Front cover: 

Top: 

The Santiam River at river mile 9.5, taken on August 7, 2002. 

Lower: 

The North Santiam River at river mile 57.3, taken on June 4, 2002. 

Both photographs by Ian Wigger (U.S. Geological Survey). 
Modeling Streamflow and Water 

Temperature in the North Santiam and 

Santiam Rivers, Oregon, 2001–02 

By Annett B. Sullivan and Stewart A. Rounds 

Prepared in cooperation with the Oregon Association of Clean Water Agencies 

Scientific Investigations Report 2004–5001 

U.S. Department of the Interior

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

Gale A. Norton, Secretary 

U.S. Geological Survey

Charles G. Groat, Director 

U.S. Geological Survey, Portland, Oregon: 2004 

For sale by U.S. Geological Survey, Information Services


Box 25286, Denver Federal Center


Denver, CO 80225


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Although this report is in the public domain, permission must be secured from the individual copyright owners to


reproduce any copyrighted materials contained within this report.


The calibrated models of the North Santiam and Santiam Rivers, as used in this investigation, are available for 


download from the Internet at http://oregon.usgs.gov/projs_dir/will_tmdl/model.html


Suggested citation: 

Sullivan, A.B., and Rounds, S.A., 2004, Modeling streamflow and water temperature in the North Santiam and Santiam Rivers, Oregon, 2001–02: 

U.S. Geological Survey Scientific Investigations Report 2004–5001, 35 p. 
 iii 

CONTENTS


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


Significant Findings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1


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


Site Description, Basin Characteristics, and Hydrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2


Purpose and Scope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4


Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4


Model Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4


Bathymetric Data and the Model Grid. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5


Temporal Inputs and Shading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5


Meteorology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6


Precipitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6


Streamflow and Stream Temperature. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6


Withdrawals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8


Riparian Shading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8


Ground Water and Ungaged Tributaries. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10


Calibration Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10


Model Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11


Water Balance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11


Flow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11


Channel Width. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12


Travel Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12


Water Temperature. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14


Sensitivity Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22


Point Sources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23


Dam Release Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23


Air Temperature. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24


Riparian Vegetation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24


Dam Release Flow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26


Simulation of System Potential Conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27


 System-Potential Vegetation with Proposed NOAA Fisheries Target Flows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27


 System-Potential Vegetation with Proposed NOAA Fisheries Target Flows and a More 


Natural Seasonal Temperature Regime in Dam Releases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27


Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29


Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30


References Cited. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30


Appendix 1. Revised Water Temperature Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

iv 

Figures

 1. Map of the North Santiam and Santiam rivers, Oregon, showing the locations of data-collection stations . . . . . . . . . . . 3


 2. Schematic diagram of the model grid, with branch boundaries and river miles from the mouth of the 


Santiam River . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6


 3. Schematic diagram showing locations of point-source and tributary inflows, withdrawals, and USGS 

streamflow gages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7


4–20. Graphs showing:


 4. Streamflow in (A) the North Santiam River at Niagara (USGS station 14181500), just downstream from the 

dams, (B) the Little North Santiam River (USGS station 14182500), and (C) the South Santiam River 

for July 2001 through October 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

 5. Water temperatures in the North Santiam River at Niagara (USGS station 14181500), just downstream from 

the dams, and at the Little North Santiam (USGS station 14182500) for July 2001 through October 2002 . . . . . . . . . . . . 10

 6. Vegetative shading for current conditions and system potential on August 1, 2001, for the North Santiam


and Santiam Rivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11


 7. Comparison of measured streamflow at the USGS gages at Mehama (USGS station 14183000) and 


Jefferson (USGS station 14189000) to calibrated model output for (A) 2001 and (B) 2002 . . . . . . . . . . . . . . . . . . . . . . . . . 13


 8. Comparison of USGS field-measured channel width to Oregon Department of Environmental Quality


digitized channel width and to wetted width from the calibrated model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14


 9. Comparison of simulated travel times to field measurements by Harris (1968) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15


10. Daily average and hourly comparison of model output to measured temperature at calibration stations in 2001 . . . . 16


11. Daily average and hourly comparison of model output to measured temperature at calibration stations in 2002 . . . . 18


12. Simulated 7-day moving average of daily maximum water temperature in degrees Celsius for 2001 and 2002 . . . . . . 21


13. Difference between the simulated 7-day moving average of daily maximum water temperature and the 


applicable water temperature standard in degrees Celsius . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22


14. Difference in water temperature between the base model and the model with dam release temperatures 

(A) increased by 5°C and (B) decreased by 5°C, using the 7-day moving average of daily maximum water 


temperature in degrees Celsius . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23


15. Difference in water temperature between the base model and the model with air temperature (A) increased


by 5°C and (B) decreased by 5°C, using the 7-day moving average of daily maximum water temperature in 


degrees Celsius . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25


16. Difference in water temperature between the base model and the model (A) with system potential shade and 

(B) without any riparian shade, using the 7-day moving average of daily maximum water temperature in degrees


Celsius. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25


17. Difference in temperature between the base model and the model with dam release flows (A) increased by


20 percent and (B) decreased by 20 percent, using the 7-day moving averages of daily maximum water


temperature in degrees Celsius . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26


18. Proposed NOAA Fisheries minimum flow targets for releases from the Detroit and Big Cliff dam complex, 

U.S. Army Corps of Engineers simulated flow from Detroit Dam using those targets, and measured flow at


Niagara for 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27


19. Estimated more-natural seasonal water temperature and measured temperature (as released from the dam) in 


the North Santiam River at Niagara. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28


20. Temperature change for (A) system-potential scenario 1 and (B) system-potential scenario 2 for 2001, 


using the 7-day moving average of daily maximum water temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29


A-1. Difference between the simulated 7-day moving average of daily maximum water temperature and the


revised water temperature standard, in degrees Celsius . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

 v 

Tables 

1. Summary of North Santiam and Santiam Rivers 303(d) temperature listings in 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 

2. Summary of the CE-QUAL-W2 model grid used to represent the North Santiam and Santiam Rivers . . . . . . . . . . . . . . . . . . . .6 

3. Locations of monitors used to calibrate temperature in the North Santiam and Santiam Rivers . . . . . . . . . . . . . . . . . . . . . . .12 

4. Goodness of fit statistics for hourly water temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 

5. Goodness of fit statistics for 7dADM water temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 

6. Summary of the model sensitivity analysis for the North Santiam River in 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 

7. Summary of results from system potential simulations for 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28 

Conversion Factors and Datum 

Multiply By To obtain 

Length 

centimeter (cm) 0.3937 inch (in) 

millimeter (mm) 0.03937 inch (in) 

meter (m) 3.281 foot (ft) 

Area 

square centimeter (cm2) 0.001076 square foot (ft2) 

square meter (m2) 10.76 square foot (ft2) 

square centimeter (cm2) 0.1550 square inch (in2) 

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:


°F = (1.8 x °C) + 32


Vertical coordinate information is referenced to the North American Vertical Datum of 1988 (NAVD 88).

Modeling Streamflow and Water Temperature in the 

North Santiam and Santiam Rivers, Oregon, 2001–02 

By Annett B. Sullivan and Stewart A. Rounds 

Abstract exceedances occurred in the lower North Santiam River 

and Santiam River from late June through mid-October. 

Temperature standards were sometimes exceeded by To support the development of a total maximum daily load 

(TMDL) for water temperature in the Willamette Basin, the laterally averaged, two-dimensional model CE-QUAL-W2 was 

used to construct a water temperature and streamflow model of 

the Santiam and North Santiam Rivers. The rivers were simulated from downstream of Detroit and Big Cliff dams to the 

confluence with the Willamette River. Inputs to the model 

included bathymetric data, flow and temperature from dam 

releases, tributary flow and temperature, and meteorologic data. 

The model was calibrated for the period July 1 through November 21, 2001, and confirmed with data from April 1 through 

October 31, 2002. Flow calibration made use of data from two 

streamflow gages, and travel time and river-width data. Temperature calibration used data from 16 temperature monitoring 

locations in 2001 and 5 locations in 2002. A sensitivity analysis 

was completed by independently varying input parameters, 

including point-source flow, air temperature, flow and water 

temperature from dam releases, and riparian shading. Scenario 

analyses considered hypothetical river conditions without 

anthropogenic heat inputs, with restored riparian vegetation, 

with minimum streamflow from the dams, and with a more-natural seasonal water temperature regime from dam releases. 

more than 7°C. 

3.	 The CE-QUAL-W2 model simulated both hourly and 

seasonal temperatures in these rivers with an acceptable 

level of accuracy. Comparison of hourly simulated river 

temperature to measured data from 16 temperature 

sensors in 2001 and 5 temperature sensors in 2002 

produced mean absolute errors (MAE) between 0.41°C 

and 1.02°C and root mean square errors (RMSE) 

between 0.50°C and 1.16°C. Using a 7-day moving 

average of the daily maximum temperature, the MAE 

ranged from 0.15°C to 1.05°C, and the RMSE ranged 

from 0.21°C to 1.14°C. The largest differences between 

simulated and measured temperatures occurred in the 

lower Santiam River, where measured daily temperature 

variation became small close to the confluence with the 

Willamette River, while the model simulated a larger 

daily temperature variation. River temperatures may 

have been damped by hyporheic flow and exchange 

of shallow ground water with river water near the 

Willamette River, processes that were not simulated 

by the model. 

4.	 Sensitivity analyses showed that river water temperature 

was most sensitive to a direct change in water temperaSignificant Findings	 ture from dam releases, though this effect decreased 

downstream. Changes in air temperature, riparian 

vegetation and dam release flows also produced changes 1.	 Summertime river temperatures were generally coolest in water temperature, with different spatial patterns of near the dams and increased downstream, with the warm- change. Water temperature was not sensitive to the est temperatures occurring in the Santiam River in both presence or absence of a minor point-source inflow at 
 2001 and 2002. In the fall, the releases from the dams typ- Stayton, Oregon.
 ically were warmer than downstream temperatures.


