San Joaquin - Tulare NAWQA Program

Surface Water - Cycle II San Joaquin River near Vernalis, CA (11303500)
The San Joaquin River receives water from tributaries draining the Sierra Nevada and Coast Ranges, and except for streams discharging directly to the Sacramento-San Joaquin Delta, is the only surface-water outlet from the study area. The water quality of the San Joaquin River is of critical interest because it flows to the delta. Both the Delta-Mendota Canal, which supplies irrigation water to farms in the western San Joaquin Valley, and the California Aqueduct, which supplies drinking water to southern California, originate in the delta.

The San Joaquin River is being sampled for water-borne constituents and biological characteristics as part of the Trend Network for Streams. Water, fish and streambed sediment were also sampled for mercury and methylmercury in the summer of 2002 as part of the Status Assessment for Mercury.

Map showing location of the San Joaquin River Basin

San Joaquin River Basin

Photograph of the San Joaquin River, looking upstream

San Joaquin River, looking upstream
(Photograph by Cathy Munday, U.S. Geological Survey)

Photograph of the San Joaquin River, showing sampling for trend assessment

Photograph of the San Joaquin River, showing sampling for trend assessment

San Joaquin River, showing sampling for trend assessment
(Photograph by Jason May, U.S. Geological Survey)