Feds release Yakima groundwater study

By Shannon Dininny
Yakima, Washington (AP) September 2010

A long-awaited federal study in central Washington’s arid Yakima River basin shows groundwater pumping significantly reduces streamflows in the river, raising questions about the state’s ability to issue new groundwater permits there without mitigating for the river’s lost water going forward.

Competition for water in the region has been brewing for more than three decades. Little has been known about the relationship between groundwater and surface water. But no new groundwater permits have been issued in the basin in nearly 20 years for fear irrigators with older, “senior” water rights could see their supply impaired, and streamflows could be reduced for threatened and endangered fish.

The study, released last week by the U.S. Geological Survey, confirms that a significant amount of water is lost to the river because of groundwater pumping and use. The study was commissioned by the state Department of Ecology, the U.S. Bureau of Reclamation and the Yakama Nation, which has the oldest water right in the region.

In a joint statement, an Ecology Department official called the findings “sobering,” and the Yakama Nation said the impairment of its water rights cannot continue or increase.

The Yakima River basin stretches from the river’s headwaters in the Cascades near Cle Elum, southeast through irrigated hay fields, orchards and vineyards to its confluence with the Columbia River in the Tri-Cities.

The report estimates, on average, that groundwater pumping reduces Yakima River flows by 200 cubic feet per second by the time the river drains into the Columbia.

Federally mandated target streamflows at two dams upstream range from 300 to 600 cubic feet per second, depending on the amount of runoff.

“The numbers are sobering,” said Ken Slattery, Ecology’s water resources program manager. “This certainly adds urgency to our efforts to tackle the basin’s water supply needs, particularly for junior water users.”

Many people have been advocating for additional reservoirs and storage to ensure a full water supply for both junior and senior water users in drought years.

The Yakama Nation raised concerns about the relationship between groundwater and surface water in the early 1990s, when it challenged new groundwater permits for orchardists east of Yakima.

“The existing groundwater pumping is impairing senior water rights in the fully appropriated Yakima Basin. Any new pumping of groundwater would do more of the same,” said Phil Rigdon, the tribe’s deputy director for natural resources.

About 900 groundwater applications are pending with the Ecology Department. Had the state granted those pending applications in 1994, the loss would have been an additional 95 cubic square feet per second in streamflows, the report said.

The basin-wide moratorium on groundwater permits excludes wells that are exempt from a permit. Under the state groundwater code of 1945, up to 5,000 gallons per day may be used for small industrial uses or domestic uses without a well permit. An unlimited amount of water from exempt wells may also be used to water livestock and for noncommercial watering of a half-acre lawn or garden.

In a separate action, Ecology officials also imposed a moratorium last year on exempt wells in the upper basin near the river’s headwaters in Kittitas County, where less is known about the relationship between groundwater and surface water. A study in that area is planned.