5.	 A scenario to examine the effect of restored riparian 2.	 Portions of both the North Santiam and Santiam Rivers 

exceeded the State of Oregon temperature standard for 

parts of 2001 and 2002. The 2001–02 temperature 

standards were 17.8°C (degrees Celsius) from July 1 

shading and a set of minimum streamflow targets showed 

cooling in the North Santiam in summer and a slight 

warming in the fall. The overall simulated temperature 

through September 14, and 12.8°C from September 15 change for July 1 through November 26, 2001, was 

-0.20°C. through June 30, measured as the 7-day average of daily 

maximum water temperature. Exceedances covered 

larger reaches and a longer time period in 2001, a low 

flow year. In both years, the greatest temperature 

6.	 A scenario to examine the effect of restored riparian 

shading, minimum streamflow targets from the dams, 

and a more-natural seasonal temperature regime from 
2 Modeling Streamflow and Water Temperature in the North Santiam and Santiam Rivers, Oregon 

dam releases showed slight warming in summer and 

significant cooling in fall compared to existing 

conditions. The overall simulated temperature change for 

July 1 through November 26, 2001, was -1.91°C. 

7.	 Although the North Santiam and Santiam Rivers 

transported water from the dams to the Willamette River 

in only a few days in summer, the water temperature 

released from the dams was less important than 

meteorological conditions in determining the water 

temperature at the mouth of the Santiam River. 

Introduction 

The North Santiam and Santiam Rivers are located in the 

Willamette Basin in northwestern Oregon (fig. 1). The North 

Santiam originates in the Cascade Range and flows generally 

westward, passing through Detroit and Big Cliff dams. Near 

Jefferson, Oregon, it joins the South Santiam River to form the 

Santiam River, a tributary of the Willamette River. From the 

dams to the Willamette River, the North Santiam and Santiam 

Rivers are used for recreation, for municipal and industrial 

water supply, for irrigation, and for fish habitat. 

The North Santiam and Santiam Rivers exceed State of 

Oregon water temperature criteria during portions of the year, 

and both are listed for temperature on Oregon’s 2002 303(d) list 

(table 1). The statistical measure used for the temperature criteria is a 7-day moving average of the daily maximum water temperature (7dADM). The temperature criteria for these rivers 

were 17.8°C from July 1 through September 14 and 12.8°C 

from September 15 through June 30, measured as a 7dADM. 

The latter time period has a lower criterion to protect the rivers 

for salmonid spawning. The published 2002 303(d) listing (Oregon Department of Environmental Quality [ODEQ], 2003) has 

a typographical error which mistakenly lists the 17.8°C criterion for part of the North Santiam for July 1 to September 1, 

instead of September 15 (Marilyn Fonseca, ODEQ, written 

commun., 2003). In December of 2003, the ODEQ revised the 

water temperature standard for Oregon. 

In addition to the North Santiam and Santiam Rivers, the 

entire Willamette River and most of its other major tributaries 

up to the first major dams also appear on Oregon’s 2002 303(d) 

list for exceeding temperature criteria. To address the temperature issue, the State of Oregon was required to develop a TMDL 

for water temperature for these rivers by the end of 2003. A 

number of factors can influence river temperature, including 

meteorological conditions such as air temperature and solar 

radiation, riparian shade, point-source inflows from municipal 

or industrial facilities, and outflows from dams. Flow and water 

temperature models were developed as part of this TMDL process to clarify which factors were most important in affecting 

water temperature in these rivers and to provide a quantitative 

framework for heat-load allocations. 

An important consideration in the application of Oregon’s 

temperature standards and development of the TMDL is the 

concept of “system potential” conditions, the hypothetical river 

environment without anthropogenic heat inputs. Anthropogenic 

sources of heat can include loss of riparian vegetation and 

shade, municipal and industrial sources, dams, and diversions. 

If the water temperature standard cannot be met when these 

anthropogenic heat sources are removed (or minimized such 

that their effects cannot be measured), then system potential 

temperatures become the temperature standard. The temperature TMDL, therefore, must include a quantification of both 

current conditions as well as system potential conditions in 

order to set a proper framework for permitted heat discharges 

and future restoration of riparian vegetation areas. 

Previous investigations have studied the temperature and 

streamflow regimes of the North Santiam and Santiam Rivers. 

Harris (1968) included these rivers in a study of water travel 

times in the Willamette Basin. Laenen and Hansen (1985) simulated North Santiam river temperatures using air temperature 

and wind speed as input. Hansen and Crumrine (1991) examined the effects of dams on the North and South Santiam Rivers 

by simulating daily mean water temperature with a one-dimensional model. Laenen and Risley (1997) produced a streamflow-routing model of the North Santiam and Santiam Rivers 

as part of their modeling of the Willamette Basin. 

Site Description, Basin Characteristics, and Hydrology 

The North Santiam River is dammed in its upper reach by 

Detroit and Big Cliff dams (fig. 1), both constructed in 1953. 

Detroit dam is the main storage structure and power generating 

facility, holding approximately 472,880 acre-feet of water at 

full pool (E & S Environmental Chemistry, Inc., and North Santiam Watershed Council, 2002). Big Cliff dam, with only 7,020 

acre-feet of storage, lies downstream of Detroit dam and is primarily a reregulation dam, used to smooth the large daily variation in water releases from Detroit dam due to power generation and avoid large pulses in streamflow downstream. 

Downstream of Detroit and Big Cliff dams, the river flows 

in a canyon where it is joined by tributaries, including Rock 

Creek, until reaching its confluence with the Little North Santiam River. Farther downstream, the topography is more open 

and agricultural uses are common. Near Jefferson, the North 

Santiam River joins the South Santiam River to form the Santiam River, which flows approximately 12 miles before reaching the Willamette River. Water flows from the dams to the 

mouth of the Santiam River in 1 or 2 days, depending on flow. 

The North Santiam and Santiam Rivers from the dams to 

the Willamette are underlain by a complex, thick sequence of 

late Tertiary and Quaternary alluvial and fluvial deposits 

(O’Connor et al., 2001) on Tertiary volcanic and sedimentary 

rocks. The climate of this area is characterized by long, cool, 

rainy winters and warm, and dry summers. The average daily 

maximum temperature at Stayton from 1951 through 2001 was 

17.2°C and the average daily minimum air temperature was 5.6 

°C, with an average annual precipitation of 134.4 cm (centimeters) and an average annual snowfall of 6.4 cm. 
Figure 1. Map of the North Santiam and Santiam Rivers, Oregon, showing the locations of data-collection stations.
4 Modeling Streamflow and Water Temperature in the North Santiam and Santiam Rivers, Oregon 

Table 1. Summary of North Santiam and Santiam Rivers 303(d) temperature listings in 2002 (Oregon Department of 

Environmental Quality [ODEQ], 2003). Temperature criteria have since changed in December of 2003. 

[°C, degrees Celsius; SP, salmonid fish spawning; RR, salmonid fish rearing; RES, resident fish and aquatic life; AN, anadromous fish passage] 

River ODEQ river mile Season Criteria Beneficial uses 

North Santiam 0 to 10 

0 to 26.5 

Santiam 0 to 12 

0 to 12 

July 1 to Sept. 14 17.8°C SP, RR, RES, AN 

Sept. 15 to June 30 12.8°C SP 

July 1 to Sept. 14 17.8°C SP, RR, RES, AN 

Sept. 15 to June 30 12.8°C SP 

Water from the rivers is used for several purposes, including irrigation, municipal and industrial water supply, and recreation. The cities of Gates, Mill City, Mehama, Lyons, Stayton 

and Jefferson lie along these rivers, and the North Santiam 

River is also the source of drinking water for the city of Salem. 

The largest withdrawals from the river, including the Salem 

withdrawal, occur in the vicinity of Stayton. 

In addition to anthropogenic uses of the water, a number 

of fish species live in these rivers. Spring-run Chinook salmon 

(Oncorhynchus tshawytscha) and winter-run steelhead trout (O. 

mykiss) are native to the rivers, and fall-run Chinook, summerrun steelhead, and coho salmon (O. kisutch) have been introduced. These salmonids use the river for spawning, rearing and 

migration. Resident salmonids include cutthroat trout (O. 

clarki) and rainbow trout (O. mykiss) (E & S Environmental 

Chemistry, Inc., and North Santiam Watershed Council, 2002). 

Purpose and Scope 

The objectives of this investigation were to (1) simulate 

hourly and seasonal streamflow and temperature conditions in 

the entire Santiam River and the North Santiam River below 

Big Cliff dam for parts of 2001 and 2002; (2) describe and 

document the model, including construction, calibration, sensitivity, and results; and (3) use the model to quantify current and 

system potential temperature conditions, and better understand 

the processes that influence water temperature in these rivers. 

The study area included the North Santiam River from Big 

Cliff dam to its confluence with the South Santiam River, and 

the entire Santiam River from the mouth of the North Santiam 

River to the confluence of the Santiam River with the Willamette River. A model of the South Santiam River was constructed by ODEQ; streamflow results from that model were 

used as tributary input to the North Santiam-Santiam model. 

Besides the South Santiam, other tributaries included in the 

model were Rock Creek and the Little North Santiam River, 

both on the North Santiam. Anthropogenic inputs included outflows from the wastewater treatment plants for the cities of 

Stayton and Jefferson. Water withdrawals by agricultural and 

municipal users were included in the model. 

In this investigation, USGS personnel collaborated with 

scientists from ODEQ, Portland State University (PSU), and the 

U.S. Army Corps of Engineers (USACE), all of whom were 

working in some capacity to create the tools necessary for 

ODEQ to create a water temperature TMDL for the Willamette 

River and its largest tributaries. The USGS was supported in 

this work through a scientific and financial partnership with the 

Oregon Association of Clean Water Agencies, a consortium of 

municipal agencies. 

Methods 

Model Description 

The North Santiam and Santiam River flow and temperature model was constructed using CE-QUAL-W2 version 3.1 

(Cole and Wells, 2002), a two-dimensional hydrodynamic and 

water-quality model from the USACE. This model is capable of 

simulating water levels, velocities, temperature, and a number 

of water-quality parameters, including dissolved oxygen, algae, 

and organic matter. 

CE-QUAL-W2 originally was designed to simulate water 

quality in reservoirs; more than 400 reservoirs, lakes, and estuaries around the world have been simulated with this model. 

Version 3 of CE-QUAL-W2 includes the capability of modeling sloping river channels in addition to reservoirs. Application 

of this model to steeply sloping rivers like the North Santiam, 

however, is relatively new. 

The model was developed by first constructing a grid 

based on river bathymetry information. Data were collected to 

quantify dam releases, tributary flow and temperatures, withdrawal rates, meteorology, and riparian vegetation. The model 

was first calibrated for flow by comparing simulated flows to 

data collected at monitoring locations along the river, by comparing simulated water travel time with published data, and by 

comparing simulated wetted width of the stream channel to 

available measurements. The model was calibrated for temperature after the water balance was complete by comparing independently collected temperature data with that simulated by the 

model. 

