U.S. Department of the Interior

U.S. Geological Survey

SIMULATION OF STREAMFLOW AND WATER QUALITY

IN THE CHRISTINA RIVER SUBBASIN AND OVERVIEW

OF SIMULATIONS IN OTHER SUBBASINS

OF THE CHRISTINA RIVER BASIN,

PENNSYLVANIA, MARYLAND, AND DELAWARE, 1994-98

by Lisa A. Senior and Edward H. Koerkle

Water-Resources Investigations Report 03-4193

In cooperation with the

DELAWARE RIVER BASIN COMMISSION,

DELAWARE DEPARTMENT OF NATURAL RESOURCES AND ENVIRONMENTAL

CONTROL, and the

PENNSYLVANIA DEPARTMENT OF ENVIRONMENTAL PROTECTION

New Cumberland, Pennsylvania

2003
ii

U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

Any use of trade, product, or firm names in this report is for identification purposes only and does not imply

endorsement by the U.S. Geological Survey.

For additional information Copies of this report may be

write to: purchased from:

District Chief U.S. Geological Survey

U.S. Geological Survey Branch of Information Services

215 Limekiln Road Box 25286, Federal Center

New Cumberland, Pennsylvania 17070 Denver, Colorado 80225-0286

Email: dc_pa@usgs.gov Telephone 1-888-ASK-USGS

Internet Address: http://pa.water.usgs.gov
Contents iii

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Purpose and scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Previous studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Description of study area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Physical setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Geology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Soils. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Hydrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Land use. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Water use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Description of model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Data for model input and calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Model-input data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Meteorologic data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Water-use data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Spatial data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Model-calibration data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Hydrologic data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Water-quality data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Simulation of streamflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Sensitivity analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Model limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Simulation of water quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Water temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Sediment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Dissolved oxygen and biochemical oxygen demand. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

Phosphorus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

Sensitivity analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

Model limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

Overview of Christina River Basin models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

Simulated sediment and nutrient yields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

Model applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

Limitations and uncertainty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

Summary and conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

References cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

Appendixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

CONTENTS

Page
iv Contents

Figure 1-3. Maps showing:

1. Location of the Christina River Basin and its four major subbasins and

nonpoint-source water-quality monitoring sites, Pennsylvania,

Delaware, and Maryland. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2. Mapped soil associations in the Christina River subbasin, Pennsylvania,

Maryland, and Delaware. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3. National Oceanic and Atmospheric Administration meteorologic

stations and calculated Thiessen polygons in the vicinity of the

Christina River subbasin, Pennsylvania, Maryland, and Delaware . . . . . . . . . 12

4-5. Graphs showing:

4. Monthly precipitation measured at the Wilmington Airport National Oceanic

and Atmospheric Administration and Porter Reservoir meteorologic

stations near the Christina River subbasin in Delaware. . . . . . . . . . . . . . . . . . . 13

5. Monthly estimates of potential evapotranspiration for Wilmington Airport,

Delaware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

6-7. Maps showing:

6. Generalized 1995 land-use map for the Christina River subbasin, Pennsylvania,

Maryland, and Delaware. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

7. Streamflow-measurement stations and water-quality monitoring sites in the

Christina River subbasin, Pennsylvania, Maryland, and Delaware . . . . . . . . . 19

8-9. Graphs showing:

8. Relation between water-quality constituents and streamflow for stormflow and

base-flow samples collected in 1998 at streamflow-measurement station

01478000, Christina River at Coochs Bridge, Del. . . . . . . . . . . . . . . . . . . . . . . . . 23

9. Relation between water-quality constituents and streamflow for stormflow

and base-flow samples collected in 1998 at streamflow-measurement

station 01480095, Little Mill Creek near Newport, Del. . . . . . . . . . . . . . . . . . . . 24

10-15. Boxplots showing:

10. Distribution of concentrations of suspended solids in samples collected under

(A) base-flow and (B) stormflow conditions at the 11 nonpoint-source

monitoring sites in the Christina River Basin during 1998 . . . . . . . . . . . . . . . . 25

11. Distribution of concentrations of dissolved nitrite plus nitrate in samples

collected under (A) base-flow and (B) stormflow conditions at the

11 nonpoint-source monitoring sites in the Christina River Basin during

1998. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

12. Distribution of concentrations of dissolved ammonia in samples collected

under (A) base-flow and (B) stormflow conditions at the 11 nonpointsource monitoring sites in the Christina River Basin during 1998 . . . . . . . . . . 27

13. Distribution of concentrations of total ammonia in samples collected under

(A) base-flow and (B) stormflow conditions at the 11 nonpoint-source

monitoring sites in the Christina River Basin during 1998 . . . . . . . . . . . . . . . . 28

14. Distribution of concentrations of dissolved orthophosphate in samples

collected under (A) base-flow and (B) stormflow conditions at the

11 nonpoint-source monitoring sites in the Christina River Basin during

1998. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

ILLUSTRATIONS

Page
Contents v

Figure 10-15. Boxplots showing—Continued:

15. Distribution of concentrations of total phosphorus in samples collected under

(A) base-flow and (B) stormflow conditions at the 11 nonpoint-source

monitoring sites in the Christina River Basin during 1998 . . . . . . . . . . . . . . . . 30

16. Map showing location of segments, reach drainage areas, and stream reaches

(RCHRES) delineated for Hydrological Simulation Program–Fortran (HSPF)

model of the Christina River subbasin, Pennsylvania, Maryland, and Delaware. . . 32

17-44. Graphs showing:

17. Simulated and observed daily mean streamflow at streamflow-measurement

stations 01478000, Christina River at Coochs Bridge, Del., and 01480095,

Little Mill Creek near Newport, Del., for the period October 1, 1994,

through October 29, 1998 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

18. Simulated and observed hourly mean streamflow at the nonpoint-source waterquality monitoring sites in the Christina River subbasin, 01478000,

Christina River at Coochs Bridge, Del., and 01480095, Little Mill Creek near

Newport, Del., for the sampling period January 1 through October 29,

1998. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

19. Duration curves of simulated and observed hourly mean streamflow for

Christina River at Coochs Bridge, Del., for the period October 1, 1996,

to October 29, 1998, and for Little Mill Creek near Newport, Del.,

for the period September 1, 1997, to October 29, 1998 . . . . . . . . . . . . . . . . . . . . 38

20. Cumulative difference between simulated and observed daily mean

streamflow at streamflow-measurement station 01478000, Christina River

at Coochs Bridge, Del., October 1, 1994, to October 29, 1998. . . . . . . . . . . . . . . 40

21. Simulated surface runoff, interflow, and ground-water (base-flow) monthly

flow contributions from pervious land segments (PERLNDs) at the

streamflow-measurement station 01478000, Christina River at Coochs

Bridge, Del., 1996-97. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

22. Simulated and observed daily mean water temperature at streamflowmeasurement stations 01478000, Christina River at Coochs Bridge, Del.,

and 01480095, Little Mill Creek near Newport, Del. . . . . . . . . . . . . . . . . . . . . . . 47

23. Simulated hourly mean and observed instantaneous water temperature at

streamflow-measurement station 01478000, Christina River at Coochs

Bridge, Del., October 1994–October 1998 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

24. Simulated and observed streamflow and concentrations of suspended sediment

and period of composite sample during six storms in 1998 at streamflowmeasurement station 01480095, Little Mill Creek near Newark, Del.. . . . . . . . 49

25. Simulated and observed streamflow and concentrations of suspended sediment

and period of composite sample during five storms in 1998 at streamflowmeasurement station 01478000, Christina River at Coochs Bridge, Del. . . . . . 50

26. Simulated hourly mean streamflow and suspended-sediment concentrations

and observed instantaneous streamflow and total suspended-solids

concentrations under base-flow conditions at monitoring site 01480095,

Little Mill Creek near Newport, Del., and 01478000, Christina River at

Coochs Bridge, Del., 1998 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

ILLUSTRATIONS—Continued

Page
vi Contents

Figure 17-44. Graphs showing—Continued:

27. Comparison of simulated hourly mean streamflow, suspended-sediment

concentrations and suspended-sediment loads to observed instantaneous

streamflow, total suspended-solids concentrations, and hourly mean

suspended-sediment loads at streamflow-measurement stations

(A) 01480095, Little Mill Creek near Newport, Del., and (B) 01478000,

Christina River at Coochs Bridge, Del., October 1994 - October 1998 . . . . . . . 54

28. Simulated daily mean dissolved oxygen concentrations at streamflowmeasurement stations 01480095, Little Mill Creek near Newport, Del.,

and observed instantaneous dissolved oxygen concentrations at waterquality monitoring site 106281, Little Mill Creek at Atlantic Avenue, and

simulated daily mean dissolved oxygen concentrations at streamflowmeasurement station 01478000, Christina River at Coochs Bridge, Del., and

observed instantaneous dissolved-oxygen concentrations at water-quality

monitoring site 106141, Christina River at Old Baltimore Pike,

October 1994–October 1998. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

29. Simulated hourly mean dissolved oxygen concentrations at streamflowmeasurement stations 01480095, Little Mill Creek near Newport, Del., and

observed instantaneous dissolved-oxygen concentrations at water-quality

monitoring site 106281, Little Mill Creek at Atlantic Avenue, and

simulated hourly mean dissolved-oxygen concentration at streamflowmeasurement station 01478000, Christina River at Coochs Bridge, Del., and

observed instantaneous dissolved oxygen concentrations at water-quality

monitoring site 106141, Christina River at Old Baltimore Pike,

October 1994–October 1998. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

30. Simulated hourly mean chlorophyll-a concentrations at streamflowmeasurement stations 01480095, Little Mill Creek near Newport, Del., and

observed instantaneous dissolved-oxygen concentrations at water-quality

monitoring site 106281, Little Mill Creek at Atlantic Avenue, and

simulated hourly mean chlorophyll-a concentrations at streamflowmeasurement station 01478000, Christina River at Coochs Bridge, Del., and

observed instantaneous chlorophyll-a concentrations at water-quality

monitoring site 106141, Christina River at Old Baltimore Pike,

October 1994–October 1998. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

31. Simulated hourly mean biochemical oxygen demand concentrations at

streamflow-measurement station 01480095, Little Mill Creek near

Newport, Del., and observed instantaneous 20-day biochemical oxygen

demand concentrations at water-quality monitoring site 106281, Little

Mill Creek at Atlantic Avenue, and simulated hourly mean biochemical

oxygen demand concentrations at streamflow-measurement

station 01478000, Christina River at Coochs Bridge, Del., and observed

instantaneous 20-day biochemical oxygen demand concentrations at waterquality monitoring site 106141, Christina River at Old Baltimore Pike,

October 1994–October 1998. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

32. Simulated and observed streamflow and concentrations of dissolved nitrate

and period of composite sample for one of the better simulated storms

in 1998 at each of the streamflow-measurement stations 01480095,

Little Mill Creek near Newark, Del., and 01478000, Christina River at

Coochs Bridge, Del. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

ILLUSTRATIONS—Continued

Page
Contents vii

Figure 17-44. Graphs showing—Continued:

33. Simulated and observed concentrations of (A) nitrate, (B) dissolved ammonia,

and (C) particulate ammonia during base-flow conditions in 1998 at

streamflow-measurement stations 01480095, Little Mill Creek near

Newport, Del., and 01478000, Christina River at Coochs Bridge, Del.. . . . . . . 64

34. Simulated hourly mean nitrate concentrations and loads at streamflowmeasurement stations (A) 01480095, Little Mill Creek near Newport, Del.,

and (B) 01478000, Christina River at Coochs Bridge, Del., and observed

instantaneous nitrate concentrations and loads at water-quality

monitoring sites (A) 106281, Little Mill Creek at Atlantic Avenue and

(B) 106141, Christina River at Old Baltimore Pike, October 1994–

October 1998 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

35. Simulated and observed streamflow and concentrations of dissolved

ammonia and period of composite sample for one of the better simulated

storms in 1998 at each of the streamflow-measurement stations 01480095,

Little Mill Creek near Newark, Del., and 01478000, Christina River

at Coochs Bridge, Del. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

36. Simulated and observed streamflow and concentrations of particulate

ammonia and period of composite sample for one of the better simulated

storms in 1998 at each of the streamflow-measurement stations 01480095,

Little Mill Creek near Newark, Del., and 01478000, Christina River at

Coochs Bridge, Del. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

37. Simulated hourly mean total ammonia concentrations and loads at

streamflow-measurement stations (A) 01480095, Little Mill Creek

near Newport, Del., and (B) 01478000, Christina River at Coochs Bridge,

Del., and observed instantaneous total ammonia concentrations and

loads at water-quality monitoring sites (A) 106281, Little Mill Creek at

Atlantic Avenue and (B) 106141, Christina River at Old Baltimore Pike,

October 1994–October 1998. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

38. Simulated and observed streamflow and concentrations of dissolved

orthophosphate and period of composite sample for one of the better

simulated storms in 1998 at each of the streamflow-measurement

stations 01480095, Little Mill Creek near Newark, Del., and 01478000,

Christina River at Coochs Bridge, Del. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

39. Simulated and observed streamflow and concentrations of particulate

orthophosphate and period of composite sample for one of the better

simulated storms in 1998 at each of the streamflow-measurement stations

01480095, Little Mill Creek near Newark, Del., and 01478000, Christina

River at Coochs Bridge, Del. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

40. Simulated and observed concentrations of (A) dissolved orthophosphate and

(B) particulate orthophosphate during base-flow conditions in 1998 at

streamflow-measurement stations 01480095, Little Mill Creek near

Newport, Del., and 01478000, Christina River at Coochs Bridge, Del.. . . . . . . 78

ILLUSTRATIONS—Continued

Page
viii Contents

Figure 17-44. Graphs showing—Continued:

41. Simulated hourly mean dissolved orthophosphate concentrations and loads

at streamflow-measurement stations (A) 01480095, Little Mill Creek near

Newport, Del., and (B) 01478000, Christina River at Coochs Bridge, Del.,

and observed instantaneous dissolved orthophosphate concentrations

and loads at water-quality monitoring sites (A) 106281, Little Mill Creek at

Atlantic Avenue and (B) 106141, Christina River at Old Baltimore Pike,

October 1994–October 1998. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

42. Sediment and phosphorus yields in relation to percent agricultural land use

as calculated from observed data for subbasins in the Chesapeake Bay

Watershed and as simulated by Hydrological Simulation Program–

Fortran (HSPF) model for selected subbasins in the Brandywine Creek,

White Clay Creek, Red Clay Creek, and Christina River Basins. . . . . . . . . . . . 90

43. Yields of nitrate and ammonia in relation to percent agricultural land use as

calculated from observed data for subbasins in the Chesapeake Bay

Watershed and as simulated by Hydrological Simulation Program–

Fortran (HSPF) model for selected subbasins in the Brandywine Creek,

White Clay Creek, Red Clay Creek, and Christina River Basins. . . . . . . . . . . . 91

44. Duration curves of observed daily mean streamflow for the period

October 1, 1943, to September 30, 2001, and of observed and simulated

daily mean streamflow for the period of simulation, October 1, 1994,

to October 29, 1998, at 01478000, Christina River at Coochs Bridge, Del. . . . . 93

45-48. Boxplots showing:

45. Ratio of simulated to observed streamflow, suspended-sediment loads, and

nitrate loads for sampled storms in 1998 at four main-stem sites and seven

subbasin sites in the Christina River Basin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

46. Ratio of simulated to observed dissolved ammonia, particulate ammonia,

and total ammonia loads for sampled storms in 1998 at four main-stem

sites and seven subbasin sites in the Christina River Basin . . . . . . . . . . . . . . . . 96

47. Ratio of simulated to observed dissolved orthophosphate, particulate

orthophosphate, and total orthophosphate loads for sampled storms in

1998 at four main-stem sites and seven subbasin sites in the Christina

River Basin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

48. Ratio of simulated mean hourly to observed instantaneous streamflow, nitrate,

dissolved ammonia, and dissolved orthophosphate loads for base-flow

periods in 1998 at four main-stem sites and seven subbasin sites in the

Christina River Basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

ILLUSTRATIONS—Continued

Page
Contents ix

Table 1. Nonpoint-source water-quality monitoring sites, Christina River Basin,

Pennsylvania and Delaware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2. Annual and total precipitation at meteorologic stations near the Christina River

subbasin, 1994-98. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3. Days of snowfall and snow-on-ground at the National Oceanic and

Atmospheric Administration meteorologic station at Newark University

Farm, 1994-98 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

4. Stream withdrawals and discharges of flow and ammonia and phosphorus loads

included in the Hydrological Simulation Program–Fortran (HSPF) model of the

Christina River subbasin, Pennsylvania, Maryland, and Delaware . . . . . . . . . . . . . . 16

5. Land-use categories used in the Hydrological Simulation Program–Fortran model

of the Christina River subbasin, Pennsylvania, Maryland, and Delaware. . . . . . . . . 16

6. Streamflow-measurement stations in the Christina River subbasin, Pennsylvania,

Maryland, and Delaware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

7. Water-quality monitoring sites in the nontidal Christina River subbasin during

1994-98 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

8. Constituents in nonpoint-source monitoring samples to be determined by

laboratory chemical analysis, Christina River Basin, Pennsylvania, Maryland,

and Delaware. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

9. Reach number, length, drainage area, segment number, and percent of land-use

category in drainage area for Christina River subbasin model . . . . . . . . . . . . . . . . . . 33

10. Calibration criteria and errors for Hydrological Simulation Program–Fortran (HSPF)

simulated streamflow at two streamflow-measurement stations in the

Christina River Basin for the period October 1, 1994, through August 15, 1995 . . . . 34

11. Statistics for comparison of observed and simulated hourly and daily mean

streamflow at two nonpoint-source water-quality monitoring sites

during the January - October 1998 nonpoint-source monitoring period

and at one water-quality monitoring site during the October 1994–October 1998

calibration period in the Christina River subbasin . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

12. Observed and simulated streamflow for Christina River at Coochs Bridge, Del.,

1994-98 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

13. Sensitivity analysis of modeled runoff characteristics at Christina River at

Coochs Bridge, Del., to variations in selected pervious land (PERLND)

parameters for the period October 1, 1994, to September 30, 1995 . . . . . . . . . . . . . . . 43

14. Suggested criteria to evaluate water-quality calibration for an Hydrological

Simulation Program–Fortran (HSPF) model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

TABLES

Page
x Contents

Table 15. Cumulative calibration errors in flow volume and constituent loads for selected

storms in 1998 at two nonpoint-source monitoring sites in the Christina River

subbasin, 01478000, Christina River at Coochs Bridge, Del., and 01480095,

Little Mill Creek near Newport, Del. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

16. Simulated and observed streamflow and loads of suspended sediment for storms

sampled in 1998 at the nonpoint-source monitoring sites, 01480095, Little

Mill Creek near Newport, Del., and 01478000, Christina River at Coochs Bridge,

Del.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

17. Observed annual precipitation and simulated annual sediment yields by land use

for three segments of Hydrological Simulation Program–Fortran (HSPF) model

for Christina River subbasin, 1995-97. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

18. Observed annual precipitation and simulated average annual sediment yield by

land use for pervious and impervious land areas in three segments of

Hydrological Simulation Program–Fortran (HSPF) model for Christina River

subbasin, 1995-97. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

19. Simulated and observed streamflow and loads of biochemical oxygen demand

for storms sampled in 1998 at the two nonpoint-source monitoring sites,

01480095, Little Mill Creek near Newport, Del., and 01478000, Christina River

at Coochs Bridge, Del. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

20. Simulated and observed streamflow and loads of dissolved nitrate, dissolved

ammonia, and particulate ammonia for storms sampled in 1998 at the two

nonpoint-source monitoring sites, 01480095, Little Mill Creek near Newport,

Del., and 01478000, Christina River at Coochs Bridge, Del. . . . . . . . . . . . . . . . . . . . . . 63

21. Observed annual precipitation and simulated annual nitrate yields by land use

for the three segments of the Hydrological Simulation Program–Fortran

(HSPF) model for Christina River subbasin, 1995-97. . . . . . . . . . . . . . . . . . . . . . . . . . . 71

22. Observed annual precipitation and simulated average annual nitrate yield by

land use for pervious and impervious land areas in the three segments of the

Hydrological Simulation Program–Fortran (HSPF) model for Christina River

subbasin, 1995-97. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

23. Observed annual precipitation and simulated annual total ammonia yields by

land use for the three segments of the Hydrological Simulation Program–

Fortran (HSPF) model for Christina River subbasin, 1995-97 . . . . . . . . . . . . . . . . . . . 73

24. Observed annual precipitation and simulated average annual total ammonia

yield for pervious and impervious land areas in the three segments of the

Hydrological Simulation Program–Fortran (HSPF) model for Christina River

subbasin, 1995-97. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

25. Simulated and observed streamflow and loads of dissolved and particulate

orthophosphate for storms sampled in 1998 at the nonpoint-source monitoring

sites, 01480095, Little Mill Creek near Newport, Del., and 01478000, Christina

River at Coochs Bridge, Del. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

26. Observed annual precipitation and simulated annual total (dissolved plus adsorbed)

orthophosphate yields by land use for the three segments of the Hydrological

Simulation Program–Fortran (HSPF) model for Christina River subbasin,

1995-97 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

TABLES—Continued

Page
Contents xi

Table 27. Observed annual precipitation and simulated average annual total orthophosphate

yield by land use for pervious and impervious land areas in the three segments

of the Hydrological Simulation Program–Fortran (HSPF) model for Christina

River subbasin, 1995-97 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

28. Observed annual precipitation and simulated average annual sediment yield by

land use for pervious and impervious land areas in segments of Hydrological

Simulation Program–Fortran (HSPF) model for the Brandywine Creek,

Red Clay Creek, White Clay Creek, and Christina River subbasins, 1995-97 . . . . . . 85

29. Observed annual precipitation and simulated average annual nitrate yield by

land use for pervious and impervious land areas in segments of Hydrological

Simulation Program–Fortran (HSPF) model for the Brandywine Creek,

Red Clay Creek, White Clay Creek, and Christina River subbasins, 1995-97 . . . . . . 86

30. Observed annual precipitation and simulated average annual total ammonia yield

by land use for pervious and impervious land areas in segments of Hydrological

Simulation Program–Fortran (HSPF) model for the Brandywine Creek, Red Clay

Creek, White Clay Creek, and Christina River subbasins, 1995-97 . . . . . . . . . . . . . . . 87

31. Observed annual precipitation and simulated average annual total orthophosphate

yield by land use for pervious and impervious land areas in segments of

Hydrological Simulation Program–Fortran (HSPF) model for the Brandywine

Creek, Red Clay Creek, White Clay Creek, and Christina River subbasins,

1995-97 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

32. Total simulated nonpoint-source and estimated point source loads of nitrate,

ammonia, and phosphorus for the 4-year period October 1, 1994, through

September 30, 1998, Christina River Basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

APPENDIXES

Appendix 1. Stormflow and base-flow water quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

2. Simulated stormflow and water quality for sampled storms in 1998 . . . . . . . . . . . . . . . . 109

3. User control file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

TABLES—Continued

Page
xii Contents

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 (NGVD 1929);

horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 1927).

Abbreviated water-quality units used in report:

ft/mi, foot per mile

μg/L, micrograms per liter

μm, micrometer

μS/cm, microsiemens per centimeter at 25 degrees Celsius

mg/L, milligrams per liter

Length

inch (in.) 25.4 millimeter

foot (ft) 0.3048 meter

mile (mi) 1.609 kilometer

Area

acre 4,047 square meter

acre .4047 hectare

square mile (mi2) 2.590 square kilometer

Volume

million gallons (Mgal) 3,785 cubic meter

cubic foot (ft3

) 0.02832 cubic meter

Flow rate

foot per second (ft/s) 0.3048 meter per second

cubic foot per second (ft3/s) 0.02832 cubic meter per second

million gallons per day (Mgal/d) 0.04381 cubic meter per second

inch per hour (in/h) 0.0254 meter per hour

Mass

pound, avoirdupois (lb) 0.4536 kilogram

ton, short (2,000 lb) 0.9072 megagram

pound per acre per year (lb/acre)/yr 1.123 kilogram per hectare per year

ton per acre per year (ton/acre)/yr 3.6712 metric ton per square kilometer

per year

Temperature

degree Fahrenheit (°F) °C=5/9 (°F-32) degree Celsius

CONVERSION FACTORS AND ABBREVIATIONS

Multiply By To obtain
Abstract 1

ABSTRACT

The Christina River Basin drains 565 square

miles (mi2) in Pennsylvania and Delaware and includes

the major subbasins of Brandywine Creek, Red Clay

Creek, White Clay Creek, and Christina River. The

Christina River subbasin (exclusive of the Brandywine,

Red Clay, and White Clay Creek subbasins) drains an

area of 76 mi2. Streams in the Christina River Basin are

used for recreation, drinking water supply, and support

of aquatic life. Water quality in some parts of the Christina River Basin is impaired and does not support designated uses of the stream. A multi-agency water-quality

management strategy included a modeling component

to evaluate the effects of point- and nonpoint-source

contributions of nutrients and suspended sediment on

stream water quality. To assist in nonpoint-source evaluation, four independent models, one for each of the four

main subbasins of the Christina River Basin, were

developed and calibrated using the model code Hydrological Simulation Program–Fortran (HSPF). Waterquality data for model calibration were collected in each

of the four main subbasins and in small subbasins predominantly covered by one land use following a nonpoint-source monitoring plan. Under this plan,

stormflow and base-flow samples were collected during

1998 at two sites in the Christina River subbasin and

nine sites elsewhere in the Christina River Basin.

The HSPF model for the Christina River subbasin simulates streamflow, suspended sediment, and

the nutrients, nitrogen and phosphorus. In addition, the

model simulates water temperature, dissolved oxygen,

biochemical oxygen demand, and plankton as secondary

objectives needed to support the sediment and nutrient

simulations. For the model, the basin was subdivided

into nine reaches draining areas that ranged from 3.8 to

21.9 mi2. Ten different pervious land uses and two

impervious land uses were selected for simulation.

Land-use areas were determined from 1995 land-use

data. The predominant land uses in the Christina River

subbasin are residential, urban, forested, agricultural,

and open.

The hydrologic component of the model was run

at an hourly time step and calibrated using streamflow

data from two U.S. Geological Survey (USGS) streamflow-measurement stations for the period of October 1,

1994, through October 29, 1998. Daily precipitation

data from one National Oceanic and Atmospheric

Administration (NOAA) meteorologic station and

hourly data from one NOAA meteorologic station were

used for model input. The difference between observed

and simulated streamflow volume ranged from -2.3 to

5.3 percent for a 10-month portion of the calibration

period at the two calibration sites. Annual differences

between observed and simulated streamflow generally

were greater than the overall error for the 4-year period.

For example, at Christina River at Coochs Bridge, near

the bottom of the free-flowing part of the subbasin

(drainage area of 21 mi2), annual differences between

observed and simulated streamflow ranged from -6.9 to

6.5 percent and the overall error for the 4-year period

was -1.1 percent. Calibration errors for 36 storm periods

at the three calibration sites for total volume, low-flowrecession rate, 50-percent lowest flows, 10-percent highest flows, and storm peaks were within the recommended criteria of 20 percent or less. Much of the error

in simulating storm events on an hourly time step can

be attributed to uncertainty in the rainfall data.

The water-quality component of the model was

calibrated using nonpoint-source monitoring data collected at two USGS streamflow-measurement stations

and other water-quality monitoring data. The period of

record for water-quality monitoring was variable at the

stations, with a start date ranging from October 1994 to

January 1998 and an end date of October 1998. Because

of availability, monitoring data for suspended-solids

concentrations were used as surrogates for suspendedsediment concentrations, although suspended-solids

data may underestimate suspended sediment and affect

apparent accuracy of the suspended-sediment simulaSIMULATION OF STREAMFLOW AND WATER QUALITY

IN THE CHRISTINA RIVER SUBBASIN AND OVERVIEW

OF SIMULATIONS IN OTHER SUBBASINS

OF THE CHRISTINA RIVER BASIN,

PENNSYLVANIA, MARYLAND, AND DELAWARE, 1994-98

By Lisa A. Senior and Edward H. Koerkle
2 Introduction

tion. Comparison of observed to simulated loads for up

to six storms in 1998 at the two nonpoint-source monitoring sites (Little Mill Creek near Newport and Christina River at Coochs Bridge, Del.) indicate that

simulation error is commonly as large as an order of

magnitude for suspended sediment and nutrients. The

simulation error tends to be smaller for dissolved nutrients than for particulate nutrients. Errors of 40 percent

or less for monthly or annual values indicate a fair to

good water-quality calibration according to recommended criteria; much larger errors are possible for individual events. Assessment of the water-quality

calibration under stormflow conditions is limited by the

relatively small amount of available water-quality data

in the subbasin.

Users of the Christina River subbasin HSPF

model and HSPF models for other subbasins in the

Christina River Basin should be aware of model limitations and consider the following if the model is used for

predictive purposes: streamflow-duration curves suggest the model simulates streamflow reasonably well

when measured over a broad range of conditions and

time although streamflow and the corresponding water

quality for individual storm events may not be well simulated; streamflow-duration curves for the simulation

period compare well with duration curves for the

58-year period ending in 2001 at Christina River at

Coochs Bridge, Del., and include all but the extreme

high-flow and low-flow events; and calibration for water

quality was based on limited data, with the result of

increasing uncertainty in the water-quality simulation.

INTRODUCTION

The Christina River Basin (fig. 1), which

includes Brandywine Creek (drainage area of

327 mi2), Red Clay Creek (54 mi2), White Clay

Creek (108 mi2), and the Christina River itself

(76 mi2), drains approximately 565 mi2 in southeastern Pennsylvania, northern Delaware, and a

small part of northeastern Maryland. The Christina

River and its tributaries provide drinking water for

more than 40 percent of the residents of Chester

County, Pa., and more than 50 percent of the residents of New Castle County, Del.

Stream waters of the Christina River Basin

are used for public water supply and recreation

and to support aquatic life. Some of these uses are

threatened because water quality is impaired by

point and nonpoint sources of contamination.

Causes of impairment have been identified as sediment, nutrients, and bacteria (Greig and others,

1998). In addition, some agricultural areas of the

basin are undergoing urbanization, and the effects

of land-use changes on water quality and quantity

are unknown. The states of Delaware and Pennsylvania need tools to evaluate alternative approaches

for addressing existing water-quantity and waterquality problems and for forecasting future conditions.

A 5-year water-quality management strategy

for the Christina River Basin starting in 1995 was

conceived and directed by the Delaware Department of Natural Resources and Environmental

Control (DNREC), Pennsylvania Department of

Environmental Protection (PADEP), Chester

County Conservation District (CCHD), Water

Resources Agency of New Castle County, Chester

County Water Resources Authority (CCWRA),

New Castle County Conservation District

(NCCCD), Delaware River Basin Commission

(DRBC), U.S. Environmental Protection Agency

(USEPA), watershed groups and other concerned

organizations, groups, and individuals. To assist

water-resources managers and others interested in

addressing water-quality problems, the U.S. Geological Survey (USGS) developed a nonpointsource monitoring plan and constructed a hydrologic and water-quality model of the basin to estimate sediment and nutrient contributions from

nonpoint sources. USGS conducted the Christina

River Basin nonpoint-source monitoring and modeling in cooperation with DRBC, DNREC, and

PADEP.

A widely used model, Hydrological Simulation Program–Fortran (HSPF), was selected to estimate the nonpoint-source loads of nutrients and

sediment for the Christina River Basin. Each of the

four major subbasins in the Christina River Basin

was modeled separately because HSPF can be

applied only to free-flowing, nontidal streams. The

lower reaches of the Christina River and its tributaries, Brandywine Creek, White Clay Creek, and

Red Clay Creek, are tide-affected and, therefore,

are not included in the HSPF models. The watershed model, HSPF, can be used to simulate the

delivery of nonpoint-source contaminants to mainstem streams. The model can simulate hydrologic

processes, physical transport of nonpoint-source

contaminants, and in-stream chemical reactions.

Data required for this watershed model include

concentrations of contaminants of interest over a

range of hydrologic conditions from various landuse areas that are expected to differ in contribution

of nonpoint-source contaminants and hydrologic

response.
Introduction 3

Figure 1. Location of the Christina River Basin and its four major subbasins and nonpoint-source

water-quality monitoring sites, Pennsylvania, Delaware, and Maryland.
4 Introduction

The nonpoint-source water-quality sampling

plan, executed in 1997-98, provided streamflow,

nutrient, and suspended-solids data that were

used to (1) estimate concentrations and loads of the

selected constituents from various land uses in the

Christina River Basin; and (2) calibrate an HSPF

model of each major subbasin for these selected

constituents. Nonpoint-source water-quality and

streamflow data were collected at four main-stem

sites on the lower free-flowing reaches of the

Christina River and Brandywine, White Clay, and

Red Clay Creeks and at seven subbasin sites

throughout the Christina River Basin selected principally for land-use characterization (fig. 1;

table 1). All sites were equipped for continuous

streamflow recording and automated water-quality sampling. Six sites were at existing USGS

streamflow-measurement stations (gages), one site

(01480095) was at a discontinued streamflow-measurement station recommissioned for the study,

and four new streamflow/water-quality sites

(01480878, 01480637, 014806318, 01478137) were

constructed (table 1).

The HSPF model for the largest of the subbasins, the Brandywine Creek Basin, was developed

first (Senior and Koerkle, 2003a), followed by the

White Clay Creek Basin (Senior and Koerkle,

2003b). These first two models were the basis for

models in the other two subbasins, Red Clay Creek

(Senior and Koerkle, 2003c) and the Christina

River. Model input parameters affecting suspended sediment and nutrient contributions from

selected land uses were calibrated for the Brandywine Creek model and transferred to the White

Clay Creek model, where applicable, with additional calibration in the White Clay Creek model

for mushroom-growing agricultural land use. The

model parameters affecting water quality from the

Brandywine Creek and White Clay Creek models

were then transferred to the Red Clay Creek and

Christina River models with minor adjustments to

obtain similar sediment and nutrient yields by

land use. The HSPF model may be used by waterresources managers to evaluate options for managing contaminants from nonpoint and point sources

and can provide a comprehensive method of calculating nonpoint-source loads to meet total maximum daily load (TMDL) requirements. Currently

(2003), TMDL assessments by the states of Pennsylvania and Delaware are ongoing in the Christina River Basin.

Table 1. Nonpoint-source water-quality monitoring sites, Christina River Basin, Pennsylvania and Delaware

(See figure 1 for location of sites)

Type of nonpoint-source

water-quality sampling site

Site

number

on map

Location

U.S. Geological

Survey

streamflowmeasurement

station number

Drainage

area

(square

miles)

Overall basin main-stem site

White Clay Creek 1 White Clay Creek near Newark, Del. 01479000 89.1

Red Clay Creek 2 Red Clay Creek near Wooddale, Del. 01480000 47.0

Brandywine Creek 3 Brandywine Creek at Chadds Ford, Pa. 01481000 287

Christina River 4 Christina River at Coochs Bridge, Del. 01478000 20.5

Single land-use basins

Urban 5 Little Mill Creek near Newport, Del. 101480095 5.24

Residential - sewered 6 Unnamed tributary to Valley Creek at

Highway 30 at Exton, Pa.

2

01480878 1.47

Residential - unsewered (on septic systems) 7 Little Broad Run near Marshallton, Pa. 201480637 .6

Agricultural - row crop 8 Doe Run above tributary at Springdell, Pa. 2014806318 11.7

Agricultural - livestock 9 West Branch Brandywine Creek near Honey

Brook, Pa.

01480300 18.7

Agricultural - mushroom 10 Trout Run at Avondale, Pa. 201478137 1.31

Forested 11 Marsh Creek near Glenmoore, Pa. 01480675 8.57

1 Streamflow-measurement station restarted for study.

2 New streamflow-measurement station constructed for study.
Description of Study Area 5

Purpose and Scope

This report describes the development of an

HSPF model constructed for the Christina River

subbasin of the Christina River Basin and subsequent hydrologic and water-quality simulations.

The main objective of modeling was to create a tool

for water-resources managers to estimate nonpoint-source loads of selected constituents over a

range of hydrologic conditions. The model description includes explanation of the general aspects,

model structure, spatial segmentation, parameterization, and limitations. In addition, data used for

model-input and calibration are described. The

HSPF model for the Christina River subbasin was

used to simulate streamflow, water temperature,

suspended sediment, and nutrients, including

nitrate, ammonia, and orthophosphate, on an

hourly basis for the calibration period October 1,

1994, through October 29, 1998. Additionally, the

model was used to simulate water temperature,

dissolved oxygen, biochemical oxygen demand,

and plankton as secondary objectives needed to

support the sediment and nutrient simulations.

Calibration results, analysis of the model’s sensitivity to parameter variation, and model limitations are discussed for simulations of streamflow

and water-quality constituents. An overview of the

HSPF models for the four major subbasins of the

Christina River Basin is given, including examples

of model applications and comparison of model

output for each of the four major subbasins, quantification of nonpoint-source loads from selected

areas of the Christina River Basin, and discussion

of model uncertainty.

Previous Studies

Water-quality samples have been collected

by the DNREC in the Christina River subbasin as

part of state monitoring programs at various sites

since 1974. Data on land use, water quality, and

water-management issues were compiled by Greig

and others (1998) as part of the Christina River

Basin Water-Quality Management Strategy. This

compilation documented that elevated concentrations of phosphorus were of concern for nutrient

enrichment, bacteria concentrations frequently

exceeded DNREC standards for swimming, and

levels of PCBs in fish were the basis of fish consumption advisories in the Christina River.

Acknowledgments

Water-use data were obtained with the assistance of Gerald Kauffman of the Water Resources

Agency at the University of Delaware, Robert Struble of the Brandywine Valley Association, and

Craig Thomas of the CCWRA. Water-quality data

for PADEP monitoring sites in Pennsylvania were

provided by William Goman of PADEP. Information about agricultural uses was obtained from

Daniel Greig and others at the CCCD and the

NCCCD. Overall guidance for the project was provided by the modeling technical committee of the

Christina River Basin Water-Quality Management

group, including David Pollison of DRBC, Richard

Greene and Hassan Mirsajadi of DNREC, William

Goman of PADEP, Janet Bowers of CCWRA,

Gerald Kauffman of the Water Resources Agency,

and Larry Merrill of USEPA. In addition to those

mentioned above, those who helped identify the

need for the project include Nancy Goggin and

Jennifer McDermott of DNREC, and Niki Kasi and

Russell Wagner of PADEP.

DESCRIPTION OF STUDY AREA

The Christina River subbasin drains an area

of 76 mi2 in southeastern Pennsylvania, northeastern Maryland, and northern Delaware. Most of the

subbasin is in Delaware and includes only small

parts of Pennsylvania and Maryland. The headwaters of Christina River are in Chester County, Pa.,

and Cecil County, Md., and the stream flows south

into New Castle County, Del., where it turns east

and is tributary to the Delaware River (fig. 1).

Major tributaries to the Christina River that are not

included in the Christina River subbasin area as

defined for this report are White Clay Creek and

Brandywine Creek, which flow south to the Christina River. Smaller named tributaries to the Christina River subbasin include Little Mill Creek,

which flows south, and Belltown Run and Muddy

Run, which flow north to the Christina River. The

Christina River is tidal below the dam at Smalley’s

Pond (fig. 1). The largest population centers in the

Christina River subbasin are the cities of Newark

and Wilmington, Del.

Physical Setting

The Christina River subbasin encompasses

areas in the Piedmont Physiographic Province in

southeastern Pennsylvania (Berg and others, 1989)

and northeastern Maryland and the Piedmont and

Coastal Plain Physiographic Provinces in northern
6 Description of Study Area

Delaware. The topography of the Piedmont Physiographic Province is characterized by gently rolling uplands dissected by narrow valleys, whereas

the topography of the Coastal Plain Physiographic

Province is characterized by nearly flat terrain. Elevation of the land surface in the Christina River

subbasin ranges from near sea level to about 440 ft

above sea level. Most of the basin is in the Coastal

Plain Physiographic Province, which is underlain

by unconsolidated sediments. Small parts of the

basin in the headwaters of the Christina River and

of the tributary, Little Mill Creek, are above the Fall

Line (fig. 1) in the Piedmont Physiographic Province, which is underlain by bedrock.

Climate

The Christina River subbasin has a modified

humid continental climate. Winters are mild to

moderately cold and summers are warm and

humid. Normal mean annual air temperatures at

the National Oceanic and Atmospheric Administration (NOAA) weather station near the western

part of the subbasin at Newark (fig. 1) for 1971-

2000 is 54.8°F (12.7°C) (National Oceanic and

Atmospheric Administration, 2000a). Normal

mean annual air temperatures (1971-2000) are

cooler north of the basin (51.5°F at Coatesville, Pa.)

than south of the basin (54.4°F at Wilmington, Del.)

(National Oceanic and Atmospheric Administration, 2000a; 2000b). At Newark, the normal mean

temperature (1971-2000) for January, the coldest

month, is 32.5°F (0.3°C), and normal mean temperature (1971-2000) for July, the warmest month, is

76.4°F (24.7°C). Normal mean annual precipitation

(1971-2000) at Newark is 45.35 in. Precipitation is

distributed fairly evenly throughout the year. In

southeastern Pennsylvania and northern Delaware, snowfall is mainly in December, January,

February, and March.

Geology

The northern headwater areas of the Christina River subbasin are underlain by Paleozoic and

older metamorphosed sedimentary and igneous

rocks. The metasediments include schist, quartzite,

and carbonate rocks. The Paleozoic and older rocks

have been folded, faulted, and metamorphosed

several times, resulting in a structurally complex

assemblage. The primary structural trends are eastnortheast. In the southern part of the subbasin,

below the Fall Line, these rocks are overlain by

Cretaceous and Quaternary sands, clays, and gravels of the Coastal Plain. These Coastal Plain sediments were deposited on the older bedrock,

forming beds that thicken to the southeast.

Soils

Fifteen soil associations that include 21 soil

series are found in the Christina River subbasin

(fig. 2) (Kunkle, 1963; Matthews and Lavoie, 1970).

In general, the soils have developed in place and

are derived from the underlying bedrock or unconsolidated sediments. The Chester, Glenelg, Glenville, Manor, Neshaminy, Talleyville, and

Wachtung soils series are developed on schist,

gneiss, quartzite, gabbro, and diabase. The Aldino

soil series is developed on serpentinite, and the

Delanco and Elsinboro soil series are developed on

old alluvium washed from crystalline rocks. Soils

south of the Fall Line include the Butlertown, Fallsington, Keyport, Matapeake, Mattapex, Othello,

and Sassafras soil series, which are developed on

unconsolidated Coastal Plain sediments, and

urban and tidal marsh soils.

The principal soil association is SassafrasFallsington-Matapeake, which overlies about

44 percent of the Christina River subbasin. Soils in

this association generally are gently to moderately

sloping and moderately well drained. Permeabilities of individual soil series range from less than

0.2 to 6.3 in/hr, and the Keyport, Matapeake,

Othello, Glenville, Neshaminy, Talleyville, and

Wachtung soil series have some of the lowest permeabilities in this range.

Hydrology

The metamorphosed sedimentary and igneous rocks that underlie the northern part of the

Christina River subbasin form fractured-rock aquifers. The competent bedrock is overlain by weathered rock, saprolite, and soil. The bedrock and

overlying materials are recharged by precipitation.

Ground water flows through the secondary openings (fractures) in fractured-rock aquifers and discharges locally to streams and springs. The sands,

clays, and gravels of the Coastal Plain that underlie

the southern part of the Christina River subbasin

also are recharged by precipitation. Recharge to

these sedimentary beds may discharge locally to

streams and may recharge the individual beds that

dip to the southeast. Ground water in the Coastal

Plain sands and gravels flows through primary

openings (pore spaces).
Description of Study Area 7

Figure 2. Mapped soil associations in the Christina River subbasin, Pennsylvania, Maryland, and

Delaware.
8 Description of Study Area

In a water budget for the nearby Red Clay

Creek subbasin, which is underlain by fracturedrock aquifers, about 40 percent of the annual input

of precipitation is estimated to discharge as

streamflow (Vogel and Reif, 1993). The remaining

precipitation is lost to evapotranspiration. Streamflow in the Red Clay Creek is composed of, on

average, 65 percent base flow (ground-water discharge) and 35 percent surface runoff (Vogel and

Reif, 1993) with between-year variations of

10 percent. In the Christina River subbasin, base

flow appears to represent a smaller proportion of

total streamflow than in Red Clay Creek. Using a

base-flow-separation technique (Sloto and Crouse,

1996), the median percentage of base flow relative

to total streamflow is estimated to be about

46 percent for Christina River at Coochs Bridge,

1944-2001, and 44 percent for Little Mill Creek near

Newport, 1991-94 and 1998. The differences

between the percentages of base flow for Red Clay

Creek and the Christina River subbasin may be

partly due to differences in the hydrology of areas

underlain by Piedmont fractured rocks and of

areas underlain by the Coastal Plain sediments and

partly due to differences in the amount of impervious areas in the basins. In many areas underlain by

Coastal Plain sediments, base flow is the majority

of streamflow. For example, in a water budget for a

nearby area of the Coastal Plain in southwestern

New Jersey near the Delaware River, base flow was

estimated to be about 90 percent of total streamflow (Barton and Kozinksi, 1991). The presence of

soils with low permeabilities in the Christina River

subbasin may impede infiltration and therefore

reduce ground-water recharge and consequent discharge (base flow).

Stream gradients range from about 50 ft/mi

to less than 10 ft/mi in the Christina River subbasin. The highest gradient reaches (greater than

15 ft/mi) are in the Piedmont. Streambeds in

reaches with gradients greater than about 15 ft/mi

primarily are composed of silt, sand, and gravel.

Streambeds in lower gradient reaches (less than

15 ft/mi) tend to be covered with silt and sand.

Stream gradients in the tidal portion of the Christina River are less than 5 ft/mi.

The largest hydraulic structure in the Christina River subbasin is the dam at Smalley’s Pond,

near the middle of the subbasin. Other dams in the

subbasin are on Muddy Run and Belltown Run

and form Sunset Lake and Becks Pond, respectively. The primary purposes of these structures

are impoundment. The dam at Smalley’s Pond is at

the upper limit of tidal movement in the Christina

River.

Land Use

Land use in the Christina River subbasin in

1993-95 (Greig and others, 1998) was predominantly residential, urban (including industrial and

commercial uses), and forested, with lesser

amounts of agricultural and open land. From data

compiled for this period, estimated land use in the

basin is about 25 percent residential, 22 percent

urban, 22 percent forested, 12 percent agricultural,

12 percent open, and 7 percent other.

Water Use

Water use in the Christina River subbasin

consists of withdrawals and discharges of surface

water and ground water for residential, commercial, and industrial consumptive and non-consumptive uses. Typically, water from a surfacewater intake or ground-water well is withdrawn,

used as needed, and returned to the source as

waste flow minus consumptive losses. Consumptive loss refers to water that is used and is not

returned to the hydrologic system in wastewater

flow. Waste flows return to surface waters through

wastewater treatment facilities and industrial discharges. In the less urbanized parts of the basin,

ground water is the primary water supply and is

provided by wells on individual properties. Wastewater in these non-sewered areas typically is discharged and infiltrates to ground water mainly

through septic systems on individual properties. In

and near population centers, public water suppliers use surface water as the main water source but

may augment with ground water. Wastewater in

urban areas generally is carried by sewers to treatment facilities that typically discharge to streams.

In the Christina River subbasin, there are two small

wastewater treatment facilities that discharge into

the headwaters in Maryland. Wastewater from the

Newark area is piped to the Wilmington sewagetreatment facility that discharges treated effluent to

the Delaware River.

Some of the larger public water systems

maintain complex withdrawal, distribution, and

discharge facilities that allow water redistribution

within or between basins. The two main surfacewater withdrawals in the Christina River subbasin

are from the impoundment upstream of the dam at

Smalley’s Pond.
Description of Model 9

In the Christina River Basin, impaired water

quality has been linked to water-use processes

such as wastewater treatment, industrial discharges, and septic systems (Greig and others,

1998). The effects of these processes on streamflow

and water quality in the Christina River subbasin

can vary depending on their location and volumes.

DESCRIPTION OF MODEL

The numerical model HSPF includes a set of

computer codes for algorithms used to simulate

the hydrologic response of land areas to precipitation and flow through stream channels in a basin.

The algorithms used to simulate these processes

are described in detail by Bicknell and others

(1997). The rainfall-driven simulation of streamflow includes response from pervious and impervious land areas and routing of water in the stream

channel. Pervious and impervious land areas are

assigned hydrologic-response parameters on the

basis of land use and other characteristics such as

slope. Streamflow routing is controlled by channel

characteristics of model reaches. The HSPF model

can be used to simulate free-flowing streams and

well-mixed reservoirs but cannot be used to simulate tidal streams.

The HSPF model structure requires dividing

the basin into multiple elements whose number

and size reflect the range of selected hydrologic

characteristics and the scope of available input

data. A first step in structuring the model is segmenting the basin. Segmentation often is delimited

by climatological or physical characteristics that

would determine specific hydrologic response to

precipitation. When little differences are apparent

in physical characteristics, segmentation may be

determined by the number and location of precipitation stations available for input. The basin also is

subdivided into characteristic pervious (PERLND)

and impervious (IMPLND) land-use types. Within

each segment, each PERLND and IMPLND is

assigned hydrologic-response parameters. These

parameters control the partitioning and magnitude

of hydrologic outputs in response to input precipitation. The stream channel is then partitioned into

reaches (RCHRES). A RCHRES generally is delimited by major flow inputs (tributaries, etc.), calibration locations (streamflow gages, water-quality

sites), and time-of-travel considerations. Each

RCHRES receives flow from land area draining to

that reach and from upstream RCHRES. Runoff,

interflow, and ground water from each PERLND

and IMPLND is directed to a RCHRES. Pointsource withdrawals and discharges can be specified for the RCHRES where they are located. The

overall model structure including assignment of

time-series data (meteorologic, streamflow, pointsource withdrawals and discharges), reach connections, land-area to reach relations, channel characteristics, and land-use category response

parameters are described in the user control input

(UCI) file.

The hydrologic response of PERLNDs and

IMPLNDs is handled by their respective modules.

The water budget, or predicted total runoff, for

pervious land is simulated using the section

PWATER of the PERLND module. Total runoff is

the sum of base flow (ground-water discharge to

streams), interflow, and surface runoff. The hydrologic processes modeled by PWATER include infiltration of precipitation, interception by plant

materials, evapotranspiration, surface runoff,

interflow, and ground-water flow. Precipitation

may be evaporated from, move through, and(or)

remain in storage in surface interception, surface

detention, interflow, upper soil zone, lower soil

zone, and active ground water. Predicted total runoff for impervious land is simulated using the section IWATER of the IMPLND module. The

hydrologic processes modeled by IWATER include

retention, routing, and evaporation of water from

impervious areas.

Runoff derived from snowfall, snow accumulation, and snow melt is simulated using the

module SNOW. Meteorologic data are used to

determine when precipitation is rain or snow, calculate an energy balance for the snow pack, and

determine the effect of heat fluxes on the snow

pack. The amount of precipitation that occurs as

snow in the Christina River subbasin is variable.

Some years have little to no snow; others may have

snow and snow cover for most of the winter

months. The assumption was made that simulating snow would result in a more accurate streamflow simulation. However, periods cold enough to

have substantial snowfall also are likely to suffer

from poor observed streamflow record because of

channel ice at stream-gaging locations.

The routing of water in the stream channel is

simulated by the section HYDR of the module

RCHRES. Routing is based on kinematic-wave or

storage-routing methods, where flow is assumed

to be unidirectional. HYDR calculates rates of outflow and change in storage for a free-flowing reach

or completely mixed reservoir. RCHRES inflows
10 Description of Model

include runoff from PERLND and IMPLND land

areas draining to that reach, water from upstream

RCHRES, precipitation falling directly on the

RCHRES surface area, and other discharges to the

reach. RCHRES outflows include flow to the

downstream reach, withdrawals from the reach,

and evaporation. A series of reaches are used to

represent the actual network of stream channels.

