Groundwater levels are rising and subsidence rates have decreased in parts of the eastern Coachella Valley, in part due to Coachella Valley Water District (CVWD)’s replenishment program, according to a U.S. Geological Survey (USGS) study released Tuesday. No measureable land subsidence was observed from 2005 to 2010 at most of the gps locations used for the study.
At five locations in La Quinta, average subsidence rates decreased near the Thomas E. Levy Groundwater Replenishment Facility based on measurements taken in 2010, only one year after the facility went into full operation. USGS measured ground uplift at one of the locations with previously observed subsidence.
Groundwater levels have increased as much as 75 feet, according to CVWD well monitoring within six miles of the facility. Since 2009, groundwater levels have increased an average of 26 feet in about 200 wells throughout the eastern Coachella Valley.
“This is great news for the eastern Coachella Valley. It confirms that CVWD’s long-term groundwater management plans are working and we’re on track to eliminating overdraft of the aquifer,” said CVWD General Manager Jim Barrett.
The USGS study measured land subsidence from 2005-2010 in the area from Rancho Mirage to the Salton Sea. It compared the recent measurements with data collected in previous studies dating back to 1993. The studies document the continuing decline of groundwater levels, and the possible connection to land subsidence in parts of the study area.
While most of the study area was stable, observed land surface declines ranged from less than 9 inches to almost two feet in isolated areas of Palm Desert, Indian Wells, and La Quinta, between June 1995, and September 2010. One of the areas with the largest decline was roughly located north of Fred Waring Drive, between Bob Hope Drive and Monterey Avenue, near the border of Palm Desert and Rancho Mirage.
“The mid-valley cities are currently our highest priority in terms of groundwater management,” Barrett said. “The western Coachella Valley is in great shape due to 40 years of a cooperative groundwater replenishment program with Desert Water Agency at the Whitewater Groundwater Replenishment Facility.”
To specifically address dropping groundwater levels in the mid-valley, CVWD completed the first phase of the Mid-Valley Pipeline in 2007, bringing Colorado River water to golf courses in Palm Desert and Rancho Mirage to supplement the recycled water supply and help alleviate demand for groundwater. Today, 45 golf courses in CVWD’s service boundary are using a non-potable supply.
An additional 48 golf courses have been identified as future nonpotable water users.
The Coachella Valley Water Management Plan (available for review online at www.cvwd.org) is the district’s blueprint for eliminating groundwater overdraft through a multi-prong strategy that includes expansion of the nonpotable water supply to farms and golf courses in lieu of groundwater, increasing the amount of imported water for replenishment, and promoting water conservation through education, rebates and other incentive programs.
A recent staff report on the status of the Coachella Valley Water Management Plan indicates that long-term overdraft could be eliminated as soon as 2021.
“Continued monitoring in the Coachella Valley is warranted because groundwater levels continue to decline due to pumping and aquifer system overdraft,” said Michelle Sneed, hydrologist and project chief with the USGS. “The Coachella Valley Water District has been proactive in their efforts to mitigate groundwater overdraft and subsidence — continued monitoring will provide them the feedback to assess their operations, and the information needed to take effective action to plan for sustainable aquifer system use.”
By comparison, the USGS has monitored land subsidence of 28 feet in the San Joaquin Valley from 1926 to 1970, and as much as one foot per year near the Delta-Mendota Canal in the Central Valley from 2008 to 2010.
The USGS study of the Coachella Valley was funded through a cooperative agreement with CVWD. A copy of the full study, “Land Subsidence, Groundwater Levels, and Geology in the Coachella Valley, California, 1993-2010,” can be found at www.usgs.gov.
“CVWD is committed to continuing to fund this important research,” Barrett said. “We rely on the data to help shape our long-term groundwater management efforts, monitor successes and identify areas in need of additional focus,” Barrett said.
The Coachella Valley Water District is a public agency governed by a five-member board of directors. The district provides domestic and irrigation water, agricultural drainage, wastewater treatment and reclamation services, regional storm water protection, groundwater management and water conservation. It serves approximately 108,000 residential and business customers across 1,000 square miles, located primarily in Riverside County, but also in portions of Imperial and San Diego counties. For more information, please visit www.cvwd.org.