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CALIFORNIA SNOW LEVELS
Source: California Department of Water Resources; California Data Exchange Center; California Cooperative Snow Surveys; this statistic shows two key statistics describing the percent of snow water equivalents (i.e., moisture content in the snow pack): 1) as a percent of normal; and 2) based on the assumption of an April 1 “peak snow water accumulation” date.

Note: The most important characteristic of snow to water managers and hydrologists is its water content. However, depth is of interest to many people also. State data collection equipment measures the weight of the snowpack, and therefore its water content. New-fallen snow can range in density depending on the air temperature and intensity of the storm. In California, densities of 12% are common. This means that for every 10 inches of snow that accumulates, it will melt to a pool of water 1.2 inches deep. After snow falls, it settles and compacts. The snowpack gets less and less deep, but the snow doesn't melt or go anywhere. Rather, its density increases. Therefore, snow depth is a fleeting indicator of the snowpack. By obtaining a measure of the water content of the snow, which doesn't change unless more precipitation occurs or the pack melts, we have a good handle on how the rivers will react in the spring. After May, the snowpack melts due to both rainfall and the intense sunshine of late spring and summer, which is the principal melting energy source.

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CALIFORNIA RESERVOIR LEVELS
Source: California Department of Water Resources; California Data Exchange Center; Summary of Storage in Major Reservoirs; includes 158 reservoirs in California, North Coast, and Colorado River (Lake Mead, Lake Powell); these statistics show reservoir levels statewide, both as a percentage of average and a percentage of capacity as of December 31, 2008.

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