California's Water Supply in the Time of Climate Change

Updated: May 24


When people think of California, images of deserts, beaches, and cities usually come to mind. While California has terrain ranging from low-lying deserts to snowy peaks, water remains a limited resource. Los Angeles, the most populous city in the state, has an average of 15.5 inches of rainfall per year, in contrast to a nationwide average of 30.21 inches. California’s precipitation is uneven, with 75% of California’s water coming from the northern third of the state. In contrast, 80% of water demand is in the southern two-thirds of the state. With a massive population that uses an average of 85 gallons of water every day, the question remains: where does California get its water?

In the face of such need, California has created an astonishing number of projects aimed to transform the state to provide for the millions of people that live there.

Photo by CA Department of Water Resources.

Usable freshwater in California comes from surface water and groundwater. Surface water comes from lakes and rivers, while groundwater is found in large underground aquifers. While California’s surface water, is quite concentrated in the ten major drainage basins of the Central Valley, infrastructure and water projects aim to effectively diffuse the water resources to the more populated regions of the state.

The push for statewide water development began in 1919 with Lt. Robert B Marshall, of the U.S. Geological Survey, who suggested carrying water from the Sacramento River system into Southern California. It took until 1931, however, for the engineer Edward Hyatt to produce the “State Water Plan” which listed all that would be needed for such an endeavor. The State Legislature soon approved the plan, and construction of the “Central Valley Project” began in 1935. The CVP is 400 miles long, and includes reservoirs, tunnels, power plants, lakes, rivers, and canals. Overall, the CVP provides water for 6 out of 10 of California’s agricultural counties.

Photo by Bill Dally via iStock.

The Colorado River Aqueduct was also constructed in the 1930s, processing over a billion gallons a day. 242 miles long, it runs from the Colorado River on the California-Arizona border to Riverside, California. The Colorado River Aqueduct was completely fundamental to the development of Southern California, including Los Angeles and San Diego.

As the state’s population continued to grow rapidly, other water projects soon followed. Despite worries about the environment and concerns on whether the state could follow its proposed budget, the Burns-Porter Act passed in 1960, making way for a water and power development and distribution system: the State Water Project. Today, it supplies water to 27 million people and 750,000 acres of farmland.

These massive, complicated water projects involved major construction and manipulation of California’s natural terrain. The environmental impacts of them soon became clear.

Photo by Chris Richard via Flickr.

The Colorado River is responsible for the water one in ten Americans use. Between 2000 and 2014, the river’s flow was 19% below the average flow between 1906-1999. There are two main reasons behind this depletion: climate change and overuse. Because of increasing temperatures and decreasing precipitation, the Colorado Basin has been in a drought for almost two decades.

Lawsuits against the California Department of Water Resources, which manages the California Water Project, claim that the California Water Project is killing fish. As water is pumped out of the north of the state, reduced habitat has led fish like the delta smelt to be on the brink of extinction.

The California Water Project consists of aqueducts, channels, tunnels, reservoirs, and pumps. To transport such a huge amount of water across California the CWP uses a lot of energy. In fact, the CWP emits about 4 million tons of greenhouse gases each year and is a contributor to climate change.

These are not new concerns. Before the passage of the State Water Project, Delta and San Francisco Bay area residents worried about how the project would affect water quality and habitability for fish and wildlife. Nevertheless, all of these water projects passed and were constructed, leaving us with the question, what can we do?

An individual can take small, everyday measures to reduce their water consumption, such as taking shorter showers or fixing leaks. There are potential options on the policy scale as well. As climate change’s effects only increase, water management tools such as water recycling and groundwater banking might perform much more efficiently in the future than more traditional water management like river diversions. Factoring energy use and its potential consequences into water management can lead to more eco-friendly development and management. Overall, future water policy must take into consideration its potential effects on the environment and climate change, while protecting water quality and levels for the millions of people that rely on it.