U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2007-5052

Prepared in cooperation with the

N.J. Department of Environmental Protection and N.J. EcoComplex

Simulation of Surface-Water Conditions in the 

Nontidal Passaic River Basin, New Jersey

Simulation of Surface-Water Conditions 

in the Nontidal Passaic River Basin, 

New Jersey

By Frederick J. Spitz

Prepared in cooperation with the 

N.J. Department of Environmental Protection and 

N.J. EcoComplex

Scientific Investigations Report 2007-5052

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia 2007

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Suggested citation:

Spitz, F.J., 2007, Simulation of surface-water conditions in the nontidal Passaic River Basin, New Jersey: U.S. Geological Survey Scientific Investigations Report 2007-5052, 67 p.

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iii

Contents

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

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................3

Description of Study Area ...................................................................................................................3

Previous Investigations........................................................................................................................4

Surface-Water Flow System........................................................................................................................4

Gaged and Ungaged Mainstem Flows ..............................................................................................4

Gaged, Partial-Record, and Ungaged Flows Along Mainstem .....................................................7

Subbasin Delineation ..................................................................................................................7

Subbasin Flows ............................................................................................................................7

Discharges and Diversions .................................................................................................................8

Simulation of Surface-Water Flow............................................................................................................11

Flow Routing Model............................................................................................................................11

Design. .........................................................................................................................................12

Boundary and Initial Conditions ..............................................................................................18

Quantitative and Qualitative Measures of Model Accuracy..............................................18

Model Sensitivity........................................................................................................................19

Calibration of Flow Model .................................................................................................................19

Ungaged Subbasin Flows.........................................................................................................20

Channel Cross-Section Geometry...........................................................................................20

Low-Flow Conditions (Water Year 2001) ................................................................................28

Validation of Flow Model ...................................................................................................................28

Average-Flow Conditions (Water Year 2000).........................................................................28

Extreme Low-Flow Conditions (Water Year 2002).................................................................29

High-Flow Conditions (Water Year 2003)................................................................................49

Mixing Algorithm at Two Bridges, New Jersey .............................................................................49

Description of Algorithm...........................................................................................................49

Output from Algorithm...............................................................................................................57

Simulation of Water-Quality Transport.....................................................................................................58

Channel Inactive Storage Area ........................................................................................................62

Transport Submodel ...........................................................................................................................62

Design and Boundary Conditions............................................................................................62

Calibration and Validation ........................................................................................................62

Limitations of the Simulation Analysis .....................................................................................................63

Summary........................................................................................................................................................64

Acknowledgments.......................................................................................................................................65

References Cited..........................................................................................................................................65
iv

Figures

1-3. Maps Showing—

1. Location of the Passaic River Basin, New Jersey.........................................................2

2. Streamflow-gaging stations and contributing subbasins in the nontidal Passaic 

River Basin, New Jersey ....................................................................................................5

3. Major discharges and diversions and water-quality sampling stations in the 

nontidal Passaic River Basin, New Jersey .....................................................................9

4-5. Graphs Showing—

4. Major (a) discharge and (b) diversion flows in the nontidal Passaic River Basin, 

New Jersey.........................................................................................................................10

5. Diurnal variation for discharges and diversions in the nontidal Passaic River 

Basin, New Jersey ............................................................................................................11

6. Map showing surface-water model grid of the nontidal Passaic River, New Jersey ....13

7-30. Graphs Showing—

7. Calibrated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 

01388500, Pompton River at Pompton Plains, New Jersey , water year 2001 .........31

8. Calibrated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 

01381500, Whippany River at Morristown, New Jersey , water year 2001 ..............32

9. Calibrated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 

01379500, Passaic River near Chatham, New Jersey, water year 2001....................33

10. Calibrated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 

01381900, Passaic River at Pine Brook, New Jersey, water year 2001.....................34

11. Calibrated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 

01389500, Passaic River at Little Falls, New Jersey, water year 2001 ......................35

12. Calibrated (a) discharge, (b) flow duration, and (c) velocity and depth at station 

01389890, Passaic River at Dundee Dam at Clifton, New Jersey, water year 

2001 ......................................................................................................................................36

13. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 

01388500, Pompton River at Pompton Plains, New Jersey, water year 2000 ..........37

14. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 

01381500, Whippany River at Morristown, New Jersey, water year 2000 ...............38

15. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 

01379500, Passaic River near Chatham, New Jersey, water year 2000....................39

16. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 

01381900, Passaic River at Pine Brook, New Jersey, water year 2000.....................40

17. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 

01389500, Passaic River at Little Falls, New Jersey, water year 2000 ......................41

18. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at station 

01389890, Passaic River at Dundee Dam at Clifton, New Jersey, water year 

2000 ......................................................................................................................................42

19. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 

01388500, Pompton River at Pompton Plains, New Jersey, water year 2002 ..........43

20. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 

01381500, Whippany River at Morristown, New Jersey, water year 2002 ...............44

21. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 

01379500, Passaic River near Chatham, New Jersey, water year 2002....................45
v

22. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 

01381900, Passaic River at Pine Brook, New Jersey, water year 2002.....................46

23. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 

01389500,Passaic River at Little Falls, New Jersey, water year 2002 .......................47

24. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at station 

01389890, Passaic River at Dundee Dam at Clifton, New Jersey, water year 

2002 ......................................................................................................................................48

25. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 

01388500, Pompton River at Pompton Plains, New Jersey, water year 2003 and 

early 2004 ............................................................................................................................50

26. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 

01381500, Whippany River at Morristown, New Jersey, water year 2003 and early 

2004 ......................................................................................................................................51

27. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 

01379500, Passaic River near Chatham, New Jersey, water year 2003 and early 

2004 ......................................................................................................................................52

28. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 

01381900, Passaic River at Pine Brook, New Jersey, water year 2003 and early 

2004 ......................................................................................................................................53

29. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 

01389500, Passaic River at Little Falls, New Jersey, water year 2003 and early 

2004 ......................................................................................................................................54

30. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at station 

01389890, Passaic River at Dundee Dam at Clifton, New Jersey, water year 2003 

and early 2004.....................................................................................................................55

31. Map showing Location of sampling stations and discharge and diversion sites, Two 

 Bridges, New Jersey, and vicinity ..................................................................................56

32-35. Graphs Showing—

32. Intake flow and phosphorus loads in the vicinity of Two Bridges, New Jersey, 

1999-2003.............................................................................................................................57

33. Results of sensitivity analysis on mixing algorithm parameters used in the flow 

model of the nontidal Passaic River, New Jersey, water year 2002 .........................59

34. Simulated sources of water to Wanaque South intake, Two Bridges, New Jersey, 

for (a) water year 2000, (b) water year 2001, (c) water year 2002, and (d) water 

year 2003 and early 2004...................................................................................................60

35. Calibrated dye transport between Two Bridges and Little Falls, New Jersey........63
vi

Tables

1. Streamflow-gaging stations in the nontidal Passaic River Basin, New Jersey ................6

2. Reference information for the surface-water model of the nontidal Passaic River Basin, 

New Jersey..................................................................................................................................14

3. Channel-slope data for the surface-water model of the nontidal Passaic River, New 

Jersey ...........................................................................................................................................17

4. Flow estimates for contributing subbasins in the surface-water model of the nontidal 

Passaic River Basin, New Jersey............................................................................................21

5. Calibrated channel cross-section geometry in the surface-water model of the nontidal 

Passaic River Basin, New Jersey............................................................................................24

6. Model calibration and validation error at gage locations, Passaic River Basin, 

 New Jersey..................................................................................................................................30
vii

Conversion Factors, Datums, and Definitions

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2)

acre 0.004047 square kilometer (km2)

square foot (ft2) 929.0 square centimeter (cm2)

square foot (ft2) 0.09290 square meter (m2)

square mile (mi2) 2.590 square kilometer (km2) 

Volume

gallon (gal) 3.785 liter (L) 

gallon (gal) 0.003785 cubic meter (m3) 

million gallons (Mgal) 3,785 cubic meter (m3)

cubic feet (ft3) 0.02832 cubic meter (m3) 

acre-foot (acre-ft) 1,233 cubic meter (m3)

Flow rate

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

cubic feet per second (ft3/s) 0.02832 cubic meter per second (m3/s)

cubic feet per second per square mile [(ft3/

s)/mi2] 0.01093 cubic meter per second per square kilometer [(m3/s)/km2]

gallon per day (gal/d) 0.003785 cubic meter per day (m3/d)

gallon per day per square mile [(gal/d)/mi2] 0.001461 cubic meter per day per square

kilometer [(m3/d)/km2]

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3/s)

million gallons per day per square mile 

[(Mgal/d)/mi2] 1,461 cubic meter per day per squarekilometer [(m3/d)/km2]

Mass

pound, avoirdupois (lb) 0.4536 kilogram (kg) 

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 

(NGVD 1929).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 

25 °C).

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) 

or micrograms per liter (μg/L).

Simulation of Surface-Water Conditions in the Nontidal 

Passaic River Basin, New Jersey

By Frederick J. Spitz

Abstract

The Passaic River Basin, the third largest drainage basin 

in New Jersey, encompasses 950 mi2 (square miles) in the 

highly urbanized area outside New York City, with a population of 2 million. Water quality in the basin is affected by 

many natural and anthropogenic factors. Nutrient loading to 

the Wanaque Reservoir in the northern part of the basin is 

of particular concern and is caused partly by the diversion 

of water at two downstream intakes that is transferred back 

upstream to refill the reservoir. The larger of these diversions, Wanaque South intake, is on the lower Pompton River 

near Two Bridges, New Jersey. To support the development 

of a Total Maximum Daily Load (TMDL) for nutrients in the 

nontidal part of the basin (805 mi2), a water-quality transport 

model was needed. The U.S. Geological Survey, in cooperation with the New Jersey Department of Environmental 

Protection and New Jersey EcoComplex, developed a flowrouting model to provide the hydraulic inputs to the waterquality model.

The Diffusion Analogy Flow model (DAFLOW) 

described herein was designed for integration with the Water 

Quality Analysis Simulation Program (WASP) watershed 

water-quality model. The flow routing model was used to 

simulate flow in 108 miles of the Passaic River and major 

tributaries. Flow data from U.S. Geological Survey streamflow-gaging stations represent most of the model’s upstream 

boundaries. Other model inputs include estimated flows for 

ungaged tributaries and unchanneled drainage along the mainstem, and reported flows for major point-source discharges 

and diversions. The former flows were calibrated using the 

drainage-area ratio method. The simulation extended over 

a 4+ year period representing a range in flow conditions. 

Simulated channel cross-sectional geometry in the DAFLOW 

model was calibrated using several different approaches by 

adjusting area and top width parameters. The model also was 

calibrated to observed flows for water year 2001 (low flow) at 

five mainstem gaging stations and one station at which flow 

was estimated. The model’s target range was medium to low 

flows--the range of typical intake operations. Simulated flow 

mass balance, hydrographs (flood-wave speed, attenuation, 

and spread), flow-duration curves, and velocity and depth 

values were compared to observed counterparts. Mass balance 

and hydrograph fit were evaluated quantitatively.

Simulation results generally were within the accuracy 

of the flow data at the measurement stations. The model was 

validated to observed flows for water years 2000 (average 

flow), 2002 (extreme low flow), and 2003 (high flow). Results 

for 19 of 20 comparisons indicate average mass-balance and 

model-fit errors of 6.6 and 15.7 percent, respectively, indicating that the model reasonably represents the time variation of 

streamflow in the nontidal Passaic River Basin.

An algorithm (subroutine) also was developed for 

DAFLOW to simulate the hydraulic mixing that occurs near 

the Wanaque South intake upstream from the confluence of 

the Pompton and Passaic Rivers. The intake draws water from 

multiple sources, including effluent from a nearby wastewatertreatment plant, all of which have different phosphorus loads. 

The algorithm determines the proportion of flow from each 

source and operates within a narrow flow range. The equations 

used in the algorithm are based on the theory of diffusion and 

lateral mixing in rivers. Parameters used in the equations were 

estimated from limited available local flow and water-quality 

data. As expected, simulation results for water years 2000, 

2001, and 2003 indicate that most of the water drawn to the 

intake comes from the Pompton River; however, during many 

short periods of low flow and high diversion, particularly in 

water year 2002, entrainment of the other flow sources compensated for the insufficient flow in the Pompton River.

As additional verification of the flow model used in the 

water-quality model, a Branched Lagrangian Transport Model 

(BLTM) was created to simulate historical dye-tracer tests 

done in the 4-mile subreach between Two Bridges and Little 

Falls. Dye decay and longitudinal dispersion were calibrated 

and roughly validated. Concentration mass, time-of-travel, and 

attenuation and spread of the dye cloud were reproduced by 

the submodel. The flow and transport models are considered 

accurate given the indicated limitations.

Introduction

The Passaic River Basin in northeastern New Jersey and 

a small part of southeastern New York (fig. 1) is the third 
Wanaque

Reservoir

Troy

Meadows

Hatfield

Swamp

Great Piece

Meadows

 Boonton

Reservoir

Great

Swamp

Dead

River

Canoe Brook

Peckman River

Singac Brook NEW YORK

NEW JERSEY

Ramapo

Rockaway

Wanaque

Upper Passaic

Lower Passaic

Saddle

Pequannock

Whippany

Pompton

ORANGE

ROCKLAND

SUSSEX

PASSAIC

BERGEN

MORRIS

SOMERSET

UNION

HUDSON

NEW YORK 

ESSEX

RICHMOND

0 25 50 KILOMETERS

0 25 50 MILES

75° 74°

41°

40°

NEW YORK

NEW 

JERSEY Atlantic Ocean

HIGHLANDS

PIEDMONT

Two

Bridges

 Wanaque

South intake

74°35' 74°10'

40°

50'

41°

15'

10 KILOMETERS

0 5 10 MILES

0 5

Basin and name

EXPLANATION

Saddle

Base from U.S. Geological Survey digital line data, 1:24,000

Universal Transverse Mercator Projection, Zone 18, NAD83

Dundee Dam

Little Falls

Great Falls

STUDY 

AREA

Figure 1. Location of the Passaic River Basin, New Jersey. (Dundee Dam divides nontidal from tidal part of basin.)

2 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey
largest drainage basin in New Jersey (950 mi2

), most of which 

is in the highly urbanized area outside New York City. Water 

quality in the basin is affected by many factors, including 

complex river-system hydraulics, many point-source discharges and diversions, nonpoint-source runoff from mixed 

land uses, varying geology, river interaction with wetlands and 

ground water, and water use.

The New Jersey Department of Environmental Protection (NJDEP), in cooperation with the U.S. Environmental 

Protection Agency (USEPA), has mandated Total Maximum 

Daily Load (TMDL) requirements for nutrients, mainly total 

phosphorus, in the nontidal part of the basin (N.J. Department 

of Environmental Protection, 2001; Cenno and Hirst, 2005). 

TMDLs establish the load of contaminants a water body can 

receive without violating applicable water-quality standards. 

Of particular concern in the Passaic River Basin is eutrophication of the Wanaque Reservoir (fig. 1), a water-supply reservoir in the 90-mi2

 Wanaque River subbasin. The Wanaque 

South intake, at the downstream end of the Pompton River, 

diverts water back upstream to the reservoir, thereby contributing additional phosphorus to the reservoir. (The reservoir also 

receives water diverted from Pompton Lake on the Ramapo 

River.) Diversion rates are flow-dependent: water typically is 

not diverted at high flows, when the reservoir storage commonly is near capacity or spilling, and diversion is limited at 

very low flows, when nearby passing-flow requirements must 

be met. Therefore, nutrient transfer usually occurs only during 

medium to low flows.

Treated effluent from Two Bridges Sewerage Authority discharges to the Pompton River just upstream from the 

intake. Nonpoint-source flows in the basin also contribute 

nutrient loads. Because streamflows, loadings, and water-quality processes are transient, advanced techniques are required to 

evaluate these issues. Accordingly, the NJDEP, in cooperation 

with local watershed advisory committees, determined that a 

transient water-quality model was needed to support TMDL 

development efforts. A necessary first step in the development 

of the water-quality transport model of the watershed was the 

development of a flow model of the river. The flow model 

provides a modeling framework, predictive representation 

of the streamflow hydraulics, and the hydraulic inputs to the 

water-quality model. Time-of-travel information important 

for dealing with accidental or intentional spills of soluble 

contaminants upstream from surface-water intakes also can be 

approximated from the dye-tracer data used in this study.

Therefore, the U.S. Geological Survey (USGS), in 

cooperation with the NJDEP and New Jersey EcoComplex 

(Rutgers University’s Environmental Research and Extension Center, or NJEC), developed a Diffusion Analogy Flow 

model (DAFLOW) to simulate flows in the nontidal Passaic 

River Basin and for integration with a Water Quality Analysis 

Simulation Program (WASP) water-quality model. TRC Omni 

Environmental Corp. (TRC Omni) in Princeton, N.J., developed the WASP model. The water-quality model uses the flow 

model as a basis for establishing a model network (grid) and 

to obtain information on mass transport and cross-sectional 

geometric characteristics throughout the basin.

Purpose and Scope

This report describes a transient flow-routing model 

developed to provide the hydraulic inputs needed for nutrient 

TMDL water-quality modeling of the nontidal Passaic River 

Basin. The flow model provides a time-series of unsteady 

streamflows as input to a watershed water-quality model being 

developed by TRC Omni. The model provides predictive capability with respect to the hydraulics of the basin that can be 

used in future simulations. It simulates mixing near Wanaque 

South intake because one of the main objectives of the TMDL 

is to address the effect of phosphorus loads contributed from 

the intake on the quality of water in the Wanaque Reservoir.

The report documents the development, calibration, and 

validation of the flow model, which simulates river-system 

hydraulics over the nontidal Passaic River Basin domain, 

as well as the development of continuous flow data for all 

model boundaries, calibration/validation locations, subbasins 

along the mainstem, and major point sources and sinks. The 

simulation period (water years 2000-03) represents a range 

of streamflow conditions, although the focus is on moderate 

streamflows. The flow model considers constituent transport 

in addition to flow routing, as it is designed ultimately to interface with and address requirements of the water-quality model 

(for example, inclusion of sampling stations).

Description of Study Area

The Passaic River Basin lies in the Piedmont and Highlands Physiographic Provinces of northeastern New Jersey and 

southeastern New York and contains complex and diverse land 

uses. Approximately half of the basin lies in the Highlands 

(northwest) and the other half lies in the Piedmont (southeast). 

The river and its major tributaries drain all of Passaic County, 

and parts of Morris, Somerset, Union, Essex, Hudson, Sussex, 

and Bergen Counties in New Jersey; and parts of Orange and 

Rockland Counties in New York (fig. 1). The population of 

this area is approximately 2 million.

The six major mainstem tributaries to the Passaic River 

in the nontidal Passaic River Basin are the Pequannock, 

Wanaque, Ramapo, Pompton, Rockaway, and Whippany Rivers. A seventh tributary, Saddle River, drains into the Passaic 

River below Clifton, outside the study area. Many smaller 

streams drain into these major tributaries. Although the Passaic River ultimately flows southeast into Newark Bay, this 

study considered only the drainage area upstream from Clifton 

(805 mi2), which excludes the tidal reaches downstream from 

Dundee Dam. Recorded flows at Little Falls (762 mi2) averaged 1,132 ft3

/s over the 105-year period of record, but can 

vary widely, as indicated by flows ranging from 37 to 11,300 

ft3/s during August and September 1999. Large wetlands, 

including Troy Meadows, Hatfield Swamp, and Great Piece 

Introduction 3
Meadows, are present along the mainstem river and tributaries. The river channel slope is very flat (0.5-1 ft/mi) throughout these areas. Many reservoirs are located within the basin. 

Ground water is withdrawn along some reaches of the mainstem river and tributaries (for example, Canoe Brook).

Previous Investigations

Anderson and Faust (1973) provided information on 

water quality and streamflow in the Passaic River upstream 

from Little Falls, defined relations among various hydrologic 

characteristics, and evaluated long-term water-quality trends. 

NJDEP (1987) developed a steady-state river water-quality 

model using the USEPA’s QUAL2E computer program 

(Brown and Barnwell, 1987) to assess the effect of pointsource discharges on the quality of water in the mainstem 

and to ensure the maintenance of water-quality standards in 

affected areas. The U.S. Army Corps of Engineers (U.S. Army 

Corps of Engineers, 1995) regularly updates flood studies 

of the basin. Storck and Nawyn (2001) reconstructed natural 

streamflow records in the basin to account for the effects of 

anthropogenic activities.

Phosphorus loading to the Wanaque Reservoir by 

instream sources was evaluated by Rosensteel and Strom 

(1991). NJDEP’s current TMDL development process is 

conducted in cooperation with the USGS and TRC Omni 

(2004, 2007) for the nontidal Passaic River Basin, Najarian 

Associates (2005) for Wanaque Reservoir, and Quantitative 

Environmental Analysis (2005) for Pompton Lake. Work done 

by Najarian Associates includes a river simulation based on a 

simple mass-balance model for phosphorus loads.

Surface-Water Flow System

Water enters the mainstem in several ways, including 

through tributary runoff, unchanneled runoff, ground-water 

base flow (nonpoint-source flows), and point-source discharges. Water is withdrawn from the mainstem and it’s tributaries by diversion. Streamflow consists of both surface- and 

ground-water components. Separation of the surface-water and 

ground-water components is not necessary for the flow model. 

To satisfy the needs of the water-quality model, continuous 

flows for these components of the surface-water system must 

be determined at model boundaries and at selected points 

(model nodes) along the mainstem by measurement or estimation.

Gaged and Ungaged Mainstem Flows

Stream stage is monitored continuously at USGS streamflow-gaging stations. Continuous streamflow is then computed 

for each station from the stage data using a stage-discharge 

rating curve developed by relating discharge measurements 

at each station to stream stage at the time the discharge was 

measured. The accuracy of continuous-flow records at gaging 

stations can range from excellent (within 5 percent of actual 

values) to poor (more than 15 percent from actual values). 

Gage accuracy can change from year to year and, therefore, 

can affect computations of discharge per square mile of drainage area. USGS streamflow-gaging stations are identified 

by numbers that consist of a two-digit major-drainage-basin 

number followed by a six-digit downstream-order number. 

Gages relevant to this study are shown in figure 2 and listed in 

table 1.

The six USGS streamflow-gaging stations that served as 

model boundaries for this study are 01382500 (Pequannock 

River at Macopin Intake Dam), 01387000 (Wanaque River 

at Wanaque), 01388000 (Ramapo River at Pompton Lakes), 

01381000 (Rockaway River below reservoir at Boonton), 

01381400 (Whippany River near Morristown), and 01379000 

(Passaic River near Millington). The accuracy of these gages 

ranged from 10 to 20 percent for water years 2000-03 (Reed 

and others, 2001-04).

At certain model boundaries, no gaging station is present 

and flows must be estimated; these include the Pequannock 

River, Dead River, Singac Brook, and Peckman River (fig. 1). 

The gage on the Pequannock River lies upstream from the 

model boundary, which is located at the site of a former gage 

(01382800). Equation 1 (below) is used to estimate flow at 

the boundary and includes the ratio of the drainage areas of 

the intervening area (20.2 mi2) to the index-gage subbasin 

(19.1 mi2), as well as coefficients C1 and C2. Coefficient C1 

is applied to shift the entire hydrograph by some amount, 

whereas coefficient C2 is applied to shift the low-flow value 

by some amount. Equations for the boundaries at the Dead 

River, Singac Brook, and Peckman River, all of which have no 

upstream gage at the model boundary, also are shown below. 

The variable Q represents flow in these equations:

Q01382800 = Q01382500 + C1 * 1.06 * Q01384500 + C2, (1)

QDead = C1 * 0.24 * Q01379000 + C2, (2)

QSingac = C1 * 0.60 * Q01381400 + C2, (3)

and

QPeckman = C1 * 0.13 * Q01390500 + C2. (4)

The six USGS streamflow-gaging stations (fig. 2) of 

importance in model calibration and validation are 01388500 

(Pompton River at Pompton Plains), 01381500 (Whippany 

River at Morristown), 01381800 (Whippany River near Pine 

Brook), 01379500 (Passaic River near Chatham), 01381900 

(Passaic River at Pine Brook), and 01389500 (Passaic River 

at Little Falls). The accuracy of measurements at these 

gages ranged from 10 to 20 percent for water years 2000-03 

4 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey
5-6

7-14

7-3

7-11

10-1

6-3

12-2

2-6

17-6

14-1

11-19

17-4

5-7

2-2

11-20

11-2

10-4

11-10

6-6

17-7

7-5

7-10

11-26

11-22

16-1

11-7

3-3

17-10

9-2

16-3

5-4

7-8

12-7

17-2

12-3

12-6

12-5

11-15

15-5

15-2

4-3

6-5

16-6

12-8

5-8

7-4

7-13

17-11

2-4

17-9

15-3

5-5

16-5

11-5

7-15

15-8

14-3

6-8

8-2

15-4

11-16

11-14

11-24

2-5

2-8

6-4

12-9

17-8

7-9

5-3

11-25

2-7

7-6

10-6

13-2

17-5

17-3

12-4

3-2

11-6

15-7

6-7

NEW YORK

NEW JERSEY

MORRIS

PASSAIC

ESSEX

SUSSEX

UNION

BERGEN

SOMERSET

HUDSON

01391500

01390500

01389890

01388500

01388000

01387000

01384500

01383500

01382800

01382500

01381900

01381800

01381400

01381000

01379773

01379530

01379500

01379000

01381500

01389005

01389500

EXPLANATION

Contributing subbasin and 

number--See table 4

Model extent

Streamflow-gaging station 

and number--See table 1 

0 5 10 MILES

0 5 10 KILOMETERS

41°

40°

45'

74°30' 74°15'

01381400

7-9

Base from U.S. Geological Survey digital line data, 1:24,000

Universal Transverse Mercator Projection, Zone 18, NAD83

Figure 2. Streamflow-gaging stations and contributing subbasins in the nontidal Passaic River Basin, New Jersey.

Surface-Water Flow System 5
(Reed and others, 2001-04). Records for stations 01388500, 

01381500, 01379500, and 01389500 are considered accurate. 

Station 01381800 has a short period of record (table 1), is 

adjacent to wetlands, and is subject to backwater conditions 

originating at the confluence of the Pompton and Passaic Rivers; station 01381900 is affected similarly by wetlands and 

backwater. The effect of backwater conditions at these gages is 

apparent in the delayed hydrograph recession and reduces the 

accuracy of the gage records. Therefore, these two gages are 

not considered accurate for model-calibration purposes.

No gage exists at the model outlet, Passaic River at 

Dundee Dam at Clifton, although a low-flow site (01389890) 

is present there. Virtually no other flow data are available for 

the river downstream from Little Falls. In an effort to develop 

a rating curve for this location, the USGS measured discharge 

10 times during the summer of 2004, but no rating curve was 

developed; continuous stage data recorded at this location for 

the past several years by United Water New Jersey are inadequate for developing a continuous streamflow record. Therefore, discharge was estimated (R.D. Schopp, U.S. Geological 

Survey, written commun., 2004), by combining discharge at 

Passaic River at Little Falls (01389500) with drainage-areaadjusted discharge at nearby Saddle River at Lodi (01391500), 

which was selected as the index gage. Index gages typically 

are selected from streams having similar drainage-basin and 

other characteristics. Hydrologic characteristics of the Saddle 

River Basin are thought to be similar to those of the drainage area of the Passaic River between Little Falls and ClifTable 1. Streamflow-gaging stations in the nontidal Passaic River Basin, New Jersey.

[mi2, square miles; ft3/s; cubic feet per second; ---, not available or not applicable]

Station number1 Station name Drainage 

area (mi2)

Period of 

record

Discharge2

((ft3/s)/mi2)

Boundary gages

01382800 Pequannock River at Riverdale 83.9 1993-97 ---

01387000 Wanaque River at Wanaque 90.4 1912-15, 1919- 0.4

01388000 Ramapo River at Pompton Lakes 160.0 1921- 1.6

01381000 Rockaway River below reservoir, at Boonton 119.0 1949- 1.1

01381400 Whippany River near Morristown 14.0 1995- 1.6

01379000 Passaic River near Millington 55.4 1903-06, 1921- 1.3

Downstream gages

01388500 Pompton River at Pompton Plains 355.0 1903-04, 1940- 1.3

01381500 Whippany River at Morristown 29.4 1921- 1.7

01381800 Whippany River near Pine Brook 68.5 1992- 2.0

01379500 Passaic River near Chatham 100.0 1903-11, 1937- 1.5

01381900 Passaic River at Pine Brook 349.0 1979- 1.6

01389500 Passaic River at Little Falls 762.0 1897- 1.1

01389890 Passaic River at Dundee Dam at Clifton3 805.0 --- ---

Index/other gages

01379773 Green Pond Brook at Picatinny Arsenal 7.65 1982- 1.5

01382500 Pequannock River at Macopin Intake Dam 63.7 1922-90, 1992- 0.6

01383500 Wanaque River at Awosting 27.1 1919- 1.8

01384500 Ringwood Creek near Wanaque 19.1 1934-78, 1985- 1.6

01379530 Canoe Brook near Summit4 11.0 1982- 1.0

01389005 Passaic River below Pompton River at Two Bridges5 734.0 1988- ---

01390500 Saddle River at Ridgewood 21.6 1954-74, 1977- 1.4

01391500 Saddle River at Lodi 54.6 1923- 1.8

1 Locations shown in figure 2.

2

 For water years 2000-03.

3 Miscellaneous station.

4 Tributary gaging station.

5 Unpublished slope (stage only) station. 

6 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey
ton. Like the Passaic River between Little Falls and Clifton, 

flow at Saddle River at Lodi is affected by both point-source 

discharges and diversions. This index gage is also best for 

estimating the intervening discharge because of its proximity 

and the similar size of its drainage basin. The equation used to 

estimate flow, accounting for the ratio of the drainage area of 

the intervening area (43 mi2) to the drainage area of the indexgage subbasin (54.6 mi2

), is

Q01389890 = Q01389500 + 0.788 * Q01391500. (5)

Estimated flows for the Passaic River at Dundee Dam at Clifton compared favorably with discharge measurements made 

during the summer of 2004.

Minimum passing-flow requirements for streams have 

been mandated by the NJDEP to protect flow quantity and 

quality and stream ecology. Passing flows for reservoir 

releases have been set at the Wanaque River downstream from 

Wanaque Reservoir (15.5 ft3/s; 10 Mgal/d) and the Rockaway 

River downstream from Boonton Reservoir (12.2 ft3/s; 7.9 

Mgal/d). Passing flows for pumped storage have been set 

at Ramapo River at Pompton Lakes (61.9 ft3/s; 40 Mgal/d); 

Pompton River at Pompton Plains (136 ft3/s; 88 Mgal/d); Passaic River at Chatham (116 ft3

/s; 75 Mgal/d); Passaic River 

at Two Bridges (143 ft3/s; 92.6 Mgal/d); and Passaic River 

at Little Falls (27.2 ft3/s; 17.6 Mgal/d). Passing flows at the 

last two stations depend on the operation of Wanaque South 

intake. A passing flow for hydroelectric use that varies with 

season and time of day has been set at Passaic River at Great 

Falls at Paterson (50.0-200 ft3/s; 32.3-129.3 Mgal/d). A passing flow that varies with the stage of Dundee Lake has been 

set at Passaic River at Dundee Dam at Clifton (outflow equals 

inflow).

Gaged, Partial-Record, and Ungaged Flows 

Along Mainstem

Tributary and unchanneled drainage from subbasins 

along the mainstem increases mainstem flow. Determination 

of drainage area and flow for these subbasins is described 

below.

Subbasin Delineation

Before flows at selected points along the mainstem can 

be determined, drainage areas along the mainstem must be 

defined. The methodology used by TRC Omni to define these 

subbasins (fig. 2) consisted of combining an existing NJDEP 

geographic information system (GIS) subbasin layer with 

subbasins delineated automatically using GIS routines. The 

NJDEP data are based on 14-digit hydrologic unit codes, or 

HUC14s, for subbasin boundaries (Ellis and Price, 1995; N.J. 

Department of Environmental Protection, 1996).

Subbasins were delineated for selected points by using 

GIS routines and a digital elevation model (DEM). The 

ArcView Spatial Analyst extension AVSWAT2000 was chosen 

for the delineation of drainage areas for the selected points. 

The extension allows digitized streams to be defined as preferential flow paths, leading to more accurate subbasin delineation. The methodology for subbasin delineation was divided 

into three main steps.

The first step was performed using AVSWAT2000 and a 

10-meter-resolution DEM. The mainstem was used to define 

preferential drainage paths and subbasins were automatically delineated for selected points along the mainstem. The 

preferential drainage paths were a line shapefile derived from 

county stream layers. A GIS point shapefile contained the 

location of selected points along the mainstem. DEMs from 

NJDEP Watershed Management Areas 3 (Pompton, Pequannock, Wanaque, and Ramapo Rivers), 4 (lower Passaic River 

and Saddle River), and 6 (upper Passaic River and Whippany 

and Rockaway Rivers) were merged to form a single DEM, 

which comprised the spatial extent of the entire nontidal Passaic River Basin.

The second step consisted of comparing the automatically delineated subbasin boundaries for selected points with 

existing subbasin boundaries by overlaying the drainage areas 

delineated using AVSWAT2000 on the existing HUC14 coverage. There was good agreement between the automatically 

delineated areas and the HUC14s; however, because automatic 

delineation is based on gridded data, the boundaries were not 

as smooth as for the HUC14s. In order to resolve this discrepancy, the HUC14 coverage was edited manually to incorporate 

the new automatically delineated subbasins. This process 

increased the resolution of the HUC14 coverage by adding 

new subbasin boundaries.

The third step consisted of aggregating multiple subbasins that drain to a single point, assigning a unique identifier 

to the subbasins, and computing the area. This process was 

performed using the county stream layers as a basis. Large 

subbasins may include more than one HUC14 drainage area. 

Drainage areas for subbasins 1-1 and 6-1 were modified to be 

consistent with USGS delineations. A total of 111 subbasins 

with a combined area of 286.7 mi2 were delineated at the 

resolution needed for the model of the nontidal Passaic River 

Basin.

Subbasin Flows

There is only one tributary gaging station in the study 

area, Canoe Brook near Summit (01379530). Partial-record 

stations exist on a number of other tributaries; however, many 

drainage areas along the mainstem are ungaged. A simple 

approach for estimating ungaged subbasin flows was needed. 

Three methods were considered for estimating continuous 

flows for tributaries and unchanneled drainage areas. To assess 

the accuracy of a particular method, total flow mass balance 

per square mile of aggregate drainage area was computed for 

gaging stations on the mainstem. (Flow at gages was time 

lagged, as appropriate, to account for time of concentration.) 

Surface-Water Flow System 7
The general mass-balance equation is the summation of all 

major inputs and outputs upstream from a particular gage:

 Qdownstream gage - Qupstream gage - Qtributaries - Qdrainage areas - (6)

 Qdischarge + Qdiversion = 0. 

 

The first method involved estimating flows at partialrecord stations using individual measurements and correlation 

and MOVE.1 regression (Hirsch, 1982) with nearby index 

gaging stations. Computations of total flow mass balance 

made using this method indicated that subbasin flows were 

underestimated, likely because many of the partial-record 

measurements were made at low-flow sites, which biases 

results and reduces the accuracy at higher flows.

The second method involved using simulated flows from 

an existing watershed model that included the study area. This 

TOPMODEL application (Kennen and others, 2007) inputs 

precipitation, temperature, ground-water withdrawals, landsurface elevation, and land-surface cover (pervious/impervious) and outputs daily discharges for HUC14 subbasins. 

Unfortunately, the TOPMODEL simulation did not cover the 

entire period of the flow model used in this study, so statistical 

relations between TOPMODEL flows and index-gage flows 

were used to extend the TOPMODEL results in time. Flows 

for appropriate TOPMODEL subbasins were compared to 

flows for 13 index gaging stations using 30 years of record. 

For example, for rank correlation, the same percentile rank of 

the best-correlated index-gage flow on that date over the 30 

years was applied to the TOPMODEL subbasin flow. Computations of total flow mass balance made using this method 

indicated that subbasin flows were both under- and overestimated. Better results likely would have been obtained if the 

TOPMODEL period had covered the entire period of the flow 

model.

The third method involved estimating flows for ungaged 

subbasins without partial-record measurements using a drainage-area ratio equation (Perry and others, 2004, p. 18; Sauer, 

2002, p. 81; Singh, 1992, p. 86), which determines flows for 

ungaged subbasins based on flows for comparable gaged subbasins. The method is based on the generally high correlation 

between discharge and drainage area. The following equation was used to estimate flow for each of the 111 subbasins 

(excluding Canoe Brook) and includes coefficients that can be 

adjusted to improve the total flow mass balance:

Qsb = C1 * 

Asb

Aidx

Qidx + C2,

C3

(7)

where 

Qsb = discharge for subbasin,

Asb = drainage area for subbasin,

Aidx = drainage area for index gage,

Qidx = discharge at index gage,

C1 = multiplicative coefficient,

C2 = additive (or subtractive), 

and

C3 = exponential coefficient.

Coefficients C1 and C2 were assumed to be constant for 

all subbasins draining to a particular branch for practical reasons. Coefficient C3 was assumed to be 1.0; this coefficient is 

less important when the drainage areas of subbasins and index 

gages are of comparable size than when they are different, 

although differences in underlying geology could still be a factor. A drainage-area ratio in a range from 0.1 to 2.3 was used, 

which is considered acceptable (for example, Ries and Friesz, 

2000, p. 14). Index gages and coefficients were determined 

during model calibration.

Discharges and Diversions

Discharge and diversion data for October 1999 to 

November 2003 were collected by both USGS and TRC 

Omni. Most data were obtained directly from the facility but, when this was not possible, data were derived from 

NJDEP databases (New Jersey Pollutant Discharge Elimination System Discharge Monitoring Reports, Bureau of Water 

Allocation Public Water Supply Diversion Reports). The 

latter NJDEP data were obtained from a provisional New 

Jersey Water-Transfer database (Domber and Hoffman, 2004). 

(Limitations associated with the supplemental discharge and 

diversion data are available from NJDEP in Trenton, N.J.) 

Daily flows obtained in units of million gallons per day were 

converted to cubic feet per second (1 Mgal/d equals 1.55 ft3/s).

There are 25 major point-source discharges and 5 major 

diversions in the nontidal Passaic River Basin (fig. 3). Discharges and diversions are associated with both municipal 

and industrial facilities. Flows for most of these facilities 

(figs. 4a-b) exceed 1 ft3/s. The Wanaque South intake represents a combined diversion by North Jersey District Water 

Supply Commission (which also supplies United Water New 

Jersey) and Passaic Valley Water Commission. Diversions 

by Marcal Paper, Garden State Paper, and Prime Energy (all 

pertaining to BWA permit number 4006PS) near Passaic River 

at Dundee Dam at Clifton were not included in the model 

because of incomplete data and the expected small effect on 

the water-quality model.

Values of diurnal variations in discharge and diversion 

flows are required for modeling purposes (fig. 5). These variations are caused primarily by patterns of water use; for some 

large diverters, energy costs also play a role. Diurnal variation for North Jersey District Water Supply Commission at 

Wanaque South for water years 2002 and 2003 was based on 

the average diurnal variation for the 2 previous water years. 

Diurnal variation for diversions was based on the limited data 

obtained from each facility. Because hourly data could not be 

obtained for most dischargers, diurnal variation was assumed 

to be similar to that for Livingston Water Pollution Control 

Facility, which was based on limited data. This assumption 

ignores differences in facility size, equipment, operation, and 

other characteristics.

8 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey
NEW YORK

NEW JERSEY

MORRIS

PASSAIC

ESSEX

SUSSEX

UNION

BERGEN

SOMERSET

HUDSON

PA2

PK1 R01 PO3

PO2

PO1

PA6 PA7

PE1

WI3

PE2

WA2

WA1

RA3

PA5

PA3

RO2

WI2

WI1

DR1

PA9

PA8 PA11

PA10

Verona

Hanover

Cedar Grove

Caldwell

Long Hill

Warren 

Stage V

Livingston Morristown

Warren 

Stage IV

Reheis Chemical

Chatham Hill

Florham Park

Pompton Lakes

Wanaque Valley

New Providence

Berkeley Heights

Morris Butterworth

Rockaway Valley 

Parsippany-Troy 

Hills

Wayne Two Bridges

Chatham Glen

Warren Stage I-ll

Madison-Chatham

Bernards

Point View/Passaic Valley 

PA4

Wanaque South/North 

Jersey District and Passaic 

Valley

Little Falls/Passaic Valley

New Jersey 

American

0 5 10 MILES

0 5 10 KILOMETERS

41°

40°

45'

74°30' 74°15'

EXPLANATION

Model extent

Discharge and name

Diversion and name

Water-quality sampling 

station and name

PA3

Wayne

New Jersey 

American

Base from U.S. Geological Survey digital line data, 1:24,000

Universal Transverse Mercator Projection, Zone 18, NAD83

Figure 3. Major discharges and diversions and water-quality sampling stations in the nontidal Passaic River Basin, New Jersey.

Surface-Water Flow System 9
Wanaque Valley

Pompton Lakes

Two Bridges

Rockaway Valley

Morris Butterworth

Morristown

Hanover

Parsippany-Troy Hills

Bernards

Warren Stage V

Warren Stage IV

Long Hill

Warren Stage I-II

Berkeley Heights

Reheis Chemical

Chatham Hill

New Providence

Chatham Glen

Madison-Chatham

Florham Park

Livingston

Caldwell

Wayne

Verona

Cedar Grove

2003-04

AVERAGE FLOW, IN CUBIC FEET PER SECOND

Point View/Passaic Valley

Wanaque South/North Jersey District

Wanaque South/Passaic Valley

New Jersey American

Little Falls/Passaic Valley

2002

2001

2000

25

20

15

10

5

0

0

-25

-50

-75

-100

-125

AVERAGE FLOW, IN CUBIC FEET PER SECOND

2003-04

2002

2001

2000

(a)

(b)

WATER YEAR

DIVERSION

DISCHARGE

WATER YEAR

Figure 4. Major (a) discharge and (b) diversion flows in the nontidal Passaic River Basin, New Jersey. (Data obtained from respective 

facilities.)

10 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey
Simulation of Surface-Water Flow

Water years 2000 through 2003 were selected for simulation of surface-water flow conditions in the nontidal Passaic 

River Basin. A water year extends from October 1 through 

September 30 so as to not separate winter stormflows between 

years, and is designated by the calendar year in which it 

ends. October and November 2003 (in water year 2004) were 

simulated with water year 2003 to include the entire period 

of the water-quality model. These recent years were selected 

because they cover a broad range of flow conditions, coincide 

with the timeframe of the water-quality model, and avoid the 

potential difficulties inherent in obtaining historical discharge 

and diversion flow data. On the basis of combined data from 

12 gaging stations in the study area, discharge averaged 254 

ft3/s in water year 2000, 222 ft3/s in water year 2001, 74.7 ft3/s 

in water year 2002, and 380 ft3/s in water year 2003, compared 

to 273 ft3/s during the periods of record (Reed and others, 

2001-04).

