GETTING THE SALT OUT – THE SAN JOAQUIN RIVER SALINITY AND BORON TMDL

Water quality objectives for salinity, to protect agricultural water supply use, are currently being exceeded in the San Joaquin River. The Central Valley Regional Water Quality Control Board has drafted a TMDL for salinity in the Lower San Joaquin River, which could actually lead to increases in salt concentrations in the future. Because the TMDL allocation is based on loadings versus concentrations, and because load reductions are achieved by eliminating lower-concentration sources, the end result would exacerbate existing salinity problems. The load-based TMDL would also concentrate salt within the Central Valley, rather than continuing to export sufficient quantities of salt needed to maintain a sustainable salt balance. An alternative approach, basing the TMDL allocation on salinity concentrations, has been proposed. A concentration-based approach would focus efforts on reducing the highest concentration sources of salinity throughout the watershed, would lead to real improvements in downstream water quality, and would be a more transparent, more directly monitored approach to comply with salinity objectives.