Effect of Snowpack Changes in the Central Sierra Nevada on Water Supply Forecasts in the Truckee River Basin

TitleEffect of Snowpack Changes in the Central Sierra Nevada on Water Supply Forecasts in the Truckee River Basin
Publication TypeConference Proceedings
Year of Conference2008
AuthorsLea, J.
Conference Name76th Annual Western Snow Conference
Series TitleProceedings of the 76th Annual Western Snow Conference
Date PublishedApril 2008
PublisherWestern Snow Conference
Conference LocationHood River, OR
KeywordsRunoff forecasting, snow accumulation timing, Donner Summit, declining snowpack, water supply
Abstract

Water supply forecasts rely on a historic record of precipitation, snow and streamflow. The snowpack in the central Sierra Nevada has been measured each year since the early 1900s. Currently the USDA Natural Resources Conservation Service and the California State Cooperative Snow Survey program measure snow in the Sierra Nevada and keep long term records of the snowpack. These long-term records are a good indicator of seasonal precipitation in the building of the snowpack in the region. A statistical analysis of the snowpack record at Donner Summit compared to Tahoe City precipitation reveals a shift in the relation that occurred in the late 1970s. This change in the relation of the April 1 snow and cumulative seasonal precipitation in the area is statistically significant at the 99.9% level. Since the late 1970s, there no trend has been observed in annual precipitation amounts and annual streamflow volume on the Truckee River. However a decrease in the amount of cumulative snowpack on April 1 in comparison to the seasonal precipitation of October through March between these two sites has been observed. This indicates that from 1980 to 2007 there has been more rain than snow compared to the previous 43 years.

URLsites/westernsnowconference.org/PDFs/2008Lea.pdf