Hydrology and the Effects of

Selected Agricultural Best-Management Practices

in the Bald Eagle Creek Watershed,

York County, Pennsylvania,

Prior To and During Nutrient Management

By Michael J. Langland and David K. Fishel

Water-Quality Study for the 

Chesapeake Bay Program

U.S. GEOLOGICAL SURVEY 

Water-Resources Investigations Report 93-4069

Prepared in cooperation with the

SUSQUEHANNA RIVER BASIN COMMISSION and the 

PENNSYLVANIA DEPARTMENT OF ENVIRONMENTAL 

RESOURCES, BUREAU OF SOIL AND WATER CONSERVATION

Lemoyne, Pennsylvania 

1995
U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY

Gordon P. Eaton, Director

For additional Information 

write to:

District Chief

U.S. Geological Survey, WRD

840 Market Street

Lemoyne, Pennsylvania 17043-1586

Copies of this report can be 

purchased from:

U.S. Geological Survey 

Earth Science Information Center 

Open-File Reports Section 

Box 25286, MS 517 

Denver Federal Center 

Denver, Colorado 80225
CONTENTS

Page

Abstract.......................................................................................... I

Introduction ...................................................................................... 3

Purpose and scope.............................................................................. 4

Approach..................................................................................... 4

Related studies ................................................................................ 4

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

Description of study area ............................................................................ 6

Climate ...................................................................................... 7

Geologic setting ............................................................................... 7

Geologic structure.............................................................................. 7

Basin morphology and topography................................................................. 7

Soils......................................................................................... 9

Land use, crops, and nutrient applications.............................................................. 10

Network design, instrumentation, sampling, and analytical techniques........................................ 16

Precipitation ................................................................................. 16

Streamflow .................................................................................. 16

Water quality................................................................................. 16

Soil nutrients................................................................................. 17

Methods ofdata analysis ........................................................................... 18

Descriptive statistics........................................................................... 18

Correlation analyses ........................................................................... 18

Seasonal Wilcoxon-Mann-Whitney-rank-sum test.................................................... 18

Seasonal Kendall test .......................................................................... 18

Effects of selected agricultural best-management practices on hydrology and soils.............................. 19

Hydrology................................................................................... 19

Precipitation............................................................................ 19

Quantity ........................................................................... 19

Quality ............................................................................ 22

Streamflow............................................................................. 23

Quantity ........................................................................... 23

Base flow...................................................................... 23

Stormflow ..................................................................... 23

Quality............................................................................ 27

Base flow...................................................................... 27

Stormflow ..................................................................... 46

Ground water........................................................................... 53

Availability and occurrence............................................................ 53

Recharge........................................................................... 53

Quality............................................................................ 55

Soils and soil nutrients ......................................................................... 55

iii Water-Resources Investigations Report 93*4069
CONTENTS-Continued

Page 

Effects of changes in nutrient applications, land use, and random events on surface-water quality .................. 59

Changes in nutrient applications.................................................................. 59

Changes in land use ........................................................................... 64

Changes in random events ...................................................................... 68

Suggestions for further study ........................................................................ 68

Summary........................................................................................ 69

References ciled.................................................................................. 71

ILLUSTRATIONS

Figures 1-3. Maps showing:

I .--Locations of Bald Eagle Creek Site I, Brush Run Site 2, and the Little Conestoga

Creek (Nutrient-Management Subbasin) Site 3 in the Lower Susquehanna River Basin. .. 6

2. Locations of farms, streamflow and precipitation gages and sampling sites, and

soil-sampling sites in Bald Eagle Creek Basin.................................... 6

3.-Basin topography and basin configuration at Bald Eagle Creek (top) and Brush Run

(bottom) sites............................................................. 8

4.~Distribution of soil types in Bald Eagle Creek site........................................... 9

5.~Land-use maps showing different cropping patterns at Bald Eagle Creek for (a) the premanagement

period, 1986 and 1987 water years and (b) the nutrient-management period, 1988, 1989,

and 1990 water years......................................................... 12

6-27 .--Graphs showing:

6. Nitrogen and phosphorus applications prior to and during nutrient management at

Bald Eagle Creek......................................................... 14

7. Measured monthly precipitation at Bald Eagle Creek and normal monthly

precipitation at New Park for the 1986-90 water years............................ 21

8.~Monthly deviations of measured precipitation at Bald Eagle Creek from normal

precipitation at New Park during the growing and nongrowing season for the

1986-90 water years....................................................... 21

9.~Relation between daily surface runoff and base-flow components obtained from 

hydrograph separation, and daily precipitation prior to and during nutrient 

management............................................................. 24

10.-Relation between monthly nitrogen discharges in base flow (top) and monthly

nitrogen applications (bottom)................................................ 36

11.-Relation between monthly phosphorus discharges in base flow (top) and monthly

phosphorus applications (bottom). ............................................ 37

12. Total nitrogen and dissolved nitrite plus nitrate concentrations in base flow prior to

and during nutrient management.............................................. 41

13. Distribution of concentrations of total nitrogen and dissolved nitrite plus nitrate in base

flow prior to and during nutrient management in the Bald Eagle Creek subbasin........ 42

14.~Relation between discharges of total nitrogen and dissolved nitrite plus nitrate and

base flow in Bald Eagle Creek ............................................... 42

15.-Relation between concentrations of organic nitrogen and base flow of Bald Eagle Creek ..... 43 

Water-Resources Investigations Report 93-4069 iv
ILLUSTRATIONS-Continued

Page

Figure 6-27.--Graphs showing Continued:

16.--ReIation between concentrations of total and dissolved ammonia nitrogen and

base flow in Bald Eagle Creek ............................................... 43

17.~Distribution of total and dissolved organic nitrogen and ammonia concentrations

in base flow prior to and during nutrient management in Bald Eagle Creek ............ 44

18.-Relation between concentrations of total phosphorus, dissolved phosphorus, and

orthophosphorus and base flow............................................... 44

19.--Relation between discharges of total phosphorus, dissolved phosphorus, and orthophosphorus

and base flow............................................................. 45

20.-Relation between concentrations of suspended sediment and base flow ................... 45

21 .--Relation between monthly precipitation, daily ground-water levels, mean daily

ground-water levels, and daily base flow ....................................... 54

22.-Soluble nitrate-nitrogen yields in selected soil increments on four fields in the

Bald Eagle Creek Basin .................................................... 57

23. Soluble phosphorus yields in selected soil increments on four fields in the

Bald Eagle Creek Basin .................................................... 58

24.~Probability of achieving statistically significant changes in base flow water quality 

at selected reductions or increases in total nitrogen and dissolved nitrite plus 

nitrate concentrations ...................................................... 62

25. Probability of achieving statistically significant changes in base flow water quality

at selected reductions or increases in total- and dissolved-phosphorus concentrations

in base flow.............................................................. 63

26.-Estimated differences between nitrogen additions from fertilizer applications and legumes,

and nitrogen removal by crops for 1986-90 water years at Bald Eagle Creek ........... 64

27.-Nutrient yield as a function of annual and long-term discharge at four

predominately agricultural basins and a forested basin (Young Womans Creek

near Renovo) in the Susquehanna River Basin, 1986-89 water years ................. 67

Water-Resources Investigations Report 93-4069
TABLES

Page 

Table 1 .-Land use and crop acreage in the Bald Eagle Creek Basin during the 1986-90 water years ............. 10

2.-Crop yields of farms at the Bald Eagle Creek site.............................................. 13

3.--Animal density at the Bald Eagle Creek site.................................................. 13

4.--Total manure produced, its estimated nutrient content, and the nutrient content of manure applied to

cropland and deposited by grazing animals at the Bald Eagle Creek site ..................... 13

5. Manure and commercial fertilizer applications to cropland at the Bald Eagle Creek site................ 15

6.--Precipitation at Bald Eagle Creek and New Park gages and deviations from normal during the

growing and nongrowing seasons in the 1986-90 water years.............................. 20

7.--Water quality of precipitation in the Bald Eagle Creek Basin..................................... 22

8.--Contribution of base flow to total streamflow at Bald Eagle Creek during the 1986-89

water years..................................................................... 25

9. Water-quality characteristics of base flow at Bald Eagle Creek by growing and nongrowing season

and by water year................................................................ 30

10. Nitrogen, phosphorus, and suspended-sediment loads in base flow at Bald Eagle Creek prior to 

(October 1985 - September 1987) and during (October 1987 - September 1989) 

nutrient management............................................................... 34

11 .--Coefficients, standard deviations, and T values for the 7-parameter log-linear model used to

estimate concentrations and loads in base flow ........................................... 38

12.-Seasonal Kendall test results for nitrogen (as N) and phosphorus (as P) constituents in base flow

for the 1986-90 water years .......................................................... 40

13. Results of synoptic sampling of base flow at the Bald Eagle Creek gaging station, tributary I, and

tributary 2........................................................................ 41

14. Number of storms, number of sampled storms, number of samples collected, and the percentage

of total stormflow sampled at the Bald Eagle Creek site for the 1986-89 water years ............. 47

15.-Ranges of instantaneous streamflow and constituent concentrations in stormflow at Bald Eagle

Creek for the 1986-89 water years..................................................... 47

!6.~Daily nitrogen, phosphorus, and suspended-sediment loads during sampled storms at the Bald Eagle

Creek site for the 1986-89 water years.................................................. 48

17. Regression statistics for estimating daily nitrogen, phosphorus, and suspended-sediment loads as

a function of stormflow at the Bald Eagle Creek for the 1986-89 water years ................... 50

18. Measured and estimated nitrogen, phosphorus, and suspended-sediment loads in stormflow at

Bald Eagle Creek for the 1986-89 water years ........................................... 50

19. Total base flow and stormflow loads for total nitrogen, total phosphorus, and suspended sediment

in Bald Eagle Creek for the 1986-89 water years ......................................... 52

20. Results of soil sampling at the Bald Eagle Creek Basin, Nutrient-Management Subbasin,

and Brush Run study areas........................................................... 56

21 . Estimates of reductions required in mean concentrations and mean loads to achieve statistically

significant changes in base-flow water quality in the Bald Eagle Creek Basin................... 60

22. Water-quality characteristics of base flow at the Bald Eagle Creek site.............................. 61

23. Estimated nitrogen addition from applications of manure and commercial fertilizer and legumes, 

and estimated nitrogen removal from crops, base flow, and stormflow for the 

1986-90 water years at Bald Eagle Creek ............................................... 65

24. Average annual yields for total nitrogen, total phosphorus, and suspended sediment in streamflow

from five basins in the Lower Susquehanna River Basin for the 1986-89 water years............. 66

Water-Resources Investigations Report 93-4069
Multiply

inch (in.)

foot (ft)

mile (mi)

foot per mile (ft/mi)

acre

square mile (mi2 )

cubic foot per second (ft3/s)

gallon per minute per foot (gal/min)/ft

gallon per minute (gal/min) 

bushel (dry)

pound (Ib)

pound per acre (Ib/acre)

pound per ton (Ib/ton)

degree Fahrenheit (°F)

CONVERSION FACTORS, VERTICAL DATUM, 

AND ABBREVIATED WATER-QUALITY UNITS

B*

Length 

25.40

0.3048

1.609

0.1894 

Area

0.004047

2.590 

Flow

0.028317

0.2070 

Volume

0.06309

0.0284 

Mass

0.4536

1.123

0.50

Temperature 

°C = 5/9 (°F - 32)

To obtain

millimeter

meter

kilometer

meter per kilometer

square kilometer 

square kilometer

cubic meter per second 

liter per second per meter

liter per second 

liter

kilogram

kilogram per hectare

kilogram per megagram

degree Celsius

Abbreviated water-quality units used in report:

micrograms per liter (ug/L)

micrometers (Mm)

microsiemens per centimeter at 25 degrees Celsius (nS/cm) 

milligrams per liter (mg/L)

Sea Level: In this report "sea level" refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929)--

a geodetic datum derived from a general adjustment of the first-order level nets of both the United States 

and Canada, formerly called Sea Level Datum of 1929.

VII Water-Resources Investigations Report 93-4069
HYDROLOGY AND THE EFFECTS OF SELECTED

AGRICULTURAL BEST-MANAGEMENT PRACTICES

IN THE BALD EAGLE CREEK WATERSHED,

YORK COUNTY, PENNSYLVANIA, 

PRIOR TO AND DURING NUTRIENT MANAGEMENT

By Michael J. Langland and David K. Fishel

ABSTRACT

The U.S. Geological Survey, in cooperation with the Susquehanna River Basin Commission and the 

Pennsylvania Department of Environmental Resources, conducted a study as part of the U.S. Environmental 

Protection Agency's Chesapeake Bay Program to determine the effects of nutrient management on surface-water 

quality by reducing animal units in a 0.43 square-mile agricultural watershed in York County. The study was 

conducted primarily from October 1985 through September 1990 prior to and during the implementation of nutrientmanagement practices designed to reduce nutrient and sediment discharges. Intermittent sampling continued until 

August 1991.

The Bald Eagle Creek Basin is underlain by schist and quartzite. About 87 percent of the watershed is cropland 

and pasture. Nearly 33 percent of the cropland was planted in corn prior to nutrient management, whereas 22 percent 

of the cropland was planted in corn during the nutrient-management phase. The animal population was reduced by 

49 percent during nutrient management. Average annual applications of nitrogen and phosphorus from manure to 

cropland were reduced by 3,940 pounds (39 percent) and 910 pounds (46 percent), respectively, during nutrient 

management. A total of 94,560 pounds of nitrogen (538 pounds per acre) and 26,400 pounds of phosphorus 

(150 pounds per acre) were applied to the cropland as commercial fertilizer and manure during the 5-year study.

Core samples from the top 4 feet of soil were collected prior to and during nutrient management and analyzed for 

concentrations of nitrogen and phosphorus. The average amount of nitrate nitrogen in the soil ranged from 36 to 

135 pounds per acre, and soluble phosphorus ranged from 0.39 to 2.5 pounds per acre, prior to nutrient management. 

During nutrient management, nitrate nitrogen in the soil ranged from 21 to 291 pounds per acre and soluble 

phosphorus ranged from 0.73 to 1.7 pounds per acre. Precipitation was about 18 percent below normal and 

streamflow was about 35 percent below normal prior to nutrient management, whereas precipitation was 4 percent 

above normal and streamflow was 3 percent below normal during the first 2 years of nutrient management. Eightyfour percent of the 20.44 inches of streamflow was base flow prior to nutrient management and 54 percent of the 

31.14 inches of streamflow was base flow during the first 2 years of the nutrient-management phase. About 31 

percent of the measured precipitation during the first 4 years of the study was discharged as surface water; the 

remaining 69 percent was removed as evapotranspiration or remained in ground-water storage.

Median concentrations of total nitrogen and dissolved nitrate plus nitrite in base flow increased from 4.9 and 

4.1 milligrams per liter as nitrogen, respectively, prior to nutrient management to 5.8 and 5.0 milligrams per liter, 

respectively, during nutrient management. Median concentrations of ammonia nitrogen and organic nitrogen did not 

change significantly in base flow. Median concentrations of total and dissolved phosphorus in base flow did not 

change significantly and were 0.05 and 0.03 milligrams per liter as phosphorus, respectively, prior to the management 

phase, and 0.05 and 0.04 milligrams per liter, respectively, during the management phase.

Water-Resources Investigations Report 93-4069
Concentrations and loads of dissolved nitrite plus nitrate in base flow increased following wet periods after crops 

were harvested and manure was applied. During the growing season, concentrations and loads decreased as nutrient 

utilization and evapotranspiration by corn increased. About 4,550 pounds of suspended sediment, 5,300 pounds of 

nitrogen, and 70.4 pounds of phosphorus discharged in base flow in the 2 years prior to nutrient management. During 

the first 2 years of nutrient management about 2,860 pounds of suspended sediment, 5,700 pounds of nitrogen, and 

46.6 pounds of phosphorus discharged in base flow. Prior to nutrient management, about 260,000 pounds of 

suspended sediment, about 2,180 pounds of nitrogen, and about 235 pounds of phosphorus discharged in stormflow. 

During the first 2 years of nutrient management about 464,000 pounds of suspended sediment, 6,120 pounds of 

nitrogen, and 912 pounds of phosphorus discharged in stormflow.

The seasonal rank-sum test indicated that significant differences were detected in the medians of total nitrogen 

and dissolved nitrite plus nitrate in base flow prior to and during nutrient management. The seasonal Kendall test 

indicated significant upward trends in concentrations and loads of total nitrogen and dissolved-nitrite plus nitrate 

measured in base flow during the entire study. Neither significant differences nor trends were detected in the 

concentrations and loads for ammonia, ammonia plus organic nitrogen, phosphorus, or suspended sediment in base 

flow.

Water-Resources Investigations Report 93-4069
INTRODUCTION

The U.S. Geological Survey (USGS), in cooperation with the Susquehanna River Basin Commission (SRBC) 

and the Pennsylvania Department of Environmental Resources (PaDER) Bureau of Land and Water Conservation, 

conducted a study to determine the effects of agricultural best-management practices on surface-water quality in the 

Bald Eagle Creek watershed (site 1, fig. 1) from October 1, 1985, to September 30, 1990. The site is underlain by 

noncarbonate rock and is one of three small agricultural watersheds in the Lower Susquehanna River Basin that were 

studied prior to and during the implementation of nutrient management at the watersheds. This report includes a 

comparison of land-use and water-quality data from Bald Eagle Creek with data from Brush Run (site 2, fig. 1, also 

underlain by noncarbonate rock) and the Nutrient-Management Subbasin located in a carbonate-rock area (site 3, 

fig. 1) that is part of the Conestoga River headwaters being studied by Fishel and others (1992) as part of the Rural 

Clean Water Program (RCWP).

The full history of this study's conception is described in the characterization report (Fishel and others, 1991). In 

1982, the RCWP initiated a 10-year study of the Conestoga River headwaters to determine the effects of agriculturalmanagement practices on surface-water and ground-water quality. One of three components of the Conestoga River 

Headwaters Project was to evaluate the effects of nutrient management in a small intensively farmed watershed, the 

Little Conestoga Creek watershed, underlain by carbonate rock. Inasmuch as there was a need for a corresponding 

program in areas underlain by noncarbonate rocks in the Lower Susquehanna River basin, this study and a study of 

the Brush Run watershed were initiated by the USGS in 1985 (Fishel and others, 1992). The study was part of the 

U.S. Environmental Protection Agency (USEPA) Chesapeake Bay Program. The results from this study were planned 

to be compared to results from the carbonate-rock areas being studied for the RCWP, such as the NutrientManagement Subbasin in the Little Conestoga Creek headwaters, and to results from Brush Run Creek, a second site 

in noncarbonate rock.

Initially, agricultural-management plans were to be designed and implemented at two of the farms in the 

0.43-mi2 Bald Eagle Creek study area and were to consist of a combination of management practices. Management 

plans included recommendations to install terraces, diversions, sediment-detention ponds, animal-waste storage 

facilities, barn gutters, and other innovative techniques to control nutrient and sediment loads in surface runoff. The 

installation of the management practices were to reduce the amount of nutrients available for leaching to the ground 

water and also discharged in base flow or storm runoff. Nutrient applications were to be balanced with crop requirements to obtain maximum crop yields. However, in September 1987, one of the cooperating fanners was permitted to 

withdraw from his Chesapeake Bay Program cost-sharing management plan after developing a medical difficulty. He 

later sold his dairy herd and changed his cropping patterns from predominantly corn to alfalfa. Subsequently, a 

second farmer within the study area sold his farm. The new owner reduced the number of animal units by reducing 

the dairy population at the farm. Monitoring continued at the site to determine the effects that these management 

changes-a reduction of animal units, manure applications, and corn production-would have on surface-water quality 

in the Bald Eagle Creek Basin.

Because a management practice was not implemented to control storm-water runoff, the monitoring effort was 

reduced and the project scope changed. The continuous streamflow gage and precipitation gage were discontinued in 

September 1989. After September 1989, the project scope concentrated on base-flow quality; however, in order to 

fully understand the hydrologic conditions at the site additional data from the ground-water system needed to be 

collected. Attempts were then made to collect limited ground-water information so that changes observed in water 

quality could be correlated with land-use activities that could potentially effect the base flow. Even though the 

ground-water basin was somewhat different than the surface-water basin, the assumption was made that any changes 

in the water quality of base flow were caused by land-use changes within the surface-water basin. Measurement of 

intermittent base-flow quantity and quality continued until August 1991 in an attempt to detect changes in water 

quality from the reduction in applications of animal waste.

Water-Resources Investigations Report 93-4069
Purpose and Scope

This report provides an evaluation of the effects of agricultural-management practices, with emphasis on the 

effects of reductions of (1) animal units, (2) nutrient applications, and (3) com production on the surface-water 

quality of a 0.43-mi2 watershed (fig. 2) in the Bald Eagle Creek headwaters near Fawn Grove, in York County, Pa. 

Data collected from the premanagement phase (October 1,1985, through September 30, 1987) is compared with data 

collected during the management phase (October 1, 1987, through September 30, !990)This report describes the 

study area, the data-collection methods used, and effects of nutrient-management practices on soil nutrients, and 

precipitation and surface-water quality. Target goals were established to determine the effects of nutrientmanagement practices on surface-water quality. This report will aid agricultural managers in the development of 

management plans for other farms. It will also help to determine whether voluntary implementation of management 

practices are successful in improving the water quality of the Lower Susquehanna River Basin.

Approach

Extensive land-use, hydrologic, and soil data were collected and used to evaluate the effects of nutrientmanagement practices on the water quality of stormflow and base flow at the Bald Eagle Creek site. Both historical 

and current data were used in the evaluation. Land-use data compiled from three farms at the site included crop 

acreage and yields, animal density, manure production, and nutrient applications. Soil-chemistry samples were used 

to identify areas where nutrient management may be most beneficial. Hydrologic data were collected and used to 

determine the quantity and quality of precipitation, base flow, and stormflow. Samples of base flow and stormflow 

were collected to document the water chemistry prior to and during the management phase. Nutrient and suspendedsediment loads were calculated to determine changes in yields of nutrients and suspended sediment as the result of the 

management practices.

