Prepared in cooperation with the U.S. Army Corps of Engineers

Simulating Potential Structural and Operational 

Changes for Detroit Dam on the North Santiam River, 

Oregon, for Downstream Temperature Management

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2012–5231
Cover: Photograph showing Detroit Dam forebay from the shore of Detroit Lake, OR. 

Photograph taken by Scott Evans, U.S. Geological Survey, July 4, 2011.
Simulating Potential Structural and Operational 

Changes for Detroit Dam on the North Santiam 

River, Oregon, for Downstream Temperature 

Management

By Norman L. Buccola, Stewart A. Rounds, Annett B. Sullivan, and John C. Risley

Prepared in cooperation with the U.S. Army Corps of Engineers

Scientific Investigations Report 2012–5231

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2012

For more information on the USGS—the Federal source for science about the Earth, its natural and living 

resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1–888–ASK–USGS.

For an overview of USGS information products, including maps, imagery, and publications, 

visit http://www.usgs.gov/pubprod

To order this and other USGS information products, visit http://store.usgs.gov

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

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.

Suggested citation:

Buccola, N.L, Rounds, S.A., Sullivan, A.B., and Risley, J.C., 2012, Simulating potential structural and operational 

changes for Detroit Dam on the North Santiam River, Oregon, for downstream temperature management: U.S. 

Geological Survey Scientific Investigations Report 2012–5231, 68 p.
iii

Contents

Executive Summary.......................................................................................................................................1

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

Purpose and Scope ..............................................................................................................................6

Methods...........................................................................................................................................................6

Flow and Temperature Models...........................................................................................................6

Detroit Lake and the Custom Blending Routine......................................................................6

Big Cliff Reservoir........................................................................................................................7

North Santiam/Santiam River....................................................................................................7

Environmental Scenarios ....................................................................................................................7

Without-Dam Water Temperature Estimation................................................................................11

Temperature Targets ..........................................................................................................................12

Model Setup and Usage ....................................................................................................................14

Dam Outflow Estimation ...........................................................................................................14

Detroit Dam........................................................................................................................14

Big Cliff Dam ......................................................................................................................15

Meteorological Inputs...............................................................................................................15

Detroit Dam Scenarios and Naming Convention..................................................................16

Detroit Dam Operational Scenarios..........................................................................................................18

Detroit Dam Reference Conditions ..................................................................................................18

base Operational Scenario ......................................................................................................18

Without-Dams Temperature Target ........................................................................................18

Fixed Lake Level at Minimum Conservation Pool (1,450 feet) .....................................................22

Delayed Drawdown............................................................................................................................23

Reduced Minimum Outflows....................................................................................................23

Reduced Minimum Outflows and Modified Rule Curve ......................................................24

Detroit Dam Structural Scenarios.............................................................................................................28

Single Sliding-Gate Structure...........................................................................................................28

Floating and Fixed-Elevation Gates .................................................................................................29

Floating Outlet with Power Penstocks ...................................................................................29

No Minimum Flow through Power Penstocks or Floating Outlet..............................29

Twenty Percent Minimum Flow through Power Penstocks.......................................30

Minimum Flow of 400 Cubic Feet per Second through Floating Outlet ...................30

Floating Outlet with Upper Regulating Outlets......................................................................31

Minimum Flow of 400 Cubic Feet per Second through Floating Outlet ...................32

Twenty Percent Minimum Flow through Upper ROs...................................................32

Forty Percent Minimum Flow through Upper ROs.......................................................33

Sliding and Floating Gates.................................................................................................................33

Fixed Flow of 400 Cubic Feet per Second through Floating Outlet ....................................34
iv

Downstream Effects of Selected Scenarios ..........................................................................................35

Estimated Emergence Dates.............................................................................................................35

North Santiam River Temperatures .................................................................................................38

Base Case ...................................................................................................................................38

Delayed Drawdown...................................................................................................................38

Floating and Fixed-Elevation Gates .......................................................................................38

A Single Sliding-Gate Structure ..............................................................................................38

Floating and Sliding-Gate Structures .....................................................................................38

Implications for Dam Operation and Planning........................................................................................44

Acknowledgments.......................................................................................................................................45

References Cited..........................................................................................................................................45

Appendix A. Big Cliff Reservoir Model Development—Construction and Calibration.................47

Appendix B. Detroit Lake and Big Cliff Reservoir Model Evaluation for 2011 ................................54

Appendix C. Code Modifications ...........................................................................................................59

Appendix D. North Santiam and Santiam River Model Set-Up and Application ...........................61

Appendix E. Additional Model Scenarios.............................................................................................63

Contents—Continued

Figures

Figure 1. Map showing location of Detroit Lake, Detroit Dam, and Big Cliff Dam in the

North Santiam River basin in western Oregon .......................................... 4

Figure 2. Map showing North Santiam and Santiam Rivers and the North Santiam River

basin in western Oregon .................................................................. 5

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

withdrawals, and USGS streamflow-gaging stations in the North Santiam and

Santiam Rivers downstream of Big Cliff Dam, Oregon ................................. 8

Figure 4. Graph showing monthly mean discharge in the North Santiam River below

Boulder Creek (USGS station 14178000) under three scenarios, North Santiam

River, Oregon................................................................................. 10

Figure 5. Graph showing monthly mean stream temperature in the North Santiam River

below Boulder Creek (USGS site 14178000) under three scenarios, North

Santiam River, Oregon ..................................................................... 11

Figure 6. Graphs showing estimated without-dam water temperatures (labeled “wod”)

at the Detroit Dam site compared to measured (USGS station 14181500) hourly

water temperatures for the three environmental scenarios, North Santiam

River, Oregon................................................................................. 13

Figure 7. Graphs showing comparison of existing structural scenarios with base

operational scenarios (scenarios c1, n1, h1) total inflows, total outflows, and

modeled water-surface elevation and rule curve, North Santiam River, Oregon ... 19

Figure 8. Graphs showing modeled water temperature and percent spill for existing

structural scenarios with base operational scenarios, and max temperature

targets (scenarios c1, n1, h1), North Santiam River, Oregon ........................... 20
v

Figures—Continued

Figure 9. Graphs showing modeled water temperature, and percent spill for existing

structural scenarios with noppmin operational scenarios, and max

temperature targets (scenarios c2, n2, h2), North Santiam River, Oregon............ 20

Figure 10. Graphs showing modeled water temperature and percent spill for existing

structural scenarios with base operational scenarios and wo_dams7dADMax

temperature targets (scenarios cwod1, nwod1, hwod1), North Santiam River,

Oregon ....................................................................................... 21

Figure 11. Graphs showing modeled water temperature and percent spill for existing

structural scenarios with noppmin operational scenarios and

wo_dams7dADMax temperature targets (scenarios cwod2, nwod2, hwod2),

North Santiam River, Oregon............................................................... 21

Figure 12. Graphs showing comparison of fixed_elevation operational scenarios

(scenarios c3, n3, h3), total inflows, total outflows, modeled water-surface

elevation, North Santiam River, Oregon ................................................ 22

Figure 13. Graphs showing modeled water temperature and percent spill for existing

structural scenarios with fixed elevation operational scenarios and max

temperature targets (scenarios c3, n3, h3), North Santiam River, Oregon............ 23

Figure 14. Graphs showing comparison of delay_dd1 operational scenarios (scenarios

c6, n6, h6), total inflows, total outflows, modeled water-surface elevation,

North Santiam River, Oregon............................................................... 24

Figure 15. Graphs showing modeled water temperature and percent spill for existing

structural scenarios with delay_dd1 operational scenarios and max

temperature targets (scenarios c6, n6, h6), North Santiam River, Oregon............ 25

Figure 16. Graphs showing modeled water temperature and percent spill for existing

structural scenarios with delay_dd1_noppmin operations and max

temperature targets (scenarios c7, n7, h7), North Santiam River, Oregon............ 25

Figure 17. Graphs showing comparison of delay_dd2 operational scenarios (scenarios 8,

9, and 18), total inflows; total outflows, modeled water-surface elevation,

North Santiam River, Oregon ............................................................ 26

Figure 18. Graphs showing modeled water temperature and percent spill for existing

structural scenarios with delay_dd2 operations and max temperature targets

(scenarios c8, n8, h8), North Santiam River, Oregon .................................... 27

Figure 19. Graphs showing modeled water temperature and percent spill for existing

structural scenarios with delay_dd2_noppmin operations and max

temperature targets (scenarios c9, n9, h9), North Santiam River, Oregon............ 27

Figure 20. Graphs showing modeled water temperature and sliding-gate elevation for

slider1340 structural scenarios with base operations and max temperature

targets (scenarios c17, n17, h17), North Santiam River, Oregon ..................... 28

Figure 21. Graphs showing results from pp-float structural scenarios with nomins

operations and max temperature targets (scenarios c10, n10, h10), modeled

water temperature, outflow from fixed outlet, and outflow from floating outlet,

North Santiam River, Oregon............................................................... 29

Figure 22. Graphs showing results from pp-float structural scenarios with 20ppmin

operations and max temperature targets (scenarios c12, n12, h12), modeled

water temperature, outflow from fixed outlet, and outflow from floating outlet,

North Santiam River, Oregon............................................................... 30
vi

Figures—Continued

Figure 23. Graphs showing results from pp-float structural scenarios with 400fmin

operations and max temperature targets (scenarios c13, n13, h13), modeled

water temperature, outflow from fixed outlet, and outflow from floating outlet,

North Santiam River, Oregon............................................................... 31

Figure 24. Graphs showing results from uro-float structural scenarios with 400fmin

operations and max temperature targets (scenarios c14, n14, h14), modeled

water temperature, outflow from fixed outlet, and outflow from floating outlet,

North Santiam River, Oregon............................................................... 32

Figure 25. Graphs showing results from uro-float structural scenarios with 20ppmin

operations and max temperature targets (scenarios c15, n15, h15), modeled

water temperature, outflow from fixed outlet, and outflow from floating outlet,

North Santiam River, Oregon............................................................... 33

Figure 26. Graphs showing results from uro-float structural scenarios with 40ppmin

operations and max temperature targets (scenarios c16, n16, h16), modeled

water temperature, outflow from fixed outlet, and outflow from floating outlet,

North Santiam River, Oregon............................................................... 34

Figure 27. Graphs showing results from slider1340-float structural scenarios with 400f

operations and max temperature targets (scenarios c19, n19, h19), modeled

water temperature, outflow from fixed outlet, and sliding outlet elevation,

North Santiam River, Oregon............................................................... 35

Figure 28. Graphs showing computed progression of Accumulated Thermal Units for

selected model scenarios, showing the different likely rates of egg incubation

over the autumn months, North Santiam River, Oregon................................. 37

Figure 29. Graphs showing simulated 7-day moving average of the daily maximum water

temperature from the North Santiam and Santiam River model under hot/dry

environmental conditions and base operations.......................................... 39

Figure 30. Graphs showing difference between the 7-day moving average of the daily

maximum water temperature from the North Santiam and Santiam River model

scenarios h8 (existing structures, delay_dd2 operations, and hot/dry

conditions) and h1 (existing structures and base operations) ........................ 40

Figure 31. Graphs showing difference between the 7-day moving average of the daily

maximum water temperature from the North Santiam and Santiam River model

scenarios h10 (pp-float structures, nomins operations, and hot/dry conditions)

and h1 (existing structures and base operations) ....................................... 41

Figure 32. Graphs showing difference between the 7-day moving average of the daily

maximum water temperature from the North Santiam and Santiam River model

scenarios h17 (slider1340 structures, base operations, and hot/dry conditions)

and h1 (existing structures and base operations) ....................................... 42

Figure 33. Graphs showing difference between the 7-day moving average of the daily

maximum water temperature from the North Santiam and Santiam River model

scenarios h19 (slider1340-float structures, 400f operations, and hot/dry

conditions) and h1 (existing structures and base operations) ........................ 43
vii

Tables

Table 1. Ranking of streamflow and water-temperature conditions at USGS gaging

station 14178000 (North Santiam River below Boulder Creek, Oregon) for two

periods in each calendar year, 2000–2009. ............................................. 9

Table 2. Description of environmental scenarios, North Santiam River, Oregon. ............ 9

Table 3. Mean, minimum, and maximum annual without-dam temperature estimates

(labeled “W/o-dams”) at Detroit Dam (river mile 60.9) along with measured

mean, minimum, and maximum annual with-dam temperatures (labeled

“With-dams”) at USGS gaging station 14181500 (river mile 57.3) for three

environmental scenarios, North Santiam River, Oregon. .............................. 13

Table 4. Minimum and maximum Detroit Dam outflow requirements for operational

scenarios, North Santiam River, Oregon. ................................................ 15

Table 5. Operational scenario group descriptions, Detroit Dam, North Santiam River,

Oregon. ....................................................................................... 16

Table 6. Structural scenarios group descriptions, Detroit Dam, North Santiam River,

Oregon. ....................................................................................... 17

Table 7. Specification and naming convention of model scenarios, Detroit Dam, North

Santiam River, Oregon. ..................................................................... 17

Table 8. Calculated emergence day for each Detroit Lake model scenario based on the

day at which the Accumulated Thermal Units (ATUs) for simulated release

temperatures reached 1,750 degrees Fahrenheit-day, North Santiam River,

Oregon. ....................................................................................... 36

Table 9. Calculated emergence day at Mehema (river mile 38.7) from the North Santiam

River model were based on the day at which the Accumulated Thermal Units

(ATUs) reached 1,750 degrees Fahrenheit-day, North Santiam River, Oregon. ...... 38
viii

Abbreviations and Acronyms

Abbreviation or 

acronym Description

7dADM 7-day moving average of the daily maximum

ATU Accumulated Thermal Unit

BiOP Biological Opinion

CE-QUAL-W2 2-dimensional hydrodynamic and water-quality model

DMR Discharge Monitoring Report

MAE mean absolute error

ME mean error

NCDC National Climatic Data Center (National Oceanic and Atmospheric Administration)

NS Nash-Sutcliffe coefficient

ODEQ Oregon Department of Environmental Quality

RAWS Remote Automated Weather Station

RM river mile

RMSE root mean square error

SRML Solar Radiation Monitoring Laboratory (University of Oregon)

USGS U.S. Geological Survey

Datums

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

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

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

Conversion Factors, Datums, and 

Abbreviations and Acronyms

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

square mile (mi2) 2.590 square kilometer (km2) 

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

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

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

square foot per second (ft2/s) 0.0929 square meter per second (m2/s)

SI to Inch/Pound

Multiply By To obtain

meter (m) 3.281 foot (ft) 

cubic meter per second (m3/s) 70.07 acre-foot per day (acre-ft/d) 

square meter per second (m2/s) 10.7639 square foot per second (ft2/s)

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

°F=(1.8×°C)+32.

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

°C=(°F-32)/1.8.
Executive Summary

Detroit Dam was constructed in 1953 on the North 

Santiam River in western Oregon and resulted in the 

formation of Detroit Lake. With a full-pool storage volume 

of 455,100 acre-feet and a dam height of 463 feet, Detroit 

Lake is one of the largest and most important reservoirs in 

the Willamette River basin in terms of power generation, 

recreation, and water storage and releases. The U.S. Army 

Corps of Engineers operates Detroit Dam as part of a system 

of 13 reservoirs in the Willamette Project to meet multiple 

goals, which include flood-damage protection, power 

generation, downstream navigation, recreation, and irrigation.

A distinct cycle in water temperature occurs in Detroit 

Lake as spring and summer heating through solar radiation 

creates a warm layer of water near the surface and isolates 

cold water below. Controlling the temperature of releases from 

Detroit Dam, therefore, is highly dependent on the location, 

characteristics, and usage of the dam’s outlet structures. Prior 

to operational changes in 2007, Detroit Dam had a welldocumented effect on downstream water temperature that was 

problematic for endangered salmonid fish species, releasing 

water that was too cold in midsummer and too warm in 

autumn. This unnatural seasonal temperature pattern caused 

problems in the timing of fish migration, spawning, and 

emergence. 

In this study, an existing calibrated 2-dimensional 

hydrodynamic water-quality model [CE-QUAL-W2] of 

Detroit Lake was used to determine how changes in dam 

operation or changes to the structural release points of Detroit 

Dam might affect downstream water temperatures under a 

range of historical hydrologic and meteorological conditions. 

The results from a subset of the Detroit Lake model scenarios 

then were used as forcing conditions for downstream 

CE-QUAL-W2 models of Big Cliff Reservoir (the small 

reregulating reservoir just downstream of Detroit Dam) and 

the North Santiam and Santiam Rivers.

Many combinations of environmental, operational, and 

structural options were explored with the model scenarios. 

Multiple downstream temperature targets were used 

along with three sets of environmental forcing conditions 

representing cool/wet, normal, and hot/dry conditions. Five 

structural options at Detroit Dam were modeled, including 

the use of existing outlets, one hypothetical variable-elevation 

outlet such as a sliding gate, a hypothetical combination of a 

floating outlet and a fixed-elevation outlet, and a hypothetical 

combination of a floating outlet and a sliding gate. Finally, 14 

sets of operational guidelines for Detroit Dam were explored 

to gain an understanding of the effects of imposing different 

downstream minimum streamflows, imposing minimum 

outflow rules to specific outlets, and managing the level of 

the lake with different timelines through the year. Selected 

subsets of these combinations of operational and structural 

scenarios were run through the downstream models of Big 

Cliff Reservoir and the North Santiam and Santiam Rivers 

to explore how hypothetical changes at Detroit Dam might 

provide improved temperatures for endangered salmonids 

downstream of the Detroit-Big Cliff Dam complex.

Conclusions that can be drawn from these model 

scenarios include:

• The water-temperature targets set by the U.S. Army 

Corps of Engineers for releases from Detroit Dam can 

be met through a combination of new dam outlets or a 

delayed drawdown of the lake in autumn.

• Spring and summer dam operations greatly affect 

the available release temperatures and operational 

flexibility later in the autumn. Releasing warm water 

during midsummer tends to keep more cool water 

available for release in autumn.

• The ability to meet downstream temperature targets 

during spring depends on the characteristics of the 

available outlets. Under existing conditions, although 

warm water sometimes is present at the lake surface 

in spring and early summer, such water may not be 

available for release if the lake level is either well 

below or well above the spillway crest.

Simulating Potential Structural and Operational 

Changes for Detroit Dam on the North Santiam River, 

Oregon, for Downstream Temperature Management 

By Norman L. Buccola, Stewart A. Rounds, Annett B. Sullivan, and John C. Risley
2 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

• Managing lake releases to meet downstream 

temperature targets depends on having outlet structures 

that can access both (warm) lake surface water and 

(cold) deeper lake water throughout the year. The 

existing outlets at Detroit Dam do not allow nearsurface waters to be released during times when the 

lake surface level is below the spillway (spring and 

autumn).

• Using the existing outlets at Detroit Dam, lake level 

management is important to the water temperature of 

releases because it controls the availability and depth 

of water at the spillway. When lake level is lowered 

below the spillway crest in late summer, the loss of 

access to warm water at the lake surface can result in 

abrupt changes to release temperatures.

• Because the power-generation intakes (penstocks) 

are 166 feet below the full-pool lake level, imposing 

minimum power production requirements at Detroit 

Dam limits the amount of warm surface water that 

can be expelled from the lake in midsummer, thereby 

postponing and amplifying warm outflows from 

Detroit Lake into the autumn spawning season. 

• Likewise, imposing minimum power production 

requirements at Detroit Dam in autumn can limit the 

amount of cool hypolimnetic water that is released 

from the lake, thereby limiting cool outflows from 

Detroit Lake during the autumn spawning season. 

• Model simulations indicate that a delayed drawdown 

of Detroit Lake in autumn would result in better 

control over release temperatures in the immediate 

downstream vicinity of Big Cliff Dam, but the reduced 

outflows necessary to retain more water in the lake 

in late summer are more susceptible to rapid heating 

downstream.

• Compared to the existing outlets at Detroit Dam, 

floating or sliding-gate outlet structures can provide 

greater control over release temperatures because they 

provide better access to warm water at the lake surface 

and cooler water at depth.

These conclusions can be grouped into several 

common themes. First, optimal and flexible management 

and achievement of downstream temperature goals requires 

that releases of warm water near the surface of the lake and 

cold water below the thermocline are both possible with the 

available dam outlets during spring, summer, and autumn. 

This constraint can be met to some extent with existing 

outlets, but only if access to the spillway is extended into 

autumn by keeping the lake level higher than called for by the 

current rule curve (the typical target water-surface elevation 

throughout the year). If new outlets are considered, a variableelevation outlet such as a sliding gate structure, or a floating 

outlet in combination with a fixed-elevation outlet at sufficient 

depth to access cold water, is likely to work well in terms 

of accessing a range of water temperatures and achieving 

downstream temperature targets.

Furthermore, model results indicate that it is important 

to release warm water from near the lake surface during 

midsummer. If not released downstream, the warm water will 

build up at the top of the lake as a result of solar energy inputs 

and the thermocline will deepen, potentially causing warm 

water to reach the depth of deeper fixed-elevation outlets 

in autumn, particularly when the lake level is drawn down 

to make room for flood storage. Delaying the drawdown in 

autumn can help to keep the thermocline above such outlets 

and preserve access to cold water.

Although it is important to generate hydropower at 

Detroit Dam, minimum power-production requirements limit 

the ability of dam operators to meet downstream temperature 

targets with existing outlet structures. The location of the 

power penstocks below the thermocline in spring and most of 

summer causes the release of more cool water during summer 

than is optimal. Reducing the power-production constraint 

allows the temperature target to be met more frequently, but at 

the cost of less power generation.

Finally, running the Detroit Dam, Big Cliff Dam, and 

North Santiam and Santiam River models in series allows dam 

operators to evaluate how different operational strategies or 

combinations of new dam outlets might affect downstream 

temperatures for many miles of critical endangered salmonid 

habitat. Temperatures can change quickly in these downstream 

reaches as the river exchanges heat with its surroundings, and 

heating or cooling of 6 degrees Celsius is not unusual in the 

40–50 miles downstream of Big Cliff Dam.

The results published in this report supersede preliminary 

results published in U.S. Geological Survey Open-File Report 

2011-1268 (Buccola and Rounds, 2011). Those preliminary 

results are still valid, but the results in this report are more 

current and comprehensive.
Introduction 3

Introduction

Detroit Dam was constructed in 1953 by the U.S. Army 

Corps of Engineers (USACE) on the North Santiam River 

in western Oregon and resulted in the formation of Detroit 

Lake (fig. 1). The North Santiam River drains an area on the 

western slopes of the Cascade Range, and it is one of several 

major tributaries to the Willamette River (fig. 2). Detroit 

Dam is the tallest dam (463 ft) in the Willamette River basin 

and impounds 455,100 acre-ft of water at full pool, making 

Detroit Lake one of the largest reservoirs in the basin. The 

smaller reregulating dam downstream of Detroit Dam, Big 

Cliff Dam, ensures steady streamflows in the North Santiam 

River and allows Detroit Dam’s power generating facility (and 

releases) to be turned on and off during the course of a day 

to meet peak electrical demands. The Big Cliff–Detroit Dam 

complex typically generates more hydroelectric power than 

any other USACE facility in the Willamette River basin, and 

Detroit Lake ranks as one of the most important recreational 

resources among the 13 reservoirs managed by USACE in the 

Willamette Project. 

Prior to 2007, power generation was a high priority for 

the Big Cliff–Detroit Dam complex, and releases from Detroit 

Dam generally were routed through the power penstocks 

(centerline elevation 427.6 m [1,402.9 ft]) except for times 

when excess flows were released through the upper regulating 

outlets (ROs, center-line elevation 408.4 m [1,339.9 ft]) 

or over the spillway (crest elevation 469.7 m [1,541.0 ft]). 

During those years, midsummer releases were unseasonably 

cold because the power penstocks are located 166 ft below 

Detroit Lake’s full-pool level, well below the thermocline at 

that time of year. Releases from that depth allowed summer 

solar energy inputs to accumulate in a growing layer of warm 

water at the lake surface. Drawdown of the lake in September 

to make room for winter flood storage typically brought that 

warmer water down to the level of the power penstocks, thus 

resulting in unseasonably warm releases in late summer and 

autumn. These somewhat “unnatural” seasonal patterns in the 

temperature releases can be confusing to anadromous fish, 

altering the timing of migration, spawning, and egg emergence 

(Caissie, 2006). The thermal effects of Willamette River basin 

dams have been quantified in recent modeling studies, and the 

effects can extend for many miles and many days of travel 

time downstream (Rounds, 2010).