For each RCHRES, a relation between depth,

surface area, volume, and outflow (discharge) is

assigned and specified in an F-TABLE. When available, data for the F-TABLEs were derived from

stage-discharge ratings for stream-gaging stations

at RCHRES endpoints. For reaches that do not end

at a stream-gaging station, data for the F-TABLE

were generated using the computer program

XSECT. XSECT calculates depth-discharge relations for a hypothetical stream channel, assuming

a trapezoidal shape and using specified stream

length, stream slope, channel width, channel

depth, floodplain slope, Manning’s n for the

stream channel, and Manning’s n for the floodplain.

The water-quality component of HSPF simulates contributions from pervious and impervious

land areas and accounts for chemical reactions in

the stream reaches. The model includes algorithms

to describe the transport of constituents from the

land to the stream reach, chemical reactions affecting constituents in the reach, sediment exchange

between channel bed and water column, and the

temperature of runoff to and water in a reach. Contributions of constituents from land areas may

vary by land-use category in the model. Waterquality simulation requires a calibrated hydrodynamic model.

Water temperature, dissolved oxygen, and

carbon dioxide in surface runoff, interflow, and

ground-water outflows from pervious land areas

are simulated in the PWTGAS section of the

PERLND module and from impervious lands in

the IWTGAS section of the IMPLND module.

Water temperature in each reach is simulated by

the HTRCH section of the module RCHRES and

includes heat transported by PERLND and

IMPLND outflows and point-source discharges.

The main heat-transfer processes considered are

transfer by advection, where water temperature is

treated as a thermal concentration, and transfer

across the air-water interface. Heat gain and loss

by radiation also is simulated. Meteorologic data,

such as air temperature and wind speed, are used

in the simulation of stream temperature. In-stream

dissolved oxygen concentrations are simulated by

the OXRX section of the RCHRES module that

includes the processes of advection, aeration, and

consumption of oxygen by biochemical oxygen

demand.

The simulation of sediment includes transport of sediment from land areas and transport

within the stream channel. Sediment release from

pervious areas is simulated in the SEDMNT module. Sediment available for transport is generated

by detachment associated with rainfall. Detached

sediment is transported to the stream as washoff.

Scour also may be simulated for pervious areas.

Sediment release for impervious areas is simulated

in the SOLIDS module. Buildup of solids on impervious areas is transported to the stream in surface

runoff. Sediment transport in the stream channel is

simulated in the SEDTRN module. The channel

simulation includes scour and deposition of bed

material but not bank material.

The transport of nutrients from the land to

the stream is simulated in the PQUAL module for

pervious areas and IQUAL module for impervious

areas. For pervious areas, nutrients associated with

soil are transported with sediment in surface runoff. Nutrients also enter the stream in interflow

and ground-water discharge. For impervious

areas, nutrients accumulate on the surface and are

washed into the stream during storm events. Once

in the stream, the transport and chemical interactions of nutrients are simulated by the modules

NUTRX and PLANK. The NUTRX and PLANK

simulations require that the in-stream simulation

of oxygen, OXRX, is active and are interactive in

the oxygen simulation. The NUTRX module

includes physical transport and inorganic chemical

reactions affecting nutrients. The PLANK module

simulates the role of periphyton and phytoplankton in the stream and includes uptake and release

of nutrients.
Data for Model Input and Calibration 11

DATA FOR MODEL INPUT

AND CALIBRATION

HSPF requires a large amount of data to

characterize effectively the hydrologic and waterquality response of the watershed to precipitation

and other inputs (Donigian and others, 1984). Data

used in creating and defining the model structure

and parameters were derived principally from spatial analysis of basin characteristics and previously

published information. Spatial data analyzed for

model construction includes land use, land-surface

slope, and soil associations. Time-series input for

streamflow and water-quality simulation include

meteorologic, precipitation quality, water-use, and

discharge quantity and quality data. Calibration

data consisted of observed streamflow for the

hydrodynamic simulation and observed water

temperatures and laboratory analyses of grab and

composite stream samples for the water-quality

simulation.

Time-series data for model input and model

output were processed and stored in the binary

format Watershed Data Management (WDM) database. The WDM format is the standard format for

input to and output from HSPF. The computer programs ANNIE (Flynn and others, 1995), IOWDM

(Lumb and others, 1990), METCMP (Alan Lumb,

U.S. Geological Survey, and John Kittle, Aqua

Terra Consultants, written commun., 1995),

WDMUtil (U.S. Environmental Protection Agency,

1999), and GenScn (Kittle and others, 1998) were

used in the processing of WDM time-series data.

Parameter and model-structure data were processed independently of the time-series data and

are defined in the UCI, an ascii text file.

Model-Input Data

The types, resolution, and quantity of the

data needed for input are determined by (1) the

hydrologic and water-quality processes to be

included in the model; (2) the time step selected for

simulation; (3) the length of the simulation period;

and (4) the spatial scale of interest. For example,

simulation of streamflow requires time-series

inputs of precipitation, potential evaporation,

withdrawals from streams, and discharges to

streams. Simulation of stream water quality

requires, in addition to parametric estimates of

chemical inputs from pervious and impervious

land areas, time-series inputs of water-temperature

data and constituent loads in point-source discharges. Observed water-temperature time-series

data may be supplied as input, but because only a

limited amount of recorded water-temperature

data were available for the Christina River subbasin, water temperature was simulated. The simulation of water temperature requires input of

additional meteorologic data.

The Christina River subbasin model was run

on a 1-hour time step. Time-series data available

only at time intervals greater than hourly required

disaggregation. For the simulation period of October 1, 1994, through October 1998, more than

4 years of reported or estimated hourly values

were needed for the time-series input data sets.

Meteorologic Data

Simulation of mean hourly streamflow in

HSPF required inputs of hourly precipitation and

potential evapotranspiration. Daily precipitation

data used for model input were selected from local

NOAA raingages based on Thiessen polygon

delineations and analysis of the precipitation

records. The daily precipitation data were disaggregated using METCMP into hourly data based

on hourly precipitation recorded at the NOAA

meteorologic station at the Wilmington, Del., Airport. Daily potential evapotranspiration data was

disaggregated at the time of simulation.

Thiessen polygons created for all local

NOAA meteorologic stations (raingages) overlaid

the Christina River subbasin in three areas (fig. 3).

Newark University Farm raingage polygon

covered about 65 percent of the western subbasin;

Wilmington Airport raingage polygon covered

about 20 percent of the southern subbasin; and

Porter Reservoir raingage polygon covered about

15 percent of the eastern subbasin. Precipitation for

these raingages is listed in table 2.

The 1994-98 period of simulation spanned

relatively normal, dry, and wet years of precipitation. For example, the long-term (1971-2000) “normal” annual precipitation as calculated from

monthly precipitation at Newark University Farm

meteorologic station is 45.35 in. (National Oceanic

and Atmospheric Administration, 2000a). In comparison to the “normal” annual precipitation at

Newark, the years 1994 and 1995 and the

10-month period of 1998 were within 15 percent of

normal (table 2). The greatest departures were in

1996 when annual precipitation was 33 percent

above normal and in 1997 when annual precipitation was about 19 percent below normal.
12 Data for Model Input and Calibration

Table 2. Annual and total precipitation at meteorologic stations near the Christina River subbasin, 1994-98

Raingage

Precipitation, in inches

1971-2000

normal1 1994 1995 1996 1997 21998 Total

Newark University Farm 45.35 43.9 40.6 60.5 36.9 32.2 214.1

Porter Reservoir 349.40 57.4 45.1 68.9 38.9 37.0 247.3

Wilmington Airport 42.81 45.4 40.1 52.4 28.0 34.2 200.1

1 Data from National Oceanic and Atmospheric Administration (2000a) unless noted.

2 Precipitation for January 1 through October 29.

3 Data from the Delaware State Climatologist (2001).

Figure 3. National Oceanic and Atmospheric Administration meteorologic stations and calculated Thiessen

polygons in the vicinity of the Christina River subbasin, Pennsylvania, Maryland, and Delaware.

Brandywine Creek

Red Clay

Creek

White Clay

Creek

Christina River

76° 75°45′ 75°30′

39°45′

40°

012 MILES

0 1 2 KILOMETERS

subbasin

Hopewell-Morgantown

subbasin

subbasin

subbasin

New Holland 2 SE Honey Brook 1S

Glenmoore

Coatesville 2 W

Phoenixville 1 E

Octoraro Lake

Marcus Hook

Porter Reservoir

Wilmington Airport Newark Univ Farm

Woodstown
Data for Model Input and Calibration 13

Comparison of the period-of-simulation precipitation totals shows substantial differences

(table 2) between meteorologic stations. For the

4-year, 10-month period, Porter Reservoir reported

23 percent more precipitation than Wilmington

Airport. Wilmington Airport is 7.5 mi southwest of

and 185 ft lower in elevation than Porter Reservoir.

Although some disagreement in total precipitation

can be expected as a result of natural spatial variability and elevation differences, the difference

between Porter Reservoir and the Wilmington Airport shows a consistent recording bias throughout

the period (fig. 4). Monthly precipitation (fig. 4)

totals show even greater departure between the

Porter Reservoir and Wilmington Airport meteorologic stations; differences of 30 percent or more

were not unusual. Comparison of Porter Reservoir

and Newark University Farm data shows precipitation totals for the period to be 15.5 percent

greater at Porter Reservoir (table 2). The Newark

University Farm meteorologic station is approximately 13.5 mi west southwest of and 169 ft lower

in elevation than Porter Reservoir. As with the

Wilmington Airport meteorologic station, natural

spatial variability and an elevation difference at

Newark University Farm likely contribute to a portion of the difference in precipitation totals. Comparison of Wilmington Airport and Newark

University Farm precipitation data shows

7 percent more precipitation at Newark University

Farm. These meteorologic stations lie on an eastwest line approximately 7.5 mi apart with an elevation difference of 16 ft.

Considering their proximity, the differences

between the Porter Reservoir data and the Wilmington Airport and Newark University Farm data

are unusually large. A review of numerous raingage network studies in the eastern United States

showed that annual differences at adjacent gages

averaged 5 percent or less (Winter, 1981) and that

those differences tend to decrease over longer periods of record. In addition, the precipitation record

of other NOAA raingages surrounding the Christina basin suggests that annual totals generally

decrease from northeast to southwest across the

basin but to a lesser extent than the differences

observed between Porter Reservoir and the Wilmington and Newark University Farm stations. Elevation difference is likely the most significant

factor in explaining these differences. The Porter

Reservoir station is higher in elevation than the

other two meteorologic stations, which have minimal elevation difference and which at 74 and 90 ft

are closer to the mean basin elevation of approximately 125 ft.

J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S

1994 1995 1996 1997 1998

0

20

2

4

6

8

10

12

14

16

18

OBSERVED MONTHLY PRECIPITATION, IN INCHES

PORTER RESERVOIR

WILMINGTON AIRPORT

Figure 4. Monthly precipitation measured at the Wilmington Airport National Oceanic and Atmospheric Administration

and Porter Reservoir meteorologic stations near the Christina River subbasin in Delaware.
14 Data for Model Input and Calibration

Because of the substantial differences in precipitation totals for these raingages, adjustment

factors to the precipitation record were required in

order to complete a satisfactory water balance for

the simulation period (Donigian and others, 1984).

Moreover, in the eastern part of the Christina River

subbasin, the water balance could only be approximated by applying about 15 percent less rainfall

than was recorded at Porter Reservoir. Thus, on the

basis of the water balance issue and in consideration of the greater elevation difference between

Porter Reservoir meteorologic station and the

mean basin elevation of approximately 125 ft,

Wilmington Airport precipitation data were

selected to represent precipitation input in place of

Porter Reservoir data where the Theissen polygon

for Porter Reservoir meteorologic station overlays

the modeled area.

Precipitation data may contain a number of

errors. Measurement errors, while known in general, are not specifically known for the raingages

used in the Christina River subbasin model. These

errors may include malfunctioning equipment,

incorrect calibration, and environmental influences

(Winter, 1981). Precipitation data from NOAA raingages adjacent to the raingages selected for the

model show departures as great as 15 percent over

the simulation period whereas individual storm

events exhibit departures as much as several hundred percent. Thus, storms with substantial precipitation in one part of the basin may appear to result

in little or no streamflow response. Disaggregation

of daily precipitation values to hourly values by

applying the hourly distribution of precipitation at

the Wilmington, Del., Airport excludes the spatial

and temporal variations in rainfall distribution

across the Christina River subbasin. Disaggregation errors can appear as timing shifts in storm

hydrographs.

Potential evapotranspiration at the Wilmington, Del., Airport meteorologic station was used

for model input. The daily estimates of potential

evapotranspiration for Wilmington were calculated by the Northeast Regional Climate Center

using a method described by DeGaetano and others (1994). This method has its basis in the British

Meteorological Office Rainfall and Evaporation

Calculation System (MORECS) and uses the Penman-Monteith equation for estimating evapotranspiration. Monthly totals of potential evapotranspiration are shown in figure 5. Disaggregation of

daily potential evapotranspiration was done automatically by HSPF. Daily potential evapotranspiration totals were divided into 24 equal hourly

values during an HSPF run.

Snow simulation requires precipitation, air

temperature, solar radiation, dewpoint, and wind

speed data. Hourly air temperature, solar radiation, dewpoint, and wind speed from Wilmington,

Del., Airport were compiled and used as input to

the model. Snow accumulation and melt are influenced directly by air temperature. In HSPF, snow

melt also is controlled by solar radiation, dewpoint, and wind speed. Wind speed is the most

variable of these three inputs and is a first-order

factor in the calculation of evaporative heat loss

from a snowpack and of heat gain through the condensation of warm humid air.

Observed snowfall at the Newark NOAA

station was used to assess the need for using the

SNOW simulation module and for calibration of

the SNOW parameters. Total snow accumulation

for the simulation period was just over 41 in. at

Figure 5. Monthly estimates of potential evapotranspiration for Wilmington Airport, Delaware.
Data for Model Input and Calibration 15

Newark. Given an average water equivalent estimate of 8 in. of snow to 1 in. of rain, snowfall

accounted for about 5 in. or 3 percent of total rainfall at Newark for the simulation period. Snow

accumulation was greatest in the year 1996 and

accounted for three quarters of the snowfall at

Wilmington Airport. The days of snowfall and

days that snow covered the ground at the Newark

gage for the years 1994-98 are listed in table 3. The

longest periods of snow cover were 17 days in February 1996 and 11 days in February 1995. In 1997,

snow cover lasted at most 3 days.

Simulation of stream water temperature

requires air temperature, dewpoint, wind speed,

cloud cover, and solar radiation. Hourly air temperature, dewpoint, windspeed, and cloud cover

from the Wilmington, Del., Airport were used as

input to the model. In the northern parts of the

basin, air temperatures for input to the model were

derived from data at the Coatesville 2 W NOAA

meteorologic station. Minimum and maximum

daily air temperatures for the Coatesville 2 W station were disaggregated to hourly air temperature

with METCMP, using the Wilmington Airport

hourly data. Hourly estimates of solar radiation for

Wilmington, Del., were calculated by the Northeast

Regional Climate Center using a method described

by DeGaetano and others (1993).

Water-Use Data

Simulation of streamflow and water quality

requires information about stream withdrawals

and discharges. Water withdrawal and discharge

data were obtained from CCWRA, Water

Resources Agency at the University of Delaware,

DNREC, and the Brandywine Valley Association

who compiled water-use information from various

sources including PADEP, DNREC, and individual

water users. Many of these data were reported on a

monthly or annual basis, and in many cases, were

available for only 1, 2, or 3 years of the 1994-98

simulation period. Where at least 1 year of acceptable monthly withdrawal data were available, the

remaining years of missing information were filled

by copying data from the most recent year prior to

the missing period. Where no monthly withdrawal

data were available, missing monthly data were

filled with values equal to 75 percent of permitted

withdrawal maximums. Missing discharge data

were filled using the same method as withdrawals.

The discharges and withdrawals included in

the simulation are presented in table 4. Isolated

single-family residential discharges were not

included in the streamflow simulation. Monthlyto-hourly disaggregation of water-use data was

done by the HSPF model at the time of simulation.

Inputs from point sources include water-quality

constituent loads, discharge temperature, and rate

of discharge. Point-source discharge-quality data,

typically available as monthly or yearly values,

were disaggregated to an hourly time step by

dividing monthly or yearly values by the number

of time steps in those periods during simulation.

Spatial Data

Spatial data input to the HSPF model are

used primarily to define the structure and “fixed”

characteristics of the model. The principal structural unit of the HSPF model is the hydrologic

response unit (i.e. PERLND and IMPLND). Hydrologic-response units for the modeled basin were

determined from analysis of digital spatial data

consisting of land use, elevation, geology, soil association, and sanitary-sewer service area data. The

digital spatial data were compiled from multiple

sources by the Water Resources Agency for New

Castle County for this study (Greig and others,

1998). These data were processed with a geographic information system (GIS) and compiled for

model input. Fifteen land-use categories were

delineated in the original digital database. These

categories were simplified and reclassified into

10 pervious and 2 impervious land-use categories

that were expected to have distinct nonpointsource water-quality signatures (table 5). Impervious areas were not delineated digitally and were

Table 3. Days of snowfall and snow-on-ground

at the National Oceanic and Atmospheric Administration

meteorologic station at Newark University Farm,

1994-98

Year

Days of snow fall

(maximum in

inches1)

1 Inches of snow, not inches of water equivalent.

Days of snow on

ground

(maximum in

inches1)

Days of

greater than

2 inches1 of

snow on

ground

21994

2 October 1 through December 31.

0 (0) 0 (0.) 0

1995 4 (7.0) 19 (6.) 7

1996 8 (13.2) 30 (16) 21

1997 7 (3.0) 5 (1.5) 0

31998

3 Through October 29.

1 (trace) 1 (trace) 0
16 Data for Model Input and Calibration

Table 4. Stream withdrawals and discharges of flow and ammonia and phosphorus loads included in the

Hydrological Simulation Program–Fortran (HSPF) model of the Christina River subbasin, Pennsylvania,

Maryland, and Delaware

[Mgal/d, million gallons per day; lbs/d, pounds per day; IND, industrial; DW, drinking water supply; STP,

sewage treatment plant; SWR, stormwater; NCW, non-contact cooling water; --, not applicable or no information]

Subbasin Name Type

Flow volume

(Mgal/d)

1994-98 Average

discharge load

(lbs/d)

Capacity

or flow

limit

1994-98

Average1 Ammonia Phosphorus

Withdrawals

Main stem Marvin Hershberger IND 0.15 -- -- --

Main stem United Water Delaware DW 4.0 -- -- --

Discharges

West Branch Highlands waste-water treatment plant STP .05 0.039 0.17 0.23

West Branch Meadowview Utilities, Inc. STP .45 .33 4.19 1.48

Little Mill Creek General Motors Assembly SWR -- .24 3.07 3.76

Little Mill Creek DuPont Chestnut Run (outfalls 001 + 002) SWR -- .039 .19 .18

Main stem-tidal Ciba-Geigy Corporation NCW -- -- -- --

Main stem-tidal Boeing Corporation SWR -- -- -- --

1 Average as estimated for model input.

Table 5. Land-use categories used in the Hydrological Simulation Program–Fortran (HSPF) model of the Christina

River subbasin, Pennsylvania, Maryland, and Delaware

Land-use category for model Description of land use

Pervious land area1 residential-septic Includes all residential land not within a sewer service area

residential-sewer Includes all residential land within a sewer service area

urban Includes commercial, industrial, institutional, transportation uses

agricultural-livestock Predominantly mixed agricultural activities of dairy cows, row crop,

pasture and other livestock operations

agricultural-rowcrop Predominantly row crop cultivation (corn, soybean, alfalfa), may

include some hay or pasture

agricultural-mushroom Mushroom growing activities including compost preparation, mushroom house operations, spent compost processing

open Recreational and other open land not used for agriculture

forested Predominantly forested land

wetlands/water Wetlands and open water

undesignated Land use not defined

Impervious land area2 residential Impervious residential land

urban Impervious commercial, industrial, and other urban land

1 Pervious land area is designated as PERLND in model.

2 Impervious land area is designated as IMPLND in model.
Data for Model Input and Calibration 17

estimated as percentages of the total areas in residential and urban land uses. Areas of specific types

of agriculture also were not available in digital

form and were estimated from knowledge of the

basin and non-digital information from conservation districts. The spatial distribution of the simplified pervious land-use categories derived from the

original digital database is shown in figure 6.

Areas of undesignated land use were considered to

have characteristics of areas with open land use.

Agricultural land use was divided into three

characteristic subtypes for the model. Agriculturallivestock land use identifies relatively small acreage farms with high animals-per-acre densities,

limited pasture areas, and rowcrops. Small acreage

dairy operations typify this land-use type. Agricultural-rowcrop land use identifies farms with lower

animals-per-acre densities (typically beef cattle

and horses) and substantial pasture and crop acreage. Agricultural-mushroom land use is the third

type of agricultural land use delimited. Mushroom

growing, which involves the preparation and use

of large amounts of manure-based compost, is

more prevalent in the Red Clay Creek and White

Clay Creek subbasins than elsewhere in the Christina River Basin.

Figure 6. Generalized 1995 land-use map for the Christina River subbasin, Pennsylvania, Maryland, and Delaware

(Land-use data from Greig and others, 1998).
18 Data for Model Input and Calibration

Residential land use is distributed throughout the basin and is divided into two types:

sewered and non-sewered. Sewered residential

areas tend to have higher housing densities and

are nearer to urban/suburban areas than non-sewered area. Non-sewered residential areas tend to

have lower densities and are more rural. Urban

land use in the basin generally is concentrated in

the Coastal Plain in the vicinity of the Christina

River. Other urban land use is in small boroughs

and towns and along major roadways. Forested

land is distributed throughout the basin and tends

to be along stream channels, especially in the

southern and northern parts of the basin (fig. 6).

Model-Calibration Data

Observed streamflow and water-quality data

are needed to calibrate the hydrologic and waterquality components of the HSPF model, respectively. These data are available at streamflow-measurement stations (gages) and water-quality

monitoring sites established in the basin for this

study and for other purposes. The period of record

and frequency of observations differ among these

gages and monitoring locations. In general, fewer

water-quality data are available than streamflow

data.

Hydrologic Data

Data used for the hydrologic calibration was

collected at two USGS streamflow-measurement

stations operating in the Christina River subbasin

during the 1994-98 simulation period (table 6;

fig. 7) (James and others, 1996, 1997, 1998, 1999).

Streamflow data at all the sites were

recorded at time steps smaller than the 1-hour time

step used in the model. Because of the shorter time

steps, no disaggregation was needed for the

streamflow data. However, substantial periods of

missing data exist in the hourly streamflow record.

Relatively short periods (up to several days) of

missing data were estimated, where possible, by

interpolation or regression. During periods of relatively steady base flow, missing data were interpolated. During periods of rapidly changing flow

(generally stormflow), missing data were estimated by linear regression. A regression equation

was generated using data from the nearest

upstream or downstream streamflow-measurement station, and which bounded the period of

missing record. Long periods (up to a year or

more) of missing data exist due to discontinuous

station operation or loss of the data record. In these

instances, no attempt was made to estimate the

missing record. Periods of poor-quality data due to

freezing conditions are few. As a result, these data

were used as recorded except in the instances

where data from a nearby streamflow-measurement station were not ice affected. In these cases,

estimated daily values were pro-rated using

hourly values from the nearby station.

Water-Quality Data

Water-quality data at stream-monitoring

sites were used in model calibration. Water-quality

data for the simulation period 1994-98 were collected by DNREC and USGS as part of several

monitoring efforts in the Christina River subbasin

(fig. 7). The period of record at monitoring sites

varied from 1 to 5 or more years (table 7), and the

sampling interval varied from hourly or less for

storms to annually. The chemical analyses of samples collected as part of these monitoring efforts

varied.

Two of the monitoring programs were

designed specifically to assist in the current assessment of water quality in the Christina River Basin:

(1) monthly and bi-monthly monitoring efforts

were conducted by DNREC and PADEP from 1995

to 1998; and (2) a hydrologically based sampling

scheme for nonpoint-source monitoring was done

by USGS, PADEP, and DNREC in 1998. The

monthly and bimonthly monitoring effort included

analyses for metals, nutrients, suspended solids,

and other constituents in samples collected at three

stream sites (table 7) in the free-flowing part of the

Christina River subbasin and was done to support

Table 6. Streamflow-measurement stations in the

Christina River subbasin, Pennsylvania, Maryland, and

Delaware

U.S.

Geological

Survey

station

identification

number

Station name

Drainage

area

(square

miles)

Period of

record

01478000 Christina River at

Coochs Bridge,

Del.

20.5 4/43 - current

01480095 Little Mill Creek

near Newport,

Del.

5.24 10/90 - 9/95,

8/97-10/98
Data for Model Input and Calibration 19

an assessment of water quality during low-flow

conditions and target point-source contributions.

The hydrologically based sampling scheme

included analyses for nutrients, suspended solids,

and organic carbon at two sites in the Christina

River subbasin (table 7) and nine sites elsewhere in

the Christina River Basin (table 1) and was done to

support an assessment of these constituents under

base-flow and stormflow conditions throughout

the year and assist in the evaluation of nonpointsource contributions to the stream.

Figure 7. Streamflow-measurement stations and water-quality monitoring sites in the Christina River subbasin,

Pennsylvania, Maryland, and Delaware.

EXPLANATION

01480095

Streamflow-measurement station,

station number, and water-quality site

01478000

01480095

Smalley’s Pond

Sunset Lake

Beck’s Pond Muddy Run

Belltown Run

West Branch

Christina

River

Christina

River

Little

Mill

Creek

East Branch

39°42′30′′

39°37′30′′

106141

106141

106191

106281

Water-quality site with no streamflowmeasurement station

75°40′

39°42′30′′

75°32′30′′

75°47′30′′
20 Data for Model Input and Calibration

The nonpoint-source water-quality monitoring in 1997-98 in the Christina River Basin was

designed to provide data on the concentrations

and loads of nutrients and suspended solids seasonally under various hydrologic conditions for

the whole of each of the four subbasins and for

seven small areas predominantly covered by one

land use. Samples were collected during four baseflow periods and up to six stormflow events. Continuous data collected at the nonpoint-source monitoring sites included streamflow and water

temperature. In the Christina River subbasin, samples collected at the streamflow-measurement station, Little Mill Creek near Newport, Del.

(01480095), provided information about water

quality in a small subbasin predominantly covered

by urban land use. Samples collected at the streamflow-measurement station, Christina River at

Coochs Bridge, Del. (01478000), provided information about the water quality of a part of the Christina River subbasin covered by mixed land uses

(about 28 percent of the drainage area). Samples

collected in the six small subbasins predominantly

covered by one land use (table 7) elsewhere in the

Christina River Basin were used to provide information about the relation between land use and

water quality. The predominant land uses in the

small-basin sites include various types of residential, forested, agricultural, and urban land use. The

small-basin data were used to develop transferable

model parameters for specific land uses.

The stormflow and base-flow sampling periods were selected as representative of the range of

seasonal, hydrologic, and land-use conditions in

the basin. Timing for the six stormflow events was

as follows: two storms in mid to late winter (February 4-5 and March 8-9, 1998), one storm in early

spring after pre-planting tillage (May 2-3, 1998),

one storm in late spring/early summer after planting of crops (June 12-13, 1998), one storm in midsummer (July 8-9, 1998), and one storm in fall after

harvest (October 8-9, 1998). Sampling was delayed

because of dry conditions in the fall of 1997. In

addition, because of the mild winter of 1998, there

was no opportunity to collect samples from frozenground runoff and snowmelt events. Sampled

storms resulted from precipitation events that

ranged from about 0.4 to 3.3 in. For Brandywine

Creek at Chadds Ford, Pa., these precipitation

events resulted in peak flows with a 1-year or less

recurrence interval. Base flow was sampled in

January, April, July, and September 1998.

Table 7. Water-quality monitoring sites in the nontidal Christina River subbasin during 1994-98

[Abbreviations: --, no data; P, Pennsylvania Department of Environmental Protection; U, U.S. Geological Survey;

D, Delaware Department of Natural Resources and Environmental Control; TSS, total suspended solids]

U.S. Geological

Survey

streamflowmeasurement

station number

State

site

number

Drainage

area

(square

miles)

Location

(predominant land use)

Monitoring

agency

Period of

record

Chemical

analyses

Monthly and bi-monthly monitoring sites

-- 106191 Christina River, Delaware Rt 273 above Newark, Del. P 1995-98 Nutrients, TSS

-- 106141 Christina River, Road 26 at Old Baltimore Pike P 1995-98 Nutrients, TSS

-- 106281 Little Mill Creek at Atlantic Avenue P 1995-98 Nutrients, TSS

Base flow and stormflow nonpoint-source monitoring small and whole basin sites

01478000 -- 20.5 Christina River at Coochs Bridge, Del.

(mixed-whole basin)

U, P, D 1998 Nutrients, TSS

01480095 -- 5.24 Little Mill Creek near Newport, Del.

(urban basin)

U, P, D 1998 Nutrients, TSS
Data for Model Input and Calibration 21

Base-flow and stormflow samples collected

from January to October 1998 were analyzed for

concentrations of dissolved and total nitrogen and

phosphorus species and suspended solids (table 8).

Other constituents, such as dissolved organic carbon (DOC) and chlorophyll a, and properties, such

as chemical oxygen demand (COD) and biological

oxygen demand (BOD), also were analyzed to better understand and simulate the chemical processes involving the fate and transport of nutrients.

Chloride was measured to provide data on the

concentrations of a conservative solute. Stormflow

samples were collected by USGS and the University of Delaware. Base-flow samples were collected

by PADEP and by DNREC. The DNREC laboratory

in Dover, Del., performed all laboratory chemical

analyses. Results of laboratory analyses for all

stormflow and base-flow samples are listed in

Appendix 1.

Table 8. Constituents in nonpoint-source monitoring samples to be determined by

laboratory chemical analysis1, Christina River Basin, Pennsylvania, Maryland,

and Delaware

[mg/L, milligrams per liter; μS/cm, microsiemens per centimeter; EPA. U.S.

Environmental Protection Agency; STDMTD, Standard Methods (American Public

Health Association, 1995)]

Constituent STORET

code Method

Reporting

limit

(mg/L)

Required constituents or properties for all samples

Ammonia nitrogen, dissolved

Ammonia nitrogen, total

00608

00610

EPA 350.1 0.004

.004

Kjeldahl nitrogen, dissolved

Kjeldahl nitrogen, total

00623

00625

EPA 351.2 .05

.05

Nitrite plus nitrate nitrogen, dissolved 00631 EPA 353.2 .05

Orthophosphorus, dissolved 00671 EPA 365.1 .005

Phosphorus, dissolved

Phosphorus, total

00666

00665

EPA 365.1 .005

.005

Chloride 00940 EPA 325.2 1

Specific conductance 90095 EPA 120.1 1. μS/cm

Total suspended-solids concentration 80154 EPA 160.2 1

Biological oxygen demand (BOD20) 00308 EPA 405.1 2.4

Dissolved organic carbon 00681 EPA 415.1 1

Chlorophyll-a2

Pheophytin

70953 92 STDMTD

10200H

.001

.002

Additional constituents-Main-stem sites

Copper, dissolved

Copper, total

01040

01042

EPA 220.2 .005

.005

Lead, dissolved

Lead, total

01049

01052

EPA 239.2 .003

.003

Zinc, dissolved

Zinc, total

01090

01092

EPA 200.7 .010

.010

Chemical oxygen demand 00340 EPA 410.1,

410.2, 410.3

5.0

Total organic carbon 00680 EPA 415.1 1

1Specifications for analytical method, reporting limit, holding time, sample volume and

preservation provided by the Delaware Department of Natural Resources and Environmental

Control laboratory.

2 First storm sampling event, all grab sampling events.
22 Data for Model Input and Calibration

Two types of samples, discrete and composite, were collected by an automatic sampler during

storm events. Discrete samples, collected at fixedtime intervals during the storm event, represent

instantaneous concentrations. Composite samples

can be used to estimate loads for a storm event.

The automatic sampler was programmed prior to

each storm event to start sampling at a pre-determined change in stage and to collect one series of

fixed-interval discrete samples and another series

of flow-weighted aliquots (250 milliliters each) for

the composite sample. The fixed-interval series

consisted of up to six 2-liter samples, collected

from 1.5 to 3 hours apart. The flow-weighted series

consisted of up to 48 250-milliliter samples. The

intake for the automatic sampler was set in

midstream and stage was determined by a transducer set in the stilling well and linked to the automatic sampler. Streams were assumed to be well

mixed. The automatic sampler was programmed

to collect a sample at fixed-time intervals and after

each time that a pre-determined flow volume, calculated using an established rating between stage

and streamflow, had passed by the monitoring site.

Composite samples were obtained by mixing the

series of flow-weighted aliquots. Because the automatic sampler was programmed in advance of

storms for which the intensity and duration were

unknown, the extent of the actual storm periods

covered by samples varied.

The measured concentration of constituents

in discrete storm samples was, in general, related

to streamflow. The concentration of total suspended solids, total ammonia nitrogen plus

organic-nitrogen, and total phosphorus tended to

increase with increasing streamflow, whereas the

concentration of dissolved nitrite plus nitrate nitrogen tended to decrease with increasing streamflow

(figs. 8, 9). Concentrations of dissolved ammonia

nitrogen and dissolved orthophosphate did not

show a strong relation to streamflow.

Concentrations of suspended solids and

nutrients in stream samples varied at the Christina

River Basin nonpoint-source monitoring locations

in relation to hydrologic conditions. Base-flow concentrations primarily are controlled by groundwater discharge and stormflow concentrations by

runoff and interflow processes. The distribution of

constituent concentrations under stormflow and

base-flow conditions at the 11 nonpoint-source

monitoring sites in the Christina River Basin are

shown in figures 10-15. For all constituents, the

range of concentrations was greater in the storm

samples than in the base-flow samples, which primarily was due to the more highly variable meteorologic and hydrologic conditions affecting the

storm samples. Concentrations of total suspended

solids, total ammonia, and total phosphorus in

stream samples were greater under stormflow conditions than under base-flow conditions

(figs. 10, 13, and 15). Concentrations of dissolved

nitrate in stream samples commonly were greater

under base-flow conditions than under stormflow

conditions (fig. 11). Concentrations of dissolved

ammonia and orthophosphate were similar or, at

some sites, tended to be slightly greater under

stormflow conditions than base-flow conditions

(figs. 12 and 14).
Data for Model Input and Calibration 23

0

160

20

40

60

80

100

120

140

TOTAL SUSPENDED SOLIDS,

IN MILLIGRAMS PER LITER

0

0.25

0.05

0.10

0.15

0.20

DISSOLVED AMMONIA,

IN MILLIGRAM PER LITER AS N

0

2.0

0.5

1.0

1.5

TOTAL AMMONIA PLUS ORGANIC NITROGEN,

IN MILLIGRAMS PER LITER AS N

0

2.5

0.5

1.0

1.5

2.0

NITRITE PLUS NITRATE,

IN MILLIGRAMS PER LITER AS N

0 600 200 400

STREAMFLOW, IN CUBIC FEET PER SECOND

0

0.8

0.2

0.4

0.6

TOTAL PHOSPHORUS,

IN MILLIGRAM PER LITER AS P

0 600 200 400

STREAMFLOW, IN CUBIC FEET PER SECOND

0

0.12

0.02

0.04

0.06

0.08

0.10

ORTHOPHOSPHATE,

IN MILLIGRAM PER LITER AS P

Figure 8. Relation between water-quality constituents and streamflow for stormflow and base-flow samples

collected in 1998 at streamflow-measurement station 01478000, Christina River at Coochs Bridge, Del.
24 Data for Model Input and Calibration

0

250

50

100

150

200

TOTAL SUSPENDED SOLIDS,

IN MILLIGRAMS PER LITER

0

0.5

0.1

0.2

0.3

0.4

DISSOLVED AMMONIA,

IN MILLIGRAM PER LITER AS N

0.5

2.5

1.0

1.5

2.0

TOTAL AMMONIA PLUS ORGANIC NITROGEN,

IN MILLIGRAMS PER LITER AS N

0.4

2.0

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

NITRITE PLUS NITRATE,

IN MILLIGRAMS PER LITER AS N

0 200 50 100 150

STREAMFLOW, IN CUBIC FEET PER SECOND

0

0.5

0.1

0.2

0.3

0.4

TOTAL PHOSPHORUS,

IN MILLIGRAM PER LITER AS P

0 200 50 100 150

STREAMFLOW, IN CUBIC FEET PER SECOND

0

0.4

0.1

0.2

0.3

ORTHOPHOSPHATE,

IN MILLIGRAM PER LITER AS P

Figure 9. Relation between water-quality constituents and streamflow for stormflow and base-flow samples

collected in 1998 at streamflow-measurement station 01480095, Little Mill Creek near Newport, Del.
Data for Model Input and Calibration 25

01480675 01480095 01480878 01480637 01480300 014806318 01478137 01481000 01480000 01479000 01478000

MONITORING STATION NUMBER

0

40

5

10

15

20

25

30

35

TOTAL SUSPENDED SOLIDS,

01480675 01480095 01480878 01480637 01480300 014806318 01478137 01481000 01480000 01479000 01478000

MONITORING STATION NUMBER

0

2,000

200

400

600

800

1,000

1,200

1,400

1,600

1,800

TOTAL SUSPENDED SOLIDS,

EXPLANATION

25TH PERCENTILE

MEDIAN

75TH PERCENTILE

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

DATA VALUE LESS THAN OR EQUAL TO 1.5 TIMES THE

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

AND MORE THAN 1.5 TIMES THE

OUTLIER DATA VALUE LESS THAN OR EQUAL TO 3

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

OUTLIER DATA VALUE MORE THAN 3 TIMES THE

Figure 10. Distribution of concentrations of suspended solids in samples collected under (A) base-flow and

(B) stormflow conditions at the 11 nonpoint-source monitoring sites in the Christina River Basin during 1998. (See

table 1 for description and figure 1 for location of monitoring sites.)

Monitoring site Predominant land use

01480675 Forested

01480095 Urban

01480878 Residential - sewered

01480637 Residential - non-sewered

01480300 Agricultural - animals/crop

014806318 Agricultural - row crop

01478137 Agricultural - mushroom growing

01481000 Mixed whole basin - Brandywine

01480000 Mixed whole basin - Red Clay

01479000 Mixed whole basin - White Clay

01478000 Mixed whole basin - Christina

A. BASE FLOW

B. STORMFLOW

IN MILLIGRAMS PER LITER

IN MILLIGRAMS PER LITER
26 Data for Model Input and Calibration

01480675 01480095 01480878 01480637 01480300 014806318 01478137 01481000 01480000 01479000 01478000

MONITORING STATION NUMBER

0

8

1

2

3

4

5

6

7

NITRITE PLUS NITRATE, IN MILLIGRAMS PER LITER AS N

01480675 01480095 01480878 01480637 01480300 014806318 01478137 01481000 01480000 01479000 01478000

MONITORING STATION NUMBER

0

8

1

2

3

4

5

6

7

NITRITE PLUS NITRATE, IN MILLIGRAMS PER LITER AS N

Monitoring site Predominant land use

01480675 Forested

01480095 Urban

01480878 Residential - sewered

01480637 Residential - non-sewered

01480300 Agricultural - animals/crop

014806318 Agricultural - row crop

01478137 Agricultural - mushroom growing

01481000 Mixed whole basin - Brandywine

01480000 Mixed whole basin - Red Clay

01479000 Mixed whole basin - White Clay

01478000 Mixed whole basin - Christina

Figure 11. Distribution of concentrations of dissolved nitrite plus nitrate in samples collected under (A) baseflow and (B) stormflow conditions at the 11 nonpoint-source monitoring sites in the Christina River Basin

during 1998. (See table 1 for description and figure 1 for location of monitoring sites.)

A. BASE FLOW

B. STORMFLOW

EXPLANATION

25TH PERCENTILE

MEDIAN

75TH PERCENTILE

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

DATA VALUE LESS THAN OR EQUAL TO 1.5 TIMES THE

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

AND MORE THAN 1.5 TIMES THE

OUTLIER DATA VALUE LESS THAN OR EQUAL TO 3

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

OUTLIER DATA VALUE MORE THAN 3 TIMES THE
Data for Model Input and Calibration 27

01480675 01480095 01480878 01480637 01480300 014806318 01478137 01481000 01480000 01479000 01478000

MONITORING STATION NUMBER

0

2.0

0.5

1.0

1.5

DISSOLVED AMMONIA, IN MILLIGRAMS PER LITER AS N

01480675 01480095 01480878 01480637 01480300 014806318 01478137 01481000 01480000 01479000 01478000

MONITORING STATION NUMBER

0

2.0

0.5

1.0

1.5

DISSOLVED AMMONIA, IN MILLIGRAMS PER LITER AS N

Figure 12. Distribution of concentrations of dissolved ammonia in samples collected under (A) base-flow and

(B) stormflow conditions at the 11 nonpoint-source monitoring sites in the Christina River Basin during 1998.

(See table 1 for description and figure 1 for location of monitoring sites.)

Monitoring site Predominant land use

01480675 Forested

01480095 Urban

01480878 Residential - sewered

01480637 Residential - non-sewered

01480300 Agricultural - animals/crop

014806318 Agricultural - row crop

01478137 Agricultural - mushroom growing

01481000 Mixed whole basin - Brandywine

01480000 Mixed whole basin - Red Clay

01479000 Mixed whole basin - White Clay

01478000 Mixed whole basin - Christina

A. BASE FLOW

B. STORMFLOW

EXPLANATION

25TH PERCENTILE

MEDIAN

75TH PERCENTILE

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

DATA VALUE LESS THAN OR EQUAL TO 1.5 TIMES THE

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

AND MORE THAN 1.5 TIMES THE

OUTLIER DATA VALUE LESS THAN OR EQUAL TO 3

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

OUTLIER DATA VALUE MORE THAN 3 TIMES THE
28 Data for Model Input and Calibration

01480675 01480095 01480878 01480637 01480300 014806318 01478137 01481000 01480000 01479000 01478000

MONITORING STATION NUMBER

0

1.5

0.5

1.0

TOTAL AMMONIA, IN MILLIGRAMS PER LITER AS N

01480675 01480095 01480878 01480637 01480300 014806318 01478137 01481000 01480000 01479000 01478000

MONITORING STATION NUMBER

12

0

2

4

6

8

10

TOTAL AMMONIA, IN MILLIGRAMS PER LITER AS N

Monitoring site Predominant land use

01480675 Forested

01480095 Urban

01480878 Residential - sewered

01480637 Residential - non-sewered

01480300 Agricultural - animals/crop

014806318 Agricultural - row crop

01478137 Agricultural - mushroom growing

01481000 Mixed whole basin - Brandywine

01480000 Mixed whole basin - Red Clay

01479000 Mixed whole basin - White Clay

01478000 Mixed whole basin - Christina

Figure 13. Distribution of concentrations of total ammonia in samples collected under (A) base-flow and (B)

stormflow conditions at the 11 nonpoint-source monitoring sites in the Christina River Basin during 1998.

(See table 1 for description and figure 1 for location of monitoring sites.)

A. BASE FLOW

B. STORMFLOW

EXPLANATION

25TH PERCENTILE

MEDIAN

75TH PERCENTILE

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

DATA VALUE LESS THAN OR EQUAL TO 1.5 TIMES THE

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

AND MORE THAN 1.5 TIMES THE

OUTLIER DATA VALUE LESS THAN OR EQUAL TO 3

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

OUTLIER DATA VALUE MORE THAN 3 TIMES THE
Data for Model Input and Calibration 29

01480675 01480095 01480878 01480637 01480300 014806318 01478137 01481000 01480000 01479000 01478000

MONITORING STATION NUMBER

0

1.00

0.25

0.50

0.75

DISSOLVED ORTHOPHOSPHATE,

01480675 01480095 01480878 01480637 01480300 014806318 01478137 01481000 01480000 01479000 01478000

MONITORING STATION NUMBER

0

1.00

0.25

0.50

0.75

DISSOLVED ORTHOPHOSPHATE,

Monitoring site Predominant land use

01480675 Forested

01480095 Urban

01480878 Residential - sewered

01480637 Residential - non-sewered

01480300 Agricultural - animals/crop

014806318 Agricultural - row crop

01478137 Agricultural - mushroom growing

01481000 Mixed whole basin - Brandywine

01480000 Mixed whole basin - Red Clay

01479000 Mixed whole basin - White Clay

01478000 Mixed whole basin - Christina

Figure 14. Distribution of concentrations of dissolved orthophosphate in samples collected under (A) baseflow and (B) stormflow conditions at the 11 nonpoint-source monitoring sites in the Christina River Basin

during 1998. (See table 1 for description and figure 1 for location of monitoring sites.)

A. BASE FLOW

B. STORMFLOW

IN MILLIGRAM PER LITER AS P IN MILLIGRAM PER LITER AS P

EXPLANATION

25TH PERCENTILE

MEDIAN

75TH PERCENTILE

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

DATA VALUE LESS THAN OR EQUAL TO 1.5 TIMES THE

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

AND MORE THAN 1.5 TIMES THE

OUTLIER DATA VALUE LESS THAN OR EQUAL TO 3

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

OUTLIER DATA VALUE MORE THAN 3 TIMES THE
30 Data for Model Input and Calibration

01480675 01480095 01480878 01480637 01480300 014806318 01478137 01481000 01480000 01479000 01478000

MONITORING STATION NUMBER

0

1.50

0.25

0.50

0.75

1.00

1.25

TOTAL PHOSPHORUS, IN MILLIGRAMS PER LITER AS P

01480675 01480095 01480878 01480637 01480300 014806318 01478137 01481000 01480000 01479000 01478000

MONITORING STATION NUMBER

0

3.5

0.5

1.0

1.5

2.0

2.5

3.0

TOTAL PHOSPHORUS, IN MILLIGRAMS PER LITER AS P

Monitoring site Predominant land use

01480675 Forested

01480095 Urban

01480878 Residential - sewered

01480637 Residential - non-sewered

01480300 Agricultural - animals/crop

014806318 Agricultural - row crop

01478137 Agricultural - mushroom growing

01481000 Mixed whole basin - Brandywine

01480000 Mixed whole basin - Red Clay

01479000 Mixed whole basin - White Clay

01478000 Mixed whole basin - Christina

Figure 15. Distribution of concentrations of total phosphorus in samples collected under (A) base-flow and

(B) stormflow conditions at the 11 nonpoint-source monitoring sites in the Christina River Basin during 1998.

(See table 1 for description and figure 1 for location of monitoring sites.)

A. BASE FLOW

B. STORMFLOW

EXPLANATION

25TH PERCENTILE

MEDIAN

75TH PERCENTILE

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

DATA VALUE LESS THAN OR EQUAL TO 1.5 TIMES THE

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

AND MORE THAN 1.5 TIMES THE

OUTLIER DATA VALUE LESS THAN OR EQUAL TO 3

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

OUTLIER DATA VALUE MORE THAN 3 TIMES THE
Simulation of Streamflow 31

Throughout the Christina River Basin, differences in water quality appear to be related to land

use. Data from 1998 (Senior and Koerkle, 2003a;

Senior and Koerkle, 2003b; this report) indicate

that under stormflow conditions, concentrations of

suspended solids, nitrate, dissolved and total

ammonia, dissolved orthophosphate, and total

phosphorus generally were higher at the sites in

predominantly agricultural small subbasins than

at sites in small subbasins with predominantly residential, urban, or forested land uses, with a few

exceptions (figs. 10-15). Concentrations of dissolved nitrate and orthophosphate under baseflow conditions also commonly wefre higher at the

sites in predominantly agricultural subbasins than

at sites in subbasins with other land uses. Concentrations of suspended sediment, nitrate, and total

phosphorus under base-flow and stormflow conditions were greater at the site in the predominantly

non-sewered residential subbasin than at the sites

in the predominantly forested, sewered residential,

and urban subbasins. Although elevated ammonia

and orthophosphate can be related to the land use,

some of these constituents may be associated with

discharge from sewage treatment plants or other

point sources upstream of monitoring sites. Differences in water quality at monitoring sites on the

main stems of the Brandywine Creek, Red Clay

Creek, White Clay Creek, and Christina River

(figs. 10-15) reflect differences in the land uses and

point-source discharges in each major subbasin.

SIMULATION OF STREAMFLOW

Streamflow in the Christina River subbasin

was simulated for the period October 1994 to October 29, 1998, or just over 4 years. Donigian and others (1984) suggest a 3-year to 5-year simulation

period as optimal for HSPF because a greater variety of climatic conditions will be included.

The Christina River subbasin was divided

into three segments, numbered 5, 8, and 9, for the

model (fig. 16). Segments of the basin area were

defined primarily on the basis of spatial distribution of precipitation and soils. Within each segment, the hydrologic response of land areas was

assumed to differ principally by land use and soil

type. Segment 5 includes the area underlain by

soils developed on the crystalline rocks in the

northwestern part of the subbasin. Segment 8

includes the area underlain by soils developed on

unconsolidated sediments in the southwestern and

central part of the subbasin. Segment 9 includes

the area underlain by predominantly urban soils

developed on both crystalline rocks and unconsolidated sediments. Precipitation input for the western model area (fig. 16) is based on data from the

Newark University Farm NOAA meteorologic station and precipitation input for the central and

eastern model area is based on data from the Wilmington Airport meteorologic station (fig. 3). The

land-based hydrologic response in each segment

was characterized spatially by sub-dividing the

area into as many as 12 land-use categories consisting of 10 pervious and 2 impervious land-use types

(table 9). These simplified land-use categories represent the predominant land uses in the 565-mi2

Christina River Basin. Initial hydrologic-response

parameters were assigned to the land-use categories and were modified as needed during model

calibration. Parameters do not vary within a segment but may vary from segment to segment.

The amount of impervious land was calculated from the residential and urban pervious land

uses using factors modified from Water Resource

Agency for New Castle County values in Greig

and others (1998). Because the HSPF model simulates no infiltration in impervious areas and some

runoff from impervious areas such as roofs and

roads does infiltrate, the amount of effectively

impervious area is expected to be lower than

impervious areas estimated by land-use maps.

Thus, the amount of effectively impervious area

was reduced from the amount of impervious area

estimated from land-use maps. This type of modification has been employed in HSPF models in

other study areas (Zarriello, 1999). The proportion

of effectively impervious land was estimated as

10 percent in residential areas without sewers,

30 percent in residential areas with sewers,

50 percent for urban areas, and 10 percent for

undesignated lands in sewered areas.

Nine RCHRES were specified for the Christina River subbasin model (fig. 16) of which seven

were used in the model hydraulic simulations.

RCHRES 8 and 9 were not included in the Christina River model simulations because of tidal influences. Of the RCHRES included in the model

simulations, lengths ranged from 1.46 to 6.73 mi;

the median length was 3.20 mi. Selection of

RCHRES lengths was guided by the confluences of

major tributaries, the location of calibration points,

the location of dams and impoundments, and

major changes in land use contributing to a stream

reach. Reach lengths were measured from topographic maps. One RCHRES was in the West

Branch, one RCHRES was in the East Branch, and
32 Simulation of Streamflow

Figure 16. Location of segments, reach drainage areas, and stream reaches (RCHRES) delineated for

Hydrological Simulation Program–Fortran (HSPF) model of the Christina River subbasin, Pennsylvania, Maryland

and Delaware.

