In 1991 the U.S. Geological Survey initiated the National Water-Quality Assessment (NAWQA) Program. The long term goals of this program are to assess the status of and trends in the quality of freshwater streams and aquifers, and to provide a sound understanding of the natural and human factors that affect the quality of these resources. As part of the program, investigations are conducted within "study units" throughout the Nation to provide a framework for national and regional water-quality assessment.

The San Joaquin-Tulare Basins(SANJ) study unit, located in central California, was a part of the first decadal cycle of the program investigations. The SANJ intensively investigated the quality of water resources in the study unit in order to establish existing water quality conditions of streams and aquifers. A summary of the first cycle findings can be found in Dubrovsky and others (1998).

Stanislaus River
(Photograph by Larry Brown, U.S. Geological Survey)

Beginning in October 2001, and continuing for a period of 4 years, the NAWQA Program will again intensively investigate the quality of water resources in the San Joaquin-Tulare Basins, as part of the second decadal cycle of the program. While the long term goals remain the same, the emphasis of these renewed investigations will shift from status of water quality to trends in water quality and understanding of natural and anthropogenic factors affecting water quality. These activities are described in Gronberg and others (2004).

If you have questions and comments related to the San Joaquin-Tulare Basins NAWQA study, contact: Charles R. Kratzer (ckratzer@usgs.gov) or write: