SAN FRANCISCO
01/30/2013 11:56 am ET | Updated Apr 01, 2013

Sierra Nevada Snowpack Shrinks With Dry January

A dry January dramatically shrank the snowpack across the Sierra Nevada, raising concern for a water supply vital to California farms and cities.

The state Department of Water Resources conducted field measurements of the snowpack at various locations on Tuesday and found it to be 93 percent of average for the date.

While not troubling in itself, that number means California lost a water supply advantage from a wet December that left the snowpack at 134 percent of average, and is now tracking close to average conditions.

Precipitation in January across the Northern Sierra -- a region crucial to statewide water supplies -- was just 13 percent of average as of Monday. The dry weather pattern is expected to hold, likely ranking the month as the driest January since 1991, according to DWR data.

The state essentially missed out entirely on what is normally the wettest month of the year.

"California's variable precipitation is a constant threat to our water supplies and an ongoing reminder for all of us to use only the water that we need," said Amy Talbot, water efficiency program manager at the Sacramento Regional Water Authority.

For now, water storage reservoirs are in good shape for this time of year, thanks to that wet December. Folsom Lake on the American River currently holds 110 percent of average water volume for the date, while Shasta and Oroville reservoirs are at 111 percent and 113 percent, respectively.

The state's summer water needs are normally met by the snowpack as it stands April 1 each year. As of now, the snowpack is only 55 percent of the April 1 average.

Melting snow can't be fully captured in winter because reservoirs must maintain storage space for potential floods.

The National Weather Service's Climate Prediction Center, in a forecast released Jan. 17, indicated below-average precipitation is likely for the balance of winter across the state.

Contact The Bee's Matt Weiser at (916) 321-1264 or via Twitter @matt_weiser. ___

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