Data were plotted and parametric and nonparametric statistics were calculated to identify seasonal variations and 

trends. Data were grouped into growing (April through September) and nongrowing (October through March) 

seasons. A modified form of the nonparametric-Wilcoxon-Mann-Whitney-rank-sum test for seasonal data (Crawford, 

Slack, and Hirsch, 1983) and Monte-Carlo simulations (R.M. Hirsch, U.S. Geological Survey, written commun., 

1989) were used to estimate reductions necessary to observe statistical changes in concentrations and loads of 

nitrogen and phosphorus in base flow, on the basis of variances of the data collected prior to nutrient management. 

The Seasonal Kendall test was used to test for monotonic trend in water quality over the 5-year sampling period.

Related Studies

Studies related to this project include the comprehensive RCWP monitoring projects to determine the effects of 

agricultural best-management practices on water quality in Idaho, Illinois, South Dakota, Vermont, and Pennsylvania. 

The Pennsylvania and South Dakota projects are the only RCWP projects investigating nutrient transport in ground 

water.

Another related study is being conducted by the USGS in the Patuxent River Basin in Maryland (Steve Preston, 

U.S. Geological Survey, oral commun., 1987) in which nonpoint-source nutrient contamination and sediment loads in 

a 980 mi2 watershed are being investigated. A study also is being conducted by the USGS and the SRBC to assess the 

sources of nutrient loads transported from selected watersheds of the Susquehanna River Basin to the Chesapeake 

Bay (Lloyd Reed, U.S. Geological Survey, oral commun., 1992). Studies by the PaDER, in cooperation with the 

Lancaster and Lebanon County Conservation Districts (D. Gregg, Pennsylvania Department of Environmental 

Resources, Bureau of Forestry, written commun., 1986) also are being conducted to determine the effects of manure 

disposal on ground water and undisturbed soils.

Water-Resources Investigations Report 93-4069
Acknowledgments

The authors thank the following individuals and respective agencies for their assistance and cooperation:

1. Landowner Kenneth Smith, who permitted the gage to be constructed on his property.

2. Four farmers, John Wilcox, Amos King, Kenneth Moore, and John Stolzfus, who volunteered to provide 

land-use data and access to their farms.

3. Riggs Harwell, District Conservationist for the U.S. Department of Agriculture, Soil Conservation

Service, who assisted with project planning, gathering crop-yield data, and developing management plans.

4. Dr. Dale Baker and Leon Marshall from the Pennsylvania State University, Department of Agronomy, who 

collected and analyzed soil samples.

Water-Resources Investigations Report 93-4069
DESCRIPTION OF STUDY AREA

Bald Eagle Creek is located in south-central Pennsylvania and is part of the Lower Susquehanna River Basin 

(fig. I). The stream flows northeastward and drains into Muddy Creek, then flows southeastward, draining into the 

Susquehanna River approximately 6 mi upstream from the Maryland-Pennsylvania state boundary.

The Bald Eagle Creek watershed is 0.43 mi2 and is located in southern York County and is about 1.5 mi 

northwest of Fawn Grove. The streamflow-gaging station (fig. 2) was 0.6 mi downstream from the headwaters.

77*28 76*11

40* IS1

10 20 MILES

EXPLANATION 

j^] CARBONATE ROCK 

Q NONCARBONATE ROCK

_.. LOWER SUSQUEHANNA 

RIVER BASIN

'? OBSERVATION WELL AND 

IDENTIFIER

A APPROXIMATE LOCATION 

OF SAMPLING SITE

Figure 1. Locations of Bald Eagle 

Creek Site 1, Brush Run Site 2, and 

the Little Conestoga Creek 

(Nutrient-Management Subbasin) 

Site 3 in the Lower Susquehanna 

River Basin.

76°28'

30*4S-20*

^1^ STUDY AREA 7

500 METERS

EXPLANATION 

© POND

 FOREST BOUNDARY

 SUBBASIN BOUNDARY

$ STREAMFLOW GAGE AND

WATER-QUALITY SAMPLING 

SITE

3 

PRECIPITATION GAGE 

SOIL-SAMPLING SITE

Figure 2. Locations of farms, 

streamflow and precipitation gages 

and sampling sites, and soilsampling sites in Bald Eagle Creek 

Basin.

Water-Resources Investigations Report 93-4069
Climate

Climate at the Bald Eagle Creek site is relatively mild but humid and is classified as humid continental. 

Summers are relatively long and warm as evidenced by a growing season that begins in April and ends in September; 

winters are comparatively short. The average growing season ranges from 169 days near York to about 175 days at 

Hanover (U.S. Department of Agriculture, 1963). Normal precipitation is 44 in/yr at New Park and is evenly 

distributed and provides for sufficient rain during the growing season. However, occasional dry periods can cause 

major crop damage as evidenced during the study.

Geologic Setting

The geologic setting of the Piedmont Uplands in which the study area lies is described by Hall (1934), Lloyd and 

Growitz (1977), Taylor and Werkheiser (1984), and Gerhart and Lazorchick (1984). In summary, each described the 

geology of the Piedmont Uplands section as being extremely complex. The area is composed primarily of 

metamorphosed sedimentary rocks but also contains some igneous rocks and quartzite. The Bald Eagle Creek site is 

underlain by Wissahickon Formation of the Lower Paleozoic age. The Wissahickon Formation consists primarily of 

albite-chlorite schist and oligoclase-mica schist, also known as "Gneissic Rocks." This formation is not a natural 

source of nitrate or phosphorus to the ground water. 

Geologic Structure

The major geologic structure in the area is the Martic overthrust a block of rock that was believed to have been 

thrust into position from the southeast by mountain-building forces. Other minor structural features within the area 

are the Tuncquan anticline and the Peach Bottom, Wentz, and Yoe synclines. Within these features, the rocks are 

complexly folded and may be broken by minor faults. These Gneissic Rocks are regionally metamorphosed, 

indicating textural and compositional banding (Gary Barton, U.S. Geological Survey, written commun., 1992).

Geologic structure has an important influence on yields of wells, ground-water movement, and quantity of base 

flow. Faults may contain zones of fractured rock where large amounts of water may be stored. If faults become filled 

with clay, calcite, or quartz then little or no water can infiltrate and be stored causing base flow to decline rapidly. In 

areas where fold hinges are present, secondary permeability may develop because of numerous fractures, welldeveloped cleavage, and the presence of horizontal or nearly horizontal bedding that can increase well yields and may 

contribute to extended periods of high base flow.

Basin Morphology and Topography

The Bald Eagle Creek watershed lies in the Southeastern Upland subdivision of the Piedmont physiographic 

province of the Appalachian Highlands. The topography consists of broad ridgetops and steep hillsides. The 

underlying rocks are largely erosion-resistant schist and quartzite.

Differences between basin morphology and topography of the Bald Eagle Creek and the Brush Run site are 

illustrated in figure 3. Generally, the Bald Eagle Creek Basin is rotund in shape with little stream bifurcation, has 

steep hillslopes and traverses west to east. Land-surface elevations at Bald Eagle Creek range from 800 ft above sea 

level near the upper end of the basin to 591 ft above sea level at the streamflow-gaging site. Bald Eagle Creek 

descends rapidly from its headwaters to the gaging site, an average gradient of 152 ft/mi. Immediately downstream 

from the gage, elevations decrease and the gradient flattens to about 55 ft/mi from the gage to Muddy Creek. The 

steep channel slope causes the flood plain of Bald Eagle Creek to be prone to flash-flood conditions, especially during 

thunderstorms.

Water-Resources Investigations Report 93-4069
76°28'30" 76°28'00"

39°45f2(r -

39°44'50' -

BALD EAGLE CREEK 

i I

77°07> 77006'

39°49'20"

39°48'20"

EXPLANATION 

 " DRAINAGE BASIN 

TOPOGRAPHIC

Contour interval 20 feet. 

Elevation in feet above 

National Geodetic 

Vertical Datum of 1929

 ROAD

 STREAM

 TRIBUTARY 

POND

STREAMFLOW-GAGING 

STATION

Figure 3. Basin topography and basin configuration at Bald Eagle Creek (top) 

and Brush Run (bottom) sites.

Water-Resources Investigations Report 93-4069
Bald Eagle Creek originates from a series of small springs. Several large springs discharge continuously forming 

two tributaries between the headwaters and the streamflow-gaging site. Another significant physical feature within 

the study area is the farm pond located at farm 2 (fig. 2). This pond is spring fed and, although it does not discharge 

from an outflow at the land surface, seepage from the pond has been observed to discharge directly to the Bald Eagle 

Creek.

At the Brush Run site, the basin is long, flat, and elongated, with no bifurcation. The Brush Run Creek traverses 

from southwest to northeast. Land-surface elevations range from 635 ft above sea level at the upper end of the 

watershed to 600 ft near the gaging site; a gradient of approximately 40 ft/mi. The farmer has installed a series of tile 

lines to help drain water from low lying fields into the stream.

Soils

The soils at the site are predominantly Glenelg channery and Elioak silt loam (fig. 4). Glenville and Chewacla 

silt loams and Manor channery loam also are present in smaller amounts, primarily in the valleys. These soils are 

described as being deep and well drained (U.S. Department of Agriculture, 1963, p. 99-101). However, when soil 

samples were collected at farm 2, bedrock was, in places, less than 3 ft below the surface. The parent material for the 

soils weathered from schist and phyllite. The Elioak silt loams have slopes ranging from 3 to 15 percent, the Glenville 

silt loams have slopes of 0 to 3 percent, and the Manor channery loams have slopes of 8 to 25 percent.

The predominant soils near the gage are from the Chewacla Series soils, which are acid and moderately fertile, 

but because they are located on narrow bottom lands they are not suitable for cultivation. The York County Soil 

Survey (U.S. Department of Agriculture, 1963, p. 92) suggests at sites where this soil extends to the stream bank, 

such as at the streamflow-gaging site, deepening of the stream channel is advisable, in addition to other drainage 

practices. It also recommends that because these soils remain moist, they provide pastures for grazing until 

midsummer, but to prevent erosion, the pastures should not be grazed until the ground is firm. Several steer pastured 

near the gage continuously.

76°28f35" 76° 28'

EXPLANATION

rr-i GLENELG CHANNERY 

"^ SILT LOAM

D ELIOAK SILT LOAM 

g CHESTER SILT LOAM 

0 CHEWACLA SILT LOAM 

^ GLENVILLE SILT LOAM

g^ MANOR CHANNERY 

LOAM

 - DRAINAGE BASIN

39°45'20" -

39°44'50"

Figure 4. Distribution of 

soil types in Bald Eagle 

Creek site.

1.000

l

500

2,000 FEET 

METERS

Water-Resources Investigations Report 93-4069
LAND USE, CROPS, AND NUTRIENT APPLICATIONS

During this study, the predominant land use within the Bald Eagle Creek Basin was agriculture. Between 63 to 

66 percent of the basin was cropland, 21 to 24 percent was pasture, and 13 percent was forest (table 1).

Table 1. Land use and crop acreage in the Bald Eagle Creek Basin during the 1986-90 water years 

[--, crop not planted; percent, percentage of total land-use area]

Prior to nutrient management

1986 

Land use (Acres) (Percent)

Cropland

Alfalfa

Barley

Corn

Oats/Alfalfa

Potatoes

Rye

Soybeans

Wheat

Subtotal

Pasture

Forest

Total

45.5

12.8

94.2

1.7

18.3

3.3

175.8

64.1

35.3

275.2

16.6

4.7

34.2

.6

-

6.6

1.2

63.9

23.3

12.8

100.0

1987 

(Acres) (Percent)

30.0

92.6

11.7

12.8

34.2

-

181.3

58.6

35.3

275.2

10.9

33.6

4.3

4.7

12.4

--

65.9

21.3

12.8

100.0

During nutrient management

1988 

(Acres) (Percent)

38.3

67.3

4.0

~

54.4

8.8

172.8

67.1

35.3

275.2

13.9

--

24.5

~

1.5

-

19.8

3.2

62.8

24.4

12.8

100.0

1989 

(Acres) (Percent)

53.4

-

41.9

~

-

2.8

62.3

12.4

172.8

67.1

35.3

275.2

19.4

-

15.2

-

1.0

22.7

4.5

62.8

24.4

12.8

100.0

1990 

(Acres) (Percent)

55.6

--

74.8

~

-

42.4

-

172.8

67.1

35.3

275.2

20.2

--

27.2

-

«

15.4

-

62.8

24.4

12.8

100.0

Parts of four farms are located within the watershed (fig. 2). Farm 4 consists of the pasture where the gaging site 

is located. This landowner generally raised three cattle and six hogs annually.

An average of about 34 percent (93 acres) of the cropland was planted in corn (fig. 5) prior to nutrient management, which decreased to an average of about 22 percent (60 acres) of the cropland during the management phase 

(fig. S). During management years 1988,1989, and 1990, the amount of cropland planted in com was 67.3,41.9, and 

74.8 acres, respectively (table 1). Rye was commonly planted as a cover crop on com fields to prevent fall and winter 

erosion. At the dairy farms (farms 1 and 2), crops were generally rotated on a 2-year corn and 3-year alfalfa sequence. 

Com yields in the Bald Eagle Creek Basin prior to and during nutrient management are listed in table 2. They were 

slightly lower than the 146 bushels per acre average yields reported for 11 farms in the Nutrient-Management 

Subbasin in Lancaster and Berks Counties by Fishel and others (1992).

Farms 1 and 2 had dairy herds with 97 and 80 cows prior to the management phase. On December 8, 1987, the 

fanner at Farm 1 (fig. 2) sold 47 cows and began raising the remaining heifers for beef. On February 2, 1990, Farm 2 

was sold and the new farm operator reduced the animal population from 99 dairy units to 67 dairy units and 10 horse 

units (table 3). One animal unit represents 1,000 Ib of body weight regardless of animal type. Meanwhile, an increase 

in the number of steer grazing in the pasture (farm 4) at the water-quality gage increased from 3 to 12 beginning in 

November 1989. Farm 3 had no animals and relied entirely on commercial fertilizer for nutrient sources.

The animal density, which is based on crop acreage and pasture land available for disposal of manure within the 

basin, was about 0.85 AU/acre (animal units per acre) prior to the management phase, and 0.43 AU/acre at the end of 

the management phase. In both cases, the animal units were much less than the 2.50 AU/acre average for 10 farms in 

the RCWP's Nutrient-Management Subbasin of the Little Conestoga Creek Basin (site 3, fig. IXFishel and others, 

1992). They were also less than the 1.5 AU/acre recommended in the Conestoga Headwaters Plan of Work (U.S. 

Department of Agriculture, 1982) for nonpoint-source discharges. Although all the animals were housed in the basin, 

the fanners in the Bald Eagle Creek Basin owned additional land outside the subbasin on which they could spread

Water-Resources Investigations Report 93-4069 10
manure. Therefore, if animal densities were calculated from total farm acreage or total farm cropland, rather than 

crop and pasture land located within the subbasin, the animal densities would be lower than those reported in this 

report.

The land used for pasture near the gage had a low slope and would often flood during high flows. In order to 

stabilize the stream channel and prevent further damage to the pasture, the landowner attempted to reroute the 

channel by use of a bulldozer. He also hauled in and deposited soil to confine the stream by increasing the height of 

the stream bank. The nutrient content of these exposed soils was unknown. Another attempt was made to reduce 

damage from flash-floods in the pasture late in July 1988 when a second culvert was added to the bridge located 

immediately downstream from the gage. Again, soils were exposed and susceptible to erosion during construction 

time.

According to the land-use data supplied by the farmers (table 4), less nitrogen and phosphorus from manure 

was applied to the crop and pasture land within the subbasin than was produced by the animal population housed 

within the subbasin. The land-use application data may contain some errors, because the amount of nitrogen and 

phosphorus applied within the subbasin plus the amount of nitrogen and phosphorus deposited by grazing animals 

was less than the amount produced. Perhaps some additional manure was spread outside the subbasin divide.

Most of the manure and commercial fertilizers were applied to the cropland between March and June (fig. 6). 

However, manure that was stored during the growing season was applied in September after the corn was harvested. 

Farmers reported that approximately 61,740 Ib of nitrogen and 16,610 Ib of phosphorus were applied as manure and 

commercial fertilizer to cropland during the 2 years prior to the management phase (table 5), and 32,820 Ib of 

nitrogen and 9,790 Ib of phosphorus were applied during the 3-year management phase. It was estimated that an 

additional 20,940 Ib of nitrogen and 3,680 Ib of phosphorus were deposited by cattle in pastures near the stream prior 

to the management phase (Owen Brubaker, United States Department of Agriculture, Agricultural Stabilization and 

Conservation Service, written commun., 1985). Likewise, an estimated 18,900 Ib of nitrogen and 3,330 Ib of 

phosphorus were contributed by the grazing animals during the 3-year management phase (table 4). Thus, prior to 

nutrient management, a total of 82,680 Ib of nitrogen (172 Ib/acre/yr) and 20,290 Ib of phosphorus (42 Ib/acre/yr) 

were applied to cropland and pastures; 50 percent of the nitrogen and 62 percent of the phosphorus were from 

commercial fertilizer. During the management phase, a total of 51,700 Ib of nitrogen (72 Ib/acre/yr) and 13,120 Ib of 

phosphorus (18 Ib/acre/yr) were applied to cropland and pastures; 28 percent of the nitrogen and 50 percent of the 

phosphorus were from commercial fertilizer. For the 5 years of land-use data collection, 94,560 Ib of nitrogen and 

26,400 Ib of phosphorus were applied to the cropland and an additional 39,840 Ib of nitrogen and 7,010 Ib of 

phosphorus were deposited in pastures.

The farmers began reducing their nutrient applications voluntarily before recommendations were made by a 

nutrient-management specialist. About 31 percent less nitrogen and 3 percent more phosphorus from commercial 

fertilizer and manure were applied during the second year than during the first year of the study. Similar unsolicited 

reductions in applications of nutrients to cropland, especially commercial fertilizer, occurred prior to the implementation of nutrient management in the Nutrient-Management Subbasin for the RCWP (Fishel and others, 1991). 

The average amount of nitrogen and phosphorus applied annually as commercial fertilizer and manure decreased 

from 30,870 and 8,305 Ib/yr, respectively, prior to nutrient management to 10,940 and 3,264 Ib/yr, respectively, 

during the management phase.

Sixty-two percent less nitrogen and 61 percent less phosphorus were applied as commercial fertilizer and manure 

during the first 2 years of the management phase than during the 2 years prior to the management phase. The 

reductions in land applications of commercial and manure fertilizers resulted in a corresponding reduction in 

available nutrients, but changes in cropping patterns could have resulted in an increase of available nutrients for crops 

(discussed later in report). An average of 93.4 acres was planted in corn, a major consumer of nitrogen, prior to 

nutrient management. During the first 2 years of nutrient management, corn was planted on an average of 54.6 acres, 

a reduction of 42 percent. Also, because the farmers changed application rates from field to field as cropping patterns 

changed, it was difficult to evaluate the effects of the changes in nutrient applications to specific changes measured in 

surface-water quality.

The contribution of nutrients from human waste was not considered to be a major source because the population 

density was sparse at the site.

Water-Resources Investigations Report 93-4069
1986 1989

1987 1990

EXPLANATION

ALFALFA fjf RYE

BARLEY [^%i SOYBEANS

CORN ||||||| WHEAT

j ^ | OATS/ALFALFA |;X'-V-;.j WOODS

^^ POTATOES | | PASTURE OR

^-,~u ROAD

Figure 5. Land-use maps showing different cropping panerns at Bald Eagle Creek for 

(a) the premanagement period, 1986 and 1987 water years and (b) the nutrientmanagement period, 1988,1989, and 1990 water years.

Water-Resources Investigations Report 93-4069 12
Table 2. Crop yields of farms at the Bald Eagle Creek site 

[Yields are in units per acre; -, crop not planted; --, no data provided]

Farm

1

2

3

Crop

corn

silage

soybeans

alfalfa

oats

corn

silage

rye

alfalfa

corn

potatoes

barley

wheat

Yield prior to 

nutrient management

100 bushels

20 tons

50 bushels

3.5 tons

1 ton

1 8 tons

4 tons

--

140 bushels

2,000 pounds

70 bushels

60 bushels

Yield during 

nutrient management

~

45 bushels

3 tons

2 tons

100 bushels

14 tons

3 tons

3.5 tons

130 bushels

~

100 bushels

30 bushels

Table 3. Animal density at the Bald Eagle Creek site

[Animal units, in thousands of pounds of body weight; cropland, in acres; and animal density, in animal units per acre of crop 

and pasture land]

Farm Animal type

1 Dairy

Cows

Heifers

Subtotal

2 Dairy

Cows

Heifers

Horses

Subtotal

3

4 

Total

Prior to nutrient management

Animal 

units

63.5

36.0

99.5

87.5

12.0

0.0

99.5

.0

4.0

203.0

Crop and 

pasture land

96.8

93.8

34.5

14.8

239.9

Animal 

density

1.03

1.06

.0

.27

.85

End of nutrient management

Animal 

units

0.0

20.0

20.0

50.0

17.0

10.0

77.0

.0

6.0

103.0

Crop and 

pasture land

96.8

93.8

34.5

14.8

239.9

Animal 

density

0.21

.82

.0

.40

.43

Table 4. Total manure produced, its estimated nutrient content, and the nutrient content of manure applied to 

cropland and deposited by grazing animals at the Bald Eagle Creek site

[N, nitrogen; P, phosphorus; Manure produced, in tons; nitrogen and phosphorus, in pounds]

Year

1986

1987

1988

1989

1990

Manure 

produced

2,590

2,910

1,940

1,630

1,380

Nutrient content 

of 

manure produced

N

25,900

29,100

19,400

16,300

14,000

P

4,560

5,130

3,410

2,870

2,470

Nutrient content 

of 

manure applied

N

11.590

8,440

4,530

6,440

7.260

P

2,040

1,920

790

1,130

1,280

Nutrient content of manure 

deposited by Total applied 

grazing animals and deposited

N

9,840

11,100

7,360

6,200

5,320

P

1,730

1,950

1,300

1,090

940

N

21,400

19,540

11,890

12,640

12,600

P

3,770

3,870

2,090

2,220

2,220

13 Water-Resources Investigations Report 93-4069
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IS Water-Resources Investigations Report 93-4069
NETWORK DESIGN, INSTRUMENTATION, SAMPLING AND ANALYTICAL TECHNIQUES

The following section describes the network design, instrumentation and sampling techniques, and all analytical 

techniques used in this report.

