Evaluation of ground-water nitrate and organic carbon inputs to the lower San Joaquin River and their sources

Nitrate and organic carbon levels in the San Joaquin River (SJR) are of concern to the Central Valley Regional Water Quality Control Board (Regional Board) and to the CALFED Drinking Water Quality Program (DWQP) because of their impacts on the cost and effectiveness of water treatment for drinking water and on the dissolved oxygen levels in the Stockton Deep Water Ship Channel (DWSC). Nitrate and organic carbon are pollutants of concern for the CALFED DWQP and this study addresses one of that program’s top priorities: monitoring, assessment, and research projects that increase our understanding of sources, transport, transformation, and fate of the CALFED drinking water quality pollutants of concern. This study also addresses several of the Regional Board priority projects including the development of a Total Maximum Daily Load (TMDL) for the low dissolved oxygen in the Stockton DWSC. It appears that ground water could be a major source of nitrate to the SJR, supporting algae growth that can eventually lead to water treatment concerns and to oxygen depletion in the Stockton DWSC. This oxygen depletion in the Stockton area can be deleterious to Chinook salmon migration. This study was designed primarily to address the issue of nitrate sources to the SJR; organic carbon will be analyzed at the same time to further define its sources to the SJR. The study area for this project is the SJR from just upstream of the confluence of Salt Slough to the new California Department of Water Resources (DWR) water quality sampling site near Vernalis, about 60 river miles.

If you have questions or comments related to this study, contact: Charles R. Kratzer (ckratzer@usgs.gov) or write: