Executive SummaryIn 199 1, the Pacific Northwest Laboratory (PNL) began studying water quality at several sites in the Yakima River Basin for the Bonneville Power Administration. These sites were being proposed as locations for fish culture facilities as part of the Yakima Fisheries Project (YFP). I.nformation on the quality of surface water and groundwater in the basin was needed to develop strategies for meeting artifical and natural production objectives of the YFP.Our studies indicate that surface water quality parameters near the proposed fish culture facilities are currently suitable for fish production, Water quality conditions in the mainstream Yakima River and its tributaries are generally excellent in the upper part of the watershed (i.e., near Cle Elum), but they are only fair to poor for the river downstream of Union Gap (river mile 107). Water quality of the Naches River near Oak Flats is also suitable for fish production.Groundwater supplies near the proposed fish production facilities typically have elevated concentrations of metals and dissolved gases. These conditions can be mitigated using best engineering practices such as precipitation and degasification. Additionally, mixing with surface water may improve these conditions. Depending on the location and depth of the well, groundwater temperatures may be warmer than optimum for acclimating and holding juvenile and adult fish. This condition may require that chillers be operated during the late summer holding periods. Additionally, planned water use requirements of some sites (i.e., Oak Flats and Nelson Springs) exceed the capacity of groundwater wells currently drilled at the sites. Thus, additional wells would be required or water requirements for fish culture activities would have to be modified.Water quality parameters measured in the Yakima River and tributaries sometimes exceed the range of values described as acceptable for culture of salmonids and for the protection of other aquatic life. However, constituent concentrations are within ranges that exist in many northwest fish hatcheries. Additionally, site-specific tests conducted by PNL (i.e., live box exposures and egg incubation studies) indicate that fish can be successfully reared in surface and well water near the proposed facility sites. Thus, there appear to be no constraints to artificial production for the YFP. However, studies by the U.S. Geological Survey and others suggest that water quality and excessive temperature in the lower Yakima River downstream from Prosser may limit natural production of some stocks of salmonids. The principal reasons for decreased water quality in the lower Yakima River include the relatively high volume of irrigation return flow.A monitoring and evaluation plan should be developed for the YFP that includes water quality measurements of water sources used for fish production and biological measures of fitness. In addition, an integrated temperature monitoring network should be implemented throughout the basin.
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AcknowledgmentsWe are grateful to...