EXPLANATION

Streamflow-measurement station

and number

01478000

01478000

01480095

1

2

3

4

5

6

7

8

9

Segment 9

Segment 8

Segment 5

Segment boundary

7 Reach number

Belltown Run

Muddy Run

West Branch

East Branch

Christina

River

Smalley’s Pond

Little Mill

Creek

Reach drainage area boundary

Christina River
Simulation of Streamflow 33

seven were in the main stem and tributaries below

the confluence of the East and West Branches. The

main stem was divided into three reaches, with

lower reach boundaries at a USGS streamflowmeasurement station, Smalley’s Pond dam, and

the confluence with the Delaware River. The tributary Little Mill Creek was divided into two

reaches, with the uppermost reach terminating at a

USGS streamflow-measurement station and the

lower reach ending at the Christina River confluence. The other reaches (RCHRES 6 and 7) were for

the tributaries Muddy Run and Belltown Run, each

of which has a dam. The area draining directly to

each reach ranged from 3.84 to 21.9 mi2, with differing amounts of the various land-use categories

in each reach drainage area (table 9).

Snowfall, snow accumulation, and snow

melt were simulated throughout the Christina

River subbasin because hydrologic and meteorologic records indicated substantial snow, ice, and

sub-freezing temperatures during the winter of

1995-96. In the coldest periods, channel icing

occurred at the calibration sites. Only estimated

daily streamflows were available during icing

periods, which occurred in February 1995 (10 days)

and in January and February 1996 (12 days).

Hourly streamflow values for these periods are

considered poor and published daily streamflows

are reported as estimated.

Assumptions

The simulation of streamflow in the Christina River subbasin was done under the following

assumptions: (1) inputs of hourly precipitation

would be estimated reasonably well by disaggregated daily precipitation data; (2) the average precipitation over a given land segment would be

represented adequately by weighted data from a

single precipitation gage; and (3) a simplified set of

PERLNDs and IMPLNDs would not unduly limit a

satisfactory hydrologic calibration of the Christina

River subbasin model.

Calibration

The basin hydrology model was calibrated

using GenScn (Kittle and others, 1998), an interactive computer program for creating, analyzing,

and comparing model simulations. HSPEXP

(Lumb and others, 1994), a computer program that

assists in calibration using an expert system, and

the calibration guidelines in Donigian and others

(1984) were employed to a limited extent because

of incomplete streamflow record at the calibration

sites. The model calibration effort was directed at

the full range of observed streamflow with an

emphasis on higher streamflows, because transport of many nonpoint source constituents is greatest at high flows. Prior to calibration, initial

Table 9. Reach number, length, drainage area, segment number, and percent of land-use category in drainage area

for Christina River subbasin model

[mi, miles; mi2, square miles]

Reach

number

Reach

length

(mi)

Reach

drainage

area

(mi2)

Segment

number

Land-use category (percent of drainage area)

Residential -

septic

Residentialsewer

Urban

Agricultural -

livestock

Agricultural -

row crop

Agricultural -

mushroom

Forested

Open

Wetland.water

Undesignated

Impervious -

residential

Impervious -

urban

1 1.46 1.87 5 9.1 0 0.4 0 58.1 0 29.7 1.1 0 0.2 1.0 0.4

1 3.33 4.83 8 7.9 4.0 7.9 0 27.1 0 23.4 12.5 0 6.2 2.6 8.3

2 4.96 7.08 5 25.5 4.7 .3 0 41.1 0 21.7 .6 .1 1.0 4.8 .3

2 3.20 2.65 8 7.7 25.9 9.6 0 4.5 0 10.7 13.8 0 13.3 12.0 10.2

3 3.24 4.47 8 4.8 17.5 12.7 0 9.2 0 18.4 8.0 .2 9.0 8.0 13.5

4 4.65 5.37 9 1.5 28.1 12.8 0 1.4 0 18.3 9.2 .2 2.6 12.2 13.4

5 2.30 3.84 9 .1 20.9 17.6 0 0 0 8.7 15.2 1.1 9.3 8.9 25.6

6 6.73 8.64 8 6.0 8.8 6.6 0 15.5 0 38.4 10.6 1.1 1.8 4.5 6.8

7 2.08 6.37 8 .6 20.1 6.9 0 8.5 0 34.3 8.1 .8 4.7 8.7 7.4

81 6.21 10.7 8 .2 19.3 8.4 0 10.4 0 27.0 7.0 .5 9.3 8.3 9.2

1

9 15.09 21.9 8 .5 10.3 17.8 0 1.8 0 12.5 20.0 4.3 9.9 4.5 18.5

Total 53.25 77.7 -- 4.6 13.7 10.8 0 11.9 0 21.6 11.6 1.6 6.5 6.4 11.4

1 Reaches 8 and 9 not included in the hydraulic model simulation because the Christina River is tidally affected in these

reaches.
34 Simulation of Streamflow

estimates of the hydrologic calibration parameters

were determined. The initial values were derived

from known watershed characteristics where possible, from parameters determined for calibrated

HSPF models for the adjacent Brandywine and

White Clay Creek Basins (Senior and Koerkle,

2003a; 2003b), from the HSPFParm database (Donigian and others, 1998), and from published sources

such as Donigian and Davis (1978) and the U.S.

Environmental Protection Agency (2000b). During

calibration with GenScn, simulated streamflow is

compared to observed streamflow through statistical and graphical methods. HSPEXP also uses statistical and graphical methods but includes default

criteria for determination of a satisfactory hydrologic calibration (table 10) and lists suggestions as

to which parameter(s) needs modification. The criteria are maximum allowable differences (errors)

between observed and simulated streamflow

expressed as percent error. These criteria are not

fixed in HSPEXP and can be modified depending

on the users’ needs. Donigian and others (1984)

offer the following error criteria for calibration:

annual and monthly values less than 10 percent

difference (Very Good); 10 to 15 percent difference

(Good); 15 to 25 percent difference (Fair). Calibrated hydrologic parameter values are listed in

the user-control input (UCI) for the Christina River

subbasin model in Appendix 3.

The model was calibrated at gaged locations

along the free-flowing sections of the Christina

River main stem and Little Mill Creek tributary.

Some drainage areas of the Christina River subbasin downstream from the streamflow-measurement station 01478000, Christina River at Coochs

Bridge, Del., were simulated but not calibrated

because no streamflow data were available in some

locations and because the Christina River becomes

tidal below Smalley’s Pond. The HSPF does not

simulate routing of water in tidal reaches. The

period of calibration was October 1, 1994, to October 29, 1998.

Stormflow hydrograph calibration consisted

of comparing stormflow volume, average simulated peak flows, and recession rates of selected

storms with observed data in GenScn and HSPEXP

and visual examination of simulated and observed

stormflow hydrographs. Twenty-one storm events

were selected from the October 1, 1994, to August

15, 1995, period for analysis in HSPEXP. Storms

were selected using the following criteria as a

guide: (1) total storm precipitation will be equal

to 0.5 in. or more. The summary statistics—error in

total storm volume, error in the mean of peak

stormflows for all selected storms, and error in

total summer storm volume—were calculated for

selected stormflow periods collectively. For the

Christina River at Coochs Bridge and Little Mill

Creek sites, these statistics indicate simulation

errors less than the default HSPEXP error criteria

(table 10) except for the 50 percent lowest flows

and summer storm volume at Little Mill Creek

near Newport, Del. The statistics in table 10 for the

Little Mill Creek site show undersimulation for

total volume, high flows, and low flows. Having

simulation errors in the same direction for these

statistics simultaneously is normally indicative of

an overall water balance error. In this case, the

reporting of these statistics for a 10.5-month period

while calibrating the model for best fit over a

4-year period resulted in the apparent short-term

bias. The large summer storm volume error results

from poor simulation of one of four storm events

Table 10. Calibration criteria and errors for HSPF simulated streamflow at two streamflow-measurement

stations in the Christina River Basin for the period October 1, 1994, through August 15, 1995

Calibration criteria, in percent1

Total

volume

Low flow

recession rate

50-percent

lowest flows

10-percent

highest flows

Storm

peaks

Seasonal

volume error

Summer

storm volume

error

10.0 0.03 10.0 15.0 20.0 30.0 50.0

Calibration

site2 Calibration errors from HSPEXP, in percent

01478000 5.3 0.0 6.3 -1.0 16.7 12.2 14.2

01480095 -2.3 -.03 -16.1 -3.0 18.8 29.0 63.5

1 Default criteria for satisfactory hydrologic calibration in HSPEXP.

2 Streamflow-measurement station number.
Simulation of Streamflow 35

selected for the statistic calculation. Observed

storm volume for the July 28, 1995, storm was

610 percent greater than the simulated volume.

Note that these statistics are not indicative of the

errors for individual storm simulations.

In general, errors in individual storm simulations vary widely. The largest errors in the simulation of stormflow appear to result from

incorrectly specified precipitation. Typically, a time

discrepancy between the simulated and observed

stormflow hydrographs has no effect on the

HSPEXP error statistics except when the time shift

moves the simulated hydrograph beyond the

established storm event time boundaries. These

boundaries are set at whole day increments (for

individual storms) or seasonal periods (June, July,

August for the summer). However, a time-shifted

event can cause difficulties with water-quality calibrations; a temporal mismatch between observed

and simulated streamflows produces a corresponding mismatch between observed and simulated water quality. Use of weighting of rainfall

also has the potential to result in incorrectly specified rainfall for individual storm events. Stormflow

simulations with the least error tended to result

from storms that produced the most uniform rainfall distribution across a drainage basin. In the

HSPF model for the adjacent Brandywine Creek

Basin, errors in individual storm simulations

tended to increase with decreasing drainage area

(Senior and Koerkle, 2003a).

Time-series comparisons of simulated and

observed daily mean streamflows at the streamflow-measurement stations on Christina River at

Coochs Bridge and on Little Mill Creek near Newport, Del. (fig. 17), show good agreement except

from May 1998 through August 1998. During that

period, simulated base flows tend to be noticeably

greater than observed base flows for the Coochs

Bridge site and for the Little Mill Creek site. The

spring and summer of 1998 was an unusually dry

period with little ground-water recharge and

strong evapotranspiration (ET) demand. In this

instance, the model allocated more water to baseflow discharge rather than to satisfying (ET)

demand. This effect is more pronounced at the Little Mill Creek site where greater urban land use

reduced the effective ET demand, allowing greater

base-flow discharge. Substantial periods of missing observed hourly streamflow data (October 1,

1995, to September 30, 1996, at Christina River at

Coochs Bridge and August 20, 1995, to August 20,

1997, at Little Mill Creek near Newport) prevented

comparison of simulated and observed hourly values over the complete simulation period. For the

period of missing hourly streamflow data (October

1, 1995, to September 30, 1996), daily streamflow

data were available for Christina River at Coochs

Bridge (fig. 17).

Time-series comparisons of simulated and

observed hourly streamflow at the nonpointsource water-quality monitoring sites, Christina

River at Coochs Bridge, Del., and Little Mill Creek

near Newport, Del., are shown in figure 18 for the

sampling period January 1 through October 29,

1998. Simulated low-flow conditions exceeded

observed streamflow in the summer months of

1998 at both sites, with the greatest departure at

the Little Mill Creek site. Summer storms also are

oversimulated with the greatest oversimulation at

the Little Mill Creek site. The more pronounced

oversimulation of summer storms at the Little Mill

Creek site is most likely due to underestimation of

the effective impervious land area in the basin.

Excess simulated base flow would also occur if

effective impervious land area was too small.

Flow-duration curves of simulated and

observed hourly streamflow for a limited portion

of the simulation period show generally good

agreement. The largest departures occur during

peak stormflows at Christina River at Coochs

Bridge, Del., and low flows at Little Mill Creek at

Newport, Del. (fig. 19). These curves represent the

longest period of continuous observed hourly

streamflow data available for each site. This period

includes 25 months of data for the Coochs Bridge

site and 14 months of data for the Newport site.

Oversimulation of peak stormflow at the

Coochs Bridge site resulted primarily for streamflows above 1,500 ft3/s, which occurred no more

than 0.1 percent of the time in the 25-month

period. The oversimulation of low flows at the

Newport site is prominent up to about 5 ft3/s,

which represents about 70 percent of the time in

the 14-month period.
36 Simulation of Streamflow 1 2,00025102050 100 200 500 1,000

DAILY MEAN STREAMFLOW,

IN CUBIC FEET PER SECOND

01478000, CHRISTINA RIVER AT COOCH

O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A 

1994 1995 1996 1997 

0.2

500

0.5

125

102050

100200

DAILY MEAN STREAMFLOW,

IN CUBIC FEET PER SECOND

01480095, LITTLE MILL CREEK NEAR 

SIMULATED

OBSERVED

Figure 17. Simulated and observed daily mean streamflow at streamflow-measurement stations 01478000 Christina River at Cooc

and 01480095 Little Mill Creek near Newport, Del. (bottom), for the period October 1, 1994, through October 29, 1998.

No record

OBSERVED SIMULATED
Simulation of Streamflow 37

1

10,000

2

5

10

20

50

100

200

500

1,000

2,000

5,000

HOURLY MEAN STREAMFLOW,

IN CUBIC FEET PER SECOND

01478000, CHRISTINA RIVER AT COOCHS BRIDGE, DEL.

J F M A M J J A S O

1998

0.2

2,000

0.5

1

2

5

10

20

50

100

200

500

1,000

HOURLY MEAN STREAMFLOW,

IN CUBIC FEET PER SECOND

01480095, LITTLE MILL CREEK NEAR NEWPORT, DEL.

SIMULATED

OBSERVED

Figure 18. Simulated and observed hourly mean streamflow at the nonpoint-source water-quality

monitoring sites in the Christina River subbasin, 01478000 Christina River at Coochs Bridge, Del.

(top), and 01480095 Little Mill Creek near Newport, Del. (bottom), for the sampling period January 1

through October 29, 1998.
38 Simulation of Streamflow

0.01 0.1 1 2 5 10 20 30 40 50 60 70 80 90 95 98 99 99.9 99.99

1

10,000

2

5

10

20

50

100

200

500

1,000

2,000

5,000

HOURLY MEAN STREAMFLOW,

IN CUBIC FEET PER SECOND

01478000, CHRISTINA RIVER AT COOCHS BRIDGE, DEL.

0.01 0.1 1 2 5 10 20 30 40 50 60 70 80 90 95 98 99 99.9 99.99

PERCENT OF THE TIME STREAMFLOW EQUALED OR EXCEEDED

0.1

1,000

0.2

0.5

1

2

5

10

20

50

100

200

500

HOURLY MEAN STREAMFLOW,

IN CUBIC FEET PER SECOND

01480095, LITTLE MILL CREEK NEAR NEWPORT, DEL.

SIMULATED

OBSERVED

Figure 19. Duration curves of simulated and observed hourly mean streamflow for Christina River at

Coochs Bridge, Del., for the period October 1, 1996, to October 29, 1998 (top), and for Little Mill Creek

near Newport, Del. (bottom), for the period September 1, 1997, to October 29, 1998.
Simulation of Streamflow 39

The model performance in simulating

hourly and daily streamflow was evaluated at the

two nonpoint-source water-quality monitoring

sites for 1998, the year of stormflow and base-flow

water-quality data collection, and at one site for

the calibration period of 1994-98. Statistical measures of the hourly and daily streamflow comparison are listed in table 11. Correlation and model-fit

efficiency coefficients for Christina River at Coochs

Bridge site are lower than those for the Little Mill

Creek near Newport site. Unlike the flow-duration

comparisons, the statistics for one-to-one comparison of observed and simulated values (table 11) are

affected by errors in the timing of storms. Because

errors in the timing of precipitation and consequent storms commonly occur in shifts on the scale

of hours, not days, they result in lower values of

correlation and model-fit efficiency coefficients for

hourly streamflow compared to those for daily

streamflow (table 11). Errors in timing of precipitation on the scale of hours affect simulated stormflow in small drainage areas to a greater extent

than simulated stormflow in large drainage areas

because the time to peak for storms generally

increases with basin size. The evaluation indicates

that the model fit efficiency and correlation coefficients for Christina River at Coochs Bridge are similar and generally slightly better for the calibration

period of 1994-98 than for 1998. Model-fit efficiency coefficients greater than 0.97 indicate an

excellent calibration (Martin and others, 2000;

James and Burgess, 1982). Simulated and observed

streamflow statistics, in inches, for Christina River

at Coochs Bridge, Del., are listed by year and for

the entire 4-year period of simulation in table 12.

Table 11. Statistics for comparison of observed and simulated hourly and daily mean streamflow at the two nonpointsource water-quality monitoring sites (01480095 Little Mill Creek near Newport and 01478000 Christina River at

Coochs Bridge), during the January - October 1998 nonpoint-source monitoring period and at one water-quality

monitoring site (01478000 Christina River at Coochs Bridge), during the October 1994 - October 1998 calibration

period in the Christina River subbasin

Site

Streamflow, in cubic feet per second

Type of

mean

values

Number of

values

Mean

observed

Mean

simulated

Mean

error

Mean

absolute

error1

Correlation

coefficient

Model-fit

efficiency2

Nonpoint-source monitoring period, January - October 1998

Little Mill Creek near Newport hourly 7,248 7.70 7.94 -0.243 2.983 0.84 0.71

Little Mill Creek near Newport daily 302 7.70 7.94 -.243 2.107 .95 .89

Christina River at Coochs Bridge hourly 7,248 26.74 26.28 .462 11.717 .77 .52

Christina River at Coochs Bridge daily 302 26.74 26.28 .462 8.769 .90 .73

Calibration period, October 1994 - October 1998

Christina River at Coochs Bridge daily 1,490 29.60 29.29 .310 8.154 .93 .85

1 Mean absolute error = sum[|(simulated - observed)|/number of values].

2 From Nash and Sutcliffe (1970) described in Wicklein and Schiffer (2002).

where

E is model-fit efficiency,

Qoi is the observed streamflow for time interval i,

Qo is the observed average streamflow for the time interval,

Qsi is the simulated streamflow for time interval i, and

N is the number of time intervals in the comparison period.

E = ( ) Qoi Qo – 2

i = 1

N

∑ ( ) Qoi Qsi – 2

i = 1

N

– ∑      / ( ) Qoi Qo – 2

i = 1

N

∑     
40 Simulation of Streamflow

Errors in simulated streamflows exhibited a

seasonal and climatic dependence. A plot of cumulative difference between simulated and observed

streamflow for the Christina River at Coochs

Bridge, Del. (fig. 20), shows that, overall, simulated

streamflow agrees best with observed streamflow

during the summer and fall months. Winter and

spring periods show the greatest simulation error.

Periods of good agreement between simulated and

observed streamflow are displayed as a horizontal

line with minor y-axis (vertical) fluctuations. Periods of poor agreement appear as larger vertical

displacements. The y-axis value lists the total difference between simulated and observed streamflow volumes, in inches, from the beginning of the

simulation period to the corresponding date on the

x-axis scale. The winter of 1996-97 had the greatest

snowfall accumulation and showed the largest

change in cumulative error; simulated streamflow

totals departed about -1.5 in. in the NovemberDecember 1996 period. A part of this loss was

returned during the spring snowmelt. Cumulative

error in simulated streamflow at Coochs Bridge

remained within about +1 to -1.5 in. rainfall equivalent over the entire simulation period.

The volume of water leaving land areas

(PERLNDs) and entering an HSPF model reach can

be subdivided into surface runoff (SURO), interflow (IFWO), and active ground-water flow

(AGWO). Impervious land segments (IMPLNDs),

by definition, have only a surface runoff (SURO)

pathway. For the Christina River at Coochs Bridge,

the totals simulated for these components are

33.2 in. of surface runoff (44 percent of total flow),

12.8 in. of interflow (17 percent of total flow), and

29.6 in. of active ground-water flow (39 percent of

total runoff).

Table 12. Observed and simulated streamflow for

Christina River at Coochs Bridge, Del., 1994-98

Year

Streamflow, in inches

Percentage

difference1

Simulated Observed Simulated -

observed

2

1994 1.77 1.70 0.07 4.1

1995 14.8 13.9 .9 6.5

1996 30.8 33.1 -2.3 -6.9

1997 15.9 15.4 .5 3.2

3

1998 14.1 14.2 -.1 -0.7

Total

(1994-98)

77.4 78.3 -.9 -1.1

1 100 x (Simulated - Observed) / Observed.

2 October 1 through December 31, 1994.

3 Through October 29, 1998.

1995 1996 1997 1998

-2

2

-1

0

1

CUMULATIVE DIFFERENCE BETWEEN SIMULATED AND

OBSERVED DAILY MEAN STREAMFLOW, IN INCHES

1994

Figure 20. Cumulative difference between simulated and observed daily mean streamflow at streamflowmeasurement station 01478000, Christina River at Coochs Bridge, Del., October 1, 1994, to October 29, 1998.
Simulation of Streamflow 41

A well-calibrated HSPF model will satisfactorily simulate the proportioning of surface runoff,

interflow, and ground-water components of the

total volume of water leaving land areas and entering streams. Simulation of components of flow is

important because the transport of contaminants

in surface runoff, interflow, and ground water is

affected by the amount and rate of water leaving

the land through each process. As a check on the

simulated proportion of base flow, a fixed-interval

base-flow-separation technique (Sloto and Crouse,

1996; Pettyjohn and Henning, 1979) was applied to

the simulated and observed streamflow record for

the Coochs Bridge and Newport sites. Base-flow

percentages determined by this technique were

51.3 and 46.9 percent for HSPF simulated streamflow and 45.9 and 44.4 percent for observed

streamflow, respectively, at the Coochs Bridge and

Newport sites. The fixed-interval base-flow-separation technique does not compute interflow as a

separate component as does HSPF. Rather, interflow is divided between base flow and surface runoff in unknown proportions. The HSPF computed

ground-water component (AGWO) plus interflow

(IFWO) represented 54.7 and 47.0 percent, respectively, for the Coochs Bridge and Newport sites.

The partitioning of PERLND water among

SURO, IFWO, and AGWO affects the stream

hydrograph and, consequently, the simulation of

nonpoint-source constituent transport (Fontaine

and Jacomino, 1997). The monthly contributions

from SURO, IFWO, and AGWO for a wetter-thanaverage year (1996) and a drier-than-average year

(1997) at Coochs Bridge, Del., are presented in

figure 21. Simulated surface runoff and interflow

are greater in magnitude and represent a greater

percent of simulated total runoff in the wet year,

1996, than in the dry year, 1997, as would be

expected. In 1996 and 1997, SURO represented 14.4

and 5.7 in., respectively (47 and 36 percent, respectively), of the total runoff at Christina River at

Coochs Bridge, Del.

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

1996

0

5

1

2

3

4

VOLUME, IN INCHES OF PRECIPITATION

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

1997

0

5

1

2

3

4

SURFACE RUNOFF (SURO)

INTERFLOW (IFWO)

GROUND WATER (AGWO)

Figure 21. Simulated surface runoff, interflow, and ground-water (base-flow) monthly flow

contributions from pervious land segments (PERLNDs) at the streamflow measurement station

01478000, Christina River at Coochs Bridge, Del., 1996-97.
42 Simulation of Streamflow

Overall, the calibration of the hydrologic

component of the HSPF model for the Christina

River subbasin generally is balanced over the full

range of observed streamflows, even though more

emphasis was placed on high-flow simulation. As

calibrated, the hydrologic component of the model

nevertheless has limitations for the application of

simulating water quality under stormflow conditions. These limitations, related primarily to the

regionalization of distant point-source precipitation data, result in a larger range and magnitude of

errors for the simulated hydrologic responses to

individual storm events than for simulated streamflow at daily or longer time steps. Errors in hourly

stormflow simulation are due in part to errors in

hourly rainfall estimated by disaggregating daily

values. Because of the dependence of certain

water-quality characteristics on streamflow conditions, limitations in the hydrologic simulations will

affect water-quality simulations, particularly during stormflow conditions at sites draining relatively small areas. In the HSPF model for the

adjacent Brandywine Creek Basin, errors commonly were relatively greater at sites draining

smaller areas (less than 10 mi2) than at sites draining larger areas (more than 10 mi2) (Senior and

Koerkle, 2003a). Although the model is intended

for high-flow simulations, base-flow water-quality

data commonly constitute a large part of waterquality monitoring efforts. Therefore, users should

be aware that the oversimulation of base-flow discharge may produce inflated estimates of baseflow constituent loads.

Sensitivity Analysis

A sensitivity analysis was performed to

examine the influence of altering selected parameters on streamflow volume simulated by the Christina River subbasin HSPF model. For the analysis,

parameters were altered one at a time. To a large

extent, the relative sensitivities of the model simulation results to changes in individual parameters

are determined by the algorithm in which the

parameters are used. However, relative sensitivities also are influenced by the calibrated values of

other parameters because of various degrees of

interdependence. IMPLND and RCHRES parameters were not included in the sensitivity analysis

because they proved to have minimal influence on

streamflow volumes during the calibration process. Rather, variations in the timing of stormflow

discharges are affected most by varying IMPLND

and RCHRES parameters. The sensitivity analysis

was limited to the period from October 1, 1994, to

September 30, 1995, because HSPEXP will not calculate error statistics if data are missing. The missing 1996 water year observed mean hourly

streamflow data thus prevented a longer analysis

period.

Selected PERLND parameter values were

multiplied by a factor prior to running a simulation while holding all other parameters constant.

Typically, application of the multiplication factors

resulted in doubling or halving the initial parameter value. In some instances, such as the lower zone

evapotranspiration (LZETP) and ground-water

recession (AGWRC) parameters, limitations on the

range of allowable values prevented doubling or

halving the values. In addition, the AGWRC

parameter was only decreased because its calibrated value is close to the maximum allowable

value. The response of simulated runoff characteristics is listed in table 13.

Total runoff volumes at the Coochs Bridge

site show the greatest sensitivity to lower-zone

storage (LZSN), upper-zone storage (UZSN), and

to the active ground-water recession constant

(AGWRC). These parameters influence simulated

base flow and ET (UZSN to a lesser extent). Base

flow and ET are the largest components of the

hydrologic budget, together making up about

75 percent of the total budget.

The 10-percent highest flows are primarily

sensitive to the lower zone storage (LZSN) and

secondarily sensitive to AGWRC, infiltration

(INFILT), and UZSN. These parameters determine

the amount of water diverted from the total available for runoff. The 50-percent lowest flows are primarily sensitive to AGWRC and secondarily

sensitive to INFILT. These parameters determine

the discharge rate from and inflow to groundwater storage.

Seasonal runoff volumes are most sensitive

to the active ground-water recession constant

(AGWRC). Seasonal runoff volume refers to the

differences between summer (June, July, and

August) runoff volumes and winter (December,

January, and February) runoff volumes. Secondary

sensitivity is greatest for INFILT and LZSN.

AGWRC determines how rapidly stream base flow

diminishes over time after recharge to groundwater storage. Ground-water storage is controlled,

in part, by infiltration and water loss to lower-zone

storage and evapotranspiration. Recharge to

ground-water storage typically exhibits seasonal-
Simulation of Streamflow 43 Table 13. Sensitivity analysis of modeled runoff characteristics at Christina River at Coochs Bridge, Del. (01478000), to variations in s

(PERLND) parameters for the period October 1, 1994, to September 30, 1995 [AGWRC, active ground-water recession constant; INFILT, infiltration; LZSN, lower-zone storage; CEPSC, interception storage; UZSNSLSUR, slope of overland flow; NSUR, Manning’s n for overland flow; INTFW, interflow; IRC, interflow recession rate; LZETP, lower-zo

Parameter Multiplier Runoff errors (in percent) Total in

Total runoff volume 50-percent low flow 10-percent high flow Seasonal runoff volume Summer storm volume Average stormflow peak Total runoff Surface runoff 

Calibrated value 1 5.9 6.3 0.5 11.9 13.7 13.7 10.94 4.86 AGWRC 0.75 12 -57 17 62 -1.6 16 11.58 4.86 INFILT 2 7.5 28 -11 47 31 -4.9 11.11 4.14 INFILT 0.5 6 -18 16 24 -8.7 41 10.95 5.89 LZSN 2 -25 -26 -25 31 37 -9.1 7.74 4.07 LZSN 0.5 27 5.7 33 36 -19 47 13.11 6.03 CEPSC 2 2.8 -5.4 -.20 .50 11 14 10.62 4.86 CEPSC 0.5 7.7 13 .70 18 14 14 11.13 4.86 UZSN 2 -3.2 6.3 -15 36 30 -4.9 10.00 4.27 UZSN 0.5 12 5.1 12 5.4 .70 30 11.61 5.32 SLSUR 2 6.1 5.7 1.3 11 12 16 10.96 4.93 SLSUR 0.5 5.8 6.3 -.40 12 15 12 10.93 4.79 NSUR 2 5.6 6.9 -1.1 14 17 9.6 10.91 4.71 NSUR 0.5 6.2 5.1 2.0 10 12 18 10.97 4.99 INTFW 2 6.5 5.7 0 10 21 -.80 11.00 4.27 INTFW 0.5 5.2 6.3 2.8 14 5.7 28 10.87 5.49 IRC1 2 2 5.0 17 -8.0 26 21 14 10.85 4.86 

IRC1 0.5 5.9 5.1 3.3 11 11 16 10.94 4.86 LZETP1 2 1.25 4.3 2.6 -.8 12 15 14 10.77 4.82 LZETP1 0.75 8.5 11 2.6 11 11 16 11.21 4.93 

1 Included monthly entries. 2 For IRC & LZETP, when increasing values in UCI file reached or exceeded 1, the value was input as .99 or .9.
44 Simulation of Streamflow

ity. Stream base flow modeled with relatively high

ground-water recession rates shows or even amplifies the seasonality in ground-water storage,

whereas, base flow modeled with relatively low

ground-water recession rates suppresses seasonal

fluctuations in ground-water storage.

Summer storm volumes show primary sensitivity to LZSN and secondary sensitivity to INFILT.

LZSN generally is not considered to have much

influence over storm volumes. However, because

HSPEXP calculates storm volumes over only

whole 24-hour increments, storm volumes for

short-duration events, which are more prevalent in

the summer, will include more base flow. These

base-flow periods are affected by the LZSN parameter.

Peak stormflows were most sensitive to

LZSN, which determines the lower-zone storage.

The percentage to which the lower-zone storage is

filled directly affects the infiltration rate and, therefore, the water available for surface runoff. Peak

stormflow was next most sensitive to INFILT,

UZSN, and INTFW. INTFW diverts surface runoff

into interflow storage. In addition to these

PERLND parameters, peak stormflow also is

affected by IMPLND parameters, if sufficient

IMPLND area exists, and by RCHRES storages as

defined in the F-TABLES, which specify relations

between depth, surface area, reach volume, and

outlflow. As with storm volumes, the choice of

storms selected for inclusion into HSPEXP has a

substantial effect on the reported peak-stormflow

statistics.

Model Limitations

The final calibration of the hydrology component of the HSPF model for the Christina River

subbasin satisfies most of the recommended calibration criteria but has limitations. These limitations can be classified as either errors in the input

and calibration data or errors in the model structure. Errors in the input data may result from the

measurement, interpolation, and extrapolation of

precipitation and other climatic data, and discharge and withdrawal rates. Errors in calibration

data include those involved in the actual measurement of streamflow or in the transcription of

streamflow data. Measurement errors result from

equipment malfunction, incorrect data transcription, and other problems, including the presence of

ice in the stream channel at or near the measurement site. Specific information required to evaluate

random or transitory measurement errors is generally unavailable. Interpolation errors can occur

when data is disaggregated to smaller time steps.

Extrapolation errors can occur when spatial variations and timing in data are lost by applying localized data to large areas.

Errors resulting from extrapolation, interpolation, and disaggregation of the precipitation data

are probably the greatest limitation to achieving

the best possible model calibration and simulations. Applying point location data from four raingages to the entire 54-mi2 basin and disaggregating

daily precipitation data to hourly data values

introduces substantial errors; stormflow simulations, in particular, have errors in peak flows and

total volumes regularly exceeding 100 percent.

These errors will translate into the water-quality

calibration of the model. In addition, temporal

errors in stormflow simulations can be detrimental

to the water-quality calibration even if stormflow

peaks and volumes are well simulated. The overall

effect of these errors is an increase in the average

error as the time period of simulation is decreased.

Other climatic data such as air temperature, solar

radiation, and wind speed are subject to the same

type of errors but are less influential factors than

precipitation in the streamflow simulation.

Measurement errors in observed streamflow

are known and corrected in some instances but

unknown and roughly estimated in other instances

such as ice-affected streamflow data. In many

cases, corrections are limited to daily values and

hourly data are left uncorrected or missing. Periods of missing hourly streamflow record were

filled with estimated data for the model to calculate statistics. However, the errors associated with

this estimated data are unknown. Estimated

records are rated as poor and errors greater then

15 percent can be expected (Durlin and Schaffstall,

1999). Errors in observed streamflow data can be

expected to affect the statistics used for calibration

evaluation and, if severe, lead to incorrect selection

of parameter values.

Errors in the model structure are mainly due

to limited resolution of PERLND, IMPLND, and

RCHRES spatial characteristics and incorrectly

specified model parameters. In general, spatial

errors result from the loss of local variation in spatial characteristics. Lack of data resolution and the

need to limit the complexity of the model structure

are the primary reasons for this loss. For example,

in the Christina River subbasin model, the number
Simulation of Water Quality 45

of pervious land-use categories has been limited to

10. In actuality, more than 10 distinct land-use categories exist. Further, each of these PERLND categories is assigned individual calibration

parameters that are selected to represent a composite average for that category. In addition, the effective impervious or IMPLND values may depart

from the expected averages. For example, in predominantly urban areas such as the Little Mill

Creek Basin, the effective impervious area is probably underestimated judging from the simulated

streamflow hydrograph. Because of this spatial

averaging, the model has limited capability to

resolve responses from land uses with limited areal

extent or that differ greatly from the average.

Many HSPF parameters are not expressed in

terms of known physical behavior, making selection of parameter values somewhat ambiguous

and may lead to incorrect specification. For example, the parameter AGWRC is not defined in terms

of established ground-water hydrologic characteristics. Also, in the case of the parameter INFILT,

published soil permeability values cannot be used

directly but only as a guide. Verification of the

proper selection of parameters occurs in the calibration process but a satisfactorily calibrated

model can be produced with more than one combination of parameters.

SIMULATION OF WATER QUALITY

Suspended sediment and nutrients were

simulated for the Christina River subbasin. The

simulation included delivery of suspended sediment and nutrients from pervious and impervious

land areas to stream reaches and transport and

chemical reactions in the stream reaches. The instream simulation of nutrients requires information about stream temperature and dissolved oxygen, both of which were simulated using the

model. Stream temperature is an important variable in determining water quality because temperature affects saturation levels of dissolved oxygen

and rates of chemical reactions. Dissolved oxygen

concentrations affect the extent of chemical reactions involving nutrients, such as nitrification. In

HSPF, the simulation of water quality is based on

and is an extension of the hydrologic simulation.

The simulation of water quality was undertaken with the following assumptions: (1) landbased contributions of sediment and nutrients

could be simulated by a simplified set of land-use

categories; (2) water quality could be represented

by the condition where chemical transformation of

nutrients are simulated explicitly in the stream

channel but not in land processes; and (3) the contribution of sediment from bank erosion in the

stream channel can be estimated by sediment from

pervious land areas.

Calibration

Each land-use category is assigned parameters that affect interflow and ground-water temperature, sediment release, and nutrient contributions

from land areas. Stream reaches are assigned

parameters that affect the simulation of stream

temperature, sediment transport, bed erosion and

deposition, and chemical reactions in the stream

channel. Individual parameters were adjusted

until the simulated water quality was an acceptable match to observed water quality. The computer program GenScn (Kittle and others, 1998),

a graphical interface to HSPF, was used for the

water-quality calibration.

Suggested guidelines to evaluate sediment

and water-quality calibration, including the nutrients nitrogen and phosphorus, in the HSPF model

are given in percentage differences between

observed and simulated monthly or annual values

(table 14) (Donigian and others, 1984). Comparison

of loads, rather than instantaneous concentrations,

are considered more appropriate when evaluating

water-quality simulations of nonpoint-source constituents (Donigian and others, 1984). Comparison

of instantaneous concentrations may result in

larger apparent differences between observed and

simulated values than comparison of loads

because of the effect of even small lags (errors) in

the timing of storm events. In addition, simulation

errors usually are larger for water-quality concentrations than for streamflow.

Table 14. Suggested criteria to evaluate water-quality

calibration for an Hydrological Simulation Program–

Fortran (HSPF) model

(from Donigian and others, 1984)

[<, less than]

Constituent

Difference between

observed and simulated

monthly or annual values,

in percent

Quality of calibration Very good Good Fair

Sediment <15 15-25 25-35

Water quality (includes

nitrogen and phosphorus)

<20 20-30 30-40
46 Simulation of Water Quality

Water-quality calibration included stormflow and base-flow conditions. Because the hydrologic part of the model is integral to simulation of

water quality, only well-simulated storms would,

ideally, be used for calibration of suspended sediment and nutrients. In all cases, however, the simulated storm hydrograph does not replicate the

observed storm hydrograph well, especially with

respect to peak flows. Therefore, simulated concentrations of suspended sediment, nitrate, ammonia,

and phosphorus cannot be expected to exactly replicate observed concentrations for all storms. Calibration was considered satisfactory when the

general pattern of simulated streamflow and suspended sediment and nutrients was simulated and

when, for better simulated storms, simulated concentrations and loads of suspended sediment and

nutrients were within an order of magnitude of

observed concentrations and loads. Individual

storm errors considerably larger than the recommended criteria of 40 percent or less for monthly or

annual values for fair to good water-quality calibration may occur and have little effect on the

overall calibration (Donigian and others, 1984).

Calibrated values for water-quality parameters are

given in the UCI file for Christina River subbasin

model (Appendix 3).

Monthly and annual load data were not

available to assess calibration errors. Simulated

and observed load data for five to six storms in

1998 were used to provide estimates of calibration

accuracy. Loads were calculated from measured

discharge and constituent concentrations in flowweighted composite samples collected during

storms. However, these limited data do not provide a long-term measure of the accuracy of the

model and may include one or more poorly simulated storms or questionable laboratory analyses,

which can have a large effect on the apparent accuracy of the model. The calibration error, calculated

as (simulated-observed)/observed for the total

flow volume or constituent load for the five storms

sampled, is listed in table 15. Calibration errors for

individual storms at the nonpoint-source monitoring site are listed and discussed in more detail in

subsequent sections describing calibration of suspended sediment, nitrogen, and phosphorus. For

many, but not all, of these storm events, loads of

suspended sediment, nitrogen, and phosphorus

were undersimulated when streamflow was

undersimulated and oversimulated when streamflow was oversimulated. Dissolved constituents

were simulated better than particulate constituents.

Water Temperature

Simulated streamwater temperature was calibrated against data collected at two streamflowmeasurement stations in the Christina River subbasin where intermittent water-temperature data

were available. Continuous observed water- temperature data were available for the periods January 21, 1998, to October 29, 1998, at the Coochs

Bridge station and December 1, 1997, to October

29, 1998, at the Newport station. Intermittent

observed instantaneous water-temperature data

were available for the period October 1994 to October 1998 at the Coochs Bridge station. Comparisons of simulated and observed continuous daily

mean water temperature at the two streamflowmeasurement stations (fig. 22) show good agreement between simulated and observed water temperature over the observed range of 0 to 25°C

except for the period of September and October

1998. During this period, simulated water temperTable 15. Cumulative calibration errors in flow volume and constituent loads for selected storms in 1998 at two

nonpoint-source monitoring sites in the Christina River subbasin, 01478000, Christina River at Coochs Bridge, Del.,

and 01480095, Little Mill Creek near Newport, Del.

Site

Number

of

storms

Cumulative calibration error for selected storm simulations in 1998, in percent1

Streamflow

volume

Suspendedsediment

load

Nitrate

load

Dissolved

ammonia

load

Particulate

ammonia

load

Dissolved

orthophosphate

load

Particulate

phosphorus

load2

Little Mill Creek near

Newport, Del.

6 2 1 -38 -31 83 -51 -62

Christina River at Coochs

Bridge, Del.

5 -2 102 5 21 -67 -33 -41

1 Percentage calibration error = 100 × [(simulated-observed) / observed]. 2 One fewer storm was available for comparison because total phosphorus was not analyzed in the October 1998 storm.
Simulation of Water Quality 47

atures fluctuated considerably more than observed

water temperatures. This excessive fluctuation in

simulated water temperatures appears to be the

result of an instability in the HSPF model when

water volume in a reach approaches the lower limits. During the late summer and early fall of 1998

after prolonged lack of rainfall, simulated streamflow decreased to the point of instability. Comparison of observed instantaneous water temperatures

to simulated mean hourly water temperatures

(fig. 23) also shows generally good agreement

between simulated and observed values. Thirtynine of 43 instantaneous measurements were

within 4°C of the observed temperature. Because

water temperature affects the rate of chemical reactions and biological processes involving nutrients

in the stream, errors in the temperature simulation

will affect calibration of the nutrient simulation to

some extent.

Sediment

Calibration of suspended sediment in the

stream channel largely is done by adjusting parameters affecting soil detachment, soil washoff, and

soil scour processes for pervious land surfaces, solids build up and washoff processes for impervious

land surfaces, and sediment transport in the channel, including deposition on and scour of the channel bottom controlled by setting shear stress

regimes. Sediment in streams may be derived from

land areas, streambanks, and beds. For the calibration, no net erosion of streambeds was assumed to

occur over the simulation period and therefore the

principal sources of sediment were assumed to be

land areas and streambanks. Because the HSPF

model does not include the process of bank erosion, sediment from streambanks was estimated by

simulating scour in pervious land areas. Simulated

concentrations of suspended sediment were evaluated against total suspended-solids data collected

D J F M A M J J A S O

1997 1998

0

40

5

10

15

20

25

30

35

WATER TEMPERATURE,

IN DEGREES CELSIUS

01480095, LITTLE MILL CREEK NEAR NEWPORT, DEL.

Figure 22. Simulated and observed daily mean water temperature at streamflow-measurement stations

01478000, Christina River at Coochs Bridge, Del., and 01480095, Little Mill Creek near Newport, Del.

0

40

5

10

15

20

25

30

35

WATER TEMPERATURE,

IN DEGREES CELSIUS

OBSERVED

SIMULATED

01478000, CHRISTINA RIVER AT COOCHS BRIDGE, DEL.

JF M A M J J A S O
48 Simulation of Water Quality

by USGS in 1998 at two nonpoint-source monitoring sites, 01480095, Little Mill Creek near Newport

and 01478000, Christina River at Coochs Bridge,

and data collected monthly and bi-monthly by

DNREC from 1994-98 at sites in Delaware.

The results of suspended-sediment simulation at Little Mill Creek near Newport provide

information about sediment yields from a predominantly urban drainage area. The results of suspended-sediment simulation at Christina River at

Coochs Bridge provide a measure of the overall

model accuracy on a basin-wide scale. Instantaneous concentrations of suspended solids were

measured for six storms and four base-flow events

in 1998. Reported concentrations of suspended solids (nonfilterable material) were considered estimates for suspended-sediment concentrations.

Suspended-solids concentrations are not always

accurate estimates of suspended-sediment concentrations and tend to be biased low, especially for

conditions when sand-sized particles represent

more than 25 percent of suspended sediment (Gray

and others, 2000). When suspended solids are used

as a surrogate for suspended-sediment concentrations, the resulting errors in load computations can

be as large as several orders of magnitude (U.S.

Geological Survey, 2000). As noted earlier, only

well-simulated storms (simulation error less than

20 percent for storm peaks, for example) would,

ideally, be used for calibration of suspended sediment. In many cases, storms were not well simulated. Observed and simulated streamflow and

suspended sediment for the six sampled storms at

Little Mill Creek near Newport and the five sampled storms at Christina River at Coochs Bridge are

shown in figures 24 and 25. Streamflow is undersimulated and oversimulated for the sampled

storms at the two sites. Some storms are not simulated well probably because of errors in the estimated hourly precipitation record. Simulated

streamflow poorly replicates the occurrence of the

May 1998 storm for Little Mill Creek near Newport

and misses the July 1998 storm for Christina River

at Coochs Bridge. For the storms that are relatively

well simulated, the simulated hourly mean suspended-sediment concentrations range from less

than, similar to, and greater than observed concentrations of suspended solids in discrete samples

collected during those storms. The simulated sharp

rise in suspended-sediment concentrations near

0 40 10 20 30

OBSERVED INSTANTANEOUS WATER TEMPERATURE,

IN DEGREES CELSIUS

0

40

10

20

30

SIMULATED HOURLY MEAN WATER TEMPERATURE,

IN DEGREES CELSIUS

LINE OF IDENTITY

Figure 23. Simulated hourly mean and observed instantaneous

water temperature at streamflow-measurement station 01478000,

Christina River at Coochs Bridge, Del., October 1994–October

1998.
Simulation of Water Quality 49

2400 1200 2400 1200 2400 1200 2400

4 5 6

February 1998

0

1,600

400

800

1,200

SUSPENDED-SEDIMENT CONCENTRATION,

IN MILLIGRAMS PER LITER

0

40

10

20

30

STREAMFLOW, IN CUBIC FEET PER SECOND

2400 0800 1600 2400 0800 1600 2400

1 2

May 1998

0

1,000

200

400

600

800

SUSPENDED-SEDIMENT CONCENTRATION,

IN MILLIGRAMS PER LITER

0

25

5

10

15

20

STREAMFLOW, IN CUBIC FEET PER SECOND

2400 1200 2400 1200 2400 1200 2400

11 12 13

June 1998

0

400

100

200

300

STREAMFLOW, IN CUBIC FEET PER SECOND

0

2,000

500

1,000

1,500

SUSPENDED-SEDIMENT CONCENTRATION,

IN MILLIGRAMS PER LITER

EXPLANATION

SIMULATED STREAMFLOW

OBSERVED STREAMFLOW

SIMULATED SUSPENDED SEDIMENT

OBSERVED SUSPENDED SOLIDS

1600 2400 0800 1600 2400 0800

7 8 9

July 1998

0

2,500

500

1,000

1,500

2,000

SUSPENDED-SEDIMENT CONCENTRATION,

IN MILLIGRAMS PER LITER

0

250

50

100

150

200

STREAMFLOW, IN CUBIC FEET PER SECOND

1600 2400 0800 1600 2400 0800

7 8 9

October 1998

0

150

50

100

STREAMFLOW, IN CUBIC FEET PER SECOND

0

2,000

500

1,000

1,500

SUSPENDED-SEDIMENT CONCENTRATION,

IN MILLIGRAMS PER LITER

2400 1200 2400 1200 2400 1200 2400

8 9 10

March 1998

0

300

100

200

STREAMFLOW, IN CUBIC FEET PER SECOND

0

800

200

400

600

SUSPENDED-SEDIMENT CONCENTRATION,

IN MILLIGRAMS PER LITER

Figure 24. Simulated and observed streamflow and concentrations of suspended sediment and period of

composite sample during six storms in 1998 at streamflow-measurement station 01480095, Little Mill Creek near

Newark, Del.

PERIOD OF COMPOSITE SAMPLE
50 Simulation of Water Quality

2400 1200 2400 1200 2400 1200 2400

7 8 9

October 1998

0

300

100

200

SUSPENDED-SEDIMENT CONCENTRATION,

IN MILLIGRAMS PER LITER

0

250

50

100

150

200

STREAMFLOW, IN CUBIC FEET PER SECOND

2400 1200 2400 1200 2400 1200 2400

8 9 10

March 1998

0

1,000

200

400

600

800

STREAMFLOW, IN CUBIC FEET PER SECOND

0

500

100

200

300

400

SUSPENDED-SEDIMENT CONCENTRATION,

IN MILLIGRAMS PER LITER

2400 0800 1600 2400 0800 1600 2400

1 2

May 1998

0

200

50

100

150

SUSPENDED-SEDIMENT CONCENTRATION,

IN MILLIGRAMS PER LITER

10

60

20

30

40

50

STREAMFLOW, IN CUBIC FEET PER SECOND

2400 1200 2400 1200 2400 1200 2400

11 12 13 June 1998

0

300

100

200

STREAMFLOW, IN CUBIC FEET PER SECOND

0

500

100

200

300

400

SUSPENDED--SEDIMENT CONCENTRATION,

IN MILLIGRAMS PER LITER

2400 1200 2400 1200 2400 1200 2400

7 8 9

July 1998

0

800

200

400

600

SUSPENDED-SEDIMENT CONCENTRATION,

IN MILLIGRAMS PER LITER

0

250

50

100

150

200

STREAMFLOW, IN CUBIC FEET PER SECOND

EXPLANATION

SIMULATED STREAMFLOW

OBSERVED STREAMFLOW

SIMULATED SUSPENDED SEDIMENT

OBSERVED SUSPENDED SOLIDS

Figure 25. Simulated and observed streamflow and concentrations of suspended sediment and period of

composite sample during five storms in 1998 at streamflow-measurement station 01478000, Christina River

at Coochs Bridge, Del.

PERIOD OF COMPOSITE SAMPLE
Simulation of Water Quality 51

the beginning of the rise of streamflow in each

storm is not supported by the few observed data

for these periods, which may be due to errors in

washoff simulation and (or) to in-stream scouring

and hydraulic simulations.

Composite samples collected during storms

at the two nonpoint-source monitoring sites in the

Christina River subbasin in 1998 allow comparison

of simulated and observed loads for the periods

monitored. Peak flows were greatest in the March

1998 storm and least in the May 1998 storm

(table 16). For the sampled storm periods, storm

volume is under- and oversimulated and suspended-sediment loads tend to be oversimulated.

For Little Mill Creek near Newport, the difference

between observed and simulated streamflow

ranged from -49 to 33 percent for individual storms

and was 2 percent for the total of all storms. The

difference between observed and simulated suspended-sediment loads ranged from -43 to

579 percent for individual storms and was

1 percent for the total of all storms. For Christina

River at Coochs Bridge, the difference between

observed and simulated streamflow ranged from

-83 to 68 percent for individual storms and was

-2 percent for the total of all storms. At that site, the

difference between observed and simulated suspended-sediment loads ranged from -47 to

452 percent for individual storms and was

102 percent for the total of all storms.

Comparison of simulated and observed values (table 16) for about half of the storms sampled

at the two sites indicates that when flow is undersimulated or oversimulated, loads of suspended

sediment also are undersimulated or oversimulated, respectively. For example, in a case of oversimulation for the July 1998 storm at Little Mill

Creek near Newport, the error was 13 percent for

simulated streamflow and 43 percent for simulated

suspended-sediment load. In a case of undersimulation for the July 1998 storm at Christina River at

Cooches Bridge, the error was -83 percent for simulated streamflow and -47 percent for simulated

suspended-sediment load. The error in simulated

streamflow contributes to the overall error in simulated loads. The magnitude and sign of the percent

error in streamflow can be compared to the magnitude and percent error in load to indicate whether

Table 16. Simulated and observed streamflow and loads of suspended sediment for storms sampled in 1998

at the nonpoint-source monitoring sites 01480095, Little Mill Creek near Newport, Del., and 01478000, Christina

River at Coochs Bridge, Del.

[ft3/s, cubic feet per second]

Dates of storm

sampling

Peak

discharge1

(ft3/s)

Streamflow (millions of cubic feet) Suspended-sediment load (tons)

Simulated Observed Percentage

difference2 Simulated Observed Percentagedifference2

Little Mill Creek near Newport, Del.

February 4-5 29.1 1.48 2.06 -23 8.52 2.06 313

March 8-9 132 4.79 4.99 -4 11.7 9.94 18

May 1-2 21.3 .51 1.00 -49 4.27 .63 579

June 11-12 264 5.67 4.94 15 25.8 45.2 -43

July 8-9 156 3.13 2.76 13 21.7 15.1 43

October 8-9 41.6 1.74 1.31 33 4.78 3.90 45

Total - all storms 17.3 17.1 2 76.7 76.3 1

Christina River at Coochs Bridge, Del.

