The State Water Project is an aquatic lifeline for California because of its vital role in bringing water to cities and farms. Without it, California would never have developed into the economic powerhouse it is.

The State Water Project diverts water from the Feather River to the Central Valley, South Bay Area and Southern California. Its key feature is the 444-mile long California Aqueduct that can be viewed from Interstate 5.

Today, about 30 percent of State Water Project water is used for irrigation, mostly in the San Joaquin Valley, and about 70 percent is used for residential, municipal and industrial use, mainly in Southern California but also in the Bay Area.

State Water Project Overview

Built and operated by the California Department of Water Resources, the SWP is the largest state-financed water project ever built.

State Water Project achievements include:

• fueling Southern California’s population and economic growth;
• supplying Silicon Valley with reliable, high-quality water vital to high-tech manufacturing
• boosting California’s agricultural industry to be among the global leaders
• helping manage floods in the Sacramento Valley
• and providing recreational opportunities at many of its reservoirs;

As prominent as the SWP is today, its creation took many decades and considerable political and engineering efforts.

Take an aerial tour of the State Water Project.

State Water Project Background

Proposals with elements similar to the SWP date back to the 1880s, but the political consensus and financing needed to build the project was not secured until the late 1950s. Even then, the SWP faced formidable engineering obstacles, including the highest water lift in the world over the Tehachapi Mountains south of Bakersfield.

The SWP originally was conceived as a much larger project, but only its first phase was completed. Even so, more than 40 years after voters approved funding for that first phase, the SWP is a vital part of California’s infrastructure.

But water practitioners are divided over its future direction.

Learn more about the history of the State Water Project.

State Water Project and the Future

Contractors who buy water from the project generally favor operation of facilities so it can deliver all the water it was designed to handle, but critics argue that operating the SWP at full capacity will stimulate further growth and further harm the environment.

For instance, the State Water Project and (federal) Central Valley Project export pumps are located at the south edge of the Sacramento-San Joaquin River Delta. As a result, there is ongoing concern about protecting the Delta’s ecosystem, and the levees protecting various islands, pumps (fish protection does limit pumping at certain times of the year) and a host of other infrastructure.  Scientists also say there is a major threat of Delta levee failure from an earthquake or flooding, which would have significant impact on SWP operations and California’s water supply.

Similarly, the need for short-term and lasting actions was demonstrated in 2007 when SWP Delta pumping operations were forced to a halt because of the threat to Delta smelt — a tiny fish that is recognized as a key component of the Delta’s ecological food web. Pumping restrictions also are contemplated to protect declining populations of Chinook salmon.

With these issues in mind, officials are seeking a permanent solution to the water export/endangered species conflict through the Bay Delta Conservation Plan, a collaborative effort by state, federal and local agencies and environmental organizations. Possibilities include alternative means of water transport, habitat restoration such as the proposed twin tunnels Delta conveyance project and management.

In addition to environmental concerns, the SWP faces financial challenges as its aging facilities require increasing maintenance and upgrades to maintain reliability.

Furthermore, demand for its water is expected to increase in future years to meet the needs of California’s growing population, which is forecast to approach 50 million by 2025.

State Water Project Facts and Figures

• built to deliver about 4.2 million acre-feet of water per year
• annual water deliveries to 29 public agency contractors that buy SWP water
• averaged 2.8 million acre-feet in deliveries over the last decade, with a high water mark of 3.7 million acre-feet in 2006
• main aqueduct is 444 miles in length
• the SWP provides supplemental water for 25 million Californians and irrigation water for an estimated 750,000 acres of farmland