Water Temperature Modeling in the Middle Fork Willamette and South Santiam River Basins

Science Center Objects

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 control, hydroelectric power, recreation, navigation, and irrigation. 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. 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 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. To support that effort, USACE asked the USGS Oregon Water Science Center to model water flow and temperature through the dam complexes on the Middle Fork Willamette and South Santiam Rivers to assess the effects of potential structural and operational changes at the dams.

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 control, 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 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 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.

Model 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]