Lawrence Berkeley National Laboratory

Salt management has been a challenge to westside farmers since the rapid expansion of irrigated agriculture in the 1900 s. The soils in this area are naturally salt-affected having formed from marine sedimentary rocks rich in sea salts rendering the shallow groundwater, and drainage return flows discharging into the lower reaches of the San Joaquin River, saline. Salinity problems are affected by the imported water supply from Delta where the Sacramento and San Joaquin Rivers combine. Water quality objectives on salinity and boron have been in place for decades to protect beneficial uses of the river. However it was the selenium-induced avian toxicity that occurred in the evaporation ponds of Kesterson Reservoir (the terminal reservoir of a planned but not completed San Joaquin Basin Master Drain) that changed public attitudes about agricultural drainage and initiated a steady stream of environmental legislation directed at reducing non-point source pollution of the River. Annual and monthly selenium load restrictions and salinity and boron Total Maximum Daily Loads (TMDLs) are the most recent of these policy initiatives. Failure by both State and Federal water agencies to construct a Master Drain facility serving mostly west-side irrigated agriculture has constrained these agencies to consider only In-Valley solutions to ongoing drainage problems. For the Westlands subarea, which has no surface irrigation drainage outlet to the San Joaquin River, innovative drainage reuse systems such as the Integrated Farm Drainage Management (IFDM) offer short- to medium-term solutions while more permanent remedies to salt disposal are being investigated. Real-time salinity management, which requires improved coordination of east-side reservoir releases and west-side drainage, offers some relief to Grasslands Basin farmers and wetland managers - allowing greater salinity loading to the River than under a strict TMDL. However, current regulation drives a policy that results in a moratorium on all drainage return flows.