Web-based USGS map tracks declining water levels

Scientists report 70-year trend continues in Mojave River and Morongo ground-water basins

Groundwater levels in most areas of the Mojave River and in the Morongo Basin in San Bernardino County, Calif., continue to decline, as they have for the past 70 years, the U.S. Geological Survey (USGS) says in a new report.

The report, "Water-level and land-subsidence studies in the Mojave River and Morongo Ground-Water Basins, Southwestern Mojave Desert, California," was co-authored by USGS scientists Christina L. Stamos, Kelly R. McPherson, Michelle Sneed and Justin T. Brandt. They found that from the years 2004 to 2006, 188 of 611 wells measured had water-level declines greater than one-half foot. More than 40 of the wells had declines greater than 5 feet. This continuing, incremental drop in water levels over the past 70 years has resulted in total water-level declines of almost 100 feet in some areas east of Victorville and of more than 100 feet east of Barstow, north of Lucerne Valley and within the U.S. Marine Corps base at Twentynine Palms.

The report is the eighth in a series published by the USGS in cooperation with the Mojave Water Agency in an effort to monitor ground-water in the Mojave River and Morongo basins. Study results can be found at an interactive Web site at http://maps.ca.water.usgs.gov/Mojave/.

Water-level increases were noted in areas near the Mojave River, probably due to high storm-flows in the winter of 2005, said co-author Stamos. But the overall trend in areas away from the river is one of decline, she said.

In addition to regional water-level maps, this year's report includes maps that show the location and change in land-surface height in the region between 1999 and 2004. These were included to address concerns related to new or renewed land subsidence brought on by continuing water-level declines. The areas of El Mirage, Lucerne Valley, Newberry Springs, and the northeast shore of Harper Lake had land-surface subsidence of as much as ½ inch during that 5-year period. A reduction in pumping along the southwest shore of Harper Lake has resulted in land-surface uplift of as much as a 1/2 inch.

The website was created to centralize water-level data collected and compiled by the USGS and make it easily available to the public. One feature of the site is an interactive map that allows the reader to view any of the data from the eight water-level reports, to compare and view water-level data from any of the maps, and to perform tasks such as querying and identifying data.

"We hope the interactive maps and other tools are useful for water agencies, well owners and anyone else interested in ground-water in the Mojave Desert," Stamos said. "The Web maps are 'living documents,' in the sense that we will update them as new information becomes available. We expect this trend toward online publishing to continue as we try to make our science more accessible and useful to the public."

The Mojave River ground-water basin covers about 1,400 square miles and extends from the San Bernardino and San Gabriel mountains in the south to the normally dry Harper and Coyote lakes in the north. The Morongo ground-water basin covers about 1,000 square miles and is surrounded by the Ord and Granite Mountains to the north, the Bullion Mountains to the east, the San Bernardino Mountains to the southwest, and the Little San Bernardino Mountains to the south.

The report was authored by scientists from USGS' California Water Science Center. The center, based in Sacramento, has more than 130 scientists who bring a broad range of scientific disciplines to the study of modern water management issues.

USGS provides science for a changing world. For more information, visit www.usgs.gov.

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