California's Water: California Water Systems

California is home to one of the most extensive water supply systems in the nation. Comprising more than 1,000 reservoirs, hundreds of groundwater basins and dozens of local and regional water conveyance systems, California’s water infrastructure is an engineering marvel and a tribute to human ingenuity.

 

This segment of “California’s Water” focuses on the state’s vast water supply network and its importance to our economy, environment and lifestyle. It takes viewers on a tour of key facilities and explores the role local and regional water management efforts play in meeting California’s water needs. 

 

Background 

 

California relies on an elaborate network of water storage and delivery systems to supply cities, farms, businesses and the environment with adequate water year-round. Given the state’s highly seasonable precipitation and the fact that annual runoff can vary widely from year to year, water supply infrastructure has allowed California to grow and prosper by storing and moving water when and where it’s needed.

 

Nature provides about 200 million acre-feet of precipitation to California in average years. Of this total, 65% is lost through evaporation and transpiration by trees and other plants. The remaining 35% stays in the state’s system as runoff. More than 30% of this runoff flows out to the Pacific Ocean or other salt sinks. The rest is used by agricultural, urban, and environmental purposes. 

 

About 75% of the annual precipitation falls north of Sacramento, while more than 75% of the demand for water is south of the capital city. Most of the rain and snowfall occurs between October and April, while demand is highest during the hot and dry summer months

 

California’s water system was developed to address that mismatch. Seven major systems of aqueducts and associated infrastructure exist today to capture and deliver water within the state. Two of the most important projects are the federal Central Valley Project (CVP) and the State Water Project (SWP). The CVP and SWP bring water from Northern California through the Sacramento-San Joaquin River Delta for delivery to users in the San Joaquin Valley, parts of the San Francisco Bay Area and Southern California

 

Key water projects and the amount of water they deliver:

 

Local water agencies play an important role in delivering water to California’s communities, farms and businesses. Some purchase water from the major state and federal projects, treat the water as needed and deliver it to their customers. Others act as wholesale agencies that buy or import water and sell it to retail water suppliers.

 

Some agencies operate their own local water supply systems, including reservoirs and canals that store and move water as needed. Many agencies rely on groundwater exclusively, and operate local wells and distribution systems.

 

In recent decades, local agencies have developed more diversified sources of water supplies. Many agencies use a combination of imported surface water and local groundwater. They also produce or purchase recycled water for use in irrigating golf courses and other landscaping.

 

California's rapidly growing population -- estimated to reach 48 million by 2030 -- is putting mounting pressure on the state’s water supply system. Local and state water managers agree that investments are needed to ensure that California has the water supply system it will need in the future.