The North Santiam River and its tributaries (fig. 2) 

provide habitat for endangered Upper Willamette River 

Chinook salmon (Oncorhynchus tshawytscha) and Upper 

Willamette River winter steelhead (O. mykiss). The Oregon 

Department of Environmental Quality (ODEQ) has set 

maximum water-temperature standards for stream reaches in 

Oregon, including the North Santiam and Santiam Rivers, to 

protect certain life stages of these sensitive fish. These criteria 

are based on the 7-day moving average of the daily maximum 

(7dADM) water temperature. For example, the North Santiam 

River was designated as core cold-water habitat for June 16–

August 31 annually, with the 7dADM water temperature not to 

exceed 16.0°C, and as salmon and steelhead spawning habitat 

for September 1–June 15, with a stricter 13.0°C criterion. 

Farther downstream, the Santiam River was designated 

as salmon and trout rearing and migration habitat with a 

maximum 7dADM water temperature of 18.0°C for May 

16–October 14, and salmon and steelhead spawning habitat 

for October 15–May 15 with the 13°C maximum criterion for 

spawning. (Oregon Department of Environmental Quality, 

2009).

To protect and enhance these beneficial uses and 

habitats, the National Marine Fisheries Service wrote a 2008 

Willamette Basin Biological Opinion (BiOP) that, among 

other things, urges the USACE to assess the feasibility of 

developing project-specific alternatives for achieving longterm temperature control at the Big Cliff–Detroit Dam 

complex (National Marine Fisheries Service, 2008). The 

USACE is in the process of evaluating alternatives for both 

current and long-term downstream temperature management 

as well as fish passage at many of the dams in the Willamette 

Project.

Detroit Dam is an excellent facility for the USACE to test 

strategies for downstream temperature management because 

the dam has outlets at several fixed elevations, allowing water 

to be released from multiple depths and blended to meet a 

downstream temperature target. In particular, the release of 

warm water over the spillway in midsummer and cool water 

from deep in the lake in late summer and early autumn can 

help mitigate problems associated with water temperatures 

that otherwise are too cold or too warm for fish. Since 2007, 

USACE has used the spillway and the ROs in addition to 

the power penstocks to improve downstream fish habitat 

during the various life stages of endangered salmonid fish 

species, while at the same time balancing the need to generate 

hydropower. 

To help evaluate potential dam operation strategies and 

future structural options, the USACE can rely on predictions 

from several models of the Detroit Lake and North Santiam 

River system. The U.S. Geological Survey (USGS) has 

constructed a model of Detroit Lake to examine watertemperature and suspended-sediment conditions in the lake 

and downstream (Sullivan and others, 2007). The model 

was built using CE-QUAL-W2, a two-dimensional, laterally 

averaged hydrodynamic and water-quality model from 

USACE (Cole and Wells, 2002) that is widely applied to river 

and reservoir systems around the world. The USGS Detroit 

Lake model was calibrated to conditions during calendar years 

2002 and 2003 and was tested for high-flow conditions in 

2005–06. The model and many results are available online at 

http://or.water.usgs.gov/santiam/detroit_lake/.
4 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

tac12-0772_fig01

14179000

OREGON

Salem

Big Cliff

Dam

Detroit

Dam

Breitenbush

River

Santiam

Blowout

Creek

Kinney Creek

Box

Canyon

Creek

Niagara

French Creek

Mt

Jefferson

River

North

Detroit Lake

Drainage 

area for 

gaging 

station at 

Niagara

EXPLANATION

Drainage area upstream of Detroit Dam

Meteorological station

Temperature profile site

USGS discharge and temperature

monitors

14178000

14180300

0 5 10 15 KILOMETERS

0 5 10 MILES

122°20' 10' 122° 121°50'

44°30'

40'

44°50'

Base map modified from U.S. Geological Survey digital data (1:24,000). 

Projection: UTM, Zone 10, North American Datum of 1927.

Figure 1. Location of Detroit Lake, Detroit Dam, and Big Cliff Dam in the North Santiam River basin in western Oregon. (Map 

modified from Sullivan and others, 2007).
Introduction 

5 tac12-0772_fig02

Breitenbush

Santiam

Santiam

Elkhorn C

N F River North Little

Stout Nor ht

River

Sant ai m

SANTIAM

TTE MALLI W E Nor ht Chehulpum R vi er

RIVER

R VI ER Cr

Cedar

Mad Creek

French Cr

Rock Creek Detroit Lake

Blowout

Creek

Pameli Creek

Cr

Creek

Breitenbush

Boulder Cr

Whit we ater

Turpentine

River

River

C er ek Valent ni e

a M

oir n

Creek

Cr

Cr

Bear Branch

mait

n

a

S

roN

ht

i R ver

5

22

22

amaheM

Mill

City

tiorteD

eillalO

Butte

tM

Jefferson

Three

deregniF

kcaJ

WILLAMETTE

VALLEY

C

A

S

C

A

D

E

R

A

N

G

E

notyatS

Jefferson Big Cliff Dam Detroit Dam

122 ̊ 15' 122 ̊ 22' 30" 122 ̊ 30' 122 ̊ 37' 30" 122 ̊ 45' 122 ̊ 52' 123 ̊ 123 ̊ 07' 122 ̊ 07' 30" 122 ̊ 121 ̊ 52' 30" 121 ̊ 45'

44 ̊

52'30"

44 ̊

45'

44 ̊

37'30"

44 ̊

30'

EXPLANATION

Base map modified from U.S. Geological Survey and other digital data (1:24 000). Projection: UTM, Zone 10, North American Datum 1927. 

OREGON

Study

area

Meteorological stationUSGS gaging stationDam

0 5 10 MILES0 5 10 KILOMETERS

Figure 2. North Santiam and Santiam Rivers and the North Santiam River basin in western Oregon. (Map reproduced from Sullivan and Rounds, 2004).
6 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

The USGS Detroit Lake model was built with 

CE-QUAL-W2 version 3.12, modified to include a custom 

subroutine that allows a model user to easily estimate 

release rates from different dam outlets that are necessary 

to achieve a time series of downstream temperature targets 

(Rounds and Sullivan, 2006; Buccola and Rounds, 2011). 

In this way, dam operations can be forecast to meet certain 

downstream fish habitat criteria at different times of the year. 

CE-QUAL-W2 models of Big Cliff Reservoir and the North 

Santiam and Santiam Rivers (Sullivan and Rounds, 2004) also 

are available. Using those models, predicted flows and water 

temperatures from the Detroit Lake model can be translated 

downstream to evaluate how temperatures change in the 61 mi 

of river downstream of Detroit Dam before the Santiam River 

joins the Willamette River. 

Purpose and Scope

To better inform structural and operational planning 

decisions related to Detroit Dam outflow temperature 

management, the USACE asked the USGS to assist in 

temperature modeling of the Detroit Lake–Big Cliff 

Reservoir–North Santiam River system. The purpose of this 

report is to provide water temperature estimates throughout 

the North Santiam River system from just upstream of Detroit 

Lake to the junction of the North and South Santiam Rivers 

(49.2 mi downstream of Detroit Dam) under a range of 

environmental conditions, alternative dam operations, and 

potential structural changes at Detroit Dam. Model results 

presented in this report are intended to inform the current 

and future operation of Big Cliff and Detroit Dams (and 

other similar dams in the Pacific Northwest) as well as the 

planning process for potential structural alterations to Detroit 

Dam undertaken by USACE for the purpose of improving 

downstream temperature conditions for fish in the North 

Santiam River. 

The following guiding objectives were used to examine 

and quantify the downstream thermal effects of potential 

operational and structural changes to Detroit Dam: 

• Develop a range of environmental conditions that 

represent “cool/wet,” “normal,” and “hot/dry” 

hydrologic and meteorological inputs that can serve as 

boundary conditions for all scenarios. 

• Estimate water temperatures in the North Santiam 

River that might occur in the absence of dams. 

• Simulate a range of potential operational and structural 

scenarios at Detroit Dam and compare predicted 

outflow temperatures against existing conditions. 

• Simulate conditions downstream of Detroit Dam using 

the Big Cliff Reservoir and North Santiam River 

models for a select subset of model scenarios and 

compare to existing conditions.

This study used previously developed CE-QUAL-W2 

models of Detroit Lake (Sullivan and others, 2007), Big Cliff 

Reservoir (model development documented in appendix A), 

and the North Santiam River (Sullivan and Rounds, 2004) 

for all simulations of water discharge and temperature. After 

an assessment of variations in historical data, measured 

meteorological and hydrologic data from 2002, 2005, 2006, 

and 2009 were used in this study for forcing conditions to the 

models and calculations. The calibration performance of the 

Detroit Lake and Big Cliff Reservoir models was checked 

using existing operating conditions in the 2011 calendar year, 

a year in which measured temperature profiles existed in 

both lakes. By using measured data from 2002 to 2011, the 

simulations reflect the most current climatic conditions and 

take advantage of the extensive datasets collected in recent 

years.

Methods

Flow and Temperature Models

Three separate CE-QUAL-W2 models were used in this 

study to simulate Detroit Lake, Big Cliff Reservoir, and the 

North Santiam and Santiam Rivers. All of the model scenarios 

presented in this report were simulated using the Detroit 

Lake model, but only some of these scenarios were run with 

the downstream models of Big Cliff Reservoir and the North 

Santiam and Santiam Rivers. 

Detroit Lake and the Custom Blending Routine

The CE-QUAL-W2 version 3.12 model of Detroit Lake 

was developed originally by Sullivan and others (2007) for 

conditions that occurred primarily in 2002 and 2003 when 

the primary outlet structure was the power penstocks. Since 

2007, typical operations at Detroit Dam include releases 

through the power penstocks as well as seasonal usage of the 

spillway (during summer) and the upper ROs (during autumn) 

for downstream temperature management. To ensure that 

the previously calibrated model accurately represented these 

new dam operations, the Detroit Lake model calibration was 

checked and updated using conditions from calendar year 2011 

before it (the Detroit Lake model) was applied to the other 

scenarios of this project. See appendix B for a description of 

model performance and slight alterations in the calibration 

for 2011. In general, the model was accurate in its depiction 

of 2011 in-lake vertical temperature profiles and release 

temperatures, with mean errors showing a slight negative bias, 

but within 0.5°C, and mean absolute errors less than about 

0.8°C for the profiles and about 0.9°C for the releases, in good 

agreement with previously documented model performance 

for Detroit Lake (Sullivan and others, 2007).
Methods 7

The previously developed Detroit Lake model used in 

this study already included a custom subroutine designed to 

optimize releases from a set of user-specified outlets to meet 

a downstream temperature target (Rounds and Sullivan, 2006; 

Sullivan and Rounds, 2006). The user specifies the total 

release rate time series for a group of potential outlets along 

with a time series of desired temperature releases. The 

subroutine then selects two outlets from among the group of 

usable outlets, and determines the optimal release rates from 

those outlets that are required to match the user-specified 

downstream temperatures. The blending algorithm allows the 

user to specify several types of outlets, including floating, 

sliding-gate (variable-elevation), and fixed-elevation outlet 

structures.

For this study, the custom blending algorithm was 

further modified and improved in several ways. First, the user 

can specify that a minimum fraction of the total releases be 

assigned to a particular outlet. This allows, for example, the 

user to specify that at least 40 percent of the releases from 

Detroit Dam go through the powerhouse. That capability 

was used in several of the scenarios in this study. Second, 

a minimum release rate also can be assigned to a particular 

outlet. In this study, this feature was used to set a minimum 

release rate of 400 ft3/s from a hypothetical floating outlet. 

Third, the user can specify a priority ranking for each of the 

outlets in an outlet group, such that one outlet is preferred 

for releases when (1) the lake is isothermal and the choice 

of outlet has little to no effect on release temperatures, or 

(2) the minimum flow fraction or minimum release rate 

criteria are in conflict. The priority ranking allows the user 

to assign more flow to power generation, for example, when 

the lake is isothermal. Finally, the blending algorithm itself 

was improved, incorporating an iterative solution method that 

greatly improved the algorithm’s ability to match the userspecified temperature target. Because the release temperature 

from each outlet is a function of flow, an iterative process 

is required to find the best combination of flows from two 

different outlets to match the downstream temperature target.

These updates to the blending subroutine require two 

new input parameters in the model control file, one for the 

minimum fraction (0 to 1) or minimum release rate (input 

as a negative number), and a second for the priority ranking. 

The code changes and updates are described in appendix C. 

The code changes were meant to be as general as possible, 

but in this study it was not necessary to specify more than two 

available outlets at any time. The algorithm for choosing two 

outlets from among a group of more than two available outlets 

was not updated to use the priority ranking or the minimum 

fraction or flow release criteria.

Big Cliff Reservoir

The customized version 3.12 CE-QUAL-W2 executable 

used for the Detroit Lake temperature model also was used for 

the Big Cliff Reservoir model. Big Cliff Reservoir is a small 

reregulating reservoir just downstream of Detroit Dam, and 

its operation has a small effect on water temperature at some 

times of the year. The development of the Big Cliff model is 

discussed in more detail in appendix A.

North Santiam/Santiam River

The CE-QUAL-W2 model used to simulate streamflow 

and water temperature in the North Santiam and Santiam 

Rivers from Big Cliff Dam (river mile [RM] 58.1) to the 

Willamette River confluence was constructed and calibrated 

in a previous study to support the Willamette River watertemperature Total Maximum Daily Load (TMDL) process 

(Sullivan and Rounds, 2004). That study relied on version 

3.12 of CE-QUAL-W2 but included some customized outputs 

to help compute water-temperature statistics for the TMDL 

work. The same model version and configuration used in 

the previous study was applied in this study. The model grid 

consisted of 1 water body, 6 branches, and 310 segments 

extending over approximately 58.1 mi of the North Santiam 

and Santiam Rivers (fig. 3). A further description of the 

methods and assumptions involved in setting up and applying 

this model is in appendix D. 

Some of the model scenarios included in this study 

resulted in temperature releases from Detroit Dam that 

were either not very successful in matching the intended 

downstream target or closely matched those of another 

scenario. Appendix E provides documentation for that set of 

model scenarios.

Environmental Scenarios

Three distinctly different environmental forcing 

scenarios—streamflow input, temperature inflow, and 

weather conditions—were developed to evaluate temperature 

management operations and structural options at Detroit 

Dam. To ensure that the streamflow, water temperature, 

and meteorological datasets used to drive the models were 

consistent with one another, the simplest approach was to use 

historical datasets that represented a wide range of possible 

conditions, from cold and wet to normal to warm and dry.
8 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

tac12-0772_fig03

Inflows Withdrawals and USGS flow gages

Branch 1 Branch 2 Branch 3 Branch 4 Branch 5 Branch 6

RM 57.4 USGS gage at Niagara (14181500)

RM 51.2 City of Gates

RM 47.5 City of Mill City

RM 38.7 USGS gage at Mehama (14183000)

RM 31 City of Salem

RM 29.5 City of Stayton; Santiam Water Control District

RM 27 NORPAC Foods

RM 19.6 Sidney Irrigation Cooperative

South Santiam River RM 11.7

Jefferson Wastewater Treatment Plant RM 9

RM 9.7 USGS gage at Jefferson (14189000)

RM 9.5 City of Jefferson

Stayton Wastewater Treatment Plant RM 27.5

Little North Santiam River RM 39.2

 Rock Creek RM 49.3

RM 29.5 City of Stayton; Santiam Water Control District

Figure 3. Locations of point-source and tributary inflows, withdrawals, and USGS streamflowgaging stations in the North Santiam and Santiam Rivers downstream of Big Cliff Dam, Oregon. 

(Diagram reproduced from Sullivan and Rounds, 2004.)
Methods 9

The historical data were analyzed based primarily on 

the assumption that streamflow, along with meteorological 

conditions, is one of the most important factors 

influencing stream temperatures in Detroit Lake, Big Cliff 

Reservoir, and the North Santiam River. In many years, 

above‐average streamflow (driven by snowmelt) during 

April– June can translate into above-average streamflow 

during July– September; therefore, the timing of runoff 

from snowmelt and precipitation may affect midsummer 

temperatures, and the development of these environmental 

forcing scenarios must take this relationship into account. 

Because streamflow and water temperature typically 

exhibit less year-to-year variability in late summer 

(August– September) prior to the autumn rainy season, 

and because years with a wet winter and spring do not 

necessarily have a wet autumn, the historical data were 

divided and analyzed in two periods: “winter–summer” 

(January– September) and “autumn” (October–December). 

In this way, measured data from a year with a dry (or wet) 

winter–summer could be concatenated with measured data 

from a year with a dry (or wet) autumn, producing a moreor-less uniformly dry (or wet) environmental scenario 

for modeling that has streamflow, water-temperature, and 

meteorological data that are consistent with one another. 

Dividing the year at the beginning of October not only 

made it easier to splice and transition model input data from 

separate years, but also takes advantage of the fact that 

autumn streamflow conditions, once the rainy season begins, 

are largely independent of the snowpack from the preceding 

winter and spring.

To select scenarios with the most realistic range in 

possible streamflow and water temperature throughout the 

year, a method was devised to rank 10 recent years in which 

adequate streamflow, water-temperature, and meteorological 

data were available (2000–2009), using monthly mean 

flow and temperature data from the North Santiam River 

below Boulder Creek site upstream of Detroit Lake (USGS 

site 14178000). In order to avoid a high-flow bias in the 

monthly flow comparisons, the monthly streamflow was logtransformed prior to computing a difference between each 

month’s flow and the long-term monthly median streamflow. 

This method allows the low-flow months to be compared 

more equally with high-flow months, and the differences 

between years can be assessed more clearly. To rank a group 

of months in each year, the sum of the differences between 

the log-transformed monthly mean streamflow and the 

log-transformed median of the monthly mean streamflow 

over the entire period of record (1929–2009) was computed 

and compared for the years 2000–2009. Results for the 

January–September and October–December time frames are 

shown in table 1. The same procedure was applied to stream 

temperature data from the same site using a historical period 

of record of 1975–2009. This ranking procedure was used to 

guide further exploration of the hydrologic conditions that 

occurred in each year.

The rankings in table 1 and a visual comparison of 

the monthly data were used to develop three scenarios 

representing cool/wet, normal, and hot/dry conditions based 

primarily on the rankings for streamflow. For example, the 

normal scenario was created by concatenating data from 

January 1 to September 27, 2006, with data from September 

27 to December 31, 2009 (table 2). Concatenation dates in 

table 2 were selected based on the day in which streamflow 

and meteorological conditions closely matched in the 2 years 

of interest. Streamflow and stream temperature during the 

three selected scenarios (cool/wet, normal, and hot/dry) are 

shown in figures 4 and 5. Because a large amount of variation 

in streamflow historically occurs during January to September, 

the three “winter–summer” scenarios were differentiated 

primarily by the quantity of streamflow occurring during the 

spring snowmelt period.

Table 1. Ranking of streamflow and water-temperature 

conditions at USGS gaging station 14178000 (North Santiam 

River below Boulder Creek, Oregon) for two periods in each 

calendar year, 2000–2009.

[Ranks were calculated as log(monthly mean streamflow)–log(median 

monthly streamflow over entire period of record) and log(monthly mean 

temperature)–log(median monthly temperature over entire period of 

record). Low ranks for streamflow indicate lower flows; low ranks for 

temperature indicate lower temperatures. Colors indicate months that 

were concatenated for three scenarios: cool/wet = blue; normal = purple; 

and hot/dry = red]

Year Spring–Summer Autumn–Winter

Streamflow Temperature Streamflow Temperature

2000 7 4 2 2

2001 1 8 7 9.5

2002 9 3 1 6

2003 5 10 3 7

2004 4 9 4 9.5

2005 2 7 8 5

2006 6 5 10 8

2007 3 6 9 4

2008 10 1 5 3

2009 8 2 6 1

Table 2. Description of environmental scenarios, North Santiam 

River, Oregon.

Environmental 

forcings

Measured time-frame Concatenate 

date 

(month-day) Spring/Summer Autumn/Winter

cool/wet 2009 2006 10-12

normal 2006 2009 09-27

hot/dry 2005 2002 09-27
10 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

tac12-0772_fig04

Month

North Santiam River below Boulder Creek, monthly mean discharge, in cubic feet per second 

300

400

500

600

700

800

900

1,000

1,500

2,000

2,500

3,000

Scenario

cool/wet (2009, 2006)

normal (2006, 2009)

hot/dry (2005, 2002)

Percentile

25–75

10–25 and 75–90

50

EXPLANATION

10

25

50

75

90

January February March April May June July August September October November December

Figure 4. Monthly mean discharge in the North Santiam River below Boulder Creek (USGS station 14178000) under three 

scenarios, North Santiam River, Oregon. The calendar years in the explanation parentheses denote the 2 years from which 

data were drawn and concatenated for the January–September and October–December periods.

Together, the three environmental forcing scenarios span 

more than the 25th–75th percentiles (interquartile range) of the 

historical data and do not exceed the 10th or 90th percentiles 

(the central 80 percent of the data used to indicate skewness) 

of streamflow and temperature. These environmental 

scenarios, therefore, encompass much of the typical variability 

in streamflow and water temperature, but without including 

rare and extreme hydrologic conditions. Most importantly, the 

normal scenario is very near the median streamflow for much 

of the year aside from January, March, and December. 

Streamflow under the hot/dry scenario is near the 25th 

percentile for the entire year, whereas monthly mean stream 

temperature is above the median for the entire year except for 

October and November. The result is a warm and dry scenario. 

Aside from February and October, monthly mean 

streamflow under the cool/wet scenario is above the median 

for the entire year. Interestingly, the extremely high flows 

occurring during autumn of the cool/wet scenario correspond 

to above average stream temperatures (probably due to direct 

rainfall-runoff), whereas the high flows occurring earlier in the 

year produced below average stream temperatures (probably 

due to snowmelt). These results confirm the dependence of 

North Santiam River stream temperatures on snowmelt from 

the Cascade Range. Farther downstream, however, river 

temperatures will depend greatly on dam operations and 

meteorological conditions.
Methods 11

tac12-0772_fig05

EXPLANATION

Scenario

cool/wet (2009, 2006)

normal (2006, 2009)

hot/dry (2005, 2002)

Percentile

25–75

10–25 and 75–90

50

Month

North Santiam River near Boulder Creek, water temperature, in degrees Celsius 

35.6

32.0

39.2

42.8

46.4

50.0

53.6

57.2

60.8

2

0

4

6

8

10

12

14

16

10

25

50

75

90

North Santiam River, near Boulder Creek, water temperature, in degrees Fahrenheit 

January February March April May June July August September October November December

Figure 5. Monthly mean stream temperature in the North Santiam River below Boulder Creek (USGS site 14178000) under 

three scenarios, North Santiam River, Oregon. The years in the explanation parentheses denote the 2 years from which 

data were drawn and concatenated for the January–September and October–December periods.

