Flow Characterization Study: Instream Flow Assessment. Hawley Creek Eighteenmile Creek, Idaho

摘要

The Bureau of Reclamation conducted flow characterization and habitat studies on Hawley Creek and Eighteenmile Creek, located in the Lemhi River sub-basin in Idaho, to identify stream flow needs to support relevant life history stages of summer steelhead (Oncorhynchus mykiss), spring Chinook salmon (O. tschawytscha), and bull trout (Salvelinus confluentus). Average snowpack level in the Salmon River Basin on April 1, 2006 was 107 percent, compared to 60 percent of the average snowpack in 2005. Hawley Creek and Eighteenmile Creek flows were continuously recorded using a stage recorder during the 2006 irrigation season. Water temperatures were also monitored in 2006. Reclamation characterized flow needs for various life stages of the selected species using the Physical Habitat Simulation (PHABSIM) model at each study site. To address food resources of salmonids, streamflow needs for aquatic macroinvertebrates were assessed. Data were collected at a total of 10 study sites: four on Hawley Creek and six on Eighteenmile Creek. Study sites were selected in accessible areas to represent mesohabitat types within each stream reach distinguished by unique hydrology, channel morphology, slope, or land use characteristics. Low, medium, and high flow measurements were attempted during the irrigation season at most sites downstream from the reference sites. In most cases, only medium and low flow conditions were measured because most of the high flows were diverted for irrigation. However, medium and low flows typically occur during the summer irrigation season with the diversions.