Precipitation

Precipitation data were collected from October 1985 through September 1989 at one location (fig. 2) by use of a 

tipping-bucket rain gage in conjunction with punched tape level recorder. The precipitation gage was located 

approximately 25 ft from the streamflow-gaging station near the eastern boundary of the site. Precipitation was 

recorded at 15-minute intervals to determine the duration and intensity of storms, and the daily, monthly, and annual 

totals. Precipitation was estimated for periods of missing record by use of data from the National Oceanic and 

Atmospheric Administration (NOAA) station at New Park and from daily records kept by the landowner of farm 3 

(fig. 2). Precipitation measured at the Bald Eagle Creek site was compared to normal precipitation measured at the 

NOAA station at New Park. The station at New Park is located approximately 2.5 mi southwest of the site.

Precipitation samples were collected by use of an 8 in. plastic funnel. The funnel collected rainfall continuously 

into a 1-liter precombusted glass bottle that was placed at ground level in a metal can packed with ice. Two 

precipitation samples were collected prior to the management phase. The first sample was collected in May 1987 near 

the beginning of the growing season, and the second was collected in September 1987, near the end of the growing 

season. Four precipitation samples were collected during the management phase: March 26,1988; May 2, 1989; 

August 15, 1989; and May 6, 1990. The pH and specific conductance were determined for each sample in the field 

immediately after sample collection. Precipitation samples were chilled to 4°C, preserved with mercuric chloride, and 

sent to the USGS National Water-Quality Laboratory in Arvada, Colo., for analyses of total nitrate plus nitrite, 

ammonia, ammonia plus organic nitrogen, and total phosphorus. Nutrients were analyzed according to methods 

described by Skougstad and others (1979).

Streamflow

The methods and instrumentation used to collect continuous streamflow data are described in the 

characterization report (Fishel and others, 1991). The streamflow-gaging station (USGS 01577400) (fig. 2) became 

operational on October 24, 1985, and was located on the right bank (fig. 2) at latitude 39°44'54" and longitude 

76°27'50", about 15 ft upstream from Kunkle Road. Continuous streamflow record was discontinued September 30, 

1989, but base flow measurements were made monthly for an additional year.

The control during high flows was a 5.8 ft diameter nonstandard geometric culvert located at the bridge at 

Kunkle Road. Late in July 1988, a second culvert was installed by the state highway department to reduce flooding in 

the pasture. The installation of this new culvert made it necessary to develop a new rating curve for high flows above 

25 ft3/s.

Long-term streamflow record from the Principle Creek near Principio Furnace, Md., was used to compare the 

measured streamflow because long-term record was not available for the gage at Bald Eagle Creek. The gage at the 

Principio Creek was about 21 mi southeast of the study area and has been in operation since June 1967.

Water Quality

Water-quality data collection began in November 1985 and ended in September 1990. Water-quality samples 

were collected manually at the V-notch weir during base flows. A float/stage-triggered PS-69 automatic pumping 

sampler was used to collect streamflow samples during storms at 30-minute intervals. The perforated intake for the 

pumping sampler was located near the centroid of flow in the pool created by the weir so that representative samples 

could be collected. Streamflow samples were collected monthly during base flow and at selected stages during storms 

to characterize stormflow. Sampling frequency was such that seasonal relations between water quality and streamflow 

could be determined.

Water-quality samples were collected during base flow by use of methods described by Guy and Norman (1970). 

Manual samples were collected and compared with discrete automatically-collected samples to assure that the 

automatic samplers were operating properly. Samples to be analyzed for dissolved constituents were filtered with a

Water-Resources Investigations Report 93-4069 16
0.45-nm membrane filter mounted in a peristaltic filter assembly. Base-flow samples were filtered in the field and 

stormflow samples were filtered in the laboratory at Lemoyne, Pa., before being sent to the laboratory in Denver, 

Colo. Like the precipitation samples, all base-flow and stormflow samples were preserved with mercuric chloride 

and kept chilled at 4°C.

Water-quality samples were analyzed for concentrations of suspended sediment, total and dissolved nitrate plus 

nitrite, ammonia plus organic nitrogen, ammonia, phosphorus, and dissolved orthophosphorus. Suspended-sediment 

samples were analyzed for concentration as well as sand and silt fraction at the USGS Sediment Laboratory in 

Lemoyne, Pa., by use of methods described by Guy (1969). Water-quality samples for nutrient analysis were sent to 

the USGS laboratory in Colorado within 24 hours after collection and analyzed by use of the same methods as 

described for the precipitation samples.

Nutrient and suspended-sediment loads in stormflow were computed by use of discharge and concentrationintegration methods described by Porterfield (1972) and estimated by use of regression techniques (SAS 1979). 

Missing storm concentration data were estimated by use of hydrograph comparisons of storms with similar 

magnitudes at similar times of the year.

Nutrient and suspended-sediment loads in base flow were computed by use of a 7-parameter log-linear model 

developed by Cohn and others (1989) to describe nutrient and sediment loads from the four river-input monitoring 

stations to the Chesapeake Bay. This model was validated by Cohn and others (U.S. Geological Survey, written 

commun., 1990) with repeated split-sample studies and is of the form

ln[C] = po + PL ln[Q / Q] + p2 (ln[Q / Q])2 + p3 [T - T] +

P4 [T- T] + P5 sin[2 n T] + P6 cos[2 n T] + e, (1)

where

In denotes natural logarithm function; 

C is constituent concentration; 

Q is discharge, in cubic feet per second; 

Q is mean discharge, in cubic feet per second; 

T is time, in years; and 

T is mean time, in years;

Po through P6 are the parameters of the model that were estimated from the data, and E denotes the model errors, 

which are assumed to be independent and normally distributed with zero mean and variance ae . Loads were 

calculated by substituting ln[C] from equation (1) into

L = antilog ln[C] Q - 5.4, (2)

where L is load, in pounds per day;

In denotes natural logarithm function;

Q is discharge, in cubic feet per second; and

5.4 is a constant.

Soil Nutrients

Soil samples were collected from two fields at two farms (fig. 2) to determine the nutrient content of the soil 

where manure and commercial fertilizer were applied. Soil nutrient results provided information for the nutrientmanagement specialist so that management plans could be developed for each farm.

Soil-nutrient samples from the upper 4 ft were collected in the fall of 1985, and the spring and fall of 1987, 

1988, 1989, and 1990. The samples were collected with the aid of a tractor mounted deep-soil probe. Each 4-ft 

sample core was divided into segments that represented 0 to 8 in., 8 to 24 in., and 24 to 48 in. below the surface. Two 

sets of three cores were taken at each location (fig. 2) and the segments from each core were composited in the field. 

The segments were analyzed for average soluble nitrate-nitrogen and phosphorus at the Pennsylvania State 

University, Soils and Environmental Chemistry Laboratory by use of methods described by Corey (1977) and by the 

USEPA (1979). Depths at which soil nutrients were concentrated were determined.

17 Water-Resources Investigations Report 93-4069
METHODS OF DATA ANALYSIS

The following section gives detailed explanations of the statistical tests and data analysis techniques used in the 

report.

Descriptive Statistics

In order to describe the hydrology of the Bald Eagle Creek, numerous descriptive statistics including maximum, 

minimum, and median values for streamflow, chemical concentrations, loads, and yields were calculated by use of the 

Statistical Analysis System (SAS) Institute, Inc. (1979; 1982a; 1982b) and P-STAT, Inc. (1986) statistical packages. 

Descriptive statistics were calculated for the entire study period, the periods prior to and during nutrient management, 

and the growing and nongrowing seasons. Frequency distributions were plotted to determine if chemical-quality data 

were normally distributed and to decide if data should be analyzed by use of parametric or nonparametric statistical 

procedures.

Correlation Analyses

Correlation analyses were performed to examine relations among concentrations and discharges of suspended 

sediment and nutrients, and streamflow and time. Relations were considered good if the correlation coefficient (r) was 

equal to or greater than 0.80, a value commonly used for chemical and biological studies.

Seasonal Wilcoxon-Mann-Whitney-Rank-Sum Test

Prior to implementation of nutrient management, estimates were made of the necessary amount of reduction 

needed to detect significant changes in concentrations and discharges of total nitrogen, dissolved nitrite plus nitrate 

nitrogen, and total and dissolved phosphorus in base flow. These estimates were established as targets for the nutrientmanagement phase assuming that variances in the data during nutrient management would be similar to variances 

prior to nutrient management. Data collected during the nutrient-management phase were tested to determine if data 

were significantly different from the data collected prior to nutrient management. Data were grouped into growing 

and nongrowing seasons after visual examination of time-series plots indicated visual differences between these 

periods. A null hypothesis of no difference between data collected prior to and during nutrient management was 

tested by means of a modified Wilcoxon-Mann-Whitney rank-sum test for seasonal data at the O.OS alpha level (R.M. 

Hirsch, U.S. Geological Survey, written commun., 1989; Crawford and others, 1983).

Because of the limited amount of measured data, Monte Carlo simulation was used to synthesize data collected 

prior to and during the nutrient-management phases in order to establish target goals and to perform the rank-sum 

test. The premanagement data were synthesized by randomly generating 1,000 data sets of each chemical constituent 

tested on the basis of the statistical characteristics of the measured data the number of seasons, the total number of 

observations in each season, and the mean and standard deviations for each season during the period prior to nutrient 

management. Data for the period during the management phase were synthesized by reducing the mean and the 

standard deviation of the data collected prior to nutrient management by a selected percentage. A second approach for 

generating the data for the management phase from normally-distributed data collected prior to nutrient management 

was to reduce the mean by a selected percentage without changing the standard deviation. The percentage by which 

the means of the synthesized data for the management phase were reduced was increased until the power of the test 

reached 1.0, which represented the greatest probability of rejecting the null hypothesis. Because the mean of the 

synthesized data for the management phase could only be lower than the mean of the data prior to nutrient 

management, the null hypothesis could only be rejected from one direction; thus, a one-tailed test was performed.

After the management phase was completed, the seasonal rank-sum test was used to determine if there was a 

change between the data collected prior to and during nutrient management. Because the mean of the data collected 

during the management phase could have either increased or decreased from the mean of the data collected prior to 

nutrient management, a two-tailed test was performed to determine if the target goals were achieved.

Seasonal Kendall Test

The seasonal Kendall test for trend (Hirsch and others, 1982) was used to analyze the Bald Eagle Creek base flow 

water-quality data. This nonparametric test for detecting monotonic trend was used because it is robust against 

seasonal behavior and departures from seasonably. In this test, Kendall's tau, ranging from -1.0 to +1.0, is a measure 

of monotonic association with 0.0 representing no association. Each tau value has an associated probability value (p), 

which is a measure of the confidence interval associated with that tau. For this study, a statistically significant or 

detectable change was defined as being within the 95-percent confidence interval (p<0.05). The estimate of slope 

trend was defined as the median slope for the period of record on the basis of the median values for all seasons.

Water-Resources Investigations Report 93-4069 18
EFFECTS OF SELECTED AGRICULTURE BEST-MANAGEMENT PRACTICES

ON HYDROLOGY AND SOILS

Hydrology

Changes in quantity and quality of precipitation, streamflow and soils are included in the following sections 

under hydrologic effects of nutrient management.

Precipitation 

Quantity

During the 4 years that precipitation was measured at the study area (1986-89 water years2), about 164 in. of 

precipitation were measured at the site (table 6); an additional 50.62 in. were measured at the New Park NOAA 

station during the fifth year (1990 water year). Precipitation was 2 percent below normal during the 5-year study, on 

the basis of long-term record at the nearby New Park NOAA station. Annual precipitation ranged from 37 percent 

below normal during the 1986 water year to 19 percent above normal during the 1989 water year. Precipitation was 

about 18 percent below normal prior to nutrient management and was about 4 percent above normal during the first 2 

years of nutrient management. Precipitation during the nongrowing season (October-March) ranged from 17 percent 

below normal in 1988 to 28 percent above normal in 1990. During the growing season (April-September), 

precipitation ranged from 57 percent below normal in 1986 to 37 percent above normal in 1989. The greater 

variations in precip-itation during the growing season probably resulted in greater variations in hydrologic processes 

such as runoff, recharge, evapotranspiration, and nutrient transport. Because precipitation was similar in the growing 

and nongrowing seasons during the 1987 and 1990 water years at New Park, data collected during these 2 years 

probably provide the best comparison of data collected prior to and during the management phase.

A large difference (11.74 in.) existed between the measured precipitation at Bald Eagle Creek and the NOAA 

station at New Park for the 1989 growing season. This difference was because of missing and bad records at Bald 

Eagle Creek during short-duration intense rain events measured on May 5,6, 16,23, July 4, and September 20, 1989. 

Therefore, the precipitation record from New Park was used for the 1989 growing season. The rainfall from these six 

events accounted for 42 percent of the total precipitation for the entire 6-month growing season.

Monthly precipitation at Bald Eagle Creek was variable and ranged from 0.27 in. in September 1986 to 12.84 in. 

in May 1989 (fig. 7). Precipitation was more than 2 in. less than normal each month except April during the 1986 

growing season. Precipitation was greater than normal during the 1987 water year because of the precipitation in 

November and December 1986 and September 1987, which was 3.29, 5.09, and 2.69 in. greater than normal, 

respectively (fig. 7). Prior to the wet September in 1987, the growing season was 29 percent drier than normal. 

Monthly precipitation during the 1988 water year ranged from 0.47 in. in June to 8.71 in. in May. During the 1989 

water year, monthly precipitation ranged from 0.98 in. in December to 12.84 in. in May. Data from the New Park 

NOAA station indicated that the 1990 water year was 15 percent wetter than normal, and monthly precipitation 

ranged between 1.44 in. in December 1989 to 6.61 in. in May 1990.

Antecedent soil moisture conditions could have had an effect on the quality of surface water at the beginning of 

the study. Historical data from the New Park station indicate that the study began following a year that was 4 percent 

drier than normal and the 4 years prior to the study were 8 percent wetter than normal.

The monthly comparison of the positive and negative deviations from the normal precipitation (fig. 8) suggests 

months during which corresponding fluxes in nutrients may begin in base flow. For example, figure 8 shows that 

above normal precipitation was measured in November during the first 4 years of the study. Assuming that the 

quantity of nitrate nitrogen available for transport from the soil to the stream remains constant, then precipitation 

would have a greater influence on the transport of the nitrate during November. Likewise, since precipitation was 

more than 4 in. above normal during December 1986 and May 1988 and 1989, similar fluxes in nitrate nitrogen 

concentrations and discharges could be expected during or shortly after these months. In contrast, precipitation was 

significantly below normal during the month of June in each water year. Thus, fluxes opposite of those for the month 

of November might be expected during or shortly after these months.

Water year is the period October 1 through September 30 and is designated by the calendar year in which it ends.

19 Water-Resources Investigations Report 93-4069
a

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Water-Resources Investigations Report 93-4069 20
MAMJJASONOJrMAMIJASONDJrMAMJJASDNDJrMAMJJASONDJrMAMJJAS 

1966 19B7 1986 1969 1990

Figure 7. Measured monthly precipitation at Bald Eagle Creek and normal monthly precipitation 

at New Park for the 1986-89 water years.

15

to

H

u

z

z

_J

DC. 

O

Z 5

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CD 19B6 

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OCT. NOV. DEC. JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT.

Figure 8. Monthly deviations of measured precipitation at Bald Eagle Creek from normal precipitation 

at New Park during the growing and nongrowing season for the 1986-90 water years.

21 Water-Resources Investigations Report 93-4069
Quality

Langland (1992) has shown that significant amounts of nitrogen contamination can be released to the 

atmosphere, carried great distances, and be deposited on the land surface by precipitation. For this reason, the quality 

of the precipitation deposited in the study area was determined prior to and during the management phase (table 7). 

Precipitation samples were collected prior to, during, and near the end of the growing season to investigate seasonal 

differences in precipitation quality. Most of the nitrogen in precipitation was in the form of ammonia and nitrate plus 

nitrite nitrogen. Concentrations of ammonia and nitrite plus nitrate in the precipitation were greater when less 

precipitation fell. These data suggest that the ammonia and nitrite plus nitrate may have been scavenged from the 

atmosphere during the early stages of precipitation events when volatilized ammonia and nitrite plus nitrate from 

manure was available and then diluted as the precipitation increased. Concentrations of ammonia in the precipitation 

were greatest near the end of the study when there was less precipitation and the number of cattle increased from 3 to 

12 in the pasture near the precipitation gage. The nitrogen load contributed to the Bald Eagle Creek from precipitation 

may have averaged 8 Ib/acre for the entire study, considering concentration data from table 7.

Generally, the data suggest that the contribution of nitrogen from precipitation at the Bald Eagle Creek site is 

seasonally variable, but it is not as significant as in other study areas within the Lower Susquehanna River Basin 

where animal densities are higher. For example, on May 20,1987,1.52 in. of precipitation were recorded at Bald 

Eagle Creek and concentrations of total nitrogen and total ammonia in precipitation were 0.80 and 0.25 mg/L, 

respectively. On the same day at Brush Run (site 1, fig. 1), where 57,000 chickens and 1,460 hogs are housed within 

0.10 mi2 of the sampling site, 0.74 in. of precipitation was recorded, and concentrations of total nitrogen and total 

ammonia in precipitation were 3.4 and 2.8 mg/L, respectively. On the basis of these limited concentration data, it was 

calculated that the total nitrogen deposited by precipitation on May 20, 1987, at Brush Run was 0.57 Ib/acre, more 

than twice the amount that was deposited at Bald Eagle Creek (0.28 Ib/acre) even though less than half the amount of 

precipitation fell at Brush Run. Because animal densities were lower at the Bald Eagle Creek site than at the Brush 

Run site, less nitrate and ammonia from animal waste was available for volatilization to the atmosphere and 

subsequent transport back to the land surface in precipitation.

Table 7. Water quality of precipitation in the Bald Eagle Creek Basin

[Precipitation, in inches; specific conductance in microsiemens per centimeter at 25 degrees Celsius; nitrogen and 

phosphorus in milligrams per liter; <, less than; , no data]

Constituent May 20. 1987 Septembers. 1987 March 25-26, 1988 May 1-2. 1989 August IS. 1989 May 5-6. 1990

Precipitation

Specific conductance

PH

Nitrogen, total

Organic, total

Ammonia, total

Nitrate plus nitrite, total

Phosphorus, total

1.52

30

4.3

.80

.25

.25

.30

.01

2.81

8

7.4

.30

.18

.02

.10

.30

1.25

14

4.6

.60

.28

.12

.20

.02

'0.90

--

--

.70

<.10

.30

.40

.01

0.20

45

-

2.3

.60

.70

1.0

.02

1 0.36

--

-

2.2

.10

I.I

1.0

.24

1 Precipitation data was estimated from data collected at New Park.

Water-Resources Investigations Report 93-4069 22
Streamflow

The following section gives information concerning the quantity and quality of base flow and stormflow. This 

information includes hydrograph separations and descriptive statistics concerning nutrient and sediment concentrations and discharges in surface water at Bald Eagle Creek.

Quantity

Daily streamflows recorded at the Bald Eagle Creek site during the study ranged from a minimum of 0.00 frVs 

(no flow) on several days in January and February 1986 to a maximum of 25 frVs estimated for May 17, 1988 (fig. 9). 

The yearly mean streamflows were 0.33, 0.32, 0.58, and 0.42 ft3/s for the 1986-89 water years, respectively. Total 

streamflow from the site was 20.44 in. prior to nutrient management; 10.47 and 9.97 in. were discharged during the 

1986-87 water years, respectively. Total streamflow was 31.14 in. during the first 2 years of the management phase; 

18.02 and 13.12 in. were discharged during the 1988-89 water years, respectively. About 31 percent of the 164 in. of 

measured precipitation was discharged as surface water during the first 4 years of the study; the remaining 69 percent 

was removed as evapotranspiration, flowed out of the site beneath the land surface, or remained in ground-water 

storage.

Daily streamflow data collected at the Bald Eagle.Creek site were correlated with data collected at Principio 

Creek (fig. I). The correlation coefficient (r) between log-transformed daily streamflows at the Bald Eagle Creek site 

and the Principio Creek station for the 2 years prior to nutrient management was 0.81 (considered good) with a 

standard error of 0.22, whereas, the correlation coefficient for streamflows during the nutrient-management phase 

was 0.62 (considered poor) with a standard error of 0.26. Streamflow, especially stormflow, was much more variable 

during the management phase of the study because of the increase in precipitation (fig. 9). This variability could 

account for the poor correlation between Principio Creek and Bald Eagle Creek data. At Principio Creek, streamflow 

was estimated to be about 35 percent below normal prior to nutrient management and 3 percent below normal during 

nutrient management. Thus, streamflow at Bald Eagle Creek was assumed to be about 35 percent below normal prior 

to nutrient management and 3 percent below normal during nutrient management.

Base flow. Hvdrograph separation techniques used to determine the contribution of base flow and stormflow to 

annual flow are described by Pettyjohn and Henning (1979). Sixty-six percent of the total streamflow during the study 

was base flow. Although nearly the same amount of base flow was discharged prior to and during the management 

phase, base flow comprised 84 percent (17.13 in.) of the total streamflow (20.44 in.) prior to nutrient management, 

but only 54 percent (16.70 in.) of the total streamflow (31.16 in.) during nutrient management (table 8). Base flow 

contributed 62 percent of the total streamflow during the nongrowing season and 68 percent of the total streamflow 

during the growing season. Eighty-one percent of the total streamflow during the nongrowing seasons prior to 

nutrient management was base flow, whereas only 45 percent of the total streamflow during the nongrowing seasons 

in the management phase was base flow. Base flow ranged between 58 and 98 percent of the monthly streamflow in 

September 1987 and June 1986, respectively, prior to nutrient management, and between 15 and 93 percent of the 

monthly streamflow in February 1988 and August 1989, respectively, during the management phase. The contribution of base flow to the total streamflow depended primarily on the duration, intensity, and amount of precipitation 

and antecedent soil moisture.

Stormflow. Stormflow contributed 34 percent of the total streamflow during the study and comprised about 

16 percent of total streamflow prior to the management phase and 46 percent of the total streamflow during the 

management phase. Nearly 11 in. more stormflow was discharged during nutrient management than prior to nutrient 

management (table 8). Thirty percent more of the total streamflow was stormflow during nutrient management than 

prior to nutrient management. Fifty-seven percent of the streamflow was stormflow in the 1988 water year but only 

15 percent was stormflow in the 1986 water year.