Flow Routing Model

Distributed flow routing is a mathematical procedure for 

predicting the shape and magnitude of a hydrograph at points 

along a watercourse as well as the time variation of water 

speed, cross-sectional area, and top width. The simulation of 

dynamic streamflow movement is based on the St. Venant 

equations, differential equations of one-dimensional unsteady 

flow, which are based on flow mass and momentum balances 

in a one-dimensional open channel (Chapra, 1997). The fully 

dynamic wave form includes all of the mathematical terms 

in these equations, but can be unstable and difficult to solve. 

The dynamic wave form is accurate for a variety of conditions, including mildly sloping channels with slowly rising 

flood waves, backwater, many tributary inflows, and channel 

constrictions.

Various simplifications to the momentum equation enable 

tractable solutions to be achieved; these include the diffusion 

wave (simpler) and kinematic wave (simplest) forms. The diffusion wave form is generally not accurate for channels with 

very flat slopes and rapidly rising flood waves, where flow 

reversals occur, or where the stage-discharge relation is very 

weak. The kinematic wave form has all of the limitations of 

the dynamic wave form plus additional restrictions because it 

ignores the pressure-gradient term as well as the momentum 

term. For example, the kinematic wave form is not accurate 

for backwater conditions or when the product of channel slope 

and time of hydrograph rise is small.

The DAFLOW computer program (Jobson, 1989) was 

selected for streamflow routing. DAFLOW simulates onedimensional flow based on the diffusion wave form of the St. 

0

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

12:00 AM 6:00 AM 12:00 PM 6:00 PM 12:00 AM

HOUR OF DAY

MULTIPLIER

DISCHARGE--all

New Jersey American 

Passaic Valley 

North Jersey District (water 

year 2000)

North Jersey District (water 

year 2001)

DIVERSION

Figure 5. Diurnal variation for discharges and diversions in the nontidal Passaic River Basin, New Jersey.

Simulation of Surface-Water Flow 11
Venant equations. DAFLOW is not fully dynamic because the 

local and convective acceleration terms are omitted from the 

momentum balance equation. The resultant flow equation is

∂Qs

∂t

+ C ∂Qs

∂x

_ Df

∂2Qs

∂x2 = 0, (8)

where

Qs = flow under steady conditions,

C = speed of a moving wave, 

and

Df = wave-dispersion coefficient.

DAFLOW routes flow through a system of interconnected upland channels and divides the system into a series 

of branches that meet at junctions, with each branch divided 

into a series of subreaches. Each subreach is defined by nodes 

representing channel cross sections. DAFLOW is accurate for 

sloped streams, but cannot simulate flow reversals or severe 

backwater conditions. DAFLOW is intensive in terms of 

boundary-condition requirements, which makes it reliable. It is 

practical to apply in a complex river basin because it requires 

a minimum of channel-geometry data. The use of the diffusion 

wave form to simulate flow in the Passaic River Basin is justified on the basis of the large scale of the basin and the lack of 

fine-scale data. For example, the dynamic wave form could 

closely account for channel variations, but collecting detailed 

information on such variations is not practical for such a large 

basin.

DAFLOW uses geomorphic relations to represent channel cross-sectional geometry. Hydraulic-geometry parameters 

are used in the following equations:

A = A0 + A1 * QS

A2, (9)

where

A = cross-sectional area of flow,

A0 = average cross-sectional area at zero flow,

A1 = hydraulic-geometry coefficient for area,

A2 = hydraulic-geometry exponent for area, 

and

 W = W1 * QS

W2, (10)

where 

W = top width of channel,

W1 = hydraulic-geometry coefficient for width,

and

W2 = hydraulic-geometry exponent for width.

These empirical relations are based on geomorphic data 

observed in various locales. Parameter A1 is analogous to 

parameter W1. Parameters A2 and W2 affect the relation of 

area and width to flow. Natural streams contain pools and 

riffles, or inactive and active flow areas, respectively. Parameter A0 applies to the inactive area (dead storage), in contrast 

to parameters A1 and A2, which apply to the active area 

(advective flow). For example, values of parameter A0 typically are large upstream from impoundments, such as Beatties 

Dam at Little Falls. Parameter A0 is not constant with flow; 

it affects constituent transport (decay and dispersion) but not 

flow routing, so it could be assumed to equal zero for flow 

calibration. Because the goal of the TMDL is to address waterquality transport, however, values for parameter A0 must be 

determined.

Design

The flow-model network consists of 17 branches, 18 

junctions (8 internal), and 145 nodes as shown in (fig. 6; 

table 2). The model covers 108 total river miles. Nodes were 

placed at gaging stations, mouths of ungaged tributaries, 

centroids of unchanneled drainage along the mainstem, and 

point-source discharges and diversions. A node also was added 

to represent an off-channel storage boundary condition that 

was required by two of the validation simulations. Additional 

nodes were placed at 25 water-quality sampling stations used 

by the consultant (TRC Omni, 2004, fig. 1). Node density was 

increased near sampling stations. Node distance along each 

branch from the upstream end was determined by applying 

GIS techniques to the 1:24,000 National Hydrography Dataset 

(USGS, 2004), which is accurate to approximately 40 ft, and 

checking results against U.S. Army Corps of Engineers (1995) 

2-ft-contour flood maps.

Channel slope was computed between gages, between 

gages and junctions, and between junctions using floodmap elevation and downstream node distance (table 3). The 

approach was to start simple and add complexity, as needed. 

Elevation data were derived from paper flood maps and distance between node locations was derived by using GIS. Riverbed slopes were estimated using a constant slope between 

endpoints. A branch-averaged slope was the most practical 

design initially, and could be enhanced later, as needed. This 

approach for determining slopes is appropriate for a largescale flow model.

The DAFLOW time-step size was 3 hours; the effect 

of this choice on model sensitivity is discussed farther on. 

According to guidelines suggested in Jobson and Harbaugh 

(1999, p. 6), the approximate minimum slope when using a 

3-hour time step should be 1 ft/mi. The flow model meets this 

requirement in most branches.

The flow model was designed to integrate with the 

water-quality model (TRC Omni, 2007), which uses the Water 

Quality Analysis Simulation Program, or WASP (Wool and 

others, 2001). Therefore, subbasin flows were combined to 

separate nonpoint- from point-source (discharge and diversion) flows. If nonpoint- and point-source flows (which have 

different concentrations) were in the same node, then a flowweighted-concentration boundary condition would be needed 

by WASP for each time step. A maximum 1.5-mi distance 

between DAFLOW nodes was used to minimize the effect of 

lumping nonpoint-source flows at nodes. WASP segments had 

to be created from DAFLOW nodes; network connectivity, 

12 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey
MORRIS

ESSEX

UNION

PASSAIC

BERGEN

SOMERSET

SUSSEX

HUDSON

BERGEN

HUDSON

7

11

5

6

2

16

17

12

9

4

15

10

3

1

14

8

Base from U.S. Geological Survey digital line data, 1:24,000

Universal Transverse Mercator Projection, Zone 18, NAD83

13

14

15

4

13

3 5

17

6

7

16

8

18

10

1

11

2

9

12

2

5

10

2

7

5 4

5

3

5 8

3

4

3

4

5

4

2

2

4

6

6 5

3

3

6

6

7

9

8

3

2

7

4

3

9

4 3

8

7

8

6

3

8

7

4

2

7

8

4

6

5

18

6

8

2

2

5

2

9

8

7

4

3 2 2

11

9

7

6

3

2

6

5

2 3

3

2

10

22

11

11

25

24

16

15

27

26

23

21

20

19 18

14

13

12

10

15

14

13

12

6

2

2

10

3

9 10

17

16

2

5

17

4

40°

45'

41°

74°30' 74°15'

0 5 10 MILES

0 5 10 KILOMETERS

EXPLANATION

Model branch and number

Model junction and number

Model node and number (interior 

nodes only)--See table 2 

13

7

Figure 6. Surface-water model grid of the nontidal Passaic River, New Jersey.

Simulation of Surface-Water Flow 13
Table 2. Reference information for the surface-water model of the nontidal Passaic River Basin, New Jersey.—Continued

[NJPDES, New Jersey Pollutant Discharge Elimination System; BWA, Bureau of Water Allocation; ft3/s, cubic feet per second; up, upstream; down, 

downstream; Ave, Avenue; ---, not available or not applicable; shading within table is designed to separate individual model branches]

River Branch1 Node River 

mile

Gaging 

station

Contributing 

subbasins2

Sampling

station3

Discharge/

diversion4

NJPDES/BWA 

permit number

Pequannock 1 1 0.00 5

01382800 1-1 PE1 --- ---

2 0.88 --- --- --- --- ---

Wanaque 2 1 0.00 01387000 --- WA1 --- ---

2 0.38 --- 2-2, 2-3 --- --- ---

3 1.09 --- --- --- Wanaque Valley NJ0053759

4 1.91 --- 2-4 --- --- ---

5 3.33 --- 2-5 --- --- ---

6 3.66 --- 2-6 --- --- ---

7 4.03 --- 2-7 up WA2 --- ---

8 4.31 --- 2-8 down WA2 --- ---

9 5.19 --- --- --- --- ---

Pequannock 3 1 0.00 --- --- up PE2 --- ---

2 0.19 --- 3-2 down PE2 --- ---

3 0.41 --- 3-3 --- --- ---

4 1.61 --- --- --- --- ---

Ramapo 4 1 0.00 01388000 --- RA3 --- ---

2 0.95 --- --- --- Pompton Lakes NJ0023698

3 1.60 --- 4-2, 4-3 --- --- ---

4 1.93 --- --- --- --- ---

Pompton 5 1 0.00 --- --- --- --- ---

2 0.19 01388500 --- PO1 Point View/Passaic Valley BWA 5099

3 0.41 --- 5-2, 5-3 --- --- ---

4 1.61 --- 5-4 --- --- ---

5 2.41 --- 5-5 --- --- ---

6 3.63 --- 5-6 --- --- ---

7 5.40 --- 5-7 up PO2 --- ---

8 5.64 --- 5-8, 5-9, 5-10 down PO2 --- ---

9 6.44 --- --- --- Two Bridges NJ0029386

10 6.63 --- --- --- Wanaque South Intake6

11 6.87 --- --- PO3 --- ---

Rockaway 6 1 0.00 01381000 --- RO1 --- ---

2 0.20 --- --- --- Rockaway Valley NJ0022349

3 2.16 --- 6-2, 6-3 --- --- ---

4 2.68 --- 6-4 --- --- ---

5 3.24 --- 6-5 --- --- ---

6 4.84 --- 6-6 --- --- ---

7 5.37 --- 6-7 up RO2 --- ---

8 5.59 --- 6-8 down RO2 --- ---

9 6.65 --- --- --- --- ---

Whippany 7 1 0.00 01381400 --- WI1 --- ---

2 1.13 --- --- --- Morris Butterworth NJ0024911

3 1.43

4 1.92 --- 7-2, 7-3 --- --- ---

5 2.22

6 2.72 --- 7-4 --- --- ---

7 4.74 --- 7-5 up WI2 --- ---

8 4.95 01381500 7-6, 7-7 down WI2 --- ---

9 5.17 --- --- --- Morristown NJ0025496

10 6.69 --- 7-8 --- --- ---

11 7.16 --- 7-9 --- --- ---

12 8.00 --- 7-10 --- --- ---

13 10.02 --- 7-11, 7-12 --- --- ---

14 11.05 --- --- --- Hanover NJ0024902

15 12.69 --- 7-13 --- --- ---

14 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey
Table 2. Reference information for the surface-water model of the nontidal Passaic River Basin, New Jersey.—Continued

[NJPDES, New Jersey Pollutant Discharge Elimination System; BWA, Bureau of Water Allocation; ft3/s, cubic feet per second; up, upstream; down, 

downstream; Ave, Avenue; ---, not available or not applicable; shading within table is designed to separate individual model branches]

River Branch1 Node River 

mile

Gaging 

station

Contributing 

subbasins2

Sampling

station3

Discharge/

diversion4

NJPDES/BWA 

permit number

16 14.14 --- 7-14 --- --- ---

17 14.39 01381800 7-15, 7-16 WI3 --- ---

18 14.58 --- --- --- Parsippany-Troy Hills NJ0024970

19 14.80 --- --- --- --- ---

Rockaway 8 1 0.00 --- --- --- --- ---

2 0.94 --- 8-2 --- --- ---

3 1.25 --- --- --- --- ---

Passaic 9 1 0.00 01379000 --- PA2 --- ---

2 1.47 --- 9-2 --- --- ---

3 3.38 --- --- --- --- ---

Dead 10 1 0.00 --- 10-1 --- --- ---

2 0.21 --- --- --- Bernards NJ0022845

3 0.88 --- --- --- Warren Stage V NJ0050369

4 2.20 --- 10-3, 10-4, 10-5 --- --- ---

5 3.44 --- --- --- Warren Stage IV NJ0022497

6 3.60 --- 10-6 up DR1 --- ---

7 3.77 --- --- down DR1 --- ---

Passaic 11 1 0.00 --- --- --- --- ---

2 1.60 --- 11-2, 11-3, 11-4 --- --- ---

3 2.63 --- --- --- Long Hill NJ0024465

4 4.18 --- --- --- Warren Stage I-II NJ0022489

5 4.45 --- 11-5 up PA3 --- ---

6 4.70 --- 11-6 down PA3 --- ---

7 5.71 --- 11-7, 11-8, 11-9 --- --- ---

8 6.83 --- --- --- Berkeley Heights NJ0027961

9 7.41 --- --- --- Reheis Chemical NJ0002551

10 9.19 --- 11-10, 11-11, --- --- ---

11-12, 11-13

11 9.76 --- --- --- Chatham Hill NJ0020281

12 10.08 --- --- --- New Providence7 NJ0021636

13 10.51 --- --- --- Chatham Glen NJ0052256

14 11.50 01379500 11-14 --- --- ---

15 13.39 --- 11-15 up PA4 --- ---

16 13.64 --- 11-16, 11-17, down PA4 --- ---

11-18

17 14.06 --- --- --- New Jersey American BWA 5008

18 14.51 --- --- --- Madison-Chatham NJ0024937

19 15.08 801379530 --- --- --- ---

20 17.17 --- 11-20, 11-21 --- --- ---

21 19.21 --- --- --- Florham Park NJ0025518

22 20.67 --- 11-22, 11-23 --- --- ---

23 22.18 --- --- --- Livingston NJ0024511

24 23.28 --- 11-24 up PA5 --- ---

25 23.58 --- 11-25 down PA5 --- ---

26 24.49 --- 11-26, 11-27 --- --- ---

27 25.03 --- --- --- Caldwell NJ0020427

28 25.52 --- --- --- --- ---

Passaic 12 1 0.00 --- --- --- --- ---

2 1.37 01381900 12-2 --- --- ---

3 4.07 --- 12-3 up PA6 --- ---

4 4.31 --- 12-4 down PA6 --- ---

5 6.33 --- 12-5 --- --- ---

6 8.68 --- 12-6 --- --- ---

7 10.85 --- 12-7 --- --- ---

Simulation of Surface-Water Flow 15
Table 2. Reference information for the surface-water model of the nontidal Passaic River Basin, New Jersey.—Continued

[NJPDES, New Jersey Pollutant Discharge Elimination System; BWA, Bureau of Water Allocation; ft3/s, cubic feet per second; up, upstream; down, 

downstream; Ave, Avenue; ---, not available or not applicable; shading within table is designed to separate individual model branches]

River Branch1 Node River 

mile

Gaging 

station

Contributing 

subbasins2

Sampling

station3

Discharge/

diversion4

NJPDES/BWA 

permit number

9

8 11.90 --- --- --- --- ---

9 12.34 --- 12-8 --- --- ---

10 12.84 --- 12-9 up PA7 --- ---

11 13.05 --- --- down PA7 --- ---

Passaic 13 1 0.00 --- --- --- --- ---

2 0.20 --- 13-2 --- --- ---

3 0.41 --- --- --- --- ---

Singac 14 1 0.00 --- 14-1, 14-2 --- --- ---

2 0.28 --- --- --- Wayne NJ0028002

3 1.71 --- 14-3 --- --- ---

4 1.91 --- --- --- --- ---

Passaic 15 1 0.00 --- --- --- --- ---

2 0.44 --- 15-2 --- --- ---

3 1.49 --- 15-3 up PA8 --- ---

4 1.76 --- 15-4 down PA8 --- ---

5 2.61 --- 15-5, 15-6 --- --- ---

6 2.89 --- --- --- Little Falls/Passaic Valley BWA 5099

7 3.15 --- 15-7 --- --- ---

8 3.44 01389500 15-8 --- --- ---

9 4.44 --- --- --- --- ---

Peckman 16 1 0.00 --- 16-1, 16-2 --- --- ---

2 1.13 --- --- --- Verona NJ0024490

3 1.94 --- 16-3, 16-4 --- --- ---

4 3.09 --- --- --- Cedar Grove NJ0025330

5 4.19 --- 16-5 --- --- ---

6 5.24 --- 16-6 up PK1 --- ---

7 5.53 --- --- down PK1 --- ---

Passaic 17 1 0.00 --- --- --- --- ---

2 1.61 --- 17-2 up PA9 --- ---

3 1.85 --- 17-3 down PA9 --- ---

4 2.85 --- 17-4 --- --- ---

5 3.09 --- 17-5 --- --- ---

6 5.12 --- 17-6 --- --- ---

7 6.24 --- 17-7 --- --- ---

8 7.26 --- 17-8 up PA10 --- ---

9 7.55 --- 17-9 down PA10 --- ---

10 10.11 --- 17-10 --- --- ---

11 10.62 --- 17-11 up PA11 --- ---

12 10.94 1001389890 --- down PA11 --- --- 1 Locations shown in figure 6.

2

 Locations shown in figure 2, except for subbasin 1-1. Subbasins listed in same row are combined in figure 2 using label shown in bold. Flow 

estimates for contributing subbasins listed in table 4.

3

 For water-quality sample collection (TRC Omni Environmental Corp., 2004).

4

 Locations shown in figure 3. Flow is greater than 1 ft3/s.

5

 Includes subbasin flow from intervening drainage area between stations 01382500 and 01382800.

6

 Diversion by North Jersey District (BWA 5329) and Passaic Valley (BWA 5099).

7

 Discharges to Berkeley Heights.

8

 Gage in contributing subbasin 11-19. Includes diversion by New Jersey American (BWA 5008).

9

 Model storage balance reservoir.

10 Miscellaneous site.

16 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey
Table 3. Channel-slope data for the surface-water model of the nontidal Passaic River, New Jersey.

[ft, foot; mi, mile; ---, not available or not applicable]

River Branch1 Node Junction Gagingstation

Elevation2

(ft)

Distance3

(ft)

Distance 

(mi)

Slope

(ft/ft)

Slope

(ft/mi)

Pequannock 1 01382800 195 --- --- --- ---

1 --- 179 4659 0.88 3.434E-03 18.13

Wanaque 2 01387000 222 --- --- --- ---

1 --- 179 27398 5.19 1.569E-03 8.28

Pequannock 3 1 --- 179 --- --- --- ---

2 --- 171 10266 1.94 7.792E-04 4.11

Ramapo 4 01388000 179 --- --- --- ---

2 --- 171 10174 1.93 7.864E-04 4.15

Pompton 5 2 --- 171 --- --- --- ---

2 01388500 169 992 0.19 2.016E-03 10.64

6 --- 161 35267 6.68 2.268E-04 1.20

Rockaway 6 01381000 197 --- --- --- ---

3 --- 168.5 35092 6.65 8.122E-04 4.29

Whippany 7 01381400 317 --- --- --- ---

8 01381500 263 26144 4.95 2.066E-03 10.91

17 01381800 169.5 49823 9.44 1.877E-03 9.91

3 --- 168.5 2162 0.41 4.625E-04 2.44

Rockaway 8 3 --- 168.5 --- --- --- ---

5 --- 167.5 6587 1.25 1.518E-04 0.80

Passaic 9 01379000 219 --- --- --- ---

4 --- 207 17861 3.38 6.719E-04 3.55

Dead 10 15 --- 218 --- --- --- ---

4 --- 207 18792 3.56 5.853E-04 3.09

Passaic 11 4 --- 207 --- --- --- ---

14 01379500 195 60707 11.50 1.977E-04 1.04

5 --- 167.5 74022 14.02 3.715E-04 1.96

Passaic 12 5 --- 167.5 --- --- --- ---

2 01381900 166.5 7245 1.37 1.380E-04 0.73

6 --- 161 61649 11.68 8.922E-05 0.47

Passaic 13 6 --- 161 --- --- --- ---

2 01389005 160 1045 0.20 9.573E-04 5.05

7 --- 159 1107 0.21 9.035E-04 4.77

Singac 14 16 --- 169 --- --- --- ---

7 --- 159 10088 1.91 9.912E-04 5.23

Passaic 15 7 --- 159 --- --- --- ---

8 01389500 123 18181 3.44 1.980E-03 10.45

8 --- 121 5255 1.00 3.806E-04 2.01

Peckman 16 17 --- 340 --- --- --- ---

8 --- 121 29204 5.53 7.499E-03 39.60

Passaic 17 8 --- 121 --- --- --- ---

01389890 27 57744 10.94 1.628E-03 8.60

1 Locations shown in figure 6.

2

 From U.S. Army Corps of Engineers (1995) 2-foot-contour flood maps.

3

 Discussed in “Flow Routing Model Design” section of report.

Simulation of Surface-Water Flow 17
model boundaries, and unit conversions had to be assigned; 

DAFLOW outputs had to be interpolated to a time step used 

in WASP; and a WASP hydrodynamic file had to be written. 

