A three-mile segment of the Walla Walla River near Milton-Freewater, Oregon was dewatered each summer for the last century creating the need for fish rescues.  The rescues have not been necessary the last twelve years after aggressive irrigation efficiency programs and new wells that now allow for at least 27 cfs to be maintained instream throughout the spring and 25 cfs instream throughout the summer.  However, half of these bypass flows are created by an increase in supplemental well use at unsustainable rates.  Additional irrigation conservation practices, combined with winter/spring groundwater recharge, will allow irrigators to reduce their demand on the river, reduce negative impacts to groundwater, and protect the conserved water as instream water rights.

This irrigation efficiency and groundwater recharge project will improve stream flows for the passage and rearing of summer steelhead, spring Chinook, and bull trout in a flow-impaired segment of the Walla Walla River.  The Walla Walla Subbasin Plan’s highest priority project types are those that address imminent threats to ESA listed species, such as dry or low flow stream reaches.  This project will address a Subbasin Plan priority restoration area that provides habitat and also passage to primary upstream spawning grounds.  Irrigation efficiency projects will utilize the Oregon Conserved Water Program to ensure that conserved water is protected as an instream water right.  Shallow Aquifer Recharge (SAR) using high winter and spring runoff will benefit spring branches and mainstem cold water refugia.

Additional opportunities exist for SAR development where monitoring and modeling has identified groundwater declines and associated river baseflow declines. Funds from this contract and contracts with Oregon Water Enhancement Board and Washington Department of Ecology allow for the continued monitoring that determines the correct placement of these sites that support flows in the Walla Walla River for fish migration and habitat through the recovery of the shallow alluvial aquifer storage and tributary and river base flow recovery.

Timeline: This is expected to be ongoing monitoring as groundwater re-charge is implemented and adaptive management review success each year.
Once monitoring shows that SAR sites are adequately mitigating for losses in the aquifer, additional sites will no longer be needed and monitoring for these purposes can stop.