28 Application of the SPARROW Model to Assess Surface-Water Nutrient Conditions and Sources, Pacific Northwest

Appendix B. Model Calibration and Prediction Results

The studentized residuals for the PNW NHD SPARROW 

models for TN and TP are shown in figures B1 and B2, 

respectively. The studentized residual is equal to the model 

residual (the difference between the natural logarithm of 

measured load and predicted load) divided by an estimate 

of its standard deviation. The negative values indicate over 

prediction and the positive values indicate under prediction. 

The incremental yields for total nitrogen and total 

phosphorus in kilograms per hectare per year are shown 

in figures B3 and B4, respectively. The mean annual total 

nitrogen and phosphorus loads and yields predicted by the 

PNW NHD SPARROW models are available online in a tabdelimited ASCII file at http://pubs.usgs.gov/sir/2013/5103/. 

The file includes predictions for individual stream reaches in 

the Pacific Northwest as defined by the National Hydrography 

Dataset Plus (NHDPlus, Pacific Northwest region [17]) 

medium resolution [1:100,000-scale] geospatial data set 

(Horizon Systems, 2013). SPARROW prediction variables in 

the ASCII file are described in the header (denoted by lines 

starting with “#”), and include COMID (common identifier 

of an NHD reach), AreaSqKM (area of the incremental NHD 

catchment, in square kilometers), TotDASqKM (total area 

draining to a reach, in square kilometers), predictions of the 

local mean annual load for each reach (in kilograms per year), 

predictions of the total mean annual load for each reach that 

is attributable to all upstream nutrient sources (in kilograms 

per year), and predictions of the total mean annual load for 

each reach that is attributable to individual upstream nutrient 

sources (in kilograms per year).

Reference Cited

Horizon Systems, 2013, NHDPlusV2Data: Horizon Systems 

database, accessed March 18, 2013, at http://www.horizonsystems.com/nhdplus/.
Appendix B 29

tac13-0821_figB1

CALIFORNIA

BRITISH COLUMBIA

OREGON

WASHINGTON

NEVADA UTAH

WYOMING

MONTANA

IDAHO

ALBERTA

Pacific Ocean Pacific Ocean

Willamette RWillamette R

Columbia River Columbia River

Snake

River

Snake

River

Clark ForkClark Fork

C

A

S

C

A

D

E

R

A

N

G

E

R

O

C

K

Y

M

O

U

N

T

A

I

N

S

ORCB

SOCR

WACR

MCOL

JDAY

YAKI

UCOL

MSBS

MSPW

USNK

SNKH

CLRW

SALM

PDOR

KOOT

SPOK

DESC

LSNK

NOCR

Oregon

Closed 

Basins

Columbia

Basin

Snake

River

River

Basin

PUGT

LCOL

WILL

West

Basins

Side

Pacific

Coast

Seattle Spokane

Portland

Boise

124° 122° 120° 118° 116° 114° 112° 110°

48°

46°

44°

42°

Base map modified from USGS and other U.S. agency 

and Canadian national digital data sources at various 

scales. Projection: Albers, SP1: 29.5, SP2: 45.5, LO: 23.0, 

CM: -96.0, Datum: North American Datum of 1983.

0 100 200 KILOMETERS

0 100 200 MILES

EXPLANATION

UCOL HUC Level 6 watershed and name—

full name in table 1.

Basin Major drainage

-3.27 to -3.00 (1)

-2.99 to -2.00 (5)

-1.99 to -1.00 (17)

-0.99 to 0.00 (61)

0.001 to 1.00 (62)

1.01 to 2.00 (19)

2.01 to 2.37 (7)

Studentized residual: Measured minus

predicted total nitrogen—value in 

parentheses is number of calibration 

stations.

Figure B1. Spatial distribution of residual stream load for the total nitrogen National Hydrography Dataset SPARROW model 

developed for the United States Pacific Northwest.
30 Application of the SPARROW Model to Assess Surface-Water Nutrient Conditions and Sources, Pacific Northwest

tac13-0821_figB2

ORCB

SOCR

PUGT

WACR

LCOL

MCOL

JDAY

YAKI

UCOL

MSBS

MSPW

USNK

SNKH

CLRW

SALM

PDOR

KOOT

SPOK

DESC

LSNK

NOCR

WILL

Oregon

Closed 

Basins

Snake

River

River

Basin

West

Basins

Side

Columbia

Basin

Pacific

Coast

Seattle Spokane

Portland

Boise

UNITED STATES

CANADA

124° 122° 120° 118° 116° 114° 112° 110°

48°

46°

44°

42°

EXPLANATION

Base map modified from USGS and other U.S. agency 

and Canadian national digital data sources at various 

scales. Projection: Albers, SP1: 29.5, SP2: 45.5, LO: 23.0, 

CM: -96.0, Datum: North American Datum of 1983.

UCOL HUC Level 6 watershed and name—

full name in table 1.

