Science activity

The Grassland Bypass Project has been under waste discharge requirements (WDRs) since 1998. Historically, subsurface agricultural drainage water (tile drainage) and surface runoff (irrigation tail water) from the Grassland Watershed was discharged to the San Joaquin River through Salt Slough and/or Mud Slough (north). These two sloughs are tributary to the San Joaquin River and serve as the primary drainage outlets for the Grassland Watershed. With the start of the Grassland Bypass Project in 1996, all tile drainage from a 97,000 acre area known as the Grassland Drainage Area is consolidated and conveyed through San Luis Drain to Mud Slough, eliminating discharges of drainage water from the Grassland Drainage Area into Salt Slough and wetlands. Reducing selenium in wetland channels is the primary goal of the Project, as elevated concentrations of selenium have been documented to be hazardous to wildlife. The Project prevents discharge of subsurface agricultural drainage water into wildlife refuges and wetlands in central California . The drainage water is conveyed instead through a segment of the San Luis Drain to Mud Slough, a tributary of the San Joaquin River. The Project improves water quality in the wildlife refuges and wetlands, sustains the productivity of 97,000 acres of farmland, and fosters cooperation between area farmers and regulatory agencies in drainage management reduction of selenium and salt loading. The Project is operated by the Bureau of Reclamation and the San Luis & Delta-Mendota Water Authority (Authority).