Restrictions intended to protect native fish in the Delta, imposed under the Endangered Species Act, have had significant effects on water exports over the past four years, under both wet and dry hydrological conditions.

The charts below show the allocations for the Central Valley Project south of the Delta (CVP) and State Water Project contractors (SWP) and the water losses in the Delta over the past several years.


CVP allocations

Water loss due to BiOps
As the chart above shows, in recent years when water supplies were scarce, hundreds of thousands of acre feet of water was required to be flushed out to the ocean while water contractors received only a fraction of their contracted amounts. So far this year, impacts have been minimized by high flows on the Sacramento and San Joaquin rivers. 

History of Water Supply Restrictions

  • 1991 – Endangered Species Act – Winter Run Salmon Temperature Control
  • 1992: Central Valley Improvement Act
  • 1994: Endangered Species Act – Delta Smelt Biological Opinion
  • 1995: Water Quality Control Plan/Clean Water Act
  • 1997: Anadromous Fish Restoration Program
  • 2000: Trinity Restoration Plan
  • 2008: Delta Smelt Biological Opinion
  • 2009: Salmon Biological Opinion