For example, flow output was modified to compute flow volumes in segments. In order to ensure stability and accuracy in 

WASP, the minimum node distance determines the time-step 

size (3 min). The difference in time step between DAFLOW 

and WASP was resolved by linear interpolation. A refined 

version of the DAFLOW model, based on the same input data, 

was developed by TRC Omni (2007). A maximum 1,500-ft 

node distance was used in the refined model to avoid numerical dispersion in WASP.

Boundary and Initial Conditions

Initial estimates for hydraulic-geometry parameters 

were computed by using the DAFLOW accessory computer 

program CEL. CEL is designed to help solve non-linear equations 9 and 10. Option 2 was selected to compute parameters 

from lag times of hydrographs. The Manning equation, which 

empirically relates flow resistance to channel characteristics, 

is used in CEL. A Manning’s roughness coefficient (n) of 

0.05 was input based on average channel characteristics. The 

assignment of one Manning’s roughness coefficient for the 

entire Passaic River Basin is reasonable because it is not a 

model input and is used only to generate initial estimates of 

hydraulic-geometry parameters prior to model calibration. 

Other inputs to CEL include branch-averaged top width from 

USGS streamflow measurements at gaging stations. Because 

only wading measurements were used, results obtained with 

CEL may be underestimated.

Flow time series for boundary gaging stations, tributaries 

and unchanneled drainage along the mainstem, and pointsource discharges and diversions were input to the model 

through 112 boundary conditions. These individual time series 

comprise most of the DAFLOW input file. Because upstream 

gaging stations do not exist on branches 10, 14, and 16 (fig. 6), 

upstream flows had to be estimated for these branches using 

the drainage-area ratio method. Initial conditions for flow 

were chosen to be consistent with observed flows at gages at 

the start of a simulation. The duration of initial conditions was 

less than 2 days in most branches.

Quantitative and Qualitative Measures of Model 

Accuracy

Flow calibration and validation were evaluated both 

qualitatively and quantitatively. Qualitative calibration and 

validation were done visually by comparing observed and 

simulated hydrographs to evaluate flood-wave speed and 

attenuation and spread. (Attenuation/spread affects the diffusion and roundness of peaks and troughs.) Quantitative calibration and validation were done by computing various mean 

and relative error measures for the water year. Mass balance at 

gage locations was evaluated by minimizing the percent mean 

error (%ME) in residuals. A residual is the difference between 

a simulated and observed value. Observed flows at gaging stations represent values at the end of model time steps, whereas 

simulated flows at corresponding node locations represent 

average values over model time steps. Although positive and 

negative residuals can offset each other, the measure does 

provide information about model bias. A balance in the overall 

error was sought because the model tended to underpredict 

flow upstream and overpredict downstream. The results presented herein achieve a balance in overall error.

Model fit at gage locations was evaluated by minimizing 

mean percent absolute error (M%AE) and root mean square 

error (RMSE) and maximizing a relative error measure called 

the coefficient of determination (RSQ). Another relative error 

measure, the modified index of agreement (MIOA), also was 

tested. The MIOA is thought to be more robust than RSQ 

(Legates and McCabe, 1999); however, differences between 

RSQ and MIOA typically were less than 15 percent and, 

therefore, RSQ was considered to be an acceptable measure. 

Associated error equations are

%ME = 

1/n ∑ (Qs

 -Qo)

i i = 1

n

* 100, Qo

(11)

M%AE = 1/n ∑ (Qs

 -Qo)

i = 1

n

* 100, Qo i

(12)

RMSE = 1/n ∑ (Qs

 -Qo)

i i = 1

n

 , 2

0.5

(13)

and

RSQ =

∑

i = 1

n

(Qo -Q)i (Qs -Q)i

∑ (Qo

 -Q)i

n

i = 1

2 ∑ (Qs

 -Q)i

n

i = 1

2

,

2

0.5 0.5 (14)

where

Qs = simulated flow,

Qo = observed flow,

Q = mean observed or simulated flow,

i = summation index,

and

n = number of time steps.

The quality of the gaging-station flow data affects model 

calibration and validation results. Individual gage accuracy 

was discussed earlier in this report. Unit values data (15 min) 

for gages integrated over 3 hours could have been used for 

calibration and validation; however, daily values data were 

used instead because these data are quality-assured in the 

USGS National Water Information System (NWIS) database. 

Daily values data are the more reliable and complete flow 

data set available. For example, unit values may have short 

periods of missing record as a result of equipment problems in 

the field. The missing daily values record is estimated during 

subsequent data analysis and computation. Only qualitative 

calibration and validation was performed for the Passaic River 

18 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey
at Dundee Dam at Clifton (01389890) because observed flows 

had to be estimated for this location, as described earlier. The 

observed data represent a “best estimate” of flow. Accordingly, 

the calibration at this location should be interpreted with caution.

Only daily data were available from facilities for discharges and diversions, and some of these data were incomplete and had to be assumed. An estimated diurnal variation 

was applied to these data, but the computed fine-time-scale 

data are uncertain. As a result, the model uses a 3-hour time 

step with flow results integrated over 24 hours for comparison 

with observed data. The only aspect of the model that might 

benefit from a finer time scale is the mixing algorithm, but 

any potential benefit would still depend on the availability of 

hourly discharge and diversion data. Calibrating the model 

based on average daily flows is a valid approach. In fact, given 

the uncertainty and variability associated with many boundary 

conditions, it can be argued that using average daily flows is 

the most appropriate temporal resolution.

Model Sensitivity

Certain model inputs affect model accuracy more than 

others and the effect depends on the sensitivity of model 

results to these inputs. Flow routing was relatively insensitive 

to changes in the hydraulic-geometry parameters because the 

model is controlled mainly by the many boundary conditions, 

the fact that hydrograph rise and fall in the Passaic River 

Basin are relatively slow, and the scale and timeframe of the 

model. If flow is steady, discharge will be constant at all locations, except where step increases in discharge occur, such 

as where tributaries enter the river, no matter what parameter 

values are used. In this case, flow routing is totally independent of the parameters, whereas area, depth, and velocity are 

quite sensitive to them. If flow varies gradually, the effect of 

flood waves is small, and the system is nearly always in steady 

state. When discharge changes gradually, detection of errors in 

wave timing is difficult.

Parameter insensitivity also may be related to the way 

DAFLOW computes the wave-dispersion coefficient, which 

is inversely proportional to channel width and slope, and the 

model limitation that dispersion cannot occur across model 

junctions. If slopes are flat so that the dispersive length scale 

(DL), which is directly proportional to the wave-dispersion 

coefficient, is large and the branches are relatively short, one 

wave may quickly traverse an entire branch. Therefore, adjusting the width does not affect DL because DL is already longer 

than the branch length. The model was slightly more sensitive 

to area than to width hydraulic-geometry parameters.

The breaks in elevation at Little Falls and Great Falls 

(fig. 1) were not taken into account in the determination of 

the channel slope. To test the sensitivity of channel slope, the 

water year 2001 simulation (discussed farther on) was reconfigured and run with a modified slope in branches 15 and 17 

to account for the breaks in elevation at Little Falls and Great 

Falls, respectively. Corresponding flatter slopes were used 

elsewhere in these branches. Simulation results in these two 

branches were virtually identical to those based on a reachaveraged slope.

DAFLOW only uses the slope to compute the wavedispersion coefficient. Slope is not related to wave speed and 

water velocity. Therefore, slope affects only the rate at which 

a mound of water in the channel dissipates (the rate at which 

a peak attenuates). The rate of attenuation of the peak with 

distance also depends on the wave speed, which has a greater 

effect than the wave-dispersion coefficient. Given the broad 

hydrograph peaks in the Passaic River Basin, the wave-dispersion coefficient has little effect on peak attenuation; thus, 

slope is relatively unimportant. Also, slope has less effect in 

short reaches because the wave attenuates over the entire reach 

for every time step, so changes in the wave-dispersion coefficient have little effect. The dissipation of the mound of water 

in the Passaic River Basin is calibrated reasonably. As a result 

of not including the two waterfalls in the model, the wave timing may be slightly inaccurate because slopes in those reaches 

are incorrect, but the total volume of flow within a 1- or 2-day 

period remain the same. From a water-quality perspective, the 

wave propagation is minor compared with the total volume of 

flow.

In contrast, the model was sensitive to changes made to 

the drainage-area ratio equations (discussed farther on) and 

time step size. A 3-hour time-step size was used in the model 

because numerical oscillations (instability) were seen in simulated hydrographs for certain calibration gages when a smaller 

time step was used. This result is likely caused by accuracy 

limitations associated with DAFLOW (Jobson and Harbaugh, 

1999, p. 5), such as the minimum ratio between advection and 

dispersion and restrictions relating time-step size to channel 

slope. The computation of the minimum ratio between advection and dispersion is a function of the time-step size, flow, 

width, slope, hydraulic-geometry parameters, and whether 

flow is increasing or decreasing with time. These variables 

are changing constantly. As long as the computed flows vary 

smoothly with time, this is not a problem.

An overbank flow simulation also was tested using a 

preliminary version of the model (May, 1998), and results 

matched the observed data fairly well, although calibration 

was not required for overbank flow. Graphs of measured 

discharge as a function of width at gaging stations helped 

to determine overbank flow conditions. A formal sensitivity 

analysis was done to evaluate the mixing algorithm that is 

discussed farther on.

Calibration of Flow Model

The flow-routing model must be able to simulate accurately a range of flow conditions. Low flows are affected 

primarily by discharges and diversions, whereas medium and 

high flows are affected primarily by flooding. Inaccuracy of 

discharge/diversion data is more important at low flows than 

high flows. Temporal patterns of runoff also vary with frontal 

Simulation of Surface-Water Flow 19
storms that typically occur in the non-growing season and 

convective storms that typically occur in the growing season.

The model simulates flow under all flow conditions. The 

target flow range for the Passaic River Basin nutrient TMDL 

is moderate (medium to low) flow conditions. The model was 

calibrated over the entire flow range and gave the best results 

for moderate flows, but did a reasonable job at other flows. 

For example, even though the cross-sectional formulation 

cannot represent overbank flows, the model yielded acceptable results at very high flows. From a TMDL perspective, the 

cross-sectional parameters are less important during overbank 

flows.

The first step in model calibration was to compare 

observed and simulated flow mass balance (volume). Simulated mass balance was calibrated to observed mass balance 

by adjusting coefficients in the drainage-area ratio equations 

by trial and error. All ungaged subbasins associated with a 

particular branch were adjusted in the same way to make the 

procedure practical. The next step in model calibration was 

to ensure a realistic representation of channel cross-sectional 

geometry. The final step in model calibration was to evaluate 

model fit at mainstem gaging stations by comparing simulated 

and observed hydrographs, flow-duration curves, and graphs 

of discharge-velocity-depth. Results of the calibration of mass 

balance and fit are discussed farther on.

Ungaged Subbasin Flows

A drainage-area ratio method, applied to estimate flows 

in ungaged subbasins and some boundary flows of the Passaic 

River Basin, also was subject to calibration. The method was 

applied to estimate flows in 287 mi2, or 35.7 percent, of the 

drainage basin (fig. 2). The method estimates subbasin flows 

based on data from index gages and coefficients used in equations for each subbasin, as described earlier. The method has 

strengths and weaknesses. Its main strength is its robustness; it 

provides a good overall estimate of flows. Its main weakness 

is its dependency on data from index gages in basins whose 

characteristics may differ from those of the basin for which 

flow is being estimated.

Index gages were selected as follows. All available 

gages in northeastern New Jersey were reviewed for use as 

index gages. Many gages had unique complications due to 

the effects of regulation or other factors; the best available 

gages were identified. To help select a particular index gage 

for a drainage-area ratio equation, daily flows for index gages 

were correlated for the period of this study, October 1999 to 

November 2003. This multi-year approach for selecting index 

gages allowed the effect of dry and wet seasons on flow to be 

captured.

Channel slope, percent storage (from land-use data), percent impervious surface, and soil permeability for the drainage 

area of each ungaged subbasin were determined using GIS 

data and ArcMap Spatial Analyst. Branch-averaged values also 

were used to simplify the analysis. Values for the same characteristics were also determined for the index gages. The difference in value was computed for each characteristic between 

each index gage, as well as for proximity and drainage area, 

and the difference was correlated with correlated daily gage 

flows. The difference in values between each index gage and 

each branch was then computed. For each branch, a rank- (for 

each gage) weighted (to account for the best correlated characteristics) sum (of characteristics) was computed. The lowest 

rank-weighted sums indicated the best index gages to use for a 

particular drainage-area ratio equation. Information on subbasins, index stations, and resulting equations is listed in table 4. 

Additional details can be found in unpublished files available 

at the USGS Water Science Center in West Trenton, N.J.

Because of error in flow data and the incomplete representation of basin characteristics, this methodology could be 

used only as a guide in selecting index gages--that is, the best 

choice did not always result in the best model fit at gaging 

stations. For example, the selection of index gage could have 

incorporated additional criteria, such as flashiness, climate, 

elevation, and ground-water components (for example, geology). Coefficients in equation 7 were calibrated by trial and 

error; resulting values are shown in table 4. The calibrated 

values account for a wide range of flows. Observed total flow 

mass balance at downstream gage locations indicated that 

associated upstream subbasin flows were reasonable.

Channel Cross-Section Geometry

Hydraulic-geometry parameters were calibrated using 

a combination of approaches, including (1) assuming values based on empirical data; (2) using DAFLOW accessory 

computer program FLWOPT to optimize values; (3) matching values to archived USGS streamflow and dye-tracer data; 

(4) matching values to cross-section surveys, various gage 

data, and dye-tracer data; and (5) adjusting values in order to 

improve water-quality-model calibration.

The first three approaches were implemented by USGS 

and provided initial parameter estimates. The first approach 

was based on tabulated values for parameters A2 and W2 

(equations 9 and 10) given in Jobson (2000). The second 

approach involved using the FLWOPT program to adjust 

hydraulic-geometry values by semiautomatically perturbing parameter values up or down in a user-driven procedure 

to minimize the root mean square error between simulated 

and observed flows. Calibration of parameters A1 and W1 

(equations 9 and 10) was attempted using FLWOPT, but the 

model was not sensitive to the parameter adjustments, as was 

discussed earlier.

The third approach was based on archived streamflow 

data collected by the USGS. Average channel width for an 

average flow could be determined at gaging stations. Parameter W1 was computed by using equation 10 and assuming a 

value for parameter W2. Dye-tracer data were available for 

USGS time-of-travel tests conducted during 1964-75 (Horwitz 

and Anderson, 1966; Anderson and Faust, 1973; and unpublished files available at the USGS Water Science Center in 

20 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey
Table 4. Flow estimates for contributing subbasins in the surface-water model of the nontidal Passaic River Basin, New Jersey.—Continued

[mi2, square miles; Ars., Arsenal; Q, discharge; ---, not available or not applicable]

Index gaging station Equation coefficients1

River Subbasin number2 and drainage area Asb (mi2

) Number Name

Drainage

area 

Aidx (mi2

)

C1 C2

Pequannock 1-1 --- --- --- --- --- --- --- --- --- --- --- --- 01384500 Ringwood Creek near Wanaque 19.1 1.3 0.9

20.2 --- --- --- --- --- --- --- --- --- --- --- ---

Wanaque 2-2 2-3 2-4 2-5 2-6 2-7 2-8 --- --- --- --- --- --- 01384500 Ringwood Creek near Wanaque 19.1 1.3 0.9

6.07 0.40 0.82 0.49 8.41 0.16 0.48 --- --- --- --- --- ---

Pequannock 3-2 3-3 --- --- --- --- --- --- --- --- --- --- --- 01384500 Ringwood Creek near Wanaque 19.1 1.3 0.9

0.05 2.69 --- --- --- --- --- --- --- --- --- --- ---

Ramapo 4-2 4-3 --- --- --- --- --- --- --- --- --- --- --- 01384500 Ringwood Creek near Wanaque 19.1 1.3 0.9

0.47 0.68 --- --- --- --- --- --- --- --- --- --- ---

Pompton 5-2 5-3 5-4 5-5 5-6 5-7 5-8 5-9 5-10 --- --- --- --- 01381400 Whippany River near Morristown 14.0 1.5 0.4

0.08 0.20 2.27 0.73 13.08 6.79 0.13 0.74 0.14 --- --- --- ---

Rockaway 6-2 6-3 6-4 6-5 6-6 6-7 6-8 --- --- --- --- --- --- 01379773 Green Pond Brook at Picatinny Ars. 7.65 0.7 -0.8

0.10 9.21 0.43 1.08 3.72 0.27 0.56 --- --- --- --- --- ---

Whippany 7-2 7-3 7-4 7-5 7-6 --- --- --- --- --- --- --- --- 01381400 Whippany River near Morristown 14.0 0.8 0.9

1.15 8.59 0.87 3.90 0.06 --- --- --- --- --- --- --- ---

7-7 7-8 7-9 7-10 7-11 7-12 7-13 7-14 7-15 7-16 --- --- --- 01379773 Green Pond Brook at Picatinny Ars. 7.65 1.5 -0.8

0.07 2.12 0.33 5.33 11.80 0.92 1.16 17.29 0.05 0.89 --- --- ---

Rockaway 8-2 --- --- --- --- --- --- --- --- --- --- --- --- 01379773 Green Pond Brook at Picatinny Ars. 7.65 0.7 -0.8

0.55 --- --- --- --- --- --- --- --- --- --- --- ---

Passaic 9-2 --- --- --- --- --- --- --- --- --- --- --- --- 01379000 Passaic River near Millington 55.4 1.2 0.0

2.40 --- --- --- --- --- --- --- --- --- --- --- ---

Dead 10-1 10-3 10-4 10-5 10-6 --- --- --- --- --- --- --- --- 01379000 Passaic River near Millington 55.4 1.2 0.0

13.12 0.57 3.10 3.85 0.14 --- --- --- --- --- --- --- ---

Passaic 11-2 11-3 11-4 11-5 11-6 11-7 11-8 11-9 11-10 11-11 11-12 11-13 11-14 01379000 Passaic River near Millington 55.4 1.2 0.0

3.30 2.47 2.50 0.93 0.06 1.51 1.30 1.13 6.51 0.46 0.16 0.29 0.85

Simulation of Surface-Water Flow 21
Table 4. Flow estimates for contributing subbasins in the surface-water model of the nontidal Passaic River Basin, New Jersey.—Continued

[mi2, square miles; Ars., Arsenal; Q, discharge; ---, not available or not applicable]

Index gaging station Equation coefficients1

River Subbasin number2 and drainage area Asb (mi2

) Number Name

Drainage

area 

Aidx (mi2

)

C1 C2

11-15 11-16 11-17 11-18 --- --- --- --- --- --- --- --- --- 01379000 Passaic River near Millington 55.4 0.7 -0.8

2.23 0.06 0.60 0.21 --- --- --- --- --- --- --- --- ---

11-19 --- --- --- --- --- --- --- --- --- --- --- --- 301379530 Canoe Brook near Summit 11.0 --- ---

12.19 --- --- --- --- --- --- --- --- --- --- --- ---

11-20 11-21 11-22 11-23 11-24 11-25 11-26 11-27 --- --- --- --- --- 01379000 Passaic River near Millington 55.4 0.7 -0.8

8.27 2.40 3.26 2.40 0.85 0.31 4.78 1.47 --- --- --- --- ---

Passaic 12-2 --- --- --- --- --- --- --- --- --- --- --- --- 01379000 Passaic River near Millington 55.4 0.7 -0.8

11.66 --- --- --- --- --- --- --- --- --- --- --- ---

12-3 12-4 12-5 12-6 12-7 12-8 12-9 --- --- --- --- --- --- 01381400 Whippany River near Morristown 14.0 1.5 0.4

2.47 0.09 1.80 2.02 2.93 1.44 0.59 --- --- --- --- --- ---

Passaic 13-2 --- --- --- --- --- --- --- --- --- --- --- --- 01381400 Whippany River near Morristown 14.0 1.0 0.0

0.14 --- --- --- --- --- --- --- --- --- --- --- ---

Singac 14-1 14-2 14-3 --- --- --- --- --- --- --- --- --- --- 01381400 Whippany River near Morristown 14.0 1.0 0.0

8.40 1.87 0.89 --- --- --- --- --- --- --- --- --- ---

Passaic 15-2 15-3 15-4 15-5 15-6 15-7 15-8 --- --- --- --- --- --- 01381400 Whippany River near Morristown 14.0 1.0 0.0

1.83 1.01 0.71 1.30 0.67 0.14 0.92 --- --- --- --- --- ---

Peckman 16-1 16-2 16-3 16-4 16-5 16-6 --- --- --- --- --- --- --- 01390500 Saddle River at Ridgewood 21.6 1.0 0.0

2.70 1.56 0.79 2.50 0.98 1.46 --- --- --- --- --- --- ---

Passaic 17-2 17-3 17-4 17-5 17-6 17-7 17-8 17-9 17-10 17-11 --- --- --- 01390500 Saddle River at Ridgewood 21.6 1.0 0.0

2.66 0.12 9.55 0.13 11.52 5.46 0.54 1.06 4.59 1.43 --- --- ---

1 Flow estimated by using drainage-area ratio equation: Qsb = C1 * (Asb/Aidx)C3 * Qidx + C2, in cubic feet per second. Coefficient C3 was set equal to 1.2 Locations shown in figure 2, except for subbasin 1-1. Subbasins listed in same row are combined in figure 2 using label shown in bold.3 Gage in contributing subbasin 11-19. Intervening drainage area below gage is 1.01 mi2. Includes diversion by New Jersey American.