The model was initially calibrated with data from July 1 

through November 21, 2001. The model was confirmed and 
5 

refined with data from April 1 through October 31, 2002. After 

calibration and testing were complete, simulations were run to 

examine the relative effect (sensitivity) of point sources, dam 

release flows, dam release temperatures, and riparian shade. 

Scenarios then were run to examine the effect of restored riparian vegetation, a set of proposed minimum streamflow targets, 

and a more-natural seasonal temperature pattern in dam 

releases. 

Bathymetric Data and the Model Grid 

A CE-QUAL-W2 model grid is made up of a sequence of 

longitudinal model segments, connected along the direction of 

flow. Each segment is divided into horizontal or sloping layers, 

each layer with a defined height. Widths of the layers for each 

segment are defined so that the cross-section of a model segment approximates the river’s channel cross-section. Model 

segments are grouped together in branches, and each branch has 

its own channel slope. A branch or group of branches make up 

a waterbody, the largest entity in CE-QUAL-W2 bathymetry. 

Bathymetric data from a number of sources were used to 

produce the model grid. Measured cross-sections were obtained 

from USGS gaging stations, from a HEC2 flood model of the 

North Santiam, and from a series of cross-sections measured 

along the lower 6 miles of the Santiam River by the USGS. 

River elevation data were taken from USGS 1:24,000 topographic maps. 

ODEQ provided digitized information at 100 ft (foot) 

intervals along the North Santiam and Santiam Rivers derived 

from a grid of digital orthophoto quadrangles. This information 

included longitudinal centerline distance, wetted width, width 

of the near-stream-disturbance zone (zone with no vegetation), 

aspect, elevation, and riparian-vegetation data. The ODEQ data 

were derived from photographs taken on different dates and at 

different river flows, information that had to be considered 

when using the channel-width data. Because simulating the 

wetted width of the river is important in accurately simulating 

river temperatures, the USGS also measured channel widths at 

a number of locations along the rivers on three dates in 2002 

during high-, medium-, and low-flow conditions for calibration 

purposes. 

These bathymetry data were combined, averaged and 

interpolated into a CE-QUAL-W2 grid. In summary, the rivers 

first were divided into six branches based on slope changes. The 

ODEQ aspect data and USGS elevation data were averaged 

every 1,000 ft and a grid was generated to encompass the full 

dimensions of the river channel. Layer heights were set to a uniform 2 ft (0.61 m [meter]). Layer widths for each segment were 

initially determined by interpolating between available measured cross-sections. Extra layers were added to the top of the 

cross-sections to accomodate higher flows. Widths of the extra 

layers were estimated by extrapolating the average change in 

widths between lower layers. Finally, all cell widths were 

adjusted using 1,000-ft averaged ODEQ wetted widths to shrink 

or expand the cell widths between the measured cross-sections. 

Methods 

As part of the model calibration, layer widths were further 

adjusted by comparing the model’s wetted widths to field-measured wetted-channel widths on the same date or on dates with 

similar flows. 

Application of CE-QUAL-W2 to steeply sloping rivers is 

a fairly new use of this model. During the construction of the 

North Santiam and Santiam River model, the CE-QUAL-W2 

development team (Scott Wells [PSU] and Tom Cole 

[USACE]) was adjusting CE-QUAL-W2 to allow for easier 

application to sloping rivers. However, one issue required an 

accommodation to the North Santiam and Santiam model grid: 

CE-QUAL-W2 requires the same surface layer index for all 

segments in each of the model’s waterbodies. The actual water 

level can be above or below the surface layer, but, for accounting purposes, it is always computed in relation to a single surface layer. When the river sloped steeply enough that the channel bottom in some segments was above the surface layer, the 

model considered these segments to be dry and would not run, 

even though the actual water level was well above the channel 

bottom. In order to overcome this issue, small-width (0.1 m) 

cells were added to the bottom of many of the segments to keep 

them from “drying out.” The volume of these small-width cells 

was negligible compared to the water volume in the rest of the 

channel. The major drawback of this approach was that the 

model’s timestep decreased, resulting in longer runtimes. On a 

1.8 Ghz Pentium processor, a model run typically required 

between 12 and 44 hours; 2002 runs were longest due to the 

longer time period simulated and a large storm in April that further slowed the model timestep. Another approach to solve this 

issue might have been to break the model grid into a number of 

smaller waterbodies, as each waterbody can have a different 

surface layer index for accounting purposes. Because changes 

and improvements to CE-QUAL-W2 are made frequently, 

these kinds of accommodations to the model grid are likely to 

be unnecessary in the future. 

The final model grid consisted of 1 waterbody, 6 branches, 

and 310 segments, of which 309 were 1,000 ft long and 1 was 

500 ft, for a total distance of 309,500 ft, or approximately 58.6 

miles (table 2). The model input format requires zero-width 

boundary segments at the start and end of the grid, and two 

boundary segments between branches, bringing the total number of segments in the grid to 322. A schematic of the grid is 

shown in figure 2, and the locations of all included inflows and 

withdrawals are shown in figure 3. 

Temporal Inputs and Shading 

The model requires meteorological data; streamflow and 

water temperature from dam releases, tributaries, and point 

sources; withdrawal rates; and information on shading from 

riparian vegetation. 
6 Modeling Streamflow and Water Temperature in the North Santiam and Santiam Rivers, Oregon 

 Table 2. Summary of the CE-QUAL-W2 model grid used to represent the North Santiam and Santiam Rivers. 

 Distance from Distance 

Branch

headwaters, 

river foot1 

from mouth, 

river mile2 

Number of model 

segments 

Average 

slope River 

1 14,750–35,750 58.1–54.1 21 0.0079 North Santiam 

2 35,750–114,750 54.1–39.4 79 0.0042 North Santiam 

3 114,750–179,750 39.4–27.0 65 0.0032 North Santiam 

4 179,750–236,750 27.0–16.2 57 0.0027 North Santiam 

5 236,750–260,750 16.2–11.7 24 0.0017 North Santiam 

6 260,750–324,250 12.1–0.0 64 0.0011 Santiam 

1 Based on Oregon Department of Environmental Quality (ODEQ) data.


2 Included for reference to USGS topo maps, on which the North Santiam River starts at RM 11.7 and the Santiam ends at RM 12.1.


Figure 2. Schematic of the model grid, with branch boundaries and river miles from the mouth of the Santiam River.

Meteorology 

Meteorological data needed for the model included air 

temperature, dewpoint temperature, wind speed and wind direction, cloud cover, and incident solar radiation. Many of these 

parameters, including air temperature, relative humidity (used 

to calculate dewpoint temperature), wind speed, and wind 

direction were measured hourly at a Remote Automated 

Weather Station (RAWS) site near Stayton (44° 45’ N, 122° 52’ 

W, 155 m elevation). Neither cloud cover nor solar radiation 

were measured at that site, so solar radiation data were obtained 

from the University of Oregon’s Solar Radiation Monitoring 

Laboratory (SRML) Eugene station (44° 03’ N, 123° 04’ W, 

150 m elevation), which used an Ascension Technology Rotating Shadow Band Pyranometer to measure global irradiance. 

Daytime cloud cover was estimated by comparing the calculated theoretical solar radiation and measured solar radiation. 

Equations to calculate theoretical solar radiation and the effects 

of cloud cover were taken from the CE-QUAL-W2 code. Nighttime cloud cover was estimated relative to the day-time cloud 

cover at dusk and dawn. 

Precipitation 

Daily precipitation data were acquired from the Oregon 

Climate Service (OCS), a State repository for climate information. Precipitation data from Stayton were used for the Santiam 

and lower three branches of the North Santiam. Rainfall data 

from Detroit were used for the upper two branches on the North 

Santiam. Precipitation at Detroit was generally higher than that 

at Stayton. 

Precipitation temperature also was required as CE-QUALW2 input, and while this was not directly measured, the daily 

median air temperature at the two precipitation sites was used 

as an estimate of precipitation temperature. 

Streamflow and Stream Temperature 

Big Cliff dam marked the upstream end of the model (RM 

58.1; fig. 3). Data from the USGS gage on the North Santiam 

River at Niagara (USGS station 14181500), just downstream of 

the dam, were used as dam release flow and water temperatures. 

Temperature and streamflow were measured every half-hour at 

this location. 
Methods 7 

Figure 3. Locations of point-source and tributary inflows, withdrawals, and USGS streamflow gages. 
8 Modeling Streamflow and Water Temperature in the North Santiam and Santiam Rivers, Oregon 

The model included three significant tributaries. The Little 

North Santiam River flows into the North Santiam River at RM 

39.2 (fig. 3) and has a USGS gage near its mouth (USGS station 

14182500), which collected streamflow and temperature data at 

half-hour intervals. 

A second, smaller tributary, Rock Creek, flows into the 

North Santiam River upstream of the Little North Santiam 

River, near RM 49.3. It was ungaged, so its streamflow was 

estimated by comparing estimated catchment areas of both 

Rock Creek and the Little North Santiam River, then using that 

ratio to estimate flow from Rock Creek as a proportion of the 

gaged flow of the Little North Santiam River. Stream temperature data were not measured at this site, so the stream temperature of Rock Creek was estimated to be equal to the temperature 

of the Little North Santiam River. 

The third major tributary, the South Santiam River, converges with the North Santiam River to form the Santiam River 

at RM 11.7. Streamflow was not measured at the mouth of the 

South Santiam River, so simulated flows from the ODEQ CEQUAL-W2 model of the South Santiam River (Jim Bloom, 

ODEQ, unpub. data, 2003) were used. For part of the time 

period simulated, half-hourly stream temperature was available 

from a temperature sensor at the mouth of the South Santiam 

River. That temperature monitor was not in the stream all year, 

so the available temperature data at the mouth of the South Santiam River were correlated to data from the USGS temperature 

gage on the Santiam River near Jefferson (station 14189050), 

which had a similar seasonal pattern. That correlation was used 

to estimate temperature in the South Santiam River for times 

when measured data were not available. 

Streamflow in the North Santiam River at Niagara, in the 

Little North Santiam River, and at the mouth of the South Santiam River are shown in figure 4. The flow in the North Santiam 

River at Niagara, just downstream from the dams was controlled by the dams, with fairly constant minimum flows, and 

little daily variation. While larger releases did correspond to 

times of the year with higher precipitation, many of the smaller 

stormflows in the upper basin were absorbed by the reservoir 

and did not appear on this hydrograph. The Little North Santiam 

River hydrograph, on the other hand, was typical of a small 

unregulated river, with a definite response to storms, high flows 

during the rainy winter and low flows during the dry summer. 

