More than half of the water used in California for farming, drinking and other everyday uses comes from Sierra Nevada runoff, according to a university news release. Gauging the amount of snow there and predicting how much runoff there will be is an annual rite that has a major trickledown effect of its own. Today, water managers physically measure the snow depth at a series of index sites. Then they compare the results to those from past years to predict water availability and determine how much water will be allocated to farmers and communities. The data are limited and the predictions can have a high degree of uncertainty. "In a more physically based approach to predictions, you start with learning how much snow is there," Bales said in the release. "Then you measure rainfall, model the timing of snowmelt and estimate how much water is used by trees and exits the system elsewhere." Read more here: http://www.mercedsunstar.com/2011/03/03/1795284/uc-merced-prof-designs-sensor.html#storylink=cpy