Global Warming
Decreased Snowmelt Poses Threat to Sierra Water Supply
Why is it important?
Global warming has affected the amount of snowmelt in the Sierra Nevada since 1950.
Precipitation in the form of snow, rather than rainfall, increases water availability originating from the Sierra Nevada by delaying water flows downstream into spring and summer months when water, particularly for agriculture, is needed most. Snowmelt water provides about 75 percent of the water supply in the western United States.19 It increases water storage and groundwater recharge capacity. Amount of snowmelt is affected by changes in snow precipitation, percolation, and evaporation. A reduction in snow precipitation and percolation is influenced by the global warming environmental effect.
How are we doing?
In the map, red circles indicate decreasing snowmelt water and blue circles indicate increasing snowmelt. Circle size indicates percent increase or decrease. The map shows that snowmelt has decreased more than 80 percent in some areas of the northern Sierra Nevada, while snowmelt has increased in the southern Sierra Nevada since 1950. Global warming has undoubtedly impacted these statistics, and will continue to do so in the Sierra Nevada and other regions of the Western United States in the years to come.
19 Mote, Philip. The West’s Snow Resources in a Changing Climate. Testimony before the U.S. Senate Committee on Commerce, Science, and Transportation. May 6, 2004.
