Tracking California’s water supplies

The American Southwest recently experienced its driest period in 1,200 years. Storms in the winter of 2023 eased some of California’s extreme drought conditions, but officials stress that conservation should remain a way of life.

This page tracks urban water use, hydrological conditions, precipitation, the Sierra snowpack and the largest reservoirs serving the state.

California’s worsening droughts

California naturally cycles between wet periods and droughts. But scientists have found that globally climate change is intensifying the water cycle and bringing more extreme droughts, as well as more extreme bouts of wet weather.

The graphic below shows the intensity and duration of droughts and wet periods since the 1980s. Over the last decade, the state has endured more frequent and severe dry periods punctuated by fewer wet years.

How much rain and snow has fallen in California?

Precipitation is tracked the across the “water year,” beginning Oct. 1 and ending Sept. 30.

As of Nov. 25, the state has received 4.6 inches of precipitation, or 135% of the average for this date.

California typically sees most of its rain and snow during the first half of the water year, which is followed by the warmer and drier spring and summer. The graphic below shows daily precipitation totals since 2000 for the state and its major drainage basins, or hydrologic regions.

How much water is your area using?

State regulators track water use in cities and towns, collecting monthly data from more than 400 urban supplies that serve about 37.2 million Californians.

Residential water use is typically measured in gallons per person per day, a metric called R-GPCD. During the drought emergency beginning in June 2021, Californians were asked to reduce water use by 15%. In the 21 month period that followed, residents managed to cut back by about 7%, reducing water use to an average of 85 gallons per person per day. Since then, residential water use has averaged about 82 gallons per person per day.

On the heels of the most recent drought, the state has enacted a new water conservation framework tailored to each water supplier, requiring some agencies to cut usage by more than 30% by 2040.

The map below shows residential water use and the total drinking water supply by utility for the month of September. In that month, Californians used an average of 106.3 gallons of water per person per day.

Residential water use can vary widely across districts depending on factors such as local climate, yard size and population density. Generally, cities and towns in warmer regions, including inland areas, use more water while cooler areas use less. Water use typically increases in the summer months and declines as temperatures cool.

Use this tool to track residential water use trends over the past year for your local water supplier. (Your supplier is the utility that bills you for water.)

Or select from the largest urban water suppliers:

How much water does California have stored in reservoirs?

California has the ability to store nearly 40 million acre feet of water behind dams around the state. The state Department of Water Resources reports a regular accounting of the water levels at 154 reservoirs representing the vast majority of the state’s water storage capacity.

As of Nov. 24, state reservoirs stand at about 60% capacity. That’s above the 30-year average of 52% for the month of November.

Large Northern California reservoirs supply Southern California with much of its water. Below are the current levels for some of the major reservoirs, in order of total capacity.

Lake Mead and Lake Powell, the country’s largest reservoirs, lie beyond state borders but hold a significant amount of Colorado River water that is used by Southern California. Here’s where these reservoirs stand as of Nov. 24.

How dry is California?

The drought in California and the American West has been worsened by rising temperatures caused by climate change. Scientists in 2022 found that the region as a whole, from Montana to California to northern Mexico, experienced the driest 22-year period in more than 1,200 years.

Since 2000, the U.S West. has grown warmer and drier. Data from the U.S. Drought Monitor shows that the region has plunged deeper into extreme drought over the past several years. Scientists have increasingly said the West is experiencing “aridification” driven by human-caused climate change, and they have called for the region to prepare for drier conditions in the long term as temperatures continue to rise.

Compared with 2021, conditions in the U.S. have worsened. About 78% of the country is at least abnormally dry, according to the drought monitor.