Tracing Reclaimed Water in the Menifee, Winchester, and Perris-South Ground-Water Subbasins, Riverside County, California
By Charles A. Kaehler and
U.S. GEOLOGICAL SURVEY
Water-Resources Investigations Report 03-4039
Sacramento, California 2003
Prepared in cooperation with the Eastern Municipal Water District
Text (1.8 MB PDF)
Front Cover of Report (482 KB PDF)
To view PDF documents, you must have the Adobe Acrobat Reader (free from Adobe Systems) installed on your computer.
(download free copy of Acrobat Reader).
As a component in the management of water resources in the Menifee, Winchester, and Perris-South subbasins in Riverside County, California, ponds are operated by the Eastern Municipal Water District for the temporary storage of reclaimed water that is produced by several regional water-reclamation facilities. A primary goal of this study was to evaluate the potential for using various ground-water constituents or characteristics as tracers of reclaimed water that has infiltrated from the storage ponds into the ground water in the three subbasins. A secondary goal was to estimate the degree to which the infiltrated reclaimed water has mixed with the native ground water. The evaluation of potential tracers and the estimation of mixing focused on data from wells located relatively close to the ponds.
The most useful constituents and characteristics for evaluation of the fate and mixing of reclaimed water in the Menifee, Winchester, and Perris-South subbasins are major-ion composition, stable isotopes of hydrogen and oxygen, ultraviolet absorbance (UV-A), chloride concentration, and boron/chloride ratio plotted against chloride concentration. Emphasis in this study was placed on evaluating the utility of UV-A as a tracer and boron/chloride ratios in estimating the fraction of reclaimed water in ground water.
In the Menifee subbasin, major-ion data, stable isotopes, chloride, UV-A, and boron/chloride ratio are all useful in identifying reclaimed water, and the results based on these indicators are consistent with each other. The results suggest that values of UV-A greater than or equal to 0.007 indicate the presence of reclaimed water in the Menifee subbasin. Ground-water samples with UV-A greater than 0.007 are estimated to consist of about 75 to 100 percent reclaimed water, on the basis of chloride-mixing calculations and boron/chloride-versus-chloride mixing calculations.
In the Winchester subbasin, results based on the same factors used in the Menifee subbasin are less conclusive; nevertheless, UV-A can be used as a tracer. The results suggest that values of UV-A greater than 0.01 indicate the presence of reclaimed water. Values from 0.006 to 0.01 may indicate the presence of reclaimed water; however, water from wells not likely to have reclaimed water may also have UV-A values in this range. Ground-water samples with UV-A greater than 0.01 seem to contain about 25 percent reclaimed water (range 6 to 32 percent), on the basis of the consistency of the results of three types of mixing calculations--chloride alone, boron/chloride versus chloride, and UV-A.
In the Perris-South subbasin, the potential tracers are not as conclusive in identifying reclaimed water in the subsurface as in the Menifee and Winchester subbasins. The less-conclusive results are a consequence of the multiple, spatially distributed sources of reclaimed water; the relative absence of wells close to the reclaimed-water pond; and the short period of operation (about 1 year) of the pond at the time of sampling. Mixing calculations suggest that ground-water samples with elevated UV-A values (greater than 0.01) in the Perris-South subbasin could contain as much as 40 to 65 percent reclaimed water.
Purpose and Scope
Methods of Sample Collection and Analysis
Description of the Study Area
Inorganic and Organic Tracers
Inorganic-Constituent Mixing Models
Tracing Reclaimed Water in the Three Subbasins
Summary and Conclusions
Document Accessibility: Adobe Systems Incorporated has information about PDFs and the visually
impaired. This information provides tools to help make PDF files accessible. These tools convert Adobe PDF documents
into HTML or ASCII text, which then can be read by a number of common screen-reading programs that synthesize text as
audible speech. In addition, an accessible version of Acrobat Reader 5.0 for Windows (English only), which contains
support for screen readers, is available. These tools and the accessible reader may be obtained free from Adobe at Adobe Access.
Water Resources of California