Yakima River Delta Habitat Assessment

Mid-Columbia Fisheries Enhancement completed an assessment of existing conditions and evaluated four different scenarios for improving salmonid passage and water quality around Bateman Island, at the confluence of the Yakima and Columbia Rivers in Richland, WA. Past work suggested that temperature was a key limit of salmonid success in that area. Warm water temperatures support large populations of predators that reduce the success of outmigrating salmon and steelhead in the spring. In the summer, lethal temperatures in the lower Yakima River impact the timing and success of migration by returning adult sockeye and summer and fall Chinook.

From the spring of 2011 to the fall of 2013, Mid-Columbia Fisheries Enhancement Group and Benton Conservation District worked with INTERA, Inc., Yakama Nation Fisheries, and a Technical Advisory Group comprised of local experts to assess flow, temperature, dissolved oxygen, and fish utilization around Bateman Island. A 500-ft long earthen causeway blocks flow along the south side of the island. Assessment work included using computer models to predict how conditions would be different if flow were allowed through the causeway area. The assessment confirmed that summer temperatures in the Yakima Delta are very warm, that dissolved oxygen levels lower in the water column approach 0 mg/ml at times, and that there is little to no flow along the south side of the island. Fish surveys found that non-native warmwater fish dominate the area.

Computer modeling of four causeway breach scenarios suggested that allowing flow along the south side of the island would reduce the spring and summer water temperatures currently experienced there. Future work will include extensive public communication on the feasibility and palatability of changes to the causeway, and close investigation of the expected benefits to migrating salmon and steelhead.

The goal of the project was to assess flow, temperature, dissolved oxygen, and fish utilization around Bateman Island to determine what factors impact salmonid migration through the area and to assess the feasibility for improving salmonid passage and water quality around Bateman Island.

Computer modeling of four causeway breach scenarios suggested that allowing flow along the south of the island would reduce the spring and summer water temperatures currently experienced there. Future work will include extensive public communication on the feasibility and palatability of changes to the causeway, and close investigation of the expected benefits to migrating salmon.