The ODEQ-simulated hydrograph from the South Santiam 

River was a mix between the two types of hydrographs. The 

South Santiam River is dammed 35 miles upstream from its 

mouth, but the river also receives flow from unregulated tributaries before reaching the confluence with the North Santiam 

River. 

Stream temperatures in the North Santiam River at Niagara and in the Little North Santiam River are shown in figure 

5. The water temperature at Niagara just downstream from the 

dams had small 24-hour variations and reached an annual maximum later in the year, in late September or October. The temperature of the Little North Santiam River had larger 24-hour 

temperature cycles and maximum summer temperatures in 

August. For much of the year, the temperature at Niagara was 

cooler than that of the Little North Santiam River because the 

releases from Detroit dam are withdrawn from a depth in the 

lake where colder water collects. However, late in the year, the 

water temperature at Niagara was warmer than the Little North 

Santiam and other small unregulated tributaries. The water in 

Detroit Lake stores heat from the summer months and is slower 

to cool than the surrounding streams. 

In addition to the dam releases and tributaries, flow and 

temperature from two municipal wastewater treatment plants 

(Stayton and Jefferson; fig. 3) were included in the model. 

Overall, few sources discharge into these rivers, as the North 

Santiam River is governed by the “Three Basin Rule” (Oregon 

Department of Environmental Quality, 2001) designed to protect the river as a source of drinking water. This rule severely 

restricts discharges into the river. 

Withdrawals 

Information on monthly withdrawals of water from the rivers by municipal and agricultural users was obtained from the 

Oregon Water Resources Department (OWRD) Water Use 

Reporting Database. Locations of the withdrawals included in 

the model are shown in figure 3. The withdrawals reported to 

OWRD are the total monthly withdrawals, including both consumptive and nonconsumptive uses. Discussions with representatives of the larger water users in the basins allowed a better 

estimate of consumptive withdrawals (Libby Barg, City of 

Salem, and Larry Trosi, Santiam Water Control District, oral 

commun., 2003) which were used in the model. 

Riparian Shading 

The representation of riparian vegetation for the shading 

component of the model was constructed using a technique 

modified from a method developed by Robert Annear (PSU), 

which used ODEQ-digitized vegetation information and the 

model bathymetry. For each of nine ODEQ vegetation zones 

along each river bank, the vegetation top elevation was calculated from tree height and thalweg elevation. Then the distance 

from the stream centerline to each vegetation zone, and a vegetation density for each zone, were calculated. The zone casting 

the longest shadow over the river was determined for each bank. 

Finally, the data were averaged longitudinally to correspond to 

the CE-QUAL-W2 model segment length. Final shading information was input to a CE-QUAL-W2 shade file, including 

Julian day, vegetation height, vegetation density, topographic 

shade inclination angles, and estimated leaf-out date and leaffall date. The original method accounted for shading from only 

one vegetation zone, which could underestimate shading. The 

method was modified in an attempt to better account for shading 

from all zones. This approach resulted in a better estimate of the 

vegetation density needed by the model. 
Methods 9 

Figure 4. Streamflow in (A) the North Santiam River at Niagara (USGS station 14181500), just downstream from the dams, (B) the Little North 

Santiam River (USGS station 14182500), and (C) the South Santiam River for July 2001 through October 2002. Data in (A) and (B) were measured; 

data in (C) were from the Oregon Department of Environmental Quality model of the South Santiam River. 
10 Modeling Streamflow and Water Temperature in the North Santiam and Santiam Rivers, Oregon 

Figure 5. Water temperatures in the North Santiam River at Niagara (USGS station 14181500), just downstream from the dams, and at the Little North Santiam (USGS station 14182500) for July 2001 through October 2002. 

In addition to the shade file based on the ODEQ digitized 

data (current conditions), shade files were prepared to represent 

the effect of no riparian vegetation and the effect of “system 

potential” vegetation. System potential vegetation is a representation of mature riparian vegetation with little natural disturbance and without anthropogenic influence. System potential 

vegetation characteristics were estimated by ODEQ by analyzing geology, historic vegetation, ecoregions and soils (ODEQ, 

unpub. data, 2003). Calculated vegetative shade under current 

and system potential conditions along the rivers on August 1, 

2001, is shown in figure 6. Topographic shading was included 

in all model runs. 

Ground Water and Ungaged Tributaries 

The model allows for input of “distributed” tributaries that 

represent ungaged tributaries and inflows of ground water. 

Flows from a distributed tributary are spread out along an entire 

branch of the model rather than discharging at a specific location. Because neither ground-water inflow/outflow nor ungaged 

tributaries were monitored, the use of a distributed tributary was 

an integral part of the water balance calibration. The relative 

importance and application of these distributed tributaries is 

discussed further in the calibration section of this report. 

Temperatures of these distributed tributaries were estimated to be a mix of ground-water inflow and ungaged tributaries. Ground-water temperature was estimated as 11°C for the 

upper two branches and 11.5°C for the lower four branches, 

based on annual mean air temperature at Detroit and Stayton, 

respectively. Ungaged tributaries were assigned a temperature 

equal to that of the Little North Santiam River. 

Calibration Data 

Calibration data consisted of a set of measured streamflow, 

travel time, wetted channel width, and temperature data along 

the two rivers. These data were compared to model output from 

the segment(s) corresponding to the measurement location to 

evaluate model performance. 

Half-hourly streamflow data were obtained from two 

USGS gages. One gage was located on the North Santiam River 

at Mehama (USGS station 14183000) just downstream of the 

confluence with the Little North Santiam River. The other gage 

was located on the Santiam River at Jefferson (USGS station 

14189000). Data were available for all the time periods simulated. 

Dye studies were conducted by Harris (1968) to determine 

water travel times in 11 separate reaches of the North Santiam 

and Santiam Rivers. To compare these travel times to the 

model, a conservative tracer was simulated in the model at various flow conditions in 2001 and 2002, and the location of the 

tracer peak was tracked as it traveled downstream through the 

model segments. The time required for the simulated tracer 

peak to travel through segments corresponding to Harris’ 

defined reaches and an average flow from these same segments 

were calculated from the model output. 

USGS personnel measured wetted river widths with a laser 

rangefinder at 24 locations on the North Santiam River and 3 

locations on the Santiam River at 3 times in 2002: April 9–10, 

June 4, and August 6. These data captured river widths at high, 

medium and low flow conditions, respectively. These fieldmeasured widths were compared to simulated wetted width on 

the same dates. 

Simulated water temperatures were compared to measured 

data at 16 locations in 2001 and at 5 locations in 2002. Information on the locations, corresponding model segments, source, 

and collection dates of these monitoring stations is summarized 

in table 3. 
Model Calibration 11 

Figure 6. Vegetative shading for current conditions and system potential on August 1, 2001, for the North Santiam and Santiam Rivers. Shading is 

calculated as the percentage of the solar radiative flux that is blocked over the course of the entire day. 

Model Calibration 

Water Balance 

The water-balance calibration was completed by comparing measured calibration data to model output and adjusting 

model parameters to achieve agreement between the two. This 

was an iterative process, using flows, wetted widths, and traveltime calibration data. Here, the results for each of these comparisons are presented sequentially. 

Flow 

After an initial simulation using 2001 data, the comparison 

of simulated flow to measured flow at the two USGS gages at 

Mehama and Jefferson demonstrated that the model was not 

accounting for enough flow. While each of the three major tributaries were included in the model, a number of small ungaged 

tributaries exist along the rivers. Some uncertainty also was 

inherent in the flows on the lower part of ODEQ’s South Santiam River model because no nearby gages existed with which 

to calibrate flow in the lower reach of that river. Also, groundwater exchange with the river was not measured. The sum of all 

of these unmeasured and uncertain flows were estimated using 

a distributed tributary inflow to achieve a reasonable agreement 

between measured and simulated flows. 

Upstream of Mehama (RM 38.7) in 2001, the largest differences in flow occurred during precipitation events; a distributed tributary inflow was added to the upper two model 

branches to correct for the extra flow. These ungaged inflows 

were assumed to be a mix of 70 percent surface inflows with a 

temperature of the Little North Santiam River and 30 percent 

ground-water inflows with a temperature of 11°C. 

At the Jefferson gage on the Santiam River (RM 9.7), the 

difference between simulated and measured flow was more 

constant through the time period simulated. The missing 

inflows were apportioned equally between the North Santiam 

and South Santiam Rivers. On the North Santiam River, the 

flows were distributed uniformly to the model branches 

between Mehama and the end of the river according to branch 

length. Temperatures were estimated by assuming a mix of 50 

percent ground-water inflow at 11.5°C and 50 percent ungaged 

tributaries with the same temperature as the Little North Santiam River. The water balance after these adjustments for 2001 

is shown in figure 7. The missing flows apportioned to the 

South Santiam River were added to the simulated flows from 

ODEQ’s model, and temperatures were not changed. 

After calibrating the model with 2001 data, the model was 

tested with 2002 data. In the 2002 water balance, some unaccounted-for flows again were present during storm events. 

These flows were attributed to ungaged inflows and included as 

distributed tributaries, similar to the method used in 2001. 
12 Modeling Streamflow and Water Temperature in the North Santiam and Santiam Rivers, Oregon 

Table 3. Locations of monitors used to calibrate water temperature in the North Santiam and Santiam Rivers. 

[SWC, Santiam Watershed Council; USGS, United States Geological Survey; SECOR, SECOR International, Inc.; n/a, not available] 

Approximate 

river mile 

Model 

segment Latitude/Longitude Source 

Data availability (month

1

2001 

/day) 

2

2002 

43.6 81 44.76683/122.53149 SECOR 7/1–11/3 6/11–10/7 

42.1 89 44.76836/122.55969 SWC 7/1–9/29 

38.7 110 44.7889/122.6167 USGS (gage 14183000) 7/1–11/21 4/1–10/31 

35.6 126 44.08389/122.65931 SWC 7/1–9/28 

35.5 126 44.77828/122.67694 SWC 7/1–9/10 

31 150 44.79110/122.74997 SECOR 7/1–9/25 

28.7 167 n/a SECOR 7/1–9/25 

24.3 186 44.77027/122.84771 SECOR 6/11–7/22 

23 193 44.75333/122.85792 SWC 7/1–9/26 

22.3 196 44.75447/122.87389 SWC 7/1–9/26 

15.7 234 44.72133/122.95650 SWC 7/1–9/26 

14.6 240 44.70863/122.97207 SECOR 8/2–11/7 6/11–10/7 

11 263 44.69528/123.01650 SWC 7/6–10/10 

9 274 44.72339/123.01672 SWC 7/6–10/10 

6.1 289 44.7389/123.0486 USGS (gage 14189050) 7/1–10/31 4/1–10/31 

3.35 303 44.74747/123.09131 SWC 7/6–10/3 

3.25 304 44.74686/123.09467 SWC 7/6–10/3 

1

 Dates modeled in 2001 were 7/1 through 11/21. 