Without-Dam Water Temperature Estimation

Hourly water temperatures for the North Santiam River 

at Detroit Dam (RM 60.9) were estimated for a “no-dams” 

scenario, in which Detroit Dam does not exist, for the hot/dry, 

normal, and cool/wet environmental scenarios. The estimates 

were computed using a simple mass and energy balance 

approach combined with a nominal downstream warming rate 

applied during summer, following methods documented by 

Rounds (2010). Although a simple one-dimensional model 

could have been constructed and applied to estimate withoutdam water temperatures, a rigorous model was not necessary 

because these estimates were used only to provide a context 

for the results of the larger study. With a maximum estimated 

error of 0.5–0.8°C (Rounds, 2010) over a relatively short 

9-mi reach, the simple mass and energy balance method also 

is likely to be just as accurate and much easier to develop and 

apply than a one-dimensional model.
12 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

The mass and energy balance method was relatively easy 

to apply because the three major streams entering Detroit 

Lake have continuous data collection for both streamflow and 

water temperature during the period 2000–11. Monitoring 

sites on these three streams are the North Santiam River below 

Boulder Creek near Detroit (station 14178000), Breitenbush 

River above French Creek near Detroit (station 14179000), 

and Blowout Creek near Detroit (station 14180300) (see 

fig. 1). Applying a mass and energy balance to mix these 

threes streams together produces the following equation:

T Q T +Q T +Q T )/(Q +Q +Q

where

T is mixe

est NS NS BB BB BL BL NS BB BL

est

= ( )

d water temperature estimate in degrees

Celsius,

Q is me NS asured streamflow in the North Santiam 

River at station 14178000 in cubic feet

per second,

T is measured water te NS mperature in the North

Santiam River at station 14178000 in

degrees Celsius,

Q is measured streamflow in the Brei BB tenbush 

River at station 14179000 in cubic feet

per second,

T is measured water temperature in the

Breitenbush Ri

BB

ver at station 14179000 

in degrees Celsius,

Q is measure BL d streamflow in Blowout Creek

at station 14180300 in cubic feet per 

second, and

T is measured water temperature i BL n Blowout 

Creek at station 14180300 in degrees

Celsius.

(1)

These hourly water-temperature estimates then were 

adjusted to account for the instream warming that may occur 

as water traverses the 9-mi reach between the upstream end 

of Detroit Lake (where the three tributaries were assumed 

to join and mix) and Detroit Dam. From November 1 to 

April 13, or any time of the year when water temperatures 

were less than 6°C, no adjustments were made to the hourly 

water temperature estimates. From April 14 to October 31, 

a downstream warming rate was applied as a function of 

the mixed temperature estimate, based on an assumption 

that warmer water was an indication of conditions that were 

favorable for some warming. All hourly water temperature 

estimates greater than 14°C were increased by 0.99°C to 

account for a nominal maximum downstream warming rate of 

0.11°C/mi over the 9-mi reach. This maximum downstream 

warming rate was based on historical data (Moore, 1964, 

1967) as well as previous water-temperature modeling in the 

North Santiam River in the 4 mi just downstream of Big Cliff 

Dam (Rounds, 2010). Water-temperature estimates less than 

14°C but greater than 6°C were increased to account for some 

downstream warming, but less than the maximum rate of 

0.11°C/mi, using the following linear interpolation:

T T final e = + st T T est e − − ≤ ≤ st 0 9. ( 9 6. ) 0 1 / ( 40 60 60 . . ), . . 14 0 (2)

where Tfinal is the final interpolated water temperature estimate 

in degrees Celsius.

These without-dam water-temperature estimates for 

the three environmental scenarios show a more “natural” 

seasonal temperature pattern that peaks in July or August, 

in contrast to the pre-2007 downstream temperature peak in 

September or October (fig. 6). The contrast in the seasonal 

temperature pattern is more evident in the hot/dry and normal

environmental scenarios because the measured downstream 

temperatures at the Niagara gage (USGS station 14181500) 

for those scenarios came primarily from years prior to the 

operational changes that occurred in 2007 to more actively 

manage the temperature releases from Detroit Dam. The 

difference is less evident for the cool/wet environmental 

scenario because reservoir operations through September in 

that scenario were different and were influenced by a desire to 

better manage downstream temperatures.

A comparison of mean annual water temperatures with 

or without the dams showed a negligible difference (less 

than 0.5°C, table 3). Therefore, the main effect of the dams 

is to change the seasonal pattern in downstream temperatures 

and the timing and magnitude of the annual maximum and 

minimum, rather than to increase or decrease temperatures 

overall. 

Temperature Targets

Temperature targets for reservoir releases were 

previously developed and used by USACE for the McKenzie 

River system downstream of another dam (Cougar Dam on 

the South Fork McKenzie River) to support a restoration 

of uses by endangered fish (U.S. Army Corps of Engineers, 

2012). Because no fish-based reservoir release targets had 

been developed for the North Santiam River, and because 

the endangered fish species are similar in the two systems, 

the McKenzie River temperature targets were applied in 

this study. ODEQ had developed some temperature targets 

for reservoir releases as part of the Willamette River watertemperature TMDL (Oregon Department of Environmental 

Quality, 2006), but those targets were based on an analysis of 

the historical data rather than the needs of the fish. Similarly, 

the maximum temperature criteria embedded in Oregon’s 

temperature standard, while meant to be protective for fish, 

include less seasonal variation than the USACE targets. 
Methods 13

tac12-0772_fig06

32

36

40

44

48

52

56

60

64

68

cool/wet wod at DET daily mean

cool/wet wod at DET daily max/min

cool/wet USGS 14181500 daily mean

cool/wet USGS 14181500 daily max/min

32

36

40

44

48

52

56

60

64

68

0

2.2

4.4

6.7

8.9

11.1

13.3

15.6

17.8

0

2.2

4.4

6.7

8.9

11.1

13.3

15.6

17.8

0

2.2

4.4

6.7

8.9

11.1

13.3

15.6

17.8

20.0

20.0

20.0

normal wod at DET daily mean

normal wod at DET daily max/min

normal USGS 14181500 daily mean

normal USGS 14181500 daily max/min

01/0101/1501/2902/1202/2603/1203/2604/0904/2305/0705/2106/0406/1807/0207/1607/3008/1308/2709/1009/2410/0810/2211/0511/1912/0312/1712/31

32

36

40

44

48

52

56

60

64

68

hot/dry wod at DET daily mean

hot/dry wod at DET daily max/min

hot/dry USGS 14181500 daily mean

hot/dry USGS 14181500 daily max/min

Calendar month/day

Temperature, in degrees Celsius 

Temperature, in degrees Fahrenheit 

EXPLANATION

EXPLANATION

EXPLANATION

A.

B.

C.

Figure 6. Estimated without-dam water temperatures (labeled “wod”) at the Detroit Dam site (DET) compared to 

measured (USGS station 14181500) hourly water temperatures for the three environmental scenarios, North Santiam 

River, Oregon. (A) cool/wet (2009 spliced with 2006), (B) normal (2006 spliced with 2009), and (C) hot/dry (2005 spliced 

with 2002).

Table 3. Mean, minimum, and maximum annual without-dam temperature estimates (labeled 

“W/o-dams”) at Detroit Dam (river mile 60.9) along with measured mean, minimum, and maximum 

annual with-dam temperatures (labeled “With-dams”) at USGS gaging station 14181500 (river mile 

57.3) for three environmental scenarios, North Santiam River, Oregon.

[*Measured 14181500 river mile 57.3: Missing period January 12–16, 2009]

Water temperature, in degrees Celsius

Cool/wet Normal Hot/dry

W/o-dams With-dams* W/o-dams With-dams W/o-dams With-dams

Mean 7.46 7.92 7.60 7.64 7.96 8.15

Minimum 1.37 3.50 0.03 3.70 0.71 4.50

Maximum 17.83 18.30 18.36 13.00 17.69 13.70
14 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

Therefore, using the USACE targets seemed to be a reasonable 

choice. Although the USACE temperature targets include 

both a minimum and maximum monthly value for much of 

the calendar year, only the maximum values were used for the 

majority of model runs in this study (scenario names include 

“max” to denote this practice). 

Estimated without-dam water temperatures at the Detroit 

Dam site also were used as temperature targets for selected 

model scenarios. Using the without-dam temperatures as 

release targets provided a way to measure the ability of 

changes in dam operations or alterations in dam outlets to 

match temperatures that might exist in the absence of Detroit 

Dam. The estimated without-dam water temperatures were 

applied as release targets in model scenarios only after first 

computing the 7dADM—the statistic used in Oregon’s 

temperature standard. That computation removed much of the 

daily variation in the without-dam temperature estimates, thus 

making them more useful as release targets. Model scenarios 

using these targets are named with “w/o_dams7dADM” to 

denote this target.

Model Setup and Usage

Dam Outflow Estimation

Detroit Dam

Prior to running the Detroit Lake model to simulate 

operational and structural scenarios at Detroit Dam, the 

previously developed USGS Detroit Lake model was set 

up and its calibration checked using measured inflows, 

outflows, and weather conditions for the entire calendar year 

of 2011 (see appendix B) and from January 1 to August 30 

in each environmental scenario. The only adjustments to the 

calibrated model parameters from the original model were 

(1) an additional spillway outlet was added as a “LINE” type 

structure with a model “WIDTH” of 25 m (82 ft) and an 

elevation (STR ELEV) of 469.7 m (1,541 ft), and (2) a minor 

change was made to the wind-sheltering coefficients to better 

reflect the distribution of wind speed across Detroit Lake. 

Wind sheltering was decreased from 1.0 to 0.9 and increased 

from 1.0 to 1.2 for model segments upstream and downstream 

of the Blowout Creek arm of the lake (model segment 21), 

respectively. 

After the model was set up for each environmental 

scenario, the difference between measured and modeled 

forebay elevations in the lake was used to determine the 

quantity of ungaged inflows and outflows for the lake. An 

additional model input known as the distributed tributary 

was created to account for any unmeasured overland flows, 

evaporation, or groundwater flux not accounted for by other 

boundary conditions, serving to balance the water budget for 

the lake. This method worked for the period from January 1 to 

the concatenation date of the environmental scenario because 

measured inputs and a corresponding measured lake level 

were available. From the concatenation date to December 31, 

however, the environmental scenario switched to inflows from 

a different year, making measured lake level comparisons 

impossible. Therefore, a proportion of the inflow from each 

tributary was used to estimate the magnitude of the distributed 

tributary from the concatenation date to December 31 of each 

environmental scenario. 

Following the water balance calibration, certain scenarios 

required that the total release rates (outflows) from Detroit 

Dam met the following conditions:

1. Releases from Detroit Dam should meet minimum and 

maximum flow requirements as specified by the BiOP 

(National Marine Fisheries Service, 2008) (table 4).

2. Computed water levels in Detroit Lake should not exceed 

the reservoir rule curve for more than 5 days.

3. Use of the power penstock outlets for “power peaking” 

was assumed to occur during the hours of 0500–1200 and 

1400–2200 each day

In reality, “power peaking” pertains only to the power 

penstock outlets; however, to enable the blending subroutine 

in CE-QUAL-W2 to determine the optimum balance of 

releases to meet downstream temperature targets, all outlets 

had to be placed on this flow schedule and used concurrently. 

Such concurrent releases might not reflect actual future 

operations, and the timing of releases (concurrent versus 

staggered) can have an effect on daily temperature variations 

immediately downstream; therefore, more detailed modeling 

may be required to optimize actual dam operations once a 

reasonable scenario is selected. The power peaking schedule 

was used only on days in which the daily average release rate 

was less than 2,472 ft3/s (70 m3/s). This rule helped ease the 

water balance of the downstream Big Cliff Reservoir model 

and came closer to the way in which Detroit Dam is operated 

during large storm events.

For the “existing” structural scenario group (use 

of existing outlets), the computed total release rate was 

distributed among the available outlets. During times in which 

the forebay elevation in Detroit Lake was computed to be 

above the spillway, the total outflow was routed to the spillway 

and power penstocks, a combination that allows access to 

warm water near the lake surface (spillway) and cooler water 

at depth (power penstocks), thus achieving a blend of releases 

that is best positioned to meet the specified temperature target. 

When the elevation in the lake was computed to fall below 

the spillway crest, the only available outlets at Detroit Dam 

were the power penstocks and the upper ROs. The lower 

ROs are located below the power penstocks and upper ROs, 

but usage of those outlets may only be possible at extremely 

low lake levels and was not assessed in this study. Under the 

“base” operational scenario group, the rules for dam releases 

that are currently in use by USACE were applied to each 

environmental scenario.
Methods 15

Big Cliff Dam

To simulate outflows at Big Cliff Dam that closely 

approximated reality and balanced inflows with outflows for 

Big Cliff Reservoir under a range of conditions, a method 

of estimating outflows at Big Cliff Dam was developed. 

The outflow at Big Cliff Dam was assumed to be a moving 

daily average of the outflow rate from Detroit Dam. The 

upper and lower bounds of the pool elevation in Big Cliff 

Reservoir (1,182 and 1,194 ft) made it necessary to add a 

substantial distributed tributary inflow to the Big Cliff model 

that accounted for several tributary inflows and balanced 

inflows with outflows while adhering to these narrow 

elevation bounds. Initially, a distributed tributary flow rate 

was calculated by the hourly difference between the calculated 

outflow from Big Cliff Dam (as described in the previous 

sentence) and the total inflows to Big Cliff Reservoir. An 

iterative process then was used to adjust this distributed 

tributary based on the difference between subsequent modeled 

water-level elevations and a mean pool elevation of 1,188 ft. 

This resulted in simulations of Big Cliff Reservoir that 

both resembled current operating elevation rules and led to 

simulations with a relatively constant pool elevation (further 

discussion in appendix B).

The simulated temperatures from the Big Cliff Reservoir 

model under these operating rules was assessed by a 

comparison to measured vertical profiles of water temperature 

from a thermistor string in Big Cliff Reservoir and a 

comparison of simulated outflow temperatures to measured 

temperatures at the streamgage downstream of Big Cliff Dam 

at Niagara (USGS gaging station 14181500) during 2011 

(further discussion in appendix B).

Meteorological Inputs

Hourly meteorological input data required for 

CE-QUAL-W2 include air temperature, dew-point 

temperature, wind speed, wind direction, short-wave solar 

radiation, and cloud cover. The same meteorological data 

in a particular environmental scenario were used as input 

to all three models of Detroit Lake, Big Cliff Reservoir, 

and the North Santiam/Santiam River. Air temperature, 

relative humidity, wind speed, and wind direction data were 

measured hourly at a Remote Automated Weather Station 

(RAWS) site near Stayton, Oregon (44° 45’ N, 122° 52’ W, 

155-m [509 ft] elevation). Hourly short-wave solar radiation 

data were obtained from the University of Oregon’s Solar 

Table 4. Minimum and maximum Detroit Dam outflow requirements for operational 

scenarios, North Santiam River, Oregon.

[Details for operational scenarios shown in table 5. Flows are daily mean streamflow, in cubic feet 

per second (ft3/s). Altered flows are indicated by the numbers in italics. Other rules incorporated 

in outflow estimation: Daily maximum flow, 15,000 ft3/s; Maximum flow through power penstocks, 

2,472 ft3/s. –, no maximum]

Month/

day

Operational scenario group minimum flows (ft3

/s)

base fixed_

elevation late_refill early_dd delay_dd1 delay_dd2

Minimum flow

Jan. 1 1,200 1,200 1,200 1,200 1,200 1,200

Feb. 1 1,000 1,000 1,000 1,000 1,000 1,000

Mar. 1 1,000 1,000 1,000 1,000 1,000 1,000

Mar. 16 1,500 1,500 1,500 1,500 1,500 1,500

Apr. 1 1,500 1,500 1,500 1,500 1,500 1,500

May 1 1,580 1,580 1,580 1,580 880 1,580

May 16 1,580 1,580 1,580 1,580 880 1,580

June 1 1,280 880 580 880 880 1,280

July 1 1,280 880 580 880 880 1,280

July 16 1,080 580 580 580 880 1,080

Sept. 1 1,500 580 580 580 880 580

Oct. 1 1,200 580 1,200 1,200 1,200 1,200

Dec. 1 1,200 580 1,200 1,200 1,200 1,200

Dec. 31 1,200 580 1,200 1,200 1,200 1,200

Maximum flow

Jan. 1 – 15,000 15,000 15,000 15,000 15,000

Sept. 1 3,000 3,000 3,000 3,000 3,000 3,000

Sept. 30 3,000 3,000 3,000 3,000 3,000 3,000

Dec. 31 – 15,000 15,000 15,000 15,000 15,000
16 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

Radiation Monitoring Laboratory (SRML) at their Eugene 

monitoring station (44° 2’ 60” N, 123° 4’ 12” W, 150 m 

[492 ft] elevation). Daytime cloud-cover data were estimated 

by comparing computed theoretical solar radiation rates 

with measured solar radiation rates as described by Sullivan 

and Rounds (2004). Nighttime cloud-cover data were 

interpolated from cloud-cover estimates at sunset on one day 

to corresponding estimates at sunrise on the following day.

Detroit Dam Scenarios and Naming Convention

A range of model scenarios at Detroit Dam were explored 

to evaluate the potential downstream temperature impacts 

of altered dam operations as well as hypothetical structural 

changes at Detroit Dam. Hypothetical dam operation scenarios 

were developed to evaluate the effects of (1) altering the lake 

level in autumn (early or delayed drawdown to make room 

for flood storage), which often necessitated some change to 

the minimum recommended release rates, and (2) placing 

specific minimum flow constraints on selected outlets to 

achieve certain outcomes such as a minimum amount of power 

generation (table 5). In order to change the seasonal pattern 

or schedule of lake-level elevations, summertime minimum 

releases from Detroit Dam had to be decreased to varying 

degrees (table 4). The set of structural scenarios included the 

existing outlets as well as the use of new floating (at a fixed 

depth) or sliding-gate (variable-elevation) outlets either alone, 

together, or in combination with an existing fixed-elevation 

outlet (table 6).

Selected operational scenarios were combined with 

selected structural scenarios, projected onto the three 

environmental forcing conditions (cool/wet, normal, and 

hot/dry) and given a set of temperature target requirements 

to produce the model scenarios of interest (table 7). The 

combination of these four conditions—operational scenario, 

structural scenario, environmental scenario, and temperature 

target—fully describes the major differences between the 

model scenarios and provides a consistent naming convention.

Table 5. Operational scenario group descriptions, Detroit Dam, North Santiam River, Oregon.

[ft3/s, cubic foot per second; NA, not applicable]

Operational scenario 

groups

Minimum outflow rules Important dates

Rules governing 

total outflow 

Minimum outflow 

to power

(percent)

 Outflow rule for 

floating outlet

Refill 

begins

Drawdown 

begins

“base” Existing operational rules following BIOP 

minimum flow requirements

40 NA Feb. 1 Sept. 1

“10ppmin” 10 No minimum Feb. 1 Sept. 1

“20ppmin” 20 No minimum Feb. 1 Sept. 1

“noppmin” No minimum No minimum Feb. 1 Sept. 1

“nomins” No minimum No minimum Feb. 1 Sept. 1

“400fmin” No minimum 400 ft3/s minimum Feb. 1 Sept. 1

“400f” 40 400 ft3/s fixed Feb. 1 Sept. 1

“fixed_elevation” Decreased minimum flow requirements 

June 1–Dec. 31; constant pool elevation 

of 1,440 feet year-round

40 NA NA NA

“late_refill” Decreased minimum flow requirements 

during the summer

40 NA June 1 Sept. 1

“early_dd” Decreased minimum flow requirements 

June 1–Sept. 1

40 NA Feb. 1 Aug. 15

“delay_dd1” Decreased minimum flow requirements 

May 1–Oct. 15

40 NA Feb. 1 Sept. 1

“delay_dd1_noppmin” No minimum NA Feb. 1 Sept. 1

“delay_dd2” Decreased minimum flow requirements 

Sept. 1–Oct. 15

40 NA Feb. 1 Oct. 15

“delay_dd2_noppmin” No minimum NA Feb. 1 Oct. 15
Methods 17

Table 6. Structural scenarios group descriptions, Detroit Dam, North Santiam River, Oregon.

Structural 

scenario groups Description of Detroit Dam model outlets Outlet priority

“existing” Existing outlets (spillway, power penstocks, and upper regulating outlet gates) Power

“pp-float” 1 floating outlet + existing power penstocks (1,420-foot elevation) Power

“uro-float” 1 floating outlet + existing upper regulating outlet gates (1,340-foot elevation) Regulating outlet

“slider1340” 1 sliding outlet from 1,340-foot elevation to the surface Sliding

“slider1340-float” 1 floating outlet + 1 sliding outlet from 1,340-foot to the surface Sliding

Table 7. Specification and naming convention of model scenarios, Detroit Dam, North Santiam River, 

Oregon.

[Scenario identifier: c, cool/wet; n, normal; h, hot/dry; wod, without dam. Bold scenarios are located in appendix. Orange

scenarios were run in Big Cliff and North Santiam River models]

Temperature 

target

Structural 

scenarios

Operational 

scenarios

Scenario identifier

Environmental forcings

cool/wet normal hot/dry

“w/o_dams7dADM” “existing” “base” cwod1 nwod1 hwod1

“noppmin” cwod2 nwod2 hwod2

“max” “existing” “base” c1 n1 h1

“noppmin” c2 n2 h2

“fixed_elevation” c3 n3 h3

“late_refill” c4 n4 h4

“early_dd” c5 n5 h5

“delay_dd1” c6 n6 h6

“delay_dd1_noppmin” c7 n7 h7

“delay_dd2” c8 n8 h8

“delay_dd2_noppmin” c9 n9 h9

“pp-float” “nomins” c10 n10 h10

“10ppmin” c11 n11 h11

“20ppmin” c12 n12 h12

“400fmin” c13 n13 h13

“uro-float” “400fmin” c14 n14 h14

“20ppmin” c15 n15 h15

“40ppmin” c16 n16 h16

“slider1340” “base” c17 n17 h17

“slider1340-float” “delay_dd2” c18 n18 h18

“400f” c19 n19 h19
18 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

Detroit Dam Operational Scenarios

Detroit Dam Reference Conditions

To compare the operational and structural model 

scenarios, specific reference conditions (entitled “base”) were 

used to represent current operational guidelines and structures 

in place at Detroit Dam. These conditions then were applied 

with the model using a set of temperature targets to show the 

extent to which current operations and structures at Detroit 

Dam were able to meet those temperature targets under the 

three environmental scenarios.

base Operational Scenario

This operational scenario was intended to provide 

simulations that reflect the guidelines, timelines, rules, 

and understandings currently in place for the operation of 

Detroit Dam under the environmental scenarios developed 

for this study (table 2). The current operational rules for 

Detroit Dam were developed for the existing usable outlet 

structures (spillways, power penstocks, and upper ROs). As 

mentioned in the section “Detroit Dam Scenarios and Naming 

Convention”, these rules are based on a combination of current 

minimum outflows (mandated by the BiOP), maximum 

outflows, downstream irrigation withdrawals, minimum power 

production requirements, and a schedule of power-peaking 

operations (base scenario in table 4 and table 5). The majority 

of operational scenarios required a minimum of 40 percent 

of the total release rate to be routed through the power 

penstocks to allow a minimum amount of power generation. 

This is consistent with a current agreement between USACE 

and the Bonneville Power Administration, which distributes 

and markets hydropower from Detroit Dam and many 

other facilities across the Pacific Northwest. All operational 

scenarios discussed in this report assigned a higher priority to 

the power penstocks whenever possible. 

Before comparing modeled outflow temperatures, it is 

helpful to compare the modeled forebay elevations in each of 

the operational scenarios, as the timing of the rule curve can 

contribute greatly to the resulting temperature regime in the 

lake. The base operational scenarios generally led to modeled 

lake levels that closely matched the USACE rule curve during 

spring and early summer. As the summer progressed into 

the low-flow months, however, minimum flow requirements 

typically led to outflows exceeding inflows and a gradual 

decrease in lake level during mid-July through mid-October 

(fig. 7). 

Modeled temperatures from the base operations and 

existing structural scenarios serve as a basis to compare other 

structural and operational scenario outcomes. In this report, 

figures of the max temperature target scenario results show 

both the minimum and maximum temperature targets currently 

used by USACE for the North Santiam River (and adapted 

from targets used for the McKenzie River, Oregon), but 

only the maximum temperature target was used to drive the 

blending algorithm within CE-QUAL-W2 for these scenarios. 

In many of the following figures, “percent spill” is defined 

as the percentage of total flow that was directed to outlets 

other than the power penstocks; thus, spill includes the total 

releases from the ROs and the spillway. Outflow temperatures 

from base operational scenarios (fig. 8) did not meet the max

temperature target during summer months (June–August), 

whereas omitting the minimum power generation constraint 

in the noppmin scenarios (fig. 9) generally allowed the model 

to be more successful at meeting the max temperature target. 

By allowing the “percent spill” to exceed 60 percent during 

the summer months (scenarios c2, n2, and h2), the model 

was allowed to release more of the warmer outflows from the 

spillway during summer, which retains some of the cooler, 

deeper water for release in autumn from the upper RO outlets 

(fig. 9). 

