Jan 25 2010

Winter Storms: Looking on the Bright Side

Posted by: Jonathan Marshall

Here at PG&E, we (like most Californians) have a love-hate attitude toward the rain. Like bitter medicine, it's not enjoyable in the moment, but deep down we know it's good for us.

Wind-driven precipitation knocks trees into our power lines, topples power poles and floods our facilities, creating outages and public safety risks. In fact, last week's storms impacted service to 1.5 million customers and damaged more than 500 poles, 250 miles of electrical lines and 800 transformers.

About the only good thing we can say during a storm is it brings out the best in our heroic repair crews and our customers, who (mostly) suffer service disruptions with patience and understanding.

But come spring and summer, if we haven't had enough rain, we at PG&E start to miss the clean, efficient hydropower driven by all the water in our mountain rivers and reservoirs. We also miss the wet ground that keeps vegetation from drying out and becoming tinder for giant wildfires that threaten our facilities and our customers' homes and businesses.

Before the onslaught of storms last week, California was headed into another drought year--its third in a row.

Just before the storms hit the state, the Department of Water Resources painted a bleak picture of continuing drought conditions:

This year's precipitation as of mid-January 2009 is well below average, with 20-30" of additional rain and snow needed to produce average runoff. The previous two water years, October 1,  2006 thru September 30, 2008 left a deficit of nearly 28" of precipitation in the Northern and Central Sierra, source of much of our water supply. . . . Statewide average reservoir levels are 68% of average for this date.  Last year at this time they were at 80% of average.

And the bottom line: "As of January 1, 2009, the statewide runoff is forecast to be dry to critically dry this year."

The result of the prolonged drought was to reduce PG&E's hydropower generation from 13,800 gigawatt-hours in 2006 to 7,700 GWh in 2007 and 7,900 GWh in 2008. (Preliminary data suggest that 2009 was a little better, but still far below normal.) This loss of about 7 percent of our total generation had to be offset by sharply higher power purchases, mostly from natural gas-fired generators, which increased costs to customers and greenhouse gas emissions as well.

Fortunately, this picture brightened last week even as the skies darkened. According to PG&E's hydro experts:

The recent wave of severe winter storms have produced significant amounts of snow and precipitation in PG&E service areas and hydro watersheds. As a result the cumulative precipitation picture has improved substantially: The California statewide average snow water content increased from 79 percent of normal on 1/7/2010 to 107 percent of normal on 1/21/2010; PG&E's hydro-weighted precipitation, from 15 representative stations, increased from 68 percent of normal to 91 percent of normal to date. If the wet trend continues, it could lead to better-than-average annual hydro generation year.

So as you struggle with your umbrella, or sit in the dark for a few hours, take heart in knowing that all this rain may end up saving you money and sparing the environment.

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