Water Temperature Modeling in the Middle Fork Willamette and South Santiam River Basins to Assess the Effects of Dams and Dam Operations

BACKGROUND

Hills Creek, Lookout Point and Dexter Dams are located on the Middle Fork Willamette River upstream of Eugene in western Oregon, and are important resources managed by the U.S. Army Corps of Engineers (USACE) for flood damage protection, hydroelectric power, recreation, navigation, and irrigation. Hills Creek and Lookout Point Dams impound large reservoirs (234,300 and 336,400 acre-feet of usable storage, respectively), whereas Dexter Dam is smaller and serves primarily as a re-regulating dam for releases from Lookout Point Dam. On the South Santiam River east of Albany in western Oregon, Green Peter and Foster Dams provide functions and resources that are similar to those of the Middle Fork Willamette River dams. Green Peter Lake has 312,500 acre-feet of usable storage and is much larger and deeper than Foster Lake, a downstream re-regulating project that holds 28,300 acre-feet at full pool.

The dams on both of these river systems are under scrutiny because the Reasonable and Prudent Alternatives listed in the 2008 Willamette Basin Biological Opinion (National Marine Fisheries Service, 2008) requires USACE to assess the feasibility of developing project-specific alternatives for achieving fish passage as well as improved long-term temperature control downstream of these dams. The goal of improved temperature management is to provide suitable water temperatures for endangered Upper Willamette River (UWR) Chinook salmon (Oncorhynchus tshawytscha) and UWR winter steelhead (O. mykiss). USACE must prepare an Alternatives Report addressing these issues. To support that effort, USACE asked the USGS Oregon Water Science Center (ORWSC) to model water flow and temperature through the Hills Creek/Lookout Point/Dexter dam complex on the Middle Fork Willamette River and the Green Peter/Foster dam complex on the South Santiam River system to assess the effects of potential structural and operational changes at the dams.

To help USACE determine the ways in which structural and/or operational changes to dams on the Middle Fork Willamette and South Santiam River systems can improve downstream water temperature and flow conditions for endangered fish species, the USGS is using existing models to simulate the effects of structural and operational scenarios and follow the effects downstream. On the Middle Fork Willamette River, results from the Hills Creek model feed into the Lookout Point/Dexter model. For the South Santiam River, results from the Foster model feed into a South Santiam River model.

Objectives

The objectives of this investigation are to:

1. Check and refine the model calibration for selected years within the existing Hills Creek and Lookout Point/Dexter CE-QUAL-W2 models,
2. Use the models to assess operational and structural temperature-control alternatives at Hills Creek and Lookout Point/Dexter Dams in terms of the resulting release temperatures and downstream temperatures
3. Estimate Middle Fork Willamette River water temperatures under a “no-dams” condition using current data as well as the selected datasets from objective 1
4. Document the results of the model simulations and no-dam analyses in a way that is specific to the Middle Fork Willamette River basin as well as generally applicable to other large river/reservoir systems of comparable size
5. Use the Foster Lake and South Santiam River models to assess and document downstream temperatures in the South Santiam River resulting from management strategies that vary the releases from Foster Dam.

Approach

All objectives will be completed by using existing CE-QUAL-W2 models originally developed by West Consultants, Inc., for the Lookout Point/Dexter system (West Consultants, Inc., 2004a), Hills Creek Lake (West Consultants, Inc., 2004b), Foster Lake (West Consultants, Inc., 2005), and the South Santiam River (model developed by Oregon Department of Environmental Quality and Portland State University for a temperature Total Maximum Daily Load).

