U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2007-5008

Modeling Hydrodynamics, Water Temperature, and 

Suspended Sediment in Detroit Lake, Oregon

Prepared in cooperation with the City of Salem, Oregon
Front Cover:

Photograph of Detroit Lake and Piety Island, looking east. (Photograph by Mark Uhrich, U.S. Geological Survey, September 29, 2004.)

Insets from left to right:

Inset 1: Photograph showing aerial view of Detroit Dam, taken from just west of the dam. (Photograph from U.S. Army Corps of Engineers, July 11, 1990.)

Inset 2: Photograph showing Breitenbush River storm inflow to Detroit Lake, looking west. (Photograph by Heather Bragg, U.S. Geological Survey, April 14, 2002.)

Inset 3: Photograph showing Breitenbush River inflow to Detroit Lake, looking west. (Photograph by Heather Bragg, U.S. Geological Survey, November 7, 2006.)

Back Cover: View of Mt. Jefferson over Detroit Lake, looking east. (Photograph by David Piatt, U.S. Geological Survey, July 4, 2004.)
Modeling Hydrodynamics, Water 

Temperature, and Suspended Sediment in 

Detroit Lake, Oregon

By Annett B. Sullivan, Stewart A. Rounds, Steven Sobieszczyk, and Heather M. Bragg

Prepared in cooperation with the City of Salem, Oregon

Scientific Investigations Report 2007–5008

U.S. Department of the Interior

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

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2007

For product and ordering information:

World Wide Web: http://www.usgs.gov/pubprod

Telephone: 1-888-ASK-USGS

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

natural hazards, and the environment:

World Wide Web: http://www.usgs.gov

Telephone: 1-888-ASK-USGS

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:

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.
iii

Contents

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

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

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

Background............................................................................................................................................2

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

Methods and Data .........................................................................................................................................4

Model Grid..............................................................................................................................................4

Meteorological Data.............................................................................................................................5

Hydrological Data .................................................................................................................................5

Inflow Water Temperature and Water Quality Data .......................................................................6

Lake Profile Data...................................................................................................................................7

Outflow Water Temperature and Water Quality Data.....................................................................8

Model Development ......................................................................................................................................8

Water Balance ......................................................................................................................................8

Water Temperature ..............................................................................................................................8

Total Dissolved Solids ........................................................................................................................16

Suspended Sediment .........................................................................................................................23

Model Sensitivity..........................................................................................................................................32

Model Applications......................................................................................................................................33

Characteristics of Sediment Inflows, Outflows, and Deposits....................................................33

Sources of Sediment to the Reservoir Outflow ............................................................................35

Effect of Dam on Release Water Temperature ..............................................................................36

Summary and Future Work.........................................................................................................................38

Acknowledgments.......................................................................................................................................39

Supplemental Material................................................................................................................................39

References Cited..........................................................................................................................................40
iv

Figures

Figure 1. Map showing locations of water-quality monitors and lake sampling sites in the

Detroit Lake drainage area, Oregon ...................................................... 3

Figure 2. Map showing location of segment boundaries for the Detroit Lake model grid ... 5

Figure 3. Graph showing volume-elevation curves for Detroit Lake, Oregon, from the U.S.

Army Corps of Engineers (USACE) and as represented by the model grid ......... 5

Figure 4. Graph showing measured and modeled forebay water-surface elevations,

Detroit Lake, Oregon, calendar years 2002 and 2003, and the period between

December 1, 2005, and February 1, 2006 ................................................ 9

Figure 5. Graph showing modeled water temperature profiles in Detroit Lake, Oregon,

near the dam as a function of time during 2003.......................................... 9

Figure 6. Measured water temperature profiles at three locations in Detroit Lake,

Oregon, compared to modeled water temperature at the same location and

time in 2002 ................................................................................. 10

Figure 7. Measured water temperatures profiles at three locations in Detroit Lake,

Oregon, compared to modeled water temperature at the same location and

time in 2003 ................................................................................. 12

Figure 8. Measured water temperature profiles at four locations in Detroit Lake,

Oregon, compared to modeled water temperature at the same location and

time in 2006 ................................................................................. 14

Figure 9. Graphs showing measured water temperatures from a string of thermistors

suspended from the log boom in Detroit Lake, Oregon, compared to

modeled water temperature at the same depth and time in 2003 ..................... 15

Figure 10. Graph showing modeled water temperatures in the Detroit Lake, Oregon,

reservoir outflow compared to measured water temperature in the North

Santiam River at Niagara, 6 km downstream of the reservoir outflow in 2003 ...... 16

Figure 11. Modeled total dissolved solids profiles in Detroit Lake, Oregon, near the dam

as a function of time during 2003 ......................................................... 17

Figure 12. Measured specific conductance profiles at three locations in Detroit Lake,

Oregon, compared to modeled specific conductance (derived from total

dissolved solids) at the same location and time in 2002 .............................. 18

Figure 13. Measured specific conductance profiles at three locations in Detroit Lake,

Oregon, compared to modeled specific conductance (derived from total

dissolved solids) at the same location and time in 2003 .............................. 20

Figure 14. Measured specific conductance profiles at four locations in Detroit Lake,

Oregon, compared to modeled specific conductance (derived from total

dissolved solids) at the same location and time in 2006 .............................. 22

Figure 15. Graph showing modeled specific conductance (converted from modeled total

dissolved solids) in the Detroit Lake, Oregon, reservoir outflow compared to

measured specific conductance in the North Santiam River at Niagara, 6 km

downstream, in 2003 ........................................................................ 22
Figure 16. Modeled profiles of suspended sediment concentrations in Detroit Lake,

Oregon, near the dam as a function of time during 2003 .............................. 24

Figure 17. Total suspended sediment concentration profiles, both measured and

calculated from turbidity, at three locations in Detroit Lake, Oregon,

compared to modeled total suspended sediment concentration at the same

location and time in 2002 .................................................................. 26

Figure 18. Total suspended sediment concentration profiles, both measured and

calculated from turbidity, at three locations in Detroit Lake, Oregon,

compared to modeled total suspended sediment concentration at the same

location and time in 2003 .................................................................. 28

Figure 19. Total suspended sediment concentration profiles, both measured and

calculated from turbidity, at four locations in Detroit Lake, Oregon, compared

to modeled total suspended sediment concentration at the same location and

time in 2006 ................................................................................. 30

Figure 20. Profiles showing chemical (pH and dissolved oxygen) and physical (surface

turbidity) evidence of an algal bloom at the Blowout lake monitoring site,

Detroit Lake, Oregon, June 12, 2002 ...................................................... 30

Figure 21. Graphs showing modeled total suspended sediment concentration in

reservoir outflow, converted to turbidity and modeled distribution of two

sediment size groups, Detroit Lake, Oregon, 2003 ....................................... 31

Figure 22. Maps showing modeled spatial distribution of suspended sediment

deposition in Detroit Lake, Oregon, for calendar years 2002, 2003, and the

period between December 1, 2005 and February 1, 2006 .............................. 34

Figure 23. Graphs showing modeled sources of total sediment in reservoir outflow of

Detroit Lake during 2003 .................................................................. 36

Figure 24. Graphs showing (A) Maximum water temperature standard for the North

Santiam River, Oregon, downstream of Big Cliff and Detroit Dams, an

estimate of the water temperatures in the absence of the dams calculated

using a volume-weighted mix of reservoir inflows for 2003, and modeled

water temperatures of the water released from Detroit Dam and (B)

smoothed water temperature of the volume-weighted mix of the reservoir

inflows, used as a temperature target for the selective withdrawal simulation,

along with the modeled reservoir release temperatures for that scenario ......... 37

Figure 25. Modeled water temperature profiles in Detroit Lake, Oregon, near the dam as

a function of time during 2003 for calibrated conditions, and the selective

withdrawal scenario ........................................................................ 38

Figures—continued
vi

Tables

Table 1. Regression equations for estimating total and clay-size suspended sediment

concentrations from turbidity data for the major tributaries to Detroit Lake,

Oregon ....................................................................................... 7

Table 2. Model parameters and values used in the Detroit Lake, Oregon, model ............ 7

Table 3. Detroit Lake model Goodness-of-fit statistics, calendar years 2002 and 2003

and a storm event in January 2006 ...................................................... 17

Table 4. Results from sensitivity testing showing the effect of changing a particular

input parameter on annual average temperature, suspended sand and silt,

and suspended clay in the whole lake and in the lake outflow for 2003 ............ 32

Table 5. Modeled sand and silt, clay, and total sediment entering, exiting, and

deposited in Detroit Lake for the three modeled time periods ........................ 33

Table 6. Fate of suspended sand and silt, and suspended clay from the major

tributaries to Detroit Lake, Oregon, 2003 ................................................ 35

Conversion Factors and Datums

SI to Inch-Pound

Multiply By To obtain

centimeter (cm) 0.394 inch (in.)

centimeter per second (cm/s) 0.394 inch per second (in/s)

centimeter per square second (cm/s2

) 0.394 inch per square second (in/s2)

cubic meter (m3

) 264.2 gallon (gal) 

cubic meter (m3

) 0.0008107 acre-foot (acre-ft) 

gram per cubic centimeter (g/cm3

) 62.4220 pound per cubic foot (lb/ft3) 

kilometer (km) 0.6214 mile (mi)

kilogram (kg) 2.205 pound avoirdupois (lb)

kilogram per square meter (kg/m2

) 0.2048 pound per square foot (lb/ft2)

meter (m) 3.281 foot (ft) 

meter per day (m/d) 3.281 foot per day (ft/d)

metric ton 1.102 ton

square meter per gram (m2

/g) 4882 square foot per pount (ft2/lb)

square meter per second (m2

/s) 10.76 square foot per second (ft2/s)

square kilometer (km2

) 247.1 acre

square centimeter (cm2

) 0.001076 square foot (ft2)

square meter (m2

) 10.76 square foot (ft2) 

square centimeter (cm2

) 0.1550 square inch (ft2)

square kilometer (km2

) 0.3861 square mile (mi2)

Watt per square meter per second 

[(W/m2

)/s]

0.317 BTU per square foot per second 

[(BTU/ft2)/s]
vii

Conversion Factors and Datums—continued

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

°F=(1.8×°C)+32

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

25 °C).

Concentrations of chemical constituents in water generally are given in milligrams per liter 

(mg/L), which is approximately equal to parts per million.

Turbidity is given in Formazin Nephelometric Units, or FNUs.

Datum

Horizontal coordinate information is referenced to North American Datum of 1927 (NAD27).

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

(NGVD29).
viii

This page intentionally left blank.
Abstract

Detroit Lake is a large reservoir on the North Santiam 

River in west-central Oregon. Water temperature and 

suspended sediment are issues of concern in the river 

downstream of the reservoir. A CE-QUAL-W2 model was 

constructed to simulate hydrodynamics, water temperature, 

total dissolved solids, and suspended sediment in Detroit Lake. 

The model was calibrated for calendar years 2002 and 2003, 

and for a period of storm runoff from December 1, 2005, 

to February 1, 2006. Input data included lake bathymetry, 

meteorology, reservoir outflows, and tributary inflows, 

water temperatures, total dissolved solids, and suspended 

sediment concentrations. Two suspended sediment size 

groups were modeled: one for suspended sand and silt with 

particle diameters larger than 2 micrometers, and another for 

suspended clay with particle diameters less than or equal to 2 

micrometers. The model was calibrated using lake stage data, 

lake profile data, and data from a continuous water-quality 

monitor on the North Santiam River near Niagara, about 

6 kilometers downstream of Detroit Dam. The calibrated 

model was used to estimate sediment deposition in the 

reservoir, examine the sources of suspended sediment exiting 

the reservoir, and examine the effect of the reservoir on 

downstream water temperatures.

Significant Findings

An annual pattern of water temperature exists in Detroit 

Lake that was similar in all modeled time periods. The 

reservoir typically is isothermal and cold at the beginning 

of the year. In spring, the lake surface warms and a 

thermocline develops by summer, isolating cold, dense 

water at the reservoir bottom. In autumn, the water surface 

cools, and eventually the reservoir mixes, or “turns over,” 

and becomes isothermal again.

1.

Detroit Lake has an important influence on downstream 

water temperature in the North Santiam River. Reservoir 

outflow water temperature reaches an annual maximum 

in autumn, at times exceeding the water temperature 

criterion. In the absence of Detroit Dam, the annual water 

temperature maximum would occur in midsummer. Water 

released from Detroit Lake also has less daily temperature 

variation compared to what would occur in the absence of 

the lake.

Model results demonstrated that if a selective withdrawal 

device were installed at Detroit Dam, water temperatures 

of the outflow from Detroit Lake could remain less than 

Oregon’s maximum water temperature criteria for the 

North Santiam River all year. A more natural seasonal 

temperature pattern could be produced through most of 

the year, but in autumn, the lake did not have enough 

stored cold water to match this hypothetical seasonal 

temperature pattern downstream of the dam.

Total dissolved solids (TDS) had an annual cycle in 

Detroit Lake. During spring storms, the inflowing TDS 

concentrations were relatively low. As the lake was not 

yet strongly stratified, these inflows acted to decrease 

TDS throughout the lake. As summer progressed, TDS 

concentrations in the inflows typically increased. The 

summer temperature stratification acted to keep summer 

inflows, with their higher TDS concentrations, in the 

epilimnion, preventing these inflows from mixing into 

the colder, denser hypolimnion. With the breakdown 

of stratification in autumn, waters with higher TDS 

concentrations in the epilimnion were mixed throughout 

the lake.