March 8-9 747 21.08 22.10 -5 111 46.1 142

May 1-3 45.4 3.60 2.14 68 .48 .40 18

June 11-13 228 12.58 10.53 19 28.9 13.3 116

July 8-9 206 .86 5.13 -83 7.88 14.8 -47

October 8-9 66.5 2.58 1.68 54 2.93 .53 452

Total - all storms 40.69 41.57 -2 151 75.1 102

1 Peak mean hourly discharge during period of composite sampling.

2 100 × (simulated-observed)/observed.
52 Simulation of Water Quality

water-quality concentrations are under- or oversimulated. The nonlinear relation between streamflow and sediment accounts for some of the

differences in errors for streamflow and suspended-sediment simulations. Suspended-sediment simulation is dependent on accuracy of

precipitation data and the flow simulation and has

a large degree of variability.

Simulated concentrations of suspended sediment under base-flow conditions were within a

factor of 10 of observed concentrations for half of

the samples at the two nonpoint-source monitoring sites (fig. 26). For all base-flow samples,

streamflow was well simulated, as shown in

figure 26. Differences larger than an order of magnitude between observed suspended solids and

simulated suspended-sediment concentrations

were associated with an April 1998 sample at Little

Mill Creek near Newport and September 1998

samples at both sites. The April 1998 sample was

collected the day after a storm and a lag in the simulated storm peak resulted in an incorrect lag in

the simulated suspended-sediment peak concentrations. No large storms occurred before the collection of the September 1998 samples, but unexpectedly, the highest observed concentrations of

suspended solids were in samples collected during

the lowest base-flow conditions in September 1998

at the two sites and the source of error for simulated suspended sediment is unknown or possibly

related to sample collection or processing.

Instantaneous loads, calculated from measured streamflows at two USGS streamflow-measurement stations and suspended-solids

concentrations in grab samples collected monthly

or bimonthly by DNREC near those stations also

were used to evaluate model calibration. Differences in location of sample-collection site and

streamflow-measurement site may result in inaccurate characterization of water quality at the streamflow-measurement location. Therefore, the

comparison of simulated and observed concentrations and loads must be considered to have substantial amounts of uncertainty. Samples were

collected at the DNREC site Christina River at Old

Baltimore Pike, which is upstream of the streamflow-measurement station 01478000, Christina

River at Coochs Bridge. Samples also were collected at the DNREC site Little Mill Creek at Atlantic Avenue, which is downstream of the

streamflow-measurement station 01480095, Little

Mill Creek near Newport. However, because of a

large stormwater discharge outfall between the

0 25 5 10 15 20

OBSERVED STREAMFLOW,

0

25

5

10

15

20

SIMULATED STREAMFLOW,

EXPLANATION

LITTLE MILL CREEK NEAR NEWPORT

CHRISTINA RIVER AT COOCHS BRIDGE

0.2 200 0.5 1 2 5 10 20 50 100

OBSERVED SUSPENDED-SOLIDS CONCENTRATION,

IN MILLIGRAMS PER LITER

0.2

200

0.5

1

2

5

10

20

50

100

SIMULATED SUSPENDED-SEDIMENT CONCENTRATION,

IN MILLIGRAMS PER LITER

Figure 26. Simulated hourly mean streamflow and

suspended-sediment concentrations and observed

instantaneous streamflow and total suspended-solids

concentrations under base-flow conditions at monitoring

site 01480095, Little Mill Creek near Newport, Del., and

01478000, Christina River at Coochs Bridge, Del., 1998.

LINE OF IDENTITY

FACTOR OF 10

IN CUBIC FEET PER SECOND

IN CUBIC FEET PER SECOND
Simulation of Water Quality 53

streamflow-measurement station and the DNREC

sampling site at Atlantic Avenue, the DNREC samples may not be representative of water-quality

upstream of the stormwater discharge outfall during stormflow conditions. The instantaneous

streamflows were fairly well simulated at the

Christina River at Coochs Bridge site (fig. 27), with

a median difference between simulated and

observed streamflows of 12 percent. At the Christina River at Coochs Bridge site, many simulated

suspended-sediment instantaneous loads were

within an order of magnitude (or factor of 10) of

observed loads of suspended solids, and in some

cases, were two or more orders of magnitude

larger or smaller than observed loads (fig. 27).

Most of the grab samples were collected from

October 1994 through October 1998 under moderate to low-flow conditions, although a few samples

were collected under relatively high-flow conditions. The median percent difference between simulated suspended-sediment loads and observed

suspended-solids loads was -80 percent at streamflow-measurement station 01478000 and -8 percent

at streamflow-measurement station 01480095.

Although data on monthly and annual loads of

suspended sediment are not available, the median

of instantaneous loads at the these stations provides an estimate of the adequacy of the sediment

calibration as worse than ‘fair’ to ‘good’ using

guidelines described by Donigian and others

(1984).

In summary, the quality of the suspendedsediment calibration ranges from less than ‘fair’

(more than 35 percent error) to ‘good’ (15-25 percent error) for individual storms using criteria

from Donigian and others (1984). Simulated

instantaneous suspended-sediment loads estimated at one long-term fixed time-interval site

commonly were within one order of magnitude of

observed loads of suspended solids but were

sometimes different by larger amounts. These

results indicate the range of variability that might

be expected in simulating individual storms or

instantaneous values. Additional apparent sources

of error may be associated with the use of total suspended-solids concentration as a surrogate for suspended-sediment concentration, which can

underestimate the suspended sediment by up to

several orders of magnitude, especially for sediment loads with greater than 25 percent sand-sized

particles. Comparison of the observed and simulated suspended-sediment concentration duration

curves in the HSPF model for the adjacent Brandywine Creek subbasin suggests that over relatively

long time periods (5 years or more), the model

results are statistically similar to observed data

(Senior and Koerkle, 2003a). This would also be the

expected case in the Christina River subbasin.

Simulated yields of sediment differ by land

use and vary with precipitation from year to year

(table 17). Simulated yields of sediment by land

use were similar in the three segments (tables 17

and 18) and are within the ranges reported for

equivalent land-use types by Dunne and Leopold

(1978, p. 520-522). Most of the simulated sediment

yield was from agricultural land-use areas. Using

pervious-land scour as an estimate of bank erosion,

the average simulated amount of sediment

removed by scour for the years 1994-97 differed

among land uses and ranged from 0 to 13 percent

of the total sediment yield. The highest percentage

of sediment yield produced by scour was in urban

and sewered residential land uses (median values

of 8 and 5 percent, respectively) and the lowest

was in forested and wetland land uses (median

values of 0 percent). In areas of agricultural land

use, the range of average simulated scour (bank

erosion) was about 1 to 3 percent of total sediment

yield for 1994-97 and appears to be slightly lower

or similar to estimates obtained elsewhere. In a

study of sediment sources in two agricultural

basins in the United Kingdom, bank erosion was

estimated to contribute about 10 percent or less of

the sediment yield (Russell and others, 2001).
54 Simulation of Water Quality

0 100 20 40 60 80

OBSERVED STREAMFLOW, IN CUBIC FEET PER SECOND

0

100

20

40

60

80

SIMULATED STREAMFLOW,

0.1 500 0.2 0.5 1 2 5 10 20 50 100200

OBSERVED SUSPENDED-SOLIDS

CONCENTRATION, IN MILLIGRAMS PER LITER

0.1

500

0.2

0.5

1

2

5

10

20

50

100

200

SIMULATED SUSPENDED-SEDIMENT

CONCENTRATION, IN MILLIGRAMS PER LITER

0.1 10,000 1 10 100 1,000

OBSERVED SUSPENDED-SOLIDS LOAD,

IN POUNDS PER HOUR

0.1

10,000

1

10

100

1,000

SIMULATED SUSPENDED-SEDIMENT LOAD,

IN POUNDS PER HOUR

0 50 10 20 30 40

OBSERVED STREAMFLOW, IN CUBIC FEET PER SECOND

0

50

10

20

30

40

SIMULATED STREAMFLOW,

0.5 500 1 2 5 10 20 50 100 200

OBSERVED SUSPENDED-SOLIDS

CONCENTRATION, IN MILLIGRAMS PER LITER

0.5

500

1

2

5

10

20

50

100

200

SIMULATED SUSPENDED-SEDIMENT

CONCENTRATION, IN MILLIGRAMS PER LITER

0.1 10,000 1 10 100 1,000

OBSERVED SUSPENDED-SOLIDS LOAD,

IN POUNDS PER HOUR

0.1

10,000

1

10

100

1,000

SIMULATED-SUSPENDED-SEDIMENT LOAD,

IN POUNDS PER HOUR

Figure 27. Comparison of simulated hourly mean streamflow, suspended-sediment concentrations and

suspended-sediment loads to observed instantaneous streamflow, total suspended-solids concentrations and

hourly mean suspended-sediment loads at streamflow-measurement stations (A) 01480095, Little Mill Creek near

Newport, Del., and (B) 01478000, Christina River at Coochs Bridge, Del., October 1994–October 1998. Observed

suspended-solids data for Little Mill Creek at Atlantic Avenue and Christina River at Old Baltimore Pike from

Delaware Department of Natural Resources and Environmental Control were used to estimate observed

suspended-sediment concentrations at near Newport and Coochs Bridge stations.

FACTOR OF 10 FACTOR OF 10

LINE OF IDENTITY LINE OF IDENTITY

LINE OF IDENTITY LINE OF IDENTITY

LINE OF IDENTITY

LINE OF IDENTITY

IN CUBIC FEET PER SECOND

IN CUBIC FEET PER SECOND

A

A

A

B

B

B
Simulation of Water Quality 55

Table 17. Observed annual precipitation and simulated annual sediment yields

by land use for three segments of Hydrological Simulation Program–Fortran

(HSPF) model for Christina River subbasin, 1995-97

Year

Segment 1995 1996 1997 1995-97

average

Precipitation (inches) 5,8 38.1 56.9 34.7 43.2

Simulated sediment yield (tons per acre per year) by land-use category1

Residential - unsewered 5 .15 .389 .035 .191

Residential - sewered 5 .203 .524 .047 .258

Urban 5 .427 .704 .073 .401

Agricultural - animal/crop 5 1.46 2.44 .586 1.495

Agricultural - row crop 5 1.44 2.43 .563 1.478

Agricultural - mushroom 5 1.44 2.45 .489 1.460

Forested 5 .052 .153 .012 .072

Open 5 .216 .550 .0496 .272

Wetlands/water 5 .003 .009 .001 .004

Undesignated 5 .214 .547 .049 .270

Impervious - residential 5 .113 .118 .118 .116

Impervious - urban 5 .657 .682 .68 .673

Simulated sediment yield (tons per acre per year) by land-use category1

Residential - unsewered 8 .181 .338 .037 .185

Residential - sewered 8 .258 .471 .053 .261

Urban 8 .500 .576 .060 .379

Agricultural - animal/crop 8 1.52 2.32 .547 1.462

Agricultural - row crop 8 1.51 2.3 .524 1.445

Agricultural - mushroom 8 1.54 2.32 .492 1.451

Forested 8 .007 .132 .011 .050

Open 8 .263 .477 .054 .265

Wetlands/water 8 .003 .007 .0004 .003

Undesignated 8 .262 .477 .054 .264

Impervious - residential 8 .113 .118 .118 .116

Impervious - urban 8 .656 .681 .682 .673

Precipitation (inches) 9 38.0 49.7 26.5 38.1

Simulated sediment yield (tons per acre per year) by land-use category1

Residential - unsewered 9 .142 .124 .00184 .089

Residential - sewered 9 .358 .223 .00479 .195

Urban 9 .482 .289 .0092 .260

Agricultural - animal/crop 9 1.05 .903 .0133 .655

Agricultural - row crop 9 1.04 .854 .0116 .635

Agricultural - mushroom 9 1.11 1.01 .0215 .714

Forested 9 .0057 .007 .00003 .004

Open 9 .181 .155 .00245 .113

Wetlands/water 9 .00065 .00056 .000005 .000

Undesignated 9 .178 .153 .00233 .111

Impervious - residential 9 .117 .113 .114 .115

Impervious - urban 9 .679 .656 .662 .666

1 In pervious areas, unless noted.
56 Simulation of Water Quality

Dissolved Oxygen and

Biochemical Oxygen Demand

Dissolved oxygen and biochemical oxygen

demand (BOD) must be simulated to simulate

nutrients in the stream. The simulation of dissolved oxygen included the in-stream effects of air

and water temperature, reaeration, advection, and

algal activity (photosynthesis and respiration).

Oxygen concentrations were simulated in landsurface runoff and were fixed in interflow and

ground water. Dissolved-oxygen concentration

data collected intermittently near two streamflowmeasurement stations in the Christina River subbasin were used to evaluate the dissolved-oxygen

simulation. To reproduce the temporal pattern of

diurnal fluctuations in dissolved oxygen concentrations observed at three continuous monitoring

sites on the Brandywine Creek, simulation of

plankton was needed (Senior and Koerkle, 2003a)

and, therefore, simulation of periphyton and phytoplankton was included in the water-quality modeling for the Christina River subbasin. The

simulation of BOD from nonpoint sources

included transport of BOD from land to streams

and in-stream processes of BOD decay, settling,

and advection. Concentrations of BOD in the soil

(sediment), interflow, and ground water were fixed

in amounts that differed by land use. Estimates of

BOD in soil, interflow, and ground water were

derived from an HSPF model of the Pautuxent

River Basin in northeastern Maryland (Stephen

Preston, U.S. Geological Survey, written commun.,

1995). BOD concentration data from the analysis of

grab and composite stream samples collected at

the nonpoint-source monitoring site were used to

evaluate the BOD simulation.

The general pattern of seasonal changes in

dissolved oxygen concentrations was simulated by

the model with varying degrees of accuracy, as

shown in figure 28 for the data collected near the

streamflow-measurement stations 01480095, Little

Mill Creek near Newport, Del., and 01478000,

Christina River at Coochs Bridge, Del. The

monthly DNREC water-quality data were collected

near, but not at, the streamflow-measurement stations and therefore may not accurately represent

water quality at those stations. Simulated concentrations of dissolved oxygen tended to be higher

than observed concentrations at Christina River at

Coochs Bridge, especially in the summer months

(fig. 28). The diurnal fluctuation in concentrations

of dissolved oxygen attributed to processes of algal

photosynthesis and respiration becomes more pronounced in the summer months than at other times

of the year.

Table 18. Observed annual precipitation and simulated average annual

sediment yield by land use for pervious and impervious land areas in

three segments of Hydrological Simulation Program–Fortran (HSPF)

model for Christina River subbasin, 1995-97

1995-97 Average

Segment 5 Segment 8 Segment 9 Average of all

segments

Precipitation (inches) 43.2 43.2 38.1 41.5

Average sediment yield (tons per acre per year) by land-use category1

Residential - unsewered .191 .185 .089 .155

Residential - sewered .258 .261 .195 .238

Urban .401 .379 .260 .347

Agricultural - animals/crops 1.50 1.46 .655 1.20

Agricultural - row crop 1.48 1.45 .635 1.19

Agricultural - mushroom 1.46 1.45 .714 1.21

Forested .072 .050 .004 .042

Open .272 .265 .113 .216

Wetlands/water .004 .003 .000 .003

Undesignated .270 .264 .111 .215

Impervious - residential .116 .116 .115 .116

Impervious - urban .673 .673 .666 .671

1 In pervious areas, unless noted.
Simulation of Water Quality 57

O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O

1994 1995 1996 1997 1998

0

20

5

10

15

DISSOLVED OXYGEN CONCENTRATION,

IN MILLIGRAMS PER LITER

O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O

1994 1995 1996 1997 1998

4

16

6

8

10

12

14

DISSOLVED OXYGEN CONCENTRATION,

IN MILLIGRAMS PER LITER

Figure 28. Simulated daily mean dissolved oxygen concentrations at streamflow-measurement stations

01480095, Little Mill Creek near Newport, Del., and observed instantaneous dissolved-oxygen

concentrations at water-quality monitoring site 106281, Little Mill Creek at Atlantic Avenue (top), and

simulated daily mean dissolved oxygen concentrations at streamflow-measurement station 01478000,

Christina River at Coochs Bridge, Del., and observed instantaneous dissolved oxygen concentrations at

water-quality monitoring site 106141, Christina River at Old Baltimore Pike (bottom), October 1994–October

1998. (Water-quality data from Delaware Department of Natural Resources and Environmental Control.)

OBSERVED

SIMULATED

OBSERVED

SIMULATED

01480095 LITTLE MILL CREEK NEAR NEWPORT

01478000 CHRISTINA RIVER AT COOCHS BRIDGE
58 Simulation of Water Quality

At Little Mill Creek near Newport, the difference between simulated hourly mean and

observed instantaneous oxygen concentrations

(measured at Little Mill Creek at Atlantic Avenue)

ranged from -59 to 86 percent [100 x (simulated -

observed)/observed] and the average difference

was 13 percent for 35 observations made from

October 1994 through October 1998. At Christina

River at Coochs Bridge, the difference between

simulated hourly mean and observed instantaneous oxygen concentrations (measured upstream

at Old Baltimore Pike) ranged from -19 to

71 percent and the average difference was

33 percent for 37 observations made from October

1994 through October 1998. These results indicate

that dissolved oxygen concentration tends to be

slightly to moderately oversimulated at the Little

Mill Creek near Newport and Christina River at

Coochs Bridge sites (fig. 29).

The simulation of phytoplankton in the

Christina River subbasin was evaluated using

chlorophyll-a concentration data for grab samples

collected under base-flow conditions in 1998 as

part of the nonpoint-source monitoring at two sites

and over a range of hydrologic conditions in 1994-

98 as part of state monthly monitoring at two

streamflow-measurement stations in Delaware.

Evaluation of the limited data collected and simulated results under base-flow conditions indicates

that concentrations of chlorophyll a are undersimulated at both sites and the undersimulation is

more pronounced at the Christina River at Coochs

Bridge site than at the Little Mill Creek near Newport site (fig. 30). Although the model apparently

fails to adequately simulate chlorophyll a at the

Coochs Bridge site in particular, observed concentrations at that site typically were low (8 mg/L or

less), and the performance of the model in simulating nutrient concentrations probably is not affected

to a great extent by undersimulation of in-stream

algal processes. The relative amounts of undersimulation at the two sites also are shown by the larger

amount of data collected under state monitoring at

nearby locations (fig. 30). The highest concentration of chlorophyll a was measured in the samples

at the two sites collected under the highest flow

conditions of all samples and may include chlorophyll a from sources (such as periphyton) disturbed by high-flow conditions.

Samples for BOD analysis were collected

under stormflow and base-flow conditions in 1998

at the two nonpoint-source monitoring sites,

01480095, Little Mill Creek near Newport, Del.,

0 16 2 4 6 8 10 12 14

OBSERVED INSTANTANEOUS DISSOLVED OXYGEN

CONCENTRATION, IN MILLIGRAMS PER LITER

0

16

2

4

6

8

10

12

14

SIMULATED HOURLY MEAN DISSOLVED OXYGEN

CONCENTRATION, IN MILLIGRAMS PER LITER

0 16 2 4 6 8 10 12 14

OBSERVED INSTANTANEOUS DISSOLVED OXYGEN

CONCENTRATION, IN MILLIGRAMS PER LITER

0

16

2

4

6

8

10

12

14

SIMULATED HOURLY MEAN DISSOLVED OXYGEN

CONCENTRATION, IN MILLIGRAMS PER LITER

Figure 29. Simulated hourly mean dissolved oxygen

concentrations at streamflow-measurement stations

01480095, Little Mill Creek near Newport, Del. (top), and

observed instantaneous dissolved oxygen concentrations

at water-quality monitoring site 106281, Little Mill Creek at

Atlantic Avenue (top), and simulated hourly mean dissolved

oxygen concentration at streamflow-measurement station

01478000 Christina River at Coochs Bridge, Del., and

observed instantaneous dissolved oxygen concentrations

at water-quality monitoring site 106141, Christina River

at Old Baltimore Pike (bottom), October 1994–October

1998. (Water-quality data from Delaware Department of

Natural Resources and Environmental Control.)

LINE OF IDENTITY

LINE OF IDENTITY

LITTLE MILL CREEK NEAR NEWPORT

CHRISTINA RIVER AT COOCHS BRIDGE
Simulation of Water Quality 59

and 01478000, Christina River at Coochs Bridge,

Del. Comparison of simulated and observed BOD

loads under stormflow conditions indicates that

BOD is undersimulated often when stormflow is

undersimulated and often oversimulated when

stormflow is oversimulated for storms at the two

sites (table 19). Errors in BOD simulation may

result in undersimulation or oversimulation of

BOD decay and consequent oxygen depletion. The

amount of oxygen in the stream reach can affect

the extent of nitrification and denitrification reactions. No bias in the simulation of BOD under

base-flow conditions was apparent for the limited

number of samples (fig. 31). Concentrations of

BOD in some of the samples collected in 1998

under base-flow conditions were reported as less

than the detection level of 2.4 mg/L (fig. 31).

Concentration data in grab samples collected

monthly by DNREC near two streamflow-measurement stations under a range of hydrologic conditions also were used to evaluate the simulation

of BOD. As noted earlier, most of the samples were

collected under moderate or base-flow conditions.

The DNREC water-quality data were collected

near but not at the streamflow-measurement stations and therefore may not accurately represent

water quality at those stations. The average difference between simulated and observed BOD concentrations was -15 percent for Little Mill Creek

and 5 percent for Christina River at Coochs Bridge

(fig. 31). This pattern of differences between simulated and observed concentrations is the converse

of the dissolved oxygen simulation. Apparent

error trends in BOD and dissolved oxygen simulations may result in part from the inverse relation

between these constituents. Errors in load estimates of BOD from point sources and nonpoint

sources may contribute to overall errors of BOD instream concentrations.

Overall, the simulation of oxygen-related

constituents results in ‘fair’ estimates of dissolved

oxygen concentrations that are needed for the instream simulation of nutrients. Errors in the simulation of BOD and plankton affect the simulation of

in-stream dissolved oxygen concentrations. Undersimulation of BOD would result in oversimulation

of dissolved oxygen. Undersimulation of plankton

could result in the undersimulation of dissolved

oxygen during the day, when photosynthesis

occurs, and oversimulation of dissolved oxygen

during the night, when respiration processes are

dominant. Further, undersimulation of plankton

could affect the simulations of in-stream concentra0 12 2 4 6 8 10

OBSERVED INSTANTANEOUS CONCENTRATION OF

CHLOROPHYLL a, IN MICROGRAMS PER LITER

0

12

2

4

6

8

10

EXPLANATION

MONTHLY SAMPLES

1998 BASE-FLOW SAMPLES

0 12 2 4 6 8 10 0

12

2

4

6

8

10

SIMULATED HOURLY MEAN CONCENTRATION OF

CHLOROPHYLL a, IN MILLIGRAMS PER LITER

Figure 30. Simulated hourly mean chlorophyll-a

concentrations at streamflow-measurement stations

01480095, Little Mill Creek near Newport, Del.,

and observed instantaneous dissolved oxygen concentrations at water-quality monitoring site 106281, Little

Mill Creek at Atlantic Avenue (top), and simulated hourly

mean chlorophyll-a concentrations at streamflowmeasurement station 01478000, Christina River at

Coochs Bridge, Del., and observed instantaneous

chlorophyll-a concentrations at water-quality monitoring

site 106141, Christina River at Old Baltimore Pike

(bottom), October 1994–October 1998. (Water-quality

data from Delaware Department of Natural Resources

and Environmental Control.)

LITTLE MILL CREEK NEAR NEWPORT

CHRISTINA RIVER AT COOCHS BRIDGE

OBSERVED INSTANTANEOUS CONCENTRATION OF

CHLOROPHYLL a, IN MICROGRAMS PER LITER

SIMULATED HOURLY MEAN CONCENTRATION OF

CHLOROPHYLL a, IN MILLIGRAMS PER LITER
60 Simulation of Water Quality

Table 19. Simulated and observed streamflow and loads of biochemical oxygen demand for storms sampled in 1998

at the two nonpoint-source monitoring sites, 01480095, Little Mill Creek near Newport, Del., and 01478000, Christina

River at Coochs Bridge, Del.

[BOD, biochemical oxygen demand; ft3/s, cubic feet per second]

Dates of storm

sampling

Peak

discharge1

(ft3/s)

Streamflow (millions of cubic feet) BOD load (tons)

Simulated Observed Percentage

difference2 Simulated Observed Percentagedifference2

Little Mill Creek near Newport, Del.

February 4-5 29.1 1.48 2.06 -23 0.70 0.41 73

March 8-9 132 4.79 4.99 -4 .84 .93 -9

May 1-2 21.3 .51 1.00 -49 .13 .15 -12

June 11-12 264 5.67 4.94 15 1.35 1.05 29

July 8-9 156 3.13 2.76 13 1.53 .63 143

October 8-9 41.6 1.74 1.31 33 .81 .21 291

Total - all storms 17.3 17.1 2 5.37 3.27 59

Christina River at Coochs Bridge, Del.

March 8-9 747 21.08 22.10 -5 2.81 4.05 -31

May 1-3 45.4 3.60 2.14 68 .62 .38 65

June 11-13 228 12.58 10.53 19 1.71 4.66 -63

July 8-9 206 .86 5.13 -83 .21 .81 -74

October 8-9 66.5 2.58 1.68 54 .56 .44 29

Total - all storms 40.69 41.57 -2 5.91 10.3 -43

1 Peak mean hourly discharge during period of composite sampling.

2 100 × (simulated-observed)/observed.
Simulation of Water Quality 61

tions of nutrients, especially ammonia and orthophosphate, by undersimulating nutrient uptake

and release.

Nitrogen

Two inorganic species of nitrogen, nitrate

and ammonia, were simulated. Nitrogen loads

from point and nonpoint sources were included in

the simulation. Loads from point-source discharges were estimated from reported average

monthly data for input on an hourly time step to

the model. For most point-source discharges,

nitrate was estimated from reported ammonia

loads using the ratios specified in USEPA, Region 3

(2000a) and nitrite was assumed to be negligible.

The ratio of nitrate to ammonia in point-source

effluent used for model data sets was 0.84 for small

wastewater treatment plants (WWTPs), 314 for

advanced secondary treatment type 1 WWTPs, 157

for advanced secondary treatment type 2 WWTPs,

and 0.21 for industrial discharges. In the Christina

River subbasin, all WWTPs were considered small

plants (U.S. Environmental Protection Agency,

2000a). For nonpoint sources, concentrations of

nitrate and ammonia in sediment (soil), interflow,

and ground water were estimated as fixed concentrations that differed by land use. Nitrate was

assumed to be transported solely in the dissolved

form. Ammonia was assumed to be transported in

dissolved and adsorbed forms.

Water-quality data from the nonpoint-source

monitoring stations, 01480095 Little Mill Creek

near Newport, Del., and 01478000 Christina River

at Coochs Bridge, Del., were used in the calibration

of concentrations of dissolved nitrate and dissolved and particulate ammonia nitrogen in stormflow and base flow. Simulated and observed

concentrations of dissolved nitrate are shown in

figure 32 for one of the better simulated storms out

of the storms sampled at each the two nonpointsource monitoring sites. Composite samples were

collected for six storms at Little Mill Creek near

Newport and five storms at Christina River at

Coochs Bridge and the number of discrete samples

varied at each site for the storms sampled in 1998.

Observed and simulated nitrate concentrations

generally decrease as streamflow increases during

storms (fig. 32).

Data from composite stormflow samples collected in 1998 were used in the calculation of loads

of dissolved nitrate and dissolved and particulate

0 15 5 10

OBSERVED INSTANTANEOUS BIOCHEMICAL OXYGEN DEMAND

CONCENTRATION, IN MILLIGRAMS PER LITER

0

15

5

10

SIMULATED HOURLY MEAN BIOCHEMICAL OXYGEN DEMAND

CONCENTRATION, IN MILLIGRAMS PER LITER

EXPLANATION

MONTHLY SAMPLES

1998 BASE-FLOW SAMPLES

0 15 5 10

OBSERVED INSTANTANEOUS BIOCHEMICAL OXYGEN DEMAND

CONCENTRATION, IN MILLIGRAMS PER LITER

0

15

5

10

SIMULATED HOURLY MEAN BIOCHEMICAL OXYGEN DEMAND

CONCENTRATION, IN MILLIGRAMS PER LITER

Figure 31. Simulated hourly mean biochemical oxygen

demand concentrations at streamflow-measurement

station 01480095, Little Mill Creek near Newport, Del.,

and observed instantaneous 20-day biochemical oxygen

demand concentrations at water-quality monitoring site

106281, Little Mill Creek at Atlantic Avenue (top), and

simulated hourly mean biochemical oxygen demand

concentrations at streamflow-measurement station

01478000, Christina River at Coochs Bridge, Del., and

observed instantaneous 20-day biochemical oxygen

demand concentrations at water-quality monitoring site

106141, Christina River at Old Baltimore Pike (bottom),

October 1994–October 1998. (Water-quality data from

Delaware Department of Natural Resources and

Environmental Control.)

LITTLE MILL CREEK NEAR NEWPORT

CHRISTINA RIVER AT COOCHS BRIDGE
62 Simulation of Water Quality

ammonia nitrogen. Calculated loads served as the

observed values in overall evaluation of nitrogen

transport during storms.

Simulated and observed streamflow and

load data for dissolved nitrate for sampled storm

events are presented in table 20. For the sampled

storm periods, nitrate loads were undersimulated

at Little Mill Creek near Newport and under- and

oversimulated at Christina River at Coochs Bridge.

For some storms at each of the two sites, streamflow volume and nitrate loads were undersimulated. At Little Mill Creek near Newport, the

difference between observed and simulated

streamflow ranged from -49 to 33 percent for individual storms and was 2 percent for the total of all

storms, and the difference between observed and

simulated nitrate loads ranged from -12 to

-65 percent for individual storms and was -38 percent for the total of all storms. The error in simulated streamflow contributes to the overall error in

simulated loads. The magnitude and sign of the

percent error in streamflow can be compared to the

magnitude and percent error in load to indicate

whether water-quality concentrations are underor oversimulated. At Christina River at Coochs

Bridge, the difference between observed and simulated streamflow ranged from -83 to 68 percent for

individual storms and was -2 percent for the total

of all storms. The difference between observed and

simulated nitrate loads ranged from -54 to 88 percent for individual storms and was 5 percent for

the total of all storms. Using an approach

described in the section on simulation of suspended sediment, the cumulative error in the simulated nitrate component of load, adjusted for the

cumulative error in simulated streamflow, is

39 percent for the Little Mill Creek near Newport

site and 7 percent for the Christina River at Coochs

Bridge site. At both monitoring sites, the undersimulation of nitrate may be related to errors in

estimating contributions of nitrate from point

sources in additions to those associated with

nitrate from nonpoint sources.

Simulated concentrations of dissolved

nitrate in base flow were within 1.2 mg/L or

65 percent of observed concentrations at the nonpoint-source monitoring sites near Newport and at

Coochs Bridge (fig. 33). Streamflow was well simulated for all base-flow samples, as shown in figure

26. The monitoring sites at Little Mill Creek near

Newport and Christina River at Coochs Bridge are

downstream of point-source discharges that can

affect concentrations of nitrate and other constitu2400 1200 2400 1200 2400 1200 2400

8 9 10

March 1998

0

1,000

200

400

600

800

STREAMFLOW,

0

4.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

DISSOLVED NITRATE CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

EXPLANATION

SIMULATED STREAMFLOW

OBSERVED STREAMFLOW

SIMULATED NITRATE

OBSERVED NITRATE

2400 1200 2400 1200 2400 1200 2400

8 9 10

March 1998

0

300

100

200

STREAMFLOW,

0

4.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

DISSOLVED NITRATE CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

Figure 32. Simulated and observed streamflow and

concentrations of dissolved nitrate and period of

composite sample for one of the better simulated storms

in 1998 at each of the streamflow-measurement stations

01480095, Little Mill Creek near Newark, Del., and

01478000, Christina River at Coochs Bridge, Del.

LITTLE MILL CREEK NEAR NEWPORT

CHRISTINA RIVER AT COOCHS BRIDGE

IN CUBIC FEET PER SECOND IN CUBIC FEET PER SECOND

PERIOD OF COMPOSITE SAMPLE
Simulation of Water Quality 63 Table 20. Simulated and observed streamflow and loads of dissolved nitrate, dissolved ammonia, and particulate ammonia for storms samp

nonpoint-source monitoring sites, 01480095, Little Mill Creek near Newport, Del., and 01478000, Christina River at Coochs Bridge, Del. [ft3/s, cubic feet per second] Dates of storm sampling Peak dis- charge1 (ft3/s) 1 Peak mean hourly discharge during period of composite sampling. Streamflow (millions of cubic feet) Nitrate load (pounds as nitrogen) Dissolved ammonia load (pounds as nitrogen) 

Simulated Observed Percent- age difference2 2 100 × (simulated-observed)/observed. Simulated Observed Percent- age difference2 Simulated Observed Percent- age difference2 Simu

Little Mill Creek near Newport, Del. February 4-5 29.1 1.48 2.06 -23 76.6 120 -36 7.30 12.6 -42 1.2

March 8-9 132 4.79 4.99 -4 146 165 -12 8.94 20.8 -57 .May 1-2 21.3 .51 1.00 -49 34.9 58 -40 2.86 .75 279 .June 11-12 264 5.67 4.94 15 81.7 232 -65 16.3 38.1 -57 2.

July 8-9 156 3.13 2.76 13 77.8 112 -31 16.6 14.3 16 4.2October 8-9 41.6 1.74 1.31 33 37.3 47.4 -21 9.03 1.73 421 .8

Total - all storms 17.3 17.1 2 454 735 -38 61.0 88.3 -31 10.5 

Christina River at Coochs Bridge, Del. March 8-9 747 21.08 22.10 -5 1,153 820 41 48.3 72.0 -35 5.3

May 1-3 45.4 3.60 2.14 68 409 217 88 26.5 4.99 430 .0June 11-13 228 12.58 10.53 19 437 672 -35 49.3 31.3 58 2.6

3 Reported concentration of total ammonia was less than that for dissolved ammonia. 

July 8-9 206 .86 5.13 -83 130 283 -54 8.03 11.4 -29 1.October 8-9 66.5 2.58 1.68 54 63.2 100 37 15.2 4.27 4 Estimated dissolved ammonia concentration from reported concentrations of <0.005 mg/L as N dissolved ammonia by assuming 0.5 times the repor

dissolved ammonia. 5,624 .3

5 Estimated particulate ammonia concentration from reported concentrations of 0.011 mg/L as N total ammonia and <0.005 mg/L as N dissolved amm

reporting level (0.0025 N mg/L) for dissolved ammonia. 

Total - all storms 40.69 41.57 -2 2,191 2,091 5 147 122 21 10.
64 Simulation of Water Quality

ents. Observed hourly concentrations of nitrate for

sewage treatment plant discharges were not available but were interpolated from reported average

monthly concentrations of ammonia assuming a

constant ratio of nitrate to ammonia. The ratio of

nitrate to ammonia in effluent probably fluctuates

through time.

Concentration data for grab samples collected by DNREC near two streamflow-measurement stations under a range of hydrologic conditions also were used to evaluate the simulation of

nitrate. Both of the sites are downstream of pointsource discharges. As noted earlier, most of the

samples were collected under moderate or baseflow conditions. Simulated concentrations generally were similar or somewhat higher than

observed nitrate concentrations at Christina River

at Coochs Bridge and were similar or somewhat

lower at Little Mill Creek near Newport (fig. 34).

The median difference between simulated and

observed nitrate concentrations was 63 percent for

Christina River at Coochs Bridge and -20 percent

for Little Mill Creek near Newport. Errors in load

estimates of nitrate from point sources and nonpoint sources and in-stream processes may contribute to overall errors of in-stream nitrate

concentrations. Errors in streamflow simulations

(fig. 27) contribute to overall error in load simu0 4 1 2 3

OBSERVED NITRITE PLUS NITRATE CONCENTRATION, IN MILLIGRAMS PER LITER AS N

0

4

1

2

3

SIMULATED NITRATE CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

EXPLANATION

LITTLE MILL CREEK NEAR NEWPORT

CHRISTINA RIVER AT COOCHS BRIDGE

0 0.5 0.1 0.2 0.3 0.4

OBSERVED DISSOLVED AMMONIA CONCENTRATION, IN MILLIGRAM PER LITER AS N

0

0.5

0.1

0.2

0.3

0.4

SIMULATED DISSOLVED AMMONIA CONCENTRATION, IN MILLIGRAM PER LITER AS N

0 0.04 0.01 0.02 0.03

OBSERVED PARTICULATE AMMONIA CONCENTRATION, IN MILLIGRAM PER LITER AS N

0

0.04

0.01

0.02

0.03

SIMULATED PARTICULATE AMMONIA CONCENTRATION, IN MILLIGRAM PER LITER AS N

Figure 33. Simulated and observed concentrations of (A) nitrate, (B) dissolved ammonia, and (C) particulate

ammonia during base-flow conditions in 1998 at streamflow-measurement stations 01480095, Little Mill Creek

near Newport, Del. and 01478000, Christina River at Coochs Bridge, Del.

LINE OF IDENTITY

LINE OF IDENTITY

LINE OF IDENTITY

B. DISSOLVED AMMONIA C. PARTICULATE AMMONIA

A. NITRATE
65

0 4 1 2 3

OBSERVED INSTANTANEOUS NITRATE CONCENTRATION, IN MILLIGRAMS PER LITER AS N

0

4

1

2

3

SIMULATED HOURLY MEAN NITRATE CONCENTRATION, IN MILLIGRAMS PER LITER AS N

0.2 20 0.5 1 2 5 10

OBSERVED NITRATE LOAD,

 IN POUNDS AS NITROGEN PER HOUR

0.2

20

0.5

1

2

5

10

SIMULATED HOURLY MEAN NITRATE LOAD,

IN POUNDS AS NITROGEN PER HOUR

0 4 1 2 3

OBSERVED INSTANTANEOUS NITRATE CONCENTRATION, IN MILLIGRAMS PER LITER AS N

0

4

1

2

3

SIMULATED HOURLY MEAN NITRATE CONCENTRATION, IN MILLIGRAMS PER LITER AS N

0.05 10 0.1 0.2 0.5 1 2 5

OBSERVED NITRATE LOAD,

 IN POUNDS AS NITROGEN PER HOUR

0.05

10

0.1

0.2

0.5

1

2

5

SIMULATED HOURLY MEAN NITRATE LOAD,

IN POUNDS AS NITROGEN PER HOUR

B. CHRISTINA RIVER

A. LITTLE MILL CREEK

LINE OF IDENTITY

B. CHRISTINA RIVER

A. LITTLE MILL CREEK

FACTOR OF 3

FACTOR OF 2

LINE OF IDENTITY

LINE OF IDENTITY

LINE OF IDENTITY

Figure 34. Simulated hourly mean nitrate concentrations and loads at streamflow-measurement stations

(A) 01480095, Little Mill Creek near Newport, Del., and (B) 01478000, Christina River at Coochs Bridge,

Del., and observed instantaneous nitrate concentrations and loads at water-quality monitoring sites

(A) 106281, Little Mill Creek at Atlantic Avenue and (B) 106141, Christina River at Old Baltimore Pike,

October 1994–October 1998. Observed loads calculated from observed concentrations at water-quality

monitoring sites and streamflow at streamflow-measurement stations. (Water-quality data from Delaware

Department of Natural Resources and Environmental Control.)

NEAR NEWPORT AT COOCHS BRIDGE

NEAR NEWPORT AT COOCHS BRIDGE
66 Simulation of Water Quality

lations at the two sites. Simulated nitrate loads

generally were within a factor of 2 or less of

observed loads at Little Mill Creek near Newport

and within a factor of 3 of observed loads at Christina River at Coochs Bridge.

At the Christina River at Coochs Bridge site,

there is an apparent bias (high) in the nitrate concentration and load simulation that may be caused

by errors in point-source and nonpoint-source contributions. Comparison of 1994-98 DNREC monitoring data collected at Christina River at Rt. 273, a

site that is upstream of the West Branch Christina

River confluence and therefore upstream of pointsource discharges, and simulated nitrate concentrations for reach 2 of the model indicates that

nitrate concentrations also may be oversimulated

in reach 2. The Christina River at Rt. 273 site

(DNREC monitoring site 106191) is not located at

the bottom of reach 2 and therefore may not represent water quality for the entire reach 2. The Rt. 273

site excludes some drainage area of reach 2 that is

urbanized land, which yields relatively small

amounts of nitrate and thus results in diluting instream nitrate concentrations. The median difference between nitrate concentrations simulated for

reach 2 and observed at Christina River at Rt. 273

(DNREC monitoring site 106191) is about 20 percent. The apparent oversimulation of nitrate concentrations in reach 2 probably accounts for some

but not all of the oversimulation of nitrate at Christina River at Coochs Bridge.

Simulated concentrations of dissolved and

particulate ammonia were compared to observed

concentrations of dissolved and particulate ammonia in stormflow and base-flow conditions where

observed particulate ammonia concentrations

were calculated by subtracting dissolved ammonia

concentrations from total ammonia concentrations.

Review of 1998 nonpoint-source monitoring data

indicates that, on average, dissolved ammonia represents about 80 percent of total ammonia concentrations for samples collected at Little Mill Creek

near Newport and Christina River at Coochs

Bridge.

Simulated and observed concentrations of

dissolved and particulate ammonia for one of the

better simulated storms of the six storms sampled

at each of the two nonpoint-source monitoring

sites, Little Mill Creek near Newport and Christina

River at Coochs Bridge, are shown in figures 35

and 36. Simulated water quality for all storms at

both sites are shown in Appendix 2. Observed and

2400 1200 2400 1200 2400 1200 2400

8 9 10

March 1998

0

1,000

200

400

600

800

STREAMFLOW, IN CUBIC FEET PER SECOND

0

0.5

0.1

0.2

0.3

0.4

DISSOLVED AMMONIA CONCENTRATION,

IN MILLIGRAM PER LITER AS N

EXPLANATION

SIMULATED STREAMFLOW

OBSERVED STREAMFLOW

SIMULATED DISSOLVED AMMONIA

OBSERVED DISSOLVED AMMONIA

2400 1200 2400 1200 2400 1200 2400

8 9 10

March 1998

0

300

100

200

STREAMFLOW, IN CUBIC FEET PER SECOND

0

0.5

0.1

0.2

0.3

0.4

DISSOLVED AMMONIA CONCENTRATION,

IN MILLIGRAM PER LITER AS N

Figure 35. Simulated and observed streamflow and

concentrations of dissolved ammonia and period of

composite sample for one of the better simulated storms

in 1998 at each of the streamflow-measurement stations

01480095, Little Mill Creek near Newark, Del., and

01478000, Christina River at Coochs Bridge, Del.

LITTLE MILL CREEK NEAR NEWPORT

CHRISTINA RIVER AT COOCHS BRIDGE

PERIOD OF COMPOSITE SAMPLE
Simulation of Water Quality 67

simulated concentrations of dissolved ammonia

appear to decrease slightly as streamflow increases

during the March storm (fig. 35). Observed and

simulated concentrations of particulate ammonia

appear to increase as streamflow increases during

the March storm (fig. 36). Though the general

range of observed dissolved and particulate

ammonia concentrations during storms are simulated by the model, errors or differences between

observed and simulated concentrations are apparent. Errors or differences between observed and

simulated particulate ammonia concentrations are

due in part to errors in flow, suspended-sediment

simulation, and timing of rainfall for storms. In

addition, the available nonpoint-source monitoring data are insufficient to calibrate the effects of

phytoplankton on in-stream dissolved ammonia

concentrations, and the phytoplankton simulation

is a source of error for the dissolved ammonia simulation.

Data from composite stormflow samples collected in 1998 were used in the calculation of loads

of dissolved nitrate and dissolved and particulate

ammonia nitrogen. Calculated loads served as the

observed values in overall evaluation of nitrogen

transport during storms. Simulated and observed

streamflow and loads of dissolved and particulate

ammonia nitrogen for storm events occurring in

1998 are presented in table 20. Observed loads of

dissolved ammonia commonly were greater than

observed loads of particulate ammonia except for

one storm in October 1998, for which the particulate ammonia was greater than the dissolved

ammonia load. The analytical results for the

ammonia concentrations in the October composite

storm sample are questionable, however.

For the sampled storm periods, dissolved

ammonia loads were under- and oversimulated at

Little Mill Creek near Newport and at Christina

River at Coochs Bridge (table 20). Particulate

ammonia loads tended to be oversimulated at Little Mill Creek and undersimulated at Christina

River at Coochs Bridge. The error in simulated

streamflow contributes to the overall error in simulated loads. The magnitude and sign of the percent

error in streamflow can be compared to the magnitude and percent error in load to indicate whether

water-quality concentrations for load computations are under- or oversimulated. At Little Mill

Creek near Newport, the difference between

observed and simulated streamflow ranged from

-49 to 33 percent for individual storms and was

2 percent for the total of all storms; the difference

2400 1200 2400 1200 2400 1200 2400

8 9 10

March 1998

0

1,000

200

400

600

800

STREAMFLOW, IN CUBIC FEET PER SECOND

0

0.10

0.02

0.04

0.06

0.08

PARTICULATE AMMONIA CONCENTRATION,

IN MILLIGRAM PER LITER AS N

EXPLANATION

SIMULATED STREAMFLOW

OBSERVED STREAMFLOW

SIMULATED PARTICULATE AMMONIA

OBSERVED PARTICULATE AMMONIA

2400 1200 2400 1200 2400 1200 2400

8 9 10

March 1998

0

300

100

200

STREAMFLOW, IN CUBIC FEET PER SECOND

0

0.10

0.02

0.04

0.06

0.08

PARTICULATE AMMONIA CONCENTRATION,

IN MILLIGRAM PER LITER AS N

Figure 36. Simulated and observed streamflow and

concentrations of particulate ammonia and period of

composite sample for one of the better simulated storms

in 1998 at each of the streamflow-measurement stations

01480095, Little Mill Creek near Newark, Del., and

01478000, Christina River at Coochs Bridge, Del.

LITTLE MILL CREEK NEAR NEWPORT

CHRISTINA RIVER AT COOCHS BRIDGE

PERIOD OF COMPOSITE SAMPLE
68 Simulation of Water Quality

between observed and simulated dissolved ammonia loads ranged from -57 to 421 percent for individual storms and was -31 percent for the total of

all storms; and the difference between observed

and simulated particulate ammonia loads ranged

from -65 to 201 percent for individual storms and

was 83 percent for the total of all storms. At Christina River at Coochs Bridge, the difference between

observed and simulated streamflow ranged from

-83 to 68 percent for individual storms and was

-2 percent for the total of all storms, the difference

between observed and simulated dissolved ammonia loads ranged from -35 to 5,624 percent for individual storms and was 21 percent for the total of all

storms; and the difference between observed and

simulated particulate ammonia loads ranged from

-93 to -50 percent for individual storms and was

-67 percent for the total of all storms. Using an

approach described in the section on simulation of

suspended sediment, the cumulative error in the

simulated dissolved ammonia component of load,

adjusted for the cumulative error in simulated

streamflow, is -32 percent for the Little Mill Creek

near Newport site and 23 percent for the Christina

River at Coochs Bridge site. The cumulative error

in the simulated particulate ammonia component

of load, adjusted for the cumulative error in simulated streamflow, is 81 percent for the Little Mill

Creek near Newport site and -66 percent for the

Christina River at Coochs Bridge site.

At both monitoring sites, the over- and

undersimulation of dissolved ammonia may be

related to analytical errors and errors in estimating

contributions of ammonia from point sources in

addition to those associated with ammonia from

nonpoint sources. The undersimulation of particulate ammonia may be related to errors in partitioning from dissolved to sorbed phases and to errors

in sediment transport. Using monthly or yearly

annual load criteria (Donigian and others, 1984),

the dissolved and particulate ammonia calibration

ranges from ‘fair’ to worse than ‘fair’ for individual storms.

Simulated concentrations of dissolved

ammonia under base-flow conditions were different than observed concentrations by -0.324 to

0.151 mg/L as nitrogen (N) at the two nonpointsource monitoring sites (fig. 33). The median difference between simulated and observed ammonia

concentrations for base-flow samples was about

9 percent. As noted previously, streamflow was

well simulated for all base-flow samples (fig. 26).

The errors in simulation of dissolved ammonia at

the Little Mill Creek near Newport and Christina

River at Coochs Bridge sites under base-flow conditions may be related to the lack of temporal resolution in estimated ammonia concentrations in

point-source discharges upstream and to inadequate simulation of in-stream processes that

include ammonia uptake and release by algae.

Mean hourly ammonia loads for point-source discharges were estimated from reported average

monthly ammonia values; however, hourly values

probably vary within each month. Simulated concentrations of particulate ammonia were less than

0.001 mg/L as N at both sites, except for the April

1998 value at Little Mill Creek near Newport, and

generally were less than the observed concentrations of particulate ammonia, which ranged from

0.0 to 0.03 mg/L as N.

Concentration data for grab samples collected by DNREC near two streamflow-measurement stations under a range of hydrologic

conditions also were used to evaluate the simulation of total ammonia. The Christina River sites at

Coochs Bridge and Little Mill Creek near Newport

sites are downstream from point-source discharges. As noted earlier, most of the samples were

collected under moderate or base-flow conditions.

Ammonia concentrations are not well simulated.

The median difference between simulated and

observed total ammonia concentrations was

57 percent for Christina River at Coochs Bridge

and 37 percent for Little Mill Creek near Newport.

Errors in load estimates of nitrate from point

sources and nonpoint sources and in-stream processes may contribute to overall errors in in-stream

ammonia concentrations. Errors in streamflow

simulations (fig. 37) contribute to overall error in

load simulations at the two sites. Simulated total

ammonia loads generally were within a factor of

5 or less of observed loads at Little Mill Creek near

Newport and within a factor of 10 of observed

loads at Christina River at Coochs Bridge. Ammonia tends to be oversimulated at both sites.

Overall, the nitrate and dissolved and particulate ammonia simulation under base-flow and

stormflow conditions generally appears to represent the observed patterns of ammonia concentrations in response to flow conditions and defined

land uses. Dissolved ammonia storm loads and

base-flow concentrations tend to be oversimulated

at the two monitoring sites (Little Mill Creek near

Newport and Christina River at Coochs Bridge)

that are downstream from several point-source discharges and this oversimulation may be partly
Simulation of Water Quality 69

0 0.5 0.1 0.2 0.3 0.4

OBSERVED INSTANTANEOUS TOTAL AMMONIA

CONCENTRATION, IN MILLIGRAM PER LITER AS N

0

0.5

0.1

0.2

0.3

0.4

SIMULATED HOURLY MEAN TOTAL AMMONIA

CONCENTRATION, IN MILLIGRAM PER LITER AS N

0.01 5 0.02 0.05 0.1 0.2 0.5 1 2

OBSERVED TOTAL AMMONIA LOAD,

 IN POUNDS AS NITROGEN PER HOUR

0.01

5

0.02

0.05

0.1

0.2

0.5

1

2

SIMULATED HOURLY MEAN TOTAL AMMONIA LOAD,

IN POUNDS AS NITROGEN PER HOUR

0 0.5 0.1 0.2 0.3 0.4

OBSERVED INSTANTANEOUS TOTAL AMMONIA

CONCENTRATION, IN MILLIGRAM PER LITER AS N

0

0.5

0.1

0.2

0.3

0.4

SIMULATED HOURLY MEAN TOTAL AMMONIA

CONCENTRATION, IN MILLIGRAM PER LITER AS N

0.002 5 0.010.02 0.05 0.1 0.2 0.5 1 2

OBSERVED TOTAL AMMONIA LOAD,

 IN POUNDS AS NITROGEN PER HOUR

0.002

5

0.005

0.01

0.02

0.05

0.1

0.2

0.5

1

2

SIMULATED HOURLY MEAN TOTAL AMMONIA LOAD,

IN POUNDS AS NITROGEN PER HOUR

Figure 37. Simulated hourly mean total ammonia concentrations and loads at streamflow-measurement

stations (A) 01480095, Little Mill Creek near Newport, Del., and (B) 01478000, Christina River at Coochs

Bridge, Del., and observed instantaneous total ammonia concentrations and loads at water-quality

monitoring sites (A) 106281, Little Mill Creek at Atlantic Avenue and (B) 106141, Christina River at Old

Baltimore Pike, October 1994–October 1998. (Observed loads calculated from observed concentrations

at water-quality monitoring sites and streamflow at streamflow-measurement stations. Water-quality data

from Delaware Department of Natural Resources and Environmental Control.)

