The Central Valley Regional Water Quality Control Board has listed the San Joaquin River Deep Water Ship Channel (DWSC), located near Stockton, California, as "impaired" under the Clean Water Act.

The dissolved oxygen concentrations in the DWSC routinely fall below the Board's water quality standard during periods in the late summer and early fall of each year, especially in the eastern portion of the channel.

The cause of the dissolved oxygen sag is related to low San Joaquin River inflows, warm water temperatures, and reduced tidal mixing that occur in combination with high biological oxygen demand. Low dissolved oxygen concentrations cause physiological stress to fish and can block upstream migration of salmon in the SJR.

The Regional Board has required that a total maximum daily load (TMDL) for the DWSC be developed for controlling the DO problem.

The structured field experiments, data collection/analysis, scientific reports and modeling provided by this project will yield a detailed understanding of how hydrodynamic and biogeochemical processes interact to produce reductions in dissolved oxygen concentrations along the San Joaquin River.

This in turn will provide a basis for the development of management options. This work is being conducted in collaboration with Stanford University, the US Geological Survey and UC Santa Barbara.