The largest suspended sediment loads entered Detroit 

Lake during storm events. During the record-breaking 

precipitation between December 1, 2005, and February 1, 

2006, more mass of suspended sediment entered and was 

deposited in the reservoir than in the entire calendar years 

of 2002 and 2003 combined. In summer, when storms 

were few, the inflow of suspended sediment into the lake 

was small, and resultant lake concentrations also were 

low.

2.

3.

4.

5.

Modeling Hydrodynamics, Water Temperature, and 

Suspended Sediment in Detroit Lake, Oregon

By Annett B. Sullivan, Stewart A. Rounds, Steven Sobieszczyk, and Heather M. Bragg
Most of the mass of sediment entering Detroit Lake was 

in a size class designated “sand and silt.” Sediment in that 

size class comprised 85 percent of the inflowing mass in 

calendar year 2002, 83 percent in calendar year 2003, and 

92 percent during the modeled 2005–06 storms.

Although the sand and silt component made up most of 

the mass of suspended sediment entering the reservoir, it 

comprised only a small portion of the suspended sediment 

exiting the reservoir. It constituted only 9 percent of 

the outflowing sediment mass in calendar year 2002, 

7 percent in 2003, and 16 percent during the modeled 

2005–06 storms. Most of the mass of sediment leaving 

Detroit Lake was composed of clay-sized particles.

Assuming a bulk density of 1.89 g/cm3, 14,300 m3 

(11.6 acre-ft) of sediment was deposited in Detroit Lake 

in 2002, 11,820 m3 (9.6 acre-ft) in 2003 and 34,900 

m3

 (28.3 acre-ft) in storms from December 1, 2005, to 

February 1, 2006. Each of these sediment volumes is 

less than 0.01 percent of Detroit Lake’s full pool volume 

of 561 million m3 (455,000 acre-ft). The model results 

indicate that most sediment deposition occurred in 

the upper reaches of the reservoir, near the inflows of 

Breitenbush and North Santiam Rivers.

All inflows contributed suspended sediment to the 

reservoir outflow. The North Santiam River was the 

largest contributor, followed by Breitenbush River, in 

calendar year 2003. The North Santiam River was unique 

in that it contributed sediment to the outflow in October 

and November, when contributions from other tributaries 

decreased. Tributaries that entered Detroit Lake closer 

to the dam were more likely to contribute suspended 

sediment that was exported to the North Santiam River 

downstream of the dam.

Introduction 

Background

The U.S. Army Corps of Engineers (USACE) constructed 

and operates a system of 13 dams and reservoirs in Oregon’s 

Willamette Basin; Detroit Lake is one of the larger of these 

reservoirs on the western slope of the Cascade Range. The 

lake is situated on the North Santiam River (fig. 1) behind 

Detroit Dam, a 141-m high concrete structure finished in 

1953. The watershed encompasses 1,130 km2

, and at a fullpool water-surface elevation of 478.2 m, 561 million m3

(455,000 acre-ft) of water is stored in the reservoir, with a 

surface area of 14.5 km2. The water-surface elevation varies 

substantially, by 35 m or more, over the course of a year. It 

is kept high in summer for recreation, and drawn down in 

6.

7.

8.

9.

winter for flood control. Detroit Lake also is used for power 

generation, irrigation, and improvement of downstream 

navigation.

A smaller, reregulating dam, Big Cliff, lies 5 km 

downstream of Detroit Dam. It is designed to dampen the 

flow variations caused by Detroit Dam’s power generating 

operations. There are an additional 36 km2

 of watershed area 

between Detroit and Big Cliff Dams. At a full-pool watersurface elevation of 367.7 m, Big Cliff Reservoir holds 

8 million m3 (6,450 acre-ft of water), with a surface area of 

0.6 km2.

Major inflows to Detroit Lake include the North Santiam 

and Breitenbush Rivers, and French, Blowout, Box Canyon, 

and Kinney Creeks. The watershed reaches its highest point 

at Mount Jefferson at 3,204 m. The climate of this area is a 

temperate one, characterized by dry summers and wet winters. 

Mean annual precipitation for 1971–2000 was 228 cm, and 

most fell between November and April (Taylor, 2002). For 

the same period, the average annual air temperature at Detroit 

Dam was 10.6 oC. The coldest month was January, with 

an average temperature of 3.7 oC, and the warmest month 

was August, with an average temperature of 18.8 oC. The 

watershed geology is dominated by volcanic andesites and 

basalts with some alluvial and glacial deposits (Uhrich and 

Bragg, 2003). Steep slopes and weathered, clay-rich soils 

lead to landslides and earthflows that deliver sediment into 

many of the creeks and rivers of the upper basin. The land 

is mostly forested, and timber harvesting and recreation are 

the largest land uses. More than 95 percent of the land in the 

watershed upstream of Detroit Dam is part of the Willamette 

National Forest, with the rest divided between the Mount 

Hood National Forest, private owners, the Oregon Department 

of Forestry (ODF), the Warm Springs Indian Reservation, and 

the Bureau of Land Management.

Downstream of Detroit and Big Cliff Dams, the North 

Santiam River flows 75 km to the Santiam River, which flows 

20 km to the Willamette River between the cities of Albany 

and Salem. The North Santiam River is governed by Oregon’s 

“Three Basin Rule” (Oregon Department of Environmental 

Quality, 2003), designed to protect the river’s water quality, 

particularly as a source of clean drinking water. The rule has 

been successful at limiting new point source discharges into 

the river. Water temperature and suspended sediment, however, 

remain issues of concern.

Portions of the North Santiam and Santiam Rivers 

downstream of Detroit Lake exceed Oregon’s maximum 

water temperature criteria at times, and these reaches were 

included on Oregon’s most recent 303(d) list of impaired 

waterbodies (Oregon Department of Environmental Quality, 

2006). To address this issue, a water temperature TMDL 

(Total Maximum Daily Load) was developed for these and 

other rivers in the Willamette Basin; the TMDL was signed 

by Oregon’s Department of Environmental Quality on 

September 21, 2006. As part of that work, a hydrodynamic 

   Modeling Hydrodynamics, Water Temperature, and Suspended Sediment in Detroit Lake, Oregon
Figure 1. Locations of water-quality monitors and lake sampling sites in the Detroit Lake drainage area, Oregon.

OR19-0104_Fig01

OREGON

Salem

Big Cliff

Dam

Detroit

Dam

Breitenbush

River

Santiam

Blowout

Creek

Mongold

Blowout

Kinney

Kinney Creek

Box

Canyon

Creek

Niagara

French Creek

Mt

Jefferson

Mongold-South

Mongold-North

River

North

Detroit Lake

Drainage

area for 

gaging

station at 

Niagara

EXPLANATION

Drainage area upstream of Detroit Dam

Meteorological station

Sampling sites

Log boom

USGS water-quality monitors

0 5 10 15 KILOMETERS

0 5 10 MILES

122°20' 10' 122°00' 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.

and water temperature model was developed, and simulations 

were run, to examine the effects of riparian shading, weather 

conditions, point sources, and Detroit Dam release flows and 

temperatures on North Santiam River water temperatures 

(Sullivan and Rounds, 2004). That study showed that water 

temperatures in these rivers were indeed sensitive to the 

temperatures and flows released from Detroit Dam, as well 

as some of the other factors. Although State temperature 

criteria focus on problems related to water that is too warm, 

temperatures also can be too cool for fish at times. Populations 

of spring Chinook salmon (Oncorhynchus tshawytscha) 

are declining in the North Santiam River, and dam outflow 

temperatures that are too cool in midsummer may be a 

contributing factor (E&S Environmental Chemistry, Inc. and 

North Santiam Watershed Council, 2002). The outflow of 

Detroit Lake in June generally is 5–7 oC, cooler than the ideal 

of 10–13 oC for migrating adult Chinook (Larson, 2000). 

Introduction    
Suspended sediment concentrations in the North Santiam 

River also can be of concern. The City of Salem takes its 

primary supply of drinking water from the North Santiam 

River approximately 45 km downstream of Detroit Lake. In 

the past, during some large storms and periods of sustained 

high levels of turbidity in the lake, high concentrations of 

suspended sediment in the North Santiam River have required 

the city to shut off its water intake and, later, to construct a 

chemical pretreatment system. The U.S. Geological Survey 

(USGS) has worked in partnership with the City of Salem 

since 1998 to monitor and study sediment and turbidity 

throughout the North Santiam River watershed (Uhrich and 

Bragg, 2003; Bragg and Uhrich, 2004).

Purpose and Scope 

Developing a model that simulates the transport and fate 

of suspended sediment and the dynamics of water temperature 

in Detroit Lake is an important component of understanding 

how the lake affects suspended sediment and temperature 

in the North Santiam and Santiam Rivers downstream of 

Detroit Lake. The objectives of this study were to (1) develop 

a model of Detroit Lake to simulate circulation, water 

temperature, TDS, and suspended sediment in the reservoir 

and the reservoir’s outflow, (2) understand processes affecting 

suspended sediment and quantify sediment sources and 

transport to the lake outlet as well as deposition in the lake, 

and (3) understand processes controlling water temperature 

in the lake and lake outflow, and demonstrate the water 

temperature effects of a hypothetical selective withdrawal 

device. 

The Detroit Lake model, described in this report, was 

developed for the entire calendar years of 2002 and 2003 and 

also for the period December 1, 2005, through February 1, 

2006 (the “2005–06 storms”) in order to simulate some large 

winter storm events. During January 2006, about 70 cm 

(27.6 in.) of precipitation were recorded at Detroit Dam, 

making it the wettest January ever recorded, breaking the 

previous record set in 1970 (Oregon Climate Service, 2006). 

Processes occurring in Big Cliff Reservoir, the reregulating 

reservoir downstream of Detroit Lake, were not included in 

this model. The monitoring station on the North Santiam River 

at Niagara is downstream of Big Cliff Dam, and outflows 

from Detroit Lake could be influenced by processes in the 

6 km reach between the outflow and Niagara, including heat 

exchange across the air-water interface, and tributary inflows.

This investigation resulted from a scientific and financial 

partnership between the USGS and the City of Salem, Oregon. 

Funding for the installation of a meteorological station near 

Detroit Lake was provided by USACE.

Methods and Data

The Detroit Lake model was constructed with CE-QUALW2, a two-dimensional, laterally-averaged, hydrodynamic 

and water quality model from the USACE (Cole and Wells, 

2002). The same model was used in the Oregon Department 

of Environmental Quality’s TMDL work for the Willamette 

River, including the Santiam and North Santiam subbasins. 

CE-QUAL-W2 is capable of simulating hydrodynamics, water 

temperature, and a number of other water quality constituents, 

including TDS, and multiple suspended sediment groups. A 

model grid based on the lake’s bathymetry was developed. 

Other model inputs included meteorology, inflows and 

outflows, inflow water temperatures, TDS concentrations, and 

suspended sediment concentrations. The water balance was 

calibrated by comparing modeled and measured lake stage 

for all modeled time periods. The model was calibrated for 

water temperature, TDS, and suspended sediment through 

comparisons of model output to measured data. All data 

used to run the Detroit Lake model, as well as measured 

profile data, are available online (see section, “Supplemental 

Material”).

Version 3.12 of CE-QUAL-W2 formed the basis of the 

Detroit Lake model. This version was modified by USGS 

project personnel to (1) fix coding errors either posted by 

CE-QUAL-W2’s development team or found by USGS, (2) 

add new model output fluxes related to sediment deposition, 

and (3) enhance model capabilities through the addition 

of a new subroutine to automatically blend outflows from 

multiple reservoir outlets to match a user-supplied downstream 

temperature target. All coding changes were extensively tested 

to assure proper model performance prior to their use. The 

blending routines were documented and applied previously by 

Sullivan and Rounds (2006). CE-QUAL-W2 uses a variable 

time step to ensure the numerical stability of its computational 

methods; this time step averaged 52 seconds for the 2002 

simulation, 49 seconds for 2003, and 23 seconds for 2005–06.

Model Grid

A geographic information system (GIS) dataset for 

Detroit Lake was created by combining a digital raster graphic 

of Detroit Lake with cross sections measured in the field by 

USGS personnel using acoustic Doppler techniques. Using 

GIS, the reservoir was divided into model segments (fig. 2). 

Ten equally spaced cross sections were subsampled from each 

segment using GIS techniques, then averaged to determine a 

representative cross section for each model segment.

 Modeling Hydrodynamics, Water Temperature, and Suspended Sediment in Detroit Lake, Oregon
Segments in CE-QUAL-W2 are grouped together into 

branches, which connect to form the model grid. The Detroit 

Lake grid consists of four model branches: The first, or main, 

branch has 33 segments, extending from the North Santiam 

River inflow to Detroit Dam. The second branch consists of 

11 segments, beginning at the Breitenbush River inflow and 

connecting to the main branch with a head boundary just 

downstream of Piety Island in Detroit Lake. The third branch 

consists of eight segments in the Blowout Creek arm of the 

lake, and the fourth branch comprises six segments in the 

Kinney Creek arm. French Creek was modeled as a tributary 

to the second branch, and Box Canyon Creek was modeled as 

a tributary to the third branch.

