Yakima River Basin Groundwater Study

The final report of the 12-year USGS study on the impact of groundwater pumping on surface water in the Yakima Basin is now available:


View a copy of the report

Yakima River Basin Groundwater Study

October 2011 – Final USGS report on Yakima Basin groundwater

On Sept. 16, 2011, the U.S. Geological Survey released the long-awaited Yakima Basin groundwater study confirming groundwater connected to rivers and streams.

The first comprehensive groundwater flow model for the entire Yakima River Basin is detailed in the report.  To view the report use the link in the right column .

Because of increasing demand for water in the basin, managers need an integrated understanding of the aquifer system and how it is connected to rivers and streams. USGS scientists have studied the aquifer system's water levels, hydrogeology, pumpage, recharge, flow, and connections to surface water—all of which are incorporated in the model. Some of this information was released in a series of earlier reports, and this thirteenth report in the series documents the model and the various scenarios simulated by the model.

Results of the Yakima Basin USGS groundwater study and model will inform how we manage groundwater in the Yakima Basin. The model will provide the scientific platform for making decisions on a backlog of pending groundwater applications and for how mitigation may allow “new” water withdrawals.


In a 1999 MOA, Water Manager Partners: US Bureau of Reclamation and Yakama Nation agreed this model will be the accepted basis for making decisions and determining mitigation.

Ecology is working to engage its water partners, Reclamation, Yakama Nation, and watershed stakeholders in understanding the ramifications of the report.

While the conflict between groundwater and surface water isn’t new, we face new challenges to manage surface water and groundwater resources as a single resource, when historically we’ve managed them independently.

News release

The report

Study done in three phases

The groundwater study in the Yakima Basin was done in three phases:

Additional information


Central Region Water Resources Program
Phone: (509) 575-2597