By Dan Shapley
A sneak preview? California has already asked residents to curtail water use in what should be high times for water managers. The culprit is the Sierra Nevada snowpack, which is 40 percent less than normal and at its lowest point in nearly 20 years. While the reservoirs are full now, if conditions persist, the state could face mandatory water restrictions. While no one weather event can be tied directly to the overall warming of the globe, this is the type of problem that scientists have predicted. With warmer temperatures, come retreating glaciers and thin snowpacks - a serious issue for places, like California, that draw most of their drinking water from mountain reserves.