The hydrograph separations (fig. 9) of the continuous streamflow data show that most of the overland runoff 

(stormflow) during nutrient management was discharged in the growing seasons during the month of May; 3.9 in. 

was discharged in 1988 and 1.3 in. was discharged in 1989 (table 8). About 29 percent of the stormflow for the entire 

4 years was discharged during these 2 months of the nutrient-management phase. The sharp peaks of the stormflow 

indicate the rapid response shortly after precipitation began and the short stormflow durations, primarily caused by 

thin soils and steep slopes. The annual maximum instantaneous peak flows at Bald Eagle Creek for the 1986 through 

1989 water years were 6.9 ft /s on November 5, 1985,25 ft3/s from a slope/area indirect measurement on September 

18, 1987, 212 ft3/s from a slope/area indirect measurement on May 17, 1988, and 107 ft3/s on May 5, 1989.

23 Water-Resources Investigations Report 93-4069
S3HONI Nl 'NOIlVlldlOadd A1IVQ S3HONI Nl 'NOIlVlldlOadd A1IVQ

QNO03S M3d 133d 31803 NI 

'39aVH3Sia NV3W

QNO03S U3d 133d OIBfD NI 

'39aVH3SIQ NV3W A1IVQ

Water-Resources Investigations Report 93-4069 24
Table 8. Contribution of base flow to total streamflow at Bald Eagle Creek during the 1986-89 water years

Month Year Base flow 

(inches)

Stormflow 

(inches)

Total 

streamflow 

(inches)

Percentage of 

base flow 

in total 

streamflow

NONGROWING SEASON

October

November

December

January

February

March

1985

1986

1987

1988

1985

1986

1987

1988

1985

1986

1987

1988

1986

1987

1988

1989

1986

1987

1988

1989

1986

1987

1988

1989

0.52

.33

.62

.28

.72

.50

.63

.30

.82

.73

.48

.27

.55

.82

.39

.38

.90

.77

.52

.34

1.2

1.0

.52

.61

0.07

.06

.13

.10

.21

.16

.57

.37

.06

.37

.08

.06

.30

.10

.91

.30

.30

.05

2.9

.22

.20

.20

.68

.21

0.59

.39

.75

.38

.93

.66

1.2

.67

.88

I.I

.56

.33

.85

.92

1.3

.68

1.2

.82

3.4

.56

1.4

1.2

1.2

.82

88

85

83

74

77

76

52

45

93

66

86

82

65

89

30

56

75

94

IS

61

86

83

43

74

GROWING SEASON

April

May

June

July

August

1986

1987

1988

1989

1986

1987

1988

1989

1986

1987

1988

1989

1986

1987

1988

1989

1986

1987

1988

1989

1.2

1.0

.49

.60

1.0

.90

1.9

1.4

.78

.63

.89

1.2

.61

.62

.64

1.2

.35

.36

.45

1.3

.20

.10

.18

.18

.10

.07

3.9

1.3

.02

.04

.11

.20

.03

.09

.35

1.0

.06

.07

.30

.10

1.4

1.1

.67

.78

I.I

.97

5.8

2.7

.80

.67

1.0

1.4

.64

.71

.99

2.2

.41

.43

.75

1.4

86

91

73

77

91

93

33

52

98

94

89

86

95

87

65

55

85

84

60

93

25 Water-Resources Investigations Report 93-4069
Table 8. Contribution of base flow to total streamflow at Bald Eagle Creek during the 1986-89 water 

years-Continued

Month Year Base flow 

(inches)

Stormflow 

(inches)

Total 

streamflow 

(inches)

Percentage of 

base flow 

in total 

streamflow

GROWING SEASON-Continued

September 1986

1987

1988

1989

Subtotals

Water year

1986

1987

1988

1989

Growing season

Prior to management

During management

Subtotal

Nongrowing season

Prior to management

During management

Subtotal

Totals

Prior to management

During management

Entire study

0.24

.58

.29

1.0

8.89

8.24

7.82

8.88

8.27

11.36

19.63

8.86

5.34

14.20

17.13

16.70

33.83

0.03

.42

.11

.20

1.58

1.73

10.20

4.24

1.23

7.93

9.16

2.08

6.53

8.61

3.31

14.46

17.77

0.27

1.0

.40

1.2

10.47

9.97

18.02

13.12

9.50

19.29

28.79

10.94

11.87

22.81

20.44

31.16

51.60

89

58

73

83

85

83

43

68

87

59

68

81

45

62

84

54

66

Water-Resources Investigations Report 93-4069 26
Quality

Base flow. Descriptive statistics (table 9) of streamflow and the concentrations and discharges of seven 

nitrogen and three phosphorus constituents and suspended sediment were calculated to provide a seasonal 

characterization of the base-flow quality of the Bald Eagle Creek. Statistics were calculated to investigate differences 

in data collected prior to and during nutrient management, during different seasons and water years. Concentrations 

and discharges listed in table 9 are from analyses of manually collected depth-integrated discrete samples. Median 

instantaneous streamflows measured during sample collection increased during nutient management as a result of the 

significant increase in precipitation. Concentrations and discharges of total nitrogen and total and dissolved nitrite 

plus nitrate increased during nutrient management in both the growing and nongrowing seasons. No significant 

changes were detected in concentrations or discharges through time or season for total and dissolved ammonia, 

ammonia plus organic nitrogen, phosphorus, and suspended sediment. Detailed discussion of each constituent is 

included later in the report.

Estimated monthly and annual nutrient and sediment loads in base flow prior to and during nutrient management, 

were calculated by use of the 7-parameter log-linear model (eqs. 1 and 2) (table 10). During nutrient management, 

estimated monthly and annual loads for total nitrogen, dissolved nitrite plus nitrate, dissolved phosphorus, and 

orthophosphorus increased; monthly and annual loads of total phosphorus and suspended sediment decreased. Loads 

for every constituent were greater in the growing season than the nongrowing season, especially during the 1989 

growing season (table 10) when precipitation was 9.03 in. above normal. Generally, higher loads of nitrogen were 

measured during the months of March, April, May, and June when applications of manure and commercial fertilizers 

are greatest (fig. 10). Phosphorus loads were more variable than nitrogen loads, but were usually greater in March, 

April, and May than in other months (fig. 11). The percentage of dissolved nitrite plus nitrate to total nitrogen showed 

only slight variations during the study. For the growing and nongrowing seasons, the percentage was 85 and 

82 percent, respectively, during the dry 1986 water year, and 86 percent during both seasons during the wet 1989 

water year. This indicates that the dissolved nitrite plus nitrate available for transport was sufficient to maintain the 

levels observed despite seasonal and annual changes in application rates. The percentage of dissolved phosphorus to 

total phosphorus was highly variable, increasing from 55 percent prior to nutrient management to 87 percent during 

nutrient management, varied by water year (53 percent in 1987 and 92 percent in 1989), and varied by season 

(72 percent growing to 62 percent nongrowing). This suggests the phosphorus load is influenced more by variations 

in precipitation and application rates than is the nitrogen load.

Table 11 lists the parameter values used to calculate base-flow nitrogen and phosphorus concentrations and 

discharges by use of the 7-parameter log-linear model described earlier. The reported T values are a measure of the 

significance of the parameter in the model described earlier in equation 1. A T value with an absolute value greater 

than 2 was considered to be significant. During the nutrient-management period when precipitation increased, the 

coefficients that account for seasonably (P5 and P6) became insignificant. Because of a longer sampling period, the 

time parameter (P3) became more significant for calculating the concentrations and loads for many of the constituents 

during nutrient management.

The load-estimator model explained 17 to 78 percent of the variability observed in the logarithms of the 

constituent concentrations in base flow prior to nutrient management and 10 to 52 percent during nutrient 

management. Likewise, the model explained 40 to 99 percent of the variability observed in the logarithms of the 

constituent loads in base flow prior to nutrient management and 30 to 99 percent during nutrient management. Lastly, 

the model added uniformity among other USGS projects for the Chesapeake Bay Program which also are using the 

model to calculate loads.

An increasing trend (positive tau and p<.05) was detected during the 5 years of base-flow data for concentrations 

and discharges of total and dissolved nitrite plus nitrate (table 12). By use of the Seasonal Kendall test, significant 

trends were not detected in either concentrations of ammonia, ammonia plus organic nitrogen, phosphorus, or 

suspended sediment in base flow or discharges of phosphorus and suspended sediment. Longer sampling times may 

be needed in order to see these trends become significant. The seasonal Kendall test was not used on ammonia and 

ammonia plus organic nitrogen discharges after inspection of the means showed no difference.

27 Water-Resources Investigations Report 93-4069
Concentrations and discharges of total nitrogen and dissolved nitrite plus nitrate in base flow (figs. 12 and 15) 

varied seasonally. As precipitation increased and cattle were permitted in the pasture near the gage during nutrient 

management, the annual ranges and maximum concentrations and discharges of total nitrogen and dissolved nitrite 

plus nitrate increased. This suggests that there was an increase in total nitrogen in base flow and part of it may have 

been contributed by grazing animals that deposited organic and ammonia nitrogen that mineralized to nitrite plus 

nitrate in and near the stream.

Median concentrations of total nitrogen and dissolved nitrite plus nitrate in base flow increased significantly 

from 4.7 and 4.0 mg/L, respectively, in the 1986 water year to 6.3 and 5.4 mg/L, respectively, in the 1990 water year. 

This significant increase is shown by the Seasonal Kendall trend lines in figure 12. Maximum concentrations of total 

nitrogen and dissolved nitrite plus nitrate in base flow were usually measured in February after applications of 

manure, and prolonged periods of precipitation. Minimum concentrations were measured in June and July when 

nitrogen uptake for crop growth, especially corn, was at a maximum, evapotranspiration rates were high, and 

precipitation was often below normal.

The median concentrations of total nitrogen and dissolved nitrite plus nitrate in base flow increased from 4.9 and 

4.1 mg/L, respectively, prior to nutrient management, to 5.8 and 5.0 mg/L, respectively, during nutrient management 

(fig. 13). The maximum concentrations of total nitrogen and dissolved nitrite plus nitrate increased from 6.2 and 

5.3 mg/L, respectively, prior to nutrient management, to 7.7 mg/L and 6.4 mg/L, respectively, during nutrient 

management. Concentrations of dissolved nitrite plus nitrate and total nitrogen also were measured in two tributaries 

(fig. 2, table 13) that drain into Bald Eagle Creek. Nitrogen concentrations were higher in tributary 1 than tributary 2 

and the gage site, suggesting that base-flow discharges originating from different ground water sources in the basin 

mixed and were diluted before reaching the gage site, where concentrations of total nitrite plus nitrate and total 

nitrogen in base flow averaged 4.9 and 5.5 mg/L, respectively, during the 5-year study. These significant increases in 

concentrations of total nitrogen and dissolved nitrite plus nitrate during nutrient management were probably because 

of a combination of the following factors: (1) an increase in precipitation, (2) the associated increase in leaching of 

nitrate through the soils, (3) the reduction in nitrogen uptake by corn caused by the reduction in corn acreage, (4) an 

increase in nitrogen in the soil caused by an increase in nitrogen-fixing alfalfa, and (5) an increase in animal waste 

near the gage.

Discharges of total nitrogen and dissolved nitrite plus nitrate (fig. 14) in base flow varied seasonally as did the 

concentrations of total nitrogen and dissolved nitrite plus nitrate. The discharges of total nitrogen and dissolved nitrite 

plus nitrate were closely related to base flow. Total nitrogen and dissolved nitrite plus nitrate discharges decreased 

during the growing season as nitrogen requirements by corn increased, base flow and precipitation decreased, and 

evapotranspiration increased. About 4,420 Ib (83 percent) of the 5,300 Ib of total nitrogen in base flow was dissolved 

nitrite plus nitrate prior to nutrient management (table 10). Approximately 4,930 Ib (86 percent) of the 5,700 Ib of 

total nitrogen discharged was dissolved nitrate plus nitrite in base flow during nutrient management when 34 percent 

less cropland was devoted to corn. At the Nutrient-Management Subbasin in the Little Conestoga River watershed 

(site 3, fig. 1), 88 percent of the total nitrogen was dissolved nitrite plus nitrate prior to nutrient management and 

91 percent of the total nitrogen was dissolved nitrite plus nitrate during nutrient management. Thus, the proportion of 

total nitrogen as dissolved nitrite plus nitrate increased during nutrient management in both basins.

Concentrations of total and dissolved organic nitrogen and total and dissolved ammonia nitrogen in base flow 

were considerably smaller and exhibited less seasonality than concentrations of nitrite plus nitrate (figs. 15 and 16). 

This suggests that transport and possibly the sources of organic nitrogen and ammonia nitrogen were probably 

different than the transport and sources of nitrite plus nitrate nitrogen. Although concentrations of ammonia and 

organic nitrogen were not significantly different (table 12) prior to and during nutrient management, median 

concentrations of total and dissolved organic nitrogen in base flow were lower during nutrient management than prior 

to nutrient management (fig. 17). The median concentration of total organic nitrogen decreased from 0.62 to 

0.50 mg/L and the median concentration of dissolved organic nitrogen decreased from 0.58 to 0.41 mg/L (fig. 17). 

One possible explanation for the decrease in median concentrations in organic nitrogen is that manure applications, a 

major source of organic nitrogen, were reduced by 40 percent (tables 4 and 5). Maximum concentrations of total and 

dissolved ammonia prior to nutrient management (0.23 mg/L) and during nutrient management (0.54 and 0.50 mg/L) 

were measured on December 12,1986, and February 12,1990, respectively, during the nongrowing season.

Water-Resources Investigations Report 93-4069 28
Discharges of total and dissolved ammonia plus organic nitrogen and total and dissolved ammonia were not 

statistically significant. About 87 percent of the organic nitrogen and 84 percent of the ammonia in base flow was 

dissolved prior to nutrient management and 80 percent of the organic nitrogen and 92 percent of the ammonia was 

dissolved during nutrient management.

Concentrations of total and dissolved phosphorus in base flow did not exhibit seasonal trends (fig. 18) nor did the 

concentrations correlate with base flow (r = 0.16). Concentrations of total and dissolved phosphorus in base flow 

ranged from 0.02 to 0.18 mg/L and from 0.02 to 0.17 mg/L, respectively (table 9). Concentrations of dissolved 

orthophosphorus ranged from 0.01 to 0.16 mg/L and were greatest during the 1989 water year (table 9), the year with 

the most precipitation (52.32 in.) (table 6) measured during the study.

About 70.4 Ib of total phosphorus and 38.5 Ib of dissolved phosphorus were discharged in base flow during the 

2 years prior to nutrient management; 46.6 Ib of total phosphorus and 40.7 Ib of dissolved phosphorus were 

discharged in the first 2 years of nutrient management (table 10). Discharge of dissolved orthophosphorus increased 

from 26.7 Ib prior to nutrient management to 31.3 Ib during the first 2 years of nutrient management. About 

68 percent of the total phosphorus discharged in base flow during the 5-year study was dissolved phosphorus, and 

50 percent was dissolved orthophosphorus. The maximum discharges of total phosphorus [0.466 Ib/d (pounds per 

day)], dissolved phosphorus (0.441 Ib/d), and orthophosphorus (0.415 lb/d) in base flow were measured during the 

growing season on July 24, 1989 (fig. 19, table 9).

Although the fanners reduced phosphorus applications 61 percent (table 5), no significant change was detected 

in concentrations or loads of phosphorus in base flow during the 3 years of nutrient management. The phosphorus 

yield from Bald Eagle Creek Basin in base flow for the 1986-89 water years was 0.42 Ib/acre. The estimated loads for 

total phosphorus are from the log-linear regression model discussed earlier; data for the statistical test for trend 

(Seasonal Kendall test) is the base flow concentration data collected monthly.

Concentrations of suspended sediment in base flow were consistently greater after plowing and when cattle were 

turned out to pasture (April through June) in the growing season than in the nongrowing season. Median 

concentrations were 6.0 mg/L during the pre-nutrient management growing season and were 3.0 mg/L during the 

post-nutrient management nongrowing season (fig. 20, table 9). But concentrations of suspended sediment at Bald 

Eagle Creek were lower than concentrations measured in other intensively fanned basins in Pennsylvania. For 

example, Koerkle and others (U.S. Geological Survey, written commun., 1992) reported that, at the 1.42-mi2 

Nutrient-Management Subbasin in the Little Conestoga Creek headwaters (site 3, fig. 1), concentrations of suspended 

sediment in base flow ranged from 3 to 136 mg/L from April 1984 through September 1989; the median 

concentration was 17 mg/L. The low concentrations of suspended sediment in base flow at Bald Eagle Creek 

probably occur for several reasons: (1) fewer animals have direct access to the stream, (2) cover crops are used on 

steep slopes during the nongrowing season, (3) minimum or no-till plowing is utilized, and (4) there is a forested 

buffer strip along the stream in the downstream area of the basin.

Maximum concentrations of suspended sediment in base flow at Bald Eagle Creek were measured in May and 

July 1987, possibly in response to modifications made by the property owner to the stream channel immediately 

upstream from the gage, and in October 1989, May and June 1990 in response to animals pasturing upstream from the 

gage. However, no trend was detected in concentrations of suspended sediment during the 5-year study.

A total of about 4,550 Ib of suspended sediment was discharged in base flow prior to nutrient management, and 

about 2,820 Ib were discharged in base flow during the first 2 years of the management period (table 10). This 

decrease in sediment transport coincided with the rotation of 34 percent of the cropland from corn to alfalfa during 

nutrient management. Thus, less soil was exposed from plowing and planting and, therefore, available for erosion and 

transport to the stream.

29 Water-Resources Investigations Report 93-4069
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Water-Resources Investigations Report 93-4069 30
Table 9. Water-quality characteristics of base flow at Bald Eagle Creek by growing and nongrowing season and by water year-Continued

Constituent 

characteristic

Nitrogen, total N

Concentration

Discharge

Phosphorus,

total as P

Concentration

Discharge

Phosphorus,

dissolved as P

Concentration

Discharge

w Ortho-phosphorus,

dissolved as P

Concentration

Discharge

Sediment, suspended

Concentration

^ Discharge

0>

Pre-nutrient 

management

Max

6.2

15.9

.11.181

.09

.141

.08.125

1316.0

Min

4.0

2.59

.03

.021

.02.011

.01

.010

1.01.08

Med n

4.9 22

8.48 22

.05 21

.084 21.04 22.053 22

.02 21.032 21

4.0 22

7.96 22

Post-nutrient 

management

Max

7.7

30.8

.18.466

.17

.441

.16

.415

2675.8

Min

4.7

3.02

.02.021

.02.017.01.009

1

.864

Med

5.8

12.4

.05.064

.04.058.03

.043

3

5.59

n

3636

36

36

363636

36

3434

Pre-nutrient 

management 

growing season

Max

5.4

10.8

.10.181.07.102.03.068

9.0

16.0

Min

4.0

2.59

.04.038

.02.011.01.010

2.0

1.08

Med

4.5

6.56

.06

.080

.04.053.02.029

6.0

8.58

n

12121111

1212

11

111212

Post-nutrient management 

growing season

Max

7.3

19.4

.18.466.17.441

.16.415

21

44.2

Min Med

4.7 5.8

3.02 13.5

.02 .05.034 .095.02 .04.017 .086.01 .03.008 .044

1 3.5

.864 8.91

n

19191919

19

19

19191818

Pre-nutrient 

management 

nongrowing season

Max Min

6.2 4.9

15.9 3.44

.11 .03.172 .021

.09 .02.141 .021

.08 .01.125 .021

13 1.015.2 1.46

Med

5.3

9.29

.05.105

.03

.062.03.058

4.0

7.%

n

10

10

10

10

10

10

1010

1010

Post-nutrient management 

nongrowing season

Max Min

7.7 5.0

30.8 3.40

.10 .02

.416 .021.08 .02.297 .021

.08 .02

.297 .016

26 2

75.8 1.40

Med n

5.8 176.95 17

.05 17.060 17.04 17

.045 17

.03 17.039 17

3 163.73 16

9

9ICO
Table 9. Water-quality characteristics of base flow at Bald Eagle Creek by growing and nongrowing season and by water year-Continued

i

_ Constituent 

a characteristic

5- Instantaneous streamflow

§ (tf/s)

3D

 g Nitrate + nitrite.

a. dissolved as N

J§ Concentration^ Discharge

*° Nitrate* nitrite.

total as N

Concentration

Discharge

Ammonia,

dissolved as N

K> Concentration

Discharge

Ammonia,

total as N

ConcentrationDischarge

Ammonia + organic.

dissolved as N

ConcentrationDischarge

Ammonia + organic.

