Sources and Circulation of Salt in the San Joaquin River Basinby Leslie F. Grober,
Abstract: Historical data and a water quality model were used to quantify the sources of salt, boron and selenium in the lower San Joaquin River (SJR) basin, California. Mean monthly data for sources and sinks in the SJR basin and Delta Mendota Canal (DMC) service area were assembled and evaluated. The San Joaquin River Input-Output model (SJRIO), a mass balance water quality model, was used to estimate mean monthly salt, boron, and selenium loads for various inflows to the SJR. Model results show that agricultural drainage discharges are the primary source of dissolved salts, boron and selenium to the SIR. Groundwater accretions and seasonal wetland releases are also important sources of salt and boron. Salt dissolved in DMC water imports is the primary source of salt circulating in the lower SIR basin; in situ dissolution of salts and pumping from the underlying confmed aquifer are important secondary sources. Salts are moved out of the basin only in the SIR but some salt is also moved out of the unconfmed aquifer of the basin into long term storage in the confined aquifer beneath the basin. The DMC supplies most of the higher quality surface irrigation water in the lower SIR basin. The quality of this supply may be impaired by the recirculation of salts from the SIR to the DMC intake pump, leading to a greater net accumulation of salts in the basin.
Subject Headings: Basins | Salts | Salt water | Water circulation | Water quality | Hydrologic models | Rivers and streams | Aquifers | Selenium | North America | California | United States
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