The volume-elevation curve resulting from this model 

grid was compared to a curve developed for the lake by 

USACE (fig. 3). From this comparison, the model grid was 

determined to be an accurate representation of the lake’s 

bathymetry. 

Meteorological Data

CE-QUAL-W2 requires air temperature, dew point 

temperature, wind speed, wind direction, and solar radiation 

or cloud cover data. In late September 2002, a Bureau of 

Reclamation Agrimet weather station was installed just north 

of Detroit Lake with funding from USACE. Because the entire 

2002 calendar year was modeled, a regression was developed 

for data collected at this weather station and a Remote 

Automated Weather Station (RAWS) site at Stayton (located 

approximately 45 km to the west of Detroit Dam) operated 

by ODF. This regression was used to extend the record of 

Figure 2. Location of segment boundaries for the Detroit Lake 

model grid. Branch 1, the main branch, extends from the North 

Santiam River inflow to the dam; the other branches join the main 

branch at the locations shown.

Figure 3. Volume-elevation curves for Detroit Lake, Oregon, 

from the U.S. Army Corps of Engineers (USACE) and as 

represented by the model grid.

OR19-0104_Fig02

 Piety

Island

Branch 1

Branch 3

Branch 1

Branch 2

Branch 4

Detroit

Dam

Base map modified from U.S. Geological Survey 

digital data (1:24,000). Projection: UTM, Zone 10, 

North American Datum of 1927.

Segment boundaries, Branch 1

Segment boundaries, Branches 2-4

EXPLANATION

21

21

0 3 4 KILOMETERS

0 3 MILES

122°15' 10' 122°07'

44°41'

44°45'

OR19-0104_Fig03

USACE

Model

360

380

400

420

440

460

480

0 100 200 300 400 500 600

ELEVATION, IN METERS ABOVE SEA LEVEL

LAKE VOLUME, IN MILLION CUBIC METERS

the Agrimet station back to January 1, 2002. Precipitation at 

Detroit Dam, reported by the Oregon Climate Service, also 

was included as input to the Detroit Lake model.

Wind speeds measured at the Agrimet weather station 

were lower than wind speeds reported on the lake by field 

crews and estimated by the Beaufort wind force scale, which 

relates wave heights and descriptions of conditions to wind 

speed. The lower wind speed at the Agrimet station probably 

was due to the site’s location in a forest clearing, not directly 

on or adjoining the lake. For the model, wind speed measured 

at the Stayton RAWS station was used instead; on average, 

these wind speeds were 10 to 15 times higher than values 

reported at the Detroit Agrimet station and more consistent 

with field observations on the lake.

Hydrological Data

Streamflow was measured at USGS gaging stations 

at 30-minute intervals on the main inflows to Detroit Lake 

including the North Santiam River, Breitenbush River, and 

Blowout Creek for all modeled time periods. French Creek 

flows were measured in 2002 and 2003, but not during the 

2005–06 storms. Kinney and Box Canyon Creeks were not 

gaged in any of the modeled years. The inflows from these 

major ungaged tributaries were estimated using the ratio 

of each stream’s watershed area to that of Blowout Creek 

upstream of the Blowout Creek gaging station and multiplying 

that ratio by the measured streamflow at the Blowout gaging 

station. Inflows to Detroit Lake generally were high during 

winter and spring storms, and low during the summer and 

early autumn.

Methods and Data 
Most releases from Detroit Lake were routed for power 

generation through two penstocks with a centerline elevation 

of 427.6 m (U.S. Army Corps of Engineers, 1953). When 

another outlet was needed to spill water, such as during a large 

storm, water was released through outlets with a centerline 

elevation of 408.4 m. These outlet centerline elevations are 

50.6 and 69.8 m below Detroit Lake’s full-pool elevation. 

Water for power generation was withdrawn from the lake 

during most of the year, but the amount of water withdrawn 

varied greatly over the course a day; those data were provided 

by USACE.

The water-surface elevation in Detroit Lake was 

measured in the forebay, the part of the lake just upstream 

of the powerhouse, and these data were compared to the 

modeled forebay elevations for the water balance calibration. 

The water-surface elevation of Detroit Lake varied by 

approximately 35 m in calendar years 2002 and 2003, and 

almost 30 m during the 2005–06 storms. The lake generally is 

filled by the end of May for boating and recreational uses, and 

gradually is drawn down beginning in September to provide 

storage for flood control through the winter.

Inflow Water Temperature and Water Quality 

Data

Water temperature, specific conductance, and turbidity 

data were recorded at 30-minute intervals by water quality 

monitors located in the North Santiam River, Breitenbush 

River, and Blowout Creek for all modeled years. These 

constituents were measured in French Creek in 2002 and 

2003, but not during the 2005–06 storms. The December 

2005–January 2006 French Creek data were estimated through 

correlations between French Creek and Breitenbush River data 

for 2002 and 2003. Water temperature, specific conductance, 

and turbidity were not measured for Kinney or Box Canyon 

Creeks in any of the modeled time periods. The inflow 

characteristics of these smaller tributary inflows were assumed 

to be similar to those in French Creek, which has similar 

watershed size.

All inflows were relatively cold to start the calendar year, 

warmed through spring to a maximum temperature in July, and 

cooled through autumn. Superimposed on this annual water 

temperature pattern were short term variations due to weather 

patterns and daily temperature cycles. The temperatures 

through the year were similar for all gaged inflows, except for 

Blowout Creek, which could be approximately 5oC warmer 

than the other inflows from June through October in the 

modeled time periods. This warmer temperature may have to 

do with sensor placement, and this may be investigated in the 

future by placing a probe in a different location in Blowout 

Creek.

Inflow specific conductance was lowest during the winter 

and spring, and reached a maximum in September to early 

November, repeating the seasonal shift from rainfall and 

snowmelt (low conductance) to ground water baseflow (higher 

conductance). The specific conductance in French Creek was 

the lowest of all gaged inflows, whereas specific conductance 

was the highest in Breitenbush River, which has geothermal 

influence. Some spikes (short-lived positive deviations) in 

specific conductance in Breitenbush River are currently 

unexplained (Bragg and Uhrich, 2004). To test whether these 

spikes affected the model results, they were removed for one 

model run, but were found to make no difference; therefore, 

the spikes were left unchanged in the final model inputs.

When using CE-QUAL-W2, it is desirable to simulate 

TDS instead of specific conductance because the model 

calculates water density as a function of temperature, TDS, 

and suspended sediment. Specific conductance and TDS are 

linearly related (Hem, 1985), because ions from dissolved 

solids make it possible for water to conduct an electric current. 

For the Detroit Lake model, then, TDS was simulated using 

TDS inputs that were converted from specific conductance 

data. According to Hem (1985), the relation between specific 

conductance and TDS can be described by: TDS = (SC) * 

A, where SC is specific conductance in microsiemens per 

centimeter, TDS is in units of milligrams per liter, and A is 

the slope of the relation between TDS and SC. The value of A 

generally ranges between 0.55 and 0.75. For the Detroit Lake 

model, the value of A was estimated to be 0.67. This relation 

was used to interconvert between SC and TDS.

Although turbidity was recorded at 30-minute intervals 

at many of Detroit Lake’s inflows, it is not a constituent 

that can be directly simulated by CE-QUAL-W2. Turbidity 

is a measure of the light-scattering properties of a liquid, and 

often can be directly related to the concentration of suspended 

particulate material in that liquid. Suspended sediment can be 

directly simulated by CE-QUAL-W2.

Relations between turbidity and total suspended 

sediment, and between turbidity and “persistent turbidity” 

— the long-lasting turbidity due to slowly settling small-sized 

suspended sediment—have been determined for Breitenbush 

River, French Creek, North Santiam River, and Blowout 

Creek (updated from Uhrich and Bragg, 2003; table 1). 

Concentrations for two sediment-size groups were determined 

for each inflow, using these relations and the measured 

30-minute turbidity data. The larger size group, “sand and 

silt,” was defined as sediment particles with a diameter larger 

than 2 μm, and the smaller-size group, “clay,” was defined as 

particles with a diameter less than or equal to 2 μm. The 2 μm 

cutoff was based on the persistent turbidity analysis by Uhrich 

and Bragg (2003). Concentrations of suspended sand and silt 

were obtained by subtracting the estimated concentration of 

suspended clay from the estimated total suspended sediment 

concentration.

 Modeling Hydrodynamics, Water Temperature, and Suspended Sediment in Detroit Lake, Oregon
Lake Profile Data

Vertical profiles of water temperature, specific 

conductance, pH, turbidity, and dissolved oxygen were 

measured with a multiparameter probe in Detroit Lake 

approximately every 3 weeks from April 2002 to October 

2003, and on January 13, 2006. The probes were calibrated 

and checked during each field trip. Water samples for 

suspended sediment analysis were taken at several discrete 

depths with a Van Dorn sampler. Light profiles were measured 

with a LI-COR LI-193SA spherical quantum sensor. Secchi 

depths were determined by lowering a Secchi disk into the 

water and noting the deepest depth at which the disk pattern 

could still be distinguished. These data were collected in 2002 

and 2003 at three sites in Detroit Lake: Kinney, Blowout, 

and Mongold (fig. 1). The Kinney site, downstream of the 

Kinney Creek inflow and the site closest to the dam, is the 

deepest site. The Blowout site, downstream of the Blowout 

Creek inflow, is of intermediate depth. The Mongold site, 

downstream of the confluence of the Breitenbush River and 

North Santiam River arms, is the shallowest of the three main 

sites. On January 13, 2006, the vertical profiles were taken at 

four sites: Kinney, Blowout, Mongold-North, and MongoldSouth. The latter two sites were upstream of the original 

Mongold site, on either side of Piety Island in Detroit Lake 

(fig. 1), and were sampled only in 2006. Water temperature at 

various depths in the lake also was measured using a string of 

thermistors suspended at varying depths from a log boom near 

the dam. Data were collected every hour at 23 depths, from 1 

to 80 m, from late May 2003 to early October 2003.

Lake light extinction coefficients, which describe how 

light is attenuated through the water column, were calculated 

for each site on each sampling date by three methods using 

the light profile and Secchi disk data (Sullivan and others, 

2006). Light extinction is affected by suspended sediment 

and algae in the lake, and in turn affects water temperature 

and the lake heat budget. A seasonal variation in the light 

extinction coefficient was observed in the lake. The highest 

light extinction coefficients, approaching 1.0 m-1, occurred in 

the lake from December through February in 2002 and 2003, 

presumably due to inflows with high turbidity associated with 

winter storms. Relatively high light extinction coefficients also 

were calculated in summer, probably related to algal blooms. 

The lowest light extinction coefficients occurred in late 

spring and early autumn. With a regression between average 

measured suspended sediment concentration in the photic zone 

and the light extinction data, the light extinction coefficient 

for water (λH2O), and the light extinction factor for suspended 

sediment (ε) were calculated to be 0.21 m-1, and 0.14 m2/g, 

respectively (table 2). The light extinction coefficient (λ) 

calculated by the model, then, is:

λ = λH20 + λSS , (1)

where:

λH20 is light extinction coefficient for lake water with no 

suspended sediment,

λSS is ε * SS,

ε is light extinction factor for suspended sediment, and

SS is suspended sediment concentration.

The fraction of solar radiation absorbed at the water 

surface (β), was set as 0.40, estimated from the light extinction 

coefficients and the equation (Cole and Wells, 2002):

β = 0.27 ln(λ) + 0.61 .	 (2)

Table 1. Regression equations for estimating total and clay-size 

suspended sediment concentrations from turbidity data for the 

major tributaries to Detroit Lake, Oregon. 

[The concentration of suspended sand and silt was determined by the 

difference between the estimated total and clay-size suspended-sediment 

concentrations. Abbreviations: SST, total suspended sediment, in milligrams 

per liter; Tb, Turbidity in FNU; SSC, Clay-size suspended sediment, in 

milligrams per liter]

Tributary Total suspended 

sediment

Clay-size suspended 

sediment

North Santiam River SST = 1.98 * Tb1.02 SSC = 1.17 * Tb0.55

Breitenbush River SST = 2.34 * Tb0.97 SSC = 1.23 * Tb0.55

French Creek SST = 1.21 * Tb0.97 SSC = 1.23 * Tb0.55

Blowout Creek SST = 1.64 * Tb1.08 SSC = 2.15 * Tb0.43

Table 2. Model parameters and values used in the Detroit Lake, 

Oregon, model. 

