A report by the U.S. Geological Survey and Coachella Valley Water District showed that groundwater levels have stabilized and risen in La Quinta, while pumping caused the land to sink up to two feet in other areas of the desert, the agencies announced Tuesday.
The report showed that the rate of land subsidence -- settling or sinking of the Earth's surface -- ``substantially'' dropped after the water district's Thomas E. Levy Groundwater Replenishment Facility in La Quinta began re-supplying groundwater with Colorado River water in 2009, according to a joint statement from the agencies.
``This is very encouraging news, and is further validation of CVWD's long-term groundwater management plans to eliminate overdraft of the aquifer,'' water district General Manager Jim Barrett said. ``The mid-valley cities are currently our highest priority, and we are addressing dropping groundwater levels with the Mid-Valley Pipeline, the first phase of which was completed in 2007.''
The pipeline brings Colorado River water to golf courses in Palm Desert and Rancho Mirage to augment recycled water and help relieve demand for groundwater, he said.
According to the statement, the report showed most of the Coachella Valley was ``relatively stable,'' although land surfaces decreased nine inches to two feet in some areas of Palm Desert, Indian Wells and La Quinta between 1995 and 2010.
Sinking was seen in or near areas where groundwater pumping ``generally caused seasonal groundwater-level fluctuations and longer-term groundwater-level declines'' from 1993 to 2010.
In 2010, some groundwater levels ``were at the lowest levels in their recorded histories,'' according to the statement.
According to the USGS, more than 80 percent of land subsistence in the country is because of ``exploitation'' of underground water. According to the joint statement, settling or sinking can cause damage to infrastructure such as roads, bridges and canals.
``Continued monitoring in the Coachella Valley is warranted because groundwater levels continue to decline in some areas due to pumping,'' said Michelle Sneed, a USGS hydrologist and project chief. ``The Coachella Valley Water District has been proactive in their efforts to mitigate groundwater overdraft and subsidence -- continued monitoring will provide them feedback to assess their operations, and information to help in planning for sustainable aquifer system use.''
Data for the report was collected from 1993 to 2010 using satellite radar imaging data, and covered from Palm Desert to near the Salton Sea.
The water district and Desert Water Agency have been sued by the Agua Caliente Band of Cahuilla Indians for allegedly overdrafting groundwater in the valley.
The full report, ``Land Subsidence, Groundwater Levels, and Geology in
the Coachella Valley, California, 1993-2010,'' is available at www.usgs.gov.