Water Information

Water is an essential resource. Without it, taps run dry, streams stop flowing, businesses suffer and crops die.

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. The systems are necessary because California’s Mediterranean-style climate means we receive little or no rain for months at a time. The ability to store and move water has made it possible for California to grow and prosper.

Precipitation varies from place to place, season to season, and year to year. Most of the state’s rain and snowfall occurs in the northern part of the state, while most of the demand for water is along the coast and in the valleys to the south of Sacramento. California receives most of its rain and snowfall between October and April, though the highest demand for water is in the hot, dry summer months.

California’s water system was developed to address that variability. Two important projects in that system are the State Water Project (SWP) and the federal Central Valley Project (CVP). The SWP and the CVP 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.

Challenges to our water supply system

Though this system has served California well in the past, it faces a number of challenges that threaten the reliability of its water supplies.

Ecological problems in the Delta

The Sacramento-San Joaquin Delta, the hub of our state’s water system, is in an ecological collapse that has triggered major cutbacks in water deliveries for many areas of the state and continues to threaten the state’s economy and species such as salmon and Delta smelt.

Growing pressure on our water delivery system

Constructed primarily in the mid-20th century, the state’s water infrastructure is struggling to keep up with the state’s population growth as well as new environmental requirements to protect species and habitats.

Climate change

Experts agree that long-term climate change is occurring and that it is already affecting California’s water resources. Warming temperatures, changing rain and snowfall patterns and rising sea levels will profoundly affect the state’s ability to manage water supplies and other natural resources.

Dry conditions

California is prone to frequent dry spells, the most recent running from 2007 to 2009. Rain and snowfall returned to average in 2010, but water deliveries were still reduced for many areas of the state due to a variety of factors. Though the 2012-'13 precipitation season got off to a good start, dry conditions in January through March have many water agencies on alert. 


In November 2009, the California Legislature passed a package of water-related bills aimed at addressing the state’s water problems. Arguably the most significant water legislation in 50 years, the package included new bills on Delta governance, conservation, groundwater monitoring and water rights enforcement as well as an $11.14 billion water bond now slated for the November 2014 ballot to implement the new policies.

The package puts California on a path to long-term solutions, but many of its elements will take years to implement.

In the meantime, local water agencies continue to invest to local and regional programs such as water conservation, water recycling, groundwater storage and other strategies to diversify water sources and improve reliability.