[Abbreviations: m, meter; m2/g, square meter per gram; °C, degree Celsius; 

(W/m2)/s, watt per square meter per second; m2/s, square meter per second; 

m/d, meter per day]

Parameter Value Description

WSC 1.0 Wind sheltering coefficient, dimensionless

EXH2O 0.21 Light extinction coefficient for water, m-1

EXSS 0.14 Light extinction due to inorganic suspended 

solids, m2

/g

BETA 0.40 Fraction of solar radiation absorbed at water 

surface, dimensionless

TSED 11.8 Sediment temperature, °C

CBHE 0.879 Coefficient of bottom heat exchange, (W/m2

)/s

AZMAX 0.001 Maximum vertical eddy viscosity, m2

/s

SSS1 21.0 Large suspended solids settling rate, m/d

SSS2 0.60 Small suspended solids settling rate, m/d

Methods and Data 
To plot and compare model output with measured profile 

lake data, modeled TDS concentrations were converted to 

specific conductance by the relation discussed section “Inflow 

Water Temperature and Water Quality Data.” Similarly, 

measured turbidity data from the vertical profiles were 

converted to suspended sediment concentrations by developing 

a relation between measured turbidity and measured 

suspended sediment in the lake, using data that had been 

collected at the same depth and the same time. This relation 

took the form:

SST = 0.7893 * Tb0.8361, R2 = 0.72 , (3)

where:

SST is total suspended sediment concentration in mg/L, 

and

Tb is turbidity, in FNU (Formazin nephelometric units, 

FNU, are similar to nephelometric turbidity units, 

NTU, but are from turbidity measurements made 

with infrared light, not white light [Anderson, 

2005]).

From this regression, the standard error in the predicted 

suspended sediment concentration for each turbidity was 

1.74 mg/L. Thus, the model may not be able to fit suspended 

sediment concentrations converted from measured turbidity 

with less error than this, because these derived values have 

about 1.7 mg/L of error intrinsic to the estimation.

Goodness-of-fit statistics were calculated between 

measured profile data and model output at the same location 

and time. Three statistics were calculated: mean error 

(ME), mean absolute error (MAE), and root mean square 

error (RMSE). ME is defined as the average difference 

between measured data and modeled values and is used as an 

indication of model bias. MAE is the average of the absolute 

values of differences between measured data and modeled 

values. RMSE is the square root of the mean of the squared 

differences. Both MAE and RMSE give an indication of the 

magnitude of the model’s prediction uncertainty for a typical 

data point. RMSE is similar to a standard error of the mean for 

the model’s uncertainty.

Outflow Water Temperature and Water Quality 

Data

Water temperature, specific conductance, and turbidity 

were measured at 30-minute intervals in the North Santiam 

River at Niagara, downstream of Detroit Dam (fig. 1). These 

data were useful for comparisons to model output for the 

outflow from Detroit Lake. However, the intervening 6 km 

reach between Niagara and the Detroit Lake outflow includes 

Big Cliff Reservoir and several small unmeasured tributary 

inflows. Thus, goodness-of-fit statistics were not calculated for 

these comparisons.

Model Development

Water Balance

The first comparison between measured and modeled 

lake water-surface elevation showed that the inflows initially 

included in the model did not account for all water entering 

the reservoir. Additional flows were needed to balance the 

water budget, especially in the winter during storms. These 

missing flows could be composed of small ungaged tributaries, 

overland flow during storms, or ground water seepage. 

They made up 10.8 percent of the total inflows in 2002, 9.4 

percent in 2003, and 20.0 percent for the 2005–06 storms. To 

account for these ungaged flows, a distributed tributary was 

added to each branch of the model. The distributed tributary 

inflows varied through the simulation period, and typically 

were greatest during storms. In CE-QUAL-W2, a distributed 

tributary inflow is apportioned to segments along an entire 

model branch according to segment surface area. The final 

modeled water-surface elevations, including the distributed 

tributary inflows, show good agreement with the measured 

water-surface elevations for 2002, 2003, and the 2005–06 

storms (fig. 4).

The missing inflow was judged to be largely surface 

water on the basis of TDS and hydrologic information, so the 

water temperature and water quality of the distributed tributary 

inflows were estimated as 90 percent surface water and 

10 percent ground water. Water temperature and water quality 

for the surface water component of the distributed tributaries 

were estimated to be the same as the water temperature and 

water quality of the major tributary for each branch. Ground 

water temperature was estimated from annual average air 

temperature at the lake. Ground water TDS concentrations 

were estimated by examining data from nearby ground water 

wells and the results of several preliminary model runs. 

Ground water suspended sediment concentrations were set to 

zero. 

Water Temperature

Reservoir water temperature patterns are controlled by 

factors such as the temperature of inflows, the amount of 

outflow, circulation in the lake, heat exchange at the air-water 

and sediment-water interfaces, solar radiation, light extinction, 

and mixing by wind. Detroit Lake typically is isothermal and 

cold at the beginning of the year (fig. 5). In spring, the surface 

begins to warm, and by summer a thermocline develops, 

separating warmer, less dense surface water (epilimnion) 

from cooler, denser, bottom waters (hypolimnion). The 

thermocline progressively deepens through the summer; this is 

an important influence on lake circulation through the summer 

season. In autumn, the water surface cools, lessening the 

 Modeling Hydrodynamics, Water Temperature, and Suspended Sediment in Detroit Lake, Oregon
density differences and allowing vertical mixing (“turnover”) 

to occur. The lake usually is in an isothermal state by the end 

of the calendar year.

In Detroit Lake, this seasonal pattern in water 

temperature repeats on an annual basis and was consistent in 

the modeled time periods (figs. 6, 7, and 8). Despite differing 

locations and water depths, temperature patterns were similar 

for all profile sites in the lake. The consistency of the vertical 

temperature profiles year-to-year and site-to-site within 

the lake demonstrates the importance of density patterns in 

creating a vertical structure within the lake. Temperature is 

the most important factor influencing water density in Detroit 

Lake, and, therefore, is among the most important factors in 

determining its circulation patterns. 

Wind also is important in creating a well-mixed layer 

near the lake surface. The stronger the wind, the deeper is the 

mixed layer. Several of the profiles in figures 6 and 7 show 

this effect. The profiles on June 19, 2003, for example, show 

a well-mixed layer 5 or more meters deep, more so near the 

dam, where the winds typically are stronger. Such spatial 

differences in wind speed were not provided by the model’s 

inputs, so the model was unable to capture such subtleties. 

Overall, however, the model captured the spatial and temporal 

patterns in the lake’s water temperature and its vertical 

structure.

Surface waters showed the greatest seasonal variation 

in temperature and the warmest summer temperatures, while 

the deepest waters of Detroit Lake remained cold through the 

summer (fig. 9). As water depth increased, the timing of the 

seasonal maximum water temperature shifted to later in the 

year, from early August near the surface to early October at 

40 m. Measured temperatures at 9–40 m depth show larger 

daily variations than those at the surface or near the bottom. 

This is likely due to those thermistors being stationed closer 

to the thermocline, the region where the temperature changes 

rapidly with depth, combined with the phenomenon of the 

lake’s internal waves caused by wind or short-term variations 

in water withdrawals, which causes the thermocline to move 

up and down. Temperatures near the surface have less daily 

variation owing to the depth of the mixed layer, but have a 

more chaotic signal that is tied to patterns in the wind, creating 

some of the short-duration spikes in these data.

Figure 4. Measured and modeled forebay water-surface elevations, Detroit Lake, Oregon, calendar years 2002 and 2003, and the 

period between December 1, 2005, and February 1, 2006.

OR19-0104_Fig04

Measured

ELEVATION, IN METERS

Model

ABOVE SEA LEVEL

DEC 1 FEB 1

440

460

480

JAN 1 APR 1 JULY 1

2002 2003 2005–2006

OCT 1 JAN 1 APR 1 JULY 1 OCT 1 JAN 1

Figure 5. Modeled water temperature profiles in Detroit Lake, Oregon, near the dam as a function of time during 2003.

11

19

23

27

7

3

15

Temperature, 

in degrees 

Celsius

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

2003

ELEVATION, IN METERS

371

400

450

477.3

Centerline elevation of dam’s penstocks

Model Development 
OR19-0104_Fig06a

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0 8 16 24 0 8

WATER TEMPERATURE, IN DEGREES CELSIUS

DEPTH, IN METERS

16 24 0 8 16 24

2002 KINNEY BLOWOUT MONGOLD

April 25

May 16

June 12

June 26

July 18

August 6

Modeled

Measured

Figure 6. Measured water temperature profiles at three locations in Detroit Lake, Oregon, compared to modeled water temperature at 

the same location and time in 2002. Model output extends to the bottom of the lake at each location.

10 Modeling Hydrodynamics, Water Temperature, and Suspended Sediment in Detroit Lake, Oregon
OR19-0104_Fig06b

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0 8 16 24 0 8

WATER TEMPERATURE, IN DEGREES CELSIUS

DEPTH, IN METERS

16 24 0 8 16 24

2002 KINNEY BLOWOUT MONGOLD

August 28

September 18

October 8

October 30

November 20

December 11

Modeled

Measured

Figure 6.—Continued.

Model Development 11
OR19-0104_Fig07a

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

DEPTH, IN METERS

0 8 16 24 0 8

WATER TEMPERATURE, IN DEGREES CELSIUS

16 24 0 8 16 24

2003 KINNEY BLOWOUT MONGOLD

January 8

January 28

February 6

March 5

March 27

April 17

May 8

Modeled

Measured

Figure 7. Measured water temperatures profiles at three locations in Detroit Lake, Oregon, compared to modeled water temperature at 

the same location and time in 2003. Model output extends to the bottom of the lake at each location.

12 Modeling Hydrodynamics, Water Temperature, and Suspended Sediment in Detroit Lake, Oregon
OR19-0104_Fig07b

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

DEPTH, IN METERS

0 8 16 24 0 8

WATER TEMPERATURE, IN DEGREES CELSIUS

16 24 0 8 16 24

2003 KINNEY BLOWOUT MONGOLD

May 28

June 19

July 10

July 30

August 21

September 10

October 9

Modeled

Measured

Figure 7.—Continued.

Model Development 13
OR19-0104_Fig08

0

40

80

120

0

40

80

120

DEPTH, IN METERS

DEPTH, IN METERS

WATER TEMPERATURE, IN DEGREES CELSIUS

WATER TEMPERATURE, IN DEGREES CELSIUS

0 8 16 24 0 8 16 24

0 8 16 24

2006 KINNEY BLOWOUT MONGOLD

January 13

North

South

Modeled

Measured

Figure 8. Measured water temperature profiles at four locations in Detroit Lake, Oregon, compared to modeled water temperature at 

the same location and time in 2006. Model output extends to the bottom of the lake at each location.

14  Modeling Hydrodynamics, Water Temperature, and Suspended Sediment in Detroit Lake, Oregon
OR19-0104_Fig09 WATER TEMPERATURE, IN DEGREES CELSIUS

MAY JUNE JULY AUG SEPT OCT

15 1 15 1 15 1 15 1 15 1 15

10

15

20

25

5

10

15

20

25

5

5

5

MAY JUNE JULY

2003

AUG SEPT OCT

15 1 15 1 15 1 15 1 15 1 15

MAY JUNE JULY AUG SEPT OCT

15 1 15 1 15 1 15 1 15 1 15

10

15

20

25

10

15

20

25

1 meter 3 meters 6 meters

9 meters 13 meters 19 meters

25 meters 31 meters 40 meters

50 meters 60 meters 80 meters

Measured

Modeled

Figure 9. Measured water temperatures from a string of thermistors suspended from the log boom in Detroit Lake, Oregon, compared 

to modeled water temperature at the same depth and time in 2003. The depth of each thermistor is noted on each graph.

Model Development 15
Measured, North Santiam at Niagara

Modeled, reservoir outflow

JAN MAR MAY JULY

2003

FEB APR JUNE AUG SEPT OCT NOV DEC

0

2

4

6

8

10

12

14

16

18

WATER TEMPERATURE, IN DEGREES CELSIUS

Figure 10. Modeled water temperatures in the Detroit Lake, Oregon, reservoir outflow compared to measured water temperature in 

the North Santiam River at Niagara, 6 km downstream of the reservoir outflow in 2003. 

The reservoir, with a relatively low-elevation outlet, 

released cold water through the summer (fig. 10). The heat 

that was stored in the upper part of the water column during 

summer was discharged later in the year when the reservoir 

was drawn down for flood control purposes. Consequently, 

outflow water temperatures were coolest in winter and spring, 

stayed cool through summer, and were warmest in autumn. 

The difference in temperature between the modeled reservoir 

outflow and the measured temperature on the North Santiam 

River 6 km downstream (at Niagara) was due in part to airwater heat exchange between the two locations—warming 

in summer and cooling in autumn. In addition, several small 

tributaries that enter the river between the reservoir outflow 

and the measuring location on the North Santiam River at 

Niagara might contribute to the temperature difference in 

figure 10.

Goodness-of-fit statistics were calculated between 

measured data and model output at the same location and 

time. For water temperature profiles in the lake, comparing 

modeled and measured water temperatures for the three time 

periods (2002, 2003, 2005–06) produced ME between -0.02

and -0.48oC, MAE between 0.48 and 0.58oC, and RMSE 

between 0.51 and 0.76oC (table 3). For the thermistor string 

near the dam in 2003, comparing modeled and measured water 

temperatures for all 23 depths produced a ME of 0.24oC, a 

MAE of 0.72oC, and a RMSE of 0.99oC. Sources of error in 

simulating water temperature include estimating inflow water 

temperatures for Kinney and Box Canyon Creeks as well as 

the ungaged (distributed) tributaries for all simulations, and 

estimating inflow water temperatures for French Creek for 

the 2005–06 storm simulations. In addition, measured data 

showed that light extinction coefficients were elevated in 

summer coincident with algal blooms. The model, however, 

did not include algae, and therefore those higher summer light 

extinctions due to algal activity were not simulated. Despite 

these sources of error, the goodness-of-fit statistics indicate 

very good performance by the model in capturing temperature 

patterns in the lake. Previous CE-QUAl-W2 models 

have demonstrated the capability of simulating reservoir 

temperatures to within 1.0oC (MAE) (Cole and Wells, 2002). 