Without-Dams Temperature Target

To assess the potential for base operations and existing

structures at Detroit Dam to match temperatures that might 

exist in the absence of Detroit Dam, calculated temperatures 

from the without-dams analysis were smoothed using a 

7-day moving average of the daily maximum, then used as a 

temperature target in the wo_dams7dADM scenarios (table 7). 

The primary difference between the two sets of temperature 

targets used in this study (max, wo_dams7dADM) is evident 

in the allowable summer temperatures. Summer dam 

operations and release temperatures then help to determine 

the availability of cool water at the elevation of the available 

outlets later in autumn and the resulting autumn release 

temperatures (figs. 8 and 10). 

As was noted for the base and noppmin scenarios 

with max temperature targets (c1, n1, h1, c2, n2, and h2), 

the removal of minimum flow requirements to the power 

penstocks resulted in more warm surface water released 

in midsummer and cooler outflows from the upper ROs 

in autumn (compare figs. 8 and 9). The same is true when 

the wo_dams7dADM temperature targets were applied 

(compare figs. 10 and 11). The max temperature targets in 

June, early July, and late August are slightly higher than the 

wo_dams7dADM targets. As a result, midsummer release 

temperatures from the cwod2, nwod2, and hwod2 scenarios 

were slightly lower than temperatures from the c2, n2, and 

h2 scenarios during the same time frame, thus resulting in 

comparatively warmer outflow temperatures in autumn. 
Detroit Dam Operational Scenarios 19

tac12-0772_fig07

Full pool

Spillway

Inflow, in cubic feet per second

500

1,000

2,000

5,000

10,000

20,000

Outflow, in cubic feet per second

500

1,000

2,000

5,000

10,000

20,000

Calendar month/day

Elevation, in feet

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/1211/1911/2612/0312/1012/1712/2412/31

1,440

1,460

1,480

1,500

1,520

1,540

1,560

1,580

cool/wet

normal

hot/dry

Rule curve

A. EXPLANATION

B.

C.

Figure 7. Comparison of existing structural scenarios with base operational scenarios (scenarios c1, n1, h1) (A) total 

inflows, (B) total outflows, and (C) modeled water-surface elevation and rule curve, North Santiam River, Oregon. 
20 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

tac12-0772_fig08

0

38

40

42

44

46

48

50

52

54

56

58

60

62

64

3.3

4.4

5.6

6.7

7.8

8.9

10.0

11.1

12.2

13.3

14.4

15.6

16.7

17.8

Calendar month/day

Percent spill

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/1211/1911/2612/0312/1012/1712/2412/31

25

50

75

100

Temperature, in degrees Celsius 

Temperature, in degrees Fahrenheit 

Max/min ttarg

cool/wet

normal

hot/dry

A. EXPLANATION

B.

Figure 8. (A) Modeled water temperature and (B) percent spill for existing structural scenarios with base operational 

scenarios, and max temperature targets (scenarios c1, n1, h1), North Santiam River, Oregon. Percent spill is the 

percentage of total flow directed to outlets other than the power penstocks. The maximum and minimum temperature 

target established for the McKenzie River (labeled “Max/min ttarg”) is shown but only the maximum was used in this 

simulation.

EXPLANATION

38

40

42

44

46

48

50

52

54

56

58

60

62

64

3.3

4.4

5.6

6.7

7.8

8.9

10.0

11.1

12.2

13.3

14.4

15.6

16.7

17.8

Calendar month/day

Percent spill

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/1211/1911/2612/0312/1012/1712/2412/31

0

25

50

75

100

Temperature, in degrees Celsius 

Temperature, in degrees Fahrenheit 

Max/min ttarg

cool/wet

normal

hot/dry

A.

B.

Figure 9. (A) Modeled water temperature, and (B) percent spill for existing structural scenarios with noppmin

operational scenarios, and max temperature targets (scenarios c2, n2, h2), North Santiam River, Oregon. Percent 

spill is the percentage of total flow directed to outlets other than the power penstocks. The maximum and minimum 

temperature target established for the McKenzie River (labeled “Max/min ttarg”) is shown but only the maximum was 

used in this simulation.
Detroit Dam Operational Scenarios 21

tac12-0772_fig10

38

40

42

44

46

48

50

52

54

56

58

60

62

64

3.3

4.4

5.6

6.7

7.8

8.9

10.0

11.1

12.2

13.3

14.4

15.6

16.7

17.8

Calendar month/day

Percent spill

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/1211/1911/2612/0312/1012/1712/2412/31

25

0

50

75

100

Temperature, in degrees Celsius 

Temperature, in degrees Fahrenheit 

cool/wet

normal

hot/dry

A. EXPLANATION

B.

Figure 10. (A) Modeled water temperature and (B) percent spill for existing structural scenarios with base

operational scenarios and wo_dams7dADMax temperature targets (scenarios cwod1, nwod1, hwod1), North Santiam 

River, Oregon. Percent spill is the percentage of total flow directed to outlets other than the power penstocks. The 

dashed lines correspond to wo_dams7dADMax temperature targets in cool/wet (blue), normal (purple), and hot/dry

(red) scenarios.

38

40

42

44

46

48

50

52

54

56

58

60

62

64

3.3

4.4

5.6

6.7

7.8

8.9

10.0

11.1

12.2

13.3

14.4

15.6

16.7

17.8

Calendar month/day

Percent spill

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/1211/1911/2612/0312/1012/1712/2412/31

25

0

50

75

100

Temperature, in degrees Celsius 

Temperature, in degrees Fahrenheit 

cool/wet

normal

hot/dry

EXPLANATION

A.

B.

Figure 11. (A) Modeled water temperature and (B) percent spill for existing structural scenarios with noppmin

operational scenarios and wo_dams7dADMax temperature targets (scenarios cwod2, nwod2, hwod2), North Santiam 

River, Oregon. Percent spill is the percentage of total flow directed to outlets other than the power penstocks. The 

dashed lines correspond to wo_dams7dADMax temperature targets in cool/wet (blue), normal (purple), and hot/dry (red) 

scenarios.
22 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

Fixed Lake Level at Minimum Conservation Pool 

(1,450 feet)

One hypothetical operational scenario included a 

specification that the year-round Detroit Lake water-surface 

elevation be held at “minimum conservation pool” the current 

guideline used during the winter months (fig. 12). This 

fixed_elevation scenario is extreme in that it would greatly 

affect summer recreational activities on the lake, but might 

possibly have some advantages for passing fish downstream; 

this scenario might never be pursued, but resource managers 

felt it was important to assess the implications of such an 

action. This scenario also is referred to as “run-of-river” 

because outflows are approximately equivalent to total inflows 

throughout the year. Exceptions to this general rule are that 

outflows cannot fall below the minima or exceed the maxima 

shown in table 4. Outflow temperatures under fixed_elevation

scenarios exceeded the max temperature target during the 

months of September–November (fig. 13), mainly because 

any cool water deep in the lake was below the elevation of the 

power penstocks and the upper ROs.

Full pool

Spillway

Inflow, in cubic feet per second

500

1,000

2,000

5,000

10,000

20,000

Outflow, in cubic feet per second

500

1,000

2,000

5,000

10,000

20,000

Calendar month/day

Elevation, in feet

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/10

09/1709/2410/0110/0810/1510/2210/2911/0511/1211/19

11/2612/0312/1012/1712/2412/31

1,440

1,460

1,480

1,500

1,520

1,540

1,560

1,580

EXPLANATION

cool/wet fixed elevation

normal fixed elevation

hot/dry fixed elevation

Rule curve

Alt curve

A.

B.

C.

Figure 12. Comparison of fixed_elevation operational scenarios (scenarios c3, n3, h3), (A) total inflows, (B) total outflows, 

(C) modeled water-surface elevation, North Santiam River, Oregon.
Detroit Dam Operational Scenarios 23

Delayed Drawdown

Reduced Minimum Outflows

When minimum outflows were decreased in summer 

under operational scenario delay_dd1 (tables 4, 5), the lake 

remained closer to full in mid- and late-summer until the 

rule curve dictated that the lake be drafted (lowered) to make 

room for potential flood storage. In this scenario, drawdown 

typically began in mid- to late-September under all three 

environmental scenarios (fig. 14), but the rule curve was 

not modified. Decreased outflows and a higher lake level in 

midsummer meant that the spillway crest was slightly deeper 

and accessing slightly cooler water, resulting in cooler releases 

at that time compared to base operations (figs. 8, and 15). In 

contrast, keeping a higher lake level in early to mid-September 

meant that the spillway could be used later in the summer 

compared to base operations (figs. 7, and 14), allowing more 

warm water to be expelled in early September and saving 

some cooler water for release later in autumn. This generally 

led to lower outflow temperatures in autumn when compared 

to base operations (figs. 8, and 15). 

When reduced minimum outflow operations were 

adjusted to free the model from the rule directing a minimum 

40 percent outflow to the power penstocks (scenario 

delay_dd1_noppmin), the modeled release temperatures from 

Detroit Dam generally met the max temperature target in 

autumn (fig. 16). Given this scenario allowing the outlets to 

access both warm water near the lake surface and cool water 

at depth with few restrictions on minimum flows, downstream 

temperature targets generally can be met.

tac12-0772 fig13

38

40

42

44

46

48

50

52

54

56

58

60

62

64

3.3

4.4

5.6

6.7

7.8

8.9

10.0

11.1

12.2

13.3

14.4

15.6

16.7

17.8

Calendar month/day

Percent spill

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/1211/1911/2612/0312/1012/1712/2412/31

25

0

50

75

100

Temperature, in degrees Celsius 

Temperature, in degrees Fahrenheit 

EXPLANATION

Max/min ttarg

cool/wet fixed elevation

normal fixed elevation

hot/dry fixed elevation

A.

B.

Figure 13. (A) Modeled water temperature and (B) percent spill for existing structural scenarios with fixed elevation

operational scenarios and max temperature targets (scenarios c3, n3, h3), North Santiam River, Oregon. The maximum 

and minimum temperature target established for the McKenzie River (labeled “Max/min ttarg”) is shown but only the 

maximum was used in this simulation.
24 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

Reduced Minimum Outflows and Modified 

Rule Curve

Another way to keep more water in the lake and retain 

the use of the spillway in late summer is to modify the rule 

curve, keeping the target lake level higher late in the season 

and delaying the drawdown that is done to make room for 

potential flood storage. To examine the effects of delaying 

drawdown by about two months while minimizing reductions 

to summertime base operational scenario minimum releases, 

the “delay_dd2” operational scenario was developed (tables 4, 

5). In this scenario, minimum releases were not decreased 

in midsummer as in the delay_dd1 operations; minimum 

releases were only modified after September 1. Drawdown 

under delay_dd2 typically began in late-October under all 

environmental scenarios except for hot/dry (fig. 17), in which 

minimum summertime outflow rules did not allow for the lake 

to remain above the spillway any later than it did under base

operations. This scenario led to temperature management in 

autumn that generally was more successful than under base

operations (compare figs. 8, and 18). During October and 

November, the cool/wet and normal scenarios under delay_

dd2 operations resulted in simulated outflow temperatures that 

generally did not exceed the max temperature target (fig. 18). 

Results were not necessarily better than those using delay_dd1

operations (fig. 15).

tac12-0772 fig14

Full pool

Spillway

cool/wet delay dd1

normal delay dd1

hot/dry delay dd1

Rule curve

Inflow, in cubic feet per second

500

1,000

2,000

5,000

10,000

20,000

Outflow, in cubic feet per second

500

1,000

2,000

5,000

10,000

20,000

Calendar month/day

Elevation, in feet

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/1211/1911/2612/0312/1012/1712/2412/31

1,440

1,460

1,480

1,500

1,520

1,540

1,560

1,580

A. EXPLANATION

B.

C.

Figure 14. Comparison of delay_dd1 operational scenarios (scenarios c6, n6, h6), (A) total inflows, (B) total outflows, 

(C) modeled water-surface elevation, North Santiam River, Oregon.
Detroit Dam Operational Scenarios 25

tac12-0772 fig15

38

40

42

44

46

48

50

52

54

56

58

60

62

64

3.3

4.4

5.6

6.7

7.8

8.9

10.0

11.1

12.2

13.3

14.4

15.6

16.7

17.8

Calendar month/day

Percent spill

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/12

11/1911/2612/0312/1012/1712/2412/31

25

0

50

75

100

Temperature, in degrees Celsius 

Temperature, in degrees Fahrenheit 

A. EXPLANATION

B.

Max/min ttarg

cool/wet delay dd1

normal delay dd1

hot/dry delay dd1

Figure 15. (A) Modeled water temperature and (B) percent spill for existing structural scenarios with delay_dd1

operational scenarios and max temperature targets (scenarios c6, n6, h6), North Santiam River, Oregon. The maximum 

and minimum temperature target established for the McKenzie River (labeled “Max/min ttarg”) is shown but only the 

maximum was used in this simulation.

0

38

40

42

44

46

48

50

52

54

56

58

60

62

64

3.3

4.4

5.6

6.7

7.8

8.9

10.0

11.1

12.2

13.3

14.4

15.6

16.7

17.8

Calendar month/day

Percent spill

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/12

11/1911/2612/0312/1012/1712/2412/31

25

50

75

100

Temperature, in degrees Celsius 

Temperature, in degrees Fahrenheit 

A. EXPLANATION

B.

Max/min ttarg

cool/wet delay dd1 noppmin

normal delay dd1 noppmin

hot/dry delay dd1 noppmin

Figure 16. (A) Modeled water temperature and (B) percent spill for existing structural scenarios with delay_dd1_

noppmin operations and max temperature targets (scenarios c7, n7, h7), North Santiam River, Oregon. The maximum 

and minimum temperature target established for the McKenzie River (labeled “Max/min ttarg”) is shown but only the 

maximum was used in this simulation.
26 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

Combining the delayed drawdown with no minimum 

outflow to the power penstocks (delay_dd2_noppmin in 

table 5) resulted in modeled outflow temperatures from Detroit 

Dam that generally met the max temperature target during 

autumn, aside from a period in November under the hot/dry

environmental scenario that exceeded the max temperature 

target (fig. 19). As was noted for other scenarios with no 

minimum power generation, such a scenario allowed for more 

heat at the lake surface to be discharged during midsummer, 

thus meeting the max temperature target at that time and 

saving the deeper cold water for release in autumn when 

cooler releases were required by the temperature targets.

Although delaying the drawdown of the lake may be 

beneficial for downstream temperature management under 

certain conditions, such advantages must be balanced against 

the need to provide protection against potential flood damages. 

The delayed drawdown simulated in these scenarios specifies 

a drawdown of the lake that occurs primarily in November, 

which historically is one of the months with the greatest 

precipitation, leading to potentially large lake inflows. Clearly, 

if the drawdown of the lake is delayed, accurate and precise 

forecasting techniques must be used to balance the need for 

temperature management against impending needs to make 

room in the reservoir to capture high-inflow events. 

tac12-0772 fig17

Full pool

Spillway

Inflow, in cubic feet per second

500

1,000

2,000

5,000

10,000

20,000

Outflow, in cubic feet per second

500

1,000

2,000

5,000

10,000

20,000

Calendar month/day

Elevation, in feet

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/1211/1911/2612/0312/1012/1712/2412/31

1,440

1,460

1,480

1,500

1,520

1,540

1,560

1,580

EXPLANATION

cool/wet delay dd2

normal delay dd2

hot/dry delay dd2

Rule curve

A.

B.

C.

Figure 17. Comparison of delay_dd2 operational scenarios (scenarios 8, 9, and 18), (A) total inflows; (B) total outflows, 

(C) modeled water-surface elevation, North Santiam River, Oregon.
Detroit Dam Operational Scenarios 27

tac12-0772 fig18

0

Max/min ttarg

cool/wet delay dd2

normal delay dd2

hot/dry delay dd2

38

40

42

44

46

48

50

52

54

56

58

60

62

64

3.3

4.4

5.6

6.7

7.8

8.9

10.0

11.1

12.2

13.3

14.4

15.6

16.7

17.8

Calendar month/day

Percent spill

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/12

11/1911/2612/0312/1012/1712/2412/31

25

50

75

100

Temperature, in degrees Celsius 

Temperature, in degrees Fahrenheit 

A. EXPLANATION

B.

Figure 18. (A) Modeled water temperature and (B) percent spill for existing structural scenarios with delay_dd2

operations and max temperature targets (scenarios c8, n8, h8), North Santiam River, Oregon. The maximum and 

minimum temperature target established for the McKenzie River (labeled “Max/min ttarg”) is shown but only the 

maximum was used in this simulation.

38

40

42

44

46

48

50

52

54

56

58

60

62

64

3.3

4.4

5.6

6.7

7.8

8.9

10.0

11.1

12.2

13.3

14.4

15.6

16.7

17.8

Calendar month/day

Percent spill

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/12

11/1911/2612/0312/1012/1712/2412/31

25

50

75

100

Temperature, in degrees Celsius 

Temperature, in degrees Fahrenheit 

EXPLANATION

Max/min ttarg

cool/wet delay dd2 noppmin

normal delay dd2 noppmin

hot/dry delay dd2 noppmin

0

A.

B.

Figure 19. (A) Modeled water temperature and (B) percent spill for existing structural scenarios with delay_dd2_

noppmin operations and max temperature targets (scenarios c9, n9, h9), North Santiam River, Oregon. The maximum 

and minimum temperature target established for the McKenzie River (labeled “Max/min ttarg”) is shown but only the 

maximum was used in this simulation.
28 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

Detroit Dam Structural Scenarios

Structural scenarios using the Detroit Lake model were 

limited only by the three possible types of outlets that are 

available in the USGS-coded CE-QUAL-W2 v3.12 blending 

routine: fixed-elevation, floating, or sliding-gate (variableelevation). Sliding-gate outlets have user-specified vertical 

limits in the depth of the lake, whereas floating outlets are 

located at a user-defined depth below the water surface, and 

have a lower vertical limit. Similarly, sliding-gate outlets are 

positioned at a user-defined depth below the lake surface when 

the blending routine calls for such an outlet to be positioned at 

or near the lake surface. For this study, a lower vertical limit of 

1,340 ft (the elevation of the upper ROs) and a depth of 6.6 ft 

(2 m) below the lake surface were specified for all floating 

and sliding-gate outlets. Four possible combinations of fixedelevation, floating, and sliding-gate outlets, as well as the 

existing fixed-elevation outlets, were used in separate groups 

of structural scenarios in this study (table 6). 

Single Sliding-Gate Structure

Replacing all outlets at Detroit Dam with a single slidinggate assembly simplified the modeled operations greatly. 

No minimum power generation constraints were set because 

presumably any or all of the flow through the new outlet 

could be routed to the hydropower plant. The minimum and 

maximum outflow rates of the base operations still applied. 

This structural scenario was named slider1340 because the 

lower elevation limit was set at 1,340 ft, the elevation of the 

upper ROs.

Scenarios in which a single sliding-gate outlet was used 

led to modeled outflow temperatures that generally varied 

more on a daily basis compared to scenarios using more than 

one outlet (fig. 20). This tendency was especially evident in 

autumn. The large variation in release temperatures is a result 

of the sliding-gate outlet being positioned at a depth that 

often was located in or near the middle of the thermocline, 

such that any seiching of the lake caused the thermocline to 

move up and down over the course of the day and thereby 

change the temperature of the water captured by the outlet. 

The model scenario was configured so that the elevation of 

the sliding-gate outlet was adjusted by the model only once 

per day (at 0500 hours), in order to minimize demands on dam 

operators; similar criteria were used for other scenarios such 

that gate adjustments were generally only performed once a 

day. Despite the larger daily variations in release temperatures, 

use of a single sliding-gate outlet in these slider1340 scenarios 

generally allowed downstream temperature targets to be met, 

with the exception of occasional spikes in autumn and general 

exceedances during December (fig. 20).

38

40

42

44

46

48

50

52

54

56

58

60

62

64

3.3

4.4

5.6

6.7

7.8

8.9

10.0

11.1

12.2

13.3

14.4

15.6

16.7

17.8

Calendar month/day

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/12

11/1911/2612/0312/1012/1712/2412/31

Temperature, in degrees Celsius 

Temperature, in degrees Fahrenheit 

EXPLANATION

Slider elevation, in feet

1,340

1,320

1,360

1,380

1,400

1,420

1,440

1,460

1,480

1,500

1,520

1,540

1,560

1,580

Max/min ttarg

cool/wet_slider1340

normal_slider1340

hot/dry_slider1340

A.

B.

Figure 20. (A) Modeled water temperature and (B) sliding-gate elevation for slider1340 structural scenarios with base

operations and max temperature targets (scenarios c17, n17, h17), North Santiam River, Oregon. The maximum and minimum 

temperature target established for the McKenzie River (labeled “Max/min ttarg”) is shown but only the maximum was used in 

this simulation.
Detroit Dam Structural Scenarios 29

Floating and Fixed-Elevation Gates

Structural scenarios in which a fixed-elevation outlet and 

a floating outlet were used in combination (pp-float and 

uro-float) led to modeled release temperatures that were 

similar to results from scenarios with a single sliding outlet 

(slider1340), but the former generally displayed less daily 

variation than the latter. The pp-float and uro-float scenarios 

depict the existing power penstocks and upper RO gates, 

respectively, as fixed-elevation outlets used in combination 

with a new floating outlet. 

Floating Outlet with Power Penstocks

The pp-float structural scenarios specify one hypothetical 

floating outlet 6.6 ft (2 m) below the lake surface as well as a 

fixed outlet at the elevation of the existing power penstocks 

(1,402.9 ft centerline elevation). A series of operational 

scenarios were modeled in combination with these outlets to 

determine the effect of different minimum flow requirements 

to the power penstocks and the floating outlet. Results 

showed that as the minimum of the total outflow directed to 

the fixed-elevation (power) outlet was increased, the release 

temperatures generally decreased in spring and increased in 

the autumn. This effect is visible in figures 21, 22, 23, and E5

by comparing the discharge rate from the fixed outlet and the 

resulting outflow temperature in each scenario.

No Minimum Flow through Power Penstocks or 

Floating Outlet

With no minimum flow directed to either outlet, the 

model was free to optimize the release temperatures based on 

the lake temperatures near each outlet. As a result, the release 

temperatures generally met the max temperature target in 

scenarios c10 and n10. The hot/dry scenario (h10), however, 

resulted in an undesirable peak outflow temperature of about 

54°F in autumn (fig. 21). 

Fixed out, in cubic feet per second 

10

50

100

500

1,000

5,000

10,000

Floating out, in 

cubic feet per second 

10

50

100

500

1,000

5,000

10,000

Max/min ttarg

cool/wet pp−float nomins

normal pp−float nomins

hot/dry pp−float nomins

38

40

42

44

46

48

50

52

54

56

58

60

62

64

3.3

4.4

5.6

6.7

7.8

8.9

10.0

11.1

12.2

13.3

14.4

15.6

16.7

17.8

Temperature, in degrees Celsius 

Temperature, in degrees Fahrenheit 

EXPLANATION

Calendar month/day

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/12

11/1911/2612/0312/1012/1712/2412/31

A.

B.

C.

Figure 21. Results from pp-float structural scenarios with nomins operations and max temperature targets (scenarios c10, 

n10, h10), (A) modeled water temperature, (B) outflow from fixed outlet, and (C) outflow from floating outlet, North Santiam 

River, Oregon. The maximum and minimum temperature target established for the McKenzie River (labeled “Max/min ttarg”) 

is shown but only the maximum was used in this simulation.
30 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

Twenty Percent Minimum Flow through Power Penstocks

As the minimum outflow to the power penstocks is 

increased from 0 to 20 percent (scenarios c12, n12, and h12

in table 7), the amount of warm surface water that can be 

released via the floating outlet is decreased, resulting in cooler 

releases in June and July and warmer releases during autumn 

(fig. 22). The warmer releases in autumn are a direct result 

of releasing more of the deeper, cooler water in midsummer, 

which decreases the reserves of cool water at the level of the 

power penstocks and draws the thermocline down to deeper 

depths, thus pulling warmer water to the elevation of the 

power penstocks in autumn.