22 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey
West Trenton, N.J.). Rhodamine B and WT dye tracers were 

used in these tests. Many of the dye tests were conducted 

during steady flow conditions. (If discharge at the time of a 

dye study was not available, it was obtained from the NWIS 

database.) Approximately 66 tests covering 11 of the 17 model 

branches were available. No dye-tracer data were available for 

branches 1-4, 14, and 16; parameter values for these branches 

were inferred from nearby or similar streams with dye-tracer 

data. Tests did not necessarily cover all of a particular branch, 

but results were assumed to apply to the entire branch. Computation of area parameters was possible for branches with 

dye-tracer data. Using two dye tests done in the same branch, 

these parameters could be computed by solving simultaneous equations using equation 9. For each study, discharge 

was divided by the velocity of the peak dye concentration to 

compute the total cross-sectional area. By assuming a value 

for parameter A2, one equation could be subtracted from the 

other to eliminate parameter A0, thereby allowing parameter 

A1 to be computed. Parameter A1 could then be substituted 

into either of the two equations to compute parameter A0. 

(Additional information regarding parameter A0 is discussed 

farther on.)

The fourth approach was implemented by TRC Omni 

(2007) to refine the above parameter estimates, which were 

not sufficient for the water-quality model. This approach 

involved three components based on the type of data used. The 

first component required developing rating curves and calibrating the hydraulic-geometry parameters to both the rating 

curve and the physical cross section. This involved comparing the relations between computed flow and cross-sectional 

area and between depth and width to data from cross-section 

surveys made at TRC Omni water-quality sampling stations 

and USGS gaging stations (second component). This approach 

was developed so these parameters could be represented for 

a variety of flows using the limited data available. USGS 

provided data for all types of surface-water stations and TRC 

Omni made field surveys at water-quality-sampling station 

locations. The field surveys were performed in order to ensure 

adequate data to calibrate the cross-sectional parameters. This 

approach consisted of using measured cross-section geometry, 

flow, and water-surface elevation to compute the relations 

between flow and cross-sectional area and between depth and 

width using a steady-state water-surface elevation computer 

program HEC-RAS (U.S. Army Corps of Engineers, 2002). 

HEC-RAS can compute cross-sectional area and top width for 

a uniform reach given a steady-state flow. The average depth 

is computed by dividing cross-sectional area by width. The 

cross-sectional area, width, and depth were computed for a 

range of flows. The calibration process consisted of finding 

parameters for the DAFLOW equations by trial and error that 

fit the geomorphic relations obtained from HEC-RAS.

The second component of this approach involved calibration of hydraulic-geometry parameters to cross-section 

data at USGS gages. This component was done similarly to 

the first and did not require the use of HEC-RAS. The third 

component of this approach involved using cross-sectional 

areas determined from the dye tests to validate the parameters 

calibrated using the TRC Omni surveys and USGS gage crosssection data. The areas from the dye tests were compared to 

the length-averaged areas computed using equation 9 and the 

calibrated cross-sectional parameters.

The fifth approach, implemented by TRC Omni (2007), 

involved manual parameter adjustment to facilitate calibration 

of WASP--for example, to account for the effects of Speedwell 

Lake and Lake Pocahontas (Morristown) on water-quality 

transport in the upper Whippany River.

The scope of the work done to determine values of 

hydraulic-geometry parameters that satisfied calibration of 

both the flow and water-quality models was substantial. The 

spatial and temporal extent of data and sites used for crosssection calibration is documented by TRC Omni (2007). 

Thirty-five cross sections were calibrated to guarantee the 

parameters were providing a realistic representation of the 

cross sections. The results shown in this report represent only 

a subset of all data and sites used for parameter calibration.

The calibrated cross-sectional areas, widths, and depths 

are summarized in table 5. USGS data from other types of stations also are included in this table. Final hydraulic-geometry 

parameter values were substituted into equations 9 and 10 to 

compute simulated cross-sectional area and width, respectively. Simulated hydraulic depth is computed by dividing area 

by width. Equations 9 and 10 are a theoretical approximation 

of the stream geometry. Therefore, not all the data obtained 

using the cross-section survey can be captured by the model. A 

general measure of accuracy can be obtained by comparing the 

difference between simulated and measured branch-averaged 

cross-sectional area, depth, and width, as shown in table 5. 

Subreaches were modeled using the detailed values that made 

up those averages. By reviewing the results for each branch, a 

good approximation can be obtained in most cases.

Values for certain calibrated cross-sectional parameters 

fall outside the ranges recommended by Jobson and Harbaugh 

(1999, p. 5), who suggest narrow ranges for parameter values. 

These ranges are meant to be a guide and not an absolute. 

Any group of measures contains substantial scatter; investigators look for central tendencies and generally de-emphasize 

extreme values. These ranges were proposed when DAFLOW 

was first developed, field experience with it was limited, and 

less geomorphic literature was available. Further, if the parameter values were limited to the suggested ranges, the relations 

between flow and cross-sectional area, width, and depth would 

not be satisfactory. Instead, the parameters were calibrated by 

observing the relations of flow to area, width, and depth, and 

of depth to width, that best represent the cross-sectional shape 

and flow velocities under a variety of conditions. The parameter values are justified because there is good calibration of 

both the flow and water-quality-transport models.

Simulation of Surface-Water Flow 23
Table 5. Calibrated channel cross-section geometry in the surface-water model of the nontidal Passaic River Basin, New 

Jersey.—Continued

[wq, water quality; ---, not available or not applicable]

River

mile

Measurement station2 Measured geometry Simulated geometry

River Branch1 Node Number Type Discharge3 Area Width Depth Area Width Depth

Pequannock 1 --- --- --- --- --- --- --- --- ---

1 0.00 01382800 gage 65.3 44.4 40.2 1.1 136.3 65.5 2.1

PE1 survey 209.1 283.5 78.8 5.6 231.9 78.0 3.0

2 0.88 --- --- --- --- --- --- --- --- ---

Average 163.9 59.5 3.3 184.1 71.8 2.5

Wanaque 2 --- --- --- --- --- --- --- --- ---

1 0.00 01387000 gage 71.3 56.1 41.1 1.4 60.6 32.1 1.9

WA1 survey 18.0 279.0 116.0 2.4 246.9 112.3 2.2

2 0.38 --- --- --- --- --- --- --- --- ---

3 1.09 --- --- --- --- --- --- --- --- ---

4 1.91 --- --- --- --- --- --- --- --- ---

5 3.33 --- --- --- --- --- --- --- --- ---

6 3.66 --- --- --- --- --- --- --- --- ---

7 4.03 WA2 survey 41.3 476.1 120.0 4.0 403.8 115.6 3.5

8 4.31 --- --- --- --- --- --- --- --- ---

9 5.19 --- --- --- --- --- --- --- --- ---

Average 270.4 92.4 2.6 237.1 86.7 2.5

Pequannock 3 --- --- --- --- --- --- --- --- ---

1 0.00 PE2 survey 253.9 84.6 49.9 1.7 84.6 50.9 1.7

2 0.24 --- --- --- --- --- --- --- --- ---

3 1.64 --- --- --- --- --- --- --- --- ---

4 1.94 --- --- --- --- --- --- --- --- ---

Average 84.6 49.9 1.7 84.6 50.9 1.7

Ramapo 4 --- --- --- --- --- --- --- --- ---

1 0.00 01388000 gage 279.8 202.9 90.7 2.2 300.5 98.7 3.0

RA3 survey 309.0 339.8 99.6 3.4 322.2 100.7 3.2

2 0.95 01388100 wq 93.6 571.1 95.1 6.0 514.2 92.0 5.6

3 1.60 --- --- --- --- --- --- --- --- ---

4 1.93 --- --- --- --- --- --- --- --- ---

Average 371.3 95.2 3.9 379.0 97.2 3.9

Pompton 5 --- dye 

tests

72.0 222.0 --- --- 199.2 --- ---

1 0.00 --- --- --- --- --- --- --- --- ---

2 0.19 01388500 gage 497.9 304.6 98.9 3.1 374.8 153.0 2.5

PO1 survey 145.0 176.3 120.2 1.5 186.4 121.0 1.5

3 0.41 --- --- --- --- --- --- --- --- ---

4 1.61 --- --- --- --- --- --- --- --- ---

5 2.41 01388600 wq 91.3 102.8 95.9 1.1 151.1 110.8 1.4

6 3.63 --- --- --- --- --- --- --- --- ---

7 5.40 PO2 survey 569.5 1165.5 239.4 4.8 693.3 173.0 4.0

8 5.64 --- --- --- --- --- --- --- --- ---

9 6.44 --- --- --- --- --- --- --- --- ---

10 6.63 01389000 low 

flow 87.1 297.2 157.7 1.9 440.0 163.5 2.7

11 6.87 PO3 survey 173.8 11.9 173.1 3.8 504.7 166.9 3.0

Average 325.7 147.5 2.7 364.2 148.0 2.5

Rockaway 6 --- dye 

tests

54.2 106.1 --- --- 152.9 --- ---

1 0.00 01381000 gage 142.1 75.5 46.9 1.6 181.0 78.2 2.3

RO1 survey 18.0 88.0 45.5 1.9 88.0 48.6 1.8

2 0.20 --- --- --- --- --- --- --- --- ---

3 2.16 --- --- --- --- --- --- --- --- ---

4 2.68 --- --- --- --- --- --- --- --- ---

5 3.24 --- --- --- --- --- --- --- --- ---

24 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey
Table 5. Calibrated channel cross-section geometry in the surface-water model of the nontidal Passaic River Basin, New 

Jersey.—Continued

[wq, water quality; ---, not available or not applicable]

River

mile

Measurement station2 Measured geometry Simulated geometry

River Branch1 Node Number Type Discharge3 Area Width Depth Area Width Depth

6 4.84 --- --- --- --- --- --- --- --- ---

7 5.37 RO2 survey 232.2 303.7 82.5 3.7 282.4 81.6 3.5

8 5.59 01381200 multiuse 54.7 108.5 63.1 1.7 165.2 71.7 2.3

9 6.65 --- --- --- --- --- --- --- --- ---

Average 136.4 59.5 2.2 173.9 70.0 2.5

Whippany 7 --- --- --- --- --- --- --- --- ---

1 0.00 01381400 gage 47.3 35.2 19.8 1.8 35.7 23.2 1.5

WI1 survey 30.2 51.2 27.2 1.9 27.9 21.7 1.3

2 1.13 --- --- --- --- --- --- --- --- ---

3 1.43 --- --- --- --- --- --- --- --- ---

4 1.92 --- dye 

tests

42.3 70.0 --- --- 95.9 --- ---

5 2.22 --- --- --- --- --- --- --- --- ---

6 2.72 --- --- --- --- --- --- --- --- ---

7 4.74 WI2 survey 67.0 132.6 55.1 2.4 129.9 57.2 2.3

8 4.95 01381500 gage 54.8 37.8 38.1 1.0 117.5 54.4 2.2

9 5.17 --- --- --- --- --- --- --- --- ---

10 6.69 --- --- --- --- --- --- --- --- ---

11 7.16 --- --- --- --- --- --- --- --- ---

12 8.00 --- --- --- --- --- --- --- --- ---

13 10.02 01381600 low 

flow 34.9 36.7 31.4 1.2 90.2 45.5 2.0

14 11.05 --- --- --- --- --- --- --- --- ---

15 12.69 --- --- --- --- --- --- --- --- ---

16 14.14 --- --- --- --- --- --- --- --- ---

17 14.39 01381800 gage 100.9 96.0 46.6 2.1 163.0 55.1 3.0

WI3 survey 270.0 316.7 64.8 4.9 296.6 65.7 4.5

18 14.58 --- --- --- --- --- --- --- --- ---

19 14.80 --- --- --- --- --- --- --- --- ---

Average 97.0 40.4 2.2 119.6 46.1 2.4

Rockaway 8 --- dye 

tests

68.0 82.0 --- --- 90.5 --- ---

1 0.00 --- --- --- --- --- --- --- --- ---

2 0.94 --- --- 68.0 --- --- --- 90.5 55.8 1.6

3 1.25 --- --- --- --- --- --- --- --- ---

Average 82.0 --- --- 90.5 55.8 1.6

Passaic 9 --- dye 

tests

28.4 48.7 --- --- 41.2 --- ---

1 0.00 01379000 gage 93.4 58.0 46.1 1.3 80.9 49.7 1.6

PA2 survey 124.0 235.2 79.8 2.9 96.3 53.4 1.8

2 1.47 --- --- --- --- --- --- --- --- ---

3 3.38 --- --- --- --- --- --- --- --- ---

Average 114.0 63.0 2.1 72.8 51.6 1.7

Dead 10 --- dye 

tests

8.0 38.0 --- --- 48.4 --- ---

1 0.00 01379100 low 

flow 1.6 5.7 10.4 0.6 20.2 24.0 0.8

2 0.21 --- --- --- --- --- --- --- --- ---

3 0.88 --- --- --- --- --- --- --- --- ---

4 2.20 --- --- --- --- --- --- --- --- ---

5 3.44 --- --- --- --- --- --- --- --- ---

6 3.60 01379200 low 

flow 12.3 37.1 23.9 1.5 62.5 51.8 1.2

DR1 survey 60.7 170.3 95.2 1.8 170.3 95.2 1.8

Simulation of Surface-Water Flow 25
Table 5. Calibrated channel cross-section geometry in the surface-water model of the nontidal Passaic River Basin, New 

Jersey.—Continued

[wq, water quality; ---, not available or not applicable]

River

mile

Measurement station2 Measured geometry Simulated geometry

River Branch1 Node Number Type Discharge3 Area Width Depth Area Width Depth

7 3.77 --- --- --- --- --- --- --- --- ---

Average 62.8 43.2 1.3 75.3 57.0 1.3

Passaic 11 --- dye 

tests

47.1 101.2 --- --- 104.2 --- ---

1 0.00 --- --- --- --- --- --- --- --- ---

2 1.60 --- --- --- --- --- --- --- --- ---

3 2.63 01379300 low 

flow 52.1 79.3 51.5 1.5 79.8 52.0 1.5

4 4.18 --- --- --- --- --- --- --- --- ---

5 4.45 PA3 survey 216.1 377.6 224.2 1.7 130.3 74.6 1.7

6 4.70 --- --- --- --- --- --- --- --- ---

7 5.71 --- --- --- --- --- --- --- --- ---

8 6.83 --- --- --- --- --- --- --- --- ---

9 7.41 --- --- --- --- --- --- --- --- ---

10 9.19 --- --- --- --- --- --- --- --- ---

11 9.76 --- --- --- --- --- --- --- --- ---

12 10.08 --- --- --- --- --- --- --- --- ---

13 10.51 --- --- --- --- --- --- --- --- ---

14 11.50 01379500 gage 175.7 104.5 72.3 1.4 118.6 73.6 1.6

15 13.39 PA4 survey 88.0 124.1 57.4 2.2 88.8 70.6 1.3

16 13.64 --- --- --- --- --- --- --- --- ---

17 14.06 --- --- --- --- --- --- --- --- ---

18 14.51 --- --- --- --- --- --- --- --- ---

19 15.08 --- --- --- --- --- --- --- --- ---

20 17.17 --- --- --- --- --- --- --- --- ---

21 19.21 --- --- --- --- --- --- --- --- ---

22 20.67 01379570 low 

flow 69.7 147.7 60.6 2.4 144.7 60.4 2.4

23 22.18 --- --- --- --- --- --- --- --- ---

24 23.28 PA5 survey 121.2 480.0 167.9 2.9 469.8 166.7 2.8

25 23.58 --- --- --- --- --- --- --- --- ---

26 24.49 --- --- --- --- --- --- --- --- ---

27 25.03 --- --- --- --- --- --- --- --- ---

28 25.52 --- --- --- --- --- --- --- --- ---

Average 202.1 105.6 2.0 162.3 83.0 1.9

Passaic 12 --- dye 

tests

102.0 296.0 --- --- 348.8 --- ---

1 0.00 --- --- --- --- --- --- --- --- ---

2 1.37 01381900 gage 621.4 612.6 163.9 3.7 566.6 135.1 4.2

3 4.07 PA6 survey 615.3 572.5 136.6 4.2 565.1 134.9 4.2

4 4.31 --- --- --- --- --- --- --- --- ---

5 6.33 --- --- --- --- --- --- --- --- ---

6 8.68 --- --- --- --- --- --- --- --- ---

7 10.85 --- --- --- --- --- --- --- --- ---

8 11.90 --- --- --- --- --- --- --- --- ---

9 12.34 --- --- --- --- --- --- --- --- ---

10 12.84 PA7 survey 628.3 659.8 273.9 2.4 656.4 273.0 2.4

11 13.05 01382000 multiuse 165.5 343.9 240.3 1.4 400.2 262.3 1.5

Average 497.0 203.6 2.9 507.4 201.3 3.1

Passaic 13 --- dye 

tests

212.0 1191.0 --- --- 1092.5 --- ---

1 0.00 --- --- --- --- --- --- --- --- ---

2 0.20 01389005 slope 224.4 451.8 263.1 1.7 557.4 267.4 2.1

0.41 --- --- --- --- --- --- --- --- ---

26 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey
Table 5. Calibrated channel cross-section geometry in the surface-water model of the nontidal Passaic River Basin, New 

Jersey.—Continued

[wq, water quality; ---, not available or not applicable]

River

mile

Measurement station2 Measured geometry Simulated geometry

River Branch1 Node Number Type Discharge3 Area Width Depth Area Width Depth

Average 821.4 --- --- 824.9 --- ---

Singac 14 --- --- --- --- --- --- --- --- ---

1 0.00 --- --- --- --- --- --- --- --- ---

2 0.28 --- --- --- --- --- --- --- --- ---

3 1.71 01389100 low 

flow 19.8 54.6 57.2 1.0 56.0 55.7 1.0

4 1.91 --- --- --- --- --- --- --- --- ---

Average 54.6 57.2 1.0 56.0 55.7 1.0

Passaic 15 --- dye 

tests

212.0 1191.0 --- --- 1092.5 --- ---

1 0.00 --- --- --- --- --- --- --- --- ---

2 0.44 --- --- --- --- --- --- --- --- ---

3 1.49 PA8 survey 1540.0 2345.2 293.3 8.0 2308.1 295.9 7.8

4 1.76 --- --- --- --- --- --- --- --- ---

5 2.61 --- --- --- --- --- --- --- --- ---

6 2.89 --- --- --- --- --- --- --- --- ---

7 3.15 --- --- --- --- --- --- --- --- ---

8 3.44 01389500 gage 1157.8 512.4 107.1 4.8 513.4 141.7 3.6

9 4.44 --- --- --- --- --- --- --- --- ---

Average 1349.5 200.2 6.4 1304.6 218.8 5.7

Peckman 16 --- --- --- --- --- --- --- --- ---

1 0.00 --- --- --- --- --- --- --- --- ---

2 1.13 01389534 crest 

stage

39.5 26.1 29.3 0.9 35.8 30.1 1.2

3 1.94 --- --- --- --- --- --- --- --- ---

4 3.09 --- --- --- --- --- --- --- --- ---

5 4.19 --- --- --- --- --- --- --- --- ---

6 5.24 01389600 low 

flow 14.7 26.3 28.9 0.9 28.8 30.1 1.0

7 5.53 --- --- --- --- --- --- --- --- ---

Average 26.2 29.1 0.9 32.3 30.1 1.1

Passaic 17 --- dye 

tests

639.0 931.0 --- --- 888.1 --- ---

1 0.00 --- --- --- --- --- --- --- --- ---

2 1.61 PA9 survey 2003.9 1103.0 257.1 4.3 1191.2 253.6 4.7

3 1.85 --- --- --- --- --- --- --- --- ---

4 2.85 01389802 total 

flow4 279.0 184.2 97.6 1.9 217.0 105.4 2.1

5 3.09 --- --- --- --- --- --- --- --- ---

6 5.12 --- --- --- --- --- --- --- --- ---

7 6.24 --- --- --- --- --- --- --- --- ---

8 7.26 PA10 survey 2069.9 2009.7 293.7 6.8 2028.4 291.4 7.0

9 7.55 01389870 wq 1232.7 636.7 230.7 2.8 756.1 241.6 3.1

10 10.11 --- --- --- --- --- --- --- --- ---

11 10.62 dam survey 4650.0 4806.0 540.0 8.9 4245.3 528.2 8.0

12 10.94 dam survey 19700.0 6472.8 558.0 11.6 6650.2 551.6 12.1

Average 2306.2 329.5 6.0 2282.3 328.6 6.2

1

 Locations shown in figure 6.

2

 Data from USGS stations, cross-section surveys at sampling stations (Marcelo Cerucci, TRC Omni Environmental Corp., written commun., 2005), 

archived USGS time-of-travel dye tests conducted during 1964-75 (unpublished files available at the USGS Water Science Center in West Trenton, New 

Jersey), and cross-section surveys at Dundee Dam (Emad Sidhom, United Water New Jersey, written commun., 2004). Dye tests yield a reach-averaged 

cross-section area for a given discharge.

3

 Estimated at sampling stations (Thomas Amidon, TRC Omni Environmental Corp., written commun., 2005).

4

 Approximate.

Simulation of Surface-Water Flow 27
Low-Flow Conditions (Water Year 2001)

To some degree, the choice of calibration period for the 

flow model and water-quality model was a function of project 

logistics and data availability. The model was calibrated for 

water year 2001, a low-flow year, which is comparable to 

the target flow conditions for evaluating river-water quality. 

(Note that WASP was calibrated for water year 2003.) Water 

year 2001 included a wide-ranging set of flow conditions for 

calibration. Simulated and observed results for six downstream 

gages are shown in figures 7 to 12; error analysis is shown in 

table 6. (Individual streamflow measurements, also shown in 

these figures, can indicate anomalies in the rating curve, and 

therefore, the observed flow record.) Comparison of simulated and observed mass balance yielded a percent mean error 

that is lower than the observed data error of four of the gages 

and equal to that of a fifth gage (01381900, Passaic River at 

Pine Brook). No quantitative comparison is made for station 

01389890, Passaic River at Dundee Dam at Clifton, because 

measured/observed data for this water year are unavailable.