2

 Dates modeled in 2002 were 4/1 through 10/31. 

At Mehama, for 2001 and 2002, the distributed tributary 

flows were generally less than 3 percent of the total flows. During spring and winter storms, the distributed tributary flow was 

larger and could be up to 18 percent of the total flow. At Jefferson for 2001 and 2002, the distributed tributary flows generally 

were between zero and 10 percent of the total flows. During 

spring and winter storms, distributed tributary flows accounted 

for up to 22 percent of the total flow. In addition, during low 

flow in 2002 only, the measured flow at the upstream gage at 

Niagara was higher than that further downstream at Mehama, 

necessitating the inclusion of a withdrawal of water between 

those two locations. No withdrawals of that magnitude were 

recorded by OWRD, and this phenomenon is unusual. Gage 

data were double-checked, but no measurement errors were 

found. The discrepancy may represent an unreported withdrawal from the river, pumping from ground water near the 

river, or a natural loss of river water to ground water. The final 

2002 water balance is shown in figure 7. 

Channel Width 

Field-measured wetted-channel widths were compared to 

simulated wetted-channel widths, and results of that comparison were used to adjust layer widths in the model grid. A comparison of the final wetted-channel widths simulated by the 

model and those measured in the field by USGS on the same 

date, August 6, 2002, is shown in figure 8. The USGS measurements were at discrete points along the river, while the simulated widths represent averages for 1000-ft long segments. The 

ODEQ channel widths in figure 8 are included for comparison, 

and while they were digitized at a relatively fine interval of 100 

ft, the dataset includes channel widths on different dates and at 

different flows. The final model bathymetry was able to represent the wetted channel widths of the rivers at different flows 

with sufficient accuracy for the purposes of this investigation. 

Travel Times 

Simulated travel times at different flows for model simulations in 2001 and 2002 were compared to measured travel times 

for a tracer peak in the reaches measured by Harris (1968) (fig. 

9). The simulated travel times compare well with the measured 

values, but in some reaches the slopes of simulated and measured travel times show a difference. The slopes of the simulated travel time versus discharge data were similar for all 11 

reaches. Dunne and Leopold (1978) show that for stations along 

a river system, the slopes of these curves should be similar, 

while their ordinate position may differ. On the other hand, 
Figure 7. Comparison of measured streamflow at the USGS gages at Mehama (USGS station 14183000) and Jefferson (USGS station 14189000) to calibrated model outp
14 Modeling Streamflow and Water Temperature in the North Santiam and Santiam Rivers, Oregon 

Figure 8. Comparison of USGS field-measured channel width to Oregon Department of Environmental Quality digitized channel width and to wetted width 

from the calibrated model. The USGS field-measured data and model data output are for the same date (August 6, 2002) and flow, while the ODEQ widths are 

from a range of dates and flows. 

results from the Harris (1968) travel time study show a range in 

slopes. The reason for this is not clear, but it may be related to 

the fact that the North Santiam River channel becomes braided 

in some portions of the reach below Mehama (RM 38.7). Routing of the river water through a system of smaller side channels 

would probably change water travel time behavior compared to 

the one-channel representation of the model. The travel time 

comparison, while certainly not perfect, was deemed to be sufficiently accurate for the needs of this study. 

Water Temperature 

After the water-balance calibration was complete, very little calibration was needed to simulate water temperatures accurately. A comparison of daily average and hourly measured and 

simulated temperature is shown in figure 10 for selected stations in 2001 and in figure 11 for all stations in 2002. Because 

the daily temperature variations were large, a seasonal comparison between simulated and measured temperature is shown 

using daily average temperatures. Hourly water temperatures 

are shown for a 2-month period. Error statistics, including mean 

absolute error (MAE) and root mean square error (RMSE), for 

the comparison between the hourly model output and measured 

data for the 16 temperature stations are shown in table 4. These 

MAEs ranged from 0.41°C to 1.02°C and the RMSEs ranged 

from 0.50°C to 1.16°C. Similar error statistics for the 7dADM, 

the 7-day moving average of the daily maximum water temperature, used in the water temperature standard, are shown in table 

5. These MAEs ranged from 0.15°C to 1.05°C and RMSEs 

ranged from 0.21°C to 1.14°C. The smoothing effect of the 

7dADM, and the fact that the model was more successful at 

matching daily maxima compared to daily minima, made for a 

better fit. 

Differences between measured and simulated water temperatures can be due to several factors. First, the measurements 

and model output are at different scales, as temperature measurements were from discrete points in the river, while model 

output was laterally and vertically averaged through the watercolumn and longitudinally averaged through each 1,000-ft segment. 

Temperature monitors also can be affected by local environmental conditions. The temperature monitor at RM 9 (not 

included in fig. 10 or 11) in the Santiam River appeared to show 

local effects. From early July through mid-August, the measured and simulated hourly temperature cycles were of similar 

magnitude. Thereafter, the measured hourly temperature signal 

became increasingly damped, until by early October, very little 

daily variation remained in the measured temperature. Measurements both upstream and downstream of this station did not 

show a similar decrease in the magnitude of the daily temperature cycle. The monitor may have become covered by sediment 

or algae, buffering it from daily heating and cooling cycles. 

Some of the largest differences between measured and 

simulated water temperature on the North Santiam River 

occurred in 2002 at RM 38.7, just downstream of the inflow of 

the Little North Santiam River. From mid-May to mid-June, the 

measured temperature was higher than the simulated temperature. The most plausible explanation for this is that the Little 

North Santiam River may not have completely mixed into the 
Model Calibration 15 

Figure 9. Comparison of simulated travel times to field measurements by Harris (1968). Data represent the velocity of the peak concentration of an injection of a nonreactive dye tracer. 
16 Modeling Streamflow and Water Temperature in the North Santiam and Santiam Rivers, Oregon 

Figure 10. Daily average and hourly comparison of model output to measured temperature at calibration stations in 2001. River mile (RM) locations 

are noted: (A) river mile 38.7, (B) river mile 27.7, (C) river mile 22.3, (D) river mile 11, (E) river mile 6.1, (F) river mile 3.25. 
Model Calibration 17 

Figure 10. Daily average and hourly comparison of model output to measured temperature at calibration stations in 2001. River mile (RM) locations 

are noted: (A) river mile 38.7, (B) river mile 27.7, (C) river mile 22.3, (D) river mile 11, (E) river mile 6.1, (F) river mile 3.25—Continued. 
18 Modeling Streamflow and Water Temperature in the North Santiam and Santiam Rivers, Oregon 

Figure 11. Daily average and hourly comparison of model output to measured temperature at calibration stations in 2002. River mile (RM) locations 

are noted: (A) river mile 43.6, (B) river mile 38.7, (C) river mile 24.3, (D) river mile 14.6, (E) river mile 6.1. 
Model Calibration 19 

Figure 11. Daily average and hourly comparison of model output to measured temperature at calibration stations in 2002. River mile (RM) locations 

are noted: (A) river mile 43.6, (B) river mile 38.7, (C) river mile 24.3, (D) river mile 14.6, (E) river mile 6.1—Continued. 

North Santiam River; the Little North Santiam River joins the 

North Santiam River on the north bank (the right bank, looking 

downstream), the same bank where the temperature monitor is 

located. At that time, the temperature of the tributary was 

higher than that of the North Santiam River, and tributary 

inflows were relatively high. Prior to this time period, tributary 

and main-stem temperatures were similar, while after July, the 

flow from the Little North Santiam River was small and less 

significant. This explanation was corroborated through an 

examination of measured temperature cross-sections during 

these time periods. 

Overall, the largest differences between measured and 

simulated hourly temperatures in both years were in the lower 

portions of the Santiam River. On an hourly timescale, the 

measured temperature signal was damped compared to the 

simulated temperature, and this effect increased with increasing proximity to the confluence of the Santiam River with the 

Willamette River. One possible explanation for this is that the 

thick gravels that underlie this portion of the river allowed a 

large amount of hyporheic flow. Interaction of the river water 

with ground water would have buffered the daily temperature 

variation. The lower reach of the Santiam River is known to 

have a large amount of hyporheic exchange (Hinkle and others, 

2001; Laenen and Bencala, 2001). The direction of the 

exchange was found to alternate between ground-water discharge to the river and river-water flow into the subsurface in 

the lower Santiam River, depending on flow and channel characteristics. 

The water temperature standard for these rivers is based 

on a 7dADM water temperature. This information is shown for 

the calibrated model for the North Santiam River and Santiam 

River in both 2001 and 2002 in figure 12. Each point on these 
20 Modeling Streamflow and Water Temperature in the North Santiam and Santiam Rivers, Oregon 

 Table 4. Goodness of fit statistics for hourly water temperature (in degrees Celsius). 

River 

Approximate 

river mile 

Model 

segment 

2001, mean 

absolute 

error 

2001, root 

mean square 

error 

2002, mean 

absolute 

error 

2002, root 

mean square 

error 

North Santiam 43.6 81 0.50 0.60 0.43 0.66 

42.1 89 0.67 0.86 

38.7 110 0.57 0.68 0.56 0.70 

35.6 126 0.71 0.86 

35.5 126 0.80 0.98 

31 150 0.67 0.81 

28.7 167 0.58 0.70 

24.3 186 0.83 1.09 

23 193 0.76 0.93 

22.3 196 0.74 0.91 

15.7 234 0.58 0.73 

14.6 240 0.65 0.81 0.78 1.01 

Santiam 11 263 0.41 0.50 

†9 274 0.55 0.66 

6.1 289 0.86 0.96 0.84 0.98 

3.35 303 0.98 1.12 

3.25 304 1.02 1.16 

†Statistics for this location computed using only data from before sensor became buried. 

Table 5. Goodness of fit statistics for 7dADM water temperature (in degrees Celsius). 