Minimum Flow of 400 Cubic Feet per Second through 

Floating Outlet 

The use of a floating outlet has two potential benefits. 

First, it allows continual access to warm water at the top of 

the lake in spring through autumn. Second, it can provide 

a means of collecting fish for downstream passage. Certain 

engineering design criteria and the use of the floating outlet 

for fish passage might require that the outlet be operated 

with a minimum flow rate. By placing a 400-ft3/s minimum 

outflow requirement on the floating outlet (fig. 23), the release 

temperatures are quite similar to those that result when no 

constraints are placed on either outlet (fig. 21). As with the 

Max/min ttarg

cool/wet pp−float 20ppmin

normal pp−float 20ppmin

hot/dry pp−float 20ppmin

Fixed out, in 

cubic feet per second 

10

50

100

500

1,000

5,000

10,000

Floating out, in 

cubic feet per second 

10

50

100

500

1,000

5,000

10,000

38

40

42

44

46

48

50

52

54

56

58

60

62

64

3.3

4.4

5.6

6.7

7.8

8.9

11.1

10.0

12.2

13.3

14.4

15.6

16.7

17.8

Temperature, in degrees Celsius 

Temperature, in degrees Fahrenheit 

EXPLANATION

Calendar month/day

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/12

11/1911/2612/0312/1012/1712/2412/31

A.

B.

C.

Figure 22. Results from pp-float structural scenarios with 20ppmin operations and max temperature targets 

(scenarios c12, n12, h12), (A) modeled water temperature, (B) outflow from fixed outlet, and (C) outflow from 

floating outlet, North Santiam River, Oregon. The maximum and minimum temperature target established for the 

McKenzie River (labeled “Max/min ttarg”) is shown but only the maximum was used in this simulation.
Detroit Dam Structural Scenarios 31

pp-float scenario that required no minimum flows through 

either outlet, this scenario exceeds the target temperatures 

in autumn for the hot/dry environmental scenario, mainly 

because the lake level is low under those conditions and 

neither outlet is able to access water that is deep enough to still 

be cool at that time of year. 

Floating Outlet with Upper Regulating Outlets

The uro-float structural scenarios specify one 

hypothetical floating outlet 6.6 ft (2 m) below the lake surface 

as well as a fixed outlet at the elevation of the existing upper 

ROs (centerline elevation of 1,339.9 ft). These scenarios were 

developed under the assumption that outflow from upper ROs 

could be routed to the powerhouse at Detroit Dam for power 

production; therefore, the same sort of operational scenarios 

for a minimum amount of power generation were applied. 

Similar to results from the pp-float structural scenarios, 

as the outflow directed to the fixed-elevation outlet was 

increased, the outflow temperatures generally decreased in 

spring and increased in autumn. This trend can be seen in 

figures 24, 25, and 26 by comparing the discharge from the 

fixed-elevation outlet (labeled “Fixed out”) and the outflow 

temperature in each scenario. Greater releases of cool water 

from depth in midsummer generally diminish the probability 

of meeting June and July temperature targets and deplete the 

reservoir of cool water that is available for release in autumn.

Fixed out, in cubic feet per second 

10

50

100

500

1,000

5,000

10,000

Floating out, in 

cubic feet per second 

10

50

100

500

1,000

5,000

10,000

38

40

42

44

46

48

50

52

54

56

58

60

62

64

3.3

4.4

5.6

6.7

7.8

8.9

11.1

10.0

12.2

13.3

14.4

15.6

16.7

17.8

Temperature, in degrees Celsius 

Temperature, in degrees Fahrenheit 

EXPLANATION

Calendar month/day

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/12

11/1911/2612/0312/1012/1712/2412/31

Max/min ttarg

cool/wet pp−float 400fmin

normal pp−float 400fmin

hot/dry pp−float 400fmin

A.

B.

C.

Figure 23. Results from pp-float structural scenarios with 400fmin operations and max temperature targets 

(scenarios c13, n13, h13), (A) modeled water temperature, (B) outflow from fixed outlet, and (C) outflow from floating 

outlet, North Santiam River, Oregon. The maximum and minimum temperature target established for the McKenzie 

River (labeled “Max/min ttarg”) is shown but only the maximum was used in this simulation.
32 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

Minimum Flow of 400 Cubic Feet per Second through 

Floating Outlet 

One potential floating withdrawal structure design for 

Detroit Dam would have the ability to convey fish downstream 

given a minimum flow requirement through the structure. 

When a 400-ft3/s minimum outflow requirement is placed 

on the floating outlet and no minimum flow is directed to 

the upper ROs, the result is that the vast majority of outflow 

is directed to the floating outlet during June–July to meet 

the max temperature target. This leads to cooler outflow 

temperatures in autumn, when scenarios c14, n14, and h14 

generally met the temperature target (fig. 24). Exporting 

more heat from the lake surface in midsummer allows dam 

operators to reserve more of the cool water at depth for use in 

autumn. Decreased export of water from depth in midsummer 

also means that the thermocline is not drawn down as far, 

helping to retain access to cool water below the thermocline at 

the fixed-elevation outlet in autumn.

Twenty Percent Minimum Flow through Upper ROs

Requiring at least 20 percent of the total outflow to pass 

through the upper ROs in scenarios c15, n15, and h15 results 

in releases from the ROs that do not fall below about 250 ft3/s 

during summer months. Under the uro-float_20ppmin and 

uro-float_40ppmin scenarios, it was assumed that power 

production could be routed through the upper ROs. These 

scenarios generally result in outflow temperatures close to the 

max temperature target during autumn (fig. 25), showing that 

some minimum amount of power can be generated while still 

meeting downstream temperature targets. 

tac12-0772 fig24

Max/min ttarg

cool/wet uro−float 400fmin

normal uro−float 400fmin

hot/dry uro−float 400fmin

Fixed out, in 

cubic feet per second 

10

50

100

500

1,000

5,000

10,000

Floating out, in 

cubic feet per second 

10

50

100

500

1,000

5,000

10,000

38

40

42

44

46

48

50

52

54

56

58

60

62

64

3.3

4.4

5.6

6.7

7.8

8.9

11.1

10.0

12.2

13.3

14.4

15.6

16.7

17.8

Temperature, in degrees Celsius 

Temperature, in degrees Fahrenheit 

EXPLANATION

Calendar month/day

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/12

11/1911/2612/0312/1012/1712/2412/31

A.

B.

C.

Figure 24. Results from uro-float structural scenarios with 400fmin operations and max temperature targets 

(scenarios c14, n14, h14), (A) modeled water temperature, (B) outflow from fixed outlet, and (C) outflow from floating 

outlet, North Santiam River, Oregon. The maximum and minimum temperature target established for the McKenzie 

River (labeled “Max/min ttarg”) is shown but only the maximum was used in this simulation.
Detroit Dam Structural Scenarios 33

Forty Percent Minimum Flow through Upper ROs

By increasing the minimum outflow requirement on 

the upper RO gates to 40 percent, outflow from the upper 

ROs does not fall below about 500 ft3/s during summer 

months (fig. 26B). These scenarios generally result in outflow 

temperatures that exceed the max temperature target during 

November (fig. 26A). Clearly, as more water is drawn from 

below the thermocline in midsummer, less of the cool water 

below the thermocline is accessible in autumn.

Sliding and Floating Gates

Structural scenarios using a combination of a slidinggate and a floating outlet were run to evaluate how access 

to both warm surface water and cool water at depth would 

allow downstream temperature targets to be met under a range 

of conditions. The sliding-gate outlet was assigned a lower 

vertical limit of 1,340 ft, which is similar to the elevation of 

the upper ROs. Similar to scenarios depicting a single slidinggate outlet, these slider1340-float structural scenarios resulted 

in outflow temperatures near the max temperature target for 

most of the calendar year except for the month of December.

tac12-0772 fig25

Max/min ttarg

cool/wet uro−float 20ppmin

normal uro−float 20ppmin

hot/dry uro−float 20ppmin

Fixed out, in 

cubic feet per second 

10

50

100

500

1,000

5,000

10,000

Floating out, in 

cubic feet per second 

10

50

100

500

1,000

5,000

10,000

38

40

42

44

46

48

50

52

54

56

58

60

62

64

3.3

4.4

5.6

6.7

7.8

8.9

10.0

11.1

12.2

13.3

14.4

15.6

16.7

17.8

Temperature, in degrees Celsius 

Temperature, in degrees Fahrenheit 

EXPLANATION

Calendar month/day

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/12

11/1911/2612/0312/1012/1712/2412/31

A.

B.

C.

Figure 25. Results from uro-float structural scenarios with 20ppmin operations and max temperature targets 

(scenarios c15, n15, h15), (A) modeled water temperature, (B) outflow from fixed outlet, and (C) outflow from 

floating outlet, North Santiam River, Oregon. The maximum and minimum temperature target established for the 

McKenzie River (labeled “Max/min ttarg”) is shown but only the maximum was used in this simulation.
34 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

Fixed Flow of 400 Cubic Feet per Second through 

Floating Outlet

By simulating a constant flow of 400 ft3/s to the floating 

outlet, this scenario was designed to represent the potential 

effects of a hypothetical year-round lake-surface withdrawal 

structure that might also accommodate fish passage. Results 

from scenarios c19, n19, and h19 show that max temperature 

targets generally could be met throughout the year with this 

outlet configuration (fig. 27), although the temperature target 

was actually exceeded at times in August–September due to 

the large surface outflow. The USGS-coded CE-QUAL-W2 

v3.12 blending routine does not explicitly solve for the 

mixed temperature between two outlets when a constant flow 

is designated to one outlet, so some of the exceedances in 

outflow temperature during late August and early October 

(fig. 20A) may be due to inconsistencies between the imposed 

temperature target and the blended outflow temperature 

calculated by the model. A modified blending subroutine could 

fix this problem, but the point is that this scenario can come 

close to meeting the temperature target most of the time. 

tac12-0772 fig26

Max/min ttarg

cool/wet uro−float 40ppmin

normal uro−float 40ppmin

hot/dry uro−float 40ppmin

Fixed out, in 

cubic feet per second 

10

50

100

500

1,000

5,000

10,000

Floating out, in 

cubic feet per second 

10

50

100

500

1,000

5,000

10,000

38

40

42

44

46

48

50

52

54

56

58

60

62

64

3.3

4.4

5.6

6.7

7.8

8.9

10.0

11.1

12.2

13.3

14.4

15.6

16.7

17.8

Temperature, in degrees Celsius 

Temperature, in degrees Fahrenheit 

EXPLANATION

Calendar month/day

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/16

04/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/12

11/1911/2612/0312/1012/1712/2412/31

A.

B.

C.

Figure 26. Results from uro-float structural scenarios with 40ppmin operations and max temperature targets 

(scenarios c16, n16, h16), (A) modeled water temperature, (B) outflow from fixed outlet, and (C) outflow from 

floating outlet, North Santiam River, Oregon. The minimum temperature target established for the McKenzie River 

is shown but not used in this simulation.
Downstream Effects of Selected Scenarios 35

Downstream Effects of Selected 

Scenarios 

To assess the potential downstream effects of operational 

and structural changes at Detroit Dam, the Big Cliff Reservoir 

and North Santiam-Santiam River models were used to run a 

subset of the Detroit Dam scenarios. Not all scenarios were 

run through the downstream models because the downstream 

patterns of temperature change are likely to be similar. The 

selected scenarios were chosen because of their potential 

for being adopted by USACE as they evaluate possible 

operational and/or structural changes to Detroit Dam.

Estimated Emergence Dates

The Accumulated Thermal Unit (ATU) is a “degree-day” 

type of calculation used to estimate the date on which spring 

Chinook salmon first emerge from their eggs (U.S. Army 

Corps of Engineers, 2012). The ATU calculation in this report 

is the cumulative sum of the daily average temperature (in 

degrees Fahrenheit) exceeding 32°F beginning at the typical 

peak of spring Chinook spawning on September 20. The 

estimated emergence day then is derived as the date when 

the ATU value reaches 1,750°F-day. These emergence day 

estimates are based on observed egg emergences at the Oregon 

Department of Fish and Wildlife Willamette Hatchery in 

Oakridge, Oregon, when the ATU value is 1,650–1,850°F-day 

(U.S. Army Corps of Engineers, 2012).

tac12-0772_fig27

Floating

Sliding outlet for all scenarios

Max/min ttarg

cool/wet_slider1340−float_400f

normal_slider1340−float_400f

hot/dry_slider1340−float_400f

Fixed out, in 

cubic feet per second 

10

50

100

500

1,000

5,000

10,000

38

40

42

44

46

48

50

52

54

56

58

60

62

64

3.3

4.4

5.6

6.7

7.8

8.9

10.0

11.1

12.2

13.3

14.4

15.6

16.7

17.8

Temperature, in degrees Celsius 

Temperature, in degrees Fahrenheit 

Calendar month/day

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/12

11/1911/2612/0312/1012/1712/2412/31

EXPLANATION

EXPLANATION

A.

B.

C.

Slider elvation, in feet

1,340

1,360

1,380

1,400

1,420

1,440

1,460

1,480

1,500

1,520

1,540

1,560

1,580

Figure 27. Results from slider1340-float structural scenarios with 400f operations and max temperature targets 

(scenarios c19, n19, h19), (A) modeled water temperature, (B) outflow from fixed outlet, and (C) sliding outlet 

elevation, North Santiam River, Oregon. The maximum and minimum temperature target established for the 

McKenzie River (labeled “Max/min ttarg”) is shown but only the maximum was used in this simulation.
36 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

Simulated Detroit Dam release temperatures were used 

for this computation. Some model scenarios resulted in 

estimated emergence dates that were later than December 31. 

In these cases, the simulated Detroit Dam outflow temperature 

from each respective scenario during the previous January 

and February were used to complete the ATU calculation. 

Estimated emergence dates under each Detroit Lake model 

scenario are compared and sorted according to the hot/ dry 

environmental scenario results in table 8. The hot/dry

scenarios display a somewhat worst-case potential effect that 

any Detroit Dam operational/structural scenario might have on 

downstream water temperatures during a low-flow year. 

Scenarios having only operational changes at Detroit 

Dam resulted in earlier emergence dates than did scenarios 

with structural changes or structural and operational 

changes combined, suggesting that some structural changes 

might be more beneficial for fish under hot/dry conditions. 

Operational scenarios with lower minimum power production 

requirements, which generally provided cooler release 

temperatures in autumn, resulted in later estimated emergence 

dates for each otherwise equivalent scenario. For example, 

scenario h2 (existing structures, noppmin operations, hot/dry

conditions) resulted in an emergence date 5 days later than 

h1 (existing structures, base operations, hot/dry conditions) 

(table 8). 

Emergence date estimates for many of the operational 

scenarios (c1, n1, c2, n2, c5, n5, c6, n6, c7, n7) under cool/ wet 

and normal environmental scenarios do not follow the 

same pattern as that exhibited by the hot/dry environmental 

scenarios; instead, the dates are later than those from many 

of the structural scenarios. This result is primarily caused by 

outflow temperatures that were well below the temperature 

target during early to mid-October, a time when the watersurface elevation was below the spillway crest and releases 

were limited to cooler water from the upper ROs and the 

power penstocks. The ATU computation has the advantage of 

integrating all of these conditions into a single numeric value, 

but it does not convey the rate at which the emergence date is 

approached or any sequence of events that changes that rate 

during autumn. Those changes in ATU over time are illustrated 

in figure 28, showing that many of the scenarios are likely 

to have quite different effects on the rate of egg incubation 

during autumn months (fig. 28).

Downstream of Big Cliff Dam in the North Santiam 

River, estimated emergence dates were calculated from model 

results (scenarios h1, h8, h10, h17, and h19) at the location of 

the USGS gaging station at Mehama (site 14183000, RM 38.7, 

table 9). All emergence date estimates at Mehama range from 

15 to 43 days later than those calculated at the outlet of Detroit 

Dam. The cooler water temperatures at that site are caused 

partly by cool inflows from the Little North Santiam River just 

upstream of Mehama in November–December.

Table 8. Calculated emergence day for each Detroit Lake model scenario based on the day at which the Accumulated 

Thermal Units (ATUs) for simulated release temperatures reached 1,750 degrees Fahrenheit-day, North Santiam River, Oregon.

[ATU calculated by the difference of the average daily temperature above 32 degrees Fahrenheit from September 20 through December 31. Dates in 

January and February were estimated based on model results from each environmental scenario and placed in increasing order according to the hot/ dry

scenarios. Bold text refers to scenarios with North Santiam and Santiam River model simulations. “7d_mmwod” prefix signifies the 7-day moving 

maximum of the without-dams temperature target. All other scenarios were based on the tmax temperature target]

Scenario 

identifiers

Scenario 

description

Structural 

scenario?

Estimated emergence day Rank

cool/wet normal hot/dry cool/wet normal hot/dry Average

c3,n3,h3 _fixed_elevation No Dec. 19 Dec. 24 Dec. 5 20 20 20.5 20.2

c4,n4,h4 _late_refill No Dec. 18 Dec. 13 Dec. 5 21 21 20.5 20.8

c5,n5,h5 _early_dd No Jan. 14 Jan. 5 Dec. 11 19 19 19 19.0

cwod1, nwod1,hwod1 _wod_base No Jan. 26 Jan. 13 Dec. 13 4 9.5 17.5 10.3

c1, n1, h1 _base No Jan. 24 Jan. 12 Dec. 13 5 13 17.5 11.8

cwod2, nwod2, hwod2 _wod_noppmin No Feb. 1 Jan. 18 Dec. 17 2 2 16 6.7

c2, n2, h2 _noppmin No Feb. 8 Jan. 22 Dec. 18 1 1 14.5 5.5

c12, n12, h12 _pp–float_20ppmin Yes Jan. 19 Jan. 12 Dec. 18 12.5 13 14.5 13.3

c11, n11, h11 _pp–float_10ppmin Yes Jan. 21 Jan. 14 Dec. 21 11 8 12.5 10.5

c16, n16, h16 _uro–float_40ppmin Yes Jan. 15 Jan. 6 Dec. 21 17.5 17.5 12.5 15.8

c8, n8, h8 _delay_dd2 No Jan. 16 Jan. 7 Dec. 22 16 16 10.5 14.2

c6, n6, h6 _delay_dd1 No Jan. 15 Jan. 6 Dec. 22 17.5 17.5 10.5 15.2

c10, n10, h10 _pp–float_nomins Yes Jan. 22 Jan. 15 Dec. 23 9 6 8 7.7

c13, n13, h13 _pp–float_400fmin Yes 22-Jan Jan. 15 Dec. 23 9 6 8 7.7

c19, n19, h19 _slider1340–float_400f Yes 17-Jan Jan. 12 Dec. 23 15 13 8 12.0

c9, n9, h9 _delay_dd2_noppmin No Jan. 23 Jan. 13 Dec. 26 6.5 9.5 6 7.3

c7, n7, h7 _delay_dd1_noppmin No Jan. 29 Jan. 17 Dec. 27 3 3.5 4.5 3.7

c15, n15, h15 _uro–float_20ppmin Yes Jan. 19 Jan. 12 Dec. 27 12.5 13 4.5 10.0

c18, n18, h18 _delay_dd2_slider1340-float Yes Jan. 18 Jan. 12 Dec. 28 14 13 3 10.0

c14, n14, h14 _uro–float_400fmin Yes Jan. 22 Jan. 15 Dec. 29 9 6 2 5.7

c17, n17, h17 _slider1340 Yes Jan. 23 Jan. 17 Dec. 31 6.5 3.5 1 3.7
Downstream Effects of Selected Scenarios 37

tac12-0772 fig28 cool/wet ATUs

100

500

900

1,300

1,700

Estimated emergence at 1750 ATU

normal ATUs

100

500

900

1,300

1,700

Estimated emergence at 1750 ATU

Calendar month/day

hot/dry ATUs

100

500

900

1,300

1,700

09/26 10/03 10/10 10/17 10/24 10/31 11/07 11/14 11/21 11/28 12/05 12/12 12/19 12/26 01/02 01/09 01/16 01/23

Estimated emergence at 1750 ATU

max

w/o dams7dadm

fixed elevation

base

delay dd2

slider1340

slider1340−float 400f

All other scenarios

EXPLANATION

A.

B.

C.

Figure 28. Computed progression of Accumulated Thermal Units (ATUs) for selected model scenarios, showing the different 

likely rates of egg incubation over the autumn months, North Santiam River, Oregon. Spring Chinook salmon are likely to hatch 

when the ATU reaches 1,750 degrees Fahrenheit-day. (“_max” is max temperature target, “_w/o_dams7dADM” is the 7-day 

moving average of the daily maximum of the without-dams temperature target.)
38 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

North Santiam River Temperatures

To examine the potential downstream effects of select 

scenarios at Detroit Dam, outflows from the Detroit Lake 

model were routed through the downstream Big Cliff 

Reservoir and North Santiam/Santiam River models. For 

these simulations, the South Santiam River inflow and all 

other tributary inflows to the North Santiam River were taken 

from measured conditions for the environmental scenario 

of interest. A 7-day moving average of the daily maximum 

(7dADM) water temperature in each model segment of the 

North Santiam and Santiam River model was used to display 

an image of the modeled river temperatures throughout the 

calendar year of the hot/dry environmental scenario. 

Base Case

The downstream conditions resulting from current base 

operational rules in place at Detroit Dam under the hot/dry 

environmental forcing conditions show that downstream 

river temperatures generally increase from the dam release 

temperatures, except in November and December when river 

temperatures decrease (fig. 29). Notably, the loss of spillway 

control at Detroit Dam around August 1 and the change in 

the temperature target near October 1 are apparent in the 

figure at RM 59 and can be traced through the river model 

downstream to the confluence of the North and South Santiam 

Rivers. The relatively large temperature differences due to 

operational changes at RM 59 during these times diminish 

with downstream distance through the river model. The effects 

of operational changes at Detroit Dam are reduced farther 

downstream of the confluence of the North and South Santiam 

Rivers from August through October due to the warming 

effect of the river system downstream of Big Cliff Dam. In 

early November, the North Santiam and Santiam Rivers below 

Big Cliff Dam begin to have a downstream cooling effect.

Delayed Drawdown

By reducing the minimum outflow requirements from 

Detroit and Big Cliff Dams from September 1 to October 16 as 

in operational scenario delay_dd2, the Detroit Lake water level 

remained higher than in base scenarios (compare figs. 7 and 

Table 9. Calculated emergence day at Mehema (river mile 

38.7) from the North Santiam River model were based on the 

day at which the Accumulated Thermal Units (ATUs) reached 

1,750 degrees Fahrenheit-day, North Santiam River, Oregon.

[ATU calculated by the difference of the average daily temperature above 

32 degrees Fahrenheit from September 20 through December 31. Dates in 

January and February were estimated based on model results from each 

environmental scenario. Scenarios were based on the max temperature target]

Scenario 

identifier

Scenario 

description

Structural 

scenario?

Emergence 

day Rank

h1 _base No Dec. 31 5

h10 _pp-float_nomins Yes Jan. 9 4

h17 _slider1340 Yes Jan. 15 3

h19 _slider1340-float_400f Yes Jan. 15 2

h8 _delay_dd2 No Feb. 3 1

17). However, this decreased outflow from Detroit and Big 

Cliff Dams under the h8 scenario led to downstream warming 

in the North Santiam River model results that exceeded the 

base h1 scenario. Although the outflow temperatures from 

Big Cliff Dam in h8 were cooler than those in h1 during 

autumn, the reduced flow in the North Santiam River led to 

temperatures 2–5°C warmer than in the h1 scenario (fig. 30).

Floating and Fixed-Elevation Gates 

The simulation of a hypothetical floating gate combined 

with the existing power penstock outlets (fixed-elevation 

gates) at Detroit Dam, with no minimum power-generation 

requirement (scenario h10, table 7), allows the Detroit Lake 

model to expel warm water during summer beyond the day in 

which the lake elevation falls below the spillway outlets in the 

h1 scenario. During a hot and dry year, the lake level may be 

lower than normal and not allow the use of the spillway late 

in summer; using a floating outlet circumvents this problem. 

