WA10 TMDL and Monitoring Programs for the San Joaquin River Basin (USA)
D135-136
8:00 AM - 12:00 PM, Wednesday
() Challenges and opportunities for implementing a Total Maximum Daily Load (TMDL) for salt and boron in the lower San Joaquin River.
Oppenheimer, E1, Grober, L1, 1 California Regional Water Quality Control Board, Central Valley Region, Sacramento, California, United States
ABSTRACT- The salinity impairment in the San Joaquin River (SJR) has occurred as a result of large-scale water development projects coupled with extensive agricultural land use and associated agricultural discharges. Establishment of a TMDL for salt and boron is challenging because these substances occur naturally in soil and groundwater of the region and large quantities of salt are imported to the watershed in irrigation supply water. Though regulation of drainage can be used to require reductions in salt loading to the river, modeling results, show that the salinity problem will persist even if all discharges are eliminated. Additionally, implementation of a conventional TMDL with static load allocations would require dischargers to retain salt on site, resulting in a net build up of salts in the soil and groundwater. The salinity problem can therefore only likely be remedied by implementing a combination of actions that include drainage controls, coordinated management of freshwater flows and saline discharges, and improvements in municipal and agricultural water supplies. The California Regional Water Quality Control Board, Central Valley Region (Regional Board) has the authority and responsibility to develop TMDLs for the SJR and other waterbodies in California's Central Valley. The Regional Board has broad authority over discharges to surface water but does not have authority over water rights, precluding it's ability to directly implement some of the actions needed to solve the salinity problem. A multi faceted implementation program has been proposed to overcome this institutional constraint. In it, dischargers would be allowed to participate in a stakeholder driven river management program, using the tools beyond the purview of the Regional Board, to solve the salinity problem in lieu of complying with static load allocations (limits). Conventional TMDL load allocations are proposed as a regulatory backstop to assure that alternative actions are taken in a timely fashion.
Key words: drainage, agriculture, TMDL, salinity