Water in eastern Washington is a scarce resource, and tracking groundwater sources and supplies is a critical part of making sure there is enough water to meet everyone’s needs. A new legal designation from the Washington Department of Ecology establishes the boundaries for a future groundwater co-management agreement in the Pasco Basin between state and federal water managers.
“Establishing this framework is a long-needed and important step for the Pasco Basin,” said Ria Berns, Ecology’s Water Resources manager. "For decades, water users in the area have relied on temporary water permits, which create uncertainty. This boundary designation is the first step toward finalizing those authorizations and considering new water uses.”
The area defined in the designation covers the southern third of Grant County, the western half of Franklin County, and the western third of Adams County, matching earlier temporary boundaries. Pasco Basin reference map
With the boundary established, Ecology will continue developing a shared-management program with the U.S. Bureau of Reclamation to address what’s known as “co-mingled groundwater.” Co-mingled groundwater is a term used when underground water from both state-managed and federally-managed sources mixes within the same basin.
In the Pasco Basin, the Columbia Basin Reclamation Project has made federally managed water available for irrigating crops. The runoff from that irrigation mixes with state-managed groundwater. This blending of water sources can make it difficult to determine ownership or usage rights, often leading to legal and regulatory challenges—particularly during drought conditions or in long-term water planning.
Designating the boundary is an initial step in a multi-phase process designed to provide long-term certainty for groundwater users in the area. This designation defines the geographic area where the new co-management rule will apply. The entire process is expected to be completed by 2027.
“Managing our shared water resources is important to help farmers, families and local businesses move forward with confidence,” Berns said. “By reducing uncertainty about who can use what water, we can speed up approvals, support smarter planning during dry years and ensure communities have the water they need.”
A 30-day appeal period is now open following the issuance of the final order.