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Benefits Of The California State Water Project

The SWP’s main purposes are to provide water storage and delivery. Its supply comes mainly from rainfall, snowmelt runoff, and excess flows in the Delta during wet years.

SWP water is delivered to contracting agencies (97K pdf) in Northern California, the San Francisco Bay area, the Central Coast, San Joaquin Valley, and Southern California. The water supplements surface and groundwater resources for most of these agencies.


The State Water Project requires dependable, economical power to pump water to areas served by the Project’s contractors. Since 1984 SWP power requirements have ranged from more than 8 billion kilowatthours a year, as in 1990, to under 4 billion kwh, as in 1995.

To provide some of that power, DWR included a system of power and power recovery plants in the system. In 1983, the Department became a bulk power utility, capable of selling, exchanging, and purchasing energy from other utilities. Other energy sources come from long-term contracts with other utilities and joint development of facilities such as Castaic Powerplant on the West Branch.

Today the SWP is one of California’s larger energy producers and a major consumer of electricity. How much power SWP facilities consume depends on contractor requests for water and the amount of water available for delivery.

In an average water supply year, SWP hydroelectric power plants and a partially SWP owned coal-fired plant in Nevada produce about 5.9 billion kwh. Of that total, 4.5 billion kwh come from hydroelectric generation.

When SWP power requirements are less than power resources, the Department sells surplus power to help defray the cost of water deliveries.

The SWP’s flexible pumping operations helps it to manage its power needs. This flexibility is allowed by Project reservoirs, which temporarily store water until it is needed to meet the daily and seasonal demands of its contracting agencies.

To reduce power costs, pumping is minimized during on-peak hours when power prices are highest. Maximum pumping is scheduled during off-peak periods (nights, weekends and holidays) when power costs are cheaper. Thus the SWP can purchase, when needed, inexpensive surplus generation from other power suppliers for its pumping operations.

The Project also can sell surplus power when its power needs are less than its resources. The revenue from these sales helps keep the net cost of water deliveries affordable.

Flood Control

Oroville Dam Spillway
Oroville Dam Spillway

One of the SWP’s primary functions is flood control in Northern California. A major flood in 1955 was the impetus for the construction of Lake Oroville.

Storage space is provided in Oroville and Lake Del Valle to capture flood flows and protect areas downstream. Releases are coordinated with other flood control reservoirs so flows stay within downstream channel capacities.

Floodwater storage space in SWP reservoirs is paid by the federal government, which regulates how the reservoir space is managed during the rainy season.

Fish and Wildlife Protection

Fish Screen
Fish screen research in the Delta

The Project is operated to protect the environment. Restricted pumping schedules, fish hatcheries, fish screens and passages, mitigation agreements, fish surveys and monitoring, a fish salvage facility, and habitat restoration, are some of the mechanisms for fish and wildlife protection. The projects are also operated to meet instream flow requirements in the Feather River, the Sacramento River, and Delta channels.

The State Water Project, in cooperation with the federal Central Valley Project, is operated to limit salinity intrusion into the Sacramento-San Joaquin Delta and Suisun Marsh. This is accomplished by supplementing freshwater outflows to the ocean and limiting water exports from the Delta during specific times of the year.

DWR spends about $20 million annually for various studies, habitat restoration projects, and fish monitoring programs. These costs also include water deliveries lost to pumping reductions (during fish migrations through the Delta) and other operational restrictions.

The Department’s environmental specialists coordinate with fish and wildlife agencies to investigate the impacts of SWP operations on the Sacramento-San Joaquin Delta.


SWP Lake
SWP lakes offer a variety of recreational activities.

Plans to construct the SWP included recreational facilities. At Project lakes and reservoirs, visitors will find opportunities to swim, picnic, waterski, boat, fish, hike, bike, camp, and horseback ride.

Visitors are also welcomed at three visitors centers located at Lake Oroville, San Luis Reservoir, and Lake Pyramid. At each center, exhibits, videos, and friendly guides tell the story of the State Water Project and its facilities. Admission is FREE.