Climate Fact: Spring Snowmelt in the West
About 75 percent of the West’s water resources originate in snowpack. Most precipitation in the region occurs during the winter, the period of the year when the reservoirs are replenished after the dry summer and early fall months. The reservoirs are at their high points in the spring. Traditionally, snowpack would last into the late spring and summer months, and not overwhelm the already full reservoirs in the early to mid-spring. Since the 1950’s however, there has been a steady trend of earlier snowmelt across the West, causing the rivers to start their spring snowmelt “pulse” sooner. If the rivers peak too soon, in order to keep the dams from breaking water from the reservoirs must be discharged instead of being conserved for the summer months. In some parts of the West, the average date of the start of the spring streamflow “pulse” is now happening over 20 days earlier than it did in the 1950’s.
To see how spring snowmelt timing has changed in your local area since the 1950’s, visit http://www.earthgauge.net/climate-facts-image-library#9. This image is featured in the “Global Climate Change Impacts in the United States” report recently published by the U.S. Global Change Research Program. The image is in the public domain.
Seasons: Spring
Source: Global Climate Change Impacts in the United States, Thomas R. Karl, Jerry M. Melillo, and Thomas C. Peterson,(eds.). Cambridge University Press, 2009