Error greater than that amount is indicative of problems 

either with the model or the data; MAE of less than 1.0oC has 

become a benchmark for a well-calibrated CE-QUAL-W2 

model.

Total Dissolved Solids

The concentration of total dissolved solids (TDS) 

represents the sum of all dissolved constituents in water. 

TDS was included in the Detroit Lake model primarily to 

more accurately model suspended sediment, because TDS 

contributes to density gradients in a reservoir. TDS also 

provides information on lake water quality. CE-QUAL-W2 

considers TDS to be conservative (nonreactive), meaning 

that its concentration is affected only by inputs, outputs, 

and hydrodynamic processes, not by chemical or biological 

processes. Some of the constituents that make up TDS, 

however, may not be completely conservative. For instance, 

nutrients may be taken up or excreted by algae, dissolved 

constituents may precipitate as solids, or solids may dissolve 

from suspended or bottom sediments. In any case, available 

data were insufficient to model each dissolved constituent 

individually in this system.

16  Modeling Hydrodynamics, Water Temperature, and Suspended Sediment in Detroit Lake, Oregon
Table 3. Detroit Lake model goodness-of-fit statistics for calendar years 

2002 and 2003 and a storm event in January 2006.

[Comparisons include profiles at three locations in the lake in 2002 and 2003, and at four 

locations in 2006. Abbreviations: °C, degree Celsius; mg/L, milligram per liter; μS/cm, 

microsiemens per centimeter]

 Year 

2002

Year 

2003

January 

2006

Number of profiles 36 42 4

Mean Error (ME)

Temperature (°C) -0.02 -0.34 -0.48

Specific conductance (μS/cm) 1.49 1.32 -0.15

Suspended sediment (mg/L) from turbidity -0.24 -0.25 0.17

Suspended sediment (mg/L) -0.61 -0.45 -1.68

Mean Absolute Error (MAE)

Temperature (°C) 0.52 0.58 0.48

Specific conductance (μS/cm) 2.11 1.74 1.31

Suspended sediment (mg/L) from turbidity 0.55 0.43 3.06

Suspended sediment (mg/L) 0.91 0.80 3.34

Root Mean Square Error (RMSE)

Temperature (°C) 0.69 0.76 0.51

Specific conductance (μS/cm) 2.42 2.55 3.13

Suspended sediment (mg/L) from turbidity 0.73 0.68 4.28

Suspended sediment (mg/L) 1.16 1.04 3.92

TDS concentrations in Detroit Lake were fairly homogeneous 

in winter (fig. 11). Inflow waters in spring had lower dissolved solids 

concentrations compared to the lake water, and decreased the TDS 

concentration throughout the lake. Through summer and autumn, the 

TDS concentrations in the inflows increased. At that time of year, 

temperature stratification was present in the reservoir, and the higher 

concentration inflow waters were not mixed into the colder, denser, 

hypolimnetic water. Later in the year, when the lake turned over, the 

higher TDS in the epilimnion mixed into the entire lake.

This seasonal cycle in TDS was similar in all modeled time 

periods (shown as specific conductance in figs. 12, 13, and 14). There 

were some differences between sampling sites 

in the lake. For instance, the most upstream site, 

Mongold, showed the greatest effect from the 

tributary inflows. At that location, the plume of 

inflow water generally was at depths of 15–40 

m. These influent plumes that enter the lake at 

specific depths according to their density are 

important in determining circulation patterns in 

the regions of these inflows.

Water released from the reservoir outflow 

reflects the TDS seasonal cycle in the lake, with 

lowest values in spring and highest values in late 

autumn and early winter (reported as specific 

conductance in fig. 15). The overall trends of 

measured and modeled specific conductance 

downstream of the dam compare well, despite 

the fact that measured specific conductance 

on the North Santiam River at Niagara is 6 km 

downstream of the modeled reservoir outflow. 

The measured data were less smooth compared 

to the modeled outflow. Part of this difference is 

due to the entrance of several small tributaries 

between Detroit Dam and Niagara, and part of the 

difference is due to dam operation. For instance, at 

Niagara in spring, two short periods occur where 

the measured specific conductance decreased to 

about 25 μS/cm. These correspond to periods 

when no water was released from Detroit Dam, 

and the small tributaries between Detroit Dam 

and Niagara appeared to have lower specific 

conductance values than the reservoir outflow 

at that time of year. Note that the comparison 

of specific conductance data downstream of 

Detroit Dam is better than the same comparison 

for temperature (fig. 10). This primarily is due 

to the largely conservative nature of specific 

conductance; unlike water temperature, it is not 

affected by exchange processes across the airwater interface.

17

25

29

33

21

Total dissolved 

solids, in

milligrams

per liter

ELEVATION, IN METERS

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

2003

371

400

450

477.3

Centerline elevation 

of dam’s penstocks

Figure 11. Modeled total dissolved solids profiles in Detroit Lake, Oregon, near the dam as a function of time during 2003. 

Model Development 17
OR19-0104_Fig12a

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

DEPTH, IN METERS

SPECIFIC CONDUCTANCE, IN MICROSIEMENS PER CENTIMETER

20 30 40 50 20 30 40 50 20 30 40 50

2002 KINNEY BLOWOUT MONGOLD

April 25 

May 16

June 12

June 26

July 18

August 6

Modeled

Measured

Figure 12. Measured specific conductance profiles at three locations in Detroit Lake, Oregon, compared to modeled specific 

conductance (derived from total dissolved solids) at the same location and time in 2002. Model output extends to the bottom of the lake 

at each site.

18  Modeling Hydrodynamics, Water Temperature, and Suspended Sediment in Detroit Lake, Oregon
OR19-0104_Fig12b

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

DEPTH, IN METERS

SPECIFIC CONDUCTANCE, IN MICROSIEMENS PER CENTIMETER

20 30 40 50 20 30 40 50 20 30 40 50

2002 KINNEY BLOWOUT MONGOLD

August 28

September 18

October 8

October 30

November 20

December 11

Modeled

Measured

Figure 12.—Continued.

Model Development 19
OR19-0104_Fig13a

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

DEPTH, IN METERS

SPECIFIC CONDUCTANCE, IN MICROSIEMENS PER CENTIMETER

20 30 40 50 20 30 40 50 20 30 40 50

2003 KINNEY BLOWOUT MONGOLD

January 8

January 28

February 6

March 5

March 27

April 17

May 8

Modeled

Measured

Figure 13. Measured specific conductance profiles at three locations in Detroit Lake, Oregon, compared to modeled specific 

conductance (derived from total dissolved solids) at the same location and time in 2003. Model output extends to the bottom of the lake 

at each site.

20 Modeling Hydrodynamics, Water Temperature, and Suspended Sediment in Detroit Lake, Oregon
OR19-0104_Fig13b

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

DEPTH, IN METERS

SPECIFIC CONDUCTANCE, IN MICROSIEMENS PER CENTIMETER

20 30 40 50 20 30 40 50 20 30 40 50

2003 KINNEY BLOWOUT MONGOLD

May 28

June 19

July 10

July 30

August 21

September 10

October 9

Modeled

Measured

Figure 13.—Continued.

Model Development 21
OR19-0104_Fig14

0

40

80

120

0

40

80

120

DEPTH, IN METERS

SPECIFIC CONDUCTANCE, IN

MICROSIEMENS PER CENTIMETER

SPECIFIC CONDUCTANCE, IN MICROSIEMENS PER CENTIMETER

20 30 40 50

20 30 40 50 20 30 40 50

2006 KINNEY BLOWOUT MONGOLD

January 13

North

South

Modeled

Measured

Measured, North Santiam at Niagara

Modeled, reservoir outflow

20

25

30

35

40

45

50

55

2003

SPECIFIC CONDUCTANCE, IN MICROSIEMENS PER CENTIMETER

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

Figure 14. Measured specific conductance profiles at four locations in Detroit Lake, Oregon, compared to modeled specific 

conductance (derived from total dissolved solids) at the same location and time in 2006. Model output extends to the bottom of the lake 

at each site.

Figure 15. Modeled specific conductance (converted from modeled total dissolved solids) in the Detroit Lake, Oregon, reservoir 

outflow compared to measured specific conductance in the North Santiam River at Niagara, 6 km downstream, in 2003.

22 Modeling Hydrodynamics, Water Temperature, and Suspended Sediment in Detroit Lake, Oregon
Calculation of goodness-of-fit statistics for measured 

specific conductance and specific conductance converted 

from modeled TDS for the three modeled time periods 

(2002, 2003, 2005–06) produced MEs between -0.15 and 

1.49 μS/cm, MAEs between 1.31 and 2.11 μS/cm, and 

RMSEs between 2.42 and 3.13 μS/cm (table 3). Sources of 

error include the estimation of TDS in ungaged inflows and 

any nonconservative reactions that affect dissolved solids. 

Overall, though, errors in simulating specific conductance are 

approximately 5 to 10 percent of measured values in the lake 

(range of about 27 to 47 μS/cm).

Suspended Sediment

Sediment suspended in the water column is a natural 

component of lakes and rivers. Excessive concentrations of 

suspended sediment, however, can impair certain uses. For 

example, high sediment loads can bury spawning gravels and 

reduce light penetration into the water column, making it 

more difficult for fish to find prey. Sediment in water used for 

drinking water supply can cause taste and odor problems and 

impair the efficiency and operation of treatment systems. High 

concentrations of suspended sediment that settle and deposit in 

a reservoir can reduce the volume available for water storage. 

Suspended sediment also can contribute surfaces for ion 

exchange and adsorption between dissolved and particulate 

phases of various constituents (Horne and Goldman, 

1994), and thus act as a storage and transport medium for 

nutrients, organic contaminants, and trace metals. Suspended 

sediment concentrations are controlled by factors such as 

hydrodynamics, sources, density, and settling rates. 

In the model calibration process, the settling rates for the 

two simulated sediment-size groups were adjusted until the 

model results and the measured data compared well. In the 

final Detroit Lake model, suspended sand and silt, particles 

larger than 2 μm, was given a settling rate of 21.0 m/d, and 

suspended clay, particles smaller than 2 μm, was given a 

settling rate of 0.6 m/d. For comparison, Stokes’ Law may be 

used to estimate the settling velocities of spherical particles in 

water (Lide, 2006):

v

g d p w = ⋅ ⋅ −

⋅

2

18

( ) ρ ρ

μ , (4)

where:

ν is setting velocity, in cm/s,

g is gravitational acceleration constant, 981 cm/s2

,

d is particle diameter, in cm,

ρp is particle density, in g/cm3

,

ρw is water density, in g/cm3

, 0.99823 at 20oC, and

μ is viscosity of water [0.01002 (g/cm)/s] at 20oC.

 The Stokes’ Law settling rates are idealized, assuming 

spherical particles and homogeneous particle density, particle 

size, and water temperature. With a particle density of 

2.7 g/cm3, a typical value for silicate minerals including clays 

and quartz (sand), a particle with a diameter of 2 μm would 

have an ideal settling velocity in pure water of 0.00037 cm/s, 

or 0.32 m/d at 20°C. Larger particles with a 62 μm diameter 

would settle at 307 m/d at 20°C, and smaller particles of 1 μm 

would settle at 0.08 m/d at 20°C. Under colder conditions, 

the density of water would change only slightly, whereas the 

viscosity of water would increase, but only by a factor of 1.6 

from 20°C to 4°C. In nature, these idealized conditions do not 

hold, so rates calculated with Stokes’ Law are not expected 

to be exactly the same as rates in Detroit Lake. However, 

comparing modeled rates for Detroit Lake to ideal Stokes’ 

Law rates is a useful comparison, and both are fairly similar.

In the modeled time periods, most of the suspended 

sediment entered the reservoir during winter and spring storms 

(fig. 16). The suspended sand and silt settled relatively quickly, 

whereas the clay-sized sediment remained in suspension for 

longer periods. In summer and autumn, suspended sediment 

concentrations were relatively low (<0.5 mg/L) in the lake.

This pattern of sediment input and settling was similar 

in all modeled time periods (figs. 17, 18, and 19). There was 

some variability between different profile locations in the 

lake, particularly during storms. Heterogeneity of suspended 

sediment concentrations is expected in the lake, with 

variations in inputs between tributaries, and different distances 

from tributary inputs, combined with settling processes in the 

reservoir.

Model Development 23
OR19-0104_Fig16

0.10

10

100

1000

0.01

0.001

1

Suspended

sediment, in

milligrams

per liter

ELEVATION, IN METERS 371

400

450

477.3

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

2003

371

400

450

477.3

Suspended sand and 

silt concentrations

Suspended clay 

concentrations

A

B

Centerline elevation of dam’s penstocks

Centerline elevation of dam’s penstocks

Figure 16. Modeled profiles of suspended sediment concentrations in Detroit Lake, Oregon, near the dam as a function of time 

during 2003.