A. LITTLE MILL CREEK NEAR NEWPORT B. CHRISTINA RIVER AT COOCHS BRIDGE

A. LITTLE MILL CREEK NEAR NEWPORT B. CHRISTINA RIVER AT COOCHS BRIDGE

LINE OF IDENTITY

LINE OF IDENTITY

FACTOR OF 10

FACTOR OF 5

LINE OF IDENTITY LINE OF IDENTITY
70 Simulation of Water Quality

related to inaccurate characterization of ammonia

uptake upstream of the sampling site and (or)

inadequate characterization of ammonia in discharges. Commonly, errors expressed in percent

are greater for particulate ammonia simulation

than for dissolved ammonia simulation and are

greater for the ammonia simulation than the

nitrate simulation. Of the nitrogen species simulated, nitrate represents the greatest amount and

particulate ammonia represents the least amount

of the inorganic nitrogen load. In storms, nitrate

loads are an order of magnitude greater than dissolved ammonia loads and two orders of magnitude greater than particulate ammonia loads

(table 20).

Simulated annual yields of nitrogen varied

by land use. Annual yields of nitrate and ammonia

are presented per land-use category per segment in

tables 21 and 23 and mean yields of nitrate and

ammonia for the simulation period are presented

per land-use category per segment in tables 22

and 24. For most land uses, simulated nitrate

yields generally were at least one order of magnitude greater than simulated total ammonia yields.
Simulation of Water Quality 71

Table 21. Observed annual precipitation and simulated annual nitrate yields by

land use for the three segments of the Hydrological Simulation Program–Fortran

(HSPF) model for Christina River subbasin, 1995-97

Year

Segment 1995 1996 1997 1995-97

average

Precipitation (inches) 5, 8 38.1 56.9 34.7 43.2

Simulated annual nitrate yield (pounds as nitrogen per acre per year) by land-use category1

Residential - unsewered 5 6.46 14.7 9.2 10.12

Residential - sewered 5 3.46 7.92 4.73 5.37

Urban 5 3.66 7.91 4.69 5.42

Agricultural - animal/crop 5 13.6 28.6 16.8 19.7

Agricultural - row crop 5 11.8 24.9 14.3 17.0

Agricultural - mushroom 5 16.9 36.4 21.6 25.0

Forested 5 .684 1.63 1.06 1.13

Open 5 2.39 5.34 3.14 3.62

Wetlands/water 5 .744 2.02 1.42 1.40

Undesignated 5 2.36 5.39 3.16 3.64

Impervious - residential 5 2.02 2.06 2.03 2.04

Impervious - urban 5 2.02 2.06 2.03 2.04

Simulated annual nitrate yield (pounds as nitrogen per acre per year) by land-use category1

Residential - unsewered 8 6.69 13.7 7.73 9.37

Residential - sewered 8 3.65 7.40 4.02 5.02

Urban 8 3.84 7.27 3.98 5.03

Agricultural - animal/crop 8 14.9 28.5 15.6 19.7

Agricultural - row crop 8 13.1 24.9 13.4 17.1

Agricultural - mushroom 8 17.7 34.2 18.6 23.5

Forested 8 .815 1.79 1.02 1.21

Open 8 2.47 4.98 2.69 3.38

Wetlands/water 8 .995 2.49 1.48 1.66

Undesignated 8 2.48 5.00 2.70 3.39

Impervious - residential 8 2.00 2.07 2.03 2.03

Impervious - urban 8 2.00 2.07 2.03 2.03

Precipitation (inches) 9 35.7 45.4 25.6 35.6

Simulated annual nitrate yield (pounds as nitrogen per acre per year) by land-use category1

Residential - unsewered 9 7.07 13.6 5.27 8.65

Residential - sewered 9 3.83 7.16 2.71 4.57

Urban 9 3.89 7.08 2.68 4.55

Agricultural - animal/crop 9 14.2 25.6 9.74 16.51

Agricultural - row crop 9 12.1 21.8 8.18 14.0

Agricultural - mushroom 9 17.5 32.4 12.2 20.7

Forested 9 .743 1.5 .699 .981

Open 9 2.47 4.65 1.78 2.97

Wetlands/water 9 .934 1.97 .919 1.27

Undesignated 9 2.48 4.68 1.79 2.98

Impervious - residential 9 2.01 1.97 1.94 1.97

Impervious - urban 9 2.01 1.97 1.94 1.97

1 In pervious areas, unless noted.
72 Simulation of Water Quality

Table 22. Observed annual precipitation and simulated average annual nitrate yield

by land use for pervious and impervious land areas in the three segments of the

Hydrological Simulation Program–Fortran (HSPF) model for Christina River

subbasin, 1995-97

1995-97 Average

Segment 5 Segment 8 Segment 9

Average of

all

segments

Precipitation (inches) 43.2 43.2 35.6 40.7

Simulated annual nitrate yield (pounds as nitrogen per acre per year) by land-use category1

Residential - unsewered 10.1 9.37 8.65 9.38

Residential - sewered 5.37 5.02 4.57 4.99

Urban 5.42 5.03 4.55 5.00

Agricultural - animals/crops 19.7 19.7 16.5 18.6

Agricultural - row crop 17.0 17.1 14.0 16.1

Agricultural - mushroom 25.0 23.5 20.7 23.1

Forested 1.13 1.21 .981 1.11

Open 3.62 3.38 2.97 3.32

Wetlands/water 1.40 1.66 1.27 1.44

Undesignated 3.64 3.39 2.98 3.34

Impervious - residential 2.04 2.03 1.97 2.01

Impervious - urban 2.04 2.03 1.97 2.01

1 In pervious areas, unless noted.
Simulation of Water Quality 73

Table 23. Observed annual precipitation and simulated annual total ammonia yields

by land use for the three segments of the Hydrological Simulation Program–Fortran

(HSPF) model for Christina River subbasin, 1995-97

Year

Segment 1995 1996 1997 1995-97

average

Precipitation (inches) 5, 8 38.1 56.9 34.7 43.2

Simulated annual total ammonia yield (pounds as nitrogen per acre per year) by land-use category1

Residential - unsewered 5 .082 .199 .079 .120

Residential - sewered 5 .046 .110 .043 .066

Urban 5 .066 .122 .045 .078

Agricultural - animal/crop 5 .624 1.06 .305 .663

Agricultural - row crop 5 .404 .704 .214 .441

Agricultural - mushroom 5 2.23 3.86 .901 2.33

Forested 5 .017 .042 .028 .029

Open 5 .069 .162 .074 .102

Wetlands/water 5 .012 .036 .023 .024

Undesignated 5 .069 1.63 .075 .591

Impervious - residential 5 .362 .364 .363 .363

Impervious - urban 5 .416 .42 .419 .418

Simulated annual total ammonia yield (pounds as nitrogen per acre per year) by land-use category1

Residential - unsewered 8 .091 .179 .068 .113

Residential - sewered 8 .052 .1 .038 .063

Urban 8 .074 .106 .039 .073

Agricultural - animal/crop 8 .504 .794 .231 .510

Agricultural - row crop 8 .28 .454 .147 .294

Agricultural - mushroom 8 1.55 2.39 .598 1.51

Forested 8 .021 .046 .027 .031

Open 8 .075 .148 .065 .096

Wetlands/water 8 .016 .043 .024 .028

Undesignated 8 .076 .148 .065 .096

Impervious - residential 8 .364 .352 .363 .360

Impervious - urban 8 .407 .405 .420 .411

Precipitation (inches) 9 35.7 45.4 25.6 35.6

Simulated annual total ammonia yield (pounds as nitrogen per acre per year) by land-use category1

Residential - unsewered 9 .070 .123 .041 .078

Residential - sewered 9 .197 .212 .023 .144

Urban 9 .286 .242 .023 .184

Agricultural - animal/crop 9 .603 .92 .051 .525

Agricultural - row crop 9 .589 .874 .049 .504

Agricultural - mushroom 9 .679 1.01 .173 .621

Forested 9 .02 .041 .018 .026

Open 9 .093 .107 .04 .080

Wetlands/water 9 .015 .033 .014 .021

Undesignated 9 .092 .084 .040 .072

Impervious - residential 9 .364 .352 .354 .357

Impervious - urban 9 .417 .405 .410 .411

1 In pervious areas, unless noted.
74 Simulation of Water Quality

Table 24. Observed annual precipitation and simulated average annual

total ammonia yield for pervious and impervious land areas in the

three segments of the Hydrological Simulation Program–Fortran (HSPF)

model for Christina River subbasin, 1995-97

1995-97 Average

Segment 5 Segment 8 Segment 9

Average of

all

segments

Precipitation (inches) 43.2 43.2 35.6 40.7

Average annual total ammonia yield (pounds per acre per year) by land-use category1

Residential - unsewered .120 .113 0.078 .109

Residential - sewered .066 .063 .144 .063

Urban .078 .073 .184 .072

Agricultural - animals/crops .663 .510 .525 .504

Agricultural - row crop .441 .294 .504 .324

Agricultural - mushroom 2.33 1.51 .621 1.73

Forested .029 .031 .026 .030

Open .102 .096 .080 .094

Wetlands/water .024 .028 .021 .025

Undesignated .591 .096 .072 .257

Impervious - residential .363 .360 .357 .360

Impervious - urban .418 .411 .411 .413

1 In pervious areas, unless noted.
Simulation of Water Quality 75

Phosphorus

The model was used to simulate inorganic

phosphorus, where dissolved and adsorbed orthophosphate are considered to be the principal dissolved and particulate inorganic phosphorus

species. Phosphorus loads from point and nonpoint sources are included in the simulation. Loads

from point-source discharges were estimated from

reported monthly average values for input on an

hourly time step to the model. For nonpoint

sources, dissolved and particulate phosphorus

were estimated at fixed concentrations in sediment

(soil), interflow, and ground water that differed by

land use. Phosphorus was assumed to be transported in dissolved and adsorbed forms from the

land surface and in the stream channel. For 1998

data collected at the Christina River at Coochs

Bridge and Little Mill Creek near Newport nonpoint-source monitoring stations under a range of

flow conditions, dissolved orthophosphate represented on average about 30 to 35 percent of total

phosphorus.

Water-quality data from the nonpoint-source

monitoring stations, Little Mill Creek near Newport and Christina River at Coochs Bridge, were

used to assess the calibration of dissolved and particulate (adsorbed) orthophosphate. Observed concentrations of particulate orthophosphate were

estimated by subtracting concentrations of dissolved phosphorus from concentrations of total

phosphorus and assuming the difference was particulate orthophosphate.

Simulated and observed concentrations of

dissolved and particulate orthophosphate are

shown in figures 38 and 39 for one of the better

simulated storms of the six storms sampled at each

of the nonpoint-source monitoring sites, Little Mill

Creek near Newport and Christina River at Coochs

Bridge. Simulated water quality for all storms at

both sites is shown in Appendix 2. Samples from

the October 1998 storm were not analyzed for total

phosphorus and therefore particulate phosphorus

concentrations could not be estimated. Observed

concentrations of dissolved and particulate orthophosphate generally appeared to increase as

streamflow increased during the March 1998 storm

(figs. 38 and 39). This general pattern of observed

dissolved and particulate orthophosphate concentrations during storms appears to be simulated by

the model for most storms (Appendix 2).

0

1,000

200

400

600

800

STREAMFLOW, IN CUBIC FEET PER SECOND

0

0.5

0.1

0.2

0.3

0.4

DISSOLVED ORTHOPHOSPHATE CONCENTRATION, IN MILLIGRAM PER LITER AS P

2400 1200 2400 1200 2400 1200 2400

8 9 10

MARCH 1998

EXPLANATION

SIMULATED STREAMFLOW

OBSERVED STREAMFLOW

SIMULATED DISSOLVED ORTHOPHOSPHATE

OBSERVED DISSOLVED ORTHOPHOSPHATE

Figure 38. Simulated and observed streamflow and

concentrations of dissolved orthophosphate and period of

composite sample for one of the better simulated storms

in 1998 at each of the streamflow-measurement stations,

01480095, Little Mill Creek near Newark, Del., and

01478000, Christina River at Coochs Bridge, Del.

CHRISTINA RIVER AT COOCHS BRIDGE

2400 1200 2400 1200 2400 1200 2400

8 9 10

March 1998

0

300

100

200

STREAMFLOW, IN CUBIC FEET PER SECOND

0

0.10

0.02

0.04

0.06

0.08

DISSOLVED ORTHOPHOSPHATE CONCENTRATION, IN MILLIGRAM PER LITER AS P

LITTLE MILL CREEK NEAR NEWPORT

PERIOD OF COMPOSITE SAMPLE
76 Simulation of Water Quality

Data from composite stormflow samples collected in 1998 were used in the calculation of loads

of dissolved orthophosphate and particulate orthophosphate. Calculated loads served as the

observed values in the evaluation of overall phosphorus transport during storms. Simulated and

observed streamflow and loads of dissolved and

particulate orthophosphate for storm events occurring in 1998 are presented in table 25. Observed

loads of particulate orthophosphate commonly

were greater than observed loads of dissolved

orthophosphate. For one small storm in May 1998,

dissolved orthophosphate loads were greater than

particulate orthophosphate loads. Dissolved and

particulate orthophosphate loads tended to be

undersimulated when flow was undersimulated,

with the exception of the March 1998 storm.

For the sampled storm periods, dissolved

and particulate orthophosphate loads were underand oversimulated at Little Mill Creek near Newport and at Christina River at Coochs Bridge. The

error in simulated streamflow contributes to the

overall error in simulated loads. The magnitude

and sign of the percent error in streamflow can be

compared to the magnitude and percent error in

load to indicate whether water-quality concentrations for load computations are under- or oversimulated. At Little Mill Creek near Newport, the

difference between observed and simulated

streamflow ranged from -56 to 43 percent for individual storms and was 3 percent for the total of all

storms; the difference between observed and simulated dissolved orthophosphate loads ranged from

-82 to 168 percent for individual storms and was

-51 percent for the total of all storms; and the difference between observed and simulated particulate orthophosphate loads ranged from -86 to

256 percent for individual storms and was -62 percent for the total of all storms (table 25). At Christina River at Coochs Bridge, the difference between

observed and simulated streamflow ranged from

-83 to 68 percent for individual storms and was

-2 percent for the total of all storms; the difference

between observed and simulated dissolved orthophosphate loads ranged from -72 to 365 percent for

individual storms and was -34 percent for the total

of all storms; and the difference between observed

and simulated particulate orthophosphate loads

ranged from -86 to 46 percent for individual storms

and was -41 percent for the total of all storms.

Using an approach described in the section on simulation of suspended sediment, the cumulative

error in the simulated dissolved orthophosphate

2400 1200 2400 1200 2400 1200 2400

8 9 10

March 1998

0

1,000

200

400

600

800

STREAMFLOW, IN CUBIC FEET PER SECOND

0

0.8

0.2

0.4

0.6

PARTICULATE ORTHOPHOSPHATE CONCENTRATION, IN MILLIGRAMS PER LITER AS P

EXPLANATION

SIMULATED STREAMFLOW

OBSERVED STREAMFLOW

SIMULATED PARTICULATE ORTHOPHOSPHATE

OBSERVED PARTICULATE PHOSPHORUS

2400 1200 2400 1200 2400 1200 2400

8 9 10

March 1998

0

300

100

200

STREAMFLOW, IN CUBIC FEET PER SECOND

0

0.8

0.2

0.4

0.6

PARTICULATE ORTHOPHOSPHATE CONCENTRATION, IN MILLIGRAMS PER LITER AS P

Figure 39. Simulated and observed streamflow and

concentrations of particulate orthophosphate and period

of composite sample for one of the better simulated

storms in 1998 at each of the streamflow-measurement

stations 01480095, Little Mill Creek near Newark, Del.,

and 01478000, Christina River at Coochs Bridge, Del.

LITTLE MILL CREEK NEAR NEWPORT

CHRISTINA RIVER AT COOCHS BRIDGE

PERIOD OF COMPOSITE SAMPLE
Simulation of Water Quality 77

Table 25. Simulated and observed streamflow and loads of dissolved and particulate orthophosphate for storms

sampled in 1998 at the nonpoint-source monitoring sites 01480095, Little Mill Creek near Newport, Del., and

01478000, Christina River at Coochs Bridge, Del.

[ft3/s, cubic feet per second; Sim., simulated; Obs., observed; diff., difference; na, not applicable; nd, not done]

Dates of storm

sampling

Peak

flow1

(ft3/s)

Streamflow

(millions of cubic feet)

Dissolved

orthophosphate load

(pounds as phosphorus)

Particulate

orthophosphate load

(pounds as phosphorus)

Sim. Obs. Percent

diff.2 Sim. Obs. Percentdiff.2 Sim. Obs. Percentdiff.2

Little Mill Creek near Newport, Del.

February 4-5 29.1 1.37 2.06 -32 5.53 2.06 168 14.3 4.00 256

March 8-9 132 4.80 4.99 -4 11.2 8.52 32 15.2 82.3 -82

May 1-2 21.3 .44 1.00 -56 6.25 7.67 -18 .35 2.52 -86

June 11-12 264 5.78 4.94 17 12.1 69.3 -82 31.9 112 -72

July 8-9 156 3.28 2.76 19 8.03 5.77 39 34.5 53.6 -36

October 8-9 41.6 1.87 1.31 43 4.52 3.47 30 na nd na

Total - all storms 17.5 17.1 3 47.7 96.8 -51 96.1 255 -62

Christina River at Coochs Bridge, Del.

March 8-9 747 21.08 22.10 -5 102 204 -50 286 512 -44

May 1-3 45.4 3.60 2.14 68 7.82 2.02 286 .54 3.91 -86

June 11-13 228 12.58 10.53 19 37.1 17.3 114 70.0 47.9 46

July 8-9 206 .86 5.13 -83 2.08 7.46 -72 10.2 57.1 -82

October 8-9 66.5 2.58 1.68 54 5.43 1.16 365 na nd na

Total - all storms 40.69 41.57 -2 155 232 -33 367 621 -41

1 Peak mean hourly discharge during period of composite sampling.

2 100 x (observed-simulated)/observed.
78 Simulation of Water Quality

component of load, adjusted for the cumulative

error in simulated streamflow, is -52 percent for the

Little Mill Creek near Newport site and 32 percent

for the Christina River at Coochs Bridge site. The

cumulative error in the simulated particulate

orthophosphate component of load, adjusted for

the cumulative error in simulated streamflow, is

-63 percent for the Little Mill Creek near Newport

site and -40 percent for the Christina River at

Coochs Bridge site.

At both monitoring sites, some errors may be

associated with estimated contributions of phosphorus from point sources in addition to those

associated with simulated orthophosphate from

nonpoint sources. The greater undersimulation of

particulate orthophosphate compared to dissolved

orthophosphate may be related to errors in partitioning from dissolved to sorbed phases and to

errors in sediment transport. Using monthly or

yearly annual load criteria (Donigian and others,

1984), the dissolved and particulate orthophosphate calibration ranges from ‘good’ to worse than

‘fair’ for individual storm loads and ‘fair’ to worse

than ‘fair’ for the cumulative storms loads.

Simulated concentrations of dissolved orthophosphate under base-flow conditions in 1998 generally were greater than or similar to observed

concentrations at the nonpoint-source monitoring

sites Christina River at Coochs Bridge and Little

Mill Creek near Newport (fig. 40). The difference

between observed and simulated dissolved orthophosphate for base-flow conditions was greater for

samples collected at Little Mill Creek near Newport than for samples collected at Christina River

at Coochs Bridge, and the median percent difference for all samples was about 110 percent. As

noted previously, streamflow was well simulated

for all base-flow samples (fig. 26). Simulated concentrations of particulate orthophosphate under

base-flow conditions generally were similar or less

than observed concentrations, except for the April

1998 value at Little Mill Creek near Newport,

which was oversimulated due to probable errors in

storm simulation prior to that sample. The median

difference between observed and simulated particulate orthophosphate for samples collected under

base-flow conditions at both sites was -48 percent

(low).

0 0.10 0.02 0.04 0.06 0.08

OBSERVED DISSOLVED ORTHOPHOSPHATE

CONCENTRATION, IN MILLIGRAM PER LITER AS P

0

0.10

0.02

0.04

0.06

0.08

SIMULATED DISSOLVED ORTHOPHOSPHATE

CONCENTRATION, IN MILLIGRAM PER LITER AS P

EXPLANATION

LITTLE MILL CREEK NEAR NEWPORT

CHRISTINA RIVER AT COOCHS BRIDGE

0 0.15 0.05 0.10

OBSERVED PARTICULATE ORTHOPHOSPHATE

CONCENTRATION, IN MILLIGRAM PER LITER AS P

0

0.15

0.05

0.10

SIMULATED PARTICULATE ORTHOPHOSPHATE

CONCENTRATION, IN MILLIGRAM PER LITER AS P

Figure 40. Simulated and observed concentrations of

(A) dissolved orthophosphate and (B) particulate

orthophosphate during base-flow conditions in 1998 at

streamflow-measurement stations 01480095, Little Mill

Creek near Newport, Del., and 01478000, Christina

River at Coochs Bridge, Del.

LINE OF IDENTITY

LINE OF IDENTITY

A

B
Simulation of Water Quality 79

Data collected by DNREC near two streamflow-measurement stations under a range of

hydrologic conditions also were used to evaluate

the simulation of dissolved orthophosphate. Both

of the sites are downstream of point-source discharges. As noted earlier, most of the samples were

collected under moderate or base-flow conditions.

Dissolved orthophosphate concentrations generally were oversimulated at both sites (fig. 41). The

median difference between simulated and

observed dissolved orthophosphate concentrations

was 380 percent for Christina River at Coochs

Bridge and 110 percent for Little Mill Creek near

Newport. Errors in load estimates of dissolved

orthophosphate from point sources and nonpoint

sources and in-stream processes may contribute to

overall errors in in-stream orthophosphate concentrations. Simulated dissolved orthophosphate

loads generally were within a factor of 5 or less of

observed loads at Little Mill Creek near Newport

and within a factor of 10 of observed loads at

Christina River at Coochs Bridge.

Overall, the dissolved and particulate orthophosphate simulation under base flow and stormflow conditions generally appears to represent the

observed patterns of phosphorus concentrations in

response to flow conditions and defined land uses.

In most storms, observed particulate orthophosphate loads commonly were from 2 to 10 times

greater than observed dissolved orthophosphate

loads (table 25). Observed orthophosphate loads

generally were greater than simulated orthophosphate loads in stormflow at the two nonpointsource monitoring sites, and appeared to be greater

than simulated loads for moderate or base-flow

conditions as determined by state monitoring data

collected nearby.

Simulated annual yields of phosphorus varied by land use. Simulated yields of total orthophosphate (dissolved plus adsorbed or particulate

orthophosphate) are presented per land-use category per segment per year in table 26 and mean

yields of total orthophosphate for the simulation

period are presented per land-use category per

segment in table 27.

Sensitivity Analysis

Sensitivity analyses for the water-quality

component of the HSPF model for the Christina

River subbasin were not done for the Christina

River subbasin model. Results of analyses done for

the other subbasins in the Christina River Basin

indicate that the model sensitivities to changes in

selected parameters for the Christina River subbasin model should be similar to model sensitivities

to changes in these parameters for the other models. General results of the sensitivity analyses for

the other subbasins are discussed below.

Calibration of water temperature is specified

by 13 parameters: 5 are for pervious land surfaces, 2 are for impervious land surfaces, and 6 are

for stream reaches. For water-temperature simulation, the model is more sensitive to parameters in

the reach modules than parameters in pervious

and impervious modules. Water temperature in a

reach is modeled as a function of the variables:

upstream flow and land surface inflow temperatures, air temperature, and various radiation, conduction, and convection gains or losses. Of these

variables, radiation, conduction, and convection

gains and losses have calibration parameters.

Although no formal sensitivity analysis was done

for parameters affecting water temperature,

through the calibration process, simulated water

temperatures were found to be sensitive most to

the parameters CFSAEX, the solar radiation correction factor, and KCOND, the conduction-convection coefficient. Daily high temperatures are

affected by CFSAEX and nighttime low temperatures by KCOND. In combination, CFSAEX and

KCOND also influence daily mean water temperature.

The simulated sediment yield from pervious

and impervious land areas is dependent on parameters affecting soil detachment, soil scour, and soil

or sediment washoff and is sensitive to parameters

affecting soil detachment (KRER, JRER), soil

washoff (KSER, JSER), and soil scour processes

(KGER, JGER) for pervious land surfaces, and solids build up (ACCSDP, REMDSP) and washoff

processes for impervious land surfaces (KEIM,

JEIM). Sediment washoff or transport capacity is

dependent on surface runoff (SURO) and, therefore, the hydrologic component of the simulation.

In addition, calibration of suspended sediment in

the stream channel is sensitive to parameters controlling shear stress regimes (TAUD, TAUS) that

determine deposition on and scour of the channel

bottom.
80 Simulation of Water Quality

0 0.20 0.05 0.10 0.15

OBSERVED INSTANTANEOUS DISSOLVED ORTHOPHOSPHATE CONCENTRATION, IN MILLIGRAM PER LITER AS P

0

0.20

0.05

0.10

0.15

SIMULATED HOURLY MEAN DISSOLVED ORTHOPHOSPHATE

CONCENTRATION, IN MILLIGRAM PER LITER AS P

0.001 1 0.005 0.01 0.02 0.05 0.1 0.2 0.5

OBSERVED DISSOLVED ORTHOPHOSPHATE

LOAD, IN POUNDS AS PHOSPHORUS PER HOUR

0.001

1

0.002

0.005

0.01

0.02

0.05

0.1

0.2

0.5

SIMULATED HOURLY MEAN DISSOLVED ORTHOPHOSPHATE

LOAD, IN POUNDS AS PHOSPHORUS PER HOUR

0 0.20 0.05 0.10 0.15

OBSERVED INSTANTANEOUS DISSOLVED ORTHOPHOSPHATE CONCENTRATION, IN MILLIGRAM PER LITER AS P

0

0.20

0.05

0.10

0.15

SIMULATED HOURLY MEAN DISSOLVED ORTHOPHOSPHATE

CONCENTRATION, IN MILLIGRAM PER LITER AS P

0.002 2 0.005 0.01 0.02 0.05 0.1 0.2 0.5 1

OBSERVED DISSOLVED ORTHOPHOSPHATE

LOAD, IN POUNDS AS PHOSPHORUS PER HOUR

0.002

2

0.005

0.01

0.02

0.05

0.1

0.2

0.5

1

SIMULATED HOURLY MEAN DISSOLVED ORTHOPHOSPHATE

LOAD, IN POUNDS AS PHOSPHORUS PER HOUR

Figure 41. Simulated hourly mean dissolved orthophosphate concentrations and loads at streamflowmeasurement stations (A) 01480095, Little Mill Creek near Newport, Del., and (B) 01478000, Christina River

at Coochs Bridge, Del., and observed instantaneous dissolved orthophosphate concentrations and loads at

water-quality monitoring sites (A) 106281, Little Mill Creek at Atlantic Avenue and (B) 106141, Christina River

at Old Baltimore Pike, October 1994–October 1998. (Observed loads calculated from observed

concentrations at water-quality monitoring sites and streamflow at streamflow-measurement stations.

Water-quality data from Delaware Department of Natural Resources and Environmental Control.)

LINE OF IDENTITY LINE OF IDENTITY

LINE OF IDENTITY

LINE OF IDENTITY

FACTOR OF 5

FACTOR OF 10

A

A

B

B
Simulation of Water Quality 81

Table 26. Observed annual precipitation and simulated annual total (dissolved plus adsorbed) orthophosphate

yields by land use for the three segments of the Hydrological Simulation Program–Fortran (HSPF) model for

Christina River subbasin, 1995-97

Year

Segment 1995 1996 1997 1995-97

average

Precipitation (inches) 5, 8 38.1 56.9 34.7 43.2

Simulated annual total orthophosphate yield (pounds as phosphorus per acre per year) by land-use category1

Residential - unsewered 5 .13 .324 .085 .180

Residential - sewered 5 .16 .399 .092 .217

Urban 5 .279 .471 .104 .285

Agricultural - animal/crop 5 5.8 9.62 2.42 5.947

Agricultural - row crop 5 5.71 9.58 2.34 5.877

Agricultural - mushroom 5 19.8 33.6 6.96 20.120

Forested 5 .0092 .023 .014 .015

Open 5 .187 .471 .065 .241

Wetlands/water 5 .006 .018 .012 .012

Undesignated 5 .185 .469 .064 .239

Impervious - residential 5 .29 .313 .298 .300

Impervious - urban 5 .771 .805 .796 .791

Simulated annual total orthophosphate yield (pounds as phosphorus per acre per year) by land-use category1

Residential - unsewered 8 .149 .287 .076 .171

Residential - sewered 8 .191 .358 .085 .211

Urban 8 .323 .397 .092 .271

Agricultural - animal/crop 8 6.04 9.23 2.26 5.843

Agricultural - row crop 8 6 9.16 2.17 5.777

Agricultural - mushroom 8 21.3 32 6.98 20.093

Forested 8 .011 .025 .014 .017

Open 8 .223 .408 .064 .232

Wetlands/water 8 .008 .022 .012 .014

Undesignated 8 .223 .408 .064 .232

Impervious - residential 8 .288 .314 .298 .300

Impervious - urban 8 .77 .804 .797 .790

Precipitation (inches) 9 35.7 45.4 25.6 35.6

Simulated annual total orthophosphate yield (pounds as phosphorus per acre per year) by land-use category1

Residential - unsewered 9 .091 .144 .038 .091

Residential - sewered 9 .165 .219 .04 .141

Urban 9 .213 .231 .042 .162

Agricultural - animal/crop 9 2.46 3.8 .117 2.126

Agricultural - row crop 9 2.41 3.62 .111 2.047

Agricultural - mushroom 9 9.55 14.3 .407 8.086

Forested 9 .01 .02 .009 .013

Open 9 .09 .119 .016 .075

Wetlands/water 9 .008 .016 .007 .010

Undesignated 9 .09 .117 .016 .074

Impervious - residential 9 .28 .284 .272 .279

Impervious - urban 9 .757 .743 .771 .757

1 In pervious areas, unless noted.
82 Simulation of Water Quality

Table 27. Observed annual precipitation and simulated average annual total orthophosphate yield

by land use for pervious and impervious land areas in the three segments of the Hydrological

Simulation Program–Fortran (HSPF) model for Christina River subbasin, 1995-97

 1995-97 Average

Segment 5 Segment 8 Segment 9 Average of all

segments

Precipitation (inches) 43.2 43.2 35.6 40.7

Simulated annual total orthophosphate yield (pounds as phosphorus per acre per year) by land-use category1

Residential - unsewered .180 .171 .091 .147

Residential - sewered .217 .211 .141 .190

Urban .285 .271 .162 .239

Agricultural - animals/crops 5.95 5.84 2.13 4.64

Agricultural - row crop 5.88 5.78 2.05 4.57

Agricultural - mushroom 20.1 20.1 8.09 16.1

Forested .015 .017 .013 .015

Open .241 .232 .075 .183

Wetlands/water .012 .014 .010 .012

Undesignated .239 .232 .074 .182

Impervious - residential .300 .300 .279 .293

Impervious - urban .791 .790 .757 .779

1 In pervious areas, unless noted.
Simulation of Water Quality 83

The simulated yields of nitrate, ammonia,

and orthophosphate from pervious land areas are

dependent on parameters affecting sediment yield

except those controlling sediment scour processes.

Nitrate yields are less affected than ammonia and

phosphorus by changes in sediment yield because

the model, as set up, simulates surface-runoff and

ground-water transport of these constituents from

land areas to streams in different relative amounts.

The largest amounts of nitrate from land areas

enter the streams through ground-water discharge

(AGWO). The largest amounts of ammonia and

orthophosphate from most land areas enter

streams with sediment in surface runoff (SURO).

The difference in transport mechanisms is supported by studies that indicate nitrate commonly

leaches from soils to ground water more readily

than ammonia and phosphorus (Guo and others,

2001) and that the majority of nitrate and phosphorus yields in nearby basins are in base flow and

stormflow, respectively (Lietman, 1997).

The simulated yields of nitrate, ammonia,

and phosphate from pervious and impervious land

areas also are dependent on parameters affecting

concentrations of the constituent on detached soil

or sediment (POTFW) and in interflow (IFLWCONC) and ground water (GRND-CONC). The

parameters affecting interflow and ground-water

concentrations affect nitrate yields more than

yields of ammonia and orthophosphate because of

differences in the main mechanisms that deliver

these nutrients to the streams. Consequently,

changes to parameters affecting concentrations of

nutrients on detached soil (POTFW) affect yields of

ammonia and orthophosphate more than nitrate.

Model Limitations

The simulation of water-quality constituent

concentrations and loads is dependent on the output of the hydrologic portion of the model. Thus

the accuracy of the water-quality simulations will

be limited by the hydrologic model. In addition,

the water-quality calibration was based on relatively few available observed water-quality data;

therefore, compared to a calibration with many

water-quality data points, greater uncertainty is

associated with this simulation of water quality

and assessment of the model performance is more

difficult.

The water-quality simulation used model

parameters that were obtained from calibration of

models in adjacent basins of various sizes and may

not be wholly representative of land uses in the

Christina River subbasin. Simulation of concentrations of suspended sediment, nitrate, ammonia,

and phosphorus for individual storms or short

periods of time may not be well simulated by the

model because of hydrologic limitations related to

accuracy of rainfall data. The timing and intensity

of rainfall affect detachment processes for soil and

soil-related constituents and transport of the solids

from land to streams. The simulation of sediment

was calibrated using measured concentrations of

suspended solids in samples collected at one point

in the stream. However, these point samples may

not accurately represent mean suspended-sediment concentrations for the entire cross section in

stream reaches that are not well mixed. Simulation

of water quality may be less accurate for ungaged

areas of the subbasin downstream of the streamflow-measurement station used for calibration

(01478000 Christina River at Coochs Bridge)

because of unknown spatial differences in hydrologic response. For example, most of the ungaged

areas in the subbasin are underlain by soils developed on the Coastal Plain with substantially different infiltration and storage characteristics from the

Piedmont area. Also, much of the ungaged area

has a shallow water table and drains directly to

tidal sections of the Christina River.

The simulation of the nutrients, including

nitrogen and phosphorus, also included the biological processes of algal plankton and benthic

algal nutrient uptake and release but not the role of

zooplankton. Thus the magnitude of diurnal fluctuations in concentrations of dissolved oxygen due

to processes of in-stream photosynthesis and respiration may not be fully characterized by the simulation. The simulation of in-stream nutrient

concentrations is further affected by the quality

and quantity of information about nutrients in discharge from point sources. For example, although

the model is run on an hourly time step, data on

point-source discharges generally are available as

monthly mean values for ammonia, and contributions of phosphorus. Nitrate discharges are extrapolated from reported ammonia. The model, as

configured, is better used to estimate loads of nonpoint-source nutrients from land areas than to predict concentrations after considerable in-stream

transport and residence time at downstream sites.

The simulation of particulate orthophosphate was calibrated to an estimated value, calculated as observed total phosphorus minus

observed dissolved phosphorus. This difference,
84 Overview of Christina River Basin Models

however, may include forms of phosphorus other

than orthophosphate. Because the model as configured only simulates orthophosphate, particulate

phosphorus that includes other forms of phosphorus may be undersimulated.

Overall, the model represents streamflow

and general water-quality conditions in the Christina River Basin to a reasonable degree. Over long

periods of time (months to years) the model

appears to be fairly accurate for streamflow. However short-term simulations and simulations of

storms are less accurate. The sparseness of waterquality data renders rigorous evaluation of the

long-term and short-term performance of the

water-quality component of the model simulation

difficult. Nevertheless, it is expected that the simulation of water quality is more accurate over long

periods than short periods, such as individual

storms. Therefore, given the model structure,

assumptions, and approach, the best applications

of the model are long-term predictions of nonpoint-source contributions to water quality.

OVERVIEW OF CHRISTINA RIVER

BASIN MODELS

Separate HSPF models were developed for

each of the four main subbasins of the Christina

River Basin, including Brandywine Creek, White

Clay Creek, Red Clay Creek (Senior and Koerkle

2003a; 2003b; 2003c), and the Christina River subbasin itself (fig. 1). The HSPF models for the main

subbasins of the Christina River Basin were developed as part of a basin-wide effort to simulate nonpoint-source contributions of suspended sediment

and nutrients. Data for calibration was collected at

sites throughout the Christina River Basin and

included at least one site in each main subbasin in

the nonpoint-source monitoring in 1998. The models can be used separately for each of the subbasins

and for the Christina River Basin as whole.

Calibration

Calibration of the HSPF model for each subbasin followed slightly different approaches based

on the location and number of streamflow-measurement stations and water-quality monitoring

sites in each subbasin. In most subbasins, the

hydrologic calibration was done in a downstream

order. For the Brandywine Creek model, primary

hydrologic calibration was done using data from

seven streamflow-measurement stations on the

West Branch, East Branch, and main stem Brandywine Creek and less emphasis was placed on the

hydrologic calibration of the four small tributary

subbasins with nonpoint-source monitoring sites.

For the White Clay Creek model, the data used for

hydrologic calibration included streamflow measurements from a station on the main stem of Red

Clay Creek in an area adjacent to the White Clay

Creek subbasin and streamflow measurements

from three stations on the main stem of White Clay

Creek, with some calibration adjustments using

data from a headwaters tributary subbasin (Trout

Run). This approach to calibration of the Brandywine Creek and White Clay Creek models resulted

in a more satisfactory hydrologic calibration of the

overall basin than of smaller subbasin areas less

than 10 to 20 mi2. Similar hydrologic calibration

results would be expected for the Red Clay Creek

model. For the Red Clay Creek model, no small

tributary subbasins had streamflow-measurement

stations and the hydrologic calibration was done

using data from three streamflow-measurement

stations on the main stem of Red Clay Creek. For

the Christina River subbasin model, much of the

stream is tidal and the hydrologic-calibration data

came from streamflow-measurement stations on

the main stem and a tributary that drain relatively

small areas (less than 25 mi2) in separate parts of

the Christina River subbasin. The overall accuracy

of the hydrologic calibrations at the two sites in the

Christina River subbasin are similar.

Water-quality data from the small subbasins

with nonpoint-source monitoring sites, which are

predominantly of one major land use, were used to

calibrate the water-quality component of landbased nonpoint-source contributions. Five of the

seven small subbasins with nonpoint-source monitoring sites were in the Brandywine Creek drainage area, one in the White Clay Creek drainage

area, and one (Little Mill Creek, described in this

report) in the Christina River drainage area. The

five nonpoint-source monitoring sites in the Brandywine Creek subbasin were located to assess

water quality associated with two types of agricultural (row crop and mixed animal/crop), two

types of residential (sewered and septic systems),

and forested land uses. Model water-quality

parameters from these five land uses were transferred with minor modifications to models for

White Clay Creek, Red Clay Creek, and Christina

River subbasins. Model water-quality parameters

from the agricultural land use of mushroom-growing were developed for the White Clay Creek

model and transferred to the Red Clay Creek
Overview of Christina River Basin Models 85

model. Despite the limitations of the hydrologic

calibration of the small subbasins with nonpointmonitoring sites in the Brandywine Creek and

White Clay Creek models, the transfer of the

water-quality model parameters appeared to result

in reasonable water-quality simulations in the

other subbasin models.

Simulated Sediment and Nutrient Yields

Simulated yields of suspended sediment and

nutrients differed by land use and in some cases by

soil type. In general, in each of the modeled subbasins, Brandywine Creek, White Clay Creek, Red

Clay Creek, and the Christina River itself, simulated suspended-sediment yields were larger from

agricultural land than from other land uses. Simulated average annual sediment and nutrient yields

for 1995-97 from the various land uses in the four

subbasins are presented in tables 28-31. Yields

tended to increase in relation to increases in precipitation because ground-water discharge and surface runoff commonly were greater in wet years

than in dry years. Average annual precipitation for

1995-97 was greatest in the Brandywine Creek subbasin and least in the Christina River subbasin,

indicating a spatial trend of a north to south

decrease in precipitation for the 1995-97 period.

Table 28. Observed annual precipitation and simulated average annual sediment

yield by land use for pervious and impervious land areas in segments of

Hydrological Simulation Program–Fortran (HSPF) model for the Brandywine Creek,

Red Clay Creek, White Clay Creek, and Christina River subbasins, 1995-97

Subbasin average, 1995-97

Brandywine

Creek

average of

four

segments

White Clay

Creek

average of

three

segments

Red Clay

Creek

average of

three

segments

Christina

River

average of

three

segments

Precipitation (inches) 50.51 45.91 45.86 40.68

Simulated average annual sediment yield (tons per acre per year) by land-use category1

Residential - unsewered .218 .192 .232 .146

Residential - sewered .261 .271 .287 .222

Urban .418 .404 .381 .340

Agricultural - animals/crops 1.67 1.76 1.88 1.18

Agricultural - row crop 1.67 1.69 1.83 1.16

Agricultural - mushroom 1.23 2.39 2.10 1.18

Forested .067 .047 .060 .041

Open .217 .259 .263 .201

Wetlands/water .050 .005 .007 .003

Undesignated .226 .260 .258 .198

Impervious - residential .114 .201 .198 .114

Impervious - urban 1.124 .795 .785 .665

1 In pervious areas, unless noted.
86 Overview of Christina River Basin Models

Table 29. Observed annual precipitation and simulated average annual nitrate yield by land use for

pervious and impervious land areas in segments of Hydrological Simulation Program–Fortran

(HSPF) model for the Brandywine Creek, Red Clay Creek, White Clay Creek, and Christina

River subbasins, 1995-97

Subbasin average, 1995-97

Brandywine

Creek

average of four

segments

White Clay

Creek

average of

three

segments

Red Clay

Creek

average of

three

segments

Christina

River

average of

three

segments

Precipitation (inches) 50.51 45.91 45.86 40.68

Simulated average annual nitrate yield (pounds as nitrogen per acre per year) by land-use category1

Residential - unsewered 17.25 14.28 12.66 9.38

Residential - sewered 9.02 7.55 6.73 4.99

Urban 9.07 7.62 6.66 5.00

Agricultural - animals/crops 32.14 27.2 24.3 18.6

Agricultural - row crop 29.46 24.5 19.0 16.1

Agricultural - mushroom 40.81 33.1 29.2 23.1

Forested 1.80 1.47 1.39 1.11

Open 6.46 5.08 4.62 3.32

Wetlands/water 1.58 1.78 1.53 1.44

Undesignated 6.16 5.09 4.62 3.39

Impervious - residential 2.07 2.04 2.03 2.01

Impervious - urban 2.07 2.04 2.03 2.01

1 In pervious areas, unless noted.
Overview of Christina River Basin Models 87

Table 30. Observed annual precipitation and simulated average annual total ammonia yield by land

use for pervious and impervious land areas in segments of Hydrological Simulation Program–Fortran

(HSPF) model for the Brandywine Creek, Red Clay Creek, White Clay Creek, and Christina River

subbasins, 1995-97

Subbasin average, 1995-97

Brandywine

Creek

average of four

segments

White Clay

Creekaverage

of three

segments

Red Clay

Creekaverage

of three

segments

Christina

River average

of three

segments

Precipitation (inches) 50.51 45.91 45.86 40.68

Simulated average annual total ammonia yield (pounds as nitrogen per acre per year) by land-use category1

Residential - unsewered .172 .152 .149 .101

Residential - sewered .108 .085 .080 .088

Urban .102 .095 .086 .107

Agricultural - animals/crops .835 .758 .720 .508

Agricultural - row crop .676 .584 .470 .391

Agricultural - mushroom .435 3.40 2.97 1.40

Forested .045 .040 .037 .028

Open .157 .134 .124 .087

Wetlands/water .025 .030 .026 .023

Undesignated .155 .134 .124 .248

Impervious - residential .361 .372 .371 .360

Impervious - urban .499 .432 .430 .413

1 In pervious areas, unless noted.
88 Overview of Christina River Basin Models

Table 31. Observed annual precipitation and simulated average annual total orthophosphate yield by land

use for pervious and impervious land areas in segments of Hydrological Simulation Program–Fortran

(HSPF) model for the Brandywine Creek, Red Clay Creek, White Clay Creek, and Christina River subbasins,

1995-97

Subbasin average, 1995-97

Brandywine

Creek average of

four segments

White Clay Creek

average of three

segments

Red Clay Creek

average of three

segments

Christina River

average of three

segments

Precipitation (inches) 50.51 45.91 45.86 40.68

Simulated average annual total orthophosphate yield (pounds as phosphorus per acre per year) by land-use category1

Residential - unsewered .210 .210 .222 .147

Residential - sewered .215 .252 .251 .190

Urban .272 .312 .291 .239

Agricultural - animals/crops 10.5 6.99 7.50 4.64

Agricultural - row crop 9.10 6.71 7.31 4.57

Agricultural - mushroom 14.8 32.6 29.0 16.1

Forested .029 .020 .029 .015

Open .256 .245 .245 .183

Wetlands/water .120 .015 .013 .012

Undesignated .263 .245 .241 .182

Impervious - residential .367 .401 .400 .293

Impervious - urban 1.88 .912 .903 .779

1 In pervious areas, unless noted.
Overview of Christina River Basin Models 89

Model Applications

The HSPF model for the Christina River was

developed to assist in the assessment of suspended

sediment and nutrient loads from nonpoint

sources to streams. The model load estimates may

be used as part of an ongoing total maximum daily

load (TMDL) assessment for the Christina River

Basin to indicate the possible location and magnitude of load reductions that might be needed to

maintain or improve water quality where

impaired. These load estimates are based on the

land-use conditions during the period of calibration and do not reflect the effects of best management practices put in place after 1998.

The models can be used to estimate loads

from individual basins for the purposes of evaluating relative and absolute contributions of suspended sediment, nitrogen, and phosphorus. This

information may be helpful in assessing areas that

appear to generate elevated nonpoint-source loads

of these constituents. For example, simulated total

loads and loads per acre in 1995 for selected headwater areas are listed for the Brandywine Creek,

White Clay Creek, and Red Clay Creek subbasins

(Senior and Koerkle, 2003a; 2003b; 2003c). Precipitation in 1995 was similar to the long-term average,

and yields in that year might be assumed to be

similar to average.

The HSPF model for the Christina River

Basin can be used to compare simulated loads in

the Christina River Basin and adjacent basins,

where monitoring data are limited, to loads calculated from extensive observed data in nearby

basins to the west that drain to the Chesapeake

Bay. Evaluation of monitoring data from these

nearby basins indicates a positive correlation

between the percentage of land in agricultural use

and calculated yields of nitrate, ammonia, phosphorus, and suspended sediment (Langland and

others, 1995). Similar relations are indicated by

results of the HSPF model for the Brandywine

Creek, White Clay Creek, and Red Clay Creek

(Senior and Koerkle, 2003a; 2003b; 2003c), and the

Christina River subbasins. Comparison of simulated and calculated yields suggests that these

models provide reasonable estimates of nonpointsource yields (figs. 42 and 43).

The HSPF model for the Christina River

Basin also can be used to compare simulated loads

from land-based nonpoint sources to reported

loads from point-source discharges to streams in

the basin. For example, total nitrate, ammonia, and

orthophosphate loads as estimated by the HSPF

models for the drainage area above selected

streamflow-measurement stations near the bottom

of the main subbasins (Brandywine Creek, White

Clay Creek, Red Clay Creek, and the Christina

River) are listed with estimated and reported loads

from point-source discharges to the streams in

table 32. For phosphorus in table 32, the reported

point source loads are for total phosphorus and the

simulated nonpoint-source loads are for total

orthophosphate, which would be a minimum estimate for total phosphorus. The simulated loads

shown in table 32 are for the entire Christina River

Basin for the 4-year period (October 1994-October

1998) and represent a range of hydrologic conditions. Total loads of nitrate, ammonia, and orthophosphate tend to decrease with decreasing

subbasin area. Yields (or loads per acre) of sediment and nutrients are less for the Christina River

subbasin than for other subbasins.

The relative proportion of nonpoint-source

and point-source contributions differs by constituent and by subbasin. The White Clay Creek subbasin had the least amount of point-source loads

relative to nonpoint-source loads of the four subbasins modeled. Simulated nitrate loads from nonpoint sources were about twice the estimated

nitrate loads from point sources for Brandywine

Creek and more than 30 times greater than estimated nitrate loads from point sources in the other

subbasins (table 32). Simulated ammonia loads

from nonpoint sources were about twice the estimated ammonia loads from point sources for Brandywine Creek, Red Clay Creek, and Christina

River and more than 30 times greater than estimated ammonia loads from point sources for

White Clay Creek. Simulated phosphorus loads

from nonpoint sources were about 2 times greater

than estimated phosphorus loads from point

sources for the Christina River, 13 times greater for

Brandywine Creek, 26 times greater for Red Clay

Creek, and almost 100 times greater than estimated

phosphorus loads from point sources for White

Clay Creek.

The HSPF models for the Christina River

Basin may be used as a predictive tool to estimate

loads under statistically identified flow conditions,

such as those based on some period of record. For

example, expected average or baseline constituent

loads from the whole basin or selected subbasins in

the Christina River Basin could be estimated for

base flow or stormflow conditions by selecting

simulation periods corresponding to periods of
90 Overview of Christina River Basin Models

0 10 20 30 40 50 60 70 80 90 100

AGRICULTURAL LAND USE, IN PERCENT

0.05

20

0.1

0.2

0.5

1

2

5

10

PHOSPHOROUS YIELD, IN POUNDS PER ACRE

0 10 20 30 40 50 60 70 80 90 100

AGRICULTURAL LAND USE, IN PERCENT

0

6,000

1,000

2,000

3,000

4,000

5,000

SEDIMENT YIELD, IN POUNDS PER ACRE

EXPLANATION

PIEDMONT SITES: MINIMUM, MAXIMUM, AND

MEAN FOR 1972-92 (LANGLAND AND OTHERS, 1995)

BRANDYWINE CREEK SIMULATION FOR 1995

WHITE CLAY CREEK SIMULATION FOR 1995

RED CLAY CREEK SIMULATION FOR 1995

CHRISTINA RIVER SUBBASIN SIMULATION FOR 1995

Figure 42. Sediment and phosphorus yields in relation to percent agricultural land use as

calculated from observed data for subbasins in the Chesapeake Bay Watershed and as

simulated by Hydrological Simulation Program–Fortran (HSPF) model for selected subbasins

in the Brandywine Creek, White Clay Creek, Red Clay Creek, and Christina River Basins.
Overview of Christina River Basin Models 91

0 10 20 30 40 50 60 70 80 90 100

AGRICULTURAL LAND USE, IN PERCENT

0

40

10

20

30

NITRATE YIELD, IN POUNDS PER ACRE OF NITROGEN

0 10 20 30 40 50 60 70 80 90 100

AGRICULTURAL LAND USE, IN PERCENT

0.1

20

0.2

0.5

1

2

5

10

AMMONIA YIELD, IN LBS PER ACRE AS NITROGEN

EXPLANATION

PIEDMONT SITES: MINIMUM, MAXIMUM, AND

MEAN FOR 1972-92 (LANGLAND AND OTHERS, 1995)

BRANDYWINE CREEK SIMULATION FOR 1995

WHITE CLAY CREEK SIMULATION FOR 1995

RED CLAY CREEK SIMULATION FOR 1995

CHRISTINA RIVER SUBBASIN SIMULATION FOR 1995

Figure 43. Yields of nitrate and ammonia in relation to percent agricultural land use as

calculated from observed data for subbasins in the Chesapeake Bay Watershed and as

simulated by Hydrological Simulation Program–Fortran (HSPF) model for selected subbasins in

the Brandywine Creek, White Clay Creek, Red Clay Creek, and Christina River Basins.
92 Overview of Christina River Basin Models

Table 32. Total simulated nonpoint-source and estimated point-source loads of

nitrate, ammonia, and phosphorus for the 4-year period October 1, 1994, through

September 30, 1998, Christina River Basin

Drainage area

(square miles)

Total load, 1994-98, in tons

Nitrate1 Ammonia Phosphorus2

Brandywine Creek3 314

Nonpoint source 5,860 123 1,470

Point source 3,390 55 112

White Clay Creek4 89.1

Nonpoint source 1,414 54 455

Point source 3.5 4 4.7

Red Clay Creek5 52.4

Nonpoint source 696 29 266

Point source 25 30 13

Christina River6 20.9

Nonpoint source 198 5.0 43

Point source 2.6 3.1 1.2

1 Estimated for point sources from reported ammonia loads.

2 Estimated by simulated total orthosphosphate for nonpoint sources.

3 Reported point-source discharges and simulated nonpoint-source loads for

drainage area above 01481500, Brandywine Creek at Wilmington Del. 4 Reported point-source discharges and simulated nonpoint-source loads for

drainage area above 01479000, White Clay Creek near Newark, Del.

