Snowpack, Snowmelt and Southern California Drinking Water

California’s drought remains at the forefront of events affecting residents, businesses and government throughout the State. Included in the topic of drought, Californians continue to hear about concerns with snowpack levels. Substantial snowpack is the determining factor to end the drought. With more than four years in a drought and the State’s major reservoirs are holding less than historical averages in non-drought years, snowpack with high water content is essential to replenish groundwater supplies and fill reservoirs.

“Our climatologists predict that the State would need snowpack to be approximately 50-percent over the average to end the drought in a single year. It is possible that more than one year with lesser amounts could end the drought; it depends largely on how long it takes to build up reservoir storage. Currently, we are nowhere near that number,” shared California Department of Water Resources (DWR), spokesperson Paul Carlson. Without an abnormally wet spring season, the chances of ending the drought this year appears unlikely.

Were does Southern California drinking Water come from?

Southern Californians on a public or private water service receive water from local groundwater supplies, the California State Water Project and the Colorado River. The majority of the Colorado River water and State Water Project water originates from snowpacks.


How does snowpack affect our local groundwater supply?

First, what is snowpack? Snowpack is an accumulation of layers of snow at high altitudes with colder temperatures. As the snowpack melts, it becomes snowmelt. Snowmelt is the source of water for lakes and rivers, which can eventually be treated and becomes drinking water. Without sufficient snowpack, there is not enough runoff in rivers and lakes; drinking water supplies run low and there is a problem with scarcity.

Snowmelt is also responsible for helping to maintain a healthy water supply. Because it is low in salt content, this fresh water source aids in providing a pure water source for our drinking water supplies, which eventually make their way to our homes.

“The quality of the water along the Santa Ana River is excellent at the foothill line,” states Maury Roos, DWR hydrologist. “Total average runoff in the basin is around 300,000 acre- feet*, including San Jacinto River water. Approximately, 10-percent comes from snowmelt from higher mountains in the watershed.”

According to the California Department of Water Resources, snowpack supplies are responsible for 30–percent of California’s water needs. While this year’s storms have brought more snowpack than in previous years, the State is still far from seeing an end to the drought. Current heat waves have melted much of the winter snowpack.


While water agencies do not separate snowmelt from total runoff, snowmelt becomes part of the streamflow by combining with runoff. In Southern California, the water pumped from the Delta is a blend of surface runoff and snowmelt, and also indirectly mountain basin groundwater.

“With the prospects looking more likely that California’s drought soon will be acknowledged to be five years long, it is imperative for Californians to adopt a new water ethic that values water conservation. Watering more than a day a week is probably wasteful, and there is a prohibition against watering within 48 hours of rainfall,” stated Carlson.


When you turn on your tap to enjoy a drink of water, take a shower, wash a load of laundry or irrigate your yard, a portion of the water that comes from the tap has likely come from snowmelt. Remember to protect our precious water resources. Water, use it wisely.

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* One acre-foot of water is equivalent to 325,851 gallons of water.

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