The upper graph in figures 7 to 12 shows simulated and 

observed flow hydrographs; the middle graph shows simulated 

and observed flow-duration curves, with the abscissa divided 

into quartiles. The third quartile (50 to 75 percent) is thought 

to best represent the target flow range. Table 6 indicates 

whether the third quartile provides better (+) or worse (-) 

calibration results than the entire flow range. The lower graph 

in the figures shows simulated and measured flow velocity 

and depth. Measured values are computed from measured 

discharge, area, and width. Because streamflow measurements 

are typically made in narrow, shallow, channel cross sections, 

measured velocities are expected to be greater and depths are 

expected to be smaller than the simulated values. Impoundments may also affect the differences between measured and 

simulated velocities and depths (fig. 6, branches 4 and 15).

Model fit at the gages was evaluated mainly by using 

mean percent absolute error; additional statistics also are 

shown in table 6. The hydrograph matches are good to fair 

and within the accuracy of gages 01385500, Pompton River 

at Pompton Plains (fig. 7), and 01381500, Whippany River 

at Morristown (fig. 8). Calibration for flow duration, velocity, and depth are reasonable (better for 01385500) for 

these gages. Simulated velocity is underpredicted for gage 

01381500; a higher velocity would be expected in a headwaters reach.

The hydrograph match for gage 01379500, Passaic River 

near Chatham (fig. 9), originally showed a simulated wave 

speed that was slower than the observed wave speed and, 

consequently, a large mean percent absolute error. This timing 

offset propagated downstream. Unlike other subbasins in the 

model, subbasins in branches 9 through 11 and subbasin 12-2 

required use of index gage 01379000, Passaic River near Millington, as other index gages proved inadequate. The drainage 

area for this index gage is relatively large compared to those 

of other index gages and contains a large wetland area (Great 

Swamp), which can delay the downstream flow of water after 

a storm event. To account for these differences, a 20-hour 

forward lag was applied to flows at this index gage to increase 

the velocity of the flood wave as it moves downstream. As 

a result, calibration results improved at gage 01379500 and 

downstream gages. The hydrograph match is poor, however, 

and not within the accuracy of the gage. Calibration for flow 

duration, velocity, and depth are reasonable.

The hydrograph match is less accurate generally for gage 

01381900 (fig. 10), particularly in terms of wave attenuation. Calibration for flow duration matches better for the third 

quartile than for the entire flow range, whereas calibration for 

velocity and depth are reasonable. The hydrograph match is 

more difficult to achieve for gage 01389500, Passaic River 

at Little Falls (fig. 11). This discrepancy is caused in part by 

the propagation of model error downstream, the exaggeration of error at low flows, and the effect of nearby diversions 

at Wanaque South and Little Falls, which are superimposed 

on the hydrograph in figure 11 (and similar figures farther 

on). The main reason that peaks are not well captured is that 

DAFLOW is not able to simulate water storage resulting 

from overbank conditions. The match at this gage improved 

after a mixing algorithm (discussed farther on) was added to 

DAFLOW because the Wanaque South intake could then draw 

water from the Passaic River. Calibration for flow duration is 

very good and velocity and depth are reasonable. The corresponding match between simulated and estimated data is 

reasonable for station 01389890 (fig. 12).

Validation of Flow Model

Three other recent water years, representing other flow 

conditions, were simulated to ensure the flow model provides 

the hydraulic framework to support TMDL modeling of the 

Passaic River. The goal of these simulations was to validate 

drainage-area ratio equations and values of hydraulic-geometry parameters determined during calibration (water year 

2001). Water years 2000 (average flow), 2002 (extreme low 

flow), and 2003 (high flow) were used for these simulations. 

No further adjustment to equations or parameters was necessary during these simulations; in fact, combined mass-balance 

results for each water year were better than for water year 

2001. A storage boundary condition needed to be implemented 

for water year 2002 and the early part of water year 2003, 

however.

Average-Flow Conditions (Water Year 2000)

The model was validated for water year 2000, an average-flow year. Simulated and observed discharge, flow duration, velocity, and depth for six downstream gages are shown 

in figures 13 to18; error analysis is shown in table 6. Comparison of simulated and observed mass balance yielded percent 

mean errors that are less than the accuracy of the gages. The 

model overpredicted mass balance at gage 01379500, Passaic 

River at Chatham, compared to mass balance at this gage in 

28 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey
Simulation of Surface-Water Flow 29

water year 2001. No observed data are available for station 

01389890, Passaic River at Dundee Dam at Clifton, for water 

year 2000.

Model-fit results for water year 2000 were compared to 

results for water year 2001. The hydrograph match is generally within the accuracy of gages 01385500, Pompton River 

at Pompton Plains (fig. 13), and 01381500, Whippany River 

at Morristown (fig. 14). Validation for flow duration, velocity, and depth are reasonable (better for 01385500) for these 

gages, although validated velocity is not as good as expected 

for gage 01381500. The root mean square error is larger 

than expected for gage 01388500. The hydrograph match for 

gage 01379500 (fig. 15) yields an increased mean percent 

absolute error, although validation for flow duration, velocity, and depth are reasonable. The hydrograph match for gage 

01381900, Passaic River at Pine Brook (fig. 16), is less accurate; however, validation for flow duration, velocity, and depth 

are reasonable. Validation within the target flow range is better. The hydrograph match for gage 01389500, Passaic River 

at Little Falls, is comparable to that in water year 2001 (fig. 

17). Root mean square error is less than expected and validation for flow duration, velocity, and depth are reasonable. The 

corresponding match between simulated and estimated data 

also is reasonable for station 01389890 (fig. 18).

Extreme Low-Flow Conditions (Water Year 2002)

The model also was validated for water year 2002, an 

extreme low-flow year. Simulated and observed discharge, 

flow duration, velocity, and depth for six downstream gages 

are shown in figures 19 to 24; error analysis is shown in 

table 6. Comparison of simulated and observed mass balance 

yielded percent mean errors that are lower than the accuracy of 

four of the gages and greater than the accuracy of a fifth gage 

(01389500, Passaic River at Little Falls). The discrepancy for 

gage 01389500 is discussed below. The model overpredicted 

mass balance at gage 01388500, Passaic River at Pompton 

Plains, compared to the mass balance at this gage in water year 

2001. No observed data are available for station 01389890, 

Passaic River at Dundee Dam at Clifton, for water year 2002.

Model-fit results for water year 2002 were compared 

to results for water year 2001. The hydrograph match is 

not within the accuracy of gages 01388500 (fig. 19) and 

01381500, Whippany River at Morristown (fig. 20), and 

velocity validation is not as good as expected for gage 

01381500. Validation for flow duration, velocity, and depth are 

reasonable. Validation within the target flow range is better. 

The hydrograph match for gage 01379500, Passaic River near 

Chatham (fig. 21), yields an increased mean percent absolute 

error, although validation for flow duration, velocity, and 

depth are reasonable. The hydrograph match is more accurate 

for gage 01381900, Passaic River at Pine Brook (fig. 22). Validation for flow duration, velocity, and depth are reasonable.

Initially, the model failed to run for the 2002 water year 

because simulated flow decreased to zero near the Wanaque 

South and Little Falls intakes during intermittent short periods 

when river flow was less than 50 ft3/s locally and the combined diversions exceeded 250 ft3

/s. This discrepancy can 

be explained by (1) the lack of diurnal diversion data for 

Wanaque South intake, including a modified diversion pattern that coincided with rainfall events during the drought; 

(2) model sensitivity to the diversion boundary conditions; 

(3) fine-scale timing error in the routing; (4) observed-data 

error that is greater than the residual flow in the river; and (5) 

inaccurate channel cross-sectional geometry representation at 

very low flows. A transient storage boundary condition was 

developed to address this discrepancy.

The storage boundary condition is a surrogate for the 

extensive wetlands in the vicinity of Two Bridges, which cannot be simulated using DAFLOW. Release of water from storage is a reasonable assumption during very low flows and the 

effect of this boundary condition is expected to be small over a 

water year. Accordingly, the DAFLOW program was modified and a mass-balancing procedure was applied to remove a 

small volume of water from channel storage and store it in an 

off-channel reservoir (fig. 6, branch 12, node 8) until needed 

to maintain a minimum flow in the river. Although it is not 

difficult to determine the volume of water needed to make up 

the deficit, it is difficult to determine the exact timing and distribution of the addition. No more water was added than was 

necessary in order to minimize the effect on the water-quality 

model. A water-storage reservoir of approximately 30 million 

cubic feet (689 acre-ft) was required. The difference in flow 

between nodes 5-10 and 5-11 (fig. 6), representing the lower 

Pompton River, was used as the basis for minimizing the 

total flow deficit. When the total flow deficit was greater than 

zero or the volume in the subreach containing the nodes was 

negative, the difference in flow between the nodes was added 

manually to the storage boundary condition at leading time 

steps. The model was run, and the procedure was repeated 

until the deficit was zeroed. Afterwards, the equivalent flow 

was subtracted manually at trailing time steps by checking 

the same criteria. A disadvantage of this approach is that the 

model is no longer fully predictive. Any future simulations 

that involve different flow conditions will require rebalancing 

of the storage flows.

Despite the use of this boundary condition, the resulting 

hydrograph match is less accurate for gage 01389500 (fig. 23) 

than for other gages, particularly at low flows. Unfortunately, 

these results are the best that could be achieved. Validated 

flow duration highlights the discrepancy. Validation for 

velocity and depth are reasonable. The corresponding match 

between simulated and estimated data is better than expected 

for station 01389890 (fig. 24) when considering the upstream 

discrepancy at Little Falls.
30 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey Table 6. Model calibration and validation error at gage locations, Passaic River Basin, New Jersey. [%, percent; +, better than overall error; - worse than overall error; ---, not available or not applicable] Model error measures Observed data % Mean error Mean % absolute error Gage Name Branch1 Node Water year Mean discharge % Error Overall 50-75% flow duration Overall 50-75% flow duration Root mean square error Coefficient of determination 01388500 Pompton River at Pompton Plains

5 2 2000 561 10-15 -14.3

+ 11.8

+ 170.7 0.95

2001 439 10-15 -5.1

+ 8.9

+ 76.8 0.99

2002 119 10-15 3.9 - 16.5

+ 67.6 0.91

2003 731 10-15 -8.2

+ 8.6 - 149.2 0.99

01381500 Whippany River 

at Morristown 7 8 2000 49.7 10-20 -0.7 - 13.0 - 14.6 0.87 2001 46.9 10 -5.9 - 9.8 - 16.0 0.86

2002 27.8 10 -6.2 - 12.0

+ 10.2 0.89

2003 71.2 10 -0.3 - 12.0

+ 21.6 0.90

01379500 Passaic River near 

Chatham

11 14 2000 144 10-15 2.9 - 23.3 - 51.3 0.83

2001 146 10-15 -5.5

+ 16.5 - 39.5 0.93

2002 70.2 10-15 -0.7 - 19.2 - 26.7 0.922003 230 10-15 7.9

+ 13.7 - 56.3 0.95

01381900 Passaic River at 

Pine Brook

12 2 2000 590 10-15 -7.2

+ 18.4

+ 210.3 0.79

2001 551 10-15 -15.5

+ 17.4

+ 219.6 0.84

2002 257 10-15 -10.2 - 16.0

+ 125.3 0.84

2003 898 10-15 -9.0 - 20.2

+ 383.7 0.77

01395000 Passaic River at 

Little Falls

15 8 2000 950 10 10.6 - 21.9

+ 308.2 0.84

2001 822 10 5.3

+ 21.4 - 357.6 0.90

2002 199 10 14.4 - 53.2 - 161.5 0.912003 1526 10 5.7

+ 18.6

+ 628.4 0.87

01389890 Passaic River at 

Dundee Dam at 

Clifton

17 12 2000 1032 --- 8.3

+ 19.2

+ 296.8 0.85

2001 892 --- 4.4

+ 18.6 - 362.6 0.91

2002 241 --- 9.6 - 34.5 - 164.5 0.902003 1664 --- 5.2 - 17.0

+ 591.9 0.90

1 Locations shown in figure 6.
Simulation of Surface-Water Flow 31

10,000

1,000

100

10

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

WATER YEAR 2001

10,000

1,000

100

10

0 25 50 75 100

PERCENT OF TIME DISCHARGE EXCEEDED

5

4

3

2

1

0

VELOCITY, IN FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND DISCHARGE, IN CUBIC FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

10 100 1,000 10,000

(Branch 5, Node 2)

Measured

Observed-24 hr

Simulated-24 hr

Observed-24 hr

Simulated-24 hr

Measured velocity

Simulated velocity-24 hr

Simulated depth-24 hr

Measured depth

15

12

9

6

3

0

DEPTH, IN FEET

(a)

(b)

(c)

Figure 7. Calibrated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 01388500, Pompton River at Pompton Plains, 

New Jersey , water year 2001.
32 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey

10,000

1,000

100

10

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

WATER YEAR 2001

10,000

1,000

100

10

0 25 50 75 100

PERCENT OF TIME DISCHARGE EXCEEDED

5

4

3

2

1

0

VELOCITY, IN FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND DISCHARGE, IN CUBIC FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

10 100 1,000 10,000

(Branch 7, Node 8)

Measured

Observed-24 hr

Simulated-24 hr

Observed-24 hr

Simulated-24 hr

Measured velocity

Simulated velocity-24 hr

Simulated depth-24 hr

Measured depth

15

12

9

6

3

0

DEPTH, IN FEET

(a)

(b)

(c)

Figure 8. Calibrated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 01381500, Whippany River at Morristown, New 

Jersey , water year 2001.
Simulation of Surface-Water Flow 33

10,000

1,000

100

10

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

WATER YEAR 2001

10,000

1,000

100

10

0 25 50 75 100

PERCENT OF TIME DISCHARGE EXCEEDED

5

4

3

2

1

0

VELOCITY, IN FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND DISCHARGE, IN CUBIC FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

10 100 1,000 10,000

(Branch 11, Node 14)

Measured

Observed-24 hr

Simulated-24 hr

Observed-24 hr

Simulated-24 hr

Measured velocity

Simulated velocity-24 hr

Simulated depth-24 hr

Measured depth

15

12

9

6

3

0

DEPTH, IN FEET

(a)

(b)

(c)

Figure 9. Calibrated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 01379500, Passaic River near Chatham, New 

Jersey, water year 2001.
34 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey

10,000

1,000

100

10

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

WATER YEAR 2001

10,000

1,000

100

10

0 25 50 75 100

PERCENT OF TIME DISCHARGE EXCEEDED

5

4

3

2

1

0

VELOCITY, IN FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND DISCHARGE, IN CUBIC FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

10 100 1,000 10,000

(Branch 12, Node 2)

Measured

Observed-24 hr

Simulated-24 hr

Observed-24 hr

Simulated-24 hr

Measured velocity

Simulated velocity-24 hr

Simulated depth-24 hr

Measured depth

15

12

9

6

3

0

DEPTH, IN FEET

(a)

(b)

(c)

Figure 10. Calibrated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 01381900, Passaic River at Pine Brook, New 

Jersey, water year 2001.
Simulation of Surface-Water Flow 35

10,000

1,000

100

10

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

WATER YEAR 2001

10,000

1,000

100

10

0 25 50 75 100

PERCENT OF TIME DISCHARGE EXCEEDED

5

4

3

2

1

0

VELOCITY, IN FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND DISCHARGE, IN CUBIC FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

10 100 1,000 10,000

(Branch 15, Node 8)

Measured velocity

Simulated velocity-24 hr

Simulated depth-24 hr

Measured depth

15

12

9

6

3

0

DEPTH, IN FEET

(a)

(b)

(c)

Simulated-24 hr

Observed-24 hr

Wanaque South diversion24 hr

Little Falls diversion24 hr

Measured

Figure 11. Calibrated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 01389500, Passaic River at Little Falls, New 

Jersey, water year 2001.
36 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey

10,000

1,000

100

10

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

WATER YEAR 2001

10,000

1,000

100

10

0 25 50 75 100

PERCENT OF TIME DISCHARGE EXCEEDED

5

4

3

2

1

0

VELOCITY, IN FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND DISCHARGE, IN CUBIC FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

10 100 1,000 10,000

(Branch 17, Node 12)

Estimated-24 hr

Simulated-24 hr

Estimated-24 hr

Simulated-24 hr

15

12

9

6

3

0

DEPTH, IN FEET

(a)

(b)

(c) Simulated velocity-24 hr

Simulated depth-24 hr

Figure 12. Calibrated (a) discharge, (b) flow duration, and (c) velocity and depth at station 01389890, Passaic River at Dundee Dam at 

Clifton, New Jersey, water year 2001.
10,000

1,000

100

10

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

WATER YEAR 2000

10,000

1,000

100

10

0 25 50 75 100

PERCENT OF TIME DISCHARGE EXCEEDED

5

4

3

2

1

0

VELOCITY, IN FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND DISCHARGE, IN CUBIC FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

10 100 1,000 10,000

(Branch 5, Node 2)

Measured

Observed-24 hr

Simulated-24 hr

Observed-24 hr

Simulated-24 hr

Measured velocity

Simulated velocity-24 hr

Simulated depth-24 hr

Measured depth

15

12

9

6

3

0

DEPTH, IN FEET

(a)

(b)

(c)

Figure 13. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 01388500, Pompton River at Pompton Plains, 

New Jersey, water year 2000.

Simulation of Surface-Water Flow 37
38 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey

10,000

1,000

100

10

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

WATER YEAR 2000

10,000

1,000

100

10

0 25 50 75 100

PERCENT OF TIME DISCHARGE EXCEEDED

5

4

3

2

1

0

VELOCITY, IN FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND DISCHARGE, IN CUBIC FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

10 100 1,000 10,000

(Branch 7, Node 8)

Measured

Observed-24 hr

Simulated-24 hr

Observed-24 hr

Simulated-24 hr

Measured velocity

Simulated velocity-24 hr

Simulated depth-24 hr

Measured depth

15

12

9

6

3

0

DEPTH, IN FEET

(a)

(b)

(c)

Figure 14. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 01381500, Whippany River at Morristown, New 

Jersey, water year 2000.
10,000

1,000

100

10

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

WATER YEAR 2000

10,000

1,000

100

10

0 25 50 75 100

PERCENT OF TIME DISCHARGE EXCEEDED

5

4

3

2

1

0

VELOCITY, IN FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND DISCHARGE, IN CUBIC FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

10 100 1,000 10,000

(Branch 11, Node 14)

Measured

Observed-24 hr

Simulated-24 hr

Observed-24 hr

Simulated-24 hr

Measured velocity

Simulated velocity-24 hr

Simulated depth-24 hr

Measured depth

15

12

9

6

3

0

DEPTH, IN FEET

(a)

(b)

(c)

Figure 15. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 01379500, Passaic River near Chatham, New 

Jersey, water year 2000.

Simulation of Surface-Water Flow 39
40 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey

10,000

1,000

100

10

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

WATER YEAR 2000

10,000

1,000

100

10

0 25 50 75 100

PERCENT OF TIME DISCHARGE EXCEEDED

5

4

3

2

1

0

VELOCITY, IN FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND DISCHARGE, IN CUBIC FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

10 100 1,000 10,000

(Branch 12, Node 2)

Observed-24 hr

Simulated-24 hr

Measured velocity

Simulated velocity-24 hr

Simulated depth-24 hr

Measured depth

15

12

9

6

3

0

DEPTH, IN FEET

Measured

Observed-24 hr

Simulated-24 hr (a)

(b)

(c)

Figure 16. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 01381900, Passaic River at Pine Brook, New 

Jersey, water year 2000.
10,000

1,000

100

10

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

WATER YEAR 2000

10,000

1,000

100

10

0 25 50 75 100

PERCENT OF TIME DISCHARGE EXCEEDED

5

4

3

2

1

0

VELOCITY, IN FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND DISCHARGE, IN CUBIC FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

10 100 1,000 10,000

(Branch 15, Node 8)

Measured velocity

Simulated velocity-24 hr

Simulated depth-24 hr

Measured depth

15

12

9

6

3

0

DEPTH, IN FEET

Simulated-24 hr

Observed-24 hr

Wanaque South diversion24 hr

Little Falls diversion24 hr

Measured

(a)

(b)

(c)

Figure 17. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 01389500, Passaic River at Little Falls, New 

Jersey, water year 2000.

Simulation of Surface-Water Flow 41
42 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey

10,000

1,000

100

10

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

WATER YEAR 2000

10,000

1,000

100

10

0 25 50 75 100

PERCENT OF TIME DISCHARGE EXCEEDED

5

4

3

2

1

0

VELOCITY, IN FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND DISCHARGE, IN CUBIC FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

10 100 1,000 10,000

(Branch 17, Node 12)

Estimated-24 hr

Simulated-24 hr

Simulated velocity-24 hr

Simulated depth-24 hr

15

12

9

6

3

0

DEPTH, IN FEET

Estimated-24 hr

Simulated-24 hr (a)

(b)

(c)

Figure 18. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at station 01389890, Passaic River at Dundee Dam at 

Clifton, New Jersey, water year 2000.
10,000

1,000

100

10

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

WATER YEAR 2002

10,000

1,000

100

10

0 25 50 75 100

PERCENT OF TIME DISCHARGE EXCEEDED

5

4

3

2

1

0

VELOCITY, IN FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND DISCHARGE, IN CUBIC FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

10 100 1,000 10,000

(Branch 5, Node 2)

Observed-24 hr

Simulated-24 hr

Measured velocity

Simulated velocity-24 hr

Simulated depth-24 hr

Measured depth

15

12

9

6

3

0

DEPTH, IN FEET

Measured

Observed-24 hr

Simulated-24 hr (a)

(b)

(c)

Figure 19. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 01388500, Pompton River at Pompton Plains, 

New Jersey, water year 2002.