total as N

Concentration 

Discharge

1986 Water Year

Max

0.50

4.9

12.1

5.1

12.7

.08

.189

.08

.189

.80

2.16

1.2 

3.24

Min

0.10

3.62.21

3.7221

.01.009

.01

.009

.30

275

.30

.275

Med

0.30

4.07.07

4.1

7.18

.04.056

.05

.081

.60

.980

.70 

1.13

n

10

1010

1010

1010

10

10

10

10

10 

10

1987 Water Year

Max

0.42

5.3

10.6

5.3

10.6

.04.086

.05

.086

.90

1.60

1.0 

1.60

Min

0.13

3.4

2.88

3.8

2.95

.01

.007

.01

.007

.20

.292

.40 

.583

Med

029

4.2

6.72

42

7.03

.03.049

.04

.060

.65

.832

.70 

1.08

n

12

12

12

12

12

12

12

12

12

12

12

12 12

1988 Water Year

Max

1.1

5.0

27.9

5.5

27.9

.09

.416

.09

" .534

.70

2.38

.80 

2.97

Min

0.10

4.4

2.70

4.42.70

.01.010

.01

.010

.27

.308

.30 

.308

Med

023

4.7

5.89

4.7

5.89

.02

.024

.03

.026

.40

.451

.55 

.562

n

12

1212

1212

12

12

12

12

12

12

12 

12

1989 Water Year

Max

0.57

5.7

17.5

5.7

17.5

20

.616

.24

.616

.70

2.15

.80 

2.46

Min

0.10

4.13.08

4.9

3.08

.01

.007

.02

.013

.50

211

.40 .324

Med

0.34

5.19.36

5.49.36

.05

.077

.05

.078

.30.918

.50 

.918

n

13

13

13

13

13

1313

13

13

1313

13 

13

1990 Water Year

Max

0.69

6.4

20.1

6.6

22.4

.50

1.48

.54

1.60

1.50

2.67

1.50

327

Min

0.31

42

8.39

4.5

9.71

.01.019

.01

.019

20.454

.04 .864

Med

0.41

5.4

12.3

5.7

12.4

.04

.117

.04.117

.40

.950

.60 

1.26

n

11

11

11

11

11

11

11

1111

11

11

11 11
Table 9. Water-quality characteristics of base flow at Bald Eagle Creek by growing and nongrowing season and by water year-Continued

ffi 

33

Constituent 

characteristic

Nitrogen, total N

Concentration

Discharge

Phosphorus,

total as P

Concentration

Discharge

Phosphorus,

dissolved as P

Concentration

Discharge

Orthophosphorus,

dissolved as P

Concentration

Discharge

Sediment, suspended

Concentration

Discharge

1986 Water Year 

Max Min Med

5.9

15.9

.09

.181

.06

.108

.06.100

6.0

15.2

4.0

2.59

.03

.038

.02

.011

.02.025

1.0

1.08

4.7

8.48

.06.127

.04

.053

.03.038

4.0

6.86

n

1010

99

10

10

9

9

10

10

1987 Water Year 

Max Min Med

6.2

12.0

.11

.172

.09

.141

.08.125

13

16.0

4.3

3.44

.03

.021

.02

.020

.01.010

2.0

2.05

5.0

8.28

.05

.081

.04

.060

.02

.031

6.0

9.10

n

1212

1212

12

12

12

12

12

12

1988 Water Year 

Max Min Med

5.9

30.9

.08

.416.08

.297

.08

.297

13.0

17.8

4.7

3.02

.02.034

.02

.017

.01.009

1.0

.864

5.3

6.58

.04

.050

.03

.044

.02

.031

2.0

3.02

n

1212

1212

12

12

1212

11

11

1989 Water Year 

Max Min Med n

6.4

19.1

.18

.466

.17

.441

.16.415

7.0

15.4

5.63.40

.03

.021.03

.021

.02

.016

1.0

1.4

6.0

10.6

.05

.078

.04

.060

.04.060

3.54.8

1313

1313

13

1313

13

12

12

1990 Water Year 

Max Min Med

7.7

24.2

.10

.297

.08

.233

.08.233

26.0

75.8

5.6

12.2

.02

.039

.02

.039

.02

.039

2.0

3.99

6.3

13.8

.05

.105

.04

.089

.02.047

3.0

10.3

n

ItIt

II11

II11

11

11II

11

I

s
Table 10. Nitrogen, phosphorus, and suspended-sediment loads in base flow at Bald Eagle Creek prior to (October 

1985 - September 1987) and during (October 1987-September 1989) nutrient management 

[Base flow, in inches; loads, in pounds]

Month Year

Base 

flow

Dissolved 

nitrate 

plus 

nitrite

Total 

nitrogen

Total 

phosphorus

Loads

Dissolved 

phosphorus

Dissolved 

orthophosphorus

Suspended 

sediment

NONGROWING SEASON

October

November

December

January

February

March

Subtotal

1985

1986

1987

1988

1985

1986

1987

1988

1985

1986

1987

1988

1986

1987

1988

1989

1986

1987

1988

1989

1986

1987

1988

1989

0.52

.33

.62

.28

.72

.50

.63

.30

.82

.73

.48

.27

.55

.82

.39

.38

.90

.77

.52

.34

1.2

1.0

.52

.61

120

80

92

88

170

130

140

91

210

180

190

92

170

230

120

130

220

230

120

110

330

300

160

190

3,893

160

97

110

98

220

150

160

100

270

220

220

100

210

270

130

140

270

270

140

120

380

350

170

200

4,555

1.6

1.7

.9

.8

2.8

2.8

1.3

.9

3.2

3.6

1.7

1.0

1.2

3.7

1.2

1.3

2.5

3.0

1.3

1.3

4.5

4.3

1.6

_2Ji

50.2

1.3

.6

.7

.8

1.8

I.I

1.0

.8

2.0

1.5

I.I

1.4

.9

1.6

.9

1.2

1.4

1.5

.9

1.0

2.4

2.2

I.I

_LI

30.0

0.9

.5

.4

.6

1.4

.9

.8

.8

1.7

1.3

1.2

.8

.9

1.4

.7

1.2

1.4

1.2

.7

I.I

2.2

1.5

.9

_LI

26.2

NO

34

64

41

130

55

94

4

130

74

110

38

59

92

60

60

130

MO

67

59

280

220

98

_L20_

2,239

Water-Resources Investigations Report 93-4069 34
Table 10. Nitrogen, phosphorus, and suspended-sediment loads in base flow at Bald Eagle Creek prior to (October 

1985 - September 1987) and during (October 1987-September 1989) nutrient management-Continued

Month Year

Base 

flow

Dissolved 

nitrate 

plus 

nitrite

Total 

nitrogen

Total 

phosphorus

Loads

Dissolved 

phosphorus

Dissolved Suspended 

orthophosphorus sediment

GROWING SEASON

April 1986

1987

1988

1989

May 1986

1987

1988

1989

June 1986

1987

1988

1989

July 1986

1987

1988

1989

August 1986

1987

1988

1989

September 1986

1987

1988

1989 

Subtotal

1.2

1.0

.49

.60

1.0

.90

1.9

1.4

.78

.63

.89

1.2

.61

.62

.64

1.2

.35

.36

.45

1.3

.24

.58

.29

1.0

320

280

140

200

260

230

540

430

180

150

260

380

140

140

180

350

79

83

120

400

58

130

89

320

5,459

370

320

150

220

310

270

650

500

220

180

300

450

170

170

200

420

95

100

140

490

69

160

100

390

6,444

5.4

4.2

1.4

2.2

4.6

3.5

3.7

4.3

3.4

2.1

2.1

3.9

2.8

2.6

1.4

3.4

1.5

1.3

1.0

3.9

I.I

3.0

.8

3.2

66.8

2.8

2.3

1.0

1.7

2.5

2.2

3.1

3.7

1.9

1.5

1.9

3.4

1.4

1.7

1.3

3.3

.6

.8

1.0

3.8

.4

2.1

.8

3.1

48.1

2.2

1.4

.7

1.6

1.7

I.I

I.I

2.5

1.2

.6

I.I

2.5

.9

.6

.9

2.5

.5

.3

.7

3.1

.3

.6

.6

3.1

31.8

420

320

95

130

460

370

130

220

360

270

150

250

240

290

120

260

72

99

82

280

26

200

49

240

5,133

Prior to nutrient management

1986

1987

Subtotal

8.89

8.24

17.13

2,257

2,163

4,420

2,744

2,557

5,301

34.6

35.8

70.4

19.4

19.1

38.5

15.3

11.4

26.7

2,417

2.134

4.551

During nutrient management

1988

1989

Subtotal

Grand total

7.82

8.88

16.70

33.83

2,151

2,781

4,932

9,352

2,470

3,228

5,698

10,999

18.4

28.2

46.6

117.0

14.8

25.9

40.7

79.2

9.8

21.5

31.3

58.0

1,119

1,702

2,821

7,372

35 Water-Resources Investigations Report 93-4069
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Figure 10. Relation between monthly nitrogen discharges in base flow (top) and monthly nitrogen 

applications (bottom).

Water-Resources Investigations Report 93-4069 36
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Figure 11. Relation between monthly phosphorus discharges in base flow (top) and monthly 

phosphorus applications (bottom).

37 Water-Resources Investigations Report 93-4069
Table 11. Coefficients, standard deviations, and T values for the 7-parameter log-linear model used to estimate 

concentrations and loads in base flow

[Prc, prior to nutrient management; Post, during nutrient management; p0, constant; Pj, log of streamflow; p2, log of streamflow 

squared; Pj, decimal time; p4, decimal time squared; p5, sin (time); p$, cos (time)]

Constituent Parameter Coefficient

Dissolved nitrite plus nitrate

Concentration

Load

Total nitrogen

Concentration

Total nitrogen

Load

Dissolved phosphorus

Concentration

Load

PoPl P2 P3 P4

Ps

P6

Po

Pl

P2

P3

P4

Ps

P6

Po

Pl

P2

P3

P4

Ps

P6

Po

Pl

P2

P3

P4

Ps

P6

Po

Pl

P2

P3

P4

Ps

P6

Po

P.

P2

P3

P4

Ps

P6

Pre

1.4270

- .0990

.0213

.0178

.0085

.I486

.1152

.7434

.9003

.0213

.0178

.0085

.I486

.1152

1.6078

-.0905

- .0391

-.0135

.0805

.1172

.1127

.9308

.9095

- .0391

-.0135

.0805

.1172

.1127

-3.6066

.8233

-.0102

.0971

.1070

- .4056

-.1146

-4.2836

1.8233

-.0102

.0971

.1070

- .4054

-.1140

Post

1.6038

-.0409

.0404

.0569

-.0605

.0343

.0311

1.0450

.9591

.0404

.0569

- .0605

.0343

.0311

1.6951

.0063

.1064

.0695

.0021

.0150

.0308

1.1363

1.0063

.1064

.0695

.0021

.0150

.0308

-3.5832

-.2193

.0844

.5650

.3596

.0309

.1036

-4.1420

.7807

.0844

.5650

.3596

.0309

.1036

Standard deviation

Pre

0.0273

.0616

.5940

.0252

.0487

.0433

.0196

.0273

.0616

.0594

.0252

.0487

.0433

.0196

.0206

.0607

.0588

.0249

.0456

.0415

.0193

.0260

.0607

.0588

.0249

.0456

.0415

.0193

.1962

.4580

.4437

.1874

.3442

.3133

.1459

.1962

.4580

.4437

.1874

.3442

.3133

.1459

Post

0.0551

.0602

.0832

.0316

.0991

.0314

.0351

.0551

.0602

.0832

.0316

.0991

.0314

.0351

.0455

.0497

.0688

.0261

.0891

.0259

.0290

.0455

.0497

.0688

.0261

.0819

.0259

.0290

.4859

.5308

.7341

.2788

.8746

.2768

.3092

.4859

.5308

.7341

.2788

.8746

.2768

.3092

T value

Pre

52.26

-1.62

.36

.70

.17

3.43

5.87

27.22

14.62

.36

.70

.17

3.43

5.87

61.78

-1.49

-.67

-.54

1.76

2.82

5.83

35.77

14.97

-.67

-.54

1.76

2.82

5.83

-18.38

1.80

-.02

.52

.31

-1.29

-.79

-21.83

3.98

-.02

.52

.31

-1.29

-.79

Post

29.12

-.68

.48

1.80

-.61

1.09

.89

18.97

15.94

.48

1.80

-.61

1.09

.89

37.25

.13

1.55

2.66

.03

.58

1.06

24.97

20.24

1.55

2.66

.03

.58

1.06

-7.37

- .41

.11

2.03

.41

.11

.34

-8.52

1.47

.11

2.03

.41

.11

.34

Water-Resources Investigations Report 93-4069 38
Table 11. Coefficients, standard deviations, and T values for the 7-parameter log-linear model used to estimate 

concentrations and loads in base flow-Continued

Constituent Parameter Coefficient

Dissolved orthophosphorus

Concentration

Load

Total phosphorus

Concentration

Total phosphorus

Load

Suspended sediment

Concentration

Load

PoPiP2

Pa

P4

Ps

P6

Po

Pi

P2

Pa

P4

Ps

P6

PoPi

P2

Pa

P4

Ps

P&

Po

p.P2

Pa

P4

Ps

P6

Po

Pi

P2

Pa

P4

Ps

P6

Po

Pi

P2

Pa

P4

Ps

PA

Pre

-3.8487

.4268

.1407

-.2139

- .2405

-.2139

.1352

-4.4681

1.4269

.1407

-.2139

- .2405

-.2139

.1352

-3.0864

.9275

.5532

.2051

- .5562

- .6739

.0319

-3.7634

1.9275

.5532

.2051

- .5562

- .6739

.0319

.9318

.9607

-.1535

-.0251

.3330

-.1862

-.7128

.2589

1.9607

-.1535

-.0251

.3330

-.1862

-.7128

Post

-3.5832

-.2193

.0844

.5650

.3596

.0309

.1036

-4.1420

.7807

.0844

.5650

.3596

.0309

.1036

-3.3868

- .3756

.3885

.I960

.6828

.2227

-.1350

-3.9457

.6244

.3885

.I960

.6828

.2227

-.1350

.7738

-.1813

- .061 1

.1371

.6227

.1103

-.1687

.2198

.8187

- .061 1

.1371

.6227

.1103

-.1687

Standard deviation

Pre

0.2484

.6505

.6451

.2514

.4724

.4198

.1951

.2484

.6505

.6451

.2514

.4724

.4198

.1951

.3542

.8267

.8009

.3383

.6213

.5655

.2633

.3542

.8267

.8009

.3383

.6213

.5655

.2633

.2192

.5034

.4846

.1952

.3566

.3564

.1607

.2192

.5034

.4846

.1952

.3566

.3564

.1607

Post

0.4859

.5308

.7341

.2788

.8746

.2768

.3092

.4859

.5308

.7341

.2788

.8746

.2768

.3092

.3437

.3755

.5193

.1972

.6187

.1958

.2188

.3437

.3755

.5193

.1972

.6187

.1958

.2188

.4534

.4825

.6720

.2574

.7977

.2491

.2806

.4534

.4825

.6720

.2574

.7977

.2491

.2806

Pre

-15.50

.66

.22

-.85

-.51

-.51

.69

-17.99

2.19

.22

-.85

-.51

-.51

.69

-8.71

1.12

.69

.61

-.90

-.19

-.12

-10.63

2.33

.69

.61

- .90

-1.19

- .12

4.25

1.91

-.32

-.13

.93

-.52

-4.44

1.18

3.89

-.32

-.13

.93

-.52

-4.44

T value

Post

-7.37

- .41

.11

2.03

.41

.11

.34

-8.52

1.47

.11

2.03

.41

.11

.34

-9.85

-1.00

.75

.99

1.10

1.14

-.62

-11.48

1.66

.75

.99

1.10

1.14

- .62

1.71

- .38

- .09

.53

.78

.44

- .60

.48

1.70

-.09

.53

.78

.44

-.60

39 Water-Resources Investigations Report 93-4069
Table 12. Seasonal Kendall test results for nitrogen (as N) and phosphorus (as P) constituents in base flow for the 

1986-90 water years

[(p), probability value; (mg/L)/yr, milligrams per liter per year; (Ib/yr), pounds per year; concentration, milligrams per liter; 

discharge, pounds per day; cfs, cubic feet per second; +, significant increasing trend; 0, no trend]

Constituent

Discharge

Total nitrogen

Concentration

Discharge

Nitrite plus nitrate

Concentration

Total

Dissolved

Discharge

Total

Dissolved

Ammonia concentration

Total

Dissolved

Ammonia plus organic

concentration

Total

Dissolved

Phosphorus

Concentration

Total

Dissolved

Ortho

Discharge

Total

Dissolved

Ortho

Suspended sediment

Concentration

Discharge

Kendall's tau 

tau (p)

0.1607

.7757

.2678

.8224

.6449

.2857

.2857

.0467

.0841

-.1495

-.1963

-.1402

.1215

.1308

-.0089

.1696

.2037

-.0280

.0857

0.205

.00

.033

.00

.001

.023

.022

.758

.526

.233

.11

.274

.341

.301

.100

.183

.III

.866

.541

Significance

+

+

+

+

+

+

+

0

0

0

0

0

0

0

0

0

0

0

0

Estimate of slope

0.02 (mg/L)/yr

0.40 (mg/L)/yr

1.52 Ib/yr

.40 (mg/L)/yr

.35 (mg/L)/yr

1.41 Ib/yr

1.17 Ib/yr

.00 (mg/L)/yr

.00(mg/L)/yr

-.02 (mg/L)/yr

-.03 (mg/L)/yr

-.01 (mg/L)/yr

.00 (mg/L)/yr

.00 (mg/L)/yr

-.01 Ib/yr

.00 Ib/yr

.00 Ib/yr

.00 (mg/L)/yr

.25 Ib/yr

Median

.31

5.6

8.9

4.9

4.7

8.05

7.52

.04

.035

.60

.50

.05

.04

.03

.079

.056

.04

3.0

6.8

Water-Resources Investigations Report 93-4069 40
16

14

12

to

z<

§1

Table 13. Results of synoptic sampling of base flow at the Bald Eagle Creek gaging station,

tributary 1, and tributary 2

[Concentrations in milligrams per liter as N; --, data not available]

Concentration

Date Location

Total

nitrite plus Total nitrogen 

nitrate

Percentage total

nitrite plus

nitrate to total

nitrogen

September 27, 1990 Gaging station

1

2 

October 31, 1990 Gaging station

1

2 

December 12, 1990 Gaging station

1

2 

December 26, 1990 Gaging station

1

2

5.8

5.4 

5.8 

7.6

6.5 

8.2 

6.2 

5.9 

7.3 

5.6

7.3

6.3 

6.3

8.2

7.0 

8.9 

6.7 

6.3 

8.0 

6.2

79

86

92

93

93

92

93

94

91

90

I I I I I I I I I I I I I I T I TT II l I I I

KENDALL TREND 

- - TOTAL NITROGEN

yjA- ' ^ AKENDALL TREND- <* 

DISSOLVED NITRATE 

PLUS NITRITE - - TOTAL NITROGEN

«- DISSOLVED NITRATE PLUS NITRITE

i I i i i < I 0.001

10

0.01

0

z 

o

on 

tf

y

CD 

U

LLJ

9

CD

ONDJFMAMJ JASONDJFMAMJ JASONDJFMAMJ JASOND JFMAMJ JASONDJFMAMJ JAS 

1985 1986 1967 1966 1969 1990

Figure 12. Total nitrogen and dissolved nitrate plus nitrate concentrations in base flow 

prior to and during nutrient management.

41 Water-Resources Investigations Report 93-4069
cc

Ul

_J 

o: iu 

a.

DC 

CO

2 *

19 

O 

a:

TOTA 

NITRI

X

L X 

DGEN

 _

H1^

H

36

22

DISSOLVED 

NITRITE 

PLUS NITRATE

36 

22

PRIOR TO DURING PRIOR TO DURING 

MANAGEMENT MANAGEMENT MANAGEMENT MANAGEMENT

DETACHED VALUE1 

OUTSIDE VALUE2

UPPER WHISKER3 

7STH PERCENTILE

MEDIAN

25TH PERCENTILE

LOWER WHISKER3

1 A value >3 times the interquartile 

range from the box.

2 A value >1.5 and £3 times the 

interquartile range from the box.

3 Upper whisker is the largest data 

point less than or equal to the upper 

quartile range plus 1.5 times the 

interquartile range.. Lower whisker 

Is the smallest data point greater 

than minus 1.5 times the 

interquartile range.

4 n - number of observations 

in analysis.

Figure 13. Distribution of concentrations of total nitrogen and dissolved nitrite plus 

nitrate in base flow prior to and during nutrient management in the 

Bald Eagle Creek subbasin.

Ul 

0.

to

O

z 12

O 

Q_

Z

to

O 

O 

cc

Q TOTAL NITROGEN LOADS

DISSOLVED NITRITE PLUS NITRATE LOADS

o.ooi

ONOJFMAMJJASONOJFMAMJJASONOJFMAMJJASONDJFMAMJJASONDJFMAMJJAS 

1985 1986 1987 1988 1989 1990

Figure 14. Relation between discharges of total nitrogen and dissolved nitrite 

plus nitrate and base flow in Bald Eagle Creek.

Water Resources Investigations Report 93-4069 42
2.5

CC 

UJ

CC 

UJ 

O.

to

1 ,.»

13

2

Z

z 1 

to

UJ

o 

a o.s

i r i i i i i i i i i i i i i i i i i i i i i i

O TOTAL-ORGANIC NITROGEN

 DISSOLVED-ORGANIC NITROGEN

BASE FLOW

0

0

o 0

0 O® °0

 o ° o«

0 O 0 0 O ° i 

0 0.°- ' r>0 0

* * 

» o o ' e

O C

10

o

z 

o

, ato 

a:

I: 6?

o.i y

CO

u

z

o.oi E

UJ 

CO

'-J o.ooi

ONDJFMAMJJASONDJFMAMJJASONDJFMAMJJASONDJFMAMJJASONDJFMAMJJAS 

19B5 1986 1967 1966 1969 1990

Figure 15. Relation between concentrations of organic nitrogen and base flow of Bald Eagle Creek.

o:

UJ

0.

l/l 

2 

< 

ce

UJ 

13 

O

cr

TOTAL-AMMONIA NITROGEN 

DISSOLVED-AMMONIA NITROGEN

BASE FLOW

A A A A A

0.01 I I I I I I I I I ifri i^l I

A

A

A

to

o

1 bl

cr 

a.

t

y

03 

U

0.01

3

u.

UJ 3

CD

 * ' o.ooi

OND JFMAM J JASONO J FMAMJ JASOND JFMAMJ JASOND JFMAMJ JASOND JFMAMJ JAS 

1965 1986 1987 1986 1989 1990

Figure 16. Relation between concentrations of total and dissolved ammonia nitrogen and base flow 

in Bald Eagle Creek.

43 Water-Resources Investigations Report 93-4069
10

or uJ

Q. 

V\

1

ID

3

Z

2

0.1

O.O1

TOTAL

ORGANIC

NITROGEN

a

t

38

DISSOLVED 

ORGANIC NITROGEN

R

38

TOTAL 

AMMONIA

22 36

DISSOLVED 

AMMONIA

36

O

X

DETACHED VALUE1 

OUTSIDE VALUE2

UPPER WHISKER3 

75TH PERCENTILE

MEDIAN

25TH PERCENTILE

LOWER WHISKER3

1 A value >3 times the interquartile 

range from the box.

2 A value >1.5 and S3 times the 

interquartile range from the box.

3 Upper whisker is the largest data 

point less than or equal to the upper 

quartile range plus 1.5 times the 

interquartile range.. Lower whisker 

Is the smallest data point greater 

than minus 1.5 times the 

interquartile range.

