Dec 18 2008

Snow Isn't Just for Skiers

Posted by: Jonathan Marshall

After a long brown spell, California ski resorts are once again covered in white and looking forward to earning some real green over the holidays. For PG&E and its customers, recent precipitation--and the promise of more to come--bodes well for supplies of clean, inexpensive hydropower next year.

Though it didn't last long, recent cold storms dumped piles of hail on San Francisco and snow on Berkeley's Tilden Park, both memorable events. Up in the Sierra, major resorts now report two-to-three feet of snow.

"What a phenomenal change one storm has made for the mountain," said a spokeswoman for Alpine Meadows and Homewood Mountain ski resorts. "It is wonderful and humbling how quickly Mother Nature can move in and create something amazing. We couldn't have received this kind of snow at a better time."

Even so, the snow that provides so much of California's water is still running only 35 percent of normal--and only 19 percent of normal in Northern California. That leaves a lot of catching up to do.

At PG&E, principal hydrologist Gary Freeman watches snow and rainfall forecasts closely, since one of his jobs is to help the utility plan its use of clean hydroelectric resources. He says the watersheds that feed PG&E's hydro system stand a good chance of beating the drought after two years of sub-par precipitation.

"Next week we could get hit by some very wet storms tapping into subtropical moisture--what we used to call the Pineapple Express," Freeman said. "We should see lots of snow and rain right around Christmas, which will fill some of our lower-elevation reservoirs and build some snowpack. We could have another subtropical storm after that, so California could be back to normal or even wet by mid-January."

Full reservoirs will allow the utility to substitute hydropower for natural gas-fired generation, helping the environment and lowering costs. The only downside is likely to be the landslides and mud flows in watersheds laid bare by this summer's widespread and intense fires.

Freeman notes that PG&E's service territory is seeing relatively less snow and more rain than it did 30 years ago as a result of California's warming climate. The snowpack is also melting two-to-three weeks earlier. So far, that's not a problem. But if warming continues apace, heavy runoff from fast-melting snows could create potential operational challenges.

President-elect Obama's appointee as secretary of energy, Lawrence Berkeley National Laboratory Director Steven Chu, commented last year on the longrun impact of climate change on California's snowpack: "I think that's a much more serious problem than the gradually rising sea level, unless Greenland just completely melts," Chu said. "This is a huge water supply concern for California and the Southwest."

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