This scenario has the effect of rationing cool water until 

later in autumn and cooling the North Santiam River about 

1°C compared to scenario h1 throughout October and the 

latter half of November (fig. 31). Although that figure shows 

substantial warming in August in scenario h10 relative to h1, 

that warming is somewhat artificial because the spillway could 

no longer be used in the h1 scenario and cooler-than-desired 

water was being released in that case.

A Single Sliding-Gate Structure

Additional flexibility and an ability to meet the cool 

temperature targets in autumn is realized in model scenario 

h17 (table 7), in which a sliding-gate outlet ranging from 2 m 

below the lake surface to the elevation of the upper ROs is 

simulated at Detroit Dam. Scenario h17 temperatures between 

Big Cliff Dam and the South Santiam River confluence were 

generally 0.5–2.5°C cooler than temperatures for scenario h1

during October and November (fig. 32). Again, the warming 

in August shown in figure 32 is somewhat artificial as a 

result of the loss of the use of the spillway in early August 

in scenario h1; scenario h17 does a better job of meeting the 

max temperature target at that time. Downstream of the South 

Santiam River confluence in the Santiam River, scenario h17

continued to have a cooling effect throughout autumn as water 

temperatures remained as much as 1°C cooler than the h1

scenario from mid-October to mid-December. 

Floating and Sliding-Gate Structures

Similar to the sliding-gate-only structural scenario h17, 

scenario h19 specified the use of the same sliding-gate outlet 

with a lower vertical limit of 1,340 ft, but added a floating 

outlet with a fixed outflow year-round of 400 ft3/s (table 7). 

This scenario resulted in autumn release temperatures that 

were cooler than h1 (0.5–11.5°C in October and 1.5–3.0°C in 

November) from RMs 59 to 40 (fig. 33). Downstream of the 

confluence of the Santiam River near RM 12, the temperature 

effects from h19 are similar to h17.
Downstream Effects of Selected Scenarios 39

tac12-0772_fig29

River mile

Calendar month/day

0 5 15 25 35 45 55 59

12−27

12−01

11−01

10−01

09−01

08−01

07−01

06−01

05−01

04−01

03−01

02−01

Rock

Creek

Little North

Santiam River

South Santiam

River

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Temperature, in degrees Celsius

32 35.6 39.2 42.8 46.4 50 53.6 57.2 60.8 64.4 68 71.6 75.2

Temperature, in degrees Fahrenheit

EXPLANATION

Figure 29. Simulated 7-day moving average of the daily maximum water temperature from the North Santiam and Santiam 

River model under hot/dry environmental conditions and base operations. 
40 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

tac12-0772_fig30

River mile

Calendar month−day

0 5 15 25 35 45 55

10−05

09−01

08−01

07−01

06−01

05−01

Rock

Creek

Little North

Santiam River

South Santiam

River

4 6 8 1210 16

39.2 42.8 46.4 50.0 53.6 60.8

Temperature at DET,

in degrees Celsius

Temperature at DET,

in degrees Fahrenheit

−3 −2.5 −2 −1.5 −1 −0.5 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6

Temperature difference, in degrees Celsius

−0.2 0.2

−5.4 −3.6 −1.8 0.9 1.8 2.7 3.6 4.5 5.4 6.3 7.2 8.1 9 9.9 10.8

Temperature difference, in degrees Fahrenheit

−0.4 0.4

0

0

EXPLANATION

delay_dd2

base

Temperature target

A. B.

57.2 64.4

14 18

Figure 30. (A) Difference between the 7-day moving average of the daily maximum water temperature from the North 

Santiam and Santiam River model scenarios h8 (existing structures, delay_dd2 operations, and hot/dry conditions) and h1

(existing structures and base operations). Positive numbers indicate warming in the h8 scenario relative to the h1 scenario; 

a white color indicates an absolute change of less than 0.2°C. (B) Comparison of the max temperature target and simulated 

outflow temperatures at Detroit Dam from scenarios h8 (labeled “delay_dd2”) and h1 (labeled “base”).
Downstream Effects of Selected Scenarios 41

Figure 31. (A) Difference between the 7-day moving average of the daily maximum water temperature from the North 

Santiam and Santiam River model scenarios h10 (pp-float structures, nomins operations, and hot/dry conditions) and h1

(existing structures and base operations). Positive numbers indicate warming in the h10 scenario relative to the h1 scenario; 

a white color indicates an absolute change of less than 0.2°C. (B) Comparison of the max temperature target and simulated 

outflow temperatures at Detroit Dam from scenarios h10 (labeled “pp-float_nomins”) and h1 (labeled “base”). tac12-0772_fig31

pp−float nomins

base

Temperature target

River mile

Calendar month−day

0 5 15 25 35 45 55

10−01

09−01

08−01

07−01

06−01

05−01

Rock

Creek

Little North

Santiam River

South Santiam

River

Temperature at DET,

in degrees Celsius

Temperature at DET,

in degrees Fahrenheit

−3 −2.5 −2 −1.5 −1 −0.5 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6

Temperature difference, in degrees Celsius

−0.2 0.2

−5.4 −3.6 −1.8 0.9 1.8 2.7 3.6 4.5 5.4 6.3 7.2 8.1 9 9.9 10.8

Temperature difference, in degrees Fahrenheit

−0.4 0.4

0

0

EXPLANATION

A. B.

11−01

12−01

12−27 4 6 8 1210 16

39.2 42.8 46.4 50.0 53.6 60.857.2 64.4

14 18
42 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

tac12-0772_fig32

12−27

12−01

11−01

10−01

09−01

08−01

07−01

06−01

05−01

slider1340

base

Temperature target

River mile

Calendar month−day

0 5 15 25 35 45 55 Rock Creek Little North Santiam River South Santiam River

Temperature at DET,

in degrees Celsius

Temperature at DET,

in degrees Fahrenheit

−3 −2.5 −2 −1.5 −1 −0.5 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6

Temperature difference, in degrees Celsius

−0.2 0.2

−5.4 −3.6 −1.8 0.9 1.8 2.7 3.6 4.5 5.4 6.3 7.2 8.1 9 9.9 10.8

Temperature difference, in degrees Fahrenheit

−0.4 0.4

0

0

EXPLANATION

A. B.

4 6 8 1210 16

39.2 42.8 46.4 50.0 53.6 60.857.2 64.4

14 18

Figure 32. (A) Difference between the 7-day moving average of the daily maximum water temperature from the North 

Santiam and Santiam River model scenarios h17 (slider1340 structures, base operations, and hot/dry conditions) and h1

(existing structures and base operations). Positive numbers indicate warming in the h17 scenario relative to the h1 scenario; 

a white color indicates an absolute change of less than 0.2°C. (B) Comparison of the max temperature target and simulated 

outflow temperatures at Detroit Dam from scenarios h17 (labeled “slider1340”) and h1 (labeled “base”).
Downstream Effects of Selected Scenarios 43

tac12-0772_fig33

12−27

12−01

11−01

10−01

09−01

08−01

07−01

06−01

05−01

River mile

Calendar month−day

0 5 15 25 35 45 55 Rock Creek Little North Santiam River South Santiam River

Temperature at DET,

in degrees Celsius

Temperature at DET,

in degrees Fahrenheit

−3 −2.5 −2 −1.5 −1 −0.5 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6

Temperature difference, in degrees Celsius

−0.2 0.2

−5.4 −3.6 −1.8 0.9 1.8 2.7 3.6 4.5 5.4 6.3 7.2 8.1 9 9.9 10.8

Temperature difference, in degrees Fahrenheit

−0.4 0.4

0

0

EXPLANATION

slider1340−float 400f

base

Temperature target

4 6 8 1210 16

39.2 42.8 46.4 50.0 53.6 60.857.2 64.4

14 18

A. B.

Figure 33. (A) Difference between the 7-day moving average of the daily maximum water temperature from the North Santiam 

and Santiam River model scenarios h19 (slider1340-float structures, 400f operations, and hot/dry conditions) and h1 (existing

structures and base operations). Positive numbers indicate warming in the h19 scenario relative to the h1 scenario; a white 

color indicates an absolute change of less than 0.2°C. (B) Comparison of the max temperature target and simulated outflow 

temperatures at Detroit Dam from scenarios h19 (labeled “slider1340-float _400f”) and h1 (labeled “base”).
44 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

Implications for Dam Operation and 

Planning

The Detroit Dam model results from this study show 

the range of release temperatures that might occur under 

varying hydrologic and meteorological conditions as well as 

under several operational and structural scenarios. A common 

theme among all model results is that spring and summer 

dam operations have an effect on operational flexibility and 

the extent to which release temperatures can be controlled 

later in autumn. Model results indicate that as early in the 

year as April, solar radiation heats the surface of the lake and 

thermal stratification begins. Because most of the lake vertical 

profile is still relatively cool at that time, the ability to meet 

downstream temperature targets during spring is dependent 

on the ability to access and release warmer water near the 

lake surface. This can be difficult when the lake surface is 

either well below or well above the spillway crest in spring 

and early summer. As the surface of the lake becomes warmer 

throughout summer and the thermocline moves deeper in 

the lake, access to cool water below the thermocline begins 

to decrease from about June until about mid-November, at 

which point the lake has been drawn down to make room 

for potential flood storage and typically is isothermal. In 

general, the release of warm surface water from the lake 

during summer allows the cooler water deeper in the lake to be 

reserved until autumn when that cold water is needed most to 

meet downstream temperature targets. 

The ability to mix and release (warm) lake surface 

water with (cold) deeper water throughout the year often is 

the limiting factor in controlling release temperatures from 

Detroit Lake or other deep reservoirs with similar outlet 

configurations. The existing outlets at Detroit Dam do not 

allow near-surface waters to be released during times when the 

lake elevation is below the spillway crest (spring and autumn). 

During years in which the reservoir may be late to fill or not 

fill at all (as in hot/dry and base model scenarios), the spillway 

may only be a viable release point for a limited time in 

summer. Immediately after the lake is drawn down below the 

spillway crest elevation, dam operations with existing outlets 

must release cool water from below the thermocline using 

either the power penstocks or the upper ROs. Later in the 

year, the cool water supply below the thermocline can become 

exhausted at the elevation of the available outlets, and an 

uncontrollable rise in release temperatures results from about 

October through November. Thus, the existing structures 

allow the managers and operators of Detroit Dam to blend 

releases from multiple outlets for only part of the year, with 

less flexibility in drier years.

Power production requirements limit the use of existing 

structures at Detroit Dam to expel warmer water in summer 

(June–September) and cooler water in autumn (October–

November). Operational scenarios with no minimum outflow 

requirements to the power penstocks (noppmin) led to 

outflow temperatures from Detroit Dam that were closer to 

meeting downstream temperature targets than operations with 

dedicated minimum flows for power production.

Model simulations indicate that by delaying the 

drawdown of Detroit Lake in autumn, better control over 

release temperatures is possible immediately downstream of 

Big Cliff Dam. Delaying the drawdown of the lake for better 

downstream temperature management must be balanced 

against the need to make room in the reservoir to manage 

storm-related November inflows that might lead to floods. The 

temperature benefits of delaying lake drawdown result mainly 

from an extended use of the Detroit Dam spillway until as 

late as November 1 (see delay_dd1 and delay_dd2 scenarios 

in figs. 14 and 17). By delaying the date at which drawdown 

begins, warm epilimnetic water can continue to be released in 

conjunction with cool water from the hypolimnion, thereby 

rationing the deeper cool-water supply throughout autumn. 

As a result of this sustained use of the spillway under these 

operational scenarios (figs. 15, 16, 18, and 19), the abrupt 

change in release temperature caused by the loss of spillway 

usage is not as apparent as with base operational scenarios 

(fig. 8). Such abrupt changes in release temperatures may or 

may not be a consideration for downstream salmon habitat 

during late summer and autumn. Farther downstream of Big 

Cliff Dam, however, the North Santiam River model results 

show that decreased releases during September 1–October 15 

necessary to keep lake levels high in scenario h8 (see 

delay_dd2 operations in table 4) cause substantial downstream 

warming (2–5°C).

Aside from operationally delaying the drawdown of 

Detroit Lake, a number of simulated structural scenarios 

showed that the addition of hypothetical floating outlets at 

Detroit Dam could provide access to warm surface water to be 

released spring through autumn, allowing better management 

of release temperatures throughout the season. Adding a 

floating outlet generally leads to greater control of the outflow 

temperature compared with existing outlets at Detroit Dam, 

even under hot/dry conditions. Combining the upper ROs with 

a floating outlet (uro-float) resulted in greater temperature 

control in autumn than the combination of the power 

penstocks and a floating outlet (pp-float) (compare figs. 23

and 24 or fig. 22 with 25). As the elevation of the lower outlet 

was decreased (going from the power penstock elevation to 

the upper RO elevation), the amount of outflow temperature 

control at Detroit Dam increased. As decreased minimum 

flow requirements were placed on the lower, fixed-elevation 

outlets in these scenarios (that is, an increase in the allowable 

“percent spill”), the resulting outflows generally were cooler 

in autumn. Likewise, warmer outflows during June and July 

were possible under these scenarios and may have contributed 

to the relatively large supply of accessible cool water in the 

lake later in autumn. 
References Cited 45

When a hypothetical sliding outlet was used alone 

(slider1340), outflow temperatures roughly met the max

temperature target at Detroit Dam (fig. 20), yet this scenario 

resulted in more day-to-day temperature variation than 

equivalent scenarios incorporating both a floating and lower 

(fixed-elevation or sliding-gate) outlet. This illustrates the 

value provided by having two outlets to access warm and 

cold water separately throughout the year. As the thermocline 

moves up and down in the water column during the day due 

to seiching, a more variable release temperature results from 

a single sliding-gate outlet (slider1340) than from a blended 

combination of one floating outlet withdrawing warmer 

surface water and one fixed-elevation outlet withdrawing 

cooler water (slider1340-float). 

The estimated emergence date of spring Chinook salmon 

was tabulated as a way of comparing the relative success of 

the model scenarios in this study. Success, as measured in this 

study, is a delay in the estimated spring Chinook emergence 

date, as early emergence can be problematic (U.S. Army 

Corps of Engineers, 2012). The comparison showed that 

many structural scenarios and scenarios in which no minimum 

flow was directed to the power penstocks generally led to 

later emergence dates. Under hot/dry environmental forcing 

conditions, structural scenarios generally exhibited later 

emergence dates than scenarios incorporating only operational 

changes to Detroit Dam, perhaps in large part because of 

the limited use of the spillway under hot/dry conditions in 

non-structural scenarios. Downstream in the North Santiam 

River, estimated emergence dates also were influenced by cool 

inflows from large tributaries such as the Little North Santiam 

River, which delayed the emergence date significantly. The 

emergence date is not the only factor involved in assessing 

the biological success of an operational or structural scenario, 

however, as with other streamflow and habitat considerations, 

may be important. 

Results from the Detroit Lake model show that the 

ability to control release temperatures and meet downstream 

temperature targets throughout the year can be more closely 

attained at the site of the dam by delaying drawdown of the 

lake in autumn, decreasing the minimum power-generation 

requirement during summer/autumn, and (or) installing a 

well-conceived combination of floating and (or) sliding-gate 

outlets. 

Results from the North Santiam and Santiam River model 

downstream of Big Cliff Dam show that release temperatures 

from Detroit and Big Cliff Dams have an important and 

measurable effect in the North Santiam River, especially in 

autumn as days become shorter and solar radiation imposes 

less heating to the river. The river modeling illustrated 

the importance of both flow rate and water temperature 

downstream of Big Cliff Dam during autumn to benefit spring 

Chinook salmon spawning. The temperature effects of altered 

releases at Detroit Dam tend to diminish with downstream 

distance, but the effects are large enough to be measurable 

throughout the North Santiam and Santiam River systems. The 

temperatures and seasonal temperature pattern downstream 

of Detroit Dam in the North Santiam River system can be 

managed and controlled through a variety of changes in dam 

operations or outlet options at the upstream dams. 

Acknowledgments

This study was made possible with primary funding from 

the U.S. Army Corps of Engineers, Portland District. Kathryn 

Tackley, James Britton, Mary Karen Scullion, Ian Chane, and 

Cindy Bowline (USACE) provided data, helpful discussions, 

and strategic details and direction on potential options for dam 

operations and structural possibilities. Steven Sobieszczyk 

(USGS) assisted with geographic information system (GIS) 

work.

References Cited

Buccola, N.L., and Rounds, S.A., 2011, Simulating potential 

structural and operational changes for Detroit Dam on 

the North Santiam River, Oregon—Interim results: U.S. 

Geological Survey Open-File Report 2011–1268, 32 p. 

(Also available at http://pubs.usgs.gov/of/2011/1268/.)

Caissie, D., 2006, The thermal regime of rivers—A review: 

Freshwater Biology, v. 51, p. 1389–1406.

Cole, T.M., and Wells, S.A., 2002, CE-QUAL-W2—A twodimensional, laterally averaged, hydrodynamic and waterquality model, version 3.1: U.S. Army Corps of Engineers, 

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

Cole, T.M., and Wells, S.A., 2008, CE-QUAL-W2—A twodimensional, laterally averaged, hydrodynamic and waterquality model, version 3.6: U.S. Army Corps of Engineers, 

Instruction Report EL-08-1 [variously paged].

Moore, A.M., 1964, Compilation of water-temperature data for 

Oregon streams: U.S. Geological Survey Open-File Report 

64-115, 134 p., 1 pl. (Also available at http://pubs.er.usgs.

gov/usgspubs/ofr/ofr64115.)
46 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

Moore, A.M., 1967, Correlation and analysis of watertemperature data for Oregon streams: U.S. Geological 

Survey Water-Supply Paper 1819-K, 53 p., 1 pl. (Also 

available at http://pubs.er.usgs.gov/usgspubs/wsp/

wsp1819K.)

Nash, J.E., and Sutcliffe, J.V., 1970, River flow forecasting 

through conceptual models part I—A discussion of 

principles: Journal of Hydrology, v. 10, no. 3, p. 282–290.

National Marine Fisheries Service, 2008, Willamette Basin 

Biological Opinion—Endangered Species Act Section 

7(a)(2) Consultation: National Oceanic and Atmospheric 

Administration Fisheries Log Number F/NWR/2000/02117 

[variously paged], accessed October 20, 2009, at http://

www.nwr.noaa.gov/Salmon-Hydropower/Willamette-Basin/

Willamette-BO.cfm. 

Oregon Department of Environmental Quality, 2006, 

Willamette Basin Total Maximum Daily Load program 

documents: Oregon Department of Environmental Quality, 

accessed March 27, 2007, at http://www.deq.state.or.us/wq/

TMDLs/willamette.htm.

Oregon Department of Environmental Quality, 2009, Water 

quality standards—Beneficial uses, policies, and criteria for 

Oregon—Temperature: Oregon Administrative Rule 340-

041-0028: Oregon Department of Environmental Quality, 

accessed November 13, 2009, at http://arcweb.sos.state.

or.us/pages/rules/oars_300/oar_340/340_tofc.html#041.

Rounds, S.A., 2010, Thermal effects of dams in the Willamette 

River Basin, Oregon: U.S. Geological Survey Scientific 

Investigations Report 2010–5153, 64 p. (Also available at 

http://pubs.usgs.gov/sir/2010/5153/.)

Rounds, S.A., and Sullivan, A.B., 2006, Development and 

use of new routines in CE-QUAL-W2 to blend water from 

multiple reservoir outlets to meet downstream temperature 

targets, in Proceedings of the Third Federal Interagency 

Hydrologic Modeling Conference, April 2–6, 2006, Reno, 

Nev.: Subcommittee on Hydrology of the Interagency 

Advisory Committee on Water Information, ISBN 

0-9779007-0-3, 8 p., accessed September 11, 2012, at http://

or.water.usgs.gov/tualatin/fihmc3_w2_modifications.pdf.

Sullivan, A.B., and Rounds, S.A., 2004, Modeling streamflow 

and water temperature in the North Santiam and Santiam 

Rivers, Oregon: U.S. Geological Survey Scientific 

Investigations Report 2004–5001, 35 p. (Also available at 

http://pubs.usgs.gov/sir/2004/5001/.)

Sullivan, A.B., and Rounds, S.A., 2006, Modeling waterquality effects of structural and operational changes to 

Scoggins Dam and Henry Hagg Lake, Oregon: U.S. 

Geological Survey Scientific Investigations Report 

2006–5060, 36 p. (Also available at http://pubs.er.usgs.gov/

publication/sir20065060.)

Sullivan, A.B., Rounds, S.A., Sobieszczyk, S., and Bragg, 

H.M., 2007, Modeling hydrodynamics, water temperature, 

and suspended sediment in Detroit Lake, Oregon: U.S. 

Geological Survey Scientific Investigations Report 

2007–5008, 40 p. (Also available at http://pubs.er.usgs.gov/

publication/sir20075008.)

U.S. Army Corps of Engineers, 2012, Willamette Basin 

Annual Water Quality Report for 2011: U.S. Army Corps of 

Engineers Final Report, April 2012, 123 p.
Appendix A 47

Abstract

A hydrodynamic and water temperature model was 

developed for Big Cliff Reservoir on the North Santiam 

River in western Oregon for calendar years 2002 and 2003. 

This model allows the connection of an existing model of 

Detroit Lake upstream to an existing model of the North 

Santiam River downstream. The Big Cliff Reservoir model 

was able to reproduce the daily as well as hourly fluctuations 

in water surface elevation well. Initial runs showed that the 

magnitude and seasonal patterns in modeled water temperature 

released from Big Cliff Dam matched measured temperature 

just downstream in the North Santiam River generally well; 

however, model temperatures were 2 to 3°C too warm in 

late October to early November. Sensitivity testing and other 

investigations into this issue led to modifications in the setup 

of the modeled Detroit Lake model releases, which formed the 

upstream boundary of the Big Cliff Reservoir model. These 

changes led to somewhat higher water temperature errors 

within the Detroit Lake model, but improved the measuredto-modeled fit for the Big Cliff release in late October to early 

November in both 2002 and 2003.

Introduction

Big Cliff Reservoir and Big Cliff Dam are part of the 

USACE water management system in the Willamette River 

basin in northwest Oregon (fig. 1). Big Cliff Dam was 

constructed in 1953 along with the larger Detroit Dam, about 

2.8 mi upstream. At a full-pool water surface elevation of 

1,206 ft, Big Cliff Reservoir stores 6,450 acre-ft of water. Big 

Cliff Dam releases water through a power generating facility 

or through radial spillway gates to the North Santiam River.

A primary purpose of Big Cliff Dam is to regulate the 

fluctuating power-generating water releases from Detroit 

Dam so that relatively smooth flows are released to the North 

Santiam River. In the years modeled, the Big Cliff Reservoir 

water surface elevation often fluctuated on a daily or hourly 

basis as much as 24 ft due to the hydropower peaking releases 

from Detroit Dam. Other purposes of Big Cliff Reservoir 

and Dam include flood damage protection, power generation, 

water quality improvement, fish and wildlife habitat, and 

recreation.

Purpose and Scope

The purpose of this work was to develop a model of Big 

Cliff Reservoir that could (1) simulate stage, flow, velocity, 

and water temperature, (2) provide information on processes 

that control water temperature in this reach, and (3) act as 

the connecting model between the existing Detroit Lake 

CE-QUAL-W2 model and the existing North Santiam and 

Santiam River CE-QUAL-W2 model so that model scenarios 

for the entire system could be run and analyzed. Separate 

Big Cliff Reservoir models were developed for calendar 

years 2002 and 2003 and were calibrated for flow and water 

temperature.

Methods and Data

The Big Cliff Reservoir model was constructed using 

version 3.12 of CE-QUAL-W2, a hydrodynamic and water 

quality model from the USACE (Cole and Wells, 2002). 

CE-QUAL-W2 is two-dimensional, simulating vertical and 

longitudinal variation from upstream to downstream; it is 

laterally averaged across the channel. For a long, narrow, 

pooled reach such as Big Cliff Reservoir, a two-dimensional 

laterally averaged model is a good choice. CE-QUAL-W2 can 

simulate streamflow, water velocity, water temperature, and a 

number of water quality constituents, including total dissolved 

solids, nutrients, algae, oxygen, and suspended sediment. 

