The Delta is California’s most important water supply hub.  About two-thirds of all Californians and millions of acres of prime farmland rely on the estuary for water deliveries.  Water delivered by the State Water Project and Federal Central Valley Project serves both urban and agricultural areas from the Bay Area and Silicon Valley to the San Joaquin Valley and Central Coast and most of Southern California. Reservoirs and snowpack are a critical component to this system and are constantly effecting water supplies to these urban and agricultural areas. 

Environmental issues in the Delta have continued to make water deliveries to these key areas of the state more and more unreliable. 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 decade, under both wet and dry hydrological conditions. Even after a years with historically wet winters, like in 2017, allocations are disappointingly low the following years.

The State Water Project has not received a full allocation since 2006. 

The charts below shows 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.

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

The Human Impacts Of California’s Water Cuts were explored by Dr. David Sunding and presented by the Southern California Water Committee.