[7dADM, 7-day average of daily maximum] 

River 

Approximate 

river mile 

Model 

segment 

2001, mean 

absolute 

error 

2001, root 

mean square 

error 

2002, mean 

absolute 

error 

2002, root 

mean square 

error 

North Santiam 43.6 81 0.47 0.59 0.65 0.82 

42.1 89 0.51 0.59 

38.7 110 0.27 0.32 0.49 0.63 

35.6 126 0.35 0.42 

35.5 126 0.24 0.27 

31 150 0.44 0.50 

28.7 167 0.44 0.53 

24.3 186 0.32 0.41 

23 193 0.55 0.61 

22.3 196 0.39 0.45 

15.7 234 0.32 0.44 

14.6 240 0.49 0.62 0.59 0.67 

Santiam 11 263 0.15 0.21 

†

9 274 0.56 0.62 

6.1 289 0.69 0.77 0.79 0.95 

3.35 303 1.05 1.14 

3.25 304 1.04 1.14 

†

Statistics for this location computed using only data from before sensor became buried.
Model Calibration 21 

Figure 12. Simulated 7-day moving average of daily maximum water temperature in degrees Celsius 

for 2001 and 2002. A time series of the 7-day moving average of air temperature shows the correlation of 

temporal patterns in both datasets. 
22 Modeling Streamflow and Water Temperature in the North Santiam and Santiam Rivers, Oregon 

graphs uses a color to represent the 7-day moving average of 

daily maximum temperature for a particular location and time. 

During summer, the water just below the dams (right side of figure) was generally the coldest in the whole system. Discharges 

from Detroit Lake were drawn from deeper, colder water during 

summer. Late in the year, in October, the pattern reversed, and 

the outflow from the dam was warmer than other parts of the 

North Santiam River downstream. At this time of year Detroit 

Lake is drawn down, and the reservoir is discharging water with 

stored summer heat. Overall, the warmest temperatures in the 

system were in the Santiam River during the summer, often 

reaching well above 20°C. Water temperatures in 2001, a lowflow year, were warmer further upstream and for a longer time 

period than in 2002, a more typical flow year. 

A strong water temperature cycle of approximately a 2­

week timescale is obvious in both 2001 and 2002. Air temperature showed similar temporal cycles in both years. The air temperature and water temperature cycles seen in figure 12 are 

indicative of the strong influence of meteorological factors in 

controlling water temperature. Releases from the dams provide 

an initial temperature to a parcel of water as it travels through 

the system, but the influence of the release temperature diminishes as the water travels downstream. Generally, water travels 

through the system in 1 or 2 days, depending on flow. In that 

short time, 7dADM water temperatures can be warmed by over 

10°C in summer from the dams to the mouth of the Santiam 

River. Tributary inflows did not have a large influence on 

7dADM water temperatures in this system. The location of the 

inflows of Rock Creek, the Little North Santiam River and the 

South Santiam River are noted in figure 12, and the changes in 

7dADM water temperatures at the mixing locations of these 

tributaries is small. 

Considering the water temperature standards of 17.8°C in 

summer and 12.8°C in winter (table 1), the rivers exceeded the 

water temperature standards for long periods in summer and 

fall, as shown in figure 13. In these graphs, simulated temperatures in the Santiam River and North Santiam Rivers were compared to the 17.8°C standard from July 1 through September 14, 

and to the 12.8°C temperature standard from September 15 

through June 30. In parts of 2001 and 2002, most or all of these 

rivers exceeded the standards. Areas of greatest exceedance 

typically occurred near the mouth of the Santiam River or when 

the standard switched from 17.8°C to 12.8°C in fall. The lowflow year, 2001, had longer reaches with higher exceedances 

than 2002. 

Sensitivity Analysis 

To determine the relative effect of individual model 

parameters or dam releases on simulated river temperatures, a 

\series of sensitivity tests was run by taking the calibrated model 

and adjusting one input parameter or condition at a time. Sensitivity runs were conducted for 2001 only using the North 

Figure 13. Difference between the simulated 7-day moving average of 

daily maximum water temperature and the applicable water temperature 

standard in degrees Celsius. The temperature standard was 17.8°C from 

July 1 through September 14, and 12.8°C for the rest of the year. (Note that 

the temperature standard has since changed. See Appendix 1.) 
Santiam River part of the model. Parameters were changed as 

follows: 

1. Removal of the point source at Stayton 

2a. Dam release temperature increased by 5°C 

2b. Dam release temperature decreased by 5°C 

3a. Air temperature increased by 5°C 

3b. Air temperature decreased by 5°C 

4a. Riparian vegetation at system potential 

4b. No riparian vegetation 

5a. Dam release flow increased by 20 percent 

5b. Dam release flow decreased by 20 percent 

The greatest overall change in river temperature was produced by changing the temperature of the dam releases. However, the magnitude of that change decreased significantly with 

distance downstream. The effect of changing air temperature 

increased with distance from the dams. Changes to riparian 

shade, which affects the amount of solar radiation reaching the 

stream, produced small temperature changes along most of the 

river. Changes to dam release flows produced both warming 

and cooling in each simulation, depending on the time of year. 

The point source at Stayton was small enough that its removal 

had no effect on river temperature. Further details of the results 

from the sensitivity analyses are given below. 

Point Sources 

The base model was adjusted by removing the wastewater 

treatment plant point-source input at Stayton on the North 

Santiam at river mile 27.5. This produced no change (<0.01°C) 

in the simulated 7dADM water temperature from July 1 to 

November 26, 2001 (table 6). The point source at Stayton was 

small compared to the flow in the river, and effluent temperatures were similar to river temperatures. The North Santiam 

River channel is braided in this part of the river, however, and 

Stayton discharges only into the smaller north channel. The 

effect of the effluent in a smaller channel may be more significant, as the current model considers all flow to occur in only one 

channel. Further analysis regarding the effects of this pointsource discharge on its receiving water may be merited. 

Dam Release Temperature 

The base model was adjusted by first increasing and then 

decreasing the dam release water temperatures at Big Cliff dam 

by 5°C. These changes produced a measurable change in water 

temperatures throughout the North Santiam River for the entire 

time period simulated (fig. 14 and table 6). 

The 5°C increase in dam release temperatures produced an 

average 7dADM temperature change of +2.74°C for July 1 

through November 26, 2001 (table 6). The magnitude of that 

temperature change was greatest near the dams (fig. 14) with a 

+4°C to +5°C increase in temperature. The effect decreased 

Sensitivity Analysis 23 

Figure 14. Difference in water temperature between the 

base model and the model with dam release temperatures 

(A) increased by 5°C and (B) decreased by 5°C, using the 7-day 

moving average of daily maximum water temperature in degrees 

Celsius. The gray color zone includes all temperature differences 

within 0.05°C of 0°C. 

with downstream distance as the river had more time to 

exchange heat with its surroundings. At the mouth of the North 

Santiam River, the temperature change had been reduced to 

between +1°C and +3°C, depending on the time of year, showing that more than half of the temperature increase had dissipated. The fact that this change is dissipated in only about 1.5 

days of travel time attests to the rapid exchange of heat between 

the river and the atmosphere. The seasonal variation in the tem­
24 Modeling Streamflow and Water Temperature in the North Santiam and Santiam Rivers, Oregon 

Table 6. Summary of the model sensitivity analysis for the North Santiam River in 2001. 

[Values are averages of simulated 7dADM water temperatures compared to the base case for all segments on all days in each month. 7dADM, 

7-day average of daily maximum; °C, degrees Celsius] 

Average change in 7dADM water temperature, °C Overall 

Parameter Change July August September October November July–November 

Point sources No point <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 

sources 

Inflow temperature +5°C +2.75 +2.84 +2.86 +2.70 +2.43 +2.74 

-5°C -2.83 -2.94 -2.96 -2.77 -2.47 -2.82 

Air temperature +5°C +0.72 +0.82 +0.79 +0.67 +0.43 +0.70 

-5°C -0.69 -0.78 -0.76 -0.64 -0.41 -0.67 

Riparian shade System -0.21 -0.26 -0.28 -0.09 -0.03 -0.18 

potential 

No vegeta- +0.31 +0.38 +0.46 +0.19 +0.09 +0.30 

tive shade 

Inflows +20% -0.33 -0.28 -0.05 +0.11 +0.09 -0.09 

-20% +0.42 +0.34 +0.07 -0.22 -0.10 +0.12 

perature change was small, with the greatest monthly average 

change of +2.86°C in September and the smallest, +2.43°C, in 

November. After mid-October, flows from the unregulated tributaries, Rock Creek and the Little North Santiam River, became 

significant (fig. 4B), causing obvious cooling to the warmer 

upstream water. 

Imposing a 5°C decrease in dam release temperatures produced an average 7dADM temperature change of -2.82°C on 

the North Santiam River between July and November 2001. The 

spatial and seasonal patterns of the decrease in temperature 

were similar to those for the increase in dam release temperatures. The greatest decrease in temperature was -2.96°C in September, and the smallest decrease, -2.47°C, was in November. 

Note that temperature changes downstream of the Little North 

Santiam River in November 2001 were smaller (less affected by 

dam releases) because of higher flows from the Little North 

Santiam River Basin. 

Air Temperature 

The relative effect of air temperature on 7dADM water 

temperature was examined by increasing and then decreasing 

air temperature by 5°C in separate model simulations. The 

results of these sensitivity tests are shown in figure 15 and table 

6. 

Increasing air temperature produced a +0.70°C overall 

average change in water temperature in the North Santiam 

River from July 1 through November 26, 2001. The spatial pattern was opposite of that of changing dam release temperatures. 

The water temperature change was negligible just downstream 

of the dams, and increased with distance away from the dams. 

This result makes sense because time must pass in order to 

allow a change in air temperature to affect the simulated water 

temperatures. No change occurred near the dams because an 

insufficient amount of time had elapsed to observe an effect. 

The greatest monthly average temperature change was +0.82°C 

in August, and the smallest change was +0.43°C in November, 

due to higher flows and shorter travel times. 

Decreasing air temperature produced a -0.67°C overall 

7dADM water temperature change. The spatial pattern of the 

change in the North Santiam River was similar to that for the 

increase in air temperature. The decrease in temperature was 

greatest in August, -0.78°C, and least in November, -0.41°C. 

Riparian Vegetation 

The base model was adjusted by first considering systempotential riparian vegetation, and then examining the effect of 

removing all riparian vegetation. Topographic shading information, a separate model input, was unchanged in all of these 

shade sensitivity analyses. The results of the riparian-vegetation 

sensitivity analysis are presented in figure 16 and table 6. 

