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Sources of High-Chloride Water to Wells, Eastern San Joaquin Ground-Water Subbasin, California

November 15, 2006

As a result of pumping and subsequent declines in water levels, chloride concentrations have increased in water from wells in the Eastern San Joaquin Ground-Water Subbasin, about 80 miles east of San Francisco (Montgomery Watson, Inc., 2000). Water from a number of public-supply, agricultural, and domestic wells in the western part of the subbasin adjacent to the San Joaquin Delta exceeds the U.S. Environmental Protection Agency Secondary Maximum Contaminant Level (SMCL) for chloride of 250 milligrams per liter (mg/L) (fig. 1) (link to animation showing chloride concentrations in water from wells, 1984 to 2004). Some of these wells have been removed from service. High-chloride water from delta surface water, delta sediments, saline aquifers that underlie freshwater aquifers, and irrigation return are possible sources of high-chloride water to wells (fig. 2). It is possible that different sources contribute high-chloride water to wells in different parts of the subbasin or even to different depths within the same well.

Citation Information

Publication Year 2006
Title Sources of High-Chloride Water to Wells, Eastern San Joaquin Ground-Water Subbasin, California
DOI 10.3133/ofr20061309
Authors John A. Izbicki, Loren F. Metzger, Kelly R. McPherson, Rhett R. Everett, George L. Bennett V
Publication Type Report
Publication Subtype USGS Numbered Series
Series Title Open-File Report
Series Number 2006-1309
Index ID ofr20061309
Record Source USGS Publications Warehouse