CE-QUAL-W2 also was used to build the upstream Detroit 

Lake model (Sullivan and others, 2007) and the downstream 

North Santiam River model (Sullivan and Rounds, 2004) as 

well as models of other rivers and reservoirs in the Willamette 

River basin.

The CE-QUAL-W2 model code was modified by USGS 

project personnel to (1) fix coding errors, (2) add new model 

flux outputs, (3) add a new subroutine to automatically blend 

outflows from multiple reservoir outlets to match a usersupplied downstream temperature target, and (4) update the 

selective withdrawal algorithms. The blending routines were 

documented previously by Sullivan and Rounds (2006); 

further updates are documented in appendix C.

The Big Cliff Reservoir model was constructed in several 

steps. Initially, a model grid was built. Then, model input 

data were collected, processed, and formatted to provide 

flow, water temperature, meteorological, and shade boundary 

conditions. Finally, the model was calibrated by comparing 

model output to measured water surface elevation and water 

temperature data.

Appendix A. Big Cliff Reservoir Model Development—

Construction and Calibration
48 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

Model Grid

A CE-QUAL-W2 model grid is composed of model 

segments that connect together in the direction of flow. Each 

individual segment has layers with defined height that increase 

in width from the channel bottom upwards, resembling a cross 

section in shape. Only limited bathymetric data were available 

to construct the Big Cliff model grid. As a first step, a predam topographic map from USACE of the Big Cliff reach 

with only few contour lines was digitized into a geographic 

information system (GIS). Model segment boundaries were 

designated in this GIS coverage. Then, 10 equally spaced 

cross sections were sampled within each segment using GIS 

techniques; the ten subsections were averaged to obtain a 

representative cross section shape for each model segment. 

Layer widths were adjusted until the volume-elevation 

curve matched the volume-elevation curve from the USACE 

Big Cliff Reservoir storage table (USACE table dated 

November 15, 2002) (fig. A1). After checking that none of 

the layer widths were less than 5 m, as recommended by the 

CE-QUAL-W2 development team (Cole and Wells, 2008), the 

segment cross sections were formatted into a CE-QUAL-W2 

bathymetry input file. The Big Cliff CE-QUAL-W2 model 

grid consisted of 15 model segments. Segment length ranged 

from 281.2 to 307.0 m, with an average length of 297.3 m. 

Layer height throughout the bathymetry grid was 1.0 m.

Model Data

Because the Detroit Lake and Big Cliff Reservoir models 

are adjacent, some CE-QUAL-W2 inputs from the Detroit 

Lake model could be used for the Big Cliff Reservoir model. 

Shared inputs included the meteorological conditions input 

file, the precipitation input file, the precipitation temperature 

input file, and many control file parameters. Data for other 

input files and calibration had to be obtained specifically 

for the Big Cliff model. Although the Detroit Lake model 

simulated total dissolved solids and suspended sediment, those 

constituents were not included in the Big Cliff model because 

the North Santiam River model does not simulate those 

constituents.

Hydrologic Data

The main inflow to the Big Cliff Reservoir model was 

the outflow from the Detroit Lake model. These releases often 

fluctuated greatly on an hourly basis, from zero to hundreds 

or thousands of cubic feet per second. Flows from Detroit 

Dam were released in this manner to respond to hydropower 

demands. During high flow events, flows were released from 

Detroit Dam in a more continuous fashion. 

Other inflows to Big Cliff Reservoir included tributary 

flows from Sardine Creek and Lawhead Creek. Because 

neither of those inflows were gaged, the inflows were 

estimated by multiplying the ratio of each creek’s watershed 

(drainage) area to the watershed area of Blowout Creek by 

the gaged flow of Blowout Creek. Blowout Creek is a gaged 

tributary on the south side of Detroit Lake that has a long 

record of data. Sardine Creek drains 5.5 mi2 and Lawhead 

Creek drains 4.6 mi2 of watershed area.

Water releases from Big Cliff Dam were routed through 

the power penstocks or over the spillway. Data on hourly 

flow through these two outlets were obtained from USACE. 

The power penstocks’ intake centerline elevation is 1,140 

ft (347.5 m), and the spillway crest is located at 1,161.5 ft 

(354.0 m). These water release elevations were set in the 

model control file.

The measured water surface elevation of Big Cliff 

Reservoir was used to close the water balance during model 

calibration and set the inflows from other ungaged tributaries 

and groundwater as a distributed tributary input to the model. 

Hourly values of the Big Cliff Reservoir forebay water surface 

elevation were obtained from USACE. In 2002–03, the water 

surface elevation in Big Cliff Reservoir fluctuated between 

1,181.0 and 1,205.9 ft.

1,100

1,120

1,140

1,160

1,180

1,200

1,220

0 1,000 2,000 3,000 4,000 5,000 6,000

Elevation, in meters above sea level

Reservoir volume, in million cubic meters

USACE

EXPLANATION

Model

Figure A1. Volume-elevation curves for Big Cliff 

Reservoir, Oregon, from the U.S. Army Corps of Engineers 

(USACE) and as represented by the model grid (Model).
Appendix A 49

Water Temperature Data

The water temperature for the inflow from Detroit Lake 

came from Detroit Lake model output. Water temperatures of 

Sardine Creek and Lawhead Creek were not measured, but 

they were estimated to be similar to that of French Creek, a 

tributary in the Detroit Lake drainage.

Water temperature data with which to compare modeled 

water temperature during calibration was limited. For instance, 

during the years modeled, no in-reservoir temperature profiles 

had been collected. Measured water temperature data were 

available for the North Santiam River at Niagara, about 0.7 mi 

downstream of Big Cliff Dam. In addition, some intermittent 

measured temperature data were available from the base of 

Detroit Dam from the Oregon Department of Environmental 

Quality LASAR database.

Some water temperature data in Big Cliff Reservoir for 

more recent years (parts of 2008 and 2009) were provided 

by USACE. Although these data were not used directly to 

calibrate the 2002 and 2003 Big Cliff Reservoir models, the 

data were useful for helping to understand the general trend in 

water temperature as water moved from Detroit Dam through 

Big Cliff Reservoir and farther downstream.

Shade

Because Big Cliff Reservoir is located in a canyon, the 

effect of topographic shading was important and included 

in the model simulations. Eighteen topographic inclination 

angles, every 20 degrees, from the water surface of each 

model segment to the nearby ridgetops, were calculated using 

GIS techniques. These angles then were formatted into a 

CE-QUAL-W2 shade file to describe the shading provided 

by topographic features. Shading provided by any riparian 

vegetation was assumed to be negligible.

Model Development/Calibration

During the process of model calibration, measured data 

are compared to model outputs. Parameters and other factors 

can be modified within reasonable bounds to optimize the 

comparison between model outputs and measured data for this 

specific reach. For the Big Cliff Reservoir model calibration, 

the water balance was completed first. Then, the model was 

calibrated for water temperature.

Water Balance

Results from initial model runs that included inflows, 

outflows, precipitation, and evaporation showed differences 

between modeled and measured water surface elevations 

in Big Cliff Reservoir. This indicated that some additional 

inflows or outflows were needed to close the water balance. 

Typically, missing flows in a CE-QUAL-W2 model occur due 

to the presence of small ungaged tributaries, overland flows, 

groundwater sources or sinks, or error in the measurement of 

the included inflows and outflows.

For the Big Cliff model, a distributed tributary was used 

to describe and include these missing flows; this is a common 

way to close the water balance in CE-QUAL-W2 (Cole and 

Wells, 2002). In brief, the distributed tributary flow was 

calculated by subtracting the sum of inflows from the sum of 

outflows on an hourly basis, applying a moving daily average 

to that time series, running the model with that distributed 

tributary file, and making minor adjustments to the distributed 

tributary inputs until the measured and modeled water surface 

elevations matched reasonably well. The flow associated with 

the distributed tributary was small relative to total inflows and 

outflows, accounting for only 1 and 4 percent of total inflows 

and 1 and 0 percent of total outflows in 2002 and 2003, 

respectively. The flows that make up the distributed tributary 

flows are likely sourced mostly from surface water because 

the flow imbalance was greatest during storm events. The final 

modeled water surface elevations were in good agreement 

with the measured values for both 2002 and 2003 (fig. A2). 

The water-surface elevations in that figure show a large 

amount of daily variation, which is typical of how Big Cliff 

Reservoir is used to moderate (reregulate) the greatly varying 

releases from Detroit Dam.

Water Temperature

Initial Testing of Big Cliff Reservoir Model

After the water balance was complete, the modeled water 

temperature of the Big Cliff Dam release was compared to 

measured water temperature 0.7 mi downstream at the USGS 

gaging station at Niagara on the North Santiam River. Travel 

time is short between these locations and although the water 

temperatures would not be expected to match exactly, they 

were likely to be close. In this first comparison, the seasonal 

pattern of water temperature from the modeled Big Cliff 

release matched the seasonal pattern in the measured data at 

Niagara for most of the year. However, the annual maximum 

modeled temperature for the period from late October to early 

November was as much as 2 or 3°C warmer than the measured 

temperature.
50 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

tac12-0772_figA02

Modeled

EXPLANATION

Measured

1,180

1,185

1,190

1,195

1,200

1,205

1,210

15 16 17 18 19 20 21 22 23 

Water surface elevation, in feet

July 2002

1,180

1,185

1,190

1,195

1,200

1,205

1,210

Water surface elevation, in feet

1,180

1,185

1,190

1,195

1,200

1,205

1,210

Water surface elevation, in feet

1,180

1,185

1,190

1,195

1,200

1,205

1,210

Water surface elevation, in feet

A.

B.

C.

D.

January March May July September November January

January March May July September November January

15 16 17 18 19 20 21 22 23

July 2003

Figure A2. Modeled and measured Big Cliff Reservoir water surface elevations for the entire calendar years of 

2002 and 2003. A closer look at 9 days in July shows the nature of the daily variation in water surface elevation. 
Appendix A 51

To test whether model calibration factors within the 

Big Cliff model could be adjusted to provide a better water 

temperature match in late October and early November, 

a series of sensitivity tests were run. The sensitivity tests 

modified one factor at a time and examined the effect on Big 

Cliff outflow water temperatures. Factors examined in this 

analysis included friction factors, the coefficient of bottom 

heat exchange, the surface heat exchange calculation method, 

the vertical turbulence closure algorithm, and the elevation of 

the outflows at Big Cliff Dam. Version 3.6 of CE-QUAL-W2 

(Cole and Wells, 2008) also was tested. None of these tests 

could explain the late October to early November temperature 

difference and most produced less than a 0.3°C change in the 

Big Cliff Dam outflow water temperature. The insensitivity of 

Big Cliff release temperatures to Big Cliff model parameters 

was likely due to the short model reach and brief residence 

time of water within Big Cliff Reservoir.

Detroit Lake Model Tests and Adjustments

Because Big Cliff Reservoir model parameters could 

not explain the 2–3°C discrepancy in late October and early 

November, the next step was to look farther upstream at 

the Detroit Lake model and its outflow water temperature. 

Testing of the Detroit Lake model first took the form of 

sensitivity testing for parameters that affected temperature 

both within Detroit Lake and for the Detroit Lake outflow. 

Through this testing, it was determined that the modeled 

in-lake water temperature and associated water temperature 

parameters were constrained by calibration to the in-lake data; 

therefore, the main variable that could be adjusted was the 

setup of the Detroit Dam outlet structures and the interaction 

of the withdrawal outlets with the CE-QUAL-W2 selective 

withdrawal algorithm.

To address this, several updates and adjustments were 

made to the CE-QUAL-W2 code for the Detroit Lake model. 

First, the DOWNSTREAM_WITHDRAWAL and 

LATERAL_WITHDRAWAL subroutines in the 

USGS‐modified version 3.12 model were modified to make 

the velocity profile equations similar to those in 

CE-QUAL-W2 version 3.6. Secondly, the LATERAL_

WITHDRAWAL subroutine was modified to allow both 

point and line withdrawals, using equations from the 

DOWNSTREAM_WITHDRAWAL subroutine. A point 

withdrawal is an outlet structure that is narrow in relation to 

the dam width, whereas a line withdrawal is wide in relation 

to dam width (>1/10). In the previous version of the Detroit 

Lake model code, the default was to specify point withdrawal 

outlets at Detroit Dam, which has no associated width 

specification. A line withdrawal, on the other hand, requires 

an associated outlet width to be specified, and varying the 

width of the outlet line affects which lake depths (or model 

layers) from which the resulting outflow are drawn. If the 

lake is well-mixed with similar temperatures from surface to 

bottom, the outlet line width has little effect on outflow water 

temperature; however, if the lake is stratified with variable 

water temperature with depth, then this parameter does affect 

the outflow water temperature.

More specifically, the equations for point and line 

withdrawals are (Cole and Wells, 2008):

point:

line:

where

is withdrawal

d

d

d

c Q

N

c q

N

bi

bi

= ( )

= ( )

0 3333

2 0 5

.

.

zone half height, m;

is total outflow, in m /s;

is inter

Q

N

3

nal buoyance frequency, Hz;

is outflow per unit width, m2

q /s; and

c is boundary interference coefficient. bi

As the outlet line width increases, the model withdraws 

more of its releases from model layers (or reservoir depths) 

close to the elevation of the outlet. As the line width decreases, 

the model withdraws water from a greater range of depths. 

Similarly, greater release rates tend to draw water from more 

model layers, whereas small releases tend to be from layers 

near the outlet elevation. Changing the line width then, 

changes release water temperatures during stratified conditions 

in Detroit Lake. For the Detroit Lake model, the line width 

was used as a calibration parameter to better match the late 

October to early November water temperature downstream 

at Niagara. The final structure widths used for the Detroit 

Lake model were 6.8 m for the power penstocks and 4.0 m 

for the upper ROs; the spillway was not used in 2002–03. 

These are calibration parameters, and the selective withdrawal 

algorithms in the model are not perfect representations of 

mixing near the dam; therefore, these values are not expected 

to have an actual physical meaning.

Changing these outlet parameters for Detroit Dam did 

somewhat affect modeled water temperatures within Detroit 

Lake. A tradeoff was made between water temperature errors 

in Detroit Lake and water temperature errors downstream. 

Goodness-of-fit statistics for the updated Detroit Lake model 

are compared to those of the original model in table A1. 

The mean error (ME) is the sum of the differences between 

modeled and measured temperatures, where they coincide 

in space and time, and is an overall measure of bias; a ME 

close to zero is desirable. The mean absolute error (MAE) 
52 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

is the average of the absolute value of modeled-measured 

differences and represents a typical error for any data point; 

an MAE less than 1.0°C has been noted in previous model 

applications as a reasonable metric denoting a good fit to 

the data (Sullivan and others, 2007). The root mean square 

error (RMSE) is the square root of the average squared error 

between modeled-measured data comparisons and is equal 

to the square of the mean plus the square of the standard 

deviation. If the ME is zero, then the RMSE is equal to the 

standard deviation of the errors—a good measure of the 

magnitude of the typical error of the prediction; RMSE values 

less than 1.0 to 1.5°C have been deemed a good fit in previous 

applications.

Detroit Lake model Year 2002 Year 2003

Original model Updated model Original model Updated model

Mean error -0.02 -0.39 -0.34 -0.55

Mean absolute error 0.52 0.77 0.58 0.77

Root mean square error 0.69 1.00 0.76 0.99

Table A1. Detroit Lake model goodness-of-fit statistics for calendar years 2002 and 2003 

for the original Detroit Lake model (Sullivan and others, 2007) and the updated Detroit Lake 

model used as the upstream boundary for the Big Cliff Reservoir model.

Final Big Cliff Modeled Water Temperature

Changing the outlet setup of the Detroit Lake model 

outlets provided a better match between the Big Cliff Dam 

release temperatures and the measured water temperatures 

at Niagara (fig. A3). Agreement with those measured data 

downstream was good, with a mean absolute error less than 

0.4°C in both 2002 and 2003 (table A2). The construction and 

calibration of the Big Cliff Reservoir model now allows the 

Detroit Lake model to be connected with the existing North 

Santiam River model and other Willamette River basin models 

downstream.

Table A2. Big Cliff model goodness-of-fit 

statistics for calendar years 2002 and 2003 

using the updated Detroit Lake model as the 

upstream boundary condition.

Statistic Year 2002 Year 2003

Mean error -0.05 -0.09

Mean absolute error 0.31 0.39

Root mean square error 0.39 0.48
Appendix A 53

tac12-0772_figA03

0

2

4

6

8

10

12

14

16

January 1 March 1 May 1 July 1 September 1 November 1 January 1 January 1 March 1 May 1 July 1 September 1 November 1 January 1

Water temperature, in degrees Celsius

2002

Niagara, measured

Big Cliff outflow, modeled

A.

EXPLANATION

2003

B. .

Figure A3. Modeled water temperatures released from Big Cliff Dam compared to measured water temperatures in the 

North Santiam River at Niagara, Oregon, 0.7 mile downstream.
54 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

To ensure that the CE-QUAL-W2 models of Detroit 

Lake and Big Cliff Reservoir would accurately represent 

conditions resulting from current dam operations, the models 

were tested using observed conditions from 2011. Since 2007, 

operations at Detroit Dam have expanded to include more 

frequent use of the spillway (elevation 1,541.0 ft; 469.7 m) 

and the upper regulating outlet (RO, elevation 1,339.9 ft; 

408.4 m) to improve downstream temperature management. 

To better match measured temperatures at the USGS Niagara 

gaging station (14181500), the CE-QUAL-W2 model line 

width parameter for the spillway outlet, which was not used 

in the original model calibration for 2002–03, was set to 

25 m through an optimization process. A sensitivity analysis 

of the line width of the upper RO at Detroit Dam also was 

conducted, but resulted in little difference in simulated outflow 

temperatures; therefore, the line width for the ROs was left 

at 4.0 m. The line width used for the power penstocks was 

unchanged and remained at 6.8 m.

Comparisons of modeled and measured vertical 

temperature profiles within Detroit Lake (fig. B1) and Big 

Cliff Reservoir (fig. B2) show that the models capture the 

seasonal patterns in the vertical profiles relatively well, 

with perhaps a slight negative bias for the deepest profiles. 

The Detroit Lake model also does not capture some of the 

daily variation in the mid-depth temperature profile data. 

Modeled daily mean release temperatures from Detroit and 

Big Cliff Dams (fig. B3) show that significant heat exchange 

is occurring in Big Cliff Reservoir in August and September; 

including the Big Cliff Reservoir model, therefore, is useful 

for capturing these heat-exchange processes. The comparison 

of Big Cliff Dam modeled release temperatures to measured 

temperatures downstream at the Niagara gage (fig. B3) shows 

relatively good agreement with an MAE less than 1.0°C, but 

a slight negative bias for August through December. A similar 

comparison between Big Cliff Dam modeled hourly release 

temperatures and measured hourly temperatures at Niagara is 

shown in figure B4.

Goodness-of-fit statistics are noted on the figures in 

this appendix to quantify the overall model performance. 

Definitions of the mean error (ME), mean absolute error 

(MAE), and the root mean square error (RMSE) were noted 

in appendix A. The Nash-Sutcliffe coefficient (NS) is the 

proportion of variance in the measured values that is explained 

by the predicted values, and is a more rigorous fit statistic than 

the coefficient of determination. An NS value of 1.0 represents 

a perfect fit, an NS value of 0 indicates that the model 

predictions are only as accurate as the mean of the measured 

data, and an NS value less than zero means that the measured 

mean is a better predictor than the model (Nash and Sutcliffe, 

1970). In this case, the NS values are all roughly 0.9 or higher, 

indicating that the model captures most of the variance in the 

measured data.

Appendix B. Detroit Lake and Big Cliff Reservoir Model Evaluation for 2011
Appendix B 55

tac12-0772_figB01

32.0

35.6

39.2

42.8

46.4

50.0

53.6

57.2

60.8

64.4

68.0

71.6

0

2

4

6

8

10

12

14

16

18

20

22

0

2

4

6

8

10

12

14

16

18

20

22

Temperature, in degrees Fahrenheit

0

2

4

6

8

10

12

14

16

18

20

22

Temperature, in degrees Celsius

0

2

4

6

8

10

12

14

16

18

20

22

35.6

39.2

42.8

46.4

50.0

53.6

57.2

35.6

39.2

42.8

46.4

50.0

53.6

57.2

2

4

6

8

10

12

14

Jan. Feb. Mar. Apr. May June July Aug. Sept. Jan. Feb. Mar. Apr. May June July Aug. Sept.

Month

2

4

6

8

10

12

14

32.0

35.6

39.2

42.8

46.4

50.0

53.6

57.2

60.8

64.4

68.0

71.6

32.0

35.6

39.2

42.8

46.4

50.0

53.6

57.2

60.8

64.4

68.0

71.6

32.0

35.6

39.2

42.8

46.4

50.0

53.6

57.2

60.8

64.4

68.0

71.6

Measured

Modeled

A.

Depth=0.15 meter

G.

Depth=3 meters

B.

Depth=6.1 meters

H.

Depth=9.1 meters

C.

Depth=12 meters

I.

Depth=15 meters

D.

Depth=24 meters

J.

Depth=30 meters

E.

Depth=37 meters

K.

Depth=43 meters

F.

Depth=49 meters

L.

Depth=55 meters

0.95

NS

-0.31

ME

0.68

MAE

EXPLANATION

Figure B1. Measured and modeled water temperatures in Detroit Lake, Oregon, at discrete depths within the lake 

during 2011. NS is the Nash-Sutcliffe coefficient, ME is the mean error, and MAE is the mean absolute error between 

the measured and modeled water temperature.
56 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

tac12-0772_figB02

32.0

35.6

39.2

42.8

46.4

50.0

53.6

57.2

60.8

64.4

68.0

71.6

32.0

35.6

39.2

42.8

46.4

50.0

53.6

57.2

60.8

64.4

68.0

71.6

32.0

35.6

39.2

42.8

46.4

50.0

53.6

57.2

60.8

64.4

68.0

71.6

0

2

4

6

8

10

12

14

16

18

20

22

0

2

4

6

8

10

12

14

16

18

20

22

May June July Aug. Sept. Oct. May June July Aug. Sept. Oct.

Month

0

2

4

6

8

10

12

14

16

18

20

22

Temperature, in degrees Fahrenheit

Temperature, in degrees Celsius

Measured

Modeled

A.

Depth=0.3 meter

D.

Depth=3 meters

B.

Depth=6.1 meters

E.

Depth=9.1 meters

C.

Depth=12 meters

F.

Depth=15 meters

EXPLANATION

0.88

NS

−0.54

ME

0.81

MAE

Nov. Nov.

Figure B2. Measured and modeled water temperatures in Big Cliff Reservoir, Oregon, at discrete depths within 

the lake during 2011. NS is the Nash-Sutcliffe coefficient, ME is the mean error, and MAE is the mean absolute error 

between the measured and modeled water temperature.
Appendix B 57

tac12-0772_figB03

Big Cliff pool limit

Big Cliff pool limit

EXPLANATION

Outflow, in cubic feet per second

100

200

500

1,000

2,000

5,000

10,000

20,000

Elevation, in feet

1,165

1,170

1,175

1,180

1,185

1,190

1,195

1,200

1,205

1,210

Error between Niagra and BCL model

NS

0.96

ME

-0.87

MAE

0.94

38

40

42

44

46

48

50

52

54

56

58

60

62

64

3.3

4.4

5.6

6.7

7.8

8.9

10.0

11.1

12.2

13.3

14.4

15.6

16.7

Temperature, in degrees Celsius 

Temperature, in degrees Fahrenheit 

EXPLANATION

2011

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/12

11/1911/2612/0312/1012/1712/2412/31

Temperature target

Niagra

Detroit

Big Cliff

Power det.out

Spill det.out

U.RO det.out

Bcl.out

A.

B.

C.

Figure B3. Simulated daily mean water temperatures from Detroit Dam release, Big Cliff Dam release, and measured 

daily mean temperatures from USGS gaging station 14181500 (North Santiam River at Niagara, Oregon), during 2011. 

