Tunk Creek Aquifer Test and Hydrogeologic Evaluation

Location: Riverside, Washington

Summary: ENTRIX was contracted to evaluate groundwater-surface water interactions between the underlying aquifer and nearby Tunk Creek, located on the subject property. Observed stream flow reductions in Tunk Creek pose concerns for native salmon habitat and spawning. The work was conducted in agreement with the Washington State Department of Ecology, United States Department of Fish and Wildlife, and the Confederated Tribes of the Colville Reservation.

The purpose of the aquifer evaluation was to provide the client with the upstream transfer of three non-interruptible water rights, while evaluating options to restore stream flow in Tunk Creek. These water rights would allow a more reliable source of water for irrigation.

The work included preparation of a workplan to determine whether pumping an irrigation well produces a demonstrable effect on Tunk Creek stream flows. The evaluation was conducted by performing a pumping test that included pre-test and post-test monitoring of aquifer water levels and streamflow characteristics of Tunk Creek.

Following completion of the pumping test and hydrogeologic evaluation, a hydrogeologic report was prepared and a location for a replacement well was proposed.