Basin Major drainage

-4.12 to -3.00 (2)

-2.99 to -2.00 (6)

-1.99 to -1.00 (16)

-0.99 to 0.00 (93)

0.001 to 1.00 (72)

1.01 to 2.00 (24)

2.01 to 3.00 (6)

3.01 to 3.47 (1)

0 100 200 KILOMETERS

0 100 200 MILES

Studentized residual: Measured minus 

predicted total phosphorus—value 

in parentheses is number of 

calibration stations. 

CALIFORNIA

BRITISH COLUMBIA

OREGON

WASHINGTON

NEVADA UTAH

WYOMING

MONTANA

IDAHO

ALBERTA

Pacific Ocean Pacific Ocean

Willamette RWillamette R

Columbia River Columbia River

Snake

River

Snake

River

Clark ForkClark Fork

C

A

S

C

A

D

E

R

A

N

G

E

R

O

C

K

Y

M

O

U

N

T

A

I

N

S

Figure B2. Spatial distribution of residual stream load for the total phosphorus National Hydrography Dataset SPARROW model 

developed for the United States Pacific Northwest.
Appendix B 31

tac13-0821_figB3

ORCB

SOCR

PUGT

WACR

LCOL

MCOL

JDAY

YAKI

UCOL

MSBS

MSPW

USNK

SNKH

CLRW

SALM

PDOR

KOOT

SPOK

DESC

LSNK

NOCR

WILL

Oregon

Closed 

Basins

Snake

River

River

Basin

West

Basins

Side

Columbia

Basin

Pacific

Coast

Seattle Spokane

Portland

Boise

UNITED STATES

CANADA

124° 122° 120° 118° 116° 114° 112° 110°

48°

46°

44°

42°

EXPLANATION

Base map modified from USGS and other U.S. agency 

and Canadian national digital data sources at various 

scales. Projection: Albers, SP1: 29.5, SP2: 45.5, LO: 23.0, 

CM: -96.0, Datum: North American Datum of 1983.

UCOL HUC Level 6 watershed and name—

full name in table 1.

Basin Major drainage

Incremental total nitrogen yield, in 

kilograms per hectare-year

0 100 200 KILOMETERS

0 100 200 MILES

CALIFORNIA

BRITISH COLUMBIA

OREGON

WASHINGTON

NEVADA UTAH

WYOMING

MONTANA

IDAHO

ALBERTA

Pacific Ocean Pacific Ocean

Willamette RWillamette R

Columbia River Columbia River

Snake

River

Snake

River

Clark ForkClark Fork

C

A

S

C

A

D

E

R

A

N

G

E

R

O

C

K

Y

M

O

U

N

T

A

I

N

S

< -0.100

0.101 to 0.500

0.501 to 1.000

1.001 to 1.500

1.501 to 2.000

2.001 to 2.500

2.501 to 3.000

> 3.00

No prediction

Figure B3. Incremental total nitrogen yields for National Hydrography Dataset catchments in the United States Pacific Northwest 

(2002 conditions).
32 Application of the SPARROW Model to Assess Surface-Water Nutrient Conditions and Sources, Pacific Northwest

tac13-0821_figB4

ORCB

SOCR

PUGT

WACR

LCOL

MCOL

JDAY

YAKI

UCOL

MSBS

MSPW

USNK

SNKH

CLRW

SALM

PDOR

KOOT

SPOK

DESC

LSNK

NOCR

WILL

Oregon

Closed 

Basins

Snake

River

River

Basin

West

Basins

Side

Columbia

Basin

Pacific

Coast

Seattle Spokane

Portland

Boise

UNITED STATES

CANADA Incremental total phosphorus yield, 

in kilograms per hectare-year

124° 122° 120° 118° 116° 114° 112° 110°

48°

46°

44°

42°

EXPLANATION

Base map modified from USGS and other U.S. agency 

and Canadian national digital data sources at various 

scales. Projection: Albers, SP1: 29.5, SP2: 45.5, LO: 23.0, 

CM: -96.0, Datum: North American Datum of 1983.

UCOL HUC Level 6 watershed and name—

full name in table 1.

Basin Major drainage

0 100 200 KILOMETERS

0 100 200 MILES

CALIFORNIA

BRITISH COLUMBIA

OREGON

WASHINGTON

NEVADA UTAH

WYOMING

MONTANA

IDAHO

ALBERTA

Pacific Ocean Pacific Ocean

Willamette RWillamette R

Columbia River Columbia River

Snake

River

Snake

River

Clark ForkClark Fork

C

A

S

C

A

D

E

R

A

N

G

E

R

O

C

K

Y

M

O

U

N

T

A

I

N

S

< 0.0400

0.0401 - 0.0800

0.0801 - 0.1200

0.1201 - 0.1600

0.1601 - 0.2000

0.2001 - 0.2400

0.2401 - 0.2800

> 0.2800

No prediction

Figure B4. Incremental total phosphorus yields for National Hydrography Dataset catchments in the United States Pacific 

Northwest (2002 conditions).