5 Reported point-source discharges and simulated nonpoint-source loads for

drainage area above 01480015, Red Clay Creek near Stanton, Del.

6 Reported point-source discharges and simulated nonpoint-source loads for

drainage area above 01478000, Christina River at Coochs Bridge, Del.
Overview of Christina River Basin Models 93

normal precipitation. In addition, loads for events

associated with statistical recurrence intervals such

as the 25-year storm or 100-year flood could be

estimated by selecting simulation periods where

the hydrologic record indicates events of these

magnitudes have occurred.

The transport pathways from land to stream

for nonpoint-source contaminants differ by constituent. In the Christina River models, the majority of

nitrate enters the stream through ground-water

discharge and the majority of ammonia and orthophosphate enters the stream through surface runoff and interflow. This information may be useful

to water-resources managers in devising strategies

to reduce loads from nonpoint sources. For example, the HSPF model for the Christina River subbasin can be used to quantify the amount of nutrients

that entered the stream in ground water or runoff.

For the October 1994 through October 1998 simulation period, the model estimated that about

60 percent of the nitrate load from nonpoint

sources (land areas) above the Christina River at

Coochs Bridge, Del., entered the stream through

ground-water discharge. Further, the model estimates only about 20 percent of ammonia and

2 percent of orthophosphate entered the stream

through ground-water discharge in the drainage

area above Coochs Bridge, and the balance of these

constituents entered the stream in interflow and

surface-water runoff.

Successful application of the Christina River

Basin HSPF models to future scenarios or periods

of record other than the calibration period will be

best supported if the model is calibrated to a broad

range of representative hydrologic conditions. The

Christina River Basin models generally were calibrated to a range of streamflows that covered all

but the more extreme high-flow and low-flow periods (Senior and Koerkle, 2003a; 2003b; 2003c). For

example, comparison of the simulated and

observed daily mean streamflow duration curves

for the simulation period at station 01478000,

Christina River at Coochs Bridge, Del., to the

observed daily mean streamflow duration curve

for the 58-year period October 1, 1943, to September 30, 2001 (fig. 44), shows generally good agreement. Daily mean streamflows greater than 1,000

ft3/s did not occur in the simulation period, so that

above that value, the duration curves for the simulation period are extrapolations and should not be

directly compared with the duration curve for the

period of record. Daily mean streamflows greater

than 1,000 ft3/s occurred less than 0.1 percent of

the time during the 58-year period of record at

0.01 0.1 1 2 5 10 20 30 40 50 60 70 80 90 95 98 99 99.9 99.99

PERCENT OF THE TIME STREAMFLOW EQUALED OR EXCEEDED

0.1

10,000

0.2

0.5

1

2

5

10

20

50

100

200

500

1,000

2,000

5,000

DAILY MEAN STREAMFLOW, IN CUBIC FEET PER SECOND

Figure 44. Duration curves of observed daily mean streamflow for the period October 1, 1943, to

September 30, 2001, and of observed and simulated daily mean streamflow for the period of

simulation, October 1, 1994, to October 29, 1998, at 01478000, Christina River at Coochs Bridge, Del.

OBSERVED OCTOBER 1943 - SEPTEMBER 2001

OBSERVED OCTOBER 1994 - OCTOBER 1998

SIMULATED OCTOBER 1994 - OCTOBER 1998
94 Overview of Christina River Basin Models

Christina River at Coochs Bridge. The highest

streamflows generally produce the largest loads of

suspended constituents, but they are also infrequent events. Below about 1.5 ft3

/s, duration

curves for the simulation period and 58-year

period of record do show substantial departure.

Thus, the performance of the model simulations at

these low flows, estimated to occur 2 percent of the

time, is unknown; however, the transport of suspended nonpoint-source constituents can be

expected to be negligible during these infrequent

occurrences.

Limitations and Uncertainty

Model use should consider calibration

approaches and limitations of data. Because the

model was calibrated for relatively large drainage

areas, the model should not be expected to predict

well the hydrologic response and water quality for

drainage areas of less than 10 to 20 mi2. In addition, because the model was calibrated with waterquality parameters transferred between one or

more subbasins, the models may not necessarily

characterize differences related to variations in

land use and loading rates within the Christina

River Basin.

Limited water-quality data were available to

calibrate and assess the water-quality simulation,

especially during storm or high-flow conditions.

Substantial uncertainty is associated with the

water-quality simulations due to limited monitoring data, and for main-stem sites downstream of

point-source discharges, lack of daily or hourly

discharge information. Nevertheless, estimates of

model uncertainty for stormflow and base-flow

conditions were obtained from the 1998 nonpointsource monitoring data. Figures 45-47 are boxplots

that show the range in ratios of simulated to

observed stormflow volume and constituent loads

for sampled storms in 1998. The ratio of simulated

to observed flow or loads for a perfect simulation

with neither a positive or negative bias would be

equal to 1.0. A dotted line equal to 1.0 is shown on

the figures as a reference to evaluate the degree to

which simulated values are greater or smaller than

observed values. The median value indicates the

central tendency of the simulation and the box and

whiskers diagram shows the range of values outside the median. The box includes 50 percent of the

data and the whiskers include 80 percent of the

data (between the 90th and 10th percentiles).

Data are grouped into main-stem and subbasin sites. The main-stem sites include the streamflow-measurement stations near the bottom of the

free-flowing sections of Brandywine Creek, Red

Clay Creek, White Clay Creek, and Christina River

and drain relatively large areas with a variety of

different land uses. The subbasin sites include the

nonpoint-source monitoring sites in drainage areas

predominantly covered by one of seven land uses.

Simulated stream volumes or constituent loads for

individual sites within the main stem and subbasin

groups may be more similar to observed stream

volumes or constituent loads shown for the groupings as a whole.

The range in ratios of simulated to observed

stormflow volume and suspended sediment and

nutrient loads commonly is smaller for main-stem

sites than subbasin sites (figs. 45-47). For stormflow volume, differences in main-stem and subbasin simulated to observed ratios are partly a

consequence of the greater emphasis that was

placed on the hydrologic calibration of main-stem

sites than of small subbasin sites. The model simulations for stormflow volume at main-stem sites

appear to have little positive or negative bias compared to a slight negative bias (undersimulation) at

the subbasin sites (fig. 45). The median ratio of

simulated to observed stormflow volume for mainstem sites is near 1.0 and for subbasin sites is about

0.8.

The errors in water-quality load simulations

commonly will be larger than streamflow simulations because simulation errors include those associated with water-quality and streamflow

simulations. For suspended sediment, the median

ratios of simulated to observed loads is near 1.0 for

main-stem and subbasin sites, indicating little bias

in the simulations. However, the range in ratios of

simulated to observed suspended-sediment loads

is larger than the range in ratio of simulated to

observed stormflow volumes. For nitrate, the

median ratios of simulated to observed loads is

about 0.7 for main-stem and subbasin sites, indicating undersimulation. The range in ratio of simulated to observed nitrate loads is not as large as

that for sediment loads and suggests that uncertainty in simulated nitrate is less than that for suspended sediment.

For dissolved ammonia, the median ratios of

simulated to observed loads was about 2.0 for

main-stem sites and 0.4 for subbasin sites (fig. 46).

These results indicate that dissolved ammonia
Overview of Christina River Basin Models 95

MAIN STEM SUBBASIN

SITE TYPE

0.1

10

0.2

0.3

0.4

0.5

0.7

1

2

3

4

5

7

RATIO OF SIMULATED TO OBSERVED

STREAMFLOW VOLUME

EXPLANATION

10TH PERCENTILE

25TH PERCENTILE

MEDIAN

75TH PERCENTILE

90TH PERCENTILE

10TH AND 90TH PERCENTILES

DATA VALUES OUTSIDE THE

RATIO = SIMULATED/OBSERVED

MAIN STEM SUBBASIN

SITE TYPE

0.001

100

0.002

0.005

0.01

0.02

0.05

0.1

0.2

0.5

1

2

5

10

20

50

RATIO OF SIMULATED TO OBSERVED

SUSPENDED-SEDIMENT LOAD

MAIN STEM SUBBASIN

SITE TYPE

0.1

10

0.2

0.3

0.4

0.5

0.7

1

2

3

4

5

7

RATIO OF SIMULATED TO OBSERVED

NITRATE LOAD

Figure 45. Boxplots showing ratio of simulated to observed streamflow, suspended-sediment loads, and nitrate

loads for sampled storms in 1998 at four main-stem sites and seven subbasin sites in the Christina River Basin.

Ratio of simulated to observed equals 1.0
96 Overview of Christina River Basin Models

MAIN STEM SUBBASIN

SITE TYPE

0.02

100

0.05

0.1

0.2

0.5

1

2

5

10

20

50

RATIO OF SIMULATED TO OBSERVED

DISSOLVED AMMONIA LOAD

EXPLANATION

10TH PERCENTILE

25TH PERCENTILE

MEDIAN

75TH PERCENTILE

90TH PERCENTILE

10TH AND 90TH PERCENTILES

DATA VALUES OUTSIDE THE

RATIO = SIMULATED/OBSERVED

MAIN STEM SUBBASIN

SITE TYPE

0.01

100

0.02

0.05

0.1

0.2

0.5

1

2

5

10

20

50

RATIO OF SIMULATED TO OBSERVED

PARTICULATE AMMONIA LOAD

MAIN STEM SUBBASIN

SITE TYPE

0.01

100

0.02

0.05

0.1

0.2

0.5

1

2

5

10

20

50

RATIO OF SIMULATED TO OBSERVED

TOTAL AMMONIA LOAD

Figure 46. Boxplots showing ratio of simulated to observed dissolved ammonia, particulate ammonia, and

total ammonia loads for sampled storms in 1998 at four main-stem sites and seven subbasin sites in the

Christina River Basin.

Ratio of simulated to observed equals 1.0
Overview of Christina River Basin Models 97

MAIN STEM SUBBASIN

SITE TYPE

0.01

10

0.02

0.03

0.04

0.05

0.07

0.1

0.2

0.3

0.4

0.5

0.7

1

2

3

4

5

7

RATIO OF SIMULATED TO OBSERVED

DISSOLVED ORTHOPHOSPHATE LOAD

EXPLANATION

10TH PERCENTILE

25TH PERCENTILE

MEDIAN

75TH PERCENTILE

90TH PERCENTILE

10TH AND 90TH PERCENTILES

DATA VALUES OUTSIDE THE

RATIO = SIMULATED/OBSERVED

MAIN STEM SUBBASIN

SITE TYPE

0.001

100

0.002

0.005

0.01

0.02

0.05

0.1

0.2

0.5

1

2

5

10

20

50

RATIO OF SIMULATED TO OBSERVED

PARTICULATE ORTHOPHOSPHATE LOAD

MAIN STEM SUBBASIN

SITE TYPE

0.01

100

0.02

0.05

0.1

0.2

0.5

1

2

5

10

20

50

RATIO OF SIMULATED TO OBSERVED

TOTAL ORTHOPHOSPHATE LOAD

Figure 47. Boxplots showing ratio of simulated to observed dissolved orthophosphate, particulate

orthophosphate, and total orthophosphate loads for sampled storms in 1998 at four main-stem sites and seven

subbasin sites in the Christina River Basin.

Ratio of simulated to observed equals 1.0
98 Summary and Conclusions

tended to be oversimulated at main-stem sites and

undersimulated at subbasin sites. The oversimulation of dissolved ammonia at main-stem sites may

be related to errors in estimated point-source discharges of ammonia and (or) in-stream processing

of nutrients. For particulate ammonia, the median

ratios of simulated to observed loads is about

1.5 for main-stem sites and 0.7 for subbasin sites,

and for total ammonia (dissolved plus particulate),

the median ratios of simulated to observed loads

was about 1.2 for main-stem sites and 0.5 for subbasin sites (fig. 46). The range of ratios of simulated to observed loads was smaller for total

ammonia than for dissolved or particulate ammonia. This result may indicate that a source of model

error may be associated with the simulated partitioning of ammonia between the dissolved and

particulate phases.

For dissolved orthophosphate, the median

ratios of simulated to observed loads was about

0.95 for main-stem sites and 0.85 for subbasin sites,

indicating little bias in the simulation (fig. 47). For

particulate orthophosphate, the median ratios of

simulated to observed loads was about 0.25 for

main-stem and subbasin sites, indicating undersimulation. The apparent undersimulation of particulate orthophosphate may be due to forms of

phosphorus other than adsorbed orthophosphate

in the total phosphorus analyzed by the laboratory.

For total orthophosphate (dissolved plus particulate), the median ratios of simulated to observed

loads was about 0.6 for main-stem and subbasin

sites. The range of ratios of simulated to observed

loads for total orthophosphate was similar to that

for particulate orthophosphate because much of

stormload orthophosphate was in the particulate

phase. However, the median of simulated to

observed ratios for total orthophosphate was

closer to 1.0 than the median of simulated to

observed ratios for particulate orthophosphate and

probably was due to the superior simulation of the

dissolved component of orthophos-phate (fig. 47).

Uncertainty associated with the simulation

under base-flow conditions can be estimated from

boxplots that show the range in ratios of simulated

to observed stormflow and constituent loads in

base-flow samples collected in 1998 (fig. 48). Under

base-flow conditions, dissolved nutrient loads are

larger than particulate nutrient loads and only dissolved loads are plotted in figure 48. In the baseflow samples collected in 1998 at nonpoint-source

monitoring sites in the Christina River Basin, the

dissolved ammonia load represented on average

about 75 percent of the total ammonia load and the

dissolved orthophosphate load represented on

average about 65 percent of the total phosphorus

load. In general, simulated streamflow and nutrient loads were more similar to observed streamflow and nutrient loads at the subbasin sites than

at the main-stem sites. The median ratios of simulated hourly mean to observed instantaneous

streamflow and dissolved nutrients were closer to

1.0 for the subbasin sites than for the main-stem

sites (fig. 48). Differences in the apparent accuracy

of nutrient simulation at the two types of sites may

result in part from errors in estimating pointsource discharges that affect water quality at the

main-stem site and in part from a slighter greater

bias in streamflow simulation at the main-stem

sites than at the subbasin sites. No bias was apparent for the simulation of nitrate, dissolved ammonia, and dissolved orthophosphate loads at the

subbasin sites under base-flow conditions. Nitrate

and dissolved ammonia tended to be oversimulated at the main-stem sites under base-flow conditions.

SUMMARY AND CONCLUSIONS

The Christina River Basin drains 565 mi2 in

Pennsylvania and Delaware and is used for recreation, drinking water supply, and support of

aquatic life. The Christina River Basin includes the

major subbasins of Brandywine Creek (327 mi2),

White Clay Creek (89 mi2), Red Clay Creek

(54 mi2), and the Christina River (76 mi2). Monitoring data indicate that water quality in some parts

of the Christina River Basin is impaired and does

not support designated uses of the stream. A

water-quality management strategy developed by

a group of local, county, State, and Federal agencies to address water-quality problems included a

modeling component to evaluate the effects of

point and nonpoint-source contributions of nutrients and suspended sediment on stream water

quality. The model selected for the nonpointsource evaluation was Hydrological-Simulation

Program–Fortran (HSPF). The HSPF model for the

Christina River Basin was constructed and calibrated by the USGS in cooperation with the Delaware River Basin Commission, Delaware

Department of Natural Resources and Environmental Control (DNREC), and Pennsylvania

Department of Environmental Protection (PADEP)

and consists of four independent models, one for

each of the four main subbasins. Reports describing the HSPF model for each subbasin were pre-
Summary and Conclusions 99

MAIN STEM SUBBASIN

SITE TYPE

0.5

5

1

2

RATIO OF SIMULATED TO OBSERVED

STREAMFLOW

EXPLANATION

10TH PERCENTILE

25TH PERCENTILE

MEDIAN

75TH PERCENTILE

90TH PERCENTILE

10TH AND 90TH PERCENTILES

DATA VALUES OUTSIDE THE

RATIO = SIMULATED/OBSERVED

MAIN STEM SUBBASIN

SITE TYPE

0.2

10

0.5

1

2

5

RATIO OF SIMULATED TO OBSERVED

NITRATE LOAD

MAIN STEM SUBBASIN

SITE TYPE

0.1

100

0.2

0.5

1

2

5

10

20

50

RATIO OF SIMULATED TO OBSERVED

DISSOLVED AMMONIA LOAD

MAIN STEM SUBBASIN

SITE TYPE

0.1

10

0.2

0.5

1

2

5

RATIO OF SIMULATED TO OBSERVED

DISSOLVED ORTHOPHOSPHATE LOAD

Figure 48. Boxplots showing ratio of simulated mean hourly to observed instantaneous streamflow, nitrate,

dissolved ammonia, and dissolved orthophosphate loads for base-flow periods in 1998 at four main stem

sites and seven subbasin sites in the Christina River Basin.

RATIO OF SIMULATED TO OBSERVED EQUALS 1.0
100 Summary and Conclusions

pared. This report describes the HSPF model for

the Christina River subbasin and provides an overview of all four subbasin models.

The USGS also developed and executed a

monitoring plan to collect water-quality data in

each of the four main subbasins and in small areas

predominantly covered by one land use for model

calibration. Under this plan, stormflow and baseflow samples were collected during 1998 at two

sites in the Christina River subbasin and nine sites

elsewhere in the Christina River Basin. Seven of

the eleven monitored stream sites in the Christina

River Basin drained areas ranging in size from

0.6 to 18.7 mi2 that were predominantly covered by

one land use: mixed animal and row-crop agricultural; row-crop agricultural; mushroom-growing

agricultural; forested; sewered residential; un-sewered residential; or urban. The nonpoint-source

monitoring site at the streamflow-measurement

station 01480095, Little Mill Creek near Newport,

Del., had a drainage area of about 5.4 mi2 where

the land use is predominantly urban. The nonpoint-source monitoring site at the streamflowmeasurement station 01478000, Christina River at

Coochs Bridge, Del., was a few miles upstream of

the tidal part of the Christina River and had a

drainage area of about 21 mi2 where the land use is

mixed. Water samples were analyzed for dissolved

and total nutrients and suspended solids. Because

suspended-sediment data were not available, suspended-solids data were used as a surrogate for

suspended-sediment data. The monitoring data

indicated that suspended solids and total phosphorus concentrations were higher in stormflow

than in base-flow samples whereas dissolved

nitrate concentrations tended to be higher in baseflow than in stormflow samples.

The HSPF model for the Christina River subbasin was used to simulate streamflow, suspended

sediment, and several species of the nutrients

nitrogen and phosphorus. For the model, the subbasin was subdivided into nine reaches draining

areas that ranged from 3.8 to 21.9 mi2. Hydrologic

routing was not simulated for the three reaches

containing an impoundment (Belltown Run,

Muddy Run, Smalley’s Pond) and the one tidal

reach below Smalley’s Pond. Ten different pervious land uses and 2 impervious land uses were

selected for simulation. Land-use areas were determined from 1995 land-use data. The predominant

land uses in the Christina River subbasin were residential, urban, forested, and agricultural.

The hydrologic component of the model was

run at an hourly time step and calibrated using

streamflow data from two USGS streamflow-measurement stations for the period of October 1, 1994,

through October 29, 1998. Daily precipitation data

from one National Oceanic and Atmospheric

Administration (NOAA) meteorologic station near

the western part of Christina River subbasin and

hourly precipitation-intensity data from one

NOAA meteorologic station to the southeast of the

subbasin were used for model input. The difference between observed and simulated streamflow

volume ranged from -2.3 to 5.3 percent for a

10-month period at the two calibration sites.

Annual differences between observed and simulated streamflow generally were greater than the

overall error. For example, at streamflow-measurement station 01478000, Christina River at Coochs

Bridge, Del. (drainage area of 20.9 mi2), annual differences between observed and simulated streamflow ranged from -6.9 to 6.5 percent and the overall

error for the 4-year period was -1.1 percent

(-0.9 in.). At the two streamflow-measurement stations, calibration errors for total flow volume, lowflow-recession rate, 50-percent lowest flows,

10-percent highest flows, storm peaks and other

seasonal measures generally were within recommended criteria for a satisfactory calibration. Much

of the error in simulating storm events on an

hourly time step can be attributed to uncertainty in

the rainfall data.

Model parameters affecting water quality

were taken, with minor adjustments, from calibrated HSPF models for the adjacent Brandywine

Creek, White Clay Creek, and Red Clay Creek subbasins, where data were available to calibrate

inputs from specific land uses. The calibration of

water-quality components of the Christina River

subbasin model was assessed using monitoring

data collected at two USGS streamflow-measurement stations with variable periods ending October 1998. Both stations were downstream of pointsource discharges. The date for the start of waterquality monitoring ranged from October 1994 to

January 1998. Suspended-solids data collected during monitoring were used as estimates for suspended sediment. Fewer data were available for

water-quality calibration than for streamflow calibration. Simulated cumulative loads of suspended

sediment, nitrate, dissolved and particulate ammonia, and dissolved orthophosphate and particulate

phosphorus were within an order of magnitude or

less of observed loads for storms sampled in 1998
References Cited 101

at the nonpoint-source monitoring sites. Simulation errors for grab samples collected by state

agencies near the two streamflow-measurement

stations were larger and may be due in part to differences in water quality at the sampling locations.

Errors in ammonia simulation apparently were

greater than errors in nitrate and orthophosphate

simulation. Some error could be related to variability in point-source discharges upstream of monitoring sites. The error in water-quality loads

typically was larger than the error in simulated

stormflows, which was included in the water-quality error. Error in simulation of dissolved constituents generally was less than the error in simulation

of particulate constituents. In storms, particulate

phosphorus loads generally were greater than dissolved orthophosphate loads, and nitrate loads

were about one order of magnitude greater than

dissolved ammonia loads and two orders of magnitude greater than particulate ammonia loads.

Simulated yields of suspended sediment,

nitrate, and ammonia for land uses in the Christina

River subbasin were similar to yields simulated for

those land uses in adjacent basins and to yields calculated from monitoring data for subbasins in the

nearby Chesapeake Bay drainage. Yields

(expressed in pounds per acre) of these constituents tended to increase as the percent of agricultural land increased. Nutrient yields generally

were smaller in the Christina River subbasin than

in the other subbasins because of the differences in

land uses. The Christina River subbasin had proportionately more urban and residential land and

less agricultural land than the White Clay, Red

Clay, and Brandywine Creek subbasins.

Users of the Christina River Basin HSPF

models should be aware of model limitations and

consider the following when predictive scenarios

are desired: duration curves suggest the model

simulates streamflow reasonably well when measured over a broad range of conditions and time

although streamflow and the corresponding waterquality for individual storm events may not be

well simulated; streamflow duration curves for the

simulation period compare well with duration

curves for the longer periods of record, such as the

55.5-year period ending in 1998 at Christina River

at Coochs Bridge, Del., and include all but the

extreme high-flow and low-flow events; calibration for water quality was based on limited data,

with the effect of increasing uncertainty in the

water-quality simulation. Given these limitations,

the model may be considered appropriate for simulating streamflow and water-quality concentrations and yields over relatively long periods of

time, such as the 5-year period used for model calibration.

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Appendix 1 105

APPENDIX 1

STORMFLOW AND BASE-FLOW WATER QUALITY
106 Appendix 1

Table 1. Results of laboratory analysis of stormflow samples collected at two sites in the Christina River subbasin, 1998

 ELEV. DIS- DIS- SPE- RESIDUE NITRO-

 AGENCY AGENCY OF LAND CHARGE, CHARGE, CIFIC CHLO- TOTAL GEN,

 ANA- COL- SURFACE IN INST. DRAIN- CON- RIDE, AT 105 AMMONIA

 LYZING LECTING DATUM CUBIC CUBIC AGE DUCT- DIS- DEG. C, DIS-

 Ending Ending SAMPLE SAMPLE (FT. FEET FEET AREA ANCE SOLVED SUS- SOLVED

 Date Time date time (CODE (CODE ABOVE PER PER (SQ. LAB (MG/L PENDED (MG/L

 NUMBER) NUMBER) NGVD) SECOND SECOND MI.) (US/CM) AS CL) (MG/L) AS N)

 (00028) (00027) (72000) (00060) (00061) (81024) (90095) (00940) (00530) (00608)

 01480095 LITTLE MILL CREEK NEAR NEWPORT, DE (LAT 39 43 54N LONG 075 36 14W)

 FEB 1998

 04... 1415 19980205 1313 10003 1028 -- 24 -- 5.24 227 27.0 34 .104

 04... 2106 -- -- 10003 1028 -- -- 29 5.24 270 40.0 12 .113

 04... 2306 -- -- 10003 1028 -- -- 25 5.24 222 29.0 9 .140

 05... 0506 -- -- 10003 1028 -- -- 18 5.24 203 25.0 9 .137

 MAR

 08... 1129 19980309 0629 10003 1028 -- 78 -- 5.24 136 13.6 63 .066

 08... 1545 -- -- 10003 1028 -- -- 68 5.24 169 20.3 37 .068

 08... 1745 -- -- 10003 1028 -- -- 85 5.24 140 15.5 35 .061

 08... 1945 -- -- 10003 1028 -- -- 56 5.24 141 14.8 19 .071

 MAY

 01... 1536 19980503 0055 10003 1028 -- 11 -- 5.24 246 30.5 20 .012

 02... 0104 -- -- 10003 1028 -- -- 22 5.24 217 25.1 10 .070

 JUN

 11... 2302 -- -- 10003 1028 -- -- 9.6 5.24 265 34.0 46 .008

 11... 2302 19980612 1829 10003 1028 -- 75 -- 5.24 113 10.5 290 .122

 12... 0032 -- -- 10003 1028 -- -- 13 5.24 291 43.3 28 .014

 12... 0202 -- -- 10003 1028 -- -- 38 5.24 191 25.2 80 .117

 12... 0502 -- -- 10003 1028 -- -- 84 5.24 108 10.1 200 .096

 JUL

 08... 0647 -- -- 10003 1028 -- -- 7.8 5.24 290 34.9 68 .006

 08... 0647 19980709 0034 10003 1028 -- 45 -- 5.24 452 10.2 173 .082

 08... 0816 -- -- 10003 1028 -- -- 85 5.24 174 17.8 211 .095

 08... 0946 -- -- 10003 1028 -- -- 152 5.24 86 6.1 176 .112

 08... 1116 -- -- 10003 1028 -- -- 87 5.24 96 7.4 122 .082

 08... 1416 -- -- 10003 1028 -- -- 25 5.24 112 7.5 29 .076

 OCT

 08... 1128 -- -- 10003 1028 -- -- 7.2 5.24 271 33.0 92 .025

 08... 1128 19981009 0118 10003 1028 -- 27 -- 5.24 158 18.0 80 .021

 08... 1258 -- -- 10003 1028 -- -- 38 5.24 159 17.0 93 .060

 08... 1558 -- -- 10003 1028 -- -- 42 5.24 160 15.0 41 .183

 08... 1728 -- -- 10003 1028 -- -- 34 5.24 159 18.0 25 .023

 08... 1858 -- -- 10003 1028 -- -- 26 5.24 161 17.0 19 .023

 01478000 CHRISTINA RIVER AT COOCHS BRIDGE, DE (LAT 39 38 14N LONG 075 43 40W)

 MAR 1998

 08... 1305 19980309 0921 10003 1028 25.54 305 -- 20.50 112 14.2 66 .053

 08... 1650 -- -- 10003 1028 25.54 -- 134 20.50 186 24.6 26 .062

 08... 2250 -- -- 10003 1028 25.54 -- 405 20.50 106 12.9 156 .046

 09... 0050 -- -- 10003 1028 25.54 -- 354 20.50 93 11.0 114 .048

 MAY

 01... 1710 19980503 0820 10003 1028 25.54 21 -- 20.50 219 31.3 6 .037

 01... 1933 -- -- 10003 1028 25.54 -- 33 20.50 259 35.0 3 .034

 01... 2333 -- -- 10003 1028 25.54 -- 35 20.50 259 37.5 6 .090

 JUN

 11... 2344 19980613 0806 10003 1028 25.54 94 -- 20.50 133 15.3 40 .047

 12... 0544 -- -- 10003 1028 25.54 -- 132 20.50 117 17.6 73 .125

 12... 0944 -- -- 10003 1028 25.54 -- 198 20.50 163 13.2 127 .071

 12... 1144 -- -- 10003 1028 25.54 -- 225 20.50 99 10.8 70 .116

 JUL

 08... 0840 19980709 0316 10003 1028 25.54 76 -- 20.50 143 16.3 91 .035

 08... 1040 -- -- 10003 1028 25.54 -- 208 20.50 156 10.9 137 .087

 08... 1240 -- -- 10003 1028 25.54 -- 144 20.50 150 17.4 52 .047

 08... 1840 -- -- 10003 1028 25.54 -- 61 20.50 123 11.3 21 .058

 08... 2040 -- -- 10003 1028 25.54 -- 47 20.50 127 11.8 17 .075

 OCT

 08... 1536 19981009 0415 10003 1028 25.54 65 -- 20.50 171 25.0 10 <.005

 08... 1736 -- -- 10003 1028 25.54 -- 59 20.50 116 18.0 25 .024

 08... 1936 -- -- 10003 1028 25.54 -- 41 20.50 188 29.0 10 .031

 08... 2136 -- -- 10003 1028 25.54 -- 35 20.50 186 26.0 11 .024
Appendix 1 107

Table 1. Results of laboratory analysis of stormflow samples collected at two sites in the Christina River subbasin, 1998—Continued

 NITRO- NITRO- NITRO- ORTHO- OXYGEN

 GEN,AM- GEN,AM- NITRO- GEN, PHOS- PHOS- CARBON, OXYGEN DEMAND,

 MONIA + MONIA + GEN, NO2+NO3 PHORUS PHATE, PHOS- ORGANIC CARBON, DEMAND, CHEM-

 ORGANIC ORGANIC AMMONIA DIS- DIS- DIS- PHORUS DIS- ORGANIC BIOCHEM ICAL

 DIS. TOTAL TOTAL SOLVED SOLVED SOLVED TOTAL SOLVED TOTAL CARBON. (HIGH

 Date (MG/L (MG/L (MG/L (MG/L (MG/L (MG/L (MG/L (MG/L (MG/L 20 LEVEL)

 AS N) AS N) AS N) AS N) AS P) AS P) AS P) AS C) AS C) (MG/L) (MG/L)

 (00623) (00625) (00610) (00631) (00666) (00671) (00665) (00681) (00680) (80087) (00340)

 01480095 LITTLE MILL CREEK NEAR NEWPORT, DE (LAT 39 43 54N LONG 075 36 14W)

 FEB 1998

 04... .30 .56 .115 .989 .027 .017 .060 7.0 -- 6.7 13

 04... .56 .65 .122 1.14 .024 .015 .071 7.0 -- 6.5 22

 04... .43 .73 .187 1.06 .029 .015 .062 7.0 -- 8.2 18

 05... .54 .66 .144 .902 .031 .015 .063 9.0 -- 9.2 18

 MAR

 08... .55 1.3 .067 .524 .062 .027 .323 7.0 -- 5.9 11

 08... .41 1.0 .070 .784 .045 .008 .149 5.0 -- 4.1 <1

 08... .63 M .067 .549 .060 .006 .257 7.0 -- 3.4 <1

 08... .70 .91 .087 .541 .076 .016 .266 6.0 -- 5.8 <1

 MAY

 01... .86 .93 .019 .923 .122 .122 .162 8.0 6.0 4.7 <1

 02... .82 1.1 .086 .902 .033 .042 .083 7.0 7.0 2.8 <1

 JUN

 11... 1.4 2.4 .033 1.66 .050 .026 .242 13.0 -- 13 --

 11... .86 3.5 .115 .744 .289 .222 .649 10.0 -- 6.7 --

 12... 1.3 1.9 .048 1.43 .408 .341 .486 12.0 -- 8.1 --

 12... 1.1 2.2 .146 1.13 .111 .068 .302 10.0 -- 8.7 --

 12... .61 2.3 .097 .604 .132 .071 .351 8.0 -- 5.3 --

 JUL

 08... .19 .64 .017 .837 .007 .004 .098 5.0 -- 5.6 --

 08... .18 1.7 .090 .643 .010 .033 .317 9.0 -- 7.2 --

 08... .12 2.1 .105 .784 .018 .036 .403 7.0 -- 8.2 --

 08... .17 1.5 .115 .589 .019 .047 .332 7.0 -- 6.3 --

 08... .18 1.3 .091 .520 .030 .033 .224 6.0 -- 4.9 --

 08... .55 1.0 .077 .693 .086 .041 .121 9.0 -- 4.2 --

 OCT

 08... -- -- .041 .738 -- .100 -- 7.0 -- M --

 08... -- -- .048 .574 -- .042 -- 7.0 -- 5.0 --

 08... -- -- .087 .587 -- .069 -- 8.0 -- 5.3 --

 08... -- -- .158 .595 -- .080 -- 8.0 -- 4.9 --

 08... -- -- .037 .513 -- .051 -- 9.0 -- 5.9 --

 08... -- -- .042 .534 -- .042 -- 8.0 -- 5.0 --

 01478000 CHRISTINA RIVER AT COOCHS BRIDGE, DE (LAT 39 38 14N LONG 075 43 40W)

 MAR 1998

 08... .84 1.3 .071 .587 .150 .146 .517 9.0 7.0 8.2 20

 08... .48 .75 .061 1.26 .065 .009 .297 6.0 4.0 3.8 5

 08... .71 1.9 .082 .436 .086 .055 .539 8.0 -- 6.5 12

 09... .96 1.6 .093 .416 .095 .036 .505 9.0 11.0 5.0 30

 MAY

 01... .77 .87 .045 1.61 .015 .008 .044 6.0 6.0 5.6 <1

 01... .23 .20 .036 2.02 .033 .004 .041 3.0 2.0 <2.4 <1

 01... .65 1.0 .093 1.81 .034 .019 .037 5.0 6.0 <2.4 <1

 JUN

 11... .77 1.2 .042 1.01 .128 .026 .200 12.0 12.0 5.0 <1

 12... .91 1.3 .144 1.07 .115 .110 .197 10.0 12.0 5.8 20

 12... .74 1.6 .085 .965 .053 .045 .221 11.0 11.0 <2.4 12

 12... .60 1.1 .101 .754 .069 .037 .138 10.0 12.0 4.9 5

 JUL

 08... .35 1.3 .046 .871 .008 .023 .184 9.0 8.0 14 22

 08... .45 1.8 .088 .581 .028 .028 .278 8.0 7.0 6.7 51

 08... .38 .89 .052 .917 .017 .028 .131 7.0 5.0 4.8 6

 08... .43 .51 .064 .848 .021 .039 .105 6.0 5.0 4.0 21

 08... .46 .57 .241 .937 .020 .058 .082 7.0 5.0 3.9 25

 OCT

 08... -- -- .011 .939 -- .011 -- 8.0 8.0 5.8 <1

 08... -- -- .043 .589 -- .031 -- 7.0 9.0 3.5 6

 08... -- -- .036 1.05 -- .020 -- 6.0 8.0 3.1 <1

 08... -- -- .027 1.01 -- .022 -- 7.0 8.0 3.7 <1

Remark codes used in this report:

 < -- Less than

 M -- Presence verified, not quantified
108 Appendix 1

Table 2. Results of laboratory analysis of base-flow samples collected at two sites in the Christina River subbasin, 1998

 ELEV. DIS- PH ANC RESIDUE

 AGENCY AGENCY OF LAND CHARGE, WATER SPE- WATER CHLO- TOTAL

 ANA- COL- SURFACE INST. DRAIN- WHOLE CIFIC UNFLTRD RIDE, AT 105

 LYZING LECTING DATUM CUBIC AGE OXYGEN, FIELD CON- TEMPER- FET DIS- DEG. C,

 SAMPLE SAMPLE (FT. FEET AREA DIS- (STAND- DUCT- ATURE FIELD SOLVED SUS-

 Date Time (CODE (CODE ABOVE PER (SQ. SOLVED ARD ANCE WATER MG/L AS (MG/L PENDED

 NUMBER) NUMBER) NGVD) SECOND MI.) (MG/L) UNITS) (US/CM) (DEG C) CACO3 AS CL) (MG/L)

 (00028) (00027) (72000) (00061) (81024) (00300) (00400) (00095) (00010) (00410) (00940) (00530)

01480095 LITTLE MILL CREEK NEAR NEWPORT, DE (LAT 39 43 54N LONG 075 36 14W)

 APR 1998

 27... 0933 10003 1028 -- 7.2 5.24 10.7 6.8 241 1.3 43 27.6 4

 JUL

 23... 1157 10003 1028 -- 1.5 5.24 8.0 7.2 246 24.2 55 30.0 2

 SEP

 15... 1026 10003 1028 -- .70 5.24 6.5 7.3 339 23.4 74 47.0 22

01478000 CHRISTINA RIVER AT COOCHS BRIDGE, DE (LAT 39 38 14N LONG 075 43 40W)

 APR 1998

 27... 1007 10003 1028 25.54 22 20.50 10.3 6.7 234 1.3 31 31.8 5

 JUL

 23... 1009 10003 1028 25.54 7.5 20.50 7.0 6.8 222 24.3 41 30.0 5

 SEP

 15... 1411 10003 1028 25.54 3.0 20.50 8.6 7.3 286 23.7 51 47.0 23

 NITRO- NITRO- NITRO- NITRO- ORTHO- OXYGEN PHEO-

 GEN, GEN,AM- GEN,AM- NITRO- GEN, PHOS- PHOS- CARBON, OXYGEN DEMAND, PHYTIN

 AMMONIA MONIA + MONIA + GEN, NO2+NO3 PHORUS PHATE, PHOS- ORGANIC CARBON, DEMAND, CHEM- PHYTO-

 DIS- ORGANIC ORGANIC AMMONIA DIS- DIS- DIS- PHORUS DIS- ORGANIC BIOCHEM ICAL PLANK-

 SOLVED DIS. TOTAL TOTAL SOLVED SOLVED SOLVED TOTAL SOLVED TOTAL CARBON. (HIGH TON,

 Date (MG/L (MG/L (MG/L (MG/L (MG/L (MG/L (MG/L (MG/L (MG/L (MG/L 20 LEVEL) ACID M.

 AS N) AS N) AS N) AS N) AS N) AS P) AS P) AS P) AS C) AS C) (MG/L) (MG/L) (UG/L)

 (00608) (00623) (00625) (00610) (00631) (00666) (00671) (00665) (00681) (00680) (80087) (00340) (32218)

01480095 LITTLE MILL CREEK NEAR NEWPORT, DE (LAT 39 43 54N LONG 075 36 14W)

 APR 1998

 27... .432 .55 .70 .439 1.84 .049 .058 .074 8.0 9.0 5.9 39 <2.00

 JUL

 23... .037 .59 1.3 .059 .886 <.005 .027 .028 5.0 5.0 <2.4 14 <2.00

 SEP

 15... .056 .84 1.2 .054 1.84 .018 .015 .018 4.0 3.0 2.5 7 3.00

01478000 CHRISTINA RIVER AT COOCHS BRIDGE, DE (LAT 39 38 14N LONG 075 43 40W)

 APR 1998

 27... .214 1.4 1.6 .223 2.31 .013 .015 .047 6.0 6.0 2.9 32 3.00

 JUL

 23... .069 .84 1.3 .100 1.50 <.005 .024 .022 7.0 6.0 <2.4 18 <2.00

 SEP

 15... <.005 .38 .65 <.005 1.36 .014 .008 .019 4.0 4.0 <2.4 6 7.00

 CHLORO-

 HPYLL A

 PHYTO-

 PLANK-

 TON

 Date ACID M.

 (UG/L)

 (32211)

01480095 LITTLE MILL CREEK NEAR NEWPORT, DE (LAT 39 43 54N LONG 075 36 14W)

 APR 1998

 27... 5.00

 JUL

 23... 5.00

 SEP

 15... 3.00

01478000 CHRISTINA RIVER AT COOCHS BRIDGE, DE (LAT 39 38 14N LONG 075 43 40W)

 APR 1998

 27... 3.00

 JUL

 23... 5.00

 SEP

 15... 8.00

0Remark codes used in this report:

 < -- Less than
Appendix 2 109

APPENDIX 2

SIMULATED STORMFLOW AND WATER QUALITY

FOR SAMPLED STORMS IN 1998
110 Appendix 2

2400 1200 2400 1200 2400 1200 2400

4 5 6

February 1998

0

4

1

2

3

NITRATE CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

0

40

10

20

30

2400 0800 1600 2400 0800 1600 2400

1 2

May 1998

0

4

1

2

3

NITRATE CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

0

25

5

10

15

20

2400 1200 2400 1200 2400 1200 2400

11 12 13

June 1998

0

400

100

200

300

0

4

1

2

3

NITRATE CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

EXPLANATION

SIMULATED STREAMFLOW

OBSERVED STREAMFLOW

SIMULATED NITRATE

OBSERVED NITRATE

1600 2400 0800 1600 2400 0800

7 8 9

July 1998

0

4

1

2

3

NITRATE CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

0

250

50

100

150

200

1600 2400 0800 1600 2400 0800

7 8 9

October 1998

0

150

50

100

STREAMFLOW,

0

4

1

2

3

NITRATE CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

2400 1200 2400 1200 2400 1200 2400

8 9 10

March 1998

0

300

100

200

0

4

1

2

3

NITRATE CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

Figure 1. Simulated and observed streamflow and concentrations of dissolved nitrate during six storms in 1998

at streamflow-measurement station 01480095, Little Mill Creek near Newport, Del.

IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND
Appendix 2 111

2400 1200 2400 1200 2400 1200 2400

7 8 9

October 1998

0

5

1

2

3

4

NITRATE CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

0

250

50

100

150

200

2400 1200 2400 1200 2400 1200 2400

8 9 10

March 1998

0

1,000

200

400

600

800

0

5

1

2

3

4

NITRATE CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

2400 0800 1600 2400 0800 1600 2400

1 2

May 1998

0

5

1

2

3

4

NITRATE CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

10

60

20

30

40

50

2400 1200 2400 1200 2400 1200 2400

11 12 13

June 1998

0

300

100

200

0

5

1

2

3

4

NITRATE CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

2400 1200 2400 1200 2400 1200 2400

7 8 9

July 1998

0

5

1

2

3

4

NITRATE CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

0

250

50

100

150

200

EXPLANATION

SIMULATED STREAMFLOW

OBSERVED STREAMFLOW

SIMULATED NITRATE

OBSERVED NITRATE

Figure 2. Simulated and observed streamflow and concentrations of dissolved nitrate during five storms in 1998 at

streamflow-measurement station 01478000, Christina River at Coochs Bridge, Delaware. STREAMFLOW, IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND STREAMFLOW, IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND STREAMFLOW, IN CUBIC FEET PER SECOND
112 Appendix 2

2400 1200 2400 1200 2400 1200 2400

4 5 6

February 1998

0

0.4

0.1

0.2

0.3

DISSOLVED AMMONIA CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

0

40

10

20

30

2400 0800 1600 2400 0800 1600 2400

1 2

May 1998

0

0.4

0.1

0.2

0.3

DISSOLVED AMMONIA CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

0

25

5

10

15

20

2400 1200 2400 1200 2400 1200 2400

11 12 13

June 1998

0

400

100

200

300

0

0.4

0.1

0.2

0.3

DISSOLVED AMMONIA CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

EXPLANATION

SIMULATED STREAMFLOW

OBSERVED STREAMFLOW

SIMULATED DISSOLVED AMMONIA

OBSERVED DISSOLVED AMMONIA

1600 2400 0800 1600 2400 0800

7 8 9

July 1998

0

0.4

0.1

0.2

0.3

DISSOLVED AMMONIA CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

0

250

50

100

150

200

1600 2400 0800 1600 2400 0800

7 8 9

October 1998

0

150

50

100

0

0.4

0.1

0.2

0.3

DISSOLVED AMMONIA CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

2400 1200 2400 1200 2400 1200 2400

8 9 10

March 1998

0

300

100

200

0

0.4

0.1

0.2

0.3

DISSOLVED AMMONIA CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

Figure 3. Simulated and observed streamflow and concentrations of dissolved ammonia during six storms in 1998

at streamflow-measurement station 01480095, Little Mill Creek near Newport, Del. STREAMFLOW, IN CUBIC FEET PER SECOND STREAMFLOW, IN CUBIC FEET PER SECOND STREAMFLOW, IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND
Appendix 2 113

2400 1200 2400 1200 2400 1200 2400

7 8 9

October 1998

0

0.5

0.1

0.2

0.3

0.4

DISSOLVED AMMONIA CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

0

250

50

100

150

200

2400 1200 2400 1200 2400 1200 2400

8 9 10

March 1998

0

1,000

200

400

600

800

0

0.5

0.1

0.2

0.3

0.4

DISSOLVED AMMONIA CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

2400 0800 1600 2400 0800 1600 2400

1 2

May 1998

0

0.5

0.1

0.2

0.3

0.4

DISSOLVED AMMONIA CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

10

60

20

30

40

50

2400 1200 2400 1200 2400 1200 2400

11 12 13

June 1998

0

300

100

200

0

0.5

0.1

0.2

0.3

0.4

DISSOLVED AMMONIA CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

2400 1200 2400 1200 2400 1200 2400

7 8 9

July 1998

0

0.5

0.1

0.2

0.3

0.4

DISSOLVED AMMONIA CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

0

250

50

100

150

200

EXPLANATION

SIMULATED STREAMFLOW

OBSERVED STREAMFLOW

SIMULATED DISSOLVED AMMONIA

OBSERVED DISSOLVED AMMONIA

Figure 4. Simulated and observed streamflow and concentrations of dissolved ammonia during five storms in

1998 at streamflow-measurement station 01478000, Christina River at Coochs Bridge, Delaware. STREAMFLOW, IN CUBIC FEET PER SECOND STREAMFLOW, IN CUBIC FEET PER SECOND STREAMFLOW, IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND
114 Appendix 2

2400 1200 2400 1200 2400 1200 2400

4 5 6

February 1998

0

0.10

0.02

0.04

0.06

0.08

PARTICULATE AMMONIA CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

0

40

10

20

30

2400 0800 1600 2400 0800 1600 2400

1 2

May 1998

0

0.10

0.02

0.04

0.06

0.08

PARTICULATE AMMONIA CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

0

25

5

10

15

20

2400 1200 2400 1200 2400 1200 2400

11 12 13

June 1998

0

400

100

200

300

0

0.12

0.02

0.04

0.06

0.08

0.10

PARTICULATE AMMONIA CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

EXPLANATION

SIMULATED STREAMFLOW

OBSERVED STREAMFLOW

SIMULATED PARTICULATE AMMONIA

OBSERVED PARTICULATE AMMONIA

1600 2400 0800 1600 2400 0800

7 8 9

July 1998

0

0.18

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

PARTICULATE AMMONIA CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

0

250

50

100

150

200

1600 2400 0800 1600 2400 0800

7 8 9

October 1998

0

150

50

100

0

0.10

0.02

0.04

0.06

0.08

PARTICULATE AMMONIA CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

2400 1200 2400 1200 2400 1200 2400

8 9 10

March 1998

0

300

100

200

0

0.10

0.02

0.04

0.06

0.08

PARTICULATE AMMONIA CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

Figure 5. Simulated and observed streamflow and concentrations of particulate ammonia during six storms in 1998

at streamflow-measurement station 01480095, Little Mill Creek near Newport, Del. STREAMFLOW, IN CUBIC FEET PER SECOND STREAMFLOW, IN CUBIC FEET PER SECOND STREAMFLOW, IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND
Appendix 2 115

2400 1200 2400 1200 2400 1200 2400

7 8 9

October 1998

0

0.05

0.01

0.02

0.03

0.04

PARTICULATE AMMONIA CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

0

250

50

100

150

200

2400 1200 2400 1200 2400 1200 2400

8 9 10

March 1998

0

1,000

200

400

600

800

0

0.05

0.01

0.02

0.03

0.04

PARTICULATE AMMONIA CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

2400 0800 1600 2400 0800 1600 2400

1 2

May 1998

0

0.05

0.01

0.02

0.03

0.04

PARTICULATE AMMONIA CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

10

60

20

30

40

50

2400 1200 2400 1200 2400 1200 2400

11 12 13

June 1998

0

300

100

200

0

0.05

0.01

0.02

0.03

0.04

PARTICULATE AMMONIA CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

2400 1200 2400 1200 2400 1200 2400

7 8 9

July 1998

0

0.08

0.01

0.02

0.03

0.04

0.05

0.06

0.07

PARTICULATE AMMONIA CONCENTRATION,

IN MILLIGRAMS PER LITER AS N

0

250

50

100

150

200

EXPLANATION

SIMULATED STREAMFLOW

OBSERVED STREAMFLOW

SIMULATED PARTICULATE AMMONIA

OBSERVED PARTICULATE AMMONIA

Figure 6. Simulated and observed streamflow and concentrations of particulate ammonia during five storms in 1998

at streamflow-measurement station 01478000, Christina River at Coochs Bridge, Delaware.