For some of the lake profiles in summer, suspended 

sediment concentrations were elevated at the lake surface, 

but the model did not simulate these elevated concentrations. 

This was due to the fact that algae blooms occur in the lake; 

they contribute to measurements of suspended sediment and 

turbidity, but the model does not simulate algae. Evidence 

for algal blooms in Detroit Lake during the summers of 2002 

and 2003 was based in part on concurrent dissolved oxygen 

and pH data from the vertical profiles. Elevated surface pH, 

dissolved oxygen supersaturation, and elevated turbidity due 

to an algal bloom occurred on June 12, 2002, for example, 

(fig. 20). Algae were not simulated by the Detroit Lake model 

due to the lack of data necessary to model algae; simulating 

algal succession in Detroit Lake was beyond the scope of this 

project. Sampling of algae in Detroit Lake at the main lake 

sampling sites between June 19, 2003, and September 10, 

2003, corroborated the chemical evidence of summertime 

24  Modeling Hydrodynamics, Water Temperature, and Suspended Sediment in Detroit Lake, Oregon
algal blooms. In those samplings, the dominant algal species 

were Rhodomonas minuta, Chromulina sp., Asterionella 

formosa, Anabaena flos-aquae, Cryptomonas erosa, Synedra 

radians, and Fragilaria crotonensis, in order of relative 

density. Additional information and data from these samples is 

available online (see section, “Supplemental Material”).

The highest suspended sediment concentrations in 

the outflow occurred during winter and spring, with low 

concentrations during summer; this reflects the patterns of 

suspended sediment concentrations in the lake (shown as 

turbidity in fig. 21A). Turbidity data from the North Santiam 

River at Niagara were more variable than those in the reservoir 

outflow, owing to the fact that the reservoir buffers the effects 

of storm flows, and the fact that several undammed tributaries 

enter the river between Detroit Dam and the monitor at 

Niagara. Suspended sand- and silt-sized sediment typically 

was released from the lake only during storm events, whereas 

varying amounts of suspended clay were released throughout 

most of the year (fig. 21B).

Comparing measured and modeled total suspended 

sediment concentrations for 2002 and 2003 produced MEs 

of -0.61 and -0.45 mg/L, MAEs of 0.91 and 0.80 mg/L, 

and RMSEs of 1.16 and 1.04 mg/L, respectively (table 3). 

Calculating goodness-of-fit statistics for the January 2006 

profiles produced an ME of -1.68 mg/L, MAE of 

3.34 mg/L, and RMSE of 3.92 mg/L (table 3). The highest 

error occurred during the storm event, when inflows were 

large, and the estimated suspended sediment loads from 

ungaged inflows were most uncertain. Goodness-of-fit 

statistics using the measured turbidity profiles converted 

to suspended sediment, rather than the sampled suspended 

sediment concentrations, were slightly better (table 3). 

Measured and modeled suspended sediment concentrations 

on days, locations, and depths where algae blooms occurred 

were not included in the error statistic calculations. 

Sources of error include the estimation of inflows and the 

representation of suspended sediment with only two size 

groups. The version of CE-QUAL-W2 used for the Detroit 

Lake model also did not include algorithms to quantify the 

effects of sediment resuspension and scour. In the model, 

the mass of deposited sediment cannot reenter the water 

column or be moved upstream or downstream. More recent 

versions of CE-QUAL-W2 do include an algorithm for wind 

resuspension of sediment, but the effects of scour are not yet 

included in any version of the model.

Model Development 25
OR19-0104_Fig17a

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

SUSPENDED SEDIMENT, IN MILLIGRAMS PER LITER

DEPTH, IN METERS

0 2 4 6 8 0 2 4 6 8 0 2 4 6 8

2002 KINNEY BLOWOUT MONGOLD

April 25 

May 16

June 12

June 26

July 18

August 6

Suspended sediment

Modeled

Measured

Measured, from turbidity

Figure 17. Total suspended sediment concentration profiles, both measured and calculated from turbidity, at three locations in Detroit 

Lake, Oregon, compared to modeled total suspended sediment concentration at the same location and time in 2002. Model output 

extends to the bottom of the lake at each site. 

26  Modeling Hydrodynamics, Water Temperature, and Suspended Sediment in Detroit Lake, Oregon
OR19-0104_Fig17b

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

SUSPENDED SEDIMENT, IN MILLIGRAMS PER LITER

DEPTH, IN METERS

0 2 4 6 8 0 2 4 6 8 0 2 4 6 8

2002 KINNEY BLOWOUT MONGOLD

August 28

September 18

October 8

October 30

November 20

December 11

Suspended sediment

Modeled

Measured

Measured, from turbidity

Figure 17.—Continued.

Model Development 27
OR19-0104_Fig18a

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

SUSPENDED SEDIMENT, IN MILLIGRAMS PER LITER

DEPTH, IN METERS

0 2 4 6 8 0 2 4 6 8 0 2 4 6 8

2003 KINNEY BLOWOUT MONGOLD

January 8

January 28

February 6

March 5

March 27

April 17

May 8

Suspended sediment

Modeled

Measured

Measured, from turbidity

Figure 18. Total suspended sediment concentration profiles, both measured and calculated from turbidity, at three locations in 

Detroit Lake, Oregon, compared to modeled total suspended sediment concentration at the same location and time in 2003. Model 

output extends to the bottom of the lake at each site.

28  Modeling Hydrodynamics, Water Temperature, and Suspended Sediment in Detroit Lake, Oregon
OR19-0104_Fig18b

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

0

40

80

120

SUSPENDED SEDIMENT, IN MILLIGRAMS PER LITER

DEPTH, IN METERS

0 2 4 6 8 0 2 4 6 8 0 2 4 6 8

2003 KINNEY BLOWOUT MONGOLD

May 28

June 19

July 10

July 30

September 10

October 9

Suspended sediment

Modeled

Measured

Measured, from turbidity

Figure 18.—Continued.

Model Development 29
OR19-0104_Fig19

0

40

80

120

0

40

80

120

SUSPENDED SEDIMENT, IN MILLIGRAMS PER LITER

SUSPENDED SEDIMENT,

IN MILLIGRAMS PER LITER

DEPTH, IN METERS

DEPTH, IN METERS

0 10 20 30 40

0 10 20 30 40 0 10 20 30 40

2006 KINNEY BLOWOUT MONGOLD

January 13

North

South

Suspended sediment

Modeled

Measured

Measured, from turbidity

Figure 19. Total suspended sediment concentration profiles, both measured and calculated from turbidity, at four locations in Detroit 

Lake, Oregon, compared to modeled total suspended sediment concentration at the same location and time in 2006. Model output 

extends to the bottom of the lake at each site.

0 1 2 3 4 5 6

TURBIDITY, IN FNU

80 90 100 110 120

DISSOLVED OXYGEN, 

IN PERCENT SATURATION

60

50

40

30

20

10

0

7 8 9 10

DEPTH, IN METERS

pH

Figure 20. Chemical (pH and dissolved oxygen) and physical 

(surface turbidity) evidence of an algal bloom at the Blowout 

lake monitoring site, Detroit Lake, Oregon, June 12, 2002.

30 Modeling Hydrodynamics, Water Temperature, and Suspended Sediment in Detroit Lake, Oregon
OR19-0104_Fig21

Measured turbidity

Modeled reservoir outflow

Modeled suspended sand and silt

Modeled suspended clay

0

2

4

6

8

10

12

14

16

18

20

TURBIDITY, IN FORMAZIN NEPHELOMETRIC UNITS

JAN MAR MAY JULY

2003

FEB APR JUNE AUG SEPT OCT NOV DEC

0

2

4

6

8

10

12

14

TURBIDITY, IN FORMAZIN NEPHELOMETRIC UNITS

A.

B.

Figure 21. Modeled total suspended sediment concentration in reservoir outflow, converted to turbidity and modeled 

distribution of two sediment size groups, Detroit Lake, Oregon, 2003: (A) compared to measured turbidity in the North Santiam 

River at Niagara, 6 km downstream, in 2003 and (B) showing the distribution between the two sediment size groups. 

Model Development 31
Model Sensitivity

The model’s wind sheltering coefficient, suspended 

sediment settling rates, suspended sediment light extinction 

factor, and bottom sediment temperature were all individually 

increased and decreased by 20 percent in separate model runs 

to determine the effect of changing that parameter on the 

model output. The sensitivity of modeled water temperature, 

suspended sand and silt concentrations, and suspended clay 

concentrations to these parameters were examined in the lake 

and in the lake outflow for 2003. In addition, a qualitative 

sense of model sensitivity was gained in the model calibration 

process.

Varying these model parameters by 20 percent did 

not have large effects on in-lake or outflow average water 

temperatures (table 4). Of the parameter group, only changes 

in the wind sheltering coefficient (which modifies wind speed) 

and the temperature of bottom sediments had any effect at all, 

and these effects were localized in the water column. Wind 

did affect the shape of the water temperature profile near 

the lake surface; higher winds led to more mixing, a deeper 

mixed surface layer, and less vertical variability in nearsurface water temperatures. A 20 percent change in bottom 

sediment temperature had only a small effect on lake water 

temperatures, and this effect was greatest for water near the 

bottom of the lake.

Varying the suspended sand and silt and suspended clay 

settling rates by 20 percent had a large effect on suspended 

sediment concentrations in the lake (table 4). Decreasing the 

suspended sediment settling rates (making sediment settle 

more slowly), as expected, led to increased average annual 

concentrations of suspended sediment in the lake and in 

the outflow. In contrast, increasing the suspended sediment 

settling rates (sediment settles faster) decreased suspended 

sediment concentrations both in the lake and the reservoir 

outflow. These effects were greatest for suspended sand and 

silt. Smaller effects on suspended sediment concentrations 

were caused by varying the wind sheltering coefficient and 

the bottom sediment temperature by 20 percent. Increasing 

the wind sheltering coefficient increases the wind shear at the 

lake’s surface and leads to more wind mixing, keeping the 

sediment suspended longer and leading to a small increase 

in the simulated suspended sediment concentration. Varying 

the light extinction factor for suspended sediment had no 

effect on suspended sediment concentrations in the lake. This 

light extinction factor is only relevant to the surface photic 

zone, a relatively small portion of the lake volume. TDS 

concentrations had no change in any of these sensitivity runs.

Table 4. Results from sensitivity testing showing the effect of changing a particular input parameter on annual average temperature, 

suspended sand and silt, and suspended clay in the whole lake and in the lake outflow for 2003.

Input Output

Parameter Percent 

change

WHOLE LAKE, percent change OUTFLOW, percent change

Temperature Suspended 

sand and silt

Suspended 

clay Temperature Suspended sand and silt

Suspended 

clay

Wind sheltering coefficient -20 -1 -3 -1 -1 +2 0

+20 +1 +5 +1 +1 -2 0

Temperature of bottom sediments -20 -1 0 0 -1 -3 0

+20 +1 0 0 +1 +6 0

Light extinction factor for 

suspended sediments

-20 0 0 0 0 0 0

+20 0 0 0 0 0 0

Suspended sediment settling rate -20 0 +33 +12 0 +65 +10

+20 0 -21 -10 0 -35 -8

32 Modeling Hydrodynamics, Water Temperature, and Suspended Sediment in Detroit Lake, Oregon
Model Applications

The calibrated Detroit Lake model was used to examine 

several scenarios. Results from the following applications are 

presented herein: 

An examination of the sediment entering and exiting 

the reservoir, including estimates of sediment trap 

efficiency and the volume of sediment deposited,

An investigation of the sources of sediment to the 

reservoir outflow, and

A demonstration of the effect of a hypothetical 

selective withdrawal device on water temperatures 

released from Detroit Dam.

Characteristics of Sediment Inflows, Outflows, 

and Deposits

Determining the amount of sediment that exits the 

reservoir and the amount of sediment that is retained by 

the reservoir is important in determining the depletion of 

reservoir storage, making decisions on reservoir operation, 

•

•

•

and assessing downstream effects. Reservoir sediment trap 

efficiency is defined as the percentage of sediment input 

retained by the lake. Methods such as the Brune ratio, 

calculated from ratios of reservoir capacity to annual water 

inflow, have been used to calculate this quantity (Brune, 

1953; Snyder and others, 2004). However, calculations that 

use a constant reservoir capacity or residence time are not 

recommended for reservoirs such as Detroit Lake that vary 

greatly in surface elevation and volume over the course of a 

year. That change in volume also changes the residence time 

and the corresponding amount of time available for suspended 

sediment to settle (Ambers, 2001). The calibrated Detroit Lake 

model keeps track of suspended sediment deposition, allowing 

trap efficiency to be calculated directly with the model. In 

calendar year 2002, the trap efficiency of Detroit Lake was 

calculated to be 93 percent, in 2003 it was calculated as 

90 percent, and during the 2005–06 storms, it was calculated 

as 94 percent (table 5). Because of residence time, the 

sediment that exits the reservoir in one year may have entered 

the reservoir in a previous year; similarly, suspended sediment 

that enters the reservoir in 2002 may not exit until a future 

year. Most of the suspended sediment that enters the lake is 

trapped; only 10 percent or less exited in the modeled time 

periods. 

Table 5. Modeled sand and silt, clay, and total sediment entering, exiting, and deposited in Detroit Lake for the three modeled time 

periods.