Simulation of Surface-Water Flow 43
10,000

1,000

100

10

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

WATER YEAR 2002

10,000

1,000

100

10

0 25 50 75 100

PERCENT OF TIME DISCHARGE EXCEEDED

5

4

3

2

1

0

VELOCITY, IN FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND DISCHARGE, IN CUBIC FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

10 100 1,000 10,000

(Branch 7, Node 8)

Observed-24 hr

Simulated-24 hr

Measured velocity

Simulated velocity-24 hr

Simulated depth-24 hr

Measured depth

15

12

9

6

3

0

DEPTH, IN FEET

Measured

Observed-24 hr

Simulated-24 hr (a)

(b)

(c)

Figure 20. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 01381500, Whippany River at Morristown, New 

Jersey, water year 2002.

44 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey
10,000

1,000

100

10

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

WATER YEAR 2002

10,000

1,000

100

10

0 25 50 75 100

PERCENT OF TIME DISCHARGE EXCEEDED

5

4

3

2

1

0

VELOCITY, IN FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND DISCHARGE, IN CUBIC FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

10 100 1,000 10,000

(Branch 11, Node 14)

Observed-24 hr

Simulated-24 hr

Measured velocity

Simulated velocity-24 hr

Simulated depth-24 hr

Measured depth

15

12

9

6

3

0

DEPTH, IN FEET

Measured

Observed-24 hr

Simulated-24 hr (a)

(b)

(c)

Figure 21. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 01379500, Passaic River near Chatham, New 

Jersey, water year 2002.

Simulation of Surface-Water Flow 45
10,000

1,000

100

10

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

WATER YEAR 2002

10,000

1,000

100

10

0 25 50 75 100

PERCENT OF TIME DISCHARGE EXCEEDED

5

4

3

2

1

0

VELOCITY, IN FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND DISCHARGE, IN CUBIC FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

10 100 1,000 10,000

(Branch 12, Node 2)

Observed-24 hr

Simulated-24 hr

Measured velocity

Simulated velocity-24 hr

Simulated depth-24 hr

Measured depth

15

12

9

6

3

0

DEPTH, IN FEET

Measured

Observed-24 hr

Simulated-24 hr (a)

(b)

(c)

Figure 22. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 01381900, Passaic River at Pine Brook, New 

Jersey, water year 2002.

46 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey
10,000

1,000

100

10

10,000

1,000

100

10

0 25 50 75 100

PERCENT OF TIME DISCHARGE EXCEEDED

5

4

3

2

1

0

VELOCITY, IN FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND DISCHARGE, IN CUBIC FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

10 100 1,000 10,000

(Branch 15, Node 8)

15

12

9

6

3

0

DEPTH, IN FEET

Simulated-24 hr

Observed-24 hr

Simulated-24 hr

Observed-24 hr

Wanaque South 

diversion-24 hr

Little Falls diversion24 hr

Measured

(a)

(b)

(c)

Measured velocity

Simulated velocity-24 hr

Simulated depth-24 hr

Measured depth

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

WATER YEAR 2002

Figure 23. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 01389500,Passaic River at Little Falls, New 

Jersey, water year 2002.

Simulation of Surface-Water Flow 47
10,000

1,000

100

10

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

WATER YEAR 2002

10,000

1,000

100

10

0 25 50 75 100

PERCENT OF TIME DISCHARGE EXCEEDED

5

4

3

2

1

0

VELOCITY, IN FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND DISCHARGE, IN CUBIC FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

10 100 1,000 10,000

(Branch 17, Node 12)

Estimated-24 hr

Simulated-24 hr

Simulated velocity-24 hr

Simulated depth-24 hr

15

12

9

6

3

0

DEPTH, IN FEET

Estimated-24 hr

Simulated-24 hr (a)

(b)

(c)

Figure 24. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at station 01389890, Passaic River at Dundee Dam at 

Clifton, New Jersey, water year 2002.

48 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey
High-Flow Conditions (Water Year 2003)

The model also was validated for water year 2003, a 

high-flow year. This simulation included the first 2 months of 

water year 2004 so as to cover the period of the water-quality 

model. At the time of validation, streamflow data from gaging 

stations for the first 2 months of water year 2004 had not yet 

undergone quality-assurance review by USGS. Validation 

discrepancies at peak flows also may be affected by reservoir 

spilling during storm events. The storage-balancing procedure 

required for water year 2002 was required for a few months 

at the start of water year 2003. A water-storage reservoir of 

approximately 3 x 106 ft3 (69 acre-ft) was required.

Simulated and observed results for six gages are shown in 

figures 25 to 30; error analysis is shown in table 6. Comparison of simulated and observed mass balance yielded percent 

mean errors that are less than the accuracy of the gages. The 

model overpredicted mass balance for gage 01379500, Passaic 

River at Chatham, compared to the mass balance at this gage 

for water year 2001. No observed data are available for station 

01389890, Passaic River at Dundee Dam at Clifton, for this 

water year.

Model-fit results for water year 2003 were compared to 

results for water year 2001. The hydrograph match is comparable to the accuracy of gage 01385500, Pompton River 

at Pompton Plains (fig. 25), and worse than the accuracy of 

gage 01381500, Whippany River at Morristown (fig. 26). 

Validation for flow duration, velocity, and depth are reasonable. Velocity validation is not as good as expected for gage 

01381500, although validation within the target flow range 

is better than for water year 2001. The hydrograph match for 

gage 01379500 (fig. 27) is more accurate, as indicated by the 

lower mean percent absolute error (table 6). Validation for 

flow duration, velocity, and depth are reasonable. The hydrograph match is less accurate for gage 01381900, Passaic River 

at Pine Brook (fig. 28). Validation for flow duration, velocity, 

and depth are reasonable. Validation within the target flow 

range is better. The hydrograph match is more accurate for 

gage 01389500, Passaic River at Little Falls (fig. 29). Validation for flow duration, velocity, and depth are reasonable. The 

corresponding match between simulated and estimated data is 

reasonable for station 01389890 (fig. 30).

Mixing Algorithm at Two Bridges, New Jersey

The Pompton River merges with the Passaic River at Two 

Bridges, New Jersey (fig. 31). The Wanaque South intake is 

approximately 1,000 ft upstream from the confluence on the 

left bank of the Pompton River (looking downstream). The 

Two Bridges Sewerage Authority (TBSA) outfall is approximately 1,000 ft upstream from the intake on the right bank of 

the Pompton River. As a result of the locally flat topography, 

reverse flow occurs near the mouth of the Pompton River 

back up to the intake during certain periods of low flow and 

high diversion. This effect also can entrain Passaic River flow 

back up to the intake and contributes to the mixing of water 

from the Pompton River, Passaic River, and TBSA outfall. 

This effect may extend a short distance downstream in the 

Passaic River (Phil Roosa, Passaic Valley Water Commission, 

oral commun., 2004). A hydroelectric plant at Little Falls, 

approximately 3 mi downstream from Two Bridges, also may 

affect the mixing (R.D. Schopp, U.S. Geological Survey, oral 

commun., 2004).

Because water quality differs among these three local 

flow sources, nutrient loading of the Wanaque Reservoir is 

affected by the proportion of flow to the Wanaque South 

intake that originates from each source. Water quality generally is better in the Pompton River than in the Passaic River 

(Anderson and Faust, 1973; Hickman, 1997). The surfacewater-quality standard for total phosphorus concentration 

(0.1 mg/L) is often exceeded in the Passaic River (and TBSA 

effluent). The Passaic River also contained dissolved solids at 

a concentration approximately 1.5 times that in the Pompton 

River during 1963-97 (USGS NWIS database). Total phosphorus loads from the three local flow sources in the vicinity 

of the intake differ greatly (fig. 32). (Only limited data were 

available for TBSA.)

Description of Algorithm

Because DAFLOW cannot simulate reverse flow, a mixing algorithm (subroutine) was developed (Harvey Jobson, 

U.S. Geological Survey, written commun., 2005) to account 

for the entrainment of Passaic River water into the Wanaque 

South intake under certain flow and diversion conditions. The 

mixing algorithm is a theoretical estimate of the distribution 

of water entrained by the Wanaque South intake among its 

three local sources (Pompton River, TBSA effluent, and Passaic River). The algorithm is based on a flow mass balance. 

The physics of the equations in the algorithm are based on the 

theory of diffusion in rivers and the hydrodynamics of streamlines and streamtubes as verified by many research studies (for 

example, Yotsukura, 1979) on lateral mixing in rivers. The 

five main equations are linear approximations to segments 

of theoretical mixing curves defining the relation between 

intake diversion and entrained TBSA effluent or Passaic River 

flow. The equations involve five parameters that affect mixing 

among the three sources as the diversion increases.

The variables used in the equations are defined below. 

The last five terms represent the mixing parameters.

Qsp = TBSA effluent entrained by intake,

Qs = effluent,

Qp = intake diversion,

Qin = Pompton River flow upstream from 

effluent outfall,

Qpam = Passaic River flow entrained by intake as a 

result of mixing,

Qpap = Passaic River flow entrained by intake as a 

result of advection,

Simulation of Surface-Water Flow 49
10,000

1,000

100

10

WATER YEAR 2003 AND EARLY 2004

10,000

1,000

100

10

0 25 50 75 100

PERCENT OF TIME DISCHARGE EXCEEDED

5

4

3

2

1

0

VELOCITY, IN FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND DISCHARGE, IN CUBIC FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

10 100 1,000 10,000

(Branch 5, Node 2)

15

12

9

6

3

0

DEPTH, IN FEET

(b)

(c)

Measured velocity

Simulated velocity-24 hr

Simulated depth-24 hr

Measured depth

Observed-24 hr

Simulated-24 hr

Measured

Observed-24 hr

Simulated-24 hr

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept Oct Nov

(a)

Figure 25. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 01388500, Pompton River at Pompton Plains, 

New Jersey, water year 2003 and early 2004.

50 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey
10,000

1,000

100

10

0 25 50 75 100

PERCENT OF TIME DISCHARGE EXCEEDED

5

4

3

2

1

0

VELOCITY, IN FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

10 100 1,000 10,000

Observed-24 hr

Simulated-24 hr

Measured velocity

Simulated velocity-24 hr

Simulated depth-24 hr

Measured depth

15

12

9

6

3

0

DEPTH, IN FEET

(b)

(c)

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept Oct Nov

(a)

10,000

1,000

100

10

WATER YEAR 2003 AND EARLY 2004

DISCHARGE, IN CUBIC FEET PER SECOND

(Branch 7, Node 8)

Measured

Observed-24 hr

Simulated-24 hr

Figure 26. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 01381500, Whippany River at Morristown, New 

Jersey, water year 2003 and early 2004.

Simulation of Surface-Water Flow 51
10,000

1,000

100

10

0 25 50 75 100

PERCENT OF TIME DISCHARGE EXCEEDED

5

4

3

2

1

0

VELOCITY, IN FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

10 100 1,000 10,000

Observed-24 hr

Simulated-24 hr

Measured velocity

Simulated velocity-24 hr

Simulated depth-24 hr

Measured depth

15

12

9

6

3

0

DEPTH, IN FEET

(b)

(c)

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept Oct Nov

10,000

1,000

100

10

WATER YEAR 2003 AND EARLY 2004

DISCHARGE, IN CUBIC FEET PER SECOND

(Branch 11, Node 14)

Measured

Observed-24 hr

Simulated-24 hr (a)

Figure 27. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 01379500, Passaic River near Chatham, New 

Jersey, water year 2003 and early 2004.

52 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey
10,000

1,000

100

10

0 25 50 75 100

PERCENT OF TIME DISCHARGE EXCEEDED

5

4

3

2

1

0

VELOCITY, IN FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

10 100 1,000 10,000

Measured velocity

Simulated velocity-24 hr

Simulated depth-24 hr

Measured depth

15

12

9

6

3

0

DEPTH, IN FEET

(b)

(c)

Observed-24 hr

Simulated-24 hr

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept Oct Nov

(a)

10,000

1,000

100

10

WATER YEAR 2003 AND EARLY 2004

DISCHARGE, IN CUBIC FEET PER SECOND

(Branch 12, Node 2)

Measured

Observed-24 hr

Simulated-24 hr

Figure 28. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 01381900, Passaic River at Pine Brook, New 

Jersey, water year 2003 and early 2004.

Simulation of Surface-Water Flow 53
10,000

1,000

100

10

DISCHARGE, IN CUBIC FEET PER SECOND

(Branch 15, Node 8)

WATER YEAR 2003 AND EARLY 2004

10,000

1,000

100

10

0 25 50 75 100

PERCENT OF TIME DISCHARGE EXCEEDED

5

4

3

2

1

0

VELOCITY, IN FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

10 100 1,000 10,000

15

12

9

6

3

0

DEPTH, IN FEET

(b)

(c)

Simulated-24 hr

Observed-24 hr

Wanaque South 

diversion-24 hr

Little Falls diversion24 hr

Measured

Measured velocity

Simulated velocity-24 hr

Simulated depth-24 hr

Measured depth

Oct Nov Dec Jan Feb Mar Apr May Sept Oct Nov

(a)

June July Aug

Figure 29. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at gage 01389500, Passaic River at Little Falls, New 

Jersey, water year 2003 and early 2004.

54 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey
10,000

1,000

100

10

0 25 50 75 100

PERCENT OF TIME DISCHARGE EXCEEDED

5

4

3

2

1

0

VELOCITY, IN FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

10 100 1,000 10,000

Estimated-24 hr

Simulated-24 hr

Simulated velocity-24 hr

Simulated depth-24 hr

15

12

9

6

3

0

DEPTH, IN FEET

(b)

(c)

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept Oct Nov

(a)

10,000

1,000

100

10

WATER YEAR 2003 AND EARLY 2004

DISCHARGE, IN CUBIC FEET PER SECOND

(Branch 17, Node 12)

Estimated-24 hr

Simulated-24 hr

Figure 30. Validated (a) discharge, (b) flow duration, and (c) velocity and depth at station 01389890, Passaic River at Dundee Dam at 

Clifton, New Jersey, water year 2003 and early 2004.

Simulation of Surface-Water Flow 55
R1 = ratio of intake diversion to Pompton River 

flow when mixing with effluent begins,

P1 = percent of effluent in total flow when 

intake diversion equals Pompton River 

flow,

P2 = percent of effluent in total flow when 

intake diversion equals Pompton River 

flow plus effluent,

D1 = flow in the Pompton River (either positive 

or negative) when the mixing influence is 

assumed to cease, 

and

QM = Passaic River flow entrained by the intake 

when the net downstream flow in the 

Pompton River below the intake is zero.

The first three equations define the mixing of Pompton River water and TBSA effluent. The amount of effluent 

entrained by the intake (Qsp) depends on the intake diversion 

(Qp). If Qp is less than a certain portion (R1) of the Pompton 

River flow upstream from the sewage outfall (Qin), then no 

effluent is entrained. If Qp is greater than R1 times Qin, but 

less than Qin, then Qsp is determined by equation 15. If Qp is 

greater than Qin, but less than Qin plus the effluent flow (Qs), 

then Qsp is determined by equation 16. Parameters P1 and 

P2 control the amount of effluent reaching the intake. If Qp

is greater than Qin plus Qs, but less than a fixed discharge of 

D1 plus Qin plus Qs, then Qsp is determined by equation 17. 

Finally, if Qp exceeds Qin plus Qs by more than D1, then all 

the effluent is entrained by the intake. A negative value for 

parameter D1 indicates that flow downstream from the intake 

is in the upstream direction, toward the intake (reverse flow).

Qsp = Qs * P1 

1 - R1

( ) - R1

Qp

Qin (15)

Qsp = Qs * P1 + Qs (P2 - P1) * Qs

(Qp - Qin) (16)

Qsp = Qs * P2 + (1 - P2) * D1

[Qp - (Qin + Qs)] (17)

01382000

01389005

Wanaque South 

intake

EXPLANATION

Discharge or diversion

site and name

Surface-water-quality 

station and number

Wanaque South 

Intake

01389005

Two Bridges Sewerage

Authority outfall

0 0.2 0.4 MILES

0 0.2 0.4 KILOMETERS

40°

53'

40"

40°

54'

74°16'40" 74°16'

Base from U.S. Geological Survey digital orthophoto data, 1:12,000

Universal Transverse Mercator Projection, Zone 18, NAD83

Two Bridges Road

Two Bridges Road

Figure 31. Location of sampling stations and discharge and diversion sites, Two Bridges, New Jersey, and vicinity.

56 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey
The last two equations define the mixing between the 

Pompton and Passaic Rivers. As Qp approaches Qin plus Qsp, 

flow in the Passaic River also will begin to move upstream, 

toward the intake. As the net downstream Pompton River flow 

below the intake approaches zero, some mixing with Passaic 

River flow will occur, and some Passaic River flow will be 

diverted. This entrainment of Passaic River flow is a result of 

mixing, not advection, because it occurs despite a small net 

downstream flow. Some Pompton River flow plus effluent 

moves downstream past the intake, and an equal amount of 

Passaic River flow moves upstream toward the intake. If the 

net downstream flow is greater than D1, then no Passaic River 

flow will be entrained by the intake. If the net downstream 

flow is greater than zero, but less than D1, then the Passaic 

River entrained flow (Qpam) is computed using equation 

18. When the net downstream flow is zero, parameter QM 

represents the amount of entrained Passaic River flow. As the 

intake diversion increases above Qin plus Qsp, additional flow 

is diverted from the Passaic River by advection (Qpap), which 

is computed using equation 19. In summary, the Passaic River 

flow that can move upstream to the intake varies from zero, 

when the Pompton River flow downstream from the intake is 

greater than D1, to QM, when the Pompton River flow downstream from the intake is zero.

D1

(Qp + D1 - Qin - Qsp) Qpam = QM * (18)

 Qpap = Qp - Qsp - Qin (19)

The mixing algorithm applies only during a limited flow 

range--that is, when Qp is comparable to the Pompton River 

flow. Outside this flow range, the algorithm has little or no 

importance. The algorithm does not apply if Qp is less than 

Qin and Qsp equals zero, or if Qp is greater than Qin plus Qs

plus D1 and Qsp equals Qs. Also, no flow is diverted from the 

Passaic River if Qp is less than Qin plus Qs plus D1.

Output from Algorithm

Little flow or water-quality data for the vicinity of Two 

Bridges were available for use in fully calibrating and validating the algorithm. Several types of calibration were attempted, 

but these attempts often were limited by insufficient data. 

In one study, a physical model was used in the design of 

Wanaque South intake (Hydro Research Science, Inc., 1983). 

Tests done for this study covered a range of flow conditions 

and indicated that complete mixing may have occurred when 

Pompton River flow was less than approximately 2,000 ft3/s. 

Diversions occur at Wanaque South for higher river flows, 

however, and that study addressed only specific flow combinations and did not account for TBSA effluent.

Continuously monitored and individual measurement surface-water and water-quality stations are shown in 

10

100

1,000

10,000

Oct-99 Feb-00 Jun-00 Oct-00 Feb-01 Jun-01 Oct-01 Feb-02 Jun-02 Oct-02 Feb-03 Jun-03 Oct-03

WATER YEAR

TOTAL PHOSPHORUS LOAD, IN POUNDS PER DAY 

1

10

100

1,000

2000 2001 2002 2003

INTAKE FLOW, IN CUBIC FEET PER SECOND 

2004

Flow at Wanaque South 

intake

LOAD AT

01382000

01388500

Two Bridges 

Sewerage Authority (Data obtained from facility.)

Figure 32. Intake flow and phosphorus loads in the vicinity of Two Bridges, New Jersey, 1999-2003. (Most locations shown in fig. 31)

Simulation of Surface-Water Flow 57
figure 31. The water-quality parameter for which the most 

data were available was specific conductance (FebruarySeptember 2002). These data were available from the USGS 

NWIS database and from North Jersey District Water Supply 

Commission and Passaic Valley Water Commission. TBSA 

also provided effluent dissolved-solids concentrations, which 

were converted to specific conductance by using the method 

described by Hem (1985) and surface-water-quality data.

The computed ratio of intake diversion to Pompton River 

flow when mixing with effluent begins (R1) could be approximated from the limited data by checking for times when 

conductance at the intake was similar to conductance on the 

opposite side of the river at Two Bridges Road and by checking for corresponding times when Pompton River flow was 

greater than the intake diversion (for example, during MayJune 2002). This approximation yielded a minimum value of 

0.5 for parameter R1. The remaining parameter values had to 

be assumed. It is assumed that TBSA contributes effluent to 

the intake mainly when the intake diversion is comparable to 

Pompton River flow. Further, it is assumed that TBSA effluent 

is only partially mixed across the Pompton River by the time it 

reaches the intake. General tracer tests indicate that transverse 

mixing likely occurs slowly when dye is injected at the river 

bank (Kilpatrick and Wilson, 1989). Accordingly, parameters 

P1 and P2 were assumed to equal 0.2 and 0.8, respectively. (It 

is possible that TBSA effluent is fully mixed before reaching 

the intake, in which case relevant output from the algorithm 

is not necessary.) Parameters D1 and QM each were assumed 

to equal 5 ft3/s; conducting a local dye-tracer test would help 

to verify these values. A tracer test to help determine mixing 

parameters was considered in the summer of 2004, but could 

not be conducted as a result of persistent high flow conditions.