STREAMFLOW,

IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND
116 Appendix 2

2400 1200 2400 1200 2400 1200 2400

4 5 6

February 1998

0

0.10

0.02

0.04

0.06

0.08

DISSOLVED ORTHOPHOSPHATE CONCENTRATION, IN MILLIGRAMS PER LITER AS P

0

40

10

20

30

2400 0800 1600 2400 0800 1600 2400

1 2

May 1998

0

0.10

0.02

0.04

0.06

0.08

DISSOLVED ORTHOPHOSPHATE CONCENTRATION, IN MILLIGRAMS PER LITER AS P

0

25

5

10

15

20

2400 1200 2400 1200 2400 1200 2400

11 12 13

June 1998

0

400

100

200

300

0

0.10

0.02

0.04

0.06

0.08

DISSOLVED ORTHOPHOSPHATE CONCENTRATION, IN MILLIGRAMS PER LITER AS P

EXPLANATION

SIMULATED STREAMFLOW

OBSERVED STREAMFLOW

SIMULATED DISSOLVED ORTHOPHOSPHATE

OBSERVED DISSOLVED ORTHOPHOSPHATE

1600 2400 0800 1600 2400 0800

7 8 9

July 1998

0

0.10

0.02

0.04

0.06

0.08

DISSOLVED ORTHOPHOSPHATE CONCENTRATION, IN MILLIGRAMS PER LITER AS P

0

250

50

100

150

200

1600 2400 0800 1600 2400 0800

7 8 9

October 1998

0

150

50

100

0

0.10

0.02

0.04

0.06

0.08

DISSOLVED ORTHOPHOSPHATE CONCENTRATION, IN MILLIGRAMS PER LITER AS P

2400 1200 2400 1200 2400 1200 2400

8 9 10

March 1998

0

300

100

200

0

0.10

0.02

0.04

0.06

0.08

DISSOLVED ORTHOPHOSPHATE CONCENTRATION, IN MILLIGRAMS PER LITER AS P

Figure 7. Simulated and observed streamflow and concentrations of dissolved orthophosphate during six storms in

1998 at streamflow-measurement station 01480095, Little Mill Creek near Newport, Del. STREAMFLOW, IN CUBIC FEET PER SECOND STREAMFLOW, IN CUBIC FEET PER SECOND STREAMFLOW, IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND
Appendix 2 117

2400 1200 2400 1200 2400 1200 2400

7 8 9

October 1998

0

0.25

0.05

0.10

0.15

0.20

DISSOLVED ORTHOPHOSPHATE CONCENTRATION, IN MILLIGRAMS PER LITER AS P

0

250

50

100

150

200

STREAMFLOW, IN CUBIC FEET PER SECOND

2400 1200 2400 1200 2400 1200 2400

8 9 10

March 1998

0

1,000

200

400

600

800

STREAMFLOW, IN CUBIC FEET PER SECOND

0

0.25

0.05

0.10

0.15

0.20

DISSOLVED ORTHOPHOSPHATE CONCENTRATION, IN MILLIGRAMS PER LITER AS P

2400 0800 1600 2400 0800 1600 2400

1 2

May 1998

0

0.25

0.05

0.10

0.15

0.20

DISSOLVED ORTHOPHOSPHATE CONCENTRATION, IN MILLIGRAMS PER LITER AS P

10

60

20

30

40

50

STREAMFLOW, IN CUBIC FEET PER SECOND

2400 1200 2400 1200 2400 1200 2400

11 12 13

June 1998

0

300

100

200

STREAMFLOW, IN CUBIC FEET PER SECOND

0

0.25

0.05

0.10

0.15

0.20

DISSOLVED ORTHOPHOSPHATE CONCENTRATION, IN MILLIGRAMS PER LITER AS P

2400 1200 2400 1200 2400 1200 2400

7 8 9

July 1998

0

0.25

0.05

0.10

0.15

0.20

DISSOLVED ORTHOPHOSPHATE CONCENTRATION, IN MILLIGRAMS PER LITER AS P

0

250

50

100

150

200

STREAMFLOW, IN CUBIC FEET PER SECOND

EXPLANATION

SIMULATED STREAMFLOW

OBSERVED STREAMFLOW

SIMULATED DISSOLVED ORTHOPHOSPHATE

OBSERVED DISSOLVED ORTHOPHOSPHATE

Figure 8. Simulated and observed streamflow and concentrations of dissolved orthophosphate during five storms in

1998 at streamflow-measurement station 01478000, Christina River at Coochs Bridge, Delaware.

Appendix 3 119

APPENDIX 3

USER CONTROL FILE
120 Appendix 3

RUN

GLOBAL

CHRISTINA RIVER HYDROLOGY - BASE SCENARIO - ALL SEGMENTS

 START 1994 10 1 0 0 END 1998 10 29 24 0

 RUN INTERP OUTPUT LEVEL 3 2

 RESUME 0 RUN 1 UNIT SYSTEM 1

END GLOBAL

FILES

<type> <UN#>***<------------fname--------------------------------------------->

WDM 26 christin.wdm

MESSU 25 christin.ech

 90 christin.out

END FILES

OPN SEQUENCE

 INGRP INDELT 1:00

 PERLND 502

 PERLND 503

 PERLND 504

 PERLND 505

 PERLND 506

 PERLND 507

 PERLND 508

 PERLND 509

 PERLND 510

 PERLND 511

 IMPLND 501

 IMPLND 502

 PERLND 802

 PERLND 803

 PERLND 804

 PERLND 805

 PERLND 806

 PERLND 807

 PERLND 808

 PERLND 809

 PERLND 810

 PERLND 811

 IMPLND 801

 IMPLND 802

 RCHRES 1

 RCHRES 2

 RCHRES 3

 GENER 1

 GENER 2

 COPY 11

 COPY 200

 RCHRES 6

 RCHRES 7

 PERLND 902

 PERLND 903

 PERLND 904

 PERLND 905

 PERLND 906

 PERLND 907

 PERLND 908

 PERLND 909

 PERLND 910

 PERLND 911

 IMPLND 901

 IMPLND 902

 RCHRES 4

 GENER 3

 GENER 4

 COPY 12

 COPY 300

 RCHRES 5

 COPY 400

 COPY 500

 END INGRP

END OPN SEQUENCE

PERLND

 ACTIVITY

 # # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ***

 502 911 1 1 1 1 1 1 1 0 0 0 0 0

 END ACTIVITY

 PRINT-INFO

 # # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *********

 502 911 5 5 5 5 5 5 5 0 0 0 0 0 0 12

 END PRINT-INFO

 GEN-INFO

 # # NAME NBLKS UCI IN OUT ENGL METR ***

 502 RESIDENTIAL-SEPTIC 1 1 1 1 90 0

 503 RESIDENTIAL-SEWER 1 1 1 1 90 0

 504 COMMERCIAL/INDUSTRY 1 1 1 1 90 0

 505 AGRICULTURAL-COWS 1 1 1 1 90 0
Appendix 3 121

 506 AGRICULTURAL-CROPS 1 1 1 1 90 0

 507 AGRICULTURAL-MUSHROOM 1 1 1 1 90 0

 508 FOREST 1 1 1 1 90 0

 509 OPEN LAND 1 1 1 1 90 0

 510 WETLANDS, WATER 1 1 1 1 90 0

 511 undesignated use 1 1 1 1 90 0

 802 RESIDENTIAL-SEPTIC 1 1 1 1 90 0

 803 RESIDENTIAL-SEWER 1 1 1 1 90 0

 804 COMMERCIAL/INDUSTRY 1 1 1 1 90 0

 805 AGRICULTURAL-COWS 1 1 1 1 90 0

 806 AGRICULTURAL-CROPS 1 1 1 1 90 0

 807 AGRICULTURAL-MUSHROOM 1 1 1 1 90 0

 808 FOREST 1 1 1 1 90 0

 809 OPEN LAND 1 1 1 1 90 0

 810 WETLANDS, WATER 1 1 1 1 90 0

 811 undesignated use 1 1 1 1 90 0

 902 RESIDENTIAL-SEPTIC 1 1 1 1 90 0

 903 RESIDENTIAL-SEWER 1 1 1 1 90 0

 904 COMMERCIAL/INDUSTRY 1 1 1 1 90 0

 905 AGRICULTURAL-COWS 1 1 1 1 90 0

 906 AGRICULTURAL-CROPS 1 1 1 1 90 0

 907 AGRICULTURAL-MUSHROOM 1 1 1 1 90 0

 908 FOREST 1 1 1 1 90 0

 909 OPEN LAND 1 1 1 1 90 0

 910 WETLANDS, WATER 1 1 1 1 90 0

 911 undesignated use 1 1 1 1 90 0

 END GEN-INFO

  AIR TEMPERATURE ** **

 ATEMP-DAT

 ELDAT AIRTMP ***

 # # (ft) (deg F) ***

 502 511 225.0 53.6

 802 811 0.0 53.6

 902 911 25.0 53.6

 END ATEMP-DAT

  SNOW ** **

 ICE-FLAG

*** <PLS > ICEFG

*** # #

 502 911 1

 END ICE-FLAG

 SNOW-PARM1

*** <PLS > LAT MELEV SHADE SNOWCF COVIND

*** # # (deg) (ft) (in)

 502 511 39.71 300. 0.20 1.0 0.50

 802 811 39.71 75. 0.20 1.0 0.50

 902 911 39.70 100. 0.20 1.0 0.50

 END SNOW-PARM1

 SNOW-PARM2

*** <PLS > RDSCN TSNOW SNOEVP CCFACT MWATER MGMELT

*** # # (degF) (in/day)

 502 511 0.08 32.0 0.05 0.60 0.50 0.010

 802 811 0.08 32.0 0.05 0.60 0.50 0.021

 902 911 0.08 32.0 0.05 0.60 0.50 0.021

 END SNOW-PARM2

  HYDROLOGY ** **

 PWAT-PARM1

*** <PLS > Flags

*** x - x CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE IFFC

 502 1 0 0 1 0 0 0 1 1 1

 503 1 0 0 1 0 0 0 1 1 1

 504 1 0 0 1 0 0 0 1 1 1

 505 1 0 0 1 0 0 0 1 1 1

 506 1 0 0 1 0 0 0 1 1 1

 507 1 0 0 1 0 0 0 1 1 1

 508 1 0 0 1 0 0 0 1 1 1

 509 1 0 0 1 0 0 0 1 1 1

 510 1 0 0 0 0 0 0 1 0 1

 511 1 0 0 1 0 0 0 1 1 1

 802 1 0 0 1 0 0 0 1 1 1

 803 1 0 0 1 0 0 0 1 1 1

 804 1 0 0 1 0 0 0 1 1 1

 805 1 0 0 1 0 0 0 1 1 1

 806 1 0 0 1 0 0 0 1 1 1

 807 1 0 0 1 0 0 0 1 1 1

 808 1 0 0 1 0 0 0 1 1 1

 809 1 0 0 1 0 0 0 1 1 1

 810 1 0 0 0 0 0 0 1 0 1

 811 1 0 0 1 0 0 0 1 1 1

 902 1 0 0 1 0 0 0 1 1 1

 903 1 0 0 1 0 0 0 1 1 1

 904 1 0 0 1 0 0 0 1 1 1

 905 1 0 0 1 0 0 0 1 1 1

 906 1 0 0 1 0 0 0 1 1 1
122 Appendix 3

 907 1 0 0 1 0 0 0 1 1 1

 908 1 0 0 1 0 0 0 1 1 1

 909 1 0 0 1 0 0 0 1 1 1

 910 1 0 0 0 0 0 0 1 0 1

 911 1 0 0 1 0 0 0 1 1 1

 END PWAT-PARM1

 PWAT-PARM2

*** <PLS> FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC

*** x - x (in) (in/hr) (ft) (1/in) (1/day)

 502 0.0 8.000 0.070 150.0 0.1837 0.000 0.985

 503 0.0 8.000 0.070 150.0 0.2095 0.000 0.985

 504 0.0 8.000 0.070 150.0 0.1502 0.000 0.985

 505 0.0 8.000 0.080 150.0 0.1591 0.000 0.985

 506 0.0 8.000 0.080 150.0 0.1591 0.000 0.985

 507 0.0 8.000 0.070 150.0 0.1591 0.000 0.985

 508 0.0 8.000 0.090 150.0 0.2025 0.000 0.985

 509 0.0 8.000 0.070 150.0 0.1672 0.000 0.985

 510 0.0 8.000 0.100 150.0 0.1235 0.000 0.985

 511 0.0 8.000 0.070 150.0 0.1143 0.000 0.985

 802 0.0 4.000 0.030 150.0 0.0977 0.000 0.986

 803 0.0 4.000 0.030 150.0 0.0706 0.000 0.986

 804 0.0 4.000 0.030 150.0 0.0798 0.000 0.986

 805 0.0 4.000 0.040 150.0 0.0626 0.000 0.986

 806 0.0 4.000 0.040 150.0 0.0626 0.000 0.986

 807 0.0 4.000 0.030 150.0 0.0626 0.000 0.986

 808 0.0 4.000 0.060 150.0 0.1014 0.000 0.986

 809 0.0 4.000 0.030 150.0 0.0689 0.000 0.986

 810 0.0 4.000 0.100 150.0 0.0683 0.000 0.986

 811 0.0 4.000 0.030 150.0 0.0599 0.000 0.986

 902 0.0 4.500 0.030 200.0 0.1062 0.000 0.980

 903 0.0 4.500 0.030 200.0 0.1078 0.000 0.980

 904 0.0 4.500 0.030 200.0 0.1382 0.000 0.980

 905 0.0 4.500 0.040 200.0 0.1253 0.000 0.980

 906 0.0 4.500 0.040 200.0 0.1253 0.000 0.980

 907 0.0 4.500 0.030 200.0 0.1253 0.000 0.980

 908 0.0 4.500 0.080 200.0 0.0536 0.000 0.980

 909 0.0 4.500 0.030 200.0 0.1819 0.000 0.980

 910 0.0 4.500 0.100 200.0 0.0857 0.000 0.980

 911 0.0 4.500 0.030 200.0 0.1244 0.000 0.980

 END PWAT-PARM2

 PWAT-PARM3

*** <PLS> PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP

*** x - x (deg F) (deg F)

 502 509 40.0 36.0 2.0 2.0 0.010 0.035 0.000

 510 40.0 36.0 2.0 2.0 0.010 0.035 0.300

 511 40.0 36.0 2.0 2.0 0.010 0.035 0.000

 802 809 40.0 36.0 2.0 2.0 0.000 0.010 0.000

 810 40.0 36.0 2.0 2.0 0.000 0.010 0.500

 811 40.0 36.0 2.0 2.0 0.000 0.010 0.000

 902 909 40.0 36.0 2.0 2.0 0.000 0.015 0.000

 910 40.0 36.0 2.0 2.0 0.000 0.015 0.500

 911 40.0 36.0 2.0 2.0 0.000 0.015 0.000

 END PWAT-PARM3

 PWAT-PARM4

*** <PLS > CEPSC UZSN NSUR INTFW IRC LZETP

*** x - x (in) (in) (1/day)

 502 0.050 0.700 0.35 0.9 0.500 0.600

 503 0.050 0.700 0.30 0.9 0.500 0.600

 504 0.050 0.600 0.25 0.9 0.500 0.600

 505 0.050 0.400 0.20 0.9 0.500 0.700

 506 0.050 0.400 0.30 0.9 0.500 0.700

 507 0.050 0.600 0.30 0.9 0.500 0.600

 508 0.100 1.000 0.35 0.9 0.500 0.800

 509 0.050 0.600 0.30 0.9 0.500 0.600

 510 0.050 1.000 0.05 0.9 0.500 0.900

 511 0.050 0.600 0.30 0.9 0.500 0.600

 802 0.050 0.800 0.35 1.3 0.500 0.600

 803 0.050 0.800 0.30 1.3 0.500 0.600

 804 0.050 0.700 0.25 1.3 0.500 0.600

 805 0.050 0.400 0.20 1.3 0.500 0.700

 806 0.050 0.400 0.30 1.3 0.500 0.700

 807 0.050 0.600 0.30 1.3 0.500 0.600

 808 0.100 1.100 0.35 1.3 0.500 0.800

 809 0.050 0.700 0.30 1.3 0.500 0.600

 810 0.050 1.000 0.05 1.3 0.500 0.900

 811 0.050 0.700 0.30 1.3 0.500 0.600

 902 0.050 0.800 0.35 2.5 0.500 0.600

 903 0.050 0.800 0.30 2.5 0.500 0.600

 904 0.050 0.700 0.25 2.5 0.500 0.600

 905 0.050 0.400 0.20 2.5 0.500 0.700

 906 0.050 0.400 0.30 2.5 0.500 0.700

 907 0.050 0.600 0.30 2.5 0.500 0.600

 908 0.100 1.200 0.35 2.5 0.500 0.800

 909 0.050 0.700 0.30 2.5 0.500 0.600

 910 0.050 1.000 0.05 2.5 0.500 0.900

 911 0.050 0.700 0.30 2.5 0.500 0.600

 END PWAT-PARM4

 MON-INTERCEP
Appendix 3 123

*** <PLS > Interception storage capacity at start of each month (in)

*** x - x JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

 502 504 .040 .040 .060 .080 .100 .100 .100 .100 .080 .060 .040 .040

 505 507 .030 .030 .030 .030 .060 .090 .110 .110 .110 .080 .070 .030

 508 .040 .040 .070 .110 .140 .160 .160 .150 .120 .090 .050 .040

 509 511 .040 .040 .060 .080 .100 .100 .100 .100 .080 .060 .050 .040

 802 804 .040 .040 .060 .080 .100 .100 .100 .100 .080 .060 .040 .040

 805 807 .030 .030 .030 .030 .060 .090 .110 .110 .110 .080 .070 .030

 808 .040 .040 .070 .110 .140 .160 .160 .150 .120 .090 .050 .040

 809 811 .040 .040 .060 .080 .100 .100 .100 .100 .080 .060 .050 .040

 902 904 .040 .040 .060 .080 .100 .100 .100 .100 .080 .060 .040 .040

 905 907 .030 .030 .030 .030 .060 .090 .110 .110 .110 .080 .070 .030

 908 .040 .040 .070 .110 .140 .160 .160 .150 .120 .090 .050 .040

 909 911 .040 .040 .060 .080 .100 .100 .100 .100 .080 .060 .050 .040

 END MON-INTERCEP

 MON-UZSN

*** <PLS > Upper zone storage at start of each month (inches)

*** x - x JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

 505 506 .400 .400 .400 .430 .450 .450 .400 .400 .400 .400 .400 .400

 805 806 .400 .400 .400 .430 .450 .450 .400 .400 .400 .400 .400 .400

 905 906 .400 .400 .400 .430 .450 .450 .400 .400 .400 .400 .400 .400

 END MON-UZSN

 MON-IRC

***

*** x - x JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

 502 911 0.4 0.4 0.5 0.5 0.5 0.5 0.5 0.5 0.6 0.6 0.7 0.4

 END MON-IRC

 MON-LZETPARM

*** <PLS > Lower zone evapotranspir parm at start of each month

*** x - x JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

 502 507 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.1 0.3 0.5 0.7

 508 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.2 0.4 0.6 0.8

 509 511 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.1 0.3 0.5 0.7

 802 807 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.1 0.3 0.5 0.7

 808 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.2 0.4 0.6 0.8

 809 811 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.1 0.3 0.5 0.7

 902 907 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.0 0.3 0.7 0.7

 908 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.0 0.4 0.8 0.8

 909 911 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.0 0.3 0.7 0.7

 END MON-LZETPARM

 PWAT-STATE1

*** <PLS> PWATER state variables (in)

*** x - x CEPS SURS UZS IFWS LZS AGWS GWVS

 502 0.0 0.0 .70 0.0 8.0 0.8 0.0

 503 0.0 0.0 .70 0.0 8.0 0.8 0.0

 504 0.0 0.0 .60 0.0 8.0 0.8 0.0

 505 0.0 0.0 .40 0.0 8.0 0.8 0.0

 506 0.0 0.0 .40 0.0 8.0 0.8 0.0

 507 0.0 0.0 .60 0.0 8.0 0.8 0.0

 508 0.0 0.0 1.00 0.0 8.0 0.8 0.0

 509 0.0 0.0 .60 0.0 8.0 0.8 0.0

 510 0.0 0.0 .90 0.0 8.0 0.8 0.0

 511 0.0 0.0 .60 0.0 8.0 0.8 0.0

 802 0.0 0.0 .80 0.0 4.0 0.7 0.0

 803 0.0 0.0 .80 0.0 4.0 0.7 0.0

 804 0.0 0.0 .70 0.0 4.0 0.7 0.0

 805 0.0 0.0 .40 0.0 4.0 0.7 0.0

 806 0.0 0.0 .40 0.0 4.0 0.7 0.0

 807 0.0 0.0 .70 0.0 4.0 0.7 0.0

 808 0.0 0.0 1.10 0.0 4.0 0.7 0.0

 809 0.0 0.0 .70 0.0 4.0 0.7 0.0

 810 0.0 0.0 .90 0.0 4.0 0.7 0.0

 811 0.0 0.0 .70 0.0 4.0 0.7 0.0

 902 0.0 0.0 .90 0.0 5.5 0.8 0.0

 903 0.0 0.0 .90 0.0 5.5 0.8 0.0

 904 0.0 0.0 .90 0.0 5.5 0.8 0.0

 905 0.0 0.0 .40 0.0 5.5 0.8 0.0

 906 0.0 0.0 .40 0.0 5.5 0.8 0.0

 907 0.0 0.0 .90 0.0 5.5 0.8 0.0

 908 0.0 0.0 1.20 0.0 5.5 0.8 0.0

 909 0.0 0.0 .90 0.0 5.5 0.8 0.0

 910 0.0 0.0 .90 0.0 5.5 0.8 0.0

 911 0.0 0.0 .90 0.0 5.5 0.8 0.0

 END PWAT-STATE1

 SED-PARM1

*** <PLS > Sediment parameters 1

*** x - x CRV VSIV SDOP

 502 911 1 0 1

 END SED-PARM1

 SED-PARM2

*** <PLS > SMPF KRER JRER AFFIX COVER NVSI

*** x - x (/day) lb/ac-day

 502 503 1.000 0.500 2.000 0.010 0.000 1.000

 504 1.000 0.500 2.000 0.010 0.000 1.000

 505 506 1.000 0.520 2.000 0.010 0.000 1.000

 507 1.000 0.520 2.000 0.010 0.000 1.000
124 Appendix 3

 508 1.000 0.450 2.000 0.002 0.000 2.000

 509 1.000 0.500 2.000 0.010 0.000 2.000

 510 1.000 0.400 2.000 0.002 0.000 2.000

 511 1.000 0.500 2.000 0.010 0.000 2.000

 802 803 1.000 0.450 2.000 0.010 0.000 1.000

 804 1.000 0.450 2.000 0.010 0.000 1.000

 805 806 1.000 0.500 2.000 0.010 0.000 1.000

 807 1.000 0.500 2.000 0.010 0.000 1.000

 808 1.000 0.400 2.000 0.002 0.000 2.000

 809 1.000 0.450 2.000 0.010 0.000 2.000

 810 1.000 0.400 2.000 0.002 0.000 2.000

 811 1.000 0.450 2.000 0.010 0.000 2.000

 902 903 1.000 0.450 2.000 0.010 0.000 1.000

 904 1.000 0.450 2.000 0.010 0.000 1.000

 905 907 1.000 0.450 2.000 0.010 0.000 1.000

 908 1.000 0.400 2.000 0.002 0.000 2.000

 909 1.000 0.450 2.000 0.010 0.000 2.000

 910 1.000 0.400 2.000 0.002 0.000 2.000

 911 1.000 0.450 2.000 0.010 0.000 2.000

 END SED-PARM2

 SED-PARM3

*** <PLS > Sediment parameter 3

*** x - x KSER JSER KGER JGER

 502 0.120 1.800 0.007 2.000

 503 0.160 1.800 0.010 2.000

 504 0.300 1.800 0.030 2.000

 505 506 1.650 1.800 0.025 2.000

 507 1.800 1.800 0.025 2.000

 508 0.080 1.800 0.000 2.000

 509 0.160 1.800 0.004 2.000

 510 0.005 1.800 0.000 2.000

 511 0.160 1.800 0.004 2.000

 802 0.100 2.000 0.005 2.000

 803 0.140 2.000 0.010 2.000

 804 0.285 2.000 0.020 2.000

 805 806 1.600 2.000 0.015 2.000

 807 1.500 2.000 0.015 2.000

 808 0.080 2.000 0.000 2.000

 809 0.140 2.000 0.004 2.000

 810 0.005 2.000 0.000 2.000

 811 0.140 2.000 0.004 2.000

 902 0.180 2.000 0.006 2.000

 903 0.450 2.000 0.012 2.000

 904 0.750 2.000 0.030 2.000

 905 907 1.800 2.000 0.020 2.000

 908 0.100 2.000 0.000 2.000

 909 0.200 2.000 0.010 2.000

 910 0.008 2.000 0.000 2.000

 911 0.200 2.000 0.010 2.000

 END SED-PARM3

 MON-COVER

*** <PLS > Monthly values for erosion related cover

*** x - x JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

 502 504 0.90 0.90 0.90 0.91 0.93 0.93 0.93 0.93 0.93 0.91 0.90 0.90

 505 507 0.50 0.45 0.00 0.00 0.10 0.50 0.75 0.93 0.93 0.85 0.70 0.55

 508 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97

 509 0.90 0.90 0.90 0.90 0.92 0.93 0.93 0.93 0.93 0.91 0.90 0.90

 510 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97

 511 0.90 0.90 0.90 0.90 0.92 0.93 0.93 0.93 0.93 0.91 0.90 0.90

 802 804 0.90 0.90 0.90 0.91 0.93 0.93 0.93 0.93 0.93 0.91 0.90 0.90

 805 807 0.50 0.45 0.00 0.00 0.10 0.50 0.75 0.93 0.93 0.85 0.70 0.55

 808 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97

 809 0.90 0.90 0.90 0.90 0.92 0.93 0.93 0.93 0.93 0.91 0.90 0.90

 810 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97

 811 0.90 0.90 0.90 0.90 0.92 0.93 0.93 0.93 0.93 0.91 0.90 0.90

 902 904 0.90 0.90 0.90 0.91 0.93 0.93 0.93 0.93 0.93 0.91 0.90 0.90

 905 907 0.50 0.45 0.00 0.00 0.10 0.50 0.75 0.93 0.93 0.85 0.70 0.55

 908 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97

 909 0.90 0.90 0.90 0.90 0.92 0.93 0.93 0.93 0.93 0.91 0.90 0.90

 910 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97

 911 0.90 0.90 0.90 0.90 0.92 0.93 0.93 0.93 0.93 0.91 0.90 0.90

 END MON-COVER

 SED-STOR

*** <PLS > Detached sediment storage (tons/acre)

*** x - x DETS

 502 911 0.4000

 END SED-STOR

 PSTEMP-PARM1

*** <PLS > Flags for section PSTEMP

*** x - x SLTV ULTV LGTV TSOP

 502 911 1 1 0 1

 END PSTEMP-PARM1

 PSTEMP-PARM2

PERLND *** ASLT BSLT ULTP1 ULTP2 LGTP1 LGTP2

 502 911 32.0 0.50 32.0 0.90 54.0 0.0

 END PSTEMP-PARM2
Appendix 3 125

 MON-ASLT

PERLND *** JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

 502 911 32.9 35.3 37.9 42.7 46.9 52.6 55.0 54.3 51.4 46.3 40.5 36.6

 END MON-ASLT

 MON-BSLT

PERLND *** JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

 502 911 0.23 0.23 0.23 0.23 0.23 0.23 0.23 0.23 0.23 0.23 0.23 0.23

 END MON-BSLT

 MON-ULTP1

PERLND *** JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

 502 911 40.0 41.0 43.0 46.0 48.6 52.8 56.8 57.8 53.5 48.8 45.0 42.0

 END MON-ULTP1

 MON-ULTP2

PERLND *** JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

 502 911 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10

 END MON-ULTP2

 PSTEMP-TEMPS

PERLND *** AIRTC SLTMP ULTMP LGTMP

 502 911 50.0 60.0 57.0 53.0

 END PSTEMP-TEMPS

 PWT-PARM2

PERLND *** ELEV IDOXP ICO2P ADOXP ACO2P

 502 511 250. 8.80 0 8.80 0

 802 811 75. 8.80 0 8.80 0

 902 911 150. 8.80 0 8.80 0

 END PWT-PARM2

 MON-IFWDOX

PERLND *** JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

 502 911 11.0 10.0 10.0 10.0 9.00 7.00 6.00 6.00 7.00 9.00 10.0 11.0

 END MON-IFWDOX

 MON-GRNDDOX

PERLND *** JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

 502 911 11.0 10.0 10.0 10.0 9.00 7.00 6.00 6.00 7.00 9.00 10.0 11.0

 END MON-GRNDDOX

 PWT-TEMPS

PERLND *** SOTMP IOTMP AOTMP

 502 911 60. 57. 53.

 END PWT-TEMPS

 PWT-GASES

PERLND *** SODOX SOCO2 IODOX IOCO2 AODOX AOCO2

 502 911 8.8 0 8.8 0 8.8 0

 END PWT-GASES

*** Water Quality Constituents N and P ***

 NQUALS

 # # NQAL ***

 502 911 5

 END NQUALS

 QUAL-PROPS

 # #<--QUALID--> QTID QSD VPFW VPFS QSO VQO QIFW VIQC QAGW VAQC ***

 502 911 NO3 LBS 1 2 0 0 0 1 4 1 4

 END QUAL-PROPS

 QUAL-INPUT

 # # SQO POTFW POTFS ACQOP SQOLIM WSQOP IOQC AOQC ***

 502 0.100 1. 1. 0.0274 0.5000 0.500 1. 1. ***

 503 0.100 1. 1. 0.0274 0.5000 0.500 1. 1. ***

 504 0.100 1. 1. 0.0274 0.5000 0.500 1. 1. ***

 505 0.100 1. 1. 0.0411 0.7500 0.500 1. 1. ***

 506 0.100 1. 1. 0.0411 0.7500 0.500 1. 1. ***

 507 0.100 1. 1. 0.0411 0.7500 0.500 1. 1. ***

 508 0.100 1. 1. 0.0137 0.2500 0.500 1. 1. ***

 509 0.100 1. 1. 0.0274 0.5000 0.500 1. 1. ***

 510 0.100 1. 1. 0.0137 0.2500 0.500 1. 1. ***

 511 0.100 1. 1. 0.0274 0.5000 0.500 1. 1. ***

 902 0.100 1. 1. 0.0274 0.5000 0.500 1. 1. ***

 903 0.100 1. 1. 0.0274 0.5000 0.500 1. 1. ***

 904 0.100 1. 1. 0.0274 0.5000 0.500 1. 1. ***

 905 0.100 1. 1. 0.0411 0.7500 0.500 1. 1. ***

 906 0.100 1. 1. 0.0411 0.7500 0.500 1. 1. ***

 907 0.100 1. 1. 0.0411 0.7500 0.500 1. 1. ***

 908 0.100 1. 1. 0.0137 0.2500 0.500 1. 1. ***

 909 0.100 1. 1. 0.0274 0.5000 0.500 1. 1. ***

 910 0.100 1. 1. 0.0137 0.2500 0.500 1. 1. ***

 911 0.100 1. 1. 0.0274 0.5000 0.500 1. 1. ***

 802 0.100 1. 1. 0.0274 0.5000 0.500 1. 1. ***

 803 0.100 1. 1. 0.0274 0.5000 0.500 1. 1. ***

 804 0.100 1. 1. 0.0274 0.5000 0.500 1. 1. ***

 805 0.100 1. 1. 0.0411 0.7500 0.500 1. 1. ***

 806 0.100 1. 1. 0.0411 0.7500 0.500 1. 1. ***

 807 0.100 1. 1. 0.0411 0.7500 0.500 1. 1. ***

 808 0.100 1. 1. 0.0137 0.2500 0.500 1. 1. ***

 809 0.100 1. 1. 0.0274 0.5000 0.500 1. 1. ***
126 Appendix 3

 810 0.100 1. 1. 0.0137 0.2500 0.500 1. 1. ***

 811 0.100 1. 1. 0.0274 0.5000 0.500 1. 1. ***

 END QUAL-INPUT

 MON-POTFW

 Potency factors for NO3 (lb NO3-N/ton sediment) ***

 # # JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ***

 502 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5

 902 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5

 802 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5

 503 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4

 903 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4

 803 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4

 504 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2

 904 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2

 804 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2

 505 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8

 905 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8

 805 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8

 506 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8

 906 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8

 806 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8

 507 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8

 907 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8

 807 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8

 508 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1.

 908 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1.

 808 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1.

 509 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1.

 909 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1.

 809 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1.

 510 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1.

 910 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1.

 810 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1.

 511 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1.

 911 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1.

 811 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1.

 END MON-POTFW

 MON-IFLW-CONC

 Interflow concentration of NO3-N (mg/l) ***

 # # JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ***

 502 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5

 902 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5

 802 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5

 503 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8

 903 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8

 803 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8

 504 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8

 904 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8

 804 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8

 505 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0

 905 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0

 805 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0

 506 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0

 906 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0

 806 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0

 507 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0

 907 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0

 807 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0

 508 .400 .400 .400 .350 .350 .300 .300 .250 .300 .300 .350 .400

 908 .400 .400 .400 .350 .350 .300 .300 .250 .300 .300 .350 .400

 808 .400 .400 .400 .350 .350 .300 .300 .250 .300 .300 .350 .400

 509 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2

 909 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2

 809 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2

 510 .700 .680 .600 .570 .530 .470 .430 .360 .430 .500 .570 .640

 910 .700 .680 .600 .570 .530 .470 .430 .360 .430 .500 .570 .640

 810 .700 .680 .600 .570 .530 .470 .430 .360 .430 .500 .570 .640

 511 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2

 911 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2

 811 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2

 END MON-IFLW-CONC

 MON-GRND-CONC

 Active groundwater concentration of NO3-N (mg/l) ***

 # # JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ***

 502 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5

 902 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5

 802 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5

 503 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8

 903 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8

 803 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8

 504 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8

 904 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8

 804 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8

 505 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0

 905 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0

 805 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0

 506 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0

 906 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0

 806 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0
Appendix 3 127

 507 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0

 907 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0

 807 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0

 508 .400 .400 .400 .350 .350 .300 .300 .250 .300 .300 .350 .400

 908 .400 .400 .400 .350 .350 .300 .300 .250 .300 .300 .350 .400

 808 .400 .400 .400 .350 .350 .300 .300 .250 .300 .300 .350 .400

 509 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2

 909 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2

 809 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2

 510 .700 .680 .600 .570 .530 .470 .430 .360 .430 .500 .570 .640

 910 .700 .680 .600 .570 .530 .470 .430 .360 .430 .500 .570 .640

 810 .700 .680 .600 .570 .530 .470 .430 .360 .430 .500 .570 .640

 511 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2

 911 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2

 811 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2

 END MON-GRND-CONC

 QUAL-PROPS

 # #<--QUALID--> QTID QSD VPFW VPFS QSO VQO QIFW VIQC QAGW VAQC ***

 502 911 NH4 LBS 1 2 0 0 0 1 4 1 4

 END QUAL-PROPS

 MON-POTFW

 Potency factors for NH4 (lb NH4-N/ton sediment) ***

 # # JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ***

 502 .24 .24 .24 .24 .24 .24 .24 .24 .24 .24 .24 .24

 902 .24 .24 .24 .24 .24 .24 .24 .24 .24 .24 .24 .24

 802 .24 .24 .24 .24 .24 .24 .24 .24 .24 .24 .24 .24

 503 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10

 903 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10

 803 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10

 504 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10

 904 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10

 804 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10

 505 .40 .40 .40 .40 .40 .40 .40 .40 .40 .40 .40 .40

 905 .40 .40 .40 .40 .40 .40 .40 .40 .40 .40 .40 .40

 805 .30 .30 .30 .30 .30 .30 .30 .30 .30 .30 .30 .30

 506 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25

 906 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25

 806 .15 .15 .15 .15 .15 .15 .15 .15 .15 .15 .15 .15

 507 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5

 907 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5

 807 .95 .95 .95 .95 .95 .95 .95 .95 .95 .95 .95 .95

 508 .002 .002 .002 .002 .002 .002 .002 .002 .002 .002 .002 .002

 908 .002 .002 .002 .002 .002 .002 .002 .002 .002 .002 .002 .002

 808 .002 .002 .002 .002 .002 .002 .002 .002 .002 .002 .002 .002

 509 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10

 909 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10

 809 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10

 510 .002 .002 .002 .002 .002 .002 .002 .002 .002 .002 .002 .002

 910 .002 .002 .002 .002 .002 .002 .002 .002 .002 .002 .002 .002

 810 .002 .002 .002 .002 .002 .002 .002 .002 .002 .002 .002 .002

 511 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10

 911 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10

 811 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10

 END MON-POTFW

 MON-IFLW-CONC

 Interflow concentration of NH4-N (mg/l) ***

 # # JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ***

 502 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027

 902 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027

 802 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027

 503 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015

 903 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015

 803 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015

 504 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015

 904 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015

 804 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015

 505 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028

 905 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028

 805 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028

 506 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028

 906 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028

 806 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028

 507 .100 .100 .100 .100 .100 .100 .100 .100 .100 .100 .100 .100

 907 .150 .150 .150 .150 .150 .150 .150 .150 .150 .150 .150 .150

 807 .080 .080 .080 .080 .080 .080 .080 .080 .080 .080 .080 .080

 508 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010

 908 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010

 808 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010

 509 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027

 909 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027

 809 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027

 510 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010

 910 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010

 810 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010

 511 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027

 911 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027

 811 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027

 END MON-IFLW-CONC
128 Appendix 3

 MON-GRND-CONC

 Active groundwater concentration of NH4-N (mg/l) ***

 # # JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ***

 502 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027

 902 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027

 802 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027

 503 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015

 903 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015

 803 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015

 504 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015

 904 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015

 804 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015 .015

 505 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028

 905 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028

 805 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028

 506 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028

 906 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028

 806 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028 .028

 507 .060 .060 .060 .060 .060 .060 .060 .060 .060 .060 .060 .060

 907 .060 .060 .060 .060 .060 .060 .060 .060 .060 .060 .060 .060

 807 .050 .050 .050 .050 .050 .050 .050 .050 .050 .050 .050 .050

 508 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010

 908 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010

 808 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010

 509 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027

 909 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027

 809 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027

 510 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010

 910 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010

 810 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010

 511 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027

 911 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027

 811 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027 .027

 END MON-GRND-CONC

 QUAL-PROPS

 # #<--QUALID--> QTID QSD VPFW VPFS QSO VQO QIFW VIQC QAGW VAQC ***

 502 911 PO4 LBS 1 2 0 0 0 1 4 1 4

 END QUAL-PROPS

 MON-POTFW

 Potency factors for PO4 (lb PO4-P/ton sediment) ***

 # # JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ***

 502 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6

 902 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6

 802 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6

 503 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6

 903 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6

 803 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6

 504 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6

 904 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6

 804 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6

 505 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0

 905 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0

 805 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0

 506 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0

 906 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0

 806 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0

 507 14. 14. 14. 14. 14. 14. 14. 14. 14. 14. 14. 14.

 907 14. 14. 14. 14. 14. 14. 14. 14. 14. 14. 14. 14.

 807 14. 14. 14. 14. 14. 14. 14. 14. 14. 14. 14. 14.

 508 .010 .010 .010 .010 .010 .025 .035 .035 .025 .010 .010 .010

 908 .010 .010 .010 .010 .010 .025 .035 .035 .025 .010 .010 .010

 808 .010 .010 .010 .010 .010 .025 .035 .035 .025 .010 .010 .010

 509 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8

 909 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8

 809 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8

 510 .020 .020 .020 .020 .020 .025 .035 .035 .035 .020 .020 .020

 910 .020 .020 .020 .020 .020 .025 .035 .035 .025 .020 .020 .020

 810 .020 .020 .020 .020 .020 .025 .035 .035 .025 .020 .020 .020

 511 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8

 911 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8

 811 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8

 END MON-POTFW

 MON-IFLW-CONC

 Interflow concentration of PO4-P (mg/l) ***

 # # JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ***

 502 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025

 902 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025

 802 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025

 503 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025

 903 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025

 803 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025

 504 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025

 904 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025

 804 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025

 505 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040

 905 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040

 805 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040

 506 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040

 906 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040
Appendix 3 129

 806 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040

 507 .120 .120 .120 .120 .120 .120 .120 .120 .120 .120 .120 .120

 907 .120 .120 .120 .120 .120 .120 .120 .120 .120 .120 .120 .120

 807 .120 .120 .120 .120 .120 .120 .120 .120 .120 .120 .120 .120

 508 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005

 908 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005

 808 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005

 509 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010

 909 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010

 809 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010

 510 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005

 910 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005

 810 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005

 511 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010

 911 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010

 811 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010

 END MON-IFLW-CONC

 MON-GRND-CONC

 Active groundwater concentration of PO4-P (mg/l) ***

 # # JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ***

 502 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025

 902 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025

 802 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025

 503 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025

 903 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025

 803 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025

 504 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025

 904 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025

 804 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025 .025

 505 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040

 905 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040

 805 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040

 506 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040

 906 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040

 806 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040 .040

 507 .060 .060 .060 .060 .060 .060 .060 .060 .060 .060 .060 .060

 907 .060 .060 .060 .060 .060 .060 .060 .060 .060 .060 .060 .060

 807 .060 .060 .060 .060 .060 .060 .060 .060 .060 .060 .060 .060

 508 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005

 908 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005

 808 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005

 509 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010

 909 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010

 809 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010

 510 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005

 910 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005

 810 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005 .005

 511 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010

 911 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010

 811 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010 .010

 END MON-GRND-CONC

 QUAL-PROPS

 # #<--QUALID--> QTID QSD VPFW VPFS QSO VQO QIFW VIQC QAGW VAQC ***

 502 911 BOD LBS 1 2 0 0 0 1 4 1 4

 END QUAL-PROPS

 MON-POTFW

 Potency factors for BOD (lb BOD/ton sediment) ***

 # # JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ***

 502 25. 25. 25. 25. 25. 25. 25. 25. 25. 25. 25. 25.

 902 25. 25. 25. 25. 25. 25. 25. 25. 25. 25. 25. 25.

 402 25. 25. 25. 25. 25. 25. 25. 25. 25. 25. 25. 25.

 503 20. 20. 20. 20. 20. 20. 20. 20. 20. 20. 20. 20.

 903 20. 20. 20. 20. 20. 20. 20. 20. 20. 20. 20. 20.

 803 20. 20. 20. 20. 20. 20. 20. 20. 20. 20. 20. 20.

 504 20. 20. 20. 20. 20. 20. 20. 20. 20. 20. 20. 20.

 904 20. 20. 20. 20. 20. 20. 20. 20. 20. 20. 20. 20.

 804 20. 20. 20. 20. 20. 20. 20. 20. 20. 20. 20. 20.

 505 35. 35. 35. 35. 35. 35. 35. 35. 35. 35. 35. 35.

 905 35. 35. 35. 35. 35. 35. 35. 35. 35. 35. 35. 35.

 805 35. 35. 35. 35. 35. 35. 35. 35. 35. 35. 35. 35.

 506 35. 35. 35. 35. 35. 35. 35. 35. 35. 35. 35. 35.

 906 35. 35. 35. 35. 35. 35. 35. 35. 35. 35. 35. 35.

 806 35. 35. 35. 35. 35. 35. 35. 35. 35. 35. 35. 35.

 507 35. 35. 35. 35. 35. 35. 35. 35. 35. 35. 35. 35.

 907 35. 35. 35. 35. 35. 35. 35. 35. 35. 35. 35. 35.

 807 35. 35. 35. 35. 35. 35. 35. 35. 35. 35. 35. 35.

 508 8.5 8.5 8.5 8.5 8.5 5.5 5.5 5.5 5.5 8.5 8.5 8.5

 908 8.5 8.5 8.5 8.5 8.5 5.5 5.5 5.5 5.5 8.5 8.5 8.5

 808 8.5 8.5 8.5 8.5 8.5 5.5 5.5 5.5 5.5 8.5 8.5 8.5

 509 20. 20. 20. 20. 20. 20. 20. 20. 20. 20. 20. 20.

 909 20. 20. 20. 20. 20. 20. 20. 20. 20. 20. 20. 20.

 809 20. 20. 20. 20. 20. 20. 20. 20. 20. 20. 20. 20.

 510 8.5 8.5 8.5 8.5 8.5 5.5 5.5 5.5 5.5 8.5 8.5 8.5

 910 8.5 8.5 8.5 8.5 8.5 5.5 5.5 5.5 5.5 8.5 8.5 8.5

 810 8.5 8.5 8.5 8.5 8.5 5.5 5.5 5.5 5.5 8.5 8.5 8.5

 511 20. 20. 20. 20. 20. 20. 20. 20. 20. 20. 20. 20.

 911 20. 20. 20. 20. 20. 20. 20. 20. 20. 20. 20. 20.

 811 20. 20. 20. 20. 20. 20. 20. 20. 20. 20. 20. 20.

 END MON-POTFW
130 Appendix 3

 MON-IFLW-CONC

 Interflow concentration of BOD (mg/l) ***

 # # JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ***

 502 .65 .65 .65 .65 .65 .65 .65 .65 .65 .65 .65 .65

 902 .65 .65 .65 .65 .65 .65 .65 .65 .65 .65 .65 .65

 802 .65 .65 .65 .65 .65 .65 .65 .65 .65 .65 .65 .65

 503 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 903 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 803 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 504 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 904 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 804 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 505 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2.

 905 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2.

 805 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2.

 506 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2.

 906 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2.

 806 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2.

 507 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2.

 907 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2.

 807 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2.

 508 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5

 908 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5

 808 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5

 509 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 909 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 809 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 510 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1

 910 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1

 810 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1

 511 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 911 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 811 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 END MON-IFLW-CONC

 MON-GRND-CONC

 Active groundwater concentration of BOD (mg/l) ***

 # # JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ***

 502 .65 .65 .65 .65 .65 .65 .65 .65 .65 .65 .65 .65

 902 .65 .65 .65 .65 .65 .65 .65 .65 .65 .65 .65 .65

 802 .65 .65 .65 .65 .65 .65 .65 .65 .65 .65 .65 .65

 503 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 903 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 803 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 504 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 904 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 804 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 505 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2.

 905 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2.

 805 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2.

 506 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2.

 906 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2.

 806 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2.

 507 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2.

 907 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2.

 807 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2. 2.

 508 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5

 908 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5

 808 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5

 509 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 909 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 809 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 510 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1

 910 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1

 810 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1

 511 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 911 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 811 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 END MON-GRND-CONC

 QUAL-PROPS

 # #<--QUALID--> QTID QSD VPFW VPFS QSO VQO QIFW VIQC QAGW VAQC ***

 502 911 ORGN LBS 1 1 0 0 0 1 4 1 4

 END QUAL-PROPS

 MON-POTFW

 Potency factors for ORGN (lb ORGN/ton sediment) ***

 502 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0

 902 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0

 802 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0

 503 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3

 903 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3

 803 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1.

 504 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1.

 904 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1.

 804 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1.

 505 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0

 905 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0

 805 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0

 506 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0

 306 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0
Appendix 3 131

 806 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0

 507 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0

 907 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0

 807 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0

 508 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0

 908 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0

 808 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0

 509 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0

 909 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0

 809 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0

 510 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0

 910 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0

 810 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0

 511 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0

 911 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0

 811 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0

 END MON-POTFW

 MON-IFLW-CONC

 Interflow concentration of ORGN (mg/l) ***

 # # JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ***

 502 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25

 902 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25

 802 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25

 503 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2

 903 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2

 803 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2

 504 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2

 904 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2

 804 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2

 505 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 905 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 805 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 506 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 906 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 806 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 507 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 907 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 807 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6

 508 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2

 908 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2

 808 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2 .2

 509 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25

 909 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25

 809 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25

 510 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1

 910 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1

 810 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1 .1

 511 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25

 911 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25

 811 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25 .25

 END MON-IFLW-CONC

 MON-GRND-CONC

 Active groundwater concentration of ORGN (mg/l) ***

 # # JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ***

 502 811 .15 .15 .15 .15 .15 .15 .15 .15 .15 .15 .15 .15

 END MON-GRND-CONC

END PERLND

IMPLND

 ACTIVITY

 # # ATMP SNOW IWAT SLD IWG IQAL ***

 501 902 1 1 1 1 1 1

 END ACTIVITY

 PRINT-INFO

 # # ATMP SNOW IWAT SLD IWG IQAL PIVL PYR ***

 501 902 5 5 5 5 5 5 0 12

 END PRINT-INFO

 GEN-INFO

 # # NAME UCI IN OUT ENGL METR ***

 501 ROADS,BUILDING-resid 1 1 1 90 0

 502 ROADS,BUILDING-urban 1 1 1 90 0

 801 ROADS,BUILDING-resid 1 1 1 90 0

 802 ROADS,BUILDING-urban 1 1 1 90 0

 901 ROADS,BUILDING-resid 1 1 1 90 0

 902 ROADS,BUILDING-urban 1 1 1 90 0

 END GEN-INFO

  AIR TEMPERATURE ** **

 ATEMP-DAT

 ELDAT AIRTMP ***

 # # (ft) (deg F) ***

 501 502 225.0 53.6

 801 802 0.0 53.6

 901 902 25.0 53.6

 END ATEMP-DAT
132 Appendix 3

  SNOW ** **

 ICE-FLAG

*** <ILS > ICEFG

*** # #

 501 902 1

 END ICE-FLAG

 SNOW-PARM1

*** <ILS > LAT MELEV SHADE SNOWCF COVIND

*** # # (deg) (ft) (in)

 501 502 39.71 300. 0.20 1.0 0.50

 801 802 39.71 75. 0.20 1.0 0.50

 901 902 39.70 100. 0.20 1.0 0.50

 END SNOW-PARM1

 SNOW-PARM2

*** <ILS > RDSCN TSNOW SNOEVP CCFACT MWATER MGMELT

*** # # (degF) (in/day)

 501 502 0.08 32.0 0.05 0.60 0.50 0.050

 801 802 0.08 32.0 0.05 0.60 0.50 0.050

 901 902 0.08 32.0 0.05 0.60 0.50 0.050

 END SNOW-PARM2

  HYDROLOGY ** **

 IWAT-PARM1

*** <ILS > Flags

*** x - x CSNO RTOP VRS VNN RTLI

 501 802 1 1 1 0 0

 901 902 1 1 1 0 0

 END IWAT-PARM1

 IWAT-PARM2

*** <ILS > LSUR SLSUR NSUR RETSC

*** x - x (ft) (in)

 501 150.0 0.197 0.07 0.0

 502 150.0 0.150 0.05 0.0

 801 150.0 0.084 0.07 0.0

 802 150.0 0.080 0.05 0.0

 901 150.0 0.110 0.07 0.0

 902 150.0 0.138 0.05 0.0

 END IWAT-PARM2

 IWAT-PARM3

*** <ILS > PETMAX PETMIN

*** x - x (deg F) (deg F)

 501 902 40.0 35.0

 END IWAT-PARM3

 MON-RETN

*** <ILS > Retention storage capacity at start of each month (in)

*** x - x JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

 501 802 .03 .03 .04 .04 .04 .06 .06 .06 .04 .04 .04 .03

 901 902 .08 .08 .08 .08 .10 .12 .15 .15 .12 .10 .08 .08

 END MON-RETN

 IWAT-STATE1

*** <ILS > IWATER state variables (inches)

*** x - x RETS SURS

 501 902 0.0 0.0

 END IWAT-STATE1

 SLD-PARM1

*** <ILS > Flags

*** x - x VASD VRSD SDOP

 501 902 0 0 1

 END SLD-PARM1

 SLD-PARM2

IMPLND *** KEIM JEIM ACCSDP REMSDP

 501 1.0 1.2 0.0006 0.08

 502 1.0 1.2 0.0035 0.08

 801 1.0 1.2 0.0006 0.08

 802 1.0 1.2 0.0035 0.08

 901 1.0 1.2 0.0006 0.08

 902 1.0 1.2 0.0035 0.08

 END SLD-PARM2

 SLD-STOR

IMPLND *** SLDS

 501 902 0.05

 END SLD-STOR

 IWT-PARM1

*** <ILS > Flags for section IWTGAS

*** x - x WTFV CSNO

 501 902 1 1

 END IWT-PARM1

*** WATER QUALITY CONSTITUENTS ***
Appendix 3 133

 NQUALS

 # # NQAL ***

 501 502 4

 901 902 4

 801 802 4

 END NQUALS

 QUAL-PROPS

 # #<--QUALID--> QTID QSD VPFW QSO VQO ***

 501 502 NO3 LBS 0 0 1 0

 901 902 NO3 LBS 0 0 1 0

 801 802 NO3 LBS 0 0 1 0

 END QUAL-PROPS

 QUAL-INPUT

 # # SQO POTFW ACQOP SQOLIM WSQOP ***

 501 502 0.050 0.0060 0.4000 0.500

 901 902 0.050 0.0060 0.4000 0.500

 801 802 0.050 0.0060 0.4000 0.500

 END QUAL-INPUT

 QUAL-PROPS

 # #<--QUALID--> QTID QSD VPFW QSO VQO ***

 501 502 NH4 LBS 1 0 1 0

 901 902 NH4 LBS 1 0 1 0

 801 802 NH4 LBS 1 0 1 0

 END QUAL-PROPS

 QUAL-INPUT

 # # SQO POTFW ACQOP SQOLIM WSQOP ***

 501 502 0.020 0.1 0.0010 0.1200 0.500

 901 902 0.020 0.1 0.0010 0.1200 0.500

 801 802 0.020 0.1 0.0010 0.1200 0.500

 END QUAL-INPUT

 QUAL-PROPS

 # #<--QUALID--> QTID QSD VPFW QSO VQO ***

 501 502 PO4 LBS 1 0 1 0

 901 902 PO4 LBS 1 0 1 0

 801 802 PO4 LBS 1 0 1 0

 END QUAL-PROPS

 QUAL-INPUT

 # # SQO POTFW ACQOP SQOLIM WSQOP ***

 501 0.010 1.2 0.0006 0.0090 0.500

 502 0.010 1.0 0.0004 0.0090 0.500

 901 0.010 1.2 0.0006 0.0090 0.500

 902 0.010 1.0 0.0004 0.0090 0.500

 801 0.010 1.2 0.0006 0.0090 0.500

 802 0.010 1.0 0.0004 0.0090 0.500

 END QUAL-INPUT

 QUAL-PROPS

 # #<--QUALID--> QTID QSD VPFW QSO VQO ***

 501 502 BOD LBS 0 0 1 0

 901 902 BOD LBS 0 0 1 0

 801 802 BOD LBS 0 0 1 0

 END QUAL-PROPS

 QUAL-INPUT

 # # SQO POTFW ACQOP SQOLIM WSQOP ***

 501 502 1.900 0.3600 9.0000 0.500

 901 902 1.900 0.3600 9.0000 0.500

 801 802 1.900 0.3600 9.0000 0.500

END QUAL-INPUT

 IWT-PARM2

IMPLND *** ELEV AWTF BWTF

 501 502 250. 34.0 0.3

 801 802 75. 34.0 0.3

 901 902 150. 34.0 0.3

 END IWT-PARM2

 MON-AWTF

IMPLND *** JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

 501 902 32.9 36.0 39.1 45.1 50.3 57.4 60.4 59.6 55.9 49.5 42.4 37.4

 END MON-AWTF

 MON-BWTF

IMPLND *** JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

 501 902 0.38 0.38 0.38 0.38 0.38 0.38 0.38 0.38 0.38 0.38 0.38 0.38

 END MON-BWTF

 IWT-INIT

*** <ILS > SOTMP SODOX SOCO2

*** x - x(deg F) (mg/l) (mg C/l)

 501 902 55.