System potential shade, a mature vegetative shade without 

anthropogenic influence and little natural disturbance, cooled 

the 7dADM water temperature on average by -0.18°C between 

July 1 and November 26, 2001. The change was fairly consistent spatially, producing a change of between 0°C and -1°C 

throughout the North Santiam River, with the largest changes 

occurring at the most downstream site. The greatest cooling 

occurred in September, with a -0.28°C average change, while 

the temperature change was very small in November, -0.03°C. 

The smaller temperature changes in November are attributable 
Sensitivity Analysis 25 

Figure 15. Difference in water temperature between the 

base model and the model with air temperature (A) increased 

by 5°C and (B) decreased by 5°C, using the 7-day moving average 

of daily maximum water temperature in degrees Celsius. The gray 

color zone includes all temperature differences within 0.05°C of 0°C. 

Figure 16. Difference in water temperature between the 

base model and the model (A) with system potential shade and 

(B) without any riparian shade, using the 7-day moving average of 

daily maximum water temperature in degrees Celsius. The gray 

color zone includes all temperature differences within 0.05°C of 0°C. 
26 Modeling Streamflow and Water Temperature in the North Santiam and Santiam Rivers, Oregon 

to the decreased importance of solar radiation (and therefore 

shade) at that time of year, the loss of leaves from some riparian 

vegetation in the fall, and the higher flows and corresponding 

shorter travel times. System potential vegetation information 

was provided by ODEQ (Oregon Department of Environmental 

Quality, unpub. data, 2003). 

Removing all riparian shade warmed the river over almost 

the entire model reach. The overall average temperature change 

was +0.30°C, with the greatest monthly change in September, 

+0.46°C, and the smallest in November, +0.09°C. Clearly, the 

effect of riparian shading in the North Santiam River is not as 

important to the temperature of the river as some other influences, such as dam release temperature or meteorological factors. 

Dam Release Flow

 The base model was adjusted by increasing and then 

decreasing the dam release flows at Big Cliff dam by 20% in 

separate runs. Results are presented in figure 17 and table 6. 

The average 7dADM water temperature change for 

increased dam release flows was only -0.09°C from July 1 

through November 26, 2001, but this effect showed fairly significant seasonal differences. In summer, when outflows from 

Detroit Lake were relatively cool, a flow increase cooled much 

of the North Santiam River. Later in the year, when the outflows 

from the lake were relatively warm, increasing those flows 

warmed much of the simulated reach. The water temperature 

change was -0.33°C in July and +0.11°C in October. 

The seasonal effects of changing dam release flows could 

be caused by both travel time and volume effects. For instance, 

larger outflows from the dams travel more quickly downstream 

and have less time to be affected by meteorological conditions. 

The larger volume and greater depth of an increased outflow 

also would be less susceptible to heating or cooling by meteorologic conditions. 

Decreasing the dam release flows (fig. 17B) produced the 

opposite effects. In summer, a decrease in dam release flow 

warmed the river, and in fall it cooled the river. The temperature 

change was +0.42°C in July and -0.22°C in October. The average water temperature change was +0.12°C from July 1 through 

November 26, 2001, for decreased dam release flows. Smaller 

outflows from the dams would be more affected by meteorological conditions compared to the base case, due to longer travel 

times and the presence of less water to absorb inputs of solar 

radiation. 

Several other authors have examined the sensitivity of 

input parameters to Willamette River tributary water-temperature models. Laenen and Hansen (1985) examined the sensitivity of simulated water temperature in the North Santiam River 

downstream of the dams to wind speed, dam releases, channel 

width and area, tributary inflows and withdrawals, and equilibrium temperature—the temperature that a waterbody would 

move towards at steady state. Of those influences, they 

Figure 17. Difference in temperature between the base 

model and the model with dam release flows (A) increased 

by 20 percent and (B) decreased by 20 percent, using the 7-day 

moving average of daily maximum water temperature in degrees 

Celsius. The gray color zone includes all temperature differences 

within 0.05°C of 0°C. 

found that equilibrium temperature and wind speed affected 

water temperature the most. Hansen (1988) evaluated the sensitivity of a temperature model of the McKenzie River by varying 

equilibrium temperature, wind speed, upstream inflow, topwidth, cross-sectional area and tributary inflows. Of those 

parameters, equilibrium temperature was found to produce the 

greatest effect on water temperature, followed by discharge and 

top-width. 
Simulation of System Potential Conditions 

The calibrated model was used to examine two scenarios 

designed to provide insight into the behavior of these rivers at 

system potential. Both of the scenarios used system potential 

riparian vegetation from ODEQ and dam release flows from 

USACE operational modeling of flows from the dams to meet 

proposed National Oceanic and Atmospheric Administration 

(NOAA) Fisheries minimum flow targets (fig. 18). These flow 

targets were designed to improve fish habitat downstream from 

the dams. A second scenario additionally replaced measured 

temperatures released from the dams with an estimated, morenatural seasonal temperature regime (fig. 19). This temperature 

regime was estimated by mixing the three major tributaries to 

Detroit Lake: the North Santiam River (USGS gage 14178000), 

Breitenbush River (14179000) and Blowout Creek (14180300), 

weighted according to their measured flows. The mixing did not 

take travel time differences into account, resulting in an incorrect daily temperature variation; therefore, a daily average temperature input was used for this analysis. This estimate of a 

more-natural seasonal temperature regime did not take into 

account any anthropogenic disturbances upstream of the dam 

that might have increased the measured temperatures. 

System-Potential Vegetation with Proposed NOAA 

Fisheries Target Flows 

The first scenario was designed to examine the effect of 

combined system potential shade and proposed Detroit dam 

minimum outflow requirements on the temperature of the North 

Santiam River. The new USACE modeled releases for 2001 

were between 10% and 73% higher than the flows from the base 

model, depending on the date. The resulting changes in temperature compared to the base-calibrated model are shown in figure 

20A. The pattern of temperature change was very similar to that 

seen in the sensitivity run of increasing flows by 20% (fig. 17A). 

Simulation of System Potential Conditions 27 

Cooler temperatures were predicted from July through October, 

and slightly warmer temperatures were predicted through most 

of the river from early October through mid-November. Just as 

in the flow-sensitivity analysis, these effects are mainly a function of changes in travel time. Higher flows during a time when 

the river is gaining heat means that less time is available for that 

gain, resulting in cooler water relative to the base case. August 

had the most cooling with an average temperature drop of 

-0.47°C (table 7), and October showed the most warming with 

an average temperature increase of +0.18°C. The overall temperature change for this period in 2001 was -0.20°C. 

System-Potential Vegetation with Proposed NOAA 

Fisheries Target Flows and a More-Natural Seasonal 

Temperature Regime in Dam Releases 

This scenario was similar to the first, but also replaced the 

measured dam release temperatures with an estimated, morenatural seasonal temperature regime. Compared to the measured temperatures, the more-natural seasonal temperature 

regime did not have significantly different yearly maximum or 

minimum temperatures. However, the timing of the maximum 

temperature shifted to earlier in the year from late SeptemberOctober to July-August (fig. 19). Thus, the more-natural seasonal temperature input was warmer in late spring and summer 

and cooler in the fall and early winter, compared to the base 

case. The results from this scenario compared to the base case 

are shown in figure 20B. Some warming occurred in July and 

August, between 0° and 2°C, but the most significant feature of 

this scenario was the large cooling effect near the dams in September through November of between -1°C and -7°C. The magnitude of this cooling effect decreased with distance from the 

dam. The month of October had the greatest cooling, -3.74°C, 

while the temperatures in the month of July warmed by an average of +0.12°C. The overall temperature change with this scenario was -1.91°C. A comparison of the results in figure 20B to 

Figure 18. Proposed NOAA Fisheries minimum flow targets for releases from the Detroit and Big Cliff dam complex, U.S. Army Corps of 

Engineers simulated flow from Detroit Dam using those targets, and measured flow at Niagara for 2001. 
28 Modeling Streamflow and Water Temperature in the North Santiam and Santiam Rivers, Oregon 

Figure 19. Estimated more-natural seasonal water temperature and measured temperature (as released from the dam) in the North Santiam 

River at Niagara. 

Table 7. Summary of results from system potential simulations for 2001. 

[Values are averages of simulated 7dADM water temperatures compared to the base case for all segments on all days in each month. 7dADM, 

7-day average of daily maximum; °C, degrees Celsius] 

Average change in 7dADM water temperature, °C 

Scenario Changes to base case July August September October November 

Overall 

(July–November) 

1 System potential vegetation, new minimum 

inflows 

-0.42 -0.47 -0.25 +0.18 +0.04 -0.20 

2 System potential vegetation, new minimum 

inflows, natural seasonal 

inflow temperatures 

+0.12 -0.80 -3.17 -3.74 -2.02 -1.91 

those in figure 13 indicate that the temperature standard still 

would have been exceeded in this scenario, though the extent of 

that exceedance would be decreased substantially in both magnitude, spatial extent, and timing. If anthropogenic disturbances 

upstream of Detroit Lake were minimized, the resulting temperatures might even be cooler. 

Other studies have found similar effects downstream from 

Willamette Basin dams. Hansen (1988) found similar results on 

the McKenzie River downstream of Cougar and Blue River 

dams. The dam produced little effect on river temperatures from 

January through May, cooled the river in June through September and warmed the river from September through the end of 

November; Cougar and Blue River dams are similar to Detroit 

dam in that the discharge point is deep enough to access cold 

stored water in midsummer. Hansen and Crumrine (1991) used 

a one-dimensional model to examine the effect of flow and temperature without the dam on the temperatures downstream of 

Detroit and Big Cliff dams. They also found that the temperature changes attenuated with distance downstream from Detroit. 
Figure 20. Temperature change for (A) system-potential 

scenario 1 and (B) system-potential scenario 2 for 2001, using 

the 7-day moving average of daily maximum water temperature. 

The gray color zone includes all temperature differences within 

0.05°C of 0°C. 

Summary 

A CE-QUAL-W2 model of the North Santiam and Santiam Rivers was constructed and calibrated for July 1 to November 26, 2001, and confirmed for April 1 through October 31, 

2002. The model effectively simulated flow and water temperature on both hourly and seasonal timescales. The mean absolute error (MAE) and root mean square error (RMSE) statistics 

Summary 29 

for water temperature were below 1°C for all stations except 

those on the lower parts of the Santiam River. There, the simulated daily temperature variation was larger than the measured 

variation, and provided indirect evidence of hyporheic flow, 

corroborating the conclusions of previous hydrological studies. 

