California Water Project: Why Built & Its Delta Impacts

The State Water Project (SWP), authorized 1951, completed 1993, moves Sierra snowmelt from the Feather River watershed south via the Sacramento–San Joaquin Delta to 27 million people and 750,000 acres of farmland.

Why It Was Built

• Post-WWII boom: Southern California population exploded; local water insufficient.
• Central Valley agriculture: Needed reliable irrigation for high-value crops.
• Flood control: Oroville Dam regulates Feather River.
• Hydropower: 8 generating plants, 3.2 GW capacity.

Delta Effects (Sacramento–San Joaquin)

Mitigation & Controversy

• Biological Opinions (USFWS/NMFS) limit pumping windows.
• Delta tunnels (Delta Conveyance Project) proposed to bypass Delta — litigated.
• EcoRestore: 30,000 acres tidal habitat restoration.
• Voluntary Agreements: flow + habitat + science governance.

Bottom Line

SWP enabled modern California but fractured the Delta’s ecology. The fix — if any — remains the state’s defining water fight.