 END IWT-INIT

END IMPLND

RCHRES

 ACTIVITY
134 Appendix 3

 RCHRES Active Sections (1=Active; 0=Inactive) ***

 # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG ***

 1 7 1 1 0 1 1 0 1 1 1 0

 END ACTIVITY

 PRINT-INFO

 RCHRES Print-flags ***

 # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ***

 1 7 5 5 5 5 5 5 5 12

 END PRINT-INFO

 GEN-INFO

 RCHRES<-------Name------->Nexit Unit Systems Printer ***

 # - # User t-series Engl Metr LKFG ***

 in out ***

 1 WEST BRANCH 1 1 1 1 90 0 0

 2 EAST BR-WEST BR 1 1 1 1 90 0 0

 3 MS-COOCHS GAGE 1 1 1 1 90 0 0

 4 LTL MILL-NEWPORT GA 1 1 1 1 90 0 0

 5 NEWPORT GA-CHRSTINA 1 1 1 1 90 0 0

 6 MUDDY RUN 1 1 1 1 90 0 0

 7 BELLTOWN RUN 1 1 1 1 90 0 0

 END GEN-INFO

  HYDRAULICS

 HYDR-PARM1

 RCHRES VC A1 A2 A3 ODFVFG for each ** * ODGTFG for each FUNCT for each

 # - # FG FG FG FG possible exit *** possible exit possible exit

 1 5 0 1 1 1 4 0 0 0 0 0 0 0 0 0 1 1 1 1 1

 6 0 1 1 1 4 0 0 0 0 0 0 0 0 0 1 1 1 1 1

 7 0 1 1 1 4 0 0 0 0 0 0 0 0 0 1 1 1 1 1

 END HYDR-PARM1

 HYDR-PARM2

 RCHRES FTABNO LEN DELTH STCOR KS DB50 ***

 # - # (miles) (ft) (ft) (in) ***

 1 1 4.79 201.0 0.0 0.5 0.01

 2 2 8.16 221.0 0.0 0.5 0.01

 3 3 3.24 51.0 0.0 0.5 0.01

 4 4 4.65 183.0 0.0 0.5 0.01

 5 5 2.30 63.0 0.0 0.5 0.01

 6 6 6.73 91.0 0.0 0.5 0.01

 7 7 2.08 46.0 0.0 0.5 0.01

 END HYDR-PARM2

 HYDR-INIT

 RCHRES VOL *** Initial value of COLIND Initial value of OUTDGT

 # - # ac-ft *** for each exit for each exit (ft3)

 1 0.75 4.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

 2 1.99 4.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

 3 2.17 4.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

 4 0.76 4.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

 5 0.75 4.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

 6 2.00 4.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

 7 0.44 4.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

 END HYDR-INIT

 HT-BED-FLAGS

RCHRES *** BDFG TGFG TSTP

 1 7 1 3

 END HT-BED-FLAGS

 HEAT-PARM

RCHRES *** ELEV ELDAT CFSAEX KATRAD KCOND KEVAP

 1 150. 75. .50 9.4 10.0 2.2

 2 250. 175. .50 9.4 10.0 2.2

 3 55. -20. .50 9.4 10.0 2.2

 4 130. 55. .50 9.4 10.0 2.2

 5 7 50. -25. .50 9.4 10.0 2.2

 END HEAT-PARM

 HT-BED-PARM

RCHRES *** MUDDEP TGRND KMUD KGRND

 1 7 0.01 59. 50 0.0

 END HT-BED-PARM

 MON-HT-TGRND

RCHRES *** JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

 1 7 39.0 43.0 46.5 55.0 59.5 67.0 74.5 75.0 74.0 63.5 53.0 44.0

 END MON-HT-TGRND

 HEAT-INIT

RCHRES *** TW AIRTMP

 1 7 59. 50.

 END HEAT-INIT

 SANDFG

*** RCHRES

*** x - x SNDFG

 1 7 3
Appendix 3 135

 END SANDFG

 SED-GENPARM

RCHRES *** BEDWID BEDWRN POR

 1 7 25. 6. 0.8

 END SED-GENPARM

 SAND-PM

RCHRES *** D W RHO KSAND EXPSND

 1 7 .005 0.1 2.6 0.10 3.92

 END SAND-PM

 SILT-CLAY-PM

RCHRES *** D W RHO TAUCD TAUCS M

 1 0.00040 0.0003 2.2 0.18 0.65 0.90

 2 0.00040 0.0003 2.2 0.18 0.55 0.90

 3 0.00040 0.0003 2.2 0.18 0.50 0.90

 4 0.00040 0.0003 2.2 0.20 0.65 0.90

 5 0.00040 0.0003 2.2 0.18 0.58 0.90

 6 0.00040 0.0003 2.2 0.12 0.30 0.90

 7 0.00040 0.0003 2.2 0.18 0.53 0.90

 END SILT-CLAY-PM

 SILT-CLAY-PM

RCHRES *** D W RHO TAUCD TAUCS M

 1 0.00010 0.00001 2.0 0.15 0.68 0.90

 2 0.00010 0.00001 2.0 0.15 0.60 0.90

 3 0.00010 0.00001 2.0 0.15 0.55 0.90

 4 0.00010 0.00001 2.0 0.18 0.70 0.90

 5 0.00010 0.00001 2.0 0.15 0.62 0.90

 6 0.00010 0.00001 2.0 0.10 0.32 0.90

 7 0.00010 0.00001 2.0 0.15 0.58 0.90

 END SILT-CLAY-PM

 SSED-INIT

RCHRES *** SSED1 SSED2 SSED3

 1 7 1. 25. 25.

 END SSED-INIT

 BED-INIT

RCHRES *** BEDDEP SANDFR SILTFR CLAYFR

 1 7 4. .70 .20 .10

 END BED-INIT

 BENTH-FLAG

*** RCHRES Benthic release flag

*** x - x BENF

 1 7 1

 END BENTH-FLAG

 SCOUR-PARMS

RCHRES *** SCRVEL SCRMUL

 1 7 3. 2

 END SCOUR-PARMS

 OX-FLAGS

*** RCHRES Oxygen flags

*** x - x REAM

 1 7 3

 END OX-FLAGS

 OX-GENPARM

RCHRES *** KBOD20 TCBOD KODSET SUPSAT

 1 7 .020 1.050 .030 1.25

 END OX-GENPARM

 OX-BENPARM

RCHRES *** BENOD TCBEN EXPOD BRBOD1 BRBOD2 EXPREL

 1 7 10. 1.1 1.2 10. 15. 2.5

 END OX-BENPARM

 OX-REAPARM

RCHRES *** TCGINV REAK EXPRED EXPREV

 1 7 1.024 .726 -1.673 .969

 END OX-REAPARM

 OX-INIT

RCHRES *** DOX BOD SATDO

 1 7 11.3 2.92 12.0

 END OX-INIT

  NUTRIENTS ** **

 NUT-FLAGS

 RCHRES TAM NO2 PO4 AMV DEN ADNH ADPO PHFG ***

 # - # ***

 1 7 1 0 1 0 1 1 1 2

 END NUT-FLAGS

 NUT-NITDENIT

 RCHRES KTAM20 KNO220 TCNIT KNO320 TCDEN DENOXT ***

 # - # /hr /hr /hr mg/l ***

 1 7 .05 .050 1.045 .005 1.04 1.
136 Appendix 3

 END NUT-NITDENIT

 NUT-BEDCONC

 RCHRES Bed concentrations of NH4 & PO4 (mg/kg) ***

 # - # NH4-sand NH4-silt NH4-clay PO4-sand PO4-silt PO4-clay ***

 1 7 1. 30. 50. 90. 700. 900.

 END NUT-BEDCONC

 NUT-ADSPARM

 RCHRES Partition coefficients for NH4 AND PO4 (ml/g) ***

 # - # NH4-sand NH4-silt NH4-clay PO4-sand PO4-silt PO4-clay ***

 1 7 10. 500. 800. 600. 15000. 18000.

 END NUT-ADSPARM

 NUT-DINIT

 RCHRES NO3 TAM NO2 PO4 PH ***

 # - # mg/l mg/l mg/l mg/l ***

 1 7 2.0 .055 .033 7.

 END NUT-DINIT

 NUT-ADSINIT

 RCHRES Initial suspended NH4 and PO4 concentrations (mg/kg) ***

 # - # NH4-sand NH4-silt NH4-clay PO4-sand PO4-silt PO4-clay ***

 1 7 0.1 0.3 0.5 0.1 0.5 0.8

 END NUT-ADSINIT

  PLANKTON ** **

 PLNK-FLAGS

 RCHRES PHYF ZOOF BALF SDLT AMRF DECF NSFG ZFOO ***

 # - # ***

 1 7 1 0 1 0 0 1 1 2

 END PLNK-FLAGS

 PLNK-PARM1

 RCHRES RATCLP NONREF LITSED ALNPR EXTB MALGR ***

 # - # /ft /hr ***

 1 7 .60 .5 0. 0.8 .20 .200

 END PLNK-PARM1

 PLNK-PARM2

 RCHRES *** CMMLT CMMN CMMNP CMMP TALGRH TALGRL TALGRM

 # - # ***ly/min mg/l mg/l mg/l deg F deg F deg F

 1 7 .03 .045 .029 .015 95. 32. 55.

 END PLNK-PARM2

 PLNK-PARM3

 RCHRES ALR20 ALDH ALDL OXALD NALDH PALDH ***

 # - # /hr /hr /hr /hr mg/l mg/l ***

 1 7 .055 .010 .001 .03 .015 .001

 END PLNK-PARM3

 PHYTO-PARM

 RCHRES SEED MXSTAY OREF CLALDH PHYSET REFSET ***

 # - # mg/l mg/l ug/l ***

 1 7 .4 .8 20. 50. .012 .010

 END PHYTO-PARM

 PLNK-INIT

 RCHRES PHYTO ZOO BENAL ORN ORP ORC ***

 # - # mg/l org/l mg/m2 mg/l mg/l mg/l ***

 1 7 .700 .03 1.0E-8 1. .2 8.

END PLNK-INIT

END RCHRES

FTABLES

 FTABLE 1

 ROWS COLS *** West Br. to Main Stem

 15 4

 DEPTH AREA VOLUME DISCH FLO-THRU ***

 (FT) (ACRES) (AC-FT) (CFS) (MIN) ***

 0.00 0.0 0.0 0.0 0.

 0.29 17.0 4.9 9.8 365.

 0.58 17.2 9.9 31.0 233.

 0.88 17.4 15.0 60.7 179.

 1.17 17.6 20.1 97.5 150.

 1.46 17.8 25.3 140.8 130.

 1.75 18.0 30.5 190.0 116.

 2.33 18.4 41.1 304.4 98.

 2.92 18.8 51.9 438.3 86.

 3.50 19.2 63.0 590.1 78.

 4.67 41.7 98.5 987.4 72.

 5.83 64.3 160.4 1496. 78.

 7.00 86.9 248.6 2133. 85.

 8.17 109.5 363.1 2913. 91.

 9.33 132.1 504.0 3848. 95.

 END FTABLE 1

 FTABLE 2

 ROWS COLS *** East Br. to Main Stem to West Br.

 15 4
Appendix 3 137

 DEPTH AREA VOLUME DISCH FLO-THRU ***

 (FT) (ACRES) (AC-FT) (CFS) (MIN) ***

 0.00 0.0 0.0 0.0 0.

 0.38 35.0 13.1 14.5 655.

 0.75 35.4 26.3 45.7 418.

 1.13 35.9 39.6 89.3 322.

 1.50 36.3 53.2 143.5 269.

 1.88 36.7 66.8 207.1 234.

 2.25 37.1 80.7 279.3 210.

 3.00 37.9 108.8 447.2 177.

 3.75 38.7 137.5 643.5 155.

 4.50 39.6 166.9 865.9 140.

 6.00 138.5 300.4 1464. 149.

 7.50 237.4 582.3 2288. 185.

 9.00 336.3 1012.6 3399. 216.

 10.50 435.2 1591.2 4850. 238.

 12.00 534.1 2318.2 6687. 252.

 END FTABLE 2

 FTABLE 3

 ROWS COLS *** Main Stem at W.Br. to Cooch’s Gage

 15 4

 DEPTH AREA VOLUME DISCH FLO-THRU ***

 (FT) (ACRES) (AC-FT) (CFS) (MIN) ***

 0.00 0.0 0.0 0.0 0.

 0.46 23.4 10.7 23.7 327.

 0.92 23.6 21.4 74.8 208.

 1.38 23.8 32.3 146.4 160.

 1.83 24.0 43.2 235.5 133.

 2.29 24.2 54.2 340.3 116.

 2.75 24.3 65.3 459.4 103.

 3.67 24.7 87.8 736.7 87.

 4.58 25.1 110.7 1061. 76.

 5.50 25.5 133.9 1429. 68.

 7.33 73.5 224.7 2390. 68.

 9.17 121.5 403.5 3677. 80.

 11.00 169.5 670.3 5368. 91.

 12.83 217.5 1025.1 7530. 99.

 14.67 265.5 1467.9 10222. 104.

 END FTABLE 3

 FTABLE 4

 ROWS COLS *** Little Mill to Newport Gage

 15 4

 DEPTH AREA VOLUME DISCH FLO-THRU ***

 (FT) (ACRES) (AC-FT) (CFS) (MIN) ***

 0.00 0.0 0.0 0.0 0.

 0.42 8.9 3.6 8.1 324.

 0.83 9.4 7.4 25.7 210.

 1.25 9.9 11.4 50.5 165.

 1.67 10.3 15.7 81.7 139.

 2.08 10.8 20.1 118.8 123.

 2.50 11.3 24.7 161.5 111.

 3.33 12.2 34.4 263.5 95.

 4.17 13.2 45.0 387.1 84.

 5.00 14.1 56.4 532.3 77.

 6.67 45.4 105.9 986.4 78.

 8.33 76.7 207.7 1685. 89.

 10.00 108.0 361.7 2715. 97.

 11.67 139.3 567.8 4147. 99.

 13.33 170.7 826.1 6047. 99.

 END FTABLE 4

 FTABLE 5

 ROWS COLS *** Newport Gage to Christina R.

 15 4

 DEPTH AREA VOLUME DISCH FLO-THRU ***

 (FT) (ACRES) (AC-FT) (CFS) (MIN) ***

 0.00 0.0 0.0 0.0 0.

 0.42 5.3 2.1 8.1 191.

 0.83 5.5 4.4 25.7 123.

 1.25 5.7 6.7 50.6 96.

 1.67 5.9 9.1 81.7 81.

 2.08 6.2 11.7 118.6 71.

 2.50 6.4 14.3 161.1 64.

 3.33 6.9 19.8 261.9 55.

 4.17 7.3 25.7 383.4 49.

 5.00 7.8 32.1 525.1 44.

 6.67 38.8 70.9 961.7 54.

 8.33 69.8 161.3 1638. 72.

 10.00 100.7 303.4 2640. 83.

 11.67 131.7 497.1 4040. 89.

 13.33 162.7 742.5 5905. 91.

 END FTABLE 5

 FTABLE 6

 ROWS COLS *** Muddy Run

 15 4

 DEPTH AREA VOLUME DISCH FLO-THRU ***

 (FT) (ACRES) (AC-FT) (CFS) (MIN) ***

 0.00 0.0 0.0 0.0 0.

 0.42 12.8 5.2 5.2 727.
138 Appendix 3

 0.83 13.5 10.7 16.5 471.

 1.25 14.1 16.4 32.3 369.

 1.67 14.7 22.4 52.2 312.

 2.08 15.3 28.7 75.7 275.

 2.50 15.9 35.2 102.7 249.

 3.33 17.1 48.9 166.9 213.

 4.17 18.4 63.7 244.1 190.

 5.00 19.6 79.5 334.3 173.

 6.67 87.6 168.8 611.5 200.

 8.33 155.5 371.4 1025. 263.

 10.00 223.5 687.3 1621. 308.

 11.67 291.5 1116.5 2435. 333.

 13.33 359.5 1658.9 3503. 344.

 END FTABLE 6

 FTABLE 7

 ROWS COLS *** Belltown Run

 15 4

 DEPTH AREA VOLUME DISCH FLO-THRU ***

 (FT) (ACRES) (AC-FT) (CFS) (MIN) ***

 0.00 0.0 0.0 0.0 0.

 0.33 2.7 0.9 3.1 205.

 0.67 2.9 1.8 9.7 134.

 1.00 3.0 2.8 19.1 105.

 1.33 3.2 3.8 31.0 89.

 1.67 3.4 4.9 45.2 79.

 2.00 3.5 6.1 61.5 71.

 2.67 3.9 8.5 100.8 61.

 3.33 4.2 11.2 148.9 55.

 4.00 4.5 14.1 205.7 50.

 5.33 21.3 31.4 385.9 59.

 6.67 38.2 71.0 660.4 78.

 8.00 55.0 133.1 1061. 91.

 9.33 71.8 217.6 1614. 98.

 10.67 88.6 324.5 2344. 101.

 END FTABLE 7

END FTABLES

COPY

 TIMESERIES

 # - # NPT NMN ***

 10 500 20

 END TIMESERIES

END COPY

EXT SOURCES

<-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> ***

<Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # ***

*** Meteorological data

WDM1 75 PREC 0 ENGL 0.94 PERLND 502 511 EXTNL PREC 1 1

WDM1 75 PREC 0 ENGL 0.94 PERLND 802 811 EXTNL PREC 1 1

WDM1 94 PREC 0 ENGL 0.95 PERLND 902 911 EXTNL PREC 1 1

WDM1 75 PREC 0 ENGL 13421.3 COPY 200 0 INPUT MEAN 4 1

WDM1 94 PREC 0 ENGL 3443.6 COPY 300 0 INPUT MEAN 4 1

WDM1 50 ATMP 0 ENGL 1.0 PERLND 502 911 EXTNL GATMP 1 1

WDM1 45 DWPT 0 ENGL 1.0 PERLND 502 911 EXTNL DTMPG 1 1

WDM1 30 WIND 0 ENGL 1.0 PERLND 502 911 EXTNL WINMOV 1 1

WDM1 20 PETX 0 ENGL 1.1 PERLND 502 911 EXTNL PETINP 1 1

WDM1 10 SOLR 0 ENGL 1.0 PERLND 502 911 EXTNL SOLRAD 1 1

WDM1 75 PREC 0 ENGL 0.94 IMPLND 501 502 EXTNL PREC 1 1

WDM1 75 PREC 0 ENGL 0.94 IMPLND 801 802 EXTNL PREC 1 1

WDM1 94 PREC 0 ENGL 0.95 IMPLND 901 902 EXTNL PREC 1 1

WDM1 50 ATMP 0 ENGL 1.0 IMPLND 501 902 EXTNL GATMP 1 1

WDM1 45 DWPT 0 ENGL 1.0 IMPLND 501 902 EXTNL DTMPG 1 1

WDM1 30 WIND 0 ENGL 1.0 IMPLND 501 902 EXTNL WINMOV 1 1

WDM1 20 PETX 0 ENGL 1.1 IMPLND 501 902 EXTNL PETINP 1 1

WDM1 10 SOLR 0 ENGL 1.0 IMPLND 501 902 EXTNL SOLRAD 1 1

WDM1 75 PREC 0 ENGL 0.94 RCHRES 1 3 EXTNL PREC 1 1

WDM1 94 PREC 0 ENGL 0.95 RCHRES 4 5 EXTNL PREC 1 1

WDM1 75 PREC 0 ENGL 0.94 RCHRES 6 7 EXTNL PREC 1 1

WDM1 50 ATMP 0 ENGL 1.0 RCHRES 1 7 EXTNL GATMP 1 1

WDM1 45 DWPT 0 ENGL 1.0 RCHRES 1 7 EXTNL DEWTMP 1 1

WDM1 40 COVR 0 ENGL 1.0 RCHRES 1 7 EXTNL CLOUD 1 1

WDM1 30 WIND 0 ENGL 1.0 RCHRES 1 7 EXTNL WIND 1 1

WDM1 20 PETX 0 ENGL 1.1 RCHRES 1 7 EXTNL POTEV 1 1

WDM1 10 SOLR 0 ENGL 1.0 RCHRES 1 7 EXTNL SOLRAD 1 1

*** Point source Discharges ***

*** Meadowview

WDM1 300 PTSQ 0 ENGL 1.0 RCHRES 1 EXTNL IVOL 1 1

WDM1 301 TSSX 0 ENGL 1.0 RCHRES 1 INFLOW ISED 3 1

WDM1 302 BODX 0 ENGL 1.0 RCHRES 1 INFLOW OXIF 2 1

WDM1 303 NH3X 0 ENGL 1.0 RCHRES 1 INFLOW NUIF1 2 1

WDM1 304 NO3X 0 ENGL 1.0 RCHRES 1 INFLOW NUIF1 1 1

WDM1 305 NO2X 0 ENGL 1.0 RCHRES 1 INFLOW NUIF1 3 1

WDM1 306 PO4X 0 ENGL 1.0 RCHRES 1 INFLOW NUIF1 4 1

WDM1 308 HEAT 0 ENGL 1.0 RCHRES 1 INFLOW IHEAT 1 1

*** Highlands

WDM1 310 PTSQ 0 ENGL 1.0 RCHRES 1 EXTNL IVOL 1 1

WDM1 311 TSSX 0 ENGL 1.0 RCHRES 1 INFLOW ISED 3 1

WDM1 312 BODX 0 ENGL 1.0 RCHRES 1 INFLOW OXIF 2 1

WDM1 313 NH3X 0 ENGL 1.0 RCHRES 1 INFLOW NUIF1 2 1
Appendix 3 139

WDM1 314 NO3X 0 ENGL 1.0 RCHRES 1 INFLOW NUIF1 1 1

WDM1 315 NO2X 0 ENGL 1.0 RCHRES 1 INFLOW NUIF1 3 1

WDM1 316 PO4X 0 ENGL 1.0 RCHRES 1 INFLOW NUIF1 4 1

WDM1 318 HEAT 0 ENGL 1.0 RCHRES 1 INFLOW IHEAT 1 1

*** GM

WDM1 320 PTSQ 0 ENGL 1.0 RCHRES 5 EXTNL IVOL 1 1

WDM1 321 TSSX 0 ENGL 1.0 RCHRES 5 INFLOW ISED 3 1

WDM1 322 BODX 0 ENGL 1.0 RCHRES 5 INFLOW OXIF 2 1

WDM1 323 NH3X 0 ENGL 0.1 RCHRES 5 INFLOW NUIF1 2 1

WDM1 324 NO3X 0 ENGL 0.15 RCHRES 5 INFLOW NUIF1 1 1

WDM1 325 NO2X 0 ENGL 0.1 RCHRES 5 INFLOW NUIF1 3 1

WDM1 326 PO4X 0 ENGL 0.05 RCHRES 5 INFLOW NUIF1 4 1

WDM1 328 HEAT 0 ENGL 1.0 RCHRES 5 INFLOW IHEAT 1 1

*** DuPont

WDM1 330 PTSQ 0 ENGL 1.0 RCHRES 4 EXTNL IVOL 1 1

WDM1 331 TSSX 0 ENGL 1.0 RCHRES 4 INFLOW ISED 3 1

WDM1 332 BODX 0 ENGL 1.0 RCHRES 4 INFLOW OXIF 2 1

WDM1 333 NH3X 0 ENGL 1.0 RCHRES 4 INFLOW NUIF1 2 1

WDM1 334 NO3X 0 ENGL 1.0 RCHRES 4 INFLOW NUIF1 1 1

WDM1 335 NO2X 0 ENGL 1.0 RCHRES 4 INFLOW NUIF1 3 1

WDM1 336 PO4X 0 ENGL 1.0 RCHRES 4 INFLOW NUIF1 4 1

WDM1 338 HEAT 0 ENGL 1.0 RCHRES 4 INFLOW IHEAT 1 1

*** DuPont

WDM1 340 PTSQ 0 ENGL 1.0 RCHRES 4 EXTNL IVOL 1 1

WDM1 341 TSSX 0 ENGL 1.0 RCHRES 4 INFLOW ISED 3 1

WDM1 342 BODX 0 ENGL 1.0 RCHRES 4 INFLOW OXIF 2 1

WDM1 343 NH3X 0 ENGL 1.0 RCHRES 4 INFLOW NUIF1 2 1

WDM1 344 NO3X 0 ENGL 1.0 RCHRES 4 INFLOW NUIF1 1 1

WDM1 345 NO2X 0 ENGL 1.0 RCHRES 4 INFLOW NUIF1 3 1

WDM1 346 PO4X 0 ENGL 1.0 RCHRES 4 INFLOW NUIF1 4 1

WDM1 348 HEAT 0 ENGL 1.0 RCHRES 4 INFLOW IHEAT 1 1

*** Withdrawals *** NONE

END EXT SOURCES

EXT TARGETS

<-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Aggr Amd ***

<Name> x <Name> x x<-factor->strg <Name> x <Name>qf tem strg strg***

*** mult factor for rovol is 12/area

*** mult factor for others 1/area

***

***(Gage: Christina River at Coochs Bridge)

RCHRES 3 ROFLOW ROVOL .000894099 WDM 1100 FLOW ENGL REPL

RCHRES 3 HYDR RO WDM 1109 FLOW ENGL REPL

COPY 200 OUTPUT MEAN 1 .000074508 WDM 1101 SURO ENGL REPL

COPY 200 OUTPUT MEAN 2 .000074508 WDM 1102 IFWO ENGL REPL

COPY 200 OUTPUT MEAN 3 .000074508 WDM 1103 AGWO ENGL REPL

COPY 200 OUTPUT MEAN 4 .000074508 WDM 1104 PREC ENGL REPL

COPY 200 OUTPUT MEAN 5 .000074508 WDM 1105 PETX ENGL REPL

COPY 200 OUTPUT MEAN 6 .000074508 WDM 1106 TAET ENGL REPL

COPY 200 OUTPUT MEAN 7 .000074508 WDM 1107 UZSX ENGL REPL

COPY 200 OUTPUT MEAN 8 .000074508 WDM 1108 LZSX ENGL REPL

COPY 200 OUTPUT MEAN 9 .000074508 WDM 1200 UZI ENGL REPL

*** sediment, nutrient output from pervious areas, ground water, impervious areas

COPY 200 OUTPUT MEAN 10 WDM 2100 SOSED ENGL REPL

COPY 200 OUTPUT MEAN 11 WDM 2122 PONO3 ENGL REPL

COPY 200 OUTPUT MEAN 18 WDM 2123 SSNO3 ENGL REPL

COPY 200 OUTPUT MEAN 12 WDM 2124 PONH4 ENGL REPL

COPY 200 OUTPUT MEAN 19 WDM 2125 SSNH4 ENGL REPL

COPY 200 OUTPUT MEAN 13 WDM 2126 POPHOS ENGL REPL

COPY 200 OUTPUT MEAN 20 WDM 2127 SSPHOS ENGL REPL

COPY 200 OUTPUT MEAN 14 WDM 2130 SOSLD ENGL REPL

COPY 200 OUTPUT MEAN 15 WDM 2135 IONO3 ENGL REPL

COPY 200 OUTPUT MEAN 16 WDM 2136 IONH4 ENGL REPL

COPY 200 OUTPUT MEAN 17 WDM 2137 IOPHOS ENGL REPL

***(Gage: Little Mill Creek near Newport)

RCHRES 4 ROFLOW ROVOL .003484714 WDM 1110 FLOW ENGL REPL

RCHRES 4 HYDR RO WDM 1119 FLOW ENGL REPL

COPY 300 OUTPUT MEAN 1 .000290393 WDM 1111 SURO ENGL REPL

COPY 300 OUTPUT MEAN 2 .000290393 WDM 1112 IFWO ENGL REPL

COPY 300 OUTPUT MEAN 3 .000290393 WDM 1113 AGWO ENGL REPL

COPY 300 OUTPUT MEAN 4 .000290393 WDM 1114 PREC ENGL REPL

COPY 300 OUTPUT MEAN 5 .000290393 WDM 1115 PETX ENGL REPL

COPY 300 OUTPUT MEAN 6 .000290393 WDM 1116 TAET ENGL REPL

COPY 300 OUTPUT MEAN 7 .000290393 WDM 1117 UZSX ENGL REPL

COPY 300 OUTPUT MEAN 8 .000290393 WDM 1118 LZSX ENGL REPL

*** Water temperature

RCHRES 3 HTRCH TW WDM 1500 WTEM METR REPL

RCHRES 4 HTRCH TW WDM 1510 WTEM METR REPL

RCHRES 3 SEDTRN SSED 4 WDM 1550 SEDC METR REPL

RCHRES 4 SEDTRN SSED 4 WDM 1580 SEDC METR REPL

*** Oxygen, BOD, nutrients

RCHRES 3 OXRX DOX WDM 1551 DOXX METR REPL

RCHRES 3 OXRX BOD WDM 1552 BODX METR REPL

RCHRES 3 NUTRX DNUST 1 WDM 1553 NO3X METR REPL

RCHRES 3 NUTRX DNUST 2 WDM 1554 NH4X METR REPL

RCHRES 3 NUTRX DNUST 4 WDM 1555 PO4X METR REPL

COPY 11 OUTPUT MEAN 1 WDM 1556 NH4P METR REPL

COPY 11 OUTPUT MEAN 2 WDM 1557 PO4P METR REPL

RCHRES 3 PLANK PKST3 4 WDM 1558 TORN METR REPL
140 Appendix 3

RCHRES 3 PLANK PHYCLA 1 WDM 1559 PHCA METR REPL

RCHRES 4 OXRX DOX WDM 1581 DOXX METR REPL

RCHRES 4 OXRX BOD WDM 1582 BODX METR REPL

RCHRES 4 NUTRX DNUST 1 WDM 1583 NO3X METR REPL

RCHRES 4 NUTRX DNUST 2 WDM 1584 NH4X METR REPL

RCHRES 4 NUTRX DNUST 4 WDM 1585 PO4X METR REPL

COPY 12 OUTPUT MEAN 1 WDM 1586 NH4P METR REPL

COPY 12 OUTPUT MEAN 2 WDM 1587 PO4P METR REPL

RCHRES 4 PLANK PKST3 4 WDM 1588 TORN METR REPL

RCHRES 4 PLANK PHYCLA 1 WDM 1589 PHCA METR REPL

RCHRES 2 OXRX DOX WDM 1651 DOXX METR REPL

RCHRES 2 OXRX BOD WDM 1652 BODX METR REPL

RCHRES 2 NUTRX DNUST 1 WDM 1653 NO3X METR REPL

RCHRES 2 NUTRX DNUST 2 WDM 1654 NH4X METR REPL

RCHRES 2 NUTRX DNUST 4 WDM 1655 PO4X METR REPL

RCHRES 1 NUTRX DNUST 1 WDM 1753 NO3X METR REPL

RCHRES 1 NUTRX DNUST 2 WDM 1754 NH4X METR REPL

RCHRES 1 NUTRX DNUST 4 WDM 1755 PO4X METR REPL

***Sediment calibration

RCHRES 1 HYDR TAU WDM 9001 TAU ENGL REPL

RCHRES 2 HYDR TAU WDM 9002 TAU ENGL REPL

RCHRES 3 HYDR TAU WDM 9003 TAU ENGL REPL

RCHRES 4 HYDR TAU WDM 9004 TAU ENGL REPL

RCHRES 5 HYDR TAU WDM 9005 TAU ENGL REPL

RCHRES 6 HYDR TAU WDM 9006 TAU ENGL REPL

RCHRES 7 HYDR TAU WDM 9007 TAU ENGL REPL

***

PERLND 502 SEDMNT DETS *** WDM 9020 DETS ENGL REPL

PERLND 503 SEDMNT DETS *** WDM 9021 DETS ENGL REPL

PERLND 504 SEDMNT DETS WDM 9022 DETS ENGL REPL

PERLND 506 SEDMNT DETS WDM 9023 DETS ENGL REPL

PERLND 508 SEDMNT DETS WDM 9024 DETS ENGL REPL

PERLND 509 SEDMNT DETS WDM 9025 DETS ENGL REPL

PERLND 803 SEDMNT DETS WDM 9032 DETS ENGL REPL

PERLND 804 SEDMNT DETS WDM 9033 DETS ENGL REPL

PERLND 806 SEDMNT DETS WDM 9034 DETS ENGL REPL

PERLND 809 SEDMNT DETS WDM 9035 DETS ENGL REPL

PERLND 903 SEDMNT DETS WDM 9042 DETS ENGL REPL

PERLND 904 SEDMNT DETS WDM 9043 DETS ENGL REPL

PERLND 908 SEDMNT DETS WDM 9044 DETS ENGL REPL

PERLND 909 SEDMNT DETS WDM 9045 DETS ENGL REPL

END EXT TARGETS

SCHEMATIC

<-Source-> <--Area--> <-Target-> <ML> ***

<Name> # <-factor-> <Name> # # ***

*** Note: All PLS-RCH and ILS-RCH multiplication factors are acres.

*** Conversion factors, where applicable, are in Mass-Link.

***

*** Segment 5 (Upper West, East Branch Christina)

*** Tributary to Reach 1 (Upper West Br. Christina)

PERLND 502 109.248 RCHRES 1 1

PERLND 503 0.000 RCHRES 1 1

PERLND 504 4.868 RCHRES 1 1

PERLND 505 0.000 RCHRES 1 1

PERLND 506 696.412 RCHRES 1 1

PERLND 507 0.000 RCHRES 1 1

PERLND 508 355.717 RCHRES 1 1

PERLND 509 12.677 RCHRES 1 1

PERLND 510 0.000 RCHRES 1 1

PERLND 511 1.861 RCHRES 1 1

IMPLND 501 12.139 RCHRES 1 2

IMPLND 502 4.868 RCHRES 1 2

*** Tributary to Reach 2 (Upper East Br. Christina)

PERLND 502 1155.693 RCHRES 2 1

PERLND 503 212.156 RCHRES 2 1

PERLND 504 11.885 RCHRES 2 1

PERLND 505 0.000 RCHRES 2 1

PERLND 506 1861.976 RCHRES 2 1

PERLND 507 0.000 RCHRES 2 1

PERLND 508 981.170 RCHRES 2 1

PERLND 509 27.181 RCHRES 2 1

PERLND 510 3.114 RCHRES 2 1

PERLND 511 46.181 RCHRES 2 1

IMPLND 501 219.334 RCHRES 2 2

IMPLND 502 11.885 RCHRES 2 2

*** Segment 8 (Coastal Plain, Mainstem Christina)

*** Tributary to Reach 1 (Upper West Br. Christina)

PERLND 802 245.640 RCHRES 1 1

PERLND 803 122.892 RCHRES 1 1

PERLND 804 245.094 RCHRES 1 1

PERLND 805 0.000 RCHRES 1 1

PERLND 806 838.366 RCHRES 1 1

PERLND 807 0.000 RCHRES 1 1

PERLND 808 723.214 RCHRES 1 1

PERLND 809 385.022 RCHRES 1 1

PERLND 810 0.000 RCHRES 1 1

PERLND 811 192.676 RCHRES 1 1

IMPLND 801 79.962 RCHRES 1 2
Appendix 3 141

IMPLND 802 258.123 RCHRES 1 2

*** Tributary to Reach 2 (Upper East Br. Christina)

PERLND 802 130.977 RCHRES 2 1

PERLND 803 438.686 RCHRES 2 1

PERLND 804 163.001 RCHRES 2 1

PERLND 805 0.000 RCHRES 2 1

PERLND 806 77.130 RCHRES 2 1

PERLND 807 0.000 RCHRES 2 1

PERLND 808 181.729 RCHRES 2 1

PERLND 809 233.640 RCHRES 2 1

PERLND 810 0.000 RCHRES 2 1

PERLND 811 95.433 RCHRES 2 1

IMPLND 801 202.561 RCHRES 2 2

IMPLND 802 173.604 RCHRES 2 2

*** Tributary to Reach 3 (confluence to Cooches)

PERLND 802 137.008 RCHRES 3 1

PERLND 803 501.478 RCHRES 3 1

PERLND 804 365.605 RCHRES 3 1

PERLND 805 0.000 RCHRES 3 1

PERLND 806 263.490 RCHRES 3 1

PERLND 807 0.000 RCHRES 3 1

PERLND 808 524.686 RCHRES 3 1

PERLND 809 227.950 RCHRES 3 1

PERLND 810 6.005 RCHRES 3 1

PERLND 811 257.298 RCHRES 3 1

IMPLND 801 230.142 RCHRES 3 2

IMPLND 802 389.565 RCHRES 3 2

*** Muddy Run (reach 6)

PERLND 802 333.809 RCHRES 6 1

PERLND 803 486.836 RCHRES 6 1

PERLND 804 365.771 RCHRES 6 1

PERLND 805 0.000 RCHRES 6 1

PERLND 806 852.926 RCHRES 6 1

PERLND 807 0.000 RCHRES 6 1

PERLND 808 2125.246 RCHRES 6 1

PERLND 809 588.951 RCHRES 6 1

PERLND 810 62.495 RCHRES 6 1

PERLND 811 96.513 RCHRES 6 1

IMPLND 801 245.734 RCHRES 6 2

IMPLND 802 374.186 RCHRES 6 2

*** Belltown Run (reach 7)

PERLND 802 23.152 RCHRES 7 1

PERLND 803 820.722 RCHRES 7 1

PERLND 804 281.534 RCHRES 7 1

PERLND 805 0.000 RCHRES 7 1

PERLND 806 344.677 RCHRES 7 1

PERLND 807 0.000 RCHRES 7 1

PERLND 808 1398.689 RCHRES 7 1

PERLND 809 328.540 RCHRES 7 1

PERLND 810 34.250 RCHRES 7 1

PERLND 811 189.419 RCHRES 7 1

IMPLND 801 354.311 RCHRES 7 2

IMPLND 802 302.295 RCHRES 7 2

 Reach Connections ***

RCHRES 1 RCHRES 3 3

RCHRES 2 RCHRES 3 3

***

*** Segment 9 (Little Mill Creek)

*** Tributary to Reach 4 (Little Mill Ck to gage)

PERLND 902 50.688 RCHRES 4 1

PERLND 903 965.315 RCHRES 4 1

PERLND 904 448.435 RCHRES 4 1

PERLND 905 0.000 RCHRES 4 1

PERLND 906 48.634 RCHRES 4 1

PERLND 907 0.000 RCHRES 4 1

PERLND 908 627.608 RCHRES 4 1

PERLND 909 316.954 RCHRES 4 1

PERLND 910 8.451 RCHRES 4 1

PERLND 911 89.883 RCHRES 4 1

IMPLND 901 419.338 RCHRES 4 2

IMPLND 902 468.305 RCHRES 4 2

*** Lower Little Mill - below gage to confl. (reach 5)

PERLND 902 2.571 RCHRES 5 1

PERLND 903 512.817 RCHRES 5 1

PERLND 904 431.453 RCHRES 5 1

PERLND 905 0.000 RCHRES 5 1

PERLND 906 0.000 RCHRES 5 1

PERLND 907 0.000 RCHRES 5 1

PERLND 908 214.157 RCHRES 5 1

PERLND 909 372.013 RCHRES 5 1

PERLND 910 27.032 RCHRES 5 1

PERLND 911 227.841 RCHRES 5 1

IMPLND 901 220.064 RCHRES 5 2

IMPLND 902 451.340 RCHRES 5 2
142 Appendix 3

 Reach Connections ***

RCHRES 4 RCHRES 5 3

*** Copy Block outputs for tidal subbasins

***

*** Segment 8 (Coastal Plain)

*** Christina (Cooches to Smalleys Pond - reach 8)

PERLND 802 29.162 COPY 400 91

PERLND 803 1687.533 COPY 400 91

PERLND 804 799.365 COPY 400 91

PERLND 805 0.000 COPY 400 91

PERLND 806 357.438 COPY 400 91

PERLND 807 0.000 COPY 400 91

PERLND 808 1843.667 COPY 400 91

PERLND 809 476.203 COPY 400 91

PERLND 810 36.714 COPY 400 91

PERLND 811 698.509 COPY 400 91

IMPLND 801 565.751 COPY 400 92

IMPLND 802 642.866 COPY 400 92

*** Christina (Smalleys to Delaware confluence - reach 9)

PERLND 802 69.386 COPY 500 91

PERLND 803 1443.678 COPY 500 91

PERLND 804 2489.162 COPY 500 91

PERLND 805 0.000 COPY 500 91

PERLND 806 251.481 COPY 500 91

PERLND 807 0.000 COPY 500 91

PERLND 808 1746.197 COPY 500 91

PERLND 809 2801.890 COPY 500 91

PERLND 810 600.317 COPY 500 91

PERLND 811 1386.300 COPY 500 91

IMPLND 801 626.429 COPY 500 92

IMPLND 802 2588.088 COPY 500 92

*** HSPEXP ***

*** Christina at Cooches -output from Reach 3

PERLND 502 1264.941 COPY 200 91

PERLND 503 212.156 COPY 200 91

PERLND 504 16.753 COPY 200 91

PERLND 505 0.000 COPY 200 91

PERLND 506 2558.388 COPY 200 91

PERLND 507 0.000 COPY 200 91

PERLND 508 1338.887 COPY 200 91

PERLND 509 39.858 COPY 200 91

PERLND 510 3.114 COPY 200 91

PERLND 511 48.042 COPY 200 91

IMPLND 501 231.473 COPY 200 92

IMPLND 502 16.753 COPY 200 92

PERLND 802 513.625 COPY 200 91

PERLND 803 1063.056 COPY 200 91

PERLND 804 773.700 COPY 200 91

PERLND 805 0.000 COPY 200 91

PERLND 806 1178.986 COPY 200 91

PERLND 807 0 COPY 200 91

PERLND 808 1429.626 COPY 200 91

PERLND 809 846.612 COPY 200 91

PERLND 810 6.005 COPY 200 91

PERLND 811 545.407 COPY 200 91

IMPLND 801 512.665 COPY 200 92

IMPLND 802 821.292 COPY 200 92

*** Little Mill Ck to gage - output from reach 4

PERLND 902 50.688 COPY 300 91

PERLND 903 965.315 COPY 300 91

PERLND 904 448.435 COPY 300 91

PERLND 905 0.000 COPY 300 91

PERLND 906 48.634 COPY 300 91

PERLND 907 0.000 COPY 300 91

PERLND 908 627.608 COPY 300 91

PERLND 909 316.954 COPY 300 91

PERLND 910 8.451 COPY 300 91

PERLND 911 89.883 COPY 300 91

IMPLND 901 419.338 COPY 300 92

IMPLND 902 468.305 COPY 300 92

END SCHEMATIC

MASS-LINK

 MASS-LINK 1

<Srce> <-Grp> <-Member-><--Mult--> <Targ> <-Grp> <-Member-> ***

<Name> <Name> <Name> # #<-factor-> <Name> <Name> <Name> # # ***

PERLND PWATER PERO 0.0833333 RCHRES INFLOW IVOL

PERLND SEDMNT SOSED 0.10 RCHRES INFLOW ISED 1

PERLND SEDMNT SOSED 0.40 RCHRES INFLOW ISED 2

PERLND SEDMNT SOSED 0.50 RCHRES INFLOW ISED 3

PERLND PWTGAS POHT RCHRES INFLOW IHEAT

PERLND PWTGAS PODOXM RCHRES INFLOW OXIF 1

PERLND PQUAL POQUAL 1 RCHRES INFLOW NUIF1 1

PERLND PQUAL POQUAL 2 RCHRES INFLOW NUIF1 2

PERLND PQUAL POQUAL 3 RCHRES INFLOW NUIF1 4

PERLND PQUAL POQUAL 4 RCHRES INFLOW OXIF 2

PERLND PQUAL POQUAL 5 RCHRES INFLOW PKIF 3

 END MASS-LINK 1
Appendix 3 143

 MASS-LINK 2

<Srce> <-Grp> <-Member-><--Mult--> <Targ> <-Grp> <-Member-> ***

<Name> <Name> <Name> # #<-factor-> <Name> <Name> <Name> # # ***

IMPLND IWATER SURO 0.0833333 RCHRES INFLOW IVOL

IMPLND SOLIDS SOSLD 0.10 RCHRES INFLOW ISED 1

IMPLND SOLIDS SOSLD 0.40 RCHRES INFLOW ISED 2

IMPLND SOLIDS SOSLD 0.50 RCHRES INFLOW ISED 3

IMPLND IWTGAS SOHT RCHRES INFLOW IHEAT

IMPLND IWTGAS SODOXM RCHRES INFLOW OXIF 1

IMPLND IQUAL SOQUAL 1 RCHRES INFLOW NUIF1 1

IMPLND IQUAL SOQUAL 2 RCHRES INFLOW NUIF1 2

IMPLND IQUAL SOQUAL 3 RCHRES INFLOW NUIF1 4

IMPLND IQUAL SOQUAL 4 RCHRES INFLOW OXIF 2

 END MASS-LINK 2

 MASS-LINK 3

<Srce> <-Grp> <-Member-><--Mult--> <Targ> <-Grp> <-Member-> ***

<Name> <Name> <Name> # #<-factor-> <Name> <Name> <Name> # # ***

RCHRES ROFLOW RCHRES INFLOW

 END MASS-LINK 3

 MASS-LINK 91

<-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> ***

<Name> <Name> x x<-factor->strg <Name> <Name> x x ***

PERLND PWATER SURO COPY INPUT MEAN 1

PERLND PWATER IFWO COPY INPUT MEAN 2

PERLND PWATER AGWO COPY INPUT MEAN 3

PERLND PWATER PET COPY INPUT MEAN 5

PERLND PWATER TAET COPY INPUT MEAN 6

PERLND PWATER UZS COPY INPUT MEAN 7

PERLND PWATER LZS COPY INPUT MEAN 8

PERLND PWATER UZI COPY INPUT MEAN 9

PERLND SEDMNT SOSED COPY INPUT MEAN 10

PERLND PQUAL POQUAL 1 COPY INPUT MEAN 11

PERLND PQUAL POQUAL 2 COPY INPUT MEAN 12

PERLND PQUAL POQUAL 3 COPY INPUT MEAN 13

PERLND PQUAL AOQUAL 1 COPY INPUT MEAN 18

PERLND PQUAL AOQUAL 2 COPY INPUT MEAN 19

PERLND PQUAL AOQUAL 3 COPY INPUT MEAN 20

 END MASS-LINK 91

 MASS-LINK 92

<-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> ***

<Name> <Name> x x<-factor->strg <Name> <Name> x x ***

IMPLND IWATER SURO COPY INPUT MEAN 1

IMPLND IWATER PET COPY INPUT MEAN 5

IMPLND IWATER IMPEV COPY INPUT MEAN 6

IMPLND SOLIDS SOSLD COPY INPUT MEAN 14

IMPLND IQUAL SOQUAL 1 COPY INPUT MEAN 15

IMPLND IQUAL SOQUAL 2 COPY INPUT MEAN 16

IMPLND IQUAL SOQUAL 3 COPY INPUT MEAN 17

 END MASS-LINK 92

 MASS-LINK 93

<-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> ***

<Name> <Name> x x<-factor->strg <Name> <Name> x x ***

COPY OUTPUT MEAN 1 COPY INPUT MEAN 1

COPY OUTPUT MEAN 2 COPY INPUT MEAN 2

COPY OUTPUT MEAN 3 COPY INPUT MEAN 3

COPY OUTPUT MEAN 4 COPY INPUT MEAN 4

COPY OUTPUT MEAN 5 COPY INPUT MEAN 5

COPY OUTPUT MEAN 6 COPY INPUT MEAN 6

COPY OUTPUT MEAN 7 COPY INPUT MEAN 7

COPY OUTPUT MEAN 8 COPY INPUT MEAN 8

COPY OUTPUT MEAN 9 COPY INPUT MEAN 9

COPY OUTPUT MEAN 10 COPY INPUT MEAN 10

COPY OUTPUT MEAN 11 COPY INPUT MEAN 11

COPY OUTPUT MEAN 12 COPY INPUT MEAN 12

COPY OUTPUT MEAN 13 COPY INPUT MEAN 13

COPY OUTPUT MEAN 14 COPY INPUT MEAN 14

COPY OUTPUT MEAN 15 COPY INPUT MEAN 15

COPY OUTPUT MEAN 16 COPY INPUT MEAN 16

COPY OUTPUT MEAN 17 COPY INPUT MEAN 17

 END MASS-LINK 93

END MASS-LINK

NETWORK

<-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> ***

<Name> # <Name> # #<-factor->strg <Name> # # <Name> # # ***

*** Results for calibration

 PARTICULATE N (ADSORBED NH3 + ORG N) ***

RCHRES 3 NUTRX RSNH4 4 GENER 1 INPUT ONE

RCHRES 3 HYDR VOL GENER 1 INPUT TWO

GENER 1 OUTPUT TIMSER 0.368 COPY 11 INPUT MEAN 1

RCHRES 4 NUTRX RSNH4 4 GENER 3 INPUT ONE

RCHRES 4 HYDR VOL GENER 3 INPUT TWO

GENER 3 OUTPUT TIMSER 0.368 COPY 12 INPUT MEAN 1

 PARTICULATE P (ADSORBED PO4 + ORG P) ***

RCHRES 3 NUTRX RSPO4 4 GENER 2 INPUT ONE
144 Appendix 3

RCHRES 3 HYDR VOL GENER 2 INPUT TWO

GENER 2 OUTPUT TIMSER 0.368 COPY 11 INPUT MEAN 2

RCHRES 4 NUTRX RSPO4 4 GENER 4 INPUT ONE

RCHRES 4 HYDR VOL GENER 4 INPUT TWO

GENER 4 OUTPUT TIMSER 0.368 COPY 12 INPUT MEAN 2

END NETWORK

GENER

 OPCODE

 #thru# code ***

 1 4 19

 END OPCODE

END GENER

END RUN