The California Regional Water Quality Control Board, Central Valley Region (CVRWQCB) has been conducting water quality monitoring of the lower San Joaquin River and the wetland channels and principal sloughs within the Grassland Basin since 1985. The data gathered has been used in developing regulatory programs for the control of agricultural subsurface drainage discharges to surface waters. It is anticipated that this effort will continue in the future, primarily for the purpose of monitoring for compliance with the Water Quality Control Plan for the Sacramento and San Joaquin River Basins (Basin Plan).

The CVRWQCB will conduct the water quality monitoring portion of the GBP, as the CVRWQCB and the GBP have common objectives and overlapping sampling areas.