4 n - number of observations 

in analysis.

Figure 17. Distribution of total and dissolved organic nitrogen and ammonia concentrations in 

base fbw prior to and during nutrient management in Bald Eagle Creek.

or

a 

to

1

u

U) D 

or 

o

a to 

o

o.

0.30

0.25

0.20

0.15

0.10

D.05

0.00

I I I I i i i

O TOTAL PHOSPHORUS

 DISSOLVED PHOSPHORUS

D DISSOLVED ORTHOPHOSPHORUS BASE FLOW

" a Q 

mo 

O o

OB o a

© © O O O

Q6D B OB -B ©

O

© OOB 

© B

D eaa

e o

© ©a

© 

9 

D

o 

B

a a . QD a a 

m a

 © 

aaa

©

O

©0 

O O' 

DO 

HO GD O

10

0.1

o

z 

o

V)

or

LJ

a

UJ

u. 

u

m

D 

U

3

u_ 

LJ

m

ONOJFMAMJJASONDJFMAMJJASONOJFMAMJJASONOJFMAMJJASONDJFMAMJJAS 

1985 19B6 1987 19B6 1989 1990

0.01

Figure 18. Relation between concentrations of total phosphorus, dissolved phosphorus, and 

orthophosphorus and base flow.

Water-Resources Investigations Report 93-4069
0.5

O TOTAL PHOSPHORUS

 DISSOLVED PHOSPHORUS

D ORTHO PHOSPHORUS

a

z

O

u

LJ 

V}

ex.

LJ

o_

t

y 

m

3

Z

3

LL 

UJ

3

m

0.0

ONDJFMAMJJASONDJFMAMJJASONDJFMAMJJASONDJFMAMJJASONDJFMAMJJAS 

1985 1986 1987 1988 1989 1990

Figure 19. Relation between discharges of total phosphorus, dissolved phosphorus, 

and orthophosphorus and base flow.

o.ot

on LJ

30

25

LJ 

Q.

to

2

a 20

CD

d

2

2 15

LJ

2

a

LJ

n 

Q

UJ 

Q

Z 

LJ 

Q.

10

I I I I I I I I I I I I

O SUSPENDED SEDIMENT

OO O

OO

BASE FLOW

O

OO 00

O O 

O OO 

O OO

00

.. P........ P. P?........... i... 9. P.

O O 

O

O O

10

Q

z

O

u

LJ 

V)

or LJ 

a.

LJ L_

y

m

u

o

LJ

3

m

ONDJFMAMJJASONDJFMAMJ JASONDJFMAMJ JASONDJFMAMJ JASONDJFMAMJ JAS 

1985 1986 1987 1988 1989 1990

0.01

Figure 20. Relation between concentrations of suspended sediment and base flow.

45 Water-Resources Investigations Report 93-4069
Stormflow. Trends in stormflow quality prior to and during nutrient management were difficult to determine 

because of the variability of runoff quantity and because only selected storms were sampled. Table 14 summarizes 

stormflow collected by water year. Twenty-eight of the 54 storms sampled were during the growing season. These

54 storms that were sampled during the study represent the quality and quantity of 84 percent of the total stormflow.

Table 15 lists the minimum and maximum concentrations of 11 constituents measured in stormflow. The 

maximum concentration of total nitrogen in stormflow was 61 mg/L on November 5, 1985. About 82 percent of the 

nitrogen in that sample was suspended-organic nitrogen. The maximum concentration of total nitrite plus nitrate was

5.5 mg/L measured in December 1989, and the maximum concentration of total ammonia was 10.0 mg/L measured in 

January 1988.

During stormflow, concentrations of total and dissolved phosphorus increased as water discharge and 

concentrations of suspended sediment increased. The maximum concentrations of total and dissolved phosphorus and 

orthophosphorus were measured prior to nutrient management and were 24, 6.0, and 3.7 mg/L, respectively. These 

concentrations were measured early in the study during the nongrowing season on November 5, 1985. During 

nutrient management, concentrations of total phosphorus, dissolved phosphorus, and orthophosphorus in stormflow 

were less than concentrations measured prior to nutrient management probably because the farmers reduced 

phosphorus applications to the cropland.

Sediment concentrations usually reached their peak just prior to or during the peak streamflow. The maximum 

concentration of suspended sediment prior to nutrient management was 8,730 mg/L on July 14, 1987, at a water 

discharge of 7.5 ft3/s, and the maximum concentration during nutrient management was 15,100 mg/L on July 4,1989, 

at a water discharge of 87 ft3/s.

Table 16 lists daily storm loads of nitrogen, phosphorus, and suspended sediment that were measured from 

October 1, 1985, to September 30, 1989. In order to calculate total storm loads, regression equations (table 17) were 

developed to estimate loadings for the 112 storm days that were not sampled. Storm days were determined on the 

basis of precipitation and streamflow records. Because the majority of sampled stormflow produced medium to high 

flows, only 16 percent of the total stormflow was not sampled (table 14).

The statistics listed in table 17 were derived from regressions between the log of the daily stormflow and the log 

of the daily nutrient and suspended sediment loads measured in the 54 sampled storms described earlier.

Table 18 summarizes the measured streamflow loads (table 16) and the estimated loads for stormflow by month 

for the 1986-89 water years. Loads of total nitrogen, total phosphorus, and suspended sediment increased 64, 74, and 

44 percent, to 6,119 Ib, 913 Ib, and 464,340 Ib, respectively, during the first 2 years of nutrient management, primarily 

in response to a 21 percent increase in precipitation.

Loads of suspended sediment in stormflow were greater in the growing season when the soils were disturbed 

from farming activities that increased erosion. Loads of total nitrogen and phosphorus were greater in the nongrowing 

season when plants are dormant and nutrients are concentrated in the soil and available to be transported to the stream 

in runoff. During May 1988 and May 1989 when 8.71 and 12.84 in. of precipitation fell, respectively (fig. 7), 24 

percent of the nitrogen, 19 percent of the phosphorus, and 36 percent of the suspended sediment for the entire study 

was discharged in stormflow.

In summary, the total loads in streamflow, prior to nutrient management, were 7,484 Ib of total nitrogen, 305 Ib 

of total phosphorus, and 264,785 Ib of suspended sediment (table 19). During the first 2 years of nutrient 

management, loads were 11,817 Ib of total nitrogen, 959 Ib of total phosphorus, and 467,166 Ib of suspended 

sediment, an increase of 37, 68, and 43 percent, respectively. The increase in nutrient and suspended-sediment loads 

during the first 2 years of nutrient management was because of the significant increase in precipitation. For the first 

4 years of the study, 43 percent of total nitrogen, 91 percent of total phosphorus, and 99 percent of suspended 

sediment were transported in stormflow.

Water-Resources Investigations Report 93-4069 46
Table 14. Number of storms, number of sampled storms, number of samples collected, and the percentage of total 

stormflow sampled at the Bald Eagle Creek site for the 1986-89 water years

Water Year

1986

1987

1988

1989 

Total

Total 

storms

31

32

28

23

114

Storms 

sampled

7

19

14

14

54

Number of 

samples

95

180

78

103

456

Percentage of total 

stormflow sampled

28

75

85

94

84

Table 15. Ranges of instantaneous streamflow and constituent concentrations in stormflow at Bald Eagle Creek for 

the 1986-89 water years

[Streamflow, in cubic feet per second; N, nitrogen; P, phosphorus; constituent concentration, in milligrams per liter; n, number of 

instantaneous samples and measurements; Min, minimum; Max, maximum; <, less than; , not determined]

Constituent

Streamflow

Nitrite + nitrate,

total as N

Nitrite + nitrate,

dissolved as N

Ammonia,

total as N

Ammonia,

dissolved as N

Ammonia + organic

nitrogen,

total as N

Ammonia + organic

nitrogen,

dissolved as N

Nitrogen,

total as N

Phosphorus,

total as P

Phosphorus,

dissolved as P

Orthophosphorus,

dissolved as P

Sediment,

suspended

1986 Water Year

Min

0.21

1.5

1.3

.06

.06

.90

.70

4.8

.03

.03

.02

3 4

Max

6.9

4.5

4.3

4.9

4.6

60

10

61

24

6

3.7

,350

n

95

19

19

19

18

19

18

19

19

18

18

81

1987 Water Year

Min Max

0.08 12

<.IO 4.3

.60 3.8

<.OI 6.7

.06 1.3

.40 28

<.20 7.9

3.8 32

.09 4.9

.15 1.5

.12 I.I

<l 8,730

n

180

77

13

77

13

75

13

73

77

13

13

150

1988 Water Year

Min Max n

0.34 105 78

.10 5.2 63

0

.04 10 63

0

.03 45 63

0

.60 23 61

.02 13 63

0

0

7 12,700 56

1989 Water Year

Min Max

0.19 147

.10 5.5

2.4 4.1

.03 3.9

.30 .97

.90 26

1.9 4.4

2.3 27

.11 9.3

.43 1.5

.38 1.3

17 15,100

n

103

47

10

47

10

47

10

46

47

10

10

83

47 Water-Resources Investigations Report 93-4069
52

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CO 

CD 

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i

0)

£ 

O

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Water-Resources Investigations Report 93-4069 48
Table 16. Daily nitrogen, phosphorus, and suspended-sediment loads during sampled storms at the Bald Eagle Creek site for the 1986-89 water years-Continued

4^ 

VD

$0i

i

CO3"§ £

H6'

CO

338

Date

1 1/29/8712/15/87

01/18/8801/20/8801/31/88

r02/01/88

-< 05/05/88

 05/06/88

05/17/88

05/18/88

4)5/19/88

07/23/88

08/29/8809/04/88

10/21/88

1 1/20/88

02/21/89

03/18/89

,03/24/89

J 05/05/89

[05/06/89

^05/23/89

1)5/24/89

06/07/89

r06/09/89

-S 07/04/89

07/05/8909/19/89

Daily

streamflow

6.5

.41

3.0

20.0

1.1

5.6

1.3

5.0

25.0

15.0

3.03.32.1

.91.77

2.8

.94.40

1.8

5.13.14.9

5.4

2.9

1.3

9.5

3.3

.93

Total

nitrite

plus

nitrate

58

9

48

146

11

6626

93

233

196

89

32

25

17

2160

4__-58

77-- 205

25- Dissolved nitrite plus Total nitrate ammonia 15.3 166 15328 1011025 15930628614 53 193 _ __ _ _ - -134 - - - -28 _ *j - Total Dissolved Dissolved organic organic ammonia nitrogen nitrogen DURING NUTRIENT MANAGEMENT 139.6 - - 260 - 41856 - 109 - 85 141 261 15852 191361536 14 110 70 13 _ _ _ __ - _ _ 7159 - - __ 11726 - Total nitrogen 19710 310 56467 175 111 234 494 354 141 223613257 17017__129 136__ 32251 Total Dissolved phosphorus phosphorus 71 .9 21 165420163923518 461438 28 18 17 _ __ 1716_ _ _ _ 2042- Dissolved ortho- Suspended phosphorus sediment 54,00086 1,080 5,330 187 23,600 13,800 11,000 94,000 46,000 6,340 22.000 2,600 426 1.110 18 4.830 209 246 1.440 28,300 7,820 38.300 1.134 3.100 867 6.190 340 780
Table 17. Regression statistics for estimating daily nitrogen, phosphorus, and suspended-sediment loads 

as a function of stormflow at the Bald Eagle Creek for the 1986-89 water years 

[Constituent loads, pounds per day; stormflow, cubic feet per second]

(x) 

Independent 

variable 

(log of stormflow)

Stormflow 

Stormflow 

Stormflow

(y)

Dependent variable 

(log of load)

Total nitrogen 

Total phosphorus 

Suspended sediment

(a) 

Slope

0.886714 

1.00475 

1.38486

y = ax+b

(b) 

Intercept

1.63302 

.680612 

-.295788

Standard error of estimate

Coefficient of 

determination (r2)

0.83 

.71 

.55

in log units

0.226 

.361 

.654

plus 

(in 

percent)

68 

129 

351

minus 

(in 

percent)

41 

56

78

Table 18. Measured and estimated nitrogen, phosphorus, and suspended-sediment loads in stormflow at Bald Eagle Creek 

for the 1986-89 water years 

[Loads, in pounds; , not determined]

Nitrogen Phosphorus Suspended sediment

Month Year Measured Estimated Total Measured Estimated Total Measured Estimated Total

NONGROWING SEASON

October

November

December

January

February

March

Subtotal

1985

1986

1987

1988

1985

1986

1987

1988

1985

1986

1987

1988

1986

1987

1988

1989

1986

1987

1988

1989

1986

1987

1988

1989

~

48

0

57

90

24

197

170

0

25

10

0

0

0

941

0

0

0

175

17

35

153

0

0

1,942

--

22

87

13

180

64

41

78

28

122

15

27

94

74

25

135

241

18

740

20

132

75

249

62

2,542

--

70

87

70

270

88

238

248

28

147

25

27

94

74

966

135

241

18

915

37

167

228

249

62

4,484

-

4.4

0

8

23

2

71

28

0

1

.9

0

0

0

190

0

0

0

20

17

2

8

0

0

375.3

-

2.1

8.9

1.2

19

6.2

4.2

7.8

2.9

15

1.4

2.5

9.6

7.7

2.6

15

26

1.8

104

2.1

14

7.9

33

6.6

301.5

-

6.5

8.9

9.2

41

8.2

75.2

35.8

2.9

16

2.3

2.5

9.6

7.7

192.6

15

26

1.8

124

19.1

16

15.9

33

6.6

676.8

--

5,324

0

1,100

2,683

6,334

54,000

4,830

0

39,624

86

0

16,500

0

6,597

0

8,260

80

23,600

209

235

25,700

0

1,686

196,848

~

240

1,420

140

3,260

840

640

1,200

510

2,420

180

320

1,620

1,260

440

3,560

5,140

260

46,700

300

2,820

1,300

12,800

1,200

88,570

~

5,564

1,420

1,240

5.943

7,174

54.640

6,030

510

42,044

266

320

18,120

1,260

7,037

3,560

13,400

340

70,300

509

3,055

27,000

12,800

2,886

285,418

Water-Resources Investigations Report 93-4069 50
Table 16. Measured and estimated nitrogen, phosphorus, and suspended-sediment loads in stormflow at Bald Eagle Creek 

for the 1986-89 water years-Continued 

(Loads, in pounds; --, not determined]

Month Year Measured

Nitrogen

Estimated Total Measured

Phosphorus

Estimated

Suspended sediment

Total Measured Estimated loud

GROWING SEASON

April 1986

1987

1988

1989

May 1986

1987

1988

1989

June 1986

1987

1988

1989

July 1986

1987

1988

1989

August 1986

1987

1988

1989

September 1986

1987

1988

1989

Subtotal

0

32

0

0

0

0

1,334

265

0

0

0

0

13

15

223

383

0

32

61

0

0

184

32

0

2,574

185

26

9

70

20

24

265

123

17

30

0

62

16

31

21

78

24

20

65

39

0

89

0

30

1,244

185

58

9

70

20

24

1,599

388

17

30

0

62

29

46

244

461

24

52

126

39

0

273

32

30

3,818

0

3

0

0

0

0

137

33

0

0

0

0

.9

4

46

62

0

3

14

0

0

21

3

0

326.9

21

2.8

9.1

7.6

2.1

2.5

30

14

1.7

2.9

0

6.6

1.5

3.2

2.1

8.5

2.3

1.8

7

4.3

0

9.1

0

3.2

143.3

21

5.8

9.1

7.6

2.1

2.5

167

47

1.7

2.9

0

6.6

2.4

7.2

48.1

70.5

2.3

4.8

21

4.3

0

30.1

3

3.2

470.2

0

843

0

0

0

0

171,140

75,554

0

0

0

3,967

236

33,100

22.000

6,530

386

3,230

2,600

0

0

88.809

426

780

409,601

4,940

480

1.600

1,480

300

400

7.580

3.600

240

380

0

1,220

200

400

320

1.800

260

200

1,320

860

0

1.420

0

560

29.560

4.940

1,323

1.600

1.480

300

400

178,720

79.150

240

380

0

5,187

436

33,500

22,320

8,330

646

3,430

3,920

860

0

90,229

426

1,340

439,161

Prior to nutrient management

1986

1987

Subtotal

138

513

651

937

595

1,532

1,075

1,108

2,183

25.9

46.4

72.3

100.1

63

163.1

126

109.4

235.4

28,300

203,044

231,344

19.290

9,600

28.890

47,590

212,644

260,234

During nutrient management

1988

1989

Subtotal

Grand total

2,973

892

3,865

4,516

1,517

737

2,254

3,786

4,490

1,629

6,119

8,302

481.9

148

629.9

702.2

202.3

79.4

281.7

444.8

684.2

227.4

911.6

1,147

280,449

94,656

375,105

606.449

73,000

16,240

89,240

118.130

353,499

110,896

464,345

724,579

51 Water-Resources Investigations Report 93-4069
Table 19. Total base flow and stormflow loads for total nitrogen, total phosphorus, and suspended sediment in 

Bald Eagle Creek for the 1986-89 water years 

[Load, in pounds]

Water year

Base flow Stormflow

Nitrogen Phosphorus Suspended 

sediment Nitrogen Phosphorus Suspended sediment

1986

1987

Subtotal

2,744

2,557

5,301

34.6

35.8

70.4

2,417

2,134

4,551

1,075

1,108

2,183

126

109

235

47,590

212,644

260,234

1988

1989 

Subtotal 

Total

GRAND TOTAL 

Nitrogen 

Phosphorus

Suspended 

sediment

2,470

3,228

5.698

10,999

19,301

1,264

731,951

18.4

28.2

46.6

117

1,119

1,702

2.821

7,372

4,480

1,629

6.119

8,302

684

228

912

1,147

353,499

110,896

464.345

724,579

Water-Resources Investigations Report 93-4069 52
Ground Water

Ground-water-level and ground-water-quality data for the study area were based primarily on historical data. 

However, current ground-water-level data and base-flow data support the historical findings.

Availability and occurrence

The availability of ground water is dependent on the capacity, storage characteristics, and transmissivity of the 

underlying rock structure. Much of the available ground water in the Wissahickon Formation is at shallow depths in 

the partially weathered bedrock and in a deeper network of joints and fractured cleavage planes (Gary Barton, U.S. 

Geological Survey, written commun., 1992). Wells drilled into the Wissahickon Formation usually provide sufficient 

water for domestic purposes. The greatest density of water-bearing zones are within 50-100 ft of the land surface; 

below 150 ft, the density of water-bearing zones decreases with increasing depth (Dennis Low, U.S. Geological 

Survey, written commun., 1991).

The topographic position of well sites significantly affect well yields. Yields from wells drilled in valleys are 

greater than yields from wells drilled on hillslopes or ridgetops. Lloyd and Growitz (1977) report that 1-hr specific 

capacities of 72 wells in the Wissahickon Formation ranged from 0.03 to 50 (gal/min)/ft; the median was 

0.95 (gal/min)/ft. The average yield for a well drilled 400 ft deep is about 45 gal/min with 50 ft of drawdown after 

pumping 1 hr; after pumping for 24 hrs, the average yield is about 30 gal/min. The maximum yield measured for a 

well in this formation was 150 gal/min (Lloyd and Growitz, 1977). In a recent study by the USGS delineating 

wellhead-protection areas in Stewartstown, Pa., approximately 7 mi west of Bald Eagle Creek, specific capacities 

ranged from 0.001 to 1.4 (gal/min)/ft and yields ranged from 0.03 to 64 gal/min (Gary Barton, U.S. Geological 

Survey, written commun., 1992).

Recharge

In basins where surface water is largely comprised of base flow, factors influencing the presence of ground water 

are important to recharge. Ground-water recharge is dependent upon the size and shape of the ground water basin, the 

annual precipitation, surface runoff, soil infiltration, and evapotranspiration. The size and shape of the ground-water 

boundary at the site is assumed to be approximated by the surface-water subbasin boundary (fig. 2). Precipitation is 

the single input to recharge the ground-water system, whereas, ground-water seepage (base flow) to Bald Eagle 

Creek, seepage to the pond (fig. 2), and evapotranspiration are the three outputs discharged from the ground-water 

system.

The Wissahickon Formation also is in the East Branch Brandywine Creek Basin above Downington (USGS 

station number 01480700). This watershed has similar basin characteristics as Bald Eagle Creek. The average annual 

recharge to the ground water for the period 1974 through 1988 was estimated to be 15.4 in/yr or 32 percent of the 

annual precipitation (Ron Sloto, U. S. Geological Survey, written commun., 1992). Therefore, ground-water recharge 

at Bald Eagle Creek is estimated to be 15 in/yr.

Typically, ground water is recharged during March and April (after the spring thaw, but before the growing 

season) and between October and December (after crops are harvested but before the ground freezes). Ground-water 

levels usually decline during the growing season from April through September when evapotranspiration permits 

only small amounts of infiltrated water to recharge the saturated zone. Therefore, seasonal variations in precipitation 

can be more critical to the recharge of ground water than the annual total precipitation.

The relation between precipitation and base flow measured at Bald Eagle Creek and the ground-water level at 

observation well YO 180 (fig. 1), located about 20 mi north of the study area, is shown in figure 21. Well YO 180 is 

part of the USGS ground-water observation network and represents typical ground-water conditions in the region of 

the study site. The corresponding amplitudes suggests a positive relation between precipitation, base flow, and 

ground-water levels with a lag time in the order of 1 to 2 months. This relation was determined not to be significant. 

Ground-water levels and base flow increased rapidly in November 1985, November 1986, May 1988, and May 1989 

in response to increased precipitation. Ground-water levels decreased steadily in May, June, and July 1986, May, 

June, July, and August 1987, and June through September 1988. During the growing season, especially summer 

months, evapotranspiration increases and precipitation generally decreases. The relation between ground-water levels 

and base flow suggests the seasonal influences on both are similar. The rise in ground-water levels at well YO 180 

and the increase in precipitation over the 5-year study period is shown in figure 21.

S3 Water-Resources Investigations Report 93-4069
seojnosey-jejBM suoiiB6i)seAU| Uodey 690P-G6 

FEET IN SURFACE, LAND FROM WATER TO DETPH 

3

(Q

5

K>

JJ 

0>

55"

3

fil

6 

p

Q. 

&>.

«< 

(Q

3

Q.

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6) 

Q.

(Q

3

01 

Q. 

Q. 

01

INCHES IN PRECIPITATION, 

SECOND PER FEET CUBIC IN FLOW, BASE 
Quality

The quality of ground water is determined by the precipitation quality, composition of the soil and aquifer, 

nutrient applications to the soil through which infiltrated water flows, and residence time in the aquifer. Historical 

data indicate ground water from water-bearing zones in the Wissahickon Formation is generally soft with low 

concentrations of dissolved solids (Lloyd and Growitz, 1977). Hardness ranged from 17 to 170 mg/L on the basis of 

measurements from 92 wells sampled between November 1968 and December 1970; the median hardness was 

34 mg/L. Field pH ranged from 5.0 to 7.0 on the basis of measurements in 48 wells in the Wissahickon Formation. 

Specific conductance ranged from 250 to 560 u,S/cm in 115 wells; the median specific conductance was 125 u,S/cm.

Concentrations of nitrate in the ground water commonly were elevated. Concentrations of nitrate nitrogen as N 

ranged from 0.5 to 21 mg/L in 34 samples; the median concentration was 6.3 mg/L. The maximum nitrate 

concentration measured in ground water of the noncarbonate rocks in southern York County was in the Wissahickon 

Formation (Lloyd and Growitz, 1977).

Water-quality samples collected from a production well in Stewartstown, Pa., had a specific conductance of 

137 uS/cm, hardness of 36 mg/L, field pH of 5.9 units, concentration of dissolved nitrite plus nitrate of 5.4 mg/L as 

N, and iron and lead concentrations of 26 and 10 ng/L, respectively (Durlin and SchafTstall, 1991).

Soils and Soil Nutrients

Soil depths at the site were shallow, often less than 36 in. deep, especially the soil sampling locations at Farm 2 

(fig. 2). The animal density also was lower at Bald Eagle Creek than at Brush Run and Little Concstoga Creek. 

Therefore, the total nutrient content of the soils at the Bald Eagle Creek site was probably lower than in fields at the 

shale site in Adams County (Brush Run) and the carbonate site of the RCWP Nutrient-Management Subbasin (Little 

Concstoga Creek) in Lancaster County (sites 2 and 3, fig. 1) simply because of the difference in soil depths and 

animal density.

Because soil nutrient concentrations were highly variable, no trends were apparent in concentrations of nitrate 

nitrogen in the soil with respect to season, or as a result of reductions in nutrient applications. Investigators have 

recognized the difficulty in collecting and interpreting representative soil samples because of varying soil and 

climatic conditions. Harmscn and Van Schreven (1955) stated reliable interpretations of soil data could be made when 

dealing with a single soil type, climatic zone, or farming system. However, variations occur from the same field for a 

number of reasons-different application rates for fertilizers, different subsurface water flow and nutrient transport 

paths, and different rates of nutrient uptake by plants.

Soils were sampled at Farm 1 on November 20, 1985, and at Farms 1 and 2 on May 20 and October 26, 1987, 

April 13 and October 15, 1988, April 15 and October 27, 1989, April 10 and November 15, 1990 (figs. 22 and 23), 

and analyzed for concentrations of nitrate nitrogen and phosphorus by the Pennsylvania State University, College of 

Agronomy, and reported to the USGS in pounds per acre. Methods of soil collection are described in the 

characterization report by Fishcl and others (1991). The concentrations of nitrate nitrogen reflect the nitrogen 

immediately available to the plants, but may actually be a small percentage of the total nitrogen in the soil (fig. 22). 

Stevenson (1982) indicates that nitrogen from ammonia, or nitrogen that may become available from mineralization 

and nitrification of residual organic nitrogen in the soil, may comprise over 90 percent of the nitrogen in surface 

layers of most soils. Therefore, the concentrations of nitrate nitrogen measured may only represent one tenth of the 

nitrogen held in the soil at any particular time.

Concentrations of nitrate and soluble phosphorus were generally lower in the Bald Eagle Creek subbasin than in 

the Brush Run and Nutrient-Management Subbasins in the Little Conestoga Creek basin. The total amount of nitratenitrogen and soluble phosphorus in the Bald Eagle Creek Basin in the top 48 in. of soil ranged from 36 to 135 Ib/acrc 

and 0.39 to 2.5 Ib/acre, respectively, prior to nutrient management (table 20). Concentrations of nitrate-nitrogen and 

soluble phosphorus in soil samples collected during the nutrient-management period ranged from 21 to 291 Ib/acrc 

and 0.73 to 1.7 Ib/acrc, respectively, in the top 48 in. of soil.

55 Water-Resources Investigations Report 93-4069
Table 20. Results of soil sampling at the Bald Eagle Creek Basin, Nutrient-Management Subbasin, and Brush Run 

study areas

[NM, nutrient management; Ib/acre, pounds per acre; , data not available]

Location

Bald Eagle Nutrient-Management Brush Run 

Creek Subbasin Creek

Number of samples 34 40 73 

Nitrate-nitrogen in soil

range (Ib/acre)

Percent greater than 

50 Ib/acre

Percent greater than 

100 Ib/acre

Soluble phosphorus in soil 

range in Ib/acre

prior to NM 

during NM

entire study

entire study

prior to NM 

during NM

36. -135 

21. -291

74

29

.39- 2.5 

.73- 1.7

46.-380

95

50

1.4-37

21 -452 

1 7 -386

77

46

.98- 93 

.29- 65

Results shown in table 20 can be explained because of the thin soils, the lower manure application rates, and the 

di (Terence in the composition of the manure used at the Bald Eagle Creek site from the other sites. Only dairy manure 

that contains less nitrogen and phosphorus than poultry or swine manure (Pennsylvania State University, Agronomy 

Guide, 1987-88) was applied at the Bald Eagle Creek site. Also, the animal density at the Bald Eagle Creek site was 

less than the animal density at the Nutrient-Management Subbasin and Brush Run site and less nutrients were applied 

at the Bald Eagle Creek site than at the Nutrient-Management Subbasin where poultry, hog, and dairy manure were 

applied. For example, the phosphorus content (P2O5 ) of the dairy manure at Farm 1 was 4.9 Ib/ton as compared to 54 

Ib/ton of phosphorus for turkey manure applied at Farm A in the Nutrient-Management Subbasin (Fishel and others, 

1991).

Soil nutrients in the Bald Eagle Creek Basin were highly variable between fields and between seasons (figs. 22 

and 23). However, nitrate concentrations were generally more uniform throughout the soil column in the Bald Eagle 

Creek subbasin than in the Brush Run and Nutrient-Management Subbasins. The data from the Bald Eagle Creek 

subbasin suggest that nitrate is highly mobile and infiltrated readily through the soil, because at times the highest 

concentrations were at depths between 24 to 48 in. below the surface (fig. 22). Similar observations were made in the 

noncarbonate shaley soils at Brush Run and the carbonate soils at the Nutrient-Management Subbasin (Fishel and 

others, 1992). In contrast to the nitrate concentrations, concentrations of phosphorus were greatest in the top 8 in. of 

the soil where fine soil particles absorb phosphorus (Finkl and Simonson, 1979, p. 374). Elevated concentrations of 

phosphorus are more likely to be present in the soil in spring before planting rather than the fall. Studies have shown 

that 69 to 80 percent of the total phosphorus in soil may be leached from dead or dormant vegetation (Ed Kocrklc, 

U.S. Gco-logical Survey, written commun., 1992).

Soil monitoring studies in Nebraska, Iowa, and Wisconsin (Halberg and others, 1984; Rehm and others, 1983, 

p. 8-10) suggest that less than 100 Ib/acre of nitrate nitrogen should remain in the top 48 in. of soil to insure that 

leachate to the ground water will not exceed 20 mg/L nitrate nitrogen. However, Baker (the Pennsylvania State 

University, College of Agriculture, Department of Agronomy, written commun., 1985) states that a more desirable 

environmental level for nitrate-nitrogen may be 50 Ib/acre in the upper 48 in. of soil. Table 19 also indicates the 

percentage of soil samples exceeding 50 Ib/acre and 100 Ib/acre at Bald Eagle Creek is less than that at the Brush Run 

site and the Nutrient-Management Subbasin. Soil data in table 20 indicate that all three sites contain more than 

50 Ib/acre of soluble nitrate-nitrogen, but less than half of the soil samples contain more than 100 Ib/acre.

Water-Resources Investigations Report 93-4069 56
300

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OL

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CZJ B TO 24 INCHES BELOW THE SURFACE 

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SITE 4

Figure 22. Soluble nitrate-nitrogen yields in selected soil increments on four fields 

in the Bald Eagle Creek Basin.

57 Water-Resources Investigations Report 93-4069
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Figure 23. Soluble phosphorus yields in selected soil increments on four fields in 

the Bald Eagle Creek Basin.

Water Resources Investigations Report 93-4069
EFFECTS OF CHANGES IN NUTRIENT APPLICATIONS, 

LAND USE, AND RANDOM EVENTS ON SURFACE-WATER QUALITY

Chanyes in Nutrient Applications

Farmers at the Bald Eagle Creek site, like those at the Small Watershed site in Lancaster County being studied as 

part of the RCWP, began reducing nutrient applications prior to the development of nutrient-management plans for 

their farms. This action taken voluntarily by the farmers prior to the implementation of nutrient management added 

an immeasurable variability in the premanagemcnt data. It also created levels in both nutrient applications and 

concentrations and discharges of nutrients and suspended sediment in surface water that were probably different than 

previous levels.

Since nutrient-management plans were not implemented at the Bald Eagle Creek subbasin, the objectives of the 

study were modified when the animal population decreased just as the nutrient-management period was to begin. 

Data collection continued to monitor the effects of a reduction in animal units and a corresponding reduction in 

nutrient applications from animal waste. This was a rare opportunity to monitor these effects because few fanners arc 

willing to voluntarily reduce their animal populations. Because of the reduction in animal units, corresponding feed 

requirements were reduced; thus, cropping patterns and nutrient applications changed. All of these changes were 

made without technical assistance from the nutrient-management specialist. Also, at the same time, one landowner 

permitted several head of cattle to graze near and immediately upstream from the sampling and gaging cross-section.

The reduction in animals units from 0.85 AU prior to nutrient management to 0.43 AU during nutrient 

management resulted in a 40 percent reduction in manure nitrogen and a 15 percent reduction in manure phosphorus 

applications to cropland and pasture. Additionally, commercial applications of nitrogen and phosphorus were reduced 

70 percent and 64 percent, respectively, during the first 2 years of nutrient management when 41 percent less acreage 

was planted in corn. In summary, nitrogen and phosphorus applications were reduced by 19,900 Ib (83 Ib/acre) and 

5,000 Ib (21 Ib/acrc), respectively, during the nutrient-management period (table 5).

The increased use of manure-storage facilities also may effect the rate and timing of nutrient applications. If open 

storage facilities gain wider acceptance in the study area, nutrients can be conserved and applied when crops can 

readily utilize them. Recent studies by Langland (1992) and van Brecman and others (1982) indicate that nitrogen 

concentrations in precipitation, especially ammonia, may be significant near manure storage facilities.

Although applications of manure and commercial fertilizers were reduced, a significant increasing trend was 

detected in concentrations and loads of total nitrogen and dissolved nitrite plus nitrate in base flow. Concentrations 

and loads of total nitrogen and dissolved nitrite plus nitrate also increased in stormflow. However, significant trends 

were not detected in concentrations and discharges in total and dissolved ammonia, ammonia plus organic nitrogen, 

total and dissolved phosphorus, and orthophosphorus.

Without the determination of true long-term levels in nutrient applications, the evaluation of cause and effects 

between changes in nutrient applications and detected changes in water quality by use of statistical methods became 

difficult. Fishel and others (1991) used the seasonal rank-sum test to establish target goals to show what reductions in 

concentrations and discharges of nutrients and suspended sediment in base flow would result in statistically 

significant changes in water quality. These estimates were made by use of measured variation from the premanagemcnt data. Comparisons were made of the estimated and actual measured changes (reductions or increases) in 

nutrient concentrations and discharges by use of water-quality data collected during the nutrient-management period. 

Because changes were constantly occurring in nutrient applications, cropping patterns, and precipitation, and 

knowing that the variation of the data during the management phase would probably be different than the variation of 

the data prior to the management phase, estimates were made for the entire study period of new reductions needed to 

detect significant changes in base-flow water quality (table 21).

The estimated and actual changes required to have the highest probability of detecting a significant change 

(p<.05) in base-flow water quality are listed in table 21. Because nutrient management was expected to cause 

reductions in nutrient concentrations and loads in base flow, a one-tailed test was used to estimate reductions. 

However, measured changes from table 21 show that all nutrient concentrations and loads increased except the 

concentration of total phosphorus. The measured changes in concentrations of total nitrogen and dissolved nitrite plus 

nitrate exceeded the estimated concentrations required to detect a significant change, and therefore, were considered 

to be significant.

59 Water-Resources Investigations Report 93-4069
Table 21. Estimates of reductions required in mean concentrations and mean loads to achieve statistically significant

changes in base-flow water quality in the Bald Eagle Creek Basin

[N, nitrogen; P, phosphorus; concentration, in milligrams per liter; load, in pounds; estimated reduction, in percent]

Constituent

Prior to nutrient management 

Estimated reductions required

During nutrient management 

True measured changes

Entire study period 

New estimated reductions

Value Percent Change Value Percent Change Value Percent Change

Nitrite plus nitrate, dissolved as N 

Concentration 4.2

Load 6.9

Nitrogen, total as N 

Concentration 4.9

Load 8.2

Phosphorus, total as P 

Concentration .06

Load .09

Phosphorus, dissolved as P 

Concentration .03

Load .06

-14

-65

-12

-62

-48

-57

-43

-90

-0.59

-4.5

-.59

-4.3

-.03

-.05

-.01

-.05

5.0

9.8

5.9

11.6

.05

.11

.04

.09

+16

+34

+17

+29

-17

+ 18

+25

+33

+0.80

+2.9

+ 1.0

+3.4

-.01

+ .02

+ .01

+ .03

4.7

8.7

5.5

10.2

.06

.11

.04

.08

-II

-42

-II

-41

-71

-58

-36

-62

-0.52

-3.6

-.60

-4.2

-.04

-.06

-.01

-.05

Table 22 lists the means, standard deviations, and number of observations of the concentrations and loads of 

water quality characteristics analyzed during the study period and the growing and nongrowing seasons. Data from 

table 22 were used as inputs to the Monte-Carlo simulation to obtain the estimates for detecting a significant change 

in water quality. The nonparametric test Univariate (SAS) determined the data for the entire study period approached 

normality, therefore log transformations of the data were not required.

The probability of detecting a significant change in base-flow water quality when selected reductions in concentrations and loads are achieved was determined by use of a modified form of the nonparametric Wilcoxon-MannWhitney rank-sum test (figs. 24 and 25). The power of the seasonal rank-sum test (1-P) represents the probability of 

rejecting the null hypothesis when in fact it is false and the alternative hypothesis is true. The null hypotheses is that 

there is no difference in the means of the water-quality data collected prior to nutrient management and during nutrient management when the nutrient management data are reduced by the indicated percentages. Therefore, the power 

of the test gives the probability of detecting a change in base-flow water quality during the nutrient-management 

phase if the constituents were reduced by the indicated percentage. Greater reductions are required in nutrient loads 

than in concentrations because of increased variability of load data. In general, greater reductions are required for 

phosphorus concentrations and loads than nitrogen concentrations and loads for the Bald Eagle Creek site.

Power curves for Bald Eagle Creek are similar to these curves of other small forested and undisturbed watersheds in the Lower Susquehanna River Basin for two reasons. First, the effect of animal density is minimal, relative 

to the highly intensive farmed basins such as the agricultural Nutrient-Management and Brush Run subbasins where 

animal densities are greater. Second, at the Bald Eagle Creek site where the soils on steep slopes are underlain by 

schist, like at the RCWP Forested Subbasin in the Nutrient-Management Subbasin in the Conestoga Creek, where 

Triassic sandstone ridges are predominate, the geology and topography permit rapid transport of ground water 

through shallow subsurface soils with little leaching before it is released as base flow. In contrast, at the NutrientManagement Subbasin, which lies within a carbonate valley, and the Brush Run Subbasin, which lies within noncarbonate terrain, the geology and topography permit longer subsurface transport of ground water through deeper 

soils, rich in nutrients before being released as base flow.

Several studies have associated specific concentrations of inorganic nitrogen and total phosphorus with particular 

environmental conditions. For example, 0.3 mg/L of inorganic nitrogen (nitrite, nitrate, and ammonia), and 0.01 

mg/L of phosphorus are critical concentrations that, when exceeded, can stimulate excessive growth of algae in 

streams (McKee and Wolf, 1963; Harms and others, 1974). MacKenthum (1969) indicates that total phosphorus 

should not exceed 0.1 mg/L; the USEPA (1986) recommends total phosphorus should not exceed 0.05 mg/L if 

nuisance growths in free-flowing streams are to be prevented. All of the 266 samples collected at the Bald Eagle 

Creek site exceeded the critical concentration for inorganic nitrogen, 80 percent of the 266 samples exceeded the total 

phosphorus concentration suggested by MacKenthum (1969), and 86 percent of the 266 samples exceeded the 

0.05 mg/L concentration recommended by the USEPA. Because water-quality criteria have not been established for 

nutrient loadings from nonpoint sources, the effects of reducing nitrogen and phosphorus loads on aquatic 

environments in stream reaches cannot be evaluated at this time.

Water-Resources Investigations Report 93-4069 60
Table 22. Water-quality characteristics of base (low at the Bald Eagle Creek site

[N, nitrogen; P, phosphorus; concentration, in milligrams per liter; load, in pounds; standard deviation, in percent except where

noted; n, number of samples]

Water-quality .. . . 

_, __ ? _: .:' Management period characteristic 

Mean Standard 

deviation

Plus

n

Nongrowing season

Mean

Minus

Standard 

deviation

Plus Minus

n Mean

Growing season

Standard 

deviation

Plus Minus

n

PRIOR TO NUTRIENT MANAGEMENT

Nitrite plus nitrate, dissolved as N

Concentration 4.2

Load 6.9

Nitrogen, total as N

Concentration 4.9

Load 8.2

Phosphorus, total as P

Concentration .06

Load .09

Phosphorus, dissolved as P

Concentration .03

Load .06

a !2

2.9

a !2

3.4

"33

a67

a67

.03

a !2

2.9

a io

3.4

a33

844

a33

.03

22

22

22

22

*

 21

21

22

22

4.6

8.4

5.4

8.4

.05

.08

.03

.07

"9

2.9

a8

4.1

a60

"NO

a64

.04

a8

2.9

a7

4.1

a40

B50

339

.04

10

10

10

10

10

10

10

10

3.9

5.6

4.6

8.0

.06

.09

.03

.06

a8

2.2

a8

2.8

a36

a56

a43

.03

a8

2.2

a7

2.8

a26

a33

a30

.03

12

12

12

12

II

N

12

12

ENTIRE STUDY PERIOD

Nitrite plus nitrate, dissolved as N

Concentration 4.7

Load 8.7

Nitrogen, total as N

Concentration 5.5

Load 10.2

Phosphorus, total as P

Concentration .OS

Load . 1 1

Phosphorus, dissolved as P

Concentration .04

Load .08

.66

5.1

.74

5.9

.03

.09

.02

.07

.66

5.1

.74

5.9

.03

.09

.02

.07

58

58

58

58

57

57

58

58

4.9

8.8

5.7

10.4

.05

.10

.04

.08

.57

5.9

.64

6.8

.02

.10

.02

.07

.57

5.9

.64

6.8

.02

.10

.02

.07

27

27

27

27

27

27

27

27

4.6

8.6

5.4

10.7

.06

.11

.04

.08

.70

4.3

.79

5.0

.03

.08

.03

.08

.70

4.3

.79

5.0

.03

.08

.03

.08

31

31

31

31

30

30

31

31

a Results fur these constituents come from log transformed data.

61 Water-Resources Investigations Report 93-4069
o.e

0.6

UJf.

O 0.4 

Q.

0.2

I//'

¥ f ...... .......J....f. ......

U 1

ill /

---/ /-"/ - /I/ / : : / ' i - ..... yTy.........

///

i

"/"

t... ........

w

^

............

20 40 60

o.e

CO Q.6

OL

UJ

*

O 0.4

O.

0.2

\(

r

80 100

REDUCTION OR INCREASE OF TOTAL-NITROGEN 

CONCENTRATION IN BASE FLOW. IN PERCENT

0 20 40 60 80 100

REDUCTION OR INCREASE OF DISSOLVED-NITRITE PLUS 

NITRATE CONCENTRATION IN BASE FLOW, IN PERCENT

O.B

03 0.6

QL 

liJ

O 0.4 Q.

0.2

m

0.8

o.s

0.4

0.2

0 20 40 60 80 100

REDUCTION OR INCREASE OF TOTAL-NITROGEN 

LOAD IN BASE FLOW. IN PERCENT

........

/ /

° 20 40 60 80 100

REDUCTION OR INCREASE OF DISSOLVED-NITRITE PLUS 

NITRATE LOAD IN BASE FLOW. IN PERCENT

EXPLANATION

................ BALD EAGLE CREEK

 FORESTED SUBBASIN

 - NUTRIENT-MANAGEMENT SUBBASIN

 - BRUSH RUN

Figure 24. Probability of achieving statistically significant changes in base flow water quality at selected 

reductions or increases in total nitrogen and dissolved nitrite plus nitrate concentrations.

Water-Resources Investigations Report 93-4069 62
o.a

0.6

oc

UJi

O 0.4

o_

0.2

i /

1UIII'

111 

///!

/ *>

m

o.a

0.6

111

O 0.4

a

0.2

0 20 40 60 BO 100

REDUCTION OR INCREASE OF TOTAL PHOSPHORUS

CONCENTRATION IN BASEFLOW, IN PERCENT

0 20 40 60 80 100

REDUCTION OR INCREASE OF DISSOLVED-PHOSPHORUS 

CONCENTRATION IN BASEFLOW, IN PERCENT

o.a

CD 0.6

or

UJi

O 0.4 

Q.

