Ground-water flow and solute movement to drain laterals, western San Joaquin Valley, California; I, Geochemical assessment

Open-File Report 90-136
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Abstract

A study was undertaken to quantitatively evaluate the hydrologic processes affecting the chemical and isotopic composition of drain-lateral water in a drained agricultural field in the western San Joaquin Valley, California. The results of chemical and isotopic analysis of the samples and analysis of hydraulic-head data and drain-lateral flow data elucidate the process of mixing of deep and shallow ground water entering the drain laterals. The deep ground water was subject to partial evaporation prior to drainage-system installation and has been displaced downward (at depths greater than 6 meters) in the ground-water system. This ground water is flowing toward the drain laterals. The percentage of the deep, isotopically enriched ground water entering the drain laterals varies with time and between drain laterals. The percentage of the total drain-lateral flow, which is deep ground-water flow, is about 30 percent for the shallow drain lateral (1.8 meters below land surface) and 60 percent for the deep drain lateral (2.7 meters below land surface). During irrigation, the percentages decrease to 0 and 30 percent for the shallow and deep drain laterals, respectively.

Selenium loads in the drain laterals vary with time and between drain laterals. The selenium load for the shallow drain lateral (68 kilograms) during 1 year is 21 percent of the load for the deep drain lateral (332 kilograms) because it collects less deep, high-selenium ground water and does not flow continuously. Although selenium concentrations in the drain-lateral water decreased during irrigation, selenium loads increased substantially during a preplant irrigation because of increased flow into the drain laterals. The selenium loads during 8 days of irrigation represented a substantial percentage (25 percent for the shallow drain lateral and 11 percent for the deep drain lateral) of the total selenium load for 1 year.

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Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title Ground-water flow and solute movement to drain laterals, western San Joaquin Valley, California; I, Geochemical assessment
Series title Open-File Report
Series number 90-136
DOI 10.3133/ofr90136
Year Published 1990
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) California Water Science Center
Description iv, 23 p.
Country United States
State California
Other Geospatial San Joaquin Valley