After a half-century under “interim” rules, the Washington Department of Ecology has begun a new process to design a permanent groundwater management framework for the Pasco Basin. By working with the U.S. Bureau of Reclamation to allocate and manage groundwater in the area, Ecology believes the new groundwater rule will increase the amount of water legally available in the basin and resolve legal and regulatory questions over how that water can be used.

“Despite numerous efforts over the past 50 years, groundwater in the Pasco Basin has remained under an interim rule,” said Tom Tebb with Ecology’s Office of Columbia River. “Adopting a permanent rule will resolve longstanding uncertainty in groundwater management in the Pasco Basin and make new groundwater supplies available for beneficial use.”

In 2021, the Washington Legislature revised Ecology’s authority to enter into an agreement with the U.S. Bureau of Reclamation in order to allow the two agencies to develop a groundwater co-management strategy. That legislative action was necessary, because the Pasco Basin has naturally occurring groundwater that mixes with irrigation water return flows -- referred to as “commingled groundwater.”

Differentiating between these water types is important because all naturally occurring groundwater in Washington is a state resource managed by Ecology. Those return flows coming from water used in the Columbia Basin Project, however, are managed and licensed by Reclamation and sold to irrigators to be used on crops or are lost to evaporation and infiltration​​ into the ground while being used.

Ecology’s first step will be setting a boundary to define the area in the Pasco Basin where groundwater will be managed.

Following the boundary designation Ecology will establish a new rule for groundwater management and the interim management rule will be repealed. The process is expected to be completed and the new rule effective in late 2025.

“This process is intended to add clarity and consistency for current and future water rights holders in the Pasco Basin,” said Mary Verner, who manages Ecology’s Water Resources program. “We are committed to a phased approach that encourages and values input from the community.”

Visit Ecology’s rule website for information and to sign up for email updates.