[Volumes are estimated assuming a sediment bulk density of 1.89 g/cm3. Sediment deposited in the reservoir is calculated by subtracting outflow from inflow, 

and is corrected by adding the difference between the initial and final suspended sediment mass in the lake water column. 1 metric ton = 1,000 kilograms]

Jan. 1 – Dec. 31, 2002 Jan. 1 – Dec. 31, 2003 Dec. 1, 2005 – Feb. 1, 2006

Sand/Silt Clay Total Sand/Silt Clay Total Sand/Silt Clay Total

Inflow sediment

Sediment mass (metric tons) 24,740 4,250 28,990 20,370 4,180 24,550 65,180 5,780 70,960

Sediment volume (cubic meters) 13,090 2,250 15,340 10,780 2,210 12,990 34,490 3,060 37,550

Outflow sediment

Sediment mass (metric tons) 190 1,990 2,180 170 2,190 2,360 690 3,720 4,410

Sediment volume (cubic meters) 100 1,050 1,150 90 1,160 1,250 360 1,970 2,330

Difference between initial and final (initial – final) suspended sediment in water column

Sediment mass (metric tons) -70 290 220 0 160 160 -60 -540 -600

Sediment volume (cubic meters) -40 150 110 0 80 80 -30 -290 -320

Sediment deposited in Detroit Lake

Sediment mass (metric tons) 24,480 2,550 27,030 20,200 2,150 22,350 64,430 1,520 65,950

Sediment volume (cubic meters) 12,950 1,350 14,300 10,690 1,130 11,820 34,100 800 34,900

Percent trapped 99 56 93 99 50 90 99 29 94

Percent exported 1 44 7 1 50 10 1 71 6

Model Applications 33
If sediment grains with a 2.7 g/cm3

 density are assumed 

to have a 30 percent pore space upon deposition, leading 

to sediment deposits with 1.89 g/cm3 dry bulk density, 

then approximately 14,300 m3 (11.6 acre-ft) of sediment 

was deposited in the lake in calendar year 2002, 11,820 m3

(9.6 acre-ft) in 2003, and 34,900 m3 (28.3 acre-ft) from 

December 1, 2005, to February 1, 2006. The mass of sediment 

entering and deposited in the reservoir in the 2-month period 

during the 2005–06 storms was more than double the mass 

of sediment deposited in the entire calendar years of either 

2002 or 2003, emphasizing the importance of storm flows to 

reservoir sediment budgets. These volumes of sediment are all 

less than 0.01 percent of Detroit Lake’s full pool volume of 

561 million m3 (455,000 acre-ft), indicating that Detroit Lake 

is not likely to fill up anytime soon. The actual density of the 

deposited sediment can vary depending on factors such as 

composition, age, and wetting and drying, which can lead to 

compaction (Vanoni, 1975).

The model results indicated that most of the sediment 

was deposited in the upper reaches of the reservoir and areas 

near major inflows (fig. 22). The velocity of the inflows, 

and their sediment carrying capacity, decreases substantially 

as they enter the pooled reservoir. The predicted deposition 

rates can be substantial during a large storm inflow. Areaaveraged deposition rates in the North Santiam arm of the 

lake during the 2005–06 storms, for example, were simulated 

to be as high as 20 kg/m2 for the 2-month simulation period 

(fig. 22). Assuming a sediment bulk density of 1.89 g/cm3, 

this deposition could have reached an average thickness of 

1.06 cm. This is an area-averaged value; some areas would 

have less deposition, and others would have more. Deposited 

sediment can be resuspended and redistributed during other 

storm events, particularly if the stage of the lake decreases 

enough to convert that area from a pooled reach to a riverine 

reach. The Detroit Lake model currently does not include 

Basemap modified from U.S. Geological Survey 

digital data (1:24,000). Projection: UTM, Zone 10, 

North American Datum 1927.

22

20

18

16

14

12

10

8

6

4

2

0

Sediment deposition, in kilograms 

per square meter

White areas within the lake 

boundary were not modeled

EXPLANATION

0

0 3 KILOMETERS

3 MILES

122°15' 10' 122°07'

44°41'

44°45'

122°15' 10' 122°07'

44°41'

44°45'

122°15' 10' 122°07'

44°41'

44°45'

January 1 - December 31, 2002 December 1 - February 1, 2006

January 1 - December 31, 2003

Detroit

Dam

Detroit

Dam

Detroit

Dam

 Piety

Island

 Piety

Island

 Piety

Island

Figure 22. Modeled spatial distribution of suspended sediment deposition in Detroit Lake, Oregon, for calendar years 2002, 2003, and 

the period between December 1, 2005 and February 1, 2006. The deposition plotted in these figures is output for each model segment 

and ranges from 0.6 to 20.2 kg/m2

.

34  Modeling Hydrodynamics, Water Temperature, and Suspended Sediment in Detroit Lake, Oregon
algorithms to fully simulate the effects of scour and sediment 

resuspension, which may be important processes that 

redistribute sediment further into the reservoir.

The calibrated model also was used to investigate the size 

of the sediment flowing into and exiting the reservoir. In 2002, 

suspended sand- and silt-sized sediment made up 85 percent 

of the inflow sediment mass. It made up 83 percent of the 

inflow mass in 2003, and 92 percent during the storm events 

between December 1, 2005, and February 1, 2006. In contrast, 

most of the sediment that exited the reservoir downstream was 

suspended clay. That clay-sized sediment made up 91 percent 

of the outflow mass of sediment in 2002, 93 percent of the 

outflow sediment mass in 2003, and 84 percent of the outflow 

sediment mass for the 2005–06 storms. Table 5 summarizes 

the masses of suspended sediment in the inflows and outflow, 

as well as the reservoir trap efficiencies, for each of the three 

modeled time periods.

Sources of Sediment to the Reservoir Outflow 

The calibrated model was used to examine the relative 

contribution of each of Detroit Lake’s tributaries to the 

suspended sediment in the reservoir outflow for 2003. Each 

suspended sand and silt and suspended clay group for each 

inflow, including the distributed tributaries (the small ungaged 

tributary groups), was modeled as a separate sediment group 

for this analysis. The settling rates for each group were the 

same as those in the calibrated model, so that the sediment 

behavior overall was unchanged. The only difference was 

the ability to track various sources of sediment through 

the system. In order to determine the initial distribution of 

sediment from various sediment sources in the reservoir 

to start the year, an entire year’s simulation was run with 

estimated initial conditions; then the distribution of sediment 

from various sources in the reservoir on the last day of the year 

was used to reinitialize the sediment distribution at the start of 

the year, before running the simulation a final time.

 The results from this scenario show that all inflows to 

Detroit Lake contributed to the suspended sediment in the 

reservoir outflow (fig. 23, table 6). The contributions were 

generally greatest from the North Santiam and Breitenbush 

Rivers, the largest tributaries, throughout the year. The 

contribution from the North Santiam River was unique in 

that it contributed suspended sediment to the outflow from 

September through November, whereas the other tributaries 

had ceased to deliver much sediment in that period. The North 

Santiam River is the only Detroit Lake tributary sourced in a 

glacial basin, and the reasons for the different characteristics 

of sediment in the headwaters of this river are still under 

investigation by the USGS.

Model results indicated that sediment that exited the 

reservoir in 2003 was mostly suspended clay (93 percent of 

the total mass). The largest contribution of this clay-sized 

sediment came from the North Santiam River, followed 

by Breitenbush River, Blowout Creek, the distributed 

Table 6. Fate of suspended sand and silt, and suspended clay from the major tributaries to Detroit Lake, Oregon, 2003.

[The small tributary group refers to the ungaged or distributed tributaries. Correction refers to the difference between initial and final (initial-final) suspended 

sediment mass in the lake water column. 1 metric ton = 1,000 kilograms]

Tributary Inflow 

(metric tons)

Outflow 

(metric tons)

Correction 

(metric tons)

Deposited 

(metric tons)

Percent

 trapped

Percent

exported

Suspended silt and clay

Box Canyon Creek 812 7 0 805 99 1

French Creek 349 1 0 348 100 0

Kinney Creek 1,040 33 0 1,007 97 3

Small tributary group 1,673 71 0 1,602 96 4

Blowout Creek 1,982 33 0 1,949 98 2

Breitenbush River 6,953 17 0 6,936 100 0

North Santiam River 7,560 3 0 7,557 100 0

Suspended clay

Box Canyon Creek 120 70 11 61 47 53

French Creek 175 86 7 96 53 47

Kinney Creek 154 123 4 35 22 78

Small tributary group 380 229 -14 137 37 63

Blowout Creek 427 255 15 187 42 58

Breitenbush River 1,073 541 57 589 52 48

North Santiam River 1,849 886 84 1,047 54 46

Model Applications 35
tributaries (small ungaged tributaries), Kinney, French, and 

Box Canyon Creeks. The minor amount of suspended sand 

and silt discharged from the reservoir came predominantly 

from Kinney Creek, Blowout Creek, and the ungaged small 

tributaries. Tributaries that enter farther upstream contributed 

less suspended sand and silt compared to those that enter 

closer to the dam, probably because the suspended sand and 

silt settles more rapidly. Table 6 quantifies each tributary’s 

export efficiency for both suspended sand and silt and 

suspended clay. The North Santiam River, entering about 

8 km upstream, contributed no suspended sand and silt to 

the reservoir outflow. The distributed tributaries represent an 

estimate of sediment associated with the ungaged fraction of 

inflow to the reservoir. The model apportions the distributed 

tributaries’ inflows with their associated sediment to every 

segment in the model, including those segments closest to the 

OR19-0104_Fig23

Blowout Creek

Box Canyon Creek

Breitenbush River

French Creek

Kinney Creek

North Santiam River

Small tributary group

JAN MAR MAY JULY

2003

FEB APR JUNE AUG SEPT OCT NOV DEC

0.0

0.5

1.0

1.5

2.0

2.5

3.0

TOTAL SUSPENDED SEDIMENT IN OUTFLOW, IN MILLIGRAMS PER LITER

 A.

B.

Sand/Silt

Clay

500

0

1000

1500

2000

2500

ANNUAL SEDIMENT MASS IN OUTFLOW, IN METRIC TONS

2003

Figure 23. Modeled sources of total sediment in reservoir outflow of Detroit Lake during 2003 (A), and annual modeled sum of 

sediment mass in the Detroit Lake outflow in 2003, showing the difference between the suspended sand and silt and suspended clay 

sediment groups, and showing the modeled sources (B) of the sediment in each group. These values also are presented in table 6. A 

metric ton is equal to 1,000 kg or 2,205 pounds.

dam. In the model, sediment introduced into the reservoir near 

the dam does not have much time to settle before it reaches the 

dam outflow. This is the reason that the distributed tributary 

represents a relatively large portion of suspended sediment 

in the reservoir outflow. Some small ungaged inflows do 

enter Detroit Lake near the dam (fig. 1), and they are likely to 

contribute disproportionately to the coarse sediment load in 

the reservoir outflow.

Effect of Dam on Release Water Temperature

The water temperature in the North Santiam River at the 

location of the dam, without the influence of the reservoir, 

was estimated by calculating a volume-weighted mix of 

Detroit Lake model inflows for 2003 (fig. 24). This is only 

an estimate, as it does not include warming or cooling that 

36  Modeling Hydrodynamics, Water Temperature, and Suspended Sediment in Detroit Lake, Oregon
might occur between each gage location and the dam. For 

the 2003 inflow mix, maximum water temperatures occurred 

in July, whereas the modeled reservoir outflow reached 

annual maximum temperatures later in the year, in early 

October. The presence of the reservoir, with its midlevel lake 

outlet, produced cooler temperatures in summer and warmer 

temperatures in autumn compared to the river in the absence 

of the reservoir. This effect has been observed for many other 

storage reservoirs in which the outflow draws water from 

relatively deep in the water column (for instance Hagg Lake, 

Figure 24. (A) Maximum water temperature standard for the North Santiam River, Oregon, downstream of Big Cliff and Detroit 

Dams, an estimate of the water temperatures in the absence of the dams calculated using a volume-weighted mix of reservoir 

inflows for 2003, and modeled water temperatures of the water released from Detroit Dam and (B) smoothed water temperature 

of the volume-weighted mix of the reservoir inflows, used as a temperature target for the selective withdrawal simulation, along 

with the modeled reservoir release temperatures for that scenario. The selective withdrawal scenario was able to achieve the 

temperature target for much of the year, but the lake did not have enough cool water to meet that target in early spring or late 

autumn. The modeled release temperature did, however, remain less than the temperature standard for the entire year.

Temperature standard

Temperature standard

Reservoir inflow, volume-weighted mix

Reservoir outflow, model

Reservoir inflow, smoothed

Reservoir outflow, modeled

with selective withdrawal

Lake no longer 

cold enough 

to meet target

0

2

4

6

8

10

12

14

16

18

JAN MAR MAY JULY

2003

FEB APR JUNE AUG SEPT OCT NOV DEC

0

2

4

6

8

10

12

14

16

18

WATER TEMPERATURE, IN DEGREES CELSIUS

A.

B.

Sullivan and Rounds, 2006). Besides differences in seasonal 

temperature patterns, the reservoir outflow also had smaller 

24-hour temperature variations compared to the inflow-mix.

