Marin County To Tap Seldom Used Reservoir

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Phoenix Lake in Marin County (CBS)

Phoenix Lake in Marin County (CBS)

MARIN COUNTY (CBS SF) — The Marin Municipal Water District is maximizing its water supply by pumping water from the Phoenix Lake reservoir to a water treatment plant during this dry year.

The pumping operation began Thursday and will end March 19. The District anticipates approximately 140 acre-feet of water will be transferred from Phoenix Lake in Ross to the Bon Tempe Treatment Plant on Mt. Tamalpais, District spokeswoman Libby Pischel said.

One acre-foot equals 325,851 gallons.

Seasonal rainfall at Lake Lagunitas is currently 18.77 inches, well below 50 percent of the average rainfall for this time of year, Pischel said.

Rainfall between July through February has been below 20 inches only 17 times in the last 134 years at Lake Lagunitas, Pischel said. In those dry years, the total annual rainfall has never exceeded 40 inches and the average rainfall in those years was about 28 inches, Pischel said.

The average rainfall at Lake Lagunitas is 52 inches, she said.

The Marin Municipal Water District gets approximately 75 percent of its water from rainfall captured in five reservoirs on the slopes of Mt. Tamalpais in central Marin County and two reservoirs in west Marin, Pischel said.

The rest of the district’s water is imported from the Russian River through a contract with the Sonoma County Water Agency.

Water levels at the reservoirs are also below average this year, Pischel said. Current reservoir storage is less than 61,000-acre-feet, or about 76 percent of capacity and 85 percent of average for the date, Pischel said.

The reservoirs have held less water storage on this date only once in the last 20 years dating back to the 1987-1992 drought, Pischel said.

Phoenix Lake is seldom used for water supply. It was last used as a water source in 1992 at the end of that drought, Pischel said.

“We also don’t use the Soulajule Reservoir in west Marin in normal rainfall years, and we don’t have plans to use it this year, but we do use it in drought years. It is part of our reserve water supply,” Pischel said.

Phoenix Lake is the District’s second smallest reservoir and is considered a reserve water supply source because of its size and location downhill from the treatment plant, which usually treats water from the Bon Tempe Reservoir.

It always has been considered part of the supply chain and the District invested $500,000 in a new pump and barge for Phoenix Lake, Pischel said.

Pischel said the District does not anticipate water use restrictions this year but wants to be in the best possible position if the dry year continues and if future years are also dry.

Due to last year’s high rainfall, the district does not expect the reservoir storage levels to drop to the alert stage this year of 50,000 acre-feet on April 1.

“There are no water restrictions yet. If the level drops to 50,000 acre feet on April 1, we would ask for a voluntary 10 percent cut back in water use as soon as possible,” Pischel said.

“We were glad to have the recent rain, but it was light,” she said.

(Copyright 2012 by CBS San Francisco and Bay City News Service. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.)

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