0.2

Ill

fi U20 40

o.a

0.6

>w>

o:

O 0.4 

O_

0.2

60 eo too

il,

REDUCTION OR INCREASE OF TOTAL PHOSPHORUS 

LOAD IN BASEFLOW, IN PERCENT

0 20 40 60 80 100 

REDUCTION OR INCREASE OF DISSOLVED-PHOSPHORUS 

LOAD IN BASEFLOW, IN PERCENT

EXPLANATION 

................ BALD EAGLE CREEK

 FORESTED SUBBASIN

 - - - NUTRIENT-MANAGEMENT SUBBASIN

 - BRUSH RUN

Figure 25. Probability of achieving statistically significant changes in base flow water quality at selected 

reductions or increases in total- and dissolved-phosphorus concentrations and loads in base flow.

63 Water-Resources Investigations Report 93-4069
Changes in Land Use

Although agriculture continued to be the dominant land use at the study area throughout the study period, the 

overall intensity of agriculture was reduced during the nutrient-management phase. In addition to the reduction of 

animal density from 0.85 to 0.43 AU/acre, the amount of cropland planted in corn changed annually and decreased 

from an average of 93 acres prior to nutrient management to 61 acres during the 3 years of nutrient management The 

reductions in land applications of commercial and manure fertilizers and the changes in cropping patterns may have 

resulted in a reduction of excess nitrogen available to leach into the ground-water system. This reduction, however, 

was not enough to produce a statistically significant decrease in base-flow concentrations of total nitrogen or 

dissolved nitrite plus nitrate.

In each of the 5 years of the project, more nitrogen was applied to the land surface than was estimated to be 

removed by crops (table 23). Prior to nutrient management, approximately 23,150 Ib/yr (205 Ib/acre) more nitrogen 

was applied than was estimated to be removed by crops. During nutrient management, when applications of fertilizers 

decreased, about 9,030 Ib/yr (157 Ib/acre) more nitrogen was applied than was estimated to be removed by crops. The 

estimates of nitrogen removal and addition, which are based on crop type, crop yield, and crop acreage, were obtained 

from the Penn State Agronomy Guide (1987) and Bob Anderson (Perm State Agricultural Extension Service, written 

common., 1991).

The annual differences in nitrogen removal by crops and nitrogen additions from fertilizer applications and 

legumes are represented by the shaded area (excess nitrogen) in figure 26. The excess nitrogen is the difference 

between nitrogen applications and nitrogen removal and may represent the annual amount of nitrogen available for 

transport to the surface-water and ground-water systems.

90,000

 ADDITIONS 

D REMOVAL

Figure 26. Estimated 

differences between 

nitrogen additions from 

fertilizer applications and 

legumes, and nitrogen 

removal by crops for 

1986-90 water years at 

Bald Eagle Creek.

19 87 19B8 1989 1990

The changes in crop type discussed earlier and the resultant changes in nutrient utilization by the crops increased 

the transport availability of nitrogen and soluble phosphorus to the stream directly in surface runoff or indirectly to 

the ground water which later is released to the stream as base flow.

The landowner near the gaging cross-section and sampling site made several land-use changes that probably had 

an immediate effect on the surface-water quality. On two occasions, modifications were made to the stream channel 

by straightening and deepening the channel to prevent flooding of pasture land. The farmer also placed fill material 

soil along the streambank and in the pasture several hundred feet upstream from the gaging pool. The nutrient content 

of the fill material was unknown. However, because they were exposed soils, the potential for increases in nutrient 

transport in surface runoff during storms and the leaching of nutrients to ground water was increased.

The landowner at this site also permitted additional cattle to graze in the pasture upstream from the waier-qualily 

sampling site during the nutrient-management period This may have increased the potential for nutrients to be 

deposited in the stream or transported to the stream in runoff. No management plan was developed for this landowner 

because his animal population consisted of a few steers and hogs raised for his own consumption and his cropland 

was located outside the basin.

Water-Resources Investigations Report 93-4069 64
 o

CO

1

1 °.

S

0

I

1

E

S

c

'Ef

ra

E

Q) 

T3

C

ra

to

Q)

E

n

f

ra

Q) 

N

C

7J

o

<0

E

E

8

T3

CO

0)

1 CO ^*O

E v- o

 R » c 

0 8? f

S 6 i-

~ & c

S

*^ O) « 

ca -

= UJ V

Ci. ^"

&15 1

o «± 2 Sr ca o. ^ 

_o ro o

=6 >< JJ3

CO *P uf

c 2 s

 = 

tf CD -H1

Table 23.Estimated rstormflow forthe198 [Total N, total nitrogen

o

ON

"~

ON

00ON

00

oo

ON

r00 

ON

NO

00 ON

Z

*«3

(2

~- £> £ §CO

B^

z

o*""

- **

£ £

c/]

1

Z

5

fr"

~- £J

£ a

|

Z

"3

p

£|

C/J

1

Z

S

H

- 1

1

^

S o o l*» r*i

<N CS 1^1

r-" <N ON*

VO* <* 0

000 

ro CO f*>

 ** oo CS

0 O O

TT vo ""^

oo vo *O

 <N

0 O O ON W> ^J- 

«/ > ON «O

>-" -"1* NO*

 IN r*i

CX 

g §

Nitrogen applications Manure nitrogen Commercial nitrog 

Subtotal 

Nitrogen additions by

« vo | ^

TT vo 

 *" NO*

00 ,

VO ^ O

I/S <N I 00 

«O 5f O\

IN IN I ^ 

f> ON ' NO

^t CS* NO*

O O 1

00 ^f '

^ rO I""*-

fi CN i «/i i^l vo ' 

J vo | O

fl <N i^)

O O 1

00 -*

ro n rOO ^F | IN 

ro *O ON

O 00 OO VO

^ fi ^r <s

<S »-" ^

o o o

CO *t it

O IN r- ON

o *' ' «n 

ro ro "^ I"-*-

O CN OO O

f* ^1*

oo >* <<r

32-2

ex

Alfalfa Soybeans 

Oats/Alfalfa Subtotal 

Nitrogen removal by i

| NO | | 1 NO 00

r- ' ' r- ON

ON ON NO

oo oo vo*

« o , , -

""

00 00 1 ? 1 1 1 J*

i oo i <N r- r- r-

' JN ' VO 0 

O^ ON ^ f<y

i^f vo* -^

| O | O 00

rs * rON OO ^ ^^

| | <N <N r-'

| NO r- I NO ON 

r- <N ' oo oo oo

o vo r- o

oo oo ON

| O V0 | 00 M rtf) O OO ;

NO oo

1 O vo I 1 vo O

1 00 ' ' ON 5J-

"". "1 'H

 OO

I O NO* 1 1 1 IN ' '

NO 00 TT

I IN IN I I wS

1 ON ' ' O

NO O I OO t- IN 

ON O VO V) <N VO 

oo ro ^J- <N ON O

 «N 00

 CS

O O | O 00

r- cs ' -<* roo r^ r^ «*j O 

H 3- I ~ ro CN 

 ON ' rj

1

o o

0 M

li

ill 

j!> c § « "§ ^ S

||

: ; i :

OO ON I"- O 

«N «N «O VO

rn * 5J-* vo*

O 0 O 

<N ^J- VO IN

I"-*- OO V} V}

I/I i VO I/I

CvT -T r*f ^*

^^ 10 ON r*^ ^- r~- ^jr- o oo <N

IN ro 'J'

IN

Base flowStorm flowSubtotal Excess nitrogen

65 Water-Resources Investigations Report 93-4069
Other studies have shown that land use within a basin has a direct effect on the water quality within and 

potentially outside the basin. Agricultural activity, along with basin hydrogeology, is believed to have the greatest 

effect on nutrient discharges in surface and ground water in the Lower Susquehanna River Basin (Lietman and others, 

1983; Lloyd Reed, U.S. Geological Survey, written commun., 1992). A comparison of data collected at five sites in 

Pennsylvania-the Bald Eagle Creek site, the Conestoga River, Little Conestoga Creek at Churchtown, Little 

Conestoga Creek at Morgantown, and Young Womans Creek at Renova support this conclusion. Figure 27 and 

table 24 compare nitrogen, phosphorus, and suspended-sediment yields in pounds per acre per year as a function of 

discharge from different basins having different agricultural intensities and hydrogeologic characteristics in the 

Susquehanna River Basin.

Generally, as agricultural activities become more intensive (increase in acres in agriculture and increase in 

animal units) in each basin, nutrient yields increase. Three sites, Little Conestoga at Churchtown, Conestoga River at 

Conestoga, and Little Conestoga near Morgantown, located in the intensively farmed carbonate valleys of Lancaster 

County, have the highest yields for nitrogen, phosphorus, and sediment compared to the less intensively farmed Bald 

Eagle Creek site and the 100 percent forested site at Young Womans Creek near Renova. For example, at Young 

Womans Creek, where agricultural activities are not present, nitrogen yields averaged about 4 (lb/acre)/yr. At Bald 

Eagle Creek, where agricultural activities are moderate to low in intensity, the nitrogen yield averaged 20 (lb/acre)/yr, 

and at Little Conestoga at Churchtown, where agriculture activities are intensive, the nitrogen yield averaged about 

38 (lb/acre)/yr, on the basis of data for the 1986-89 water years and a normal water discharge ratio of one. A water 

discharge ratio of one means normal flow, below normal flow is less than one, and above normal flow would be 

greater than one.

Table 24. Average annual yields for total nitrogen, total phosphorus, and suspended sediment in streamflow

from five basins in the Susquehanna River Basin for the 1986-89 water years

[Drainage area, square miles; yields, pounds per acre per year; manure production, tons per acre of agricultural land]

Basin

Young Womans Creek

near Renova

Bald Eagle Creek

near Fawn Grove

Conestoga River

near Lancaster

Little Conestoga Creek

near Morgantown

Little Conestoga Creek

near Churchtown

_. . Major Drainage , , . underlying 

area . ' e geology

46.2 shale

.43 schist

324 carbonate

1 .42 carbonate

5.82 carbonate

Percent 

agriculture

0

87

63

78

76

Manure 

production8

0

9.45

8.36

19.0

11.8

Nitrogen

4

20

32

26

38

Average yield

Phosphorus

0.2

1.6

2.5

2.5

3.7

Sediment

250

900

1,330

1,500

2,900

8 Manure production data for Conestoga River at Lancaster and Young Womans Creek near Renova is from Hannawald (1989).

Water-Resources Investigations Report 93-4069 66
60

LULU :Q-

.LU 40

20

0<

cc.cc.

0 

0.5 0.6 0.7 O.B O.9 1 1.1 1.2

RATIO OF ANNUAL AND LONG TERM MEAN DISCHARGE

1.3 1.4

o-o:

-JZ

 o 

0.5

J-x- AX0.7 O.B O.9 1 1.1 1.2

RATIO OF ANNUAL AND LONG TERM MEAN DISCHARGE

1.3 1.4

Q. 6,000 

UJ

or

*,000

K

O(O 

LJQ

2,000

o

0.5

LITTLE CONESTOGA CREEK AT CHURCHTOM 

CONESTOGA CREEK AT CONESTOGA 

LITTLE CONESTOGA CREEK AT UORGANTOIN 

 ALO EAGLE CREEK NEAR FAWN GiOVE 

TOUNG VOMANS CREEK NEAR RENOVO

O, X

 x.

0.6 0.7 O.B 0.9 1 1.1 1.2

RATIO OF ANNUAL AND LONG TERM MEAN DISCHARGE

1.3 1.4

Figure 27. Nutrient yield as a function of annual and long-term discharge at four predominately agricultural 

basins and a forested basin (Young Womans Creek near Renovo) in the Susquehanna River Basin 

1986-89 water years.

67 Water-Resources Investigations Report 93-4069
Changes in Random Events

Numerous random events effected both nutrient management and the water quality at the Bald Eagle Creek site 

during the 5-year study. These random events included large precipitation events, drought conditions, severe wind 

damage to crops, changes in animal populations because of disease outbreaks and changes in market demands, and 

other social, economic, and cultural conditions. The effects of large storms or hurricanes on nutrient transport were 

pointed out by Fishel and others (1992). On May 19,1988, and May 6, 1989, more than 3.5 in. of precipitation (fig. 7) 

fell within the Bald Eagle Creek subbasin producing the two largest monthly discharges of nutrients in stormflow 

(table 18). In contrast, precipitation was 51 percent below normal during the 1986 growing season months April 

through September when nutrient discharges in stormflow were virtually nonexistent. Events of this nature have 

substantial effects on water quality by effecting the processes of surface runoff, infiltration, recharge, crop uptake, 

evapotranspiration, and the timing of most farm operations.

Changes in animal populations or the type of animals raised cause associated changes in manure production and 

applications. Because the animal density at Bald Eagle Creek decreased from 0.85 to 0.43 AU/acre, applications of 

nitrogen and phosphorus from manure to the cropland and pasture were reduced 40 and 15 percent, respectively. 

Thus, animal density and nutrient applications to agricultural land are closely associated.

Other events that had undefinable and immeasurable effects on nutrient management and water quality included 

farmer cooperation after changes developed in (1) the economic condition of the agricultural community, (2) health 

of the land owners, and (3) the religious and cultural composition of the community. For example, one landowner 

within the subbasin sold his farm because of economic reasons. The new owner farmed the land by use of more 

traditional methods, which included the use of horse-drawn equipment in place of modern machinery and applied 

only manure fertilizers. A second farmer sold his dairy herd because of personal health conditions. All the farmers 

were hesitant to sign government contracts to implement conservation practices.

SUGGESTIONS FOR FURTHER STUDY

Although nitrogen, phosphorus, and suspended-sediment concentrations and loads did not decrease significantly 

during the 5-year study at Bald Eagle Creek, nutrient reductions totaling 30,920 Ib of nitrogen and 7,170 Ib of 

phosphorus were accomplished. Valuable information was gained about the water quality of surface-water hydrologic 

processes occurring within a small noncarbonate basin in southern York County, Pa.

In any future studies relating water quality to nutrient management, the study should be well designed and 

planned before sampling begins. A longer sampling period (>5 years) may be necessary to assure sampling over a full 

range of hydrologic conditions and allow water quality to reflect agricultural-activity changes. Extremely wet or dry 

periods make accurate interpretation of water-quality data difficult because nutrient-transport processes are controlled 

by precipitation. It is also important that water-quality studies fully incorporate all interactions of surface-water and 

ground-water. Only one specific nutrient-management practice should be tested within a watershed during the study. 

Problems arise with multiple practices occurring simultaneously, because relating the contribution of an individual 

practice to changes in water quality becomes difficult, if not impossible. Finally, future studies need to consider soilnutrient interactions and transformations of nitrogen with changes in water quality.

Reliable land-use data are critical when trying to relate changes in nutrient management to changes in water 

quality. Therefore, a cooperative environment must exist between all federal, state, and local agencies, and the 

farmers. All concerns from project implications should be discussed with the farmers as the need arises. Farmers are 

more likely to participate in the project if they understand the goals, problems, and results of similar studies.

Water-Resources Investigations Report 93-4069 68
SUMMARY

Hydrologic and land-use data were collected at the Bald Eagle Creek watershed in York County, Pa., from 

October 1985 through September 1990 in cooperation with the SRBC and the PaDER Bureau of Land and Water 

Conservation, as part of the USEPA's Chesapeake Bay Program. This report documents and evaluates changes in 

water quality for a 5-year period from October 1985 through September 1990 during implementation of agriculturalmanagement practices in the watershed.

Three small farms in the subbasin have a total acreage of about 275 acres. About 87 percent of the land is 

cropland and pasture. Prior to nutrient management, 33 percent of the cropland was used to produce corn, whereas 

during nutrient management, an average of 22 percent of the cropland was used to produce corn. Dairy farms at the 

site generally rotate crops on a 2-year corn and 3-year alfalfa sequence.

The animal population consists almost exclusively of dairy cattle. Several steer and hogs were raised near the 

water-quality monitoring gage during the final 2 years of the study. A sudden and unplanned decrease in the animal 

population occurred immediately after the onset of nutrient management in 1987, when one of the fanners sold his 

dairy herd. Later, a second fanner sold his farm and the new owner reduced his dairy herd. Thus, the animal density 

decreased from 0.85 AU/acre prior to nutrient management to 0.43 AU/acre during nutrient management.

The total amount of nitrogen and phosphorus applied to cropland and pasture decreased 62 and 61 percent, 

respectively, during the first 2 years of nutrient management. Applications of nitrogen and phosphorus applied were 

made primarily between March and June and were predominately commercial fertilizers. About 82,640 Ib of nitrogen 

and 20,290 Ib of phosphorus were applied to the cropland and pastures prior to nutrient management, and 51,720 Ib of 

nitrogen and 13,120 Ib of phosphorus were applied to cropland and pastures during the 3 years of nutrient 

management. Prior to nutrient management, 50 percent of the nitrogen and 62 percent of the phosphorus applied 

were from commercial fertilizer; during nutrient management, 28 percent of the nitrogen and 50 percent of the 

phosphorus applied were from commercial fertilizer. The reductions in the amounts of nitrogen and phosphorus 

applications resulted from the reductions in animal units and requirements for crops because of the rotation from corn 

to legumes.

Precipitation was 2 percent less than normal during the 5-year study. Prior to nutrient management (October 

1985-September 1987), precipitation was 18 percent less than normal. During nutrient management (October 1987- 

September 1990), precipitation was 8 percent above normal. Annual precipitation ranged from 37 percent less than 

normal in the 1986 water year to 19 percent greater than normal during the 1989 water year. Extreme variations in 

seasonal precipitation were measured during the study. Precipitation during the growing seasons (April through 

September) ranged from 57 percent less than normal in 1986 to 37 percent greater than normal in 1989. Precipitation 

during the nongrowing seasons (October through March) ranged from 18 percent less than normal in 1988 to 

25 percent greater than normal in 1990.

Streamflow was about 35 percent less than normal prior to nutrient management and 3 percent less than normal 

during the first 2 years of nutrient management. Annual mean streamflows were 0.33,0.32,0.58, and 0.42 ft /s for the 

1986-89 water years, respectively. Prior to and during nutrient management, the base flow percentage of the total 

stream discharge was 84 and 54 percent, respectively. Fifty-seven percent of the total measured stormflow for the 4- 

year period (1986-89 water years) was discharged in the 1988 water year. About 24 percent of the total measured 

stormflow was discharged in May 1988 and May 1989. About 31 percent of the measured precipitation during the 

first 4 years of the study was discharged as surface water; the remaining 69 percent was removed as evapotranspiration or remained in ground-water storage.

69 Water-Resources Investigations Report 93-4069
Median concentrations of total nitrogen and dissolved nitrite plus nitrate in base flow increased significantly 

from 4.7 and 4.0 mg/L, respectively, in the 1986 water year, to 6.3 and 5.4 mg/L, respectively, in the 1990 water year. 

Concentrations and discharges of dissolved nitrite plus nitrate in base flow were greatest in February during the 

nongrowing season when base flow was high following prolonged periods of precipitation. Prior to nutrient 

management, about 83 percent of the approximate 5,300 Ib of total nitrogen discharged in base flow was dissolved 

nitrite plus nitrate, whereas, 86 percent of the approximate 5,700 Ib of total nitrogen discharged during nutrient 

management was dissolved nitrite plus nitrate. About 2,180 Ib of total nitrogen were discharged in stormflow prior to 

nutrient management; about 6,120 Ib of total nitrogen were discharged in stormflow during nutrient management. 

Eighty-four percent of the stormflow was sampled during the first 4 years of the study. No significant change was 

detected in concentrations or discharges of total and dissolved ammonia, ammonia plus organic nitrogen, phosphorus, 

or suspended sediment between the prior to and during nutrient-management periods, or between growing and 

nongrowing seasons.

Concentrations of total phosphorus in base flow, unlike concentrations of total nitrogen and dissolved nitrite plus 

nitrate, did not exhibit a seasonal trend. However, loads of phosphorus were more closely associated with base flow 

than were the concentrations of phosphorus. About 117 Ib of total phosphorus were discharged in base flow during 

the first 4 years of the study; 68 percent of the measured phosphorus was dissolved and 50 percent was 

orthophosphorus. About 79 percent of the 1,150 Ib of total phosphorus load discharged in stormflow was measured in 

the first 2 years of the nutrient-management period.

Monthly suspended-sediment concentrations and loads in streamflow were greatest in the growing season 

months of April and May, when the majority of the plowing was done. About 4,550 Ib of sediment were discharged in 

base flow prior to nutrient management, and about 2,860 Ib of sediment were discharged in base flow during nutrient 

management. About 64 percent of the 724,575 Ib of suspended-sediment load was discharged in stormflow during the 

growing seasons.

Concentrations of nutrients in the soil were highly variable. No trends were detected in the concentrations of 

nitrate nitrogen in the soil with respect to season or as a result of reduced nutrient applications. Because some soils 

were less than 36 in. deep in the Bald Eagle Creek subbasin, the total nutrient content of soils at Bald Eagle Creek is 

inherently lower than the nutrient content of soils in other intensively fanned areas being studied at the Brush Run 

subbasin in Adams County and the Conestoga headwaters in Lancaster County. Concentrations of nitrate nitrogen in 

the Bald Eagle Creek Basin were generally uniform throughout the soil column, suggesting that nitrate is highly 

mobile, whereas, phosphorus concentrations consistently were greater in the top 8 in. of the soil. The amount of 

nitrate-nitrogen in the top 4 ft of soil at four field sites ranged from 36 to 135 Ib/acre prior to nutrient management 

and from 21 to 291 Ib/acre during nutrient management. The amount of available phosphorus in the top 4 ft of soil 

ranged from 0.39 to 2.5 Ib/acre prior to nutrient management and 0.73 to 1.7 Ib/acre during nutrient management.

In conclusion, a 7 percent increase in precipitation, a 34 percent reduction in cropland devoted to corn, and a 

37 percent increase in cropland devoted to legumes coincided with a significant increase in base flow concentrations 

and discharges of total nitrogen and dissolved nitrite plus nitrate during nutrient management. Furthermore, a 

49 percent reduction in animal units combined with a 77 and 65 percent reduction in commercial applications of 

nitrogen and phosphorus, respectively, did not result in a favorable detectable change in surface-water quality in the 

3-year nutrient-management monitoring period.

Water-Resources Investigations Report 93-4069 70
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