Walla Walla Technical Work Group's Walla Walla River Seepage Studies

and Surface Water Budget PDF 6/24/05

The Walla Walla River basin is a bi-state watershed that originates in Oregon and passes through the state of Washington on route to its confluence with the Columbia River (Figure A-1). As in many watersheds in the Western United States, the Walla Walla River basin’s water quality and endangered species issues are heavily influenced by the timing, availability, quality and quantity of water originating from both surface and ground resources. While the more obvious, seasonal variation in supply (winter-spring = higher flows, summer-fall = lower flows) is well documented in readily available annual hydrographs and continuous flow data. An understanding of how Walla Walla River flow varies spatially relative to water use, groundwater inputs, evaporation, irrigation returns and tributary inputs is lacking. From the near pristine headwaters (South Fork @ Reser Creek) to near the confluence with the Columbia (Nine Mile Bridge) variations in geology, geomorphology, riparian ecology, water and land management, weather, elevation, and fisheries habitat also help shape the flow profile for the Walla Walla River.

Starting in 2002, a group of agencies and groups from Washington and Oregon starting conducting seasonal instream flow, diversion inventories, and tributary flow surveys termed “seepage runs” as a primary first step toward quantifying the spatial variation in water volume for the Walla Walla River. The idea originally came from work being conducted on the Dungeness River in Clallam County, Washington by the USGS and WDOE (Simonds, Sinclair, 2002). Seepage runs were conducted in two primary seasons of concern; June when ESA listed fish species are moving from the lower to upper watershed to either spawn or rear for the summer months and August when Clean Water Act water quality issues and low flow volumes are at their most critical levels. This report shares the baseline assessment and the data collected from these bi-state cooperative seepage runs. The primary focus of the water budget analysis presented in this report to quantify the channel bed gains and losses.

For more information about this project please contact: Bob Bower

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