To complete the water balance, extra flows were added to 

account for ungaged tributaries and ground-water inflows. The 

extra flows were most important during the rainy season and 

storm events. Although the river becomes braided in the vicinity 

of Stayton, the model simulated the rivers as a one-channel system. The temperature simulation did well despite the difference, 

but there was some deviation in measured versus simulated 

travel times in that reach. This could be explained by river 

braiding or the presence of small check dams in the vicinity of 

Stayton. 

The Detroit-Big Cliff dam complex released cold water 

from Detroit Lake in the summer, and river temperatures were 

coldest near the dams at that time of year and could increase by 

as much as 10°C before discharging into the Willamette River. 

In fall, the dams discharged water with stored summer heat; 

river temperatures near the dams at that time were often the 

warmest of the whole system, and cooling occurred as the water 

traveled downstream. 

Observed water temperatures were produced by a combination of releases from Detroit and Big Cliff dams, meteorological factors (including air temperature and solar radiation), temperatures of tributary rivers and streams, and riparian shade. 

Anthropogenic point-source inflows were unimportant in 

determining water temperature in these rivers because such 

sources were relatively small. During summer, the temperatures 

released from the dam did not propagate far downstream before 

being affected by meteorological factors. Daily water temperature variations of up to 7°C at some sites also attest to the importance of radiative heat exchange with the atmosphere. Changes 

in travel time at different flow conditions affected water temperatures by affecting the amount of time available for the river to 

exchange heat with its surroundings. 

During summer and early fall, the downstream parts of the 

North Santiam and the Santiam Rivers were often above Oregon’s water temperature standards. Exceedance of water temperature standards in this system was due to both anthropogenic 

and natural causes. The presence of the dams affected both flow 

and temperature and contributed to exceedances of the temperature standard in the fall, especially in the upper reaches of the 

river. Simulation of a more-natural seasonal temperature 

regime from the dams resulted in significant cooling in the fall 

and some warming in the summer compared to current conditions. This cooling effect was greatest in the upper portion of the 

North Santiam River, and decreased downstream; this was not 

enough to put the lower North Santiam River and Santiam River 

in compliance with temperature standards for the years simulated in this study. Disturbances to the river’s riparian vegetation also contributes somewhat to higher temperatures. Restoring riparian vegetation along the river would provide some 

cooling to the river, but that effect would be smaller than changing the temperature regime from the dams. In the lower reaches 
30 Modeling Streamflow and Water Temperature in the North Santiam and Santiam Rivers, Oregon 

of these rivers, meteorological factors account for most of the 

temperature standard exceedances in midsummer. If the water 

temperature standard cannot be met when anthropogenic heat 

sources are removed—by restoring riparian vegetation and 

removing the heating effects of point sources—then the “system potential” becomes the temperature standard. That is to say, 

the temperature standard stipulates a condition of no measurable anthropogenic heating. The system potential model runs 

shown in this report provide some insight into the types of temeratures that might be achieved in the absence of human disturbances other than the presence of the dams. 

Besides providing an understanding of the river temperature regime and the factors that influence it, this model can be 

used to asses the effects of future changes on the rivers, including restoration of riparian vegetation, different dam operations 

or changes in climate. A CE-QUAL-W2 model of Detroit Lake 

that includes a selective withdrawal tower for the regulation of 

released water temperature is currently being constructed by the 

USGS and will connect to the North Santiam/Santiam River 

model. A selective withdrawal tower would allow releases from 

both reservoir bottom and surface water. This would allow dam 

operators some flexibility to release warmer water in summer 

and cooler water in fall in order to approach a more natural seasonal temperature regime in the North Santiam River. Together, 

the river and reservoir models will allow detailed investigations 

into how dam operations will affect downstream river temperatures. 

Acknowledgments 

This report was prepared with cooperative funding provided by the Oregon Association of Clean Water Agencies. Jim 

Bloom (ODEQ) provided results from the South Santiam CEQUAL-W2 model. Arthur Armour and USACE modelers provided modeled flows from Detroit and Big Cliff dams to meet 

proposed NOAA Fisheries minimum streamflow targets. Agnes 

Lut (ODEQ) and Steve Mrazik (ODEQ) provided detailed 

information on riparian vegetation and other river characteristics. Discussions with members of the Willamette TMDL 

Model Coordination Team, including Scott Wells (PSU), 

Robert Annear (PSU), Chris Berger (PSU), Dave Kliewer (City 

of Portland), Steve Mrazik (ODEQ), Jim Bloom (ODEQ), Brian 

Bicknell (AquaTerra), Arthur Armour (USACE), and Jim Britton (USACE) provided insight in model development and calibration. Helpful information on withdrawals was provided by 

Mary Grainey (OWRD), Libby Barg (City of Salem) and Larry 

Trosi (Santiam Water Control District). Reviews by Dale Robertson (USGS), Alan Flint (USGS), Jim Bloom (ODEQ), Dave 

Kliewer (City of Portland), Scott Wells, (PSU), Robert Annear 

(PSU) and Chris Berger (PSU) improved the manuscript. 

References Cited 

Cole, T.M. and Wells, S.A., 2002, CE-QUAL-W2: A twodimensional, laterally averaged, hydrodynamic and water 

quality model, version 3.1: U.S. Army Corps of Engineers, 

Instruction Report EL–02–1 [variously paged]. 

Dunne, T. and Leopold, L.B., 1978, Water in Environmental 

Planning: San Francisco, W.H. Freeman and Company, 

818 p. 

E & S Environmental Chemistry, Inc. and North Santiam 

Watershed Council, 2002, North Santiam River watershed 

assessment: June, 2002, accessed December 3, 2003, at 

http://www.esenvironmental.com/north_santiam_ 

download.htm 

Hansen, R.P., 1988, The effects of two multipurpose reservoirs 

on the water temperature of the McKenzie River, Oregon: 

U.S. Geological Survey Water-Resources Investigations 

Report 87–4175, 34 p. 

Hansen, R.P. and Crumrine, M.D., 1991, The effects of multipurpose reservoirs on the water temperature of the North and 

South Santiam Rivers, Oregon: U.S. Geological Survey 

Water-Resources Investigations Report 91–4007, 51 p. 

Harris, D.D., 1968, Travel rates of water for selected streams in 

the Willamette River Basin, Oregon: U.S. Geological Survey 

Hydrologic Investigations Atlas HA–273. 

Hinkle, S.R., Duff, J.H., Triska, F.J., Laenen, A., Gates, E.B., 

Bencala, K.E., Wentz, D.A., and Silva, S.R., 2001, Linking 

hyporheic flow and nitrogen cycling near the Willamette 

River—A large river in Oregon, USA: Journal of Hydrology, 

v. 244, no. 3–4, 157–180. 

Laenen, A. and Bencala, K.E., 2001, Transient storage assessments of dye-tracer injections in rivers of the Willamette 

Basin, Oregon: Journal of the American Water Resources 

Association, v. 37, no. 2, 367–377. 

Laenen, A. and Hansen, R.P., 1985, Preliminary study of the 

water-temperature regime of the North Santiam River downstream from Detroit and Big Cliff dams, Oregon: U.S. Geological Survey Water-Resources Investigations Report 84– 

4105, 45 p. 

Laenen, A. and Risley, J.C., 1997, Precipitation-runoff and 

streamflow-routing models for the Willamette River Basin, 

Oregon: U.S. Geological Survey Water Resources Investigations Report 95–4284, 197 p. 

O’Connor, J.E., Sarna-Wojcicki, A., Wozniak, K.C., Polette, 

D.J. and Fleck, R.J., 2001, Origin, extent, and thickness of 

quaternary geologic units in the Willamette Valley, Oregon: 

U.S. Geological Survey Professional Paper 1620, 52 p. 
References Cited 31 

Oregon Department of Environmental Quality, 2001, Oregon Department of Environmental Quality, 2003, Oregon’s 

Oregon Administrative Rules—“The Three Basin Rule”: Final 2002 303(d) List of Water Quality Limited WaterbodOAR 340–41–470, accessed December 3, 2003, at ies: updated September 12, 2003, accessed December 3, 

http://arcweb.sos.state.or.us/rules/OARs_300/OAR_340/ 2003, at http://www.deq.state.or.us/wq/303dlist/ 

340_041.html 303dpage.htm 

Appendix 1


Appendix 1. Revised Water Temperature Standards 35 

Appendix 1. Revised Water Temperature 

Standards 

In this report, it was noted that the water temperature standards were expected to change. The standards were indeed 

revised, and this appendix provides an update with the new temperature criteria. The revisions in the standards were initiated by 

a court case brought by Northwest Environmental Advocates, 

which resulted in the Federal District Court of Oregon overturning the 1999 U.S. Environmental Protection Agency (USEPA) 

approval of Oregon's existing temperature criteria in March 

2003. In order to protect salmonid populations, the USEPA provided guidance to Oregon in formulating new water temperature criteria. The Oregon Department of Environmental Quality 

(ODEQ) used the USEPA guidance along with advice from 

stakeholders, the Oregon Department of Fish and Wildlife, 

NOAA Fisheries and the U.S. Fish and Wildlife Service to formulate proposed standards. Input from the public was received 

through an open comment period and via public hearings across 

the State. The Oregon Environmental Quality Commission 

adopted the new water temperature criteria in December 2003, 

and the USEPA approved them on March 2, 2004. 

Under these new criteria, based on the 7-day moving average of the daily maximum water temperature (7dADM), the 

North Santiam River has been designated as core cold-water 

habitat, with water temperature not to exceed 16.0°C during the 

period June 16–August 31. From September 1 through June 15, 

the river was designated for salmon and steelhead spawning 

use, with a stricter 13.0°C standard in effect. The Santiam River 

was designated as salmon and trout rearing and migration habitat with a maximum 7dADM water temperature of 18.0°C for 

the period May 16–October 14. From October 15 through May 

15, the Santiam River was designated as salmon and steelhead 

spawning use with a maximum 7dADM water temperature of 

13°C. 

Figure 13 of this report, showing the difference between 

the simulated 7dADM and the applicable water standard, has 

been updated with these new temperature standards, and is 

shown here as figure A-1. 

Figure A-1. Difference between the simulated 7-day moving average 

of daily maximum water temperature and the revised water temperature 

standard, in degrees Celsius. 
Back cover: 

The North Santiam River at river mile 29.5, taken on June 4, 2002 (photograph by Ian Wigger, U.S. Geological Survey).