Sensitivity analysis can provide additional information 

about the choice of mixing-parameter values. The effect of 

variation in parameter values on the average intake diversion 

from the local flow sources during water year 2002 is shown 

in figure 33. This analysis is confined to the limited range of 

Pompton River flows in which the parameters are relevant. 

Parameters R1, P1, and P2 are not included on the lower graph 

because they have little or no effect on the diversion of Passaic River flow. Simulation results generally are more sensitive to changes in parameters D1 and QM than to changes in 

parameters R1, P1, and P2, although intake diversion from the 

Pompton River is very sensitive to parameter R1, and intake 

diversion from TBSA is not sensitive to parameters QM or D1. 

These results likely are because effluent is only a small portion 

of the total flow diverted.

The simulated sources of water to Wanaque South intake 

based on the parameter values used are shown in “pumpographs” (intake diversion as a function of time) for the 4 water 

years (figs. 34a-d). Daily flows are shown in the figure. As 

expected, most of the diverted water comes from the Pompton 

River. During certain periods of low flow and high diversion, 

however, when the Pompton River flow is insufficient to supply the intake (for example, in water year 2002), TBSA and 

the Passaic River contribute flow to the intake. These contributions can occur throughout the year depending on local flow 

conditions.

In another study (Najarian Associates, 2005), cumulative 

frequency analysis was used to show that Passaic River flow 

was entrained approximately 55 percent of the time on intake 

operation days from 1993 to 2002. Water-quality simulation 

results indicated that, from October 1999 to November 2003, 

Passaic River water was entrained more than 50 percent of the 

days that diversion occurred, accounting for almost 20 percent 

of the flow and more than 42 percent of the phosphorus load to 

the diversion. These results are consistent with Najarian Associates’ (2005) estimates for 1993-2002. Also, the governing 

assumption used to determine Passaic River entrainment is the 

same assumption used by Najarian Associates (2005), namely 

that Pompton River water is used preferentially as long as 

flow is available to meet the demand; then Passaic River water 

is used to make up any deficit. Calibration of the mixing algorithm is important only in determining the amount of TBSA 

effluent entrained by the diversion. This determination is irrelevant when Passaic River water is entrained because all TBSA 

effluent and Pompton River water are entrained under those 

conditions. Ultimately, the parameter values used are considered acceptable because (1) adequate field data are lacking, (2) 

they satisfy the purpose of demonstrating the proof of concept, 

(3) they affect only local flow routing, and (4) their validity 

might be better evaluated through use of the water-quality 

model (that is, the parameter values may not be appropriate 

from a water-quality perspective).

Simulation of Water-Quality Transport

The water-quality computer program WASP was used by 

TRC Omni to simulate the dynamics of nutrient cycling and its 

effect on water-quality constituents. WASP is a dynamic finitedifference program for aquatic systems that includes the timevarying processes of advection, dispersion, point and nonpoint 

mass loading, and boundary exchange. Input to WASP consists 

of time series of streamflows, time series of constituent loads, 

constituent concentrations in streamflow, and several waterquality parameters. Output from WASP provides constituent 

data that can be used in establishing the Passaic River Basin 

nutrient TMDL.

In addition to the DAFLOW design considerations for 

WASP discussed earlier, TRC Omni (2007) developed a 

graphical user interface, one function of which was to reformulate output flows from DAFLOW for input to WASP. That 

is, DAFLOW output was converted from a Lagrangian to a 

Eulerian reference frame. In a Lagrangian reference frame, the 

computational nodes move with the flow; in a Eulerian reference frame, they are fixed in space. The interface also performs other functions for the water-quality modeling, including data processing and decision support.

58 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey
V A R I A T I O N I N D 1 O R Q M , I N C U B I C F E E T P E R S E C O N D

VARIATION IN R1, P1, OR P2

100

75

50

25

0

0 10 20 30 40

AVERAGE INTAKE DIVERSION FROM PASSAIC RIVER, IN CUBIC FEET PER SECOND

D1

QM

100

75

50

25

0

0 10 20 30 40

1.00

0.75

0.50

0.25

0

AVERAGE INTAKE DIVERSION FROM TWO BRIDGES SEWERAGE AUTHORITY, IN CUBIC FEET PER SECOND

D1

QM

R1

P1

P2

100

75

50

25

0

115 125 135 145 155

1.00

0.75

0.50

0.25

0

AVERAGE INTAKE DIVERSION FROM POMPTON RIVER, IN CUBIC FEET PER SECOND

D1

QM

R1

P1

P2

VARIATION IN R1, P1, OR P2

(a)

(b)

(c)

Figure 33. Results of sensitivity analysis on mixing algorithm parameters used in the flow model of the nontidal Passaic River, New 

Jersey, water year 2002. (Parameters D1, QM, R1, P1, and P2 identified on p. 56)

Simulation of Water-Quality Transport 59
500

400

300

200

100

0

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

WATER YEAR 2000

500

400

300

200

100

0

DAILY DIVERSION AT INTAKE, IN CUBIC FEET PER SECOND

DAILY DISCHARGE AT GAGE , IN CUBIC FEET PER SECOND

500

400

300

200

100

0

DAILY DISCHARGE AT GAGE, IN CUBIC FEET PER SECOND

500

400

300

200

100

0

DAILY DIVERSION AT INTAKE, IN CUBIC FEET PER SECOND

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

WATER YEAR 2001

(a)

(b)

EXPLANATION

Pompton River

Passaic River

Source

Two Bridges

Sewerage Authority

Gage 01388500, Pompton 

River at Pompton Plains

Figure 34. Simulated sources of water to Wanaque South intake, Two Bridges, New Jersey, for (a) water year 2000, (b) water year 

2001, (c) water year 2002, and (d) water year 2003 and early 2004.

60 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey
500

400

300

200

100

0

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

WATER YEAR 2002

500

400

300

200

100

0

DAILY DIVERSION AT INTAKE, IN CUBIC FEET PER SECOND

DAILY DISCHARGE AT GAGE, IN CUBIC FEET PER SECOND

500

400

300

200

100

0

DAILY DISCHARGE AT GAGE , IN CUBIC FEET PER SECOND

500

400

300

200

100

0

DAILY DIVERSION AT INTAKE, IN CUBIC FEET PER SECOND

WATER YEAR 2003 AND EARLY 2004

EXPLANATION

Pompton River

Passaic River

Source

Two Bridges

Sewerage Authority

(c)

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept Oct Nov

(d)

Gage 01388500, Pompton 

River at Pompton Plains

Figure 34. Simulated sources of water to Wanaque South intake, Two Bridges, New Jersey, for (a) water year 2000, (b) water year 

2001, (c) water year 2002, and (d) water year 2003 and early 2004.—Continued

Simulation of Water-Quality Transport 61
Channel Inactive Storage Area

DAFLOW simulates flood wave speed but not constituent transport speed. Accurate determination of hydraulicgeometry parameter A0, average channel cross-sectional 

area at zero flow, is required for the water-quality model, as 

discussed earlier in this report. Calibration of parameter A0 

also was described earlier by way of equation 9. If continuous 

concentration data were available at many locations within 

the model domain, a computer program like the Branched 

Lagrangian Transport Model (BLTM) could be used (Jobson 

and Schoellhamer, 1993; Jobson, 1997; Jobson, 2001) to 

accurately calibrate parameter A0. Such data are not available, 

although archived dye-tracer data from USGS time-of-travel 

tests do exist. Unfortunately, most of these data are unpublished. Published data are available for the subreach between 

Two Bridges and Little Falls, and can be used to validate the 

parameter A0 values there. Thus, BLTM was applied to simulate constituent transport in that subreach.

Time-of-travel tests involving 29.8 mi of the Passaic 

River (Horwitz and Anderson, 1966) were available for use 

in this transport simulation. The tests were conducted under 

steady flow conditions using fluorescent rhodamine B dye, 

which was thought to be relatively stable and non-reactive. 

Dye-concentration data were provided for a moderately lowflow tracer test conducted during June 16-19, 1964, but dye 

concentration as a function of time, required for BLTM, was 

given only for the sampling sites at Two Bridges and Little 

Falls. No pollutographs (concentration as a function of time) 

were available for an extreme-low-flow tracer test conducted 

during September 21-25, 1964.

Transport Submodel

The Branched Lagrangian Transport Model (BLTM) 

simulates dissolved-constituent transport in open channels by 

solving the one-dimensional advection-dispersion equation. 

BLTM uses a Lagrangian reference frame; a solution scheme 

that minimizes numerical dispersion and allows determination of the effect of each physical process on the computed 

concentrations. BLTM can accept DAFLOW output directly as 

input, and can route any number of interactive constituents for 

which the physical and (or) chemical reactions can be defined 

in a subroutine. The version of the BLTM used herein considers only first-order growth or decay. The transport equation for 

one constituent is

∂C

∂t = ∂∂ξ D ∂C∂ξ + S + Φ + K (C - CR), (20)

where 

C = concentration,

ξ = Lagrangian distance coordinate,

D = longitudinal dispersion coefficient,

S = rate of production of concentration, 

 which is independent of the concentration,

Φ = rate of change in concentration due to 

tributary inflow,

K = rate of production of the constituent,

and

CR = equilibrium concentration.

Design and Boundary Conditions

A DAFLOW submodel was needed to drive the BLTM 

submodel. Accordingly, a three-branch DAFLOW submodel 

was created from branches 13 to 15 (fig. 6) of the existing 

DAFLOW model. A 2.5-day simulation using 1-hour time 

steps was created to coincide with the period of the tracer 

test done in June 1964. The adequate subreach slope made 

the smaller time step feasible (Jobson and Harbaugh, 1999). 

Flow boundary conditions during the tracer test were reconstructed from the limited reported and archived data. Flows 

were assumed to be constant and no diversion was simulated 

at Little Falls (data were not available). A three-branch BLTM 

submodel also was created. A concentration boundary condition determined by discretizing the pollutograph at Two 

Bridges was input at the upstream end of the submodel. A 

1-hour time step was required to represent the variation in dye 

concentration with time shown in the pollutograph.

Calibration and Validation

A pollutograph showing the match between simulated 

and measured dye concentration at Little Falls is shown in 

figure 35. Concentration loss and peak attenuation and spread 

caused by decay and (or) dilution from inflows are reproduced. Tracers are lost in transit as a result of adhesion on 

sediments and photochemical decay. Dye loss was calibrated 

by adjusting a first-order decay coefficient and minimizing the 

mean error in residuals between simulated and measured concentrations. Peak dye attenuation and spread were calibrated 

by adjusting a dimensionless dispersion factor, which is based 

on the longitudinal dispersion coefficient, and minimizing the 

root mean square error in residuals. The calibrated decay rate 

of rhodamine B dye of 5.0 percent per hour is comparable to a 

measured decay rate of 7.5 percent per hour. In contrast, a dye 

such as rhodamine WT, which is less sorptive than rhodamine 

B, decays at only 5 percent per day (Wilson and others, 1986; 

Kilpatrick, 1993). The calibrated dispersion factor of 0.35 

could be refined by predicting the peak dye concentration at 

various points along the river caused by an upstream injection, using the procedure outlined in Jobson (1996), and then 

adjusting dispersion factors in each subreach to obtain simulated results similar to those predicted.

The timing of the peak dye concentration was approximately 3 hours too slow using the values for parameter A0 

from the existing DAFLOW model (fig. 35). This result could 

be improved by adjusting parameter A0 through trial and error. 

The submodel was validated using the calibrated transport 

parameters in a second simulation representing the September 

62 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey
1964 tracer test. The DAFLOW and BLTM submodels were 

reconstructed and run. Because only time-of-travel of the 

peak dye concentration was available from that tracer test, the 

input pollutograph from the June 1964 tracer test was used. 

Simulated results indicate a peak time-of-travel of 55.5 hours, 

whereas the measured data indicate a peak time-of-travel of 

58.3 hours. Thus, the transport submodel created indicates that 

simulated values for parameter A0 are very good in subreaches 

13 to 15.

Limitations of the Simulation Analysis

Hydrologic models are only as good as the assumptions 

used to develop them and the data used as input. One source of 

error is model error. Limitations of the DAFLOW and BLTM 

computer programs are discussed in the respective code documentation reports. Calibration is less good at some locations 

than at others as a result of the effects of spatial and temporal 

discretization, flat channel slope, the model’s weak representation of backwater conditions and off-channel storage, and a 

low ratio of advection to dispersion. Limitations of the mixing 

algorithm include simplified assumptions about local flow 

conditions and estimates for parameter values. For example, 

reverse flow is not allowed downstream from Two Bridges, 

represented by branch 13 (fig. 6). Validation can be expected 

to be worse than calibration in some cases because model 

parameters are adjusted only during the calibration process 

and not during validation.

Further, ground-water withdrawals from shallow wells 

near the river can induce the loss of river water to the well 

screens. This effect may be offset to some degree by pointsource discharges to the river. Withdrawals have their greatest 

effect at low flow. Individual withdrawals within the study 

area are documented in Storck and Nawyn (2001). Most 

of these withdrawals represent within-basin water use. To 

account for the effect of withdrawals or to include base flows, 

additional diversions and discharges could be included as 

model boundary conditions, or a linked ground-water/surfacewater computer program such as MODFLOW-DAFLOW 

(Jobson and Harbaugh, 1999) could be used.

Another source of error is data error, such as errors in 

rainfall-runoff relations associated with estimates of subbasin 

flows, which were determined using the drainage-area ratio 

method. Other data inaccuracies include errors in various gage 

JUNE 18-20, 1964

12

10

8

6

4

2

0

APPROXIMATE DYE CONCENTRATION, IN PARTS PER BILLION

0:00 6:00 12:00 18:00 0:00 6:00 12:00 18:00 0:00 6:00

18 19 20

Little Falls, simulated

Two Bridges, observed (input)

Little Falls, observed

(Model branches 13-15)

Figure 35. Calibrated dye transport between Two Bridges and Little Falls, New Jersey. (Observed data from Horwitz and Anderson, 

1966.)

Limitations of the Simulation Analysis 63
data, such as the effects of regulation and reservoir releases 

and the effects of backwater on flow at certain gages during 

water year 2003, and errors in dye-tracer data, such as the 

effects of poorly mixed dye. In addition, the discharge and 

diversion flow data are subject to inaccuracies, particularly in 

water year 2002.

Despite the limitations described above, model calibration and validation over a range of flow conditions indicate that the model’s ability to simulate flow in the Passaic 

River Basin generally is good. For a regional model with a 

daily calibration, the shape of a simulated hydrograph is not 

expected to match exactly the shape of an observed hydrograph. Although the model may not simulate local effects at all 

locations within the basin, it adequately simulates flow conditions in the basin as a whole. The error at most gaging stations 

during most water years is within 15 percent, and coefficient 

of determination (RSQ) is greater than 0.75. Comparisons of 

flow duration and other properties complement these statistics. 

These results indicate an acceptable calibration and validation 

of the flow model.

Summary

The Passaic River Basin, the third largest drainage 

basin in New Jersey (950 mi2), is in the heavily urbanized 

area outside New York City, with a population of 2 million. 

Mainstem tributaries of the Passaic River include the Pequannock, Wanaque, Ramapo, Pompton, Rockaway, and Whippany 

Rivers. The Saddle River subbasin is outside the study area. 

Efforts to develop Total Maximum Daily Loads (TMDLs) 

in the nontidal part of the basin (805 mi2) have focused on 

nutrient loading of the Wanaque Reservoir in the northern part 

of the basin. One source of nutrient loading is the transfer of 

water diverted at two downstream intakes back upstream to 

refill the reservoir. The larger of these diversions is Wanaque 

South intake, on the lower Pompton River near Two Bridges.

To support TMDL development efforts for nutrients in 

the basin, the NJDEP and local stakeholders determined that 

a water-quality model was needed to address the issue. TRC 

Omni Environmental Corp. developed this watershed waterquality model. An important input to this model was the river 

hydraulics. The USGS, in cooperation with the NJDEP and 

NJEC, developed a flow-routing model to provide this input. 

This report describes the development of the input flow data, 

construction and calibration of the flow model, and development of an algorithm for the model to simulate hydraulic mixing near the Wanaque South intake upstream from the confluence of the Passaic and Pompton Rivers. Integration issues 

between the flow model and the water-quality model also are 

described.

The Diffusion Analogy Flow model (DAFLOW) was 

used for flow routing and input to the Water Quality Analysis 

Simulation Program (WASP), which was used to simulate 

water-quality transport. Approximately 108 miles of the 

Passaic River and relevant tributaries were simulated. The 

river was discretized into 17 branches, 18 junctions, and 145 

nodes (channel cross sections). The time-step size for the flow 

model was limited to 3 hours. Boundaries for the flow model 

consisted of flows at six upstream gaging stations and estimated flows for three smaller tributaries. Ungaged subbasins 

(111 total with a combined drainage area of 287 mi2) consisted 

of tributaries and unchanneled drainage that contribute flow 

to the mainstem. Flows were estimated using the drainagearea ratio method. Twenty-five major municipal or industrial 

point-source discharges and five point-source diversions were 

simulated using flow data collected from facilities or extracted 

from NJDEP databases.

The model was calibrated for water year 2001 (low 

flow) and validated for water years 2000 (average flow), 2002 

(extreme low flow), and 2003 (high flow). Channel crosssection geometry was calibrated by adjusting simulated area 

and top width parameters. Several approaches were used for 

geometry calibration, and simulation data were compared 

quantitatively to measured data. Flow was calibrated at locations of five mainstem gaging stations and one estimated-flow 

station. The target calibration range was medium to low flows, 

as the Wanaque South intake typically does not operate during 

high flows or very low flows. Simulated flow mass balance, 

hydrographs, flow-duration curves, and velocity and depth 

data were calibrated against observed data. Mass balance (total 

volume) was calibrated quantitatively by adjusting the choice 

of index gages and (or) coefficients in the drainage-area ratio 

equations by trial and error. Hydrograph fit (flood-wave speed, 

wave attenuation, and spread) was calibrated visually and by 

using quantitative error measures. Simulated results generally 

were within the accuracy of the observed data. Flow calibration and validation results for 19 of 20 comparisons indicated 

average mass-balance and model-fit errors of 6.6 and 15.7 

percent, respectively. Calibration results for gage 01389500, 

Passaic River at Little Falls, were less accurate during water 

year 2002. The model reasonably represents the time variation 

of streamflow in the nontidal Passaic River Basin.

An algorithm (subroutine) was developed for DAFLOW 

to simulate hydraulic mixing that occurs near the Wanaque 

South intake upstream from the confluence of the Pompton 

and Passaic Rivers. Flow entrained by the intake, depending on local flow conditions, can be derived from multiple 

sources, including effluent from a nearby wastewater facility. The three sources contain different phosphorus loads. 

The algorithm determines the proportion of flow from each 

source, but operates within a narrow flow range when mixing 

occurs. Advection occurs outside this flow range. The equations used in the algorithm are based on the theory of diffusion 

and lateral mixing in rivers. The algorithm is based on a flow 

mass balance and consists of five equations and five input 

parameters. Parameters used in the equations were estimated 

from limited available local flow and water-quality data (for 

example, phosphorus loads). Model results over the 4 water 

years indicated the variation in distribution of source water 

to the intake; these results compared favorably with limited 

64 Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey
available reported data. As expected, the main source of water 

was the Pompton River. During certain short periods of low 

flow and high diversion, however--particularly in water year 

2002, when flow was extremely low--wastewater effluent and 

flow from the Passaic River made up for the insufficient flow 

in the Pompton River.

As additional verification of the simulated hydraulics 

for use in water-quality modeling, the Branched Lagrangian 

Transport Model (BLTM) was used to simulate dye transport 

in the 4-mile subreach between Two Bridges and Little Falls, 

the only subreach for which published dye-concentration 

data were available. Rhodamine B dye tracer was used in two 

injection tests. Flow and transport submodels of branches 13 

to 15 of the existing flow model were created using 1-hour 

time steps and reconstructed flow and concentration boundary conditions. Dye decay and longitudinal dispersion were 

calibrated to a tracer test done in June 1964. The submodel 

was roughly validated to a tracer test done in September 1964. 

Concentration mass, time-of-travel of the peak dye, and peak 

attenuation and spread of the dye cloud were reproduced. 

These results provide additional support regarding the accuracy of the DAFLOW model, particularly channel storage 

area.

The flow model indicated that flow routing was not as 

sensitive to hydraulic geometry parameters as was cross-sectional area, depth, and flow velocity. Model results were not 

sensitive to channel slope, but were sensitive to time step sizes 

less than 3 hours. A formal sensitivity analysis also was done 

to evaluate mixing algorithm parameter values. Limitations 

of the simulation analysis include model error (for example 

from calibration) and data error (for example gage flows). The 

flow and transport models are considered accurate given the 

indicated limitations.

Acknowledgments

The author thanks Harvey Jobson, formerly of the USGS 

Office of Surface Water, for his invaluable technical advice 

during the course of this study. He is the author of the computer programs used in this study and developed the mixing 

algorithm discussed in this report. The author also thanks the 

staff at TRC Omni (particularly Marcelo Cerucci), developer 

of the TMDL water-quality model, for a thorough technical 

review of the draft version of this report. Their comments 

were used to supplement existing report text. They also contributed to the development and calibration of the flow model. 

Officials of the major point-source discharge and diversion 

facilities in the study area are acknowledged for providing the 

requested flow and water-quality data. Finally, NJDEP Division of Watershed Management personnel are thanked for their 

technical review of the draft report.

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For additional information, write to:

Director

U.S. Geological Survey

New Jersey Water Science Center

Mountain View Office Park

810 Bear Tavern Rd., Suite 206

West Trenton, NJ 08628

or visit our Web site at:

http://nj.usgs.gov/
Spitz, F.J.,—Simulation of Surface-Water Conditions in the Nontidal Passaic River Basin, New Jersey—Scientific Investigations Report 2007-5052

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