NS is the Nash-Sutcliffe coefficient, ME is the mean error, and MAE is the mean absolute error between the measured 

and modeled water temperature.
58 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

tac12-0772_figB04

38

40

42

44

46

48

50

52

54

3.3

4.4

5.6

6.7

7.8

8.9

10.0

11.1

12.2

Temperature, in degrees Fahrenheit 44

46

48

50

52

54

56

58

60

6.7

7.8

8.9

10.0

11.1

12.2

13.3

14.4

15.6

Temperature, in degrees Celsius

09−0709−0909−1109−1309−1509−1709−1909−2109−2309−2509−2709−2910−0110−0310−0510−0710−0910−1110−1310−1510−1710−1910−2110−2310−2510−2710−2910−3111−0211−0411−0611−0811−1011−1211−1411−1611−1811−2011−2211−2411−2611−2811−3012−0212−0412−06

42

44

46

48

50

52

54

56

58

60

5.6

6.7

7.8

8.9

10.0

11.1

12.2

13.3

14.4

15.6

62 16.7

62 16.7 04−10 04−12 04−14 04−16 04−18 04−20 04−22 04−24 04−26 04−28 04−30 05−02 05−04 05−06 05−08 05−10 05−12 05−14 05−16 05−18 05−20 05−22 05−24 05−26 05−28 05−30 06−01 06−03 06−05 06−07 06−09 06−11 06−13 06−15 06−17 06−19 06−21 06−23 06−25 06−27 06−29 06−29 07−01 07−03 07−05 07−07 07−09 07−11 07−13 07−15 07−17 07−19 07−21 07−23 07−25 07−27 07−29 07−31 08−02 08−04 08−06 08−08 08−10 08−12 08−14 08−16 08−18 08−20 08−22 08−24 08−26 08−28 08−30 09−01 09−03 09−05 09−07

Niagra

Big Cliff model

Overall error between Niagra and Big Cliff model

0.95

NS

-0.60

ME

1.05

MAE

EXPLANATION

2011

A.

B.

C.

Figure B4. Simulated hourly water temperatures from modeled Big Cliff Dam, Oregon, releases during 2011, 

compared to measured hourly temperatures from USGS gaging station 14181500 (North Santiam River at Niagara).
Appendix C 59

Appendix C. Code Modifications

Several modifications were made to the version 3.12 

CE-QUAL-W2 model code beyond those already documented 

by Sullivan and others (2007) and Sullivan and Rounds 

(2006). The original Detroit Lake version 3.12 model 

published by Sullivan and others (2007) included a USGScoded blending subroutine that allowed the model to select 

two outlets from among several potential outlets and set the 

percentage of the total release rate in each outlet in order to 

meet a user-supplied downstream temperature target time 

series. In this study, several additional modifications were 

made to the model code:

• The DOWNSTREAM_WITHDRAWAL and 

LATERAL_WITHDRAWAL subroutines were updated 

to make the velocity profile equations similar to those 

used in CE-QUAL-W2 version 3.6. The LATERAL_

WITHDRAWAL subroutine also was modified to 

allow both “point” and “line” withdrawals, using 

equations from the DOWNSTREAM_WITHDRAWAL 

subroutine.

• The blending subroutine was modified to iteratively set 

the outlet release rates when two outlets are used; up to 

five iterations are performed. In the original blending 

subroutine, the temperature released from each outlet 

was estimated as the temperature in the reservoir at 

the elevation of the outlet, but that estimate did not 

always match well with the actual temperature released 

through the outlet because water from many layers 

is drawn into the outlet as specified by the model’s 

selective withdrawal algorithm. Because the amount 

of water that comes from various layers depends on 

the release rate for that outlet, this procedure had to be 

iterative in order to be accurate.

In this iterative process, an initial estimate of the 

release rates is made and then refined in a loop. 

The loop is exited early if the current and previous 

release rates for each outlet are within 1 percent. If 

all five iterations are performed and the current and 

previous results are still not within 1 percent, then a 

message is written to the model warning file. This code 

modification greatly improved the accuracy of the 

blending subroutine.

• Two new inputs were added to the model control file 

to allow withdrawals (in addition to structures) to have 

the characteristics of a line sink or a point sink and to 

specify the width of the line sink. The WD SINK card 

is located in the control file just after the WD TYPE 

card; accepted inputs are either LINE or POINT. The 

WD WIDTH card follows, to include the width of any 

line sinks that are specified for withdrawals.

• For floating outlets, the original blending algorithm 

assumed that all floating outlets, and all sliding-gate 

outlets that were located at their upper limit near the 

water surface, were positioned at a depth of 1.5 m 

below the water surface. The introduction of a new 

withdrawal depth variable allows the user to set the 

depth of each floating or sliding-gate outlet relative 

to the water surface. This new WD FLOAT card is 

located just after the WD WIDTH card in the control 

file.

• A new input variable (MINFRAC) was added for 

use with the blending subroutine to allow the user to 

specify a minimum outlet flow rate or a minimum 

fraction of the total release rate for a particular group 

of withdrawals. This input variable does not affect the 

choice of outlets. If a user specifies more than three 

withdrawals in any one withdrawal group, this factor 

is not used to determine which two of the available 

withdrawals are selected for blending the releases 

and, therefore, this constraint will not necessarily be 

honored.

When not active, this new MINFRAC variable is set 

to 0.0. When used to set a minimum fraction of the 

total withdrawal, it is set to a positive value less than 

or equal to 1.0. To set a minimum flow rate in cubic 

meters per second, the MINFRAC input is set by the 

user to a negative number where the minimum flow 

rate is equal to the absolute value of MINFRAC. The 

negative sign is used to tell the model that this is a 

minimum flow rate rather than a minimum fraction of 

the total flow. The model ensures that MINFRAC is 

not larger than 1.0. This new user input is provided on 

a new WD MINFR card that is located just after the 

WD GROUP card in the model control file.

Note that the minimum flow specification should 

work well as long as the withdrawn flows do not 

change between the times that the blending subroutine 

is called. If the withdrawal flow rates change more 

frequently than the subroutine is called, then this 

code does not guarantee that the minimum specified 

flows are met. Often, the blending subroutine may 

only be called once or a few times per day so that 

dam operators do not have to frequently change gate 

positions.

• Lastly, a withdrawal priority setting was added as a 

user-specified input so that if more than one minimum 

flow constraint was specified within a withdrawal 

group, the code can try to honor each constraint 

according to the specified outlet priority. A lower code 
60 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

specifies a higher priority; therefore, a priority input 

of 1 is a higher priority than a priority input of 2. 

Specified minimum flow criteria will not necessarily 

be met if the outlet has a lower priority (higher priority 

number). The priority setting does not affect the choice 

of which two outlets are selected from among a group 

of more than two withdrawals in a group.

After honoring the priority level, the blending 

subroutine makes an attempt to meet any other 

fractional flow or minimum flow criteria. However, if 

a greater total flow or total fractional flow is requested 

relative to what can be provided, a compromise will 

be made and it is possible that neither minimum flow 

constraint will be honored.

In cases when the water column is isothermal and no 

minimum flow criteria are set, the priority setting is 

used to route all of the outflow to the outlet with the 

higher priority (lower priority setting). 

The new inputs to the model control file described in this 

section above might look like the snippet of a control 

file example as reproduced here for a system with three 

withdrawals: 

WD TYPE WDTYPE WDTYPE WDTYPE WDTYPE WDTYPE WDTYPE WDTYPE WDTYPE WDTYPE

FIXED FIXED FIXED

WD SINK WDSINK WDSINK WDSINK WDSINK WDSINK WDSINK WDSINK WDSINK WDSINK

LINE LINE LINE

WD WIDTH WWD WWD WWD WWD WWD WWD WWD WWD WWD

6.8 4.0 25

WD FLOAT WDEPTH WDEPTH WDEPTH WDEPTH WDEPTH WDEPTH WDEPTH WDEPTH WDEPTH

0 0 0

WD GROUP WDGRP WDGRP WDGRP WDGRP WDGRP WDGRP WDGRP WDGRP WDGRP

1 1 2

WD MINFR MINFRAC MINFRAC MINFRAC MINFRAC MINFRAC MINFRAC MINFRAC MINFRAC MINFRAC

0.4 0 0

WD PRIOR WDPRIOR WDPRIOR WDPRIOR WDPRIOR WDPRIOR WDPRIOR WDPRIOR WDPRIOR WDPRIOR

1 2 3

The modified model source code is available online at the project website: http://or.water.usgs.gov/santiam/detroit_lake/ in the 

Downloads section of that page.
Appendix D 61

The original North Santiam and Santiam River model 

was constructed and calibrated for June through October 2001 

and April through October 2002 (Sullivan and Rounds, 2004). 

For application to the conditions of this study, updated flow, 

temperature, and meteorological boundary conditions had to 

be created.

Boundary Inflows

Boundary inflows to the river model include the North 

Santiam River below Big Cliff Dam (RM 58.1), Rock Creek 

(RM 49.3), the Little North Santiam River (RM 39.2), and 

the South Santiam River (RM 11.7). Other waters entering 

the river model include precipitation on the water surface, 

groundwater inflows, and effluent from the Stayton and 

Jefferson wastewater treatment plants located at RMs 27.5 and 

9.0, respectively. 

For the initial simulations representing current conditions 

and for testing purposes, measured hourly streamflow from 

the North Santiam River at Niagara (USGS gaging station 

14181500) was used as the upstream boundary because that 

site is near Big Cliff Dam. For simulations in the study based 

on hypothetical Detroit Dam scenarios, the simulated outflow 

from the upstream Detroit Lake and Big Cliff Reservoir 

models was used as the upstream boundary for the river 

model.

For most of the normal and cool/wet environmental 

scenarios, measured hourly streamflow for the Rock Creek 

near Mill City site (USGS station 14181750) were available 

and were used directly. For the hot/dry scenario, however, 

no measured data were available for that site. In the absence 

of measured data, hourly streamflow for Rock Creek was 

estimated by multiplying the measured hourly streamflow 

from the Little North Santiam River near Mehama (USGS site 

14182500) by a drainage area ratio of 0.17 (ratio of the Rock 

Creek drainage area to the Little North Santiam River drainage 

area). 

Measured hourly streamflow data were available for the 

time periods of all three environmental scenarios for the Little 

North Santiam River (USGS site 14182500). That station 

is located 2 mi upstream from its confluence with the North 

Santiam River.

South Santiam River streamflow data were estimated 

at the river’s confluence with the North Santiam River using 

hourly streamflow measurements at the South Santiam River 

at Waterloo (USGS site 14187500). Measured streamflows at 

Waterloo were multiplied by 1.1 (as a drainage area expansion 

factor) to account for net inflows and withdrawals between the 

Waterloo gage and the North Santiam River confluence.

Measured precipitation data were obtained from the 

National Oceanic and Atmospheric Administration’s National 

Climatic Data Center (NCDC). Daily total precipitation data 

for the upstream two branches of the model, upstream of the 

Little North Santiam River confluence (RM 39.2), were taken 

from a site at Detroit Dam (NCDC station 352292). For the 

downstream three model branches, daily total precipitation 

data were measured at Stayton, Oregon (NCDC station 

358095). 

Groundwater inflow, flow from small ungaged creeks, 

and errors in gaged streamflow data were accounted for by 

using a distributed tributary in the model for each of the six 

branches. For the initial simulation, distributed tributary flow 

files created for 2001–02 by Sullivan and Rounds (2004) were 

used. These initial inflows were then adjusted in a second 

simulation for each environmental scenario to eliminate the 

difference between simulated and measured streamflows in 

each branch. This adjustment was justified because it could not 

be assumed that groundwater inflow and the cumulative inflow 

from small unmeasured creeks would remain similar from 

year to year. 

Additional inflow to the model included municipal 

wastewater effluent from the cities of Stayton and 

Jefferson. Records containing daily effluent discharges for 

both municipalities were provided in monthly Discharge 

Monitoring Reports (DMRs) to ODEQ (Robert Dicksa, 

Oregon Department of Environmental Quality, written 

commun., 2011).

Surface-Water Withdrawals

Surface-water withdrawals from the river model included 

municipal water supply (cities of Gates, Mill City, Salem, 

Stayton, and Jefferson) and irrigation (Santiam Water Control 

District and the Sidney Irrigation Cooperative) (fig. 3). Data 

for these withdrawals were provided by the Oregon Water 

Resources Department Water Use Reporting Database. 

Although the withdrawals were reported as monthly total 

volumes, they were converted to a rate in cubic meters per 

second for the model. Monthly withdrawal rates were assigned 

to just the midpoint of each month, and the model then was set 

up to linearly interpolate between those monthly midpoints for 

each model time step. 

Appendix D. North Santiam and Santiam River Model Set-Up and Application
62 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

Boundary Water Temperatures 

Using the same methods employed by Sullivan and 

Rounds (2004), measured or estimated water temperatures 

were assigned to all boundary flows entering the river model. 

For testing purposes and for simulating existing conditions, 

hourly water temperature data measured in the North Santiam 

River at Niagara (USGS station 14181500) were used as the 

upstream boundary for the model at Big Cliff Dam. For other 

model scenarios, simulated release temperatures from the Big 

Cliff Reservoir model were used.

Measured hourly water temperature data were available 

for the Little North Santiam River near Mehama (USGS site 

14182500). Measured hourly water temperature data from 

Rock Creek near Mill City (USGS site 14181750) were 

available only for 2006. Although Sullivan and Rounds (2004) 

used measured water temperature data from the Little North 

Santiam River near Mehama as estimated water temperatures 

for Rock Creek in their 2001–02 simulations, a comparison 

of water temperatures in Rock Creek and the Little North 

Santiam River showed that Little North Santiam River water 

temperatures were about 10°C warmer than temperatures in 

Rock Creek in summer. Because of that difference, measured 

hourly water temperature data from 2006 for the Rock Creek 

site were used for all three (hot/dry, normal, and cool/wet) 

environmental scenarios.

Measured daily-mean air temperature data for 

precipitation entering the river model through the water 

surface were available from the Detroit and Stayton 

NCDC meteorological stations that were used for the daily 

precipitation data. Data from the Detroit station were used for 

branches 1–2, and data from the Stayton station were used 

for branches 3–6.

Water temperatures for groundwater and ungaged 

tributaries flowing into the six model branches were estimated 

using a weighted average approach from Sullivan and Rounds 

(2004). For the two upstream model branches, 70 percent 

of the flow was assumed to come from ungaged tributaries. 

Daily-mean water temperatures measured at the Little 

North Santiam River near Mehama (USGS site 14182500) 

were used for this portion of the flow. For the remaining 

30 percent of flow, which was assumed to be groundwater, 

a constant temperature of 11.5°C was assigned. For the four 

downstream model branches, flow was weighted as 50 percent 

ungaged tributary flow and 50 percent groundwater and the 

temperatures were estimated accordingly.

For the Stayton and Jefferson municipal wastewater 

outflows, measured daily-mean water temperatures were taken 

from information included in the monthly DMRs provided to 

ODEQ.

Meteorological Data

Meteorological inputs for the three environmental 

scenarios for the river model were constructed using the 

same data sources and methods as those used by Sullivan and 

Rounds (2004). Air temperature, dew-point temperature, wind 

speed, and wind direction data were obtained from the Stayton 

meteorological site. Solar radiation data were obtained from 

the Solar Radiation Monitoring Laboratory at the University 

of Oregon for their meteorological site in Eugene. Cloud cover 

data were computed using a comparison between measured 

and theoretical clear-sky solar radiation rates, in which the 

nighttime cloud cover information was interpolated from 

values near sunrise and sunset. For more information on these 

data sources and methods, see Sullivan and Rounds (2004).
Appendix E 63

Some of the model scenarios included in this study 

resulted in temperature releases from Detroit Dam that 

were either not very successful in matching the intended 

downstream target or closely matched those of another 

scenario. This appendix is dedicated to the archival of that set 

of model scenarios.

Late Refill of Detroit Lake

Delaying the time at which Detroit Lake begins to fill 

from February 1 to June 1 results in the operational scenario 

late_refill (fig. E1, tables 4 and 5). The thinking behind 

this scenario was that by keeping the lake level low during 

spring, it might be easier or more efficient to pass juvenile 

fish downstream past the dam. Insufficient streamflow was 

available to fill the lake after June 1, and the lake level 

remained well below full pool level for the rest of the summer 

under all three environmental scenarios. Temperatures released 

from existing outlets under this late-refill scenario generally 

did not meet the max temperature targets for much of the year 

(fig. E2). Early in the summer, power production constraints 

and a water level that was too low to use the spillway resulted 

in water releases that were cooler than the target. In autumn, 

the lake level was too low for existing outlets to access 

sufficient cool water, and the water releases were too warm.

Appendix E. Additional Model Scenarios

Full pool

Spillway

Inflow, in cubic feet per second

500

1,000

2,000

5,000

10,000

20,000

Outflow, in cubic feet per second

500

0

1,000

2,000

5,000

10,000

20,000

Calendar month/day

Elevation, in feet

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/1211/1911/2612/0312/1012/1712/2412/31

1,440

1,460

1,480

1,500

1,520

1,540

1,560

1,580

cool/wet late refill

normal late refill

hot/dry late refill

Rule curve

Alt curve

EXPLANATION

A.

B.

C.

0

Figure E1. Comparison of late_refill operational scenarios (c4, n4, h4): (A) total inflows, (B) total outflows, and 

(C) modeled water-surface elevation. 
64 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

Early Drawdown of Detroit Lake

Changing the time at which the Detroit Lake level 

reaches its minimum conservation pool from December 1 

to November 1 results in the operational scenario early_dd

(tables 4, 5, and fig. E3). Despite the earlier drawdown, this 

operational scenario had little effect on the date at which the 

use of the spillway was no longer an option, as the lake level 

under base operations tended to decrease to the elevation 

of the spillway crest before this change occurred. However, 

the earlier drawdown caused the thermocline to be drawn 

down to the level of the available outlets sooner than in base 

operations, which caused the max temperature target generally 

not to be met during October and November (fig. E4).

Power Penstocks with Floating Outlet 

and 10 Percent Minimum Power 

Generation

Several model scenarios were run with the pp-float

structural option and a combination of flow constraints. In that 

group, this scenario specified that a minimum of 10 percent 

tac12-0772_figE02

38

40

42

44

46

48

50

52

54

56

58

60

62

64

3.3

4.4

5.6

6.7

7.8

8.9

10.0

11.1

12.2

13.3

14.4

15.6

16.7

17.8

Calendar month/day

Percent spill

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/12

11/1911/2612/0312/1012/1712/2412/31

25

50

75

100

Temperature, in degrees Celsius 

Temperature, in degrees Fahrenheit 

0

Max/min ttarg

cool/wet_late_refill

normal_late_refill

hot/dry_late_refill

A. EXPLANATION

B.

Figure E2. (A) Modeled water temperature and (B) percent spill for existing structural scenarios (c4, n4, h4) with 

late_refill operations and max temperature targets. The maximum and minimum temperature target established 

for the McKenzie River (labeled “Max/min ttarg”) is shown but only the maximum was used in this simulation.

of the total outflow be released through the power penstocks 

(table 7), providing another point in a continuum between a 

scenario with no power generation constraint (c10, n10, h10) 

and a scenario with a 20 percent power generation minimum 

(c12, n12, h12). Used with the max temperature targets, 

the results did not meet the target release temperatures in 

October and November for the hot/dry environmental scenario 

(compare fig. E5 with figs. 21 and 22).

Sliding-Gate and Floating Outlets with 

Delayed Drawdown

The combination of a sliding-gate outlet and a floating 

outlet (slider1340-float) along with delayed drawdown 

operations (delay_dd2) provided another combination that was 

of interest and similar to a couple of scenarios documented in 

the main part of this report (table 7). Results from c18, n18, 

and h18 are almost identical to results from uro-float_400fmin 

scenarios c14, n14, and h14 (fig. E6).
Appendix E 65

tac12-0772_figE03

Full pool

Spillway

cool/wet early dd

normal early dd

hot/dry early dd

Rule curve

Alt curve

Inflow, in cubic feet per second

500

1,000

2,000

5,000

10,000

20,000

Outflow, in cubic feet per second

500

0

0

1,000

2,000

5,000

10,000

20,000

Calendar month/day

Elevation, in feet

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/1211/1911/2612/0312/1012/1712/2412/31

1,440

1,420

1,460

1,480

1,500

1,520

1,540

1,560

1,580

EXPLANATION

A.

B.

C.

Figure E3. Comparison of early_dd operational scenarios (c5, n5, h5): (A) total inflows, (B) total outflows, and 

(C) modeled water-surface elevation. 
66 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

tac12-0772 figE04

Max/min ttarg

cool/wet_early_dd

normal_early_dd

hot/dry_early_dd

EXPLANATION

38

40

42

44

46

48

50

52

54

56

58

60

62

64

3.3

4.4

5.6

6.7

7.8

8.9

10.0

11.1

12.2

13.3

14.4

15.6

16.7

17.8

Calendar month/day

Percent spill

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/12

11/1911/2612/0312/1012/1712/2412/31

25

50

75

100

Temperature, in degrees Celsius 

Temperature, in degrees Fahrenheit 

0

A.

B.

Figure E4. (A) Modeled water temperature and (B) percent spill for existing structural scenarios (c5, n5, h5) with 

early_dd operations and max temperature targets. The maximum and minimum temperature target established for 

the McKenzie River (labeled “Max/min ttarg”) is shown but only the maximum was used in this simulation.
Appendix E 67

tac12-0772 figE05 Fixed out, in cubic feet per second 

10

50

100

500

1,000

5,000

10,000

Floating out, in 

cubic feet per second 

10

50

100

500

1,000

5,000

10,000

38

40

42

44

46

48

50

52

54

56

58

60

62

64

3.3

4.4

5.6

6.7

7.8

8.9

10.0

11.1

12.2

13.3

14.4

15.6

16.7

17.8

Temperature, in degrees Celsius 

Temperature, in degrees Fahrenheit 

Calendar month/day

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/12

11/1911/2612/0312/1012/1712/2412/31

Max/min ttarg

cool/wet pp−float 10ppmin

normal pp−float 10ppmin

hot/dry pp−float 10ppmin

EXPLANATION

A.

B.

C.

Figure E5. Results from pp-float structural scenarios with 10ppmin operations and max temperature targets 

(scenarios c11, n11, h11): (A) modeled water temperature, (B) outflow from fixed outlet, and (C) outflow from 

floating outlet. The maximum and minimum temperature target established for the McKenzie River (labeled 

“Max/min ttarg”) is shown but only the maximum was used in this simulation.
68 Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management

tac12-0772 figE06

Max/min ttarg

cool/wet delay dd2 slider1340−float

normal delay dd2 slider1340−float

hot/dry delay dd2 slider1340−float

EXPLANATION

Sliding out, in 

cubic feet per second 

10

50

100

500

1,000

5,000

10,000

Floating out, in 

cubic feet per second 

10

50

100

500

1,000

5,000

10,000

38

40

42

44

46

48

50

52

54

56

58

60

62

64

3.3

4.4

5.6

6.7

7.8

8.9

10.0

11.1

12.2

13.3

14.4

15.6

16.7

17.8

Temperature, in degrees Celsius 

Temperature, in degrees Fahrenheit 

Calendar month/day

01/0101/0801/1501/2201/2902/0502/1202/1902/2603/0503/1203/1903/2604/0204/0904/1604/2304/3005/0705/1405/2105/2806/0406/1106/1806/2507/0207/0907/1607/2307/3008/0608/1308/2008/2709/0309/1009/1709/2410/0110/0810/1510/2210/2911/0511/12

11/1911/2612/0312/1012/1712/2412/31

A.

B.

C.

Figure E6. Results from slider1340-float structural scenarios with delay_dd2 operations and max temperature 

targets (scenarios c18, n18, h18): (A) modeled water temperature, (B) outflow from sliding outlet, and (C) outflow 

from floating outlet. The maximum and minimum temperature target established for the McKenzie River (labeled 

“Max/min ttarg”) is shown but only the maximum was used in this simulation.
Publishing support provided by the U.S. Geological Survey

Publishing Network, Tacoma Publishing Service Center

For more information concerning the research in this report, contact the

 Director, Oregon Water Science Center

U.S. Geological Survey

2130 SW 5th Avenue

Portland, Oregon 97201

http://or.water.usgs.gov
Buccola and others—Potential Structural and Operational Changes, North Santiam River, Oregon, for Temperature Management—Scientific Investigations Report 2012–5231