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Instream Flow Characterization of Upper Salmon River Basin Streams, Central Idaho

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Historically, upper Salmon River basin rivers, streams, and lakes have provided migration corridors and significant habitat for anadromous Chinook salmon, sockeye salmon, and steelhead trout. Bull trout also inhabit many of these rivers and streams. However, human development has modified the original flow in a number of key stream reaches. Reduced flow caused by diversions has:

  • affected the quantity and quality of fish habitat
  • limited the migration and/or access to suitable spawning and rearing habitat
  • increased water temperatures (which may prove to be unsuitable for native salmonids)

In 1990, chinook salmon (Oncorhynchus tshawytscha) and steelhead trout (Oncorhynchus mykiss) were listed as endangered or threatened under the Endangered Species Act, and bull trout (Salvelinus confluentus) were listed as threatened in 1998.

Sawtooth Mountains
Sawtooth Mountains, upper Salmon River Basin, ID. Photo by USGS.

How the USGS Helps

Between 2003 and 2005, our scientists collected fish community, habitat, water-quality, and streamflow data to support the development of a Physical Habitat Simulation model (PHABSIM) for the Salmon River and its tributaries.

Our scientists produced three reports to describe PHABSIM modeling results for bull trout, Chinook salmon, and steelhead trout during summer streamflows. Habitat/discharge relations were summarized for adult and spawning life stages at each study site. Natural summer streamflows were estimated for each study site using regional regression equations. In addition, streamflow needs for riffle dwelling invertebrate taxa (Ephemeroptera, Plecoptera, and Trichoptera) were summarized in 2005.

Adult fish passage and discharge relations were evaluated at specific transects that were identified as potential low-streamflow passage barriers at each study site.

Continuous summer water temperature data for selected study sites were summarized and compared with Idaho Water Quality Standards and various water temperature requirements of targeted fish species.

Key Results

Our scientists created and described habitat suitability curves and instream flow characteristics for several tributaries of the upper Salmon River.

Results of these habitat studies can be used to prioritize and direct cost-effective actions to improve fish habitat for ESA-listed anadromous and native fish species in the basin. These actions may include acquiring water during critical low-flow periods by leasing or modifying irrigation delivery systems to minimize out-of-stream diversions.

Products

Maret, Terry R., Hortness, Jon E., and Ott, Douglas S., Instream flow characterization of upper Salmon River basin streams, central Idaho, 2005: U.S. Geological Survey Scientific Investigations Report 2006-5230.

Maret, Terry R., Hortness, Jon E., and Ott, Douglas S., Instream flow characterization of upper Salmon River basin streams, central Idaho, 2004: U.S. Geological Survey Scientific Investigations Report 2005-5212.

Maret, Terry R., Hortness, Jon E., and Ott, Douglas S., Instream flow characterization of upper Salmon River basin streams, central Idaho, 2003: U.S. Geological Survey Scientific Investigations Report 2004-5173.