The California Cooperative Snow Surveys do perhaps the best analysis of Spring snowmelt. A glance at geography of the region can provide good reasons why. California is situated in a place where probably few people should live. It's dry (much is desert) and interspersed with mountains. Not the kind of mountains typically seen in the eastern U.S. - green and flourishing with vegetation. Because of the lack of moisture, water is a commodity, which should be shared & distributed wisely. Desalination is possible, but water resources are best used considering conservation and distribution using a series of rivers, dams, and reservoirs. The source of much of the water in the region is precipitation during the wet season (Winter), especially snow at high elevations. Several hundreds of inches of snow fall yearly, most at peaks of mountains. As stated very well by the snow survey people, snow for many Californians is an 'out of sight, out of mind' type of thing, yet greatly influences their lives. Though it all eventually melts at southern locations, Mount Shasta in the north is capped by a snow/ice glacier year round. Such locations can have a climate and weather of their own, as illustrated in an interesting article from long ago. Not so typical thundershowers can turn a beautiful location to a private hell for a day.
Snow surveys are very helpful to accomplish objectives stated above. Many methods are used to monitor water resources in snowpacks. These include gamma radiation remote sensing using aircraft, using snow sensors (snow pillows), and taking snow core samples. The California Cooperative Snow Surveys mainly do the latter 2, among other things. Snow core samples provide the most reliable data, good for verification of data measured using less reliable methods. A nice description of the a snow core survey is provided at the CSS WWW site. More than 300 snow courses are established in the Sierra Nevada and surrounding mountainous regions, from which various snow core samples are weighed monthly, mainly to determine snow water content. They are located to best determine contribution of snowmelt to river and reservoir systems. Over 100 snow sensors are distributed above major river systems, for continuous data availability. Such abundant data is very valuable for modelers, hydrological planners, and researchers. Current measurements indicate large snowpacks in much of the central and northern mountains, water equivalents of 30 - 60 inches still existing at high and cold locations, but much of the snow below 5000 - 6000 feet has now melted. Amounts are typical for this time of year (no great surprises or flooding), which is exactly what the California Department of Water Resources likes, making their jobs easier. After abundant rains during December and January with rapid snowmelt at middle elevations and associated flooding, mudslide, and other problems, February and March were much drier than normal, such that snowpacks which were once very thick are currently only average at south and central locations, above average northeast, and below average northwest. These can be compared with current airborne measurements of aerial extent and water equivalent of snow cover. This clearly illustrates usefulness of local snow surveys for providing detailed verification data.
Text is copyright of Joseph Bartlo, though may be used with proper crediting.