In addition to the fact that the reservoir outflow can 

exceed Oregon’s maximum water temperature criterion in 

autumn, the cool summer temperatures of the outflow also 

may be undesirable (Larson, 2000). In an attempt to address 

this issue, the USACE experimented with mixing the cool 

waters released from Detroit Dam’s power-generating outlet 

with warmer surface waters released from the spillway in 

Model Applications 37
June and July of 1979. Further study by USACE led to the 

recommendation that a selective withdrawal tower be installed 

as part of Detroit Dam (Larson, 2000 referring to two USACE 

reports). This type of device would blend water from different 

levels in the water column in order to release water with 

a more natural seasonal temperature pattern. The USACE 

recently completed a selective withdrawal tower at Cougar 

Reservoir, another large storage reservoir in the Willamette 

Basin, to address downstream temperature issues (Resource 

Management Associates, 2003).

The calibrated Detroit Lake model was used to assess the 

degree to which a more natural seasonal temperature pattern 

could be achieved downstream of the dam by using such a 

device. The hypothetical selective withdrawal device was 

set up to withdraw water from the penstocks at their current 

elevation, and from a sliding gate outlet that could be adjusted 

once per day vertically through the water column to select 

an elevation, with a corresponding water temperature, that 

could be blended into the penstocks to meet a temperature 

target. The elevation of the sliding-gate outlet was determined 

automatically by the model in an attempt to match a userspecified downstream temperature target. In this run, the 

model was given a downstream temperature target based on 

the inflow-mix water temperature and “filtered” twice with 

a 7-day running average (fig. 24B). These running averages 

were used simply to smooth the target temperature time series 

and remove daily variations and some effects of short-term 

weather variations. The resulting outflow water temperature 

from this simulation is shown in figure 24B along with the 

temperature target. The selective withdrawal device allowed 

the reservoir outflow to approximate a more-natural seasonal 

temperature pattern for most of the year. However, the 

reservoir did not have a sufficient stored volume of cold water 

in autumn to meet the target, leading to a small temperature 

peak at that time of year. The peak was small, and was less 

than the water temperature criterion. A comparison to the 

reservoir in 2003 without selective withdrawal (fig. 25A), 

shows that selective withdrawal (fig. 25B) led to a shallower 

thermocline, as warm water was withdrawn from near the lake 

surface in summer. Further work may examine the effect of 

such an altered thermal structure of the lake on the transport 

and fate of suspended sediment in the lake. Additional 

scenarios also could be run to simulate different outlet 

characteristics, various temperature targets, altered flows, 

changes in reservoir operation, and/or climate shifts.

Summary and Future Work

A CE-QUAL-W2 model of Detroit Lake was constructed 

and calibrated for calendar years 2002 and 2003, and for a 

period of heightened storm inflows between December 1, 

2005, and February 1, 2006. The model effectively simulated 

11

19

23

27

7

3

15

Temperature, 

in degrees 

Celsius

Variable elevation outlet

Variable 

elevation

outlet

Variable 

elevation

outlet

ELEVATION, IN METERS 371

400

450

477.3

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

2003

371

400

450

477.3

Calibrated

conditions

Selective withdrawal 

scenario

Centerline elevation of dam’s penstocks

Centerline elevation of dam’s penstocks

Figure 25. Modeled water temperature profiles in Detroit Lake, Oregon, near the dam as a function of time during 2003 for calibrated 

conditions, and the selective withdrawal scenario.

38  Modeling Hydrodynamics, Water Temperature, and Suspended Sediment in Detroit Lake, Oregon
the lake’s spatial and temporal patterns in hydrodynamics, 

water temperature, TDS, and two size groups of suspended 

sediment. Most sediment entered the reservoir during storm 

events. The lake is an efficient sediment trap, capturing more 

than 90 percent of the incoming suspended sediment in each 

of the modeled time periods. The model results indicate that 

a large percentage of suspended sand and silt was deposited 

in the upper reaches of the reservoir; this size of sediment 

typically only exited the reservoir in the outflow during 

large storm events. In contrast, clay-sized sediment stayed in 

suspension for longer periods of time, and composed most 

of the suspended sediment in the reservoir outflow. The 

source of the suspended sediment in the outflow came from 

all tributaries to Detroit Lake, but the largest contributions 

were from the two largest tributaries, the North Santiam and 

Breitenbush Rivers. A larger percentage of the suspended sand 

and silt in the outflow came from tributaries closer to the dam, 

because this size of suspended sediment settles rapidly.

Water temperature in Detroit Lake followed a seasonal 

pattern, with surface warming in spring, development of a 

thermocline in summer, and surface cooling and turnover in 

autumn. At present, the temperature of water released from 

Detroit Lake is cooler in summer and warmer in autumn 

compared to a more natural seasonal temperature pattern. 

Simulation of a hypothetical selective withdrawal device 

showed that with structural and operational adjustments, the 

outflow from Detroit Lake could approximate a more natural 

seasonal temperature pattern for most of the year, but also that 

the lake’s supply of cold water might be exhausted in autumn.

Modeling the spatial patterns of sediment deposition 

in the reservoir could be improved by including algorithms 

to simulate sediment scour and resuspension. This would 

allow a more detailed examination of the spatial patterns 

of sedimentation in the reaches near the major inflows that 

are affected by seasonal drawdown. The current Detroit 

Lake model also does not distinguish between inorganic and 

organic sediment. It would be useful to collect more data to 

determine the makeup of the inflow suspended material, as 

CE-QUAL-W2 is able to simulate degradation of particulate 

organic material. Simulation of the 2005–06 storms showed 

the importance of large storm events on sediment transport 

into and out of the reservoir, and the model could be used to 

further assess future or historic storm inflows and suspended 

sediment transport and fate. For example, the large 1996 flood 

event would be a good candidate for further use and testing of 

the model. The model also could be used to assess patterns of 

sediment deposition in the lake over long time periods.

The use of a selective withdrawal device could be 

modeled in more detail, examining how different combinations 

of outlets, various downstream temperature targets, changes 

in reservoir operation, and modified release schedules might 

affect downstream water temperatures. An existing North 

Santiam River CE-QUAL-W2 flow and water temperature 

model could be upgraded and connected to the Detroit Lake 

model in order to predict how these changes to Detroit 

Lake might affect water temperatures on the North Santiam 

and Santiam Rivers downstream to the confluence with the 

Willamette River. Extension of the Detroit Lake model to 

include the Big Cliff reregulating reservoir would be a logical 

component of that effort.

The Detroit Lake model could be expanded to include 

nutrients and algae dynamics. Blue-green algae blooms are 

a potential concern because of their associated toxins and 

their known occurrence in Detroit Lake, albeit at low levels. 

Significant blooms have occurred in other Cascade Range 

reservoirs, leading to health advisories and recommendations 

that visitors avoid contact with lake water. In order to simulate 

algae in the Detroit Lake model, additional data on nutrients, 

chlorophyll, and algae would be needed. 

Acknowledgments

This study was made possible with cooperative funding 

from the City of Salem and the USGS. Mark Uhrich (USGS) 

has led the larger effort over a number of years to study and 

monitor sediment in the North Santiam Basin; this project has 

produced much of the suspended sediment data and turbiditysuspended sediment regressions used to construct the Detroit 

Lake model. Amy Brooks, David Piatt, Anna Buckley, and 

Adam Stonewall (all USGS) helped with field work related 

to this project. Arthur Armour and Jim Britton (USACE) 

provided information on dam operation, and the USACE 

provided funding for the Agrimet weather station near Detroit 

Lake. Helpful reviews of the manuscript were provided by 

Mark Uhrich (USGS), Christopher Konrad (USGS), Robert 

Annear (Portland State University), and Sophia Hobet (City of 

Salem).

Supplemental Material

A Web site has been created to distribute supplemental 

material from this project. Visitors to http://or.water.usgs.

gov/santiam/detroit_lake/ can:

Download this report;

Obtain the calibrated Detroit Lake models, including 

model source code, data files, and model executables;

Download or view animations of model output;

Obtain algae and nutrient data collected during the 

investigation;

Download GIS coverages of the lake’s bathymetry, 

with fly-by visualizations; and

Follow links to related material and data. 

•

•

•

•

•

•

Supplemental Material 39
References Cited

Ambers, R.K.R., 2001, Using the sediment record in a western 

Oregon flood-control reservoir to assess the influence of 

storm history and logging on sediment yield: Journal of 

Hydrology, v. 244, p. 181-200.

Anderson, C.W., 2005, Turbidity (Version 2.1): U.S. 

Geological Survey Techniques of Water-Resources 

Investigations, book 9, chap. A6, section 6.7, accessed 

December 19, 2006, at http://pubs.water.usgs.gov/twri9A6/.

Bragg, H.M., and Uhrich, M.A., 2004, The North Santiam 

River, Oregon, water-quality monitoring network: U.S. 

Geological Survey Fact Sheet FS-2004-3069, 6 p.

Brune, C.B., 1953, Trap efficiency of reservoirs: Transactions 

of the American Geophysical Union, v. 34, no. 3, p. 407-

418. 

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].

E&S Environmental Chemistry, Inc. and North Santiam 

Watershed Council, 2002, North Santiam River watershed 

assessment: June, 2002, accessed August 24, 2006, at http://

www.esenvironmental.com/north_santiam_download.htm.

Hem, J.D., 1985, Study and interpretation of the chemical 

characteristics of natural water. Third Edition: U.S. 

Geological Survey Water-Supply Paper 2254, 263 p.

Horne, A.J., and Goldman, C.R., 1994, Limnology, Second 

Edition: McGraw-Hill, Inc., New York, 576 p.

Larson, D.W., 2000, Willamette Reservoirs Oregon. Detroit, 

Big Cliff, Green Peter, Foster, Blue River, Cougar. 

Limnological and water-quality studies, 1950–2000. Final 

Report: U.S. Army Corps of Engineers, 1402 p.

Lide, D.R., ed., 2006, CRC handbook of chemistry and 

physics (87th edition): Taylor and Francis, Boca Raton, FL 

[variously paged].

Oregon Climate Service, 2006, Oregon Weather Summary, 

January 2006, accessed September 24, 2006, at http://www.

ocs.orst.edu/page_links/periodicals/2006/Jan06.html.

Oregon Department of Environmental Quality, 2003, Oregon 

Administrative Rules—“The Three Basin Rule”: OAR 340-

041-0350, accessed September 29, 2006, at http://arcweb.

sos.state.or.us/rules/OARs_300/OAR_340/340_041.html.

Oregon Department of Environmental Quality, 2006, Oregon’s 

2004/2006 Integrated Report, accessed March 13, 2007, at 

http://www.deq.state.or.us/wq/assessment/rpt0406.htm.

Resource Management Associates, Inc., 2003, Blue River 

temperature modeling with HEC-5Q. Final Report: 

Prepared for U.S. Army Corps of Engineers, September.

Snyder, N.P., Rubin, D.M., Alpers, C.N., Childs, J.R., Curtis, 

J.A., Flint, L.E., and Wright, S.A., 2004, Estimating 

accumulation rates and physical properties of sediment 

behind a dam: Englebright Lake, Yuba River, northern 

California: Water Resources Research, v. 40, W11301.

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. Available online at 

http://pubs.water.usgs.gov/sir20045001/.

Sullivan, A.B., and Rounds, S.A., 2006, Modeling water 

quality 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. Available online at http://pubs.water.usgs.

gov/sir20065060/,

Sullivan, A.B., Rounds, S.A., Uhrich, M.A., and Bragg, H.M., 

2006, Modeling suspended sediment and water temperature 

in Detroit Lake, Oregon: Proceedings of the Joint Federal 

Interagency Conference, 8th FISC and 3rd FIHMC, Reno, 

NV.

Taylor, G.H., 2002, The climate of Oregon, zone 4, Northern 

Cascades, Oregon Climate Service: Special Report 914, 

accessed September 29, 2006, at http://www.ocs.orst.edu/

pub_ftp/reports/zone/zone4.html.

Uhrich, M.A., and Bragg, H.M., 2003, Monitoring instream 

turbidity to estimate continuous suspended-sediment loads 

and yields and clay-water volumes in the upper North 

Santiam River basin, Oregon, 1998-2000: U.S. Geological 

Survey Water-Resources Investigations Report 03-4098, 

43 p.

U.S. Army Corps of Engineers (1953) Water control manual 

for Detroit and Big Cliff Lakes, Oregon: Portland District 

Report, December 18, 1953.

Vanoni, V.A., ed., 1975, Sedimentation Engineering: American 

Society of Civil Engineers, New York, 745 p.

40 Modeling Hydrodynamics, Water Temperature, and Suspended Sediment in Detroit Lake, Oregon
Manuscript approved for publication, January 14, 2007

Prepared by the USGS Publishing Network, 

Publishing Service Center, Tacoma, Washington

Donita Parker

Sharon Wahlstrom

Bobbie Jo Richey

For more information concerning the research in this report, contact the 

Oregon Water Science Center Director

U.S. Geological Survey

10615 S.E. Cherry Blossom Dr.

Portland, OR 97216

http://or.water.usgs.gov
SIR 2007-5008 Sullivan and others Modeling Hydrodynamics, Water Temperature, and Suspended Sediment in Detroit Lake, Oregon

Printed on recycled paper