If it's winter, it might be raining - how much, we never really know until the storms come and the clouds hang thick over Mount Tamalpais. As Jon Mandell, manager of engineering at Marin Municipal Water District, quips, "We're not in the business of predicting the weather. We wait and see and manage the rain that does fall."

Seventy-five percent of the water we use -- even to fight fires -- comes from Mount Tam and its watersheds. The remainder arrives from the Russian River in a deal struck during the county's driest years, the drought of 1976-77.

"You can live without electricity or gas, but not without water," says Paul Helliker, general manager of MMWD, which delivers potable water to 190,000 thirsty customers, who require 120 gallons of water, on average and including landscaping, each day of the year. "The jewel in Marin is the MMWD watershed, and the goal is to maintain it for our grandchildren."

Drought: It's Anyone's Guess

You've heard the expression, a 100-year flood. What it means is that every year there is a 1 in 100 chance that a flood will occur. For drought, the same is true, but the odds are 1 in 63. So far in the past 100-plus years, drought has struck Marin three times, in 1929, 1976, and 1989.

"Fortunately, it's been wet in Marin since '92, with rainfall around normal for most of the years since then," Helliker says, with caution. The 2006-07 season (a rain season is tracked between July 1 and June 30) was drier than desired, though reservoir levels are at 69,000 acre-feet - for now comfortably near the normal storage baseline of 79,000 acre-feet.

As far as global warming goes, no one knows exactly what's in store, though predictions are unnerving. Helliker points to forecasts that the Sierra snowpack could be reduced 50 percent by 2050 due to higher temperatures. MMWD's planning forecast includes the potential for dry years as a matter of course. It now factors in an additional 10 percent rainfall reduction, in reaction to the imprecise nature of predicting climate change.

"We think ahead, always. We have to," says Helliker, adding that it's not the drastic reduction of Sierra snow that looms in the background, but something more specific to Marin. "They're saying another major drought could occur before 2040, and it could be a lot worse."

Water conservation is an indelible part of life in Marin, and we're known as being among the most water-conscious users in the state. But what we've done to date could be a drop in the bucket if we're hit by a major drought or climate crisis. Future water solutions on the table include desalinization of San Francisco Bay water, purchasing more water from the Russian River, and making deals for water with East Bay water districts.

Conserving Water and Energy

As concerns about energy use increase, the fact that Marin's water supply is mostly local may seem like a bonus. It is, to a degree: 19 percent of the electrical power used in the state goes to the collection, treatment, and distribution of water. In Marin, MMWD is PG&E's largest commercial account.

Eighty percent of MMWD's greenhouse gas emissions are associated with the electricity it needs to treat and distribute water through the labyrinth of underground pipes - 923 miles of them -- that also require always-on, power-hungry "booster" pumps to push the water up and over Marin's hilly landscape. Water is heavy: One gallon weighs more than 8 pounds.

As it turns out, conserving water is good for our watersheds and good for the atmosphere -- "a twofer," says Helliker.

FOR MORE INFORMATION

Marin Municipal Water District: www.marinwater.org