Palm Springs -

The U.S. Department of Justice filed a motion in federal court today asking to file a complaint in support of the Agua Caliente Band of Cahuilla ndians in its suit against two local water agencies for groundwater rights.

The documents ask the court to hold that the United States ``has federal reserved rights to sufficient groundwater as is necessary to fulfill the purposes of the tribe's reservation and to protect any prior rights of the tribe,'' and that the government seeks to dissuade the agencies -- the Coachella Valley Water District and the Desert Water Agency -- from ``injuring the tribe and individual allottees by overdrafting the groundwater of the
Coachella Valley Groundwater Basin aquifer.''

Agua Caliente tribal chairman Jeff Grubbe called the filing ``a significant step in our fight to protect the future of Coachella Valley's water supply."

``For more than 20 years, the tribe and the United States have raised concerns about the overdraft of the valley's aquifer and degradation of the drinking water,'' Grubbe said. ``... This move by the United States further proves the value and importance of our case against the water districts.''

Desert Water Agency Board President Craig Ewing said the filing ``comes as no surprise to us, as the federal government holds land in trust for the tribe.''

Ewing said the two water agencies have worked since their inception ``to ensure a safe, reliable drinking water supply for all of the residents of the Coachella Valley. We will continue to work to protect our customers as we have for decades.''

Coachella Valley Water District spokeswoman Heather Engel said the district's board of directors and general manager just received a copy of the motion today and needed time to review it before responding.

The tribe's suit against the agencies, filed a year ago in U.S. District Court in Riverside, seeks a ruling declaring the tribe's rights to valley groundwater and prevent the Desert Water Agency and Coachella Valley Water District from overdrawing and ``degrading'' the local water supply.

The two agencies said in a past joint statement that the suit would ``take away the public's rights to use Coachella Valley groundwater and prevent the public agencies' delivery of water to their customers.''

They said it would also stop them from using the Colorado River water to recharge the Upper Coachella Valley Basin, and pumping groundwater.

Since 1973, the agencies have used Colorado River water exchanged for State Water Project water to replenish groundwater in the Whitewater River sub-basin. And since 2002, they have used river water exchanged for water project water to replenish groundwater in the Mission Creek sub-basin of the Upper Coachella Valley Groundwater Basin, according to the agencies.