• Objective 1 will be achieved through an assessment and analysis of the existing temperature models for Hills Creek Lake and Lookout Point/Dexter Lakes. The goal is to select years from the 30+ year dataset for which the models were calibrated that represent a range of expected future conditions, from cold and wet to warm and dry. That subset of years then can be imposed on the models and allow a range of predictions to be simulated. The model calibrations will be checked prior to proceeding with other aspects of the study.
• Objective 2 will be achieved by modeling a set of scenarios with the Hills Creek and Lookout Point/Dexter models in series to simulate the downstream temperature effects of structural and operational changes at the dams. Predictive uncertainty will be assessed by imposing the range of flow and meteorological conditions determined from objective 1.
• Objective 3 will be achieved by following techniques established by Rounds (2010), using data from upstream of Hills Creek Lake to estimate the flow and temperature conditions that would occur at the Dexter dam site in the absence of upstream dams. Variability and uncertainty in those estimates will be assessed by imposing the range of flow and water-temperature conditions from objective 1. The no-dam results will provide useful context for the results of operational/structural dam scenarios developed in objective 2.
• Objective 4 will be achieved by analyzing and documenting the results of the previous tasks, leading to a peer-reviewed journal article or USGS Scientific Investigations Report (SIR) to be published in FY 2013.
• Objective 5 will be achieved through an assessment and analysis of the existing temperature model of Foster Lake. A set of inflow/outflow scenarios resulting from modified operations at Foster Dam will be modeled and analyzed.

Downloads

Middle Fork Willamette

Calibrated models for 2002 [zip 4.2MB], 2006 [zip 5.7MB], 2008 [zip 4.1MB], 2011 [zip 5.4MB]

Animations: 2011

South Santiam

Calibrated models for 2002 [zip 2.4MB], 2006 [zip 4.0MB], 2008 [zip 4.0MB], 2011 [zip 4.5MB]

Selected References

Buccola, N.L., Stonewall, A.J., Sullivan, A.B., Kim, Yoonhee, and Rounds, S.A., 2013, Development of CE-QUAL-W2 models for the Middle Fork Willamette and South Santiam Rivers, Oregon: U.S. Geological Survey Open-File Report 2013–1196, 55 p. (Also available at http://pubs.usgs.gov/of/2013/1186/.)

Buccola, N.L, Rounds, S.A., Sullivan, A.B., and Risley, J.C., 2012, Simulating potential structural and operational changes for Detroit Dam on the North Santiam River, Oregon, for downstream temperature management: U.S. Geological Survey Scientific Investigations Report 2012–5231, 68 p. (Also available at http://pubs.usgs.gov/sir/2012/5231/.)

Buccola, N.L., and Rounds, S.A., 2011, Simulating potential structural and operational changes for Detroit Dam on the North Santiam River, Oregon—Interim Results: U.S. Geological Survey Open-File Report 2011–1268, 32 p. (Also available at http://pubs.usgs.gov/of/2011/1268/.)

Cole, T.M., and Wells, S.A., 2010, CE-QUAL-W2—A two-dimensional, laterally averaged, hydrodynamic and water-quality model, version 3.7: U.S. Army Corps of Engineers, Instruction Report EL-08-1, [variously paged].

Rounds, S.A., 2010, Thermal effects of dams in the Willamette River Basin, Oregon: U.S. Geological Survey
Scientific Investigations Report 2010-5153, 64 p. (Also available at http://pubs.usgs.gov/sir/2010/5153.)

Sullivan, A.B. and Rounds, S.A., 2004, Modeling streamflow and water temperature in the North Santiam and
Santiam Rivers, Oregon: U.S. Geological Survey Scientific Investigations Report 2004-5001, 35 p.
(Also available at http://pubs.usgs.gov/sir/2004/5001/.)

Sullivan, A.B., Rounds, S.A., Sobieszczyk, Steven, and Bragg, H.M., 2007, Modeling hydrodynamics, water
temperature, and suspended sediment in Detroit Lake, Oregon: U.S. Geological Survey Scientific
Investigations Report 2007-5008, 40 p. (Also available at http://pubs.usgs.gov/sir/2007/5008/.)

West Consultants, Inc., 2004a, Development of a CE-QUAL-W2 model for Lookout/Dexter Reservoirs: Seattle, WA, prepared for U.S. Army Corps of Engineers under contract DACW57-02-D-0005, 40 p.

West Consultants, Inc., 2004b, Development of a CE-QUAL-W2 model for Hills Creek Reservoir: Seattle, WA, prepared for U.S. Army Corps of Engineers under contract DACW57-02-D-0005, 42 p.

West Consultants, Inc., 2005, Development of a CE-QUAL-W2 model for Green Peter and Foster Reservoirs: Seattle, WA, prepared for U.S. Army Corps of Engineers under contract DACW57-02-D-0005, 43 p.