August 22, 2008

Water district expands valley groundwater recharge facilities

Ground was broken today at Coachella Valley Water District's (CVWD) newest full-scale groundwater recharge facility, which will replenish 40,000 acre-feet annually into the eastern Coachella Valley's aquifer. This amount of water is equal to what is used each year by about 85,000 residents and will alleviate the overdraft of groundwater supplies throughout the eastern valley.

Representatives from all levels of government, other water agencies, agriculture and business were among those who attended the brief ceremony at the facility, located west of Monroe Street, between Avenues 60 and 62 in La Quinta.

"This is a significant milestone in our efforts to ensure that a reliable supply of groundwater will continued to be available, across the entire valley, now and for many generations to come," said CVWD General Manager-Chief Engineer Steve Robbins.

The Dike 4 Groundwater Recharge Facility is named due to its proximity to the Dike 4 flood control berm. The facility takes advantage of existing pipes currently used to deliver Colorado River water from Lake Cahuilla, at the terminus of the Coachella Canal, to farmland. Thirty-nine recharge basins are being built at the facility and will cover nearly half of the project's 163 acres.

Replenishment is among the most effective methods available for preserving local groundwater supplies, reversing aquifer overdraft and meeting demand by domestic and commercial water consumers.

CVWD and Desert Water Agency have been cooperatively recharging the upper Coachella Valley at Windy Point, west of Palm Springs, with their entitlements to State Water Project water for 35 years. Additional replenishment began at Mission Creek about five years ago. Since 1973, the aquifer has been replenished with more than 2 million acre-feet of imported water. Aquifer overdraft in the valley was approximately 5.1 million acre-feet at the end of 2007.

CVWD launched two pilot projects to ensure that meaningful replenishment was possible in the eastern valley. Replenishment at Dike 4 began in 1997, and through last year nearly 25,000 acre-feet had been recharged there; at Martinez Canyon, recharge began in 2005, with replenishment exceeding 4,150 acre-feet in 2007.

Scientific studies concluded these were suitable locations in the eastern valley for effective aquifer recharge. A clay aquitard allows for the drilling of wells in the eastern valley, but thwarts the use of conventional groundwater replenishment techniques on the valley floor. Water cannot percolate directly through the clay layer into the lower aquifer, in which most of the water suitable for domestic and irrigation purposes is located.

Along the edges of the eastern valley, however, the absence of the aquitard and the presence of more permeable materials make replenishment feasible. The aquitard actually enhances the distribution of replenishment water because it creates pressure that pushes recharged water throughout the lower aquifer.

To date, $43 million has been budgeted for the Dike 4 recharge facility; $6 million for the pump plant, $10 million for the recharge basins and $27 million for land acquisitions.