Dwindling California Snowpack is a Warning of More Dire Water Challenges to Come
Posted March 31, 2014
California’s annual April snow survey results, which provide an indicator of how much water will flow into streams and rivers during the dry summer and fall months, will be announced tomorrow by the Department of Water Resources. With drought conditions affecting more than 99 percent of the state, this year’s April snowpack measurement is likely to be the lowest since 1988.
Although this year’s low snowpack is due to drought, warmer temperatures from climate change are expected to dramatically reduce April snowpack in the future, jeopardizing important seasonal water supplies for farms and cities throughout California in the long-term.
Snowpack is an important component of California’s water supply because the melting of Sierra Nevada snowpack in late spring and early summer fills reservoirs in advance of the dry summer and fall months. This snowpack normally stores 15 million acre-feet of water —that’s more water than California cities used in 2010—and provides one-third of the water used by cities and farms each year. The April snow survey is particularly important because it generally represents when snowpack is at its peak—what we have at the beginning of April typically is all we’re going to get.
Snowpack in the Eastern Sierra Nevada in May 2013 (photo credit: Pete Davis)
The snowpack measured so far this year has set records for how scarce it has been. At the beginning of February, the snowpack was only 10 percent of the average for that time of the year (the lowest reading since World War II). Significant precipitation during February improved snowpack conditions, but they still represented only 20 percent of the average. While recent snow showers may help to avert a record-breaking low for snowpack, this year’s April snow survey will still rank far below normal.
We should get used to seeing less winter snowpack because of climate change. Here are the projections:
- By 2050, California snowpack is projected to decline by 25 to 40 percent compared to historical averages.
- By 2100, estimated reductions of 50 to more than 75 percent are expected for April 1 snowpack.
- Further, new research indicates the state is likely to see 5 to 10 fewer days of precipitation each year.
- Warmer temperatures from climate change also are expected to change streamflow patterns by causing peak runoff to occur earlier in the year.
In fact, California just experienced the warmest winter on record. Earlier shifts in runoff lead to higher flood risks as more winter precipitation falls as rain than snow, and it also reduces the water available in the summer and fall to meet agricultural, industrial, and municipal water needs.
All of these changes have wide-ranging implications for water users in California, including those cities and farmers that divert water from rivers upstream of the Delta as well as those that rely on the state’s two major water supply networks, the State Water Project (SWP) and the Central Valley Project (CVP), which receive water from river basin systems fed by snowmelt. SWP exports predominantly go to urban areas in Southern California and the Bay Area, with the remainder going largely to agricultural users in Kern County. And the CVP exports from the Delta primarily go to agricultural businesses in the San Joaquin Valley, with smaller deliveries to the Santa Clara Valley Water District and wildlife refuges. Collectively, the SWP and CVP provide a portion of the water for more than 25 million people and more than 3.6 million acres of farmland in California, although the total water exported from the Delta by the SWP and CVP only accounts for about 8 percent of the state’s water supply.
The critically-low snowpack this year is primarily responsible for the record low water supply allocations affecting SWP and CVP contractors as well as upstream users. The lack of snowpack also will have big impacts on the state’s fisheries and wildlife because of low river flows, very dry conditions for terrestrial species and plants, and higher risk of wildfires.
Because many areas in the state depend on largely unsustainable water supplies, such as exports from the Delta and/or the Colorado River as well as groundwater over-extraction, we must invest in sustainable water solutions. Please see my colleague Doug Obegi's blog for more details on these solutions. Instead of relying on outdated infrastructure-heavy approaches like expensive new reservoirs, cost-effective, sustainable water management measures such as urban and agricultural water efficiency, water recycling, better groundwater management, and green infrastructure will better prepare our communities for a future with greater water insecurity. With investments in these wise water solutions, we can reduce our reliance on imported water and create resilient water supplies for decades to come.
As we face increasingly dire water challenges from climate change, these solutions will help to ensure cost-effective, reliable, and adequate water supplies for the next generation of Californians.
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