Marin Water Usage
Is a desalination plant the answer?
By Jim Wood
Can a county as lush as Marin have a water shortage problem? It did some 30 years ago after two winters of less than 50 percent of normal rainfall. Marin had to beg the federal government for $6 million to jury-rig a pipe over the Richmond Bridge that brought water to desperate residents.
Could it happen again? Paul Helliker, general manager of the Marin Municipal Water District (MMWD), says the county’s average rainfall is 52 inches—and back-to-back dry winters still mean trouble. “Last year we had only 35 inches of rain,” he says. “So heading into this winter we were worried.” Possibly, the anxiety was misplaced. By the end of January, Marin already had 32 inches of rain with notoriously wet March and March still to go.
Yet each year MMWD—which serves over 190,000 central and southern Marin residents—has a unique challenge. Unlike most districts, Marin doesn’t have underground aquifers or spring-fed lakes from which to draw freshwater. “We are 98 percent dependent on rainfall,” Helliker says, “and then we store that water in our seven reservoirs—five on Mount Tam two in West Marin.” MMWD also gets water from the Russian River, thanks to contracts with districts to the north. The source again: rainfall.
MMWD’s area consumes 10 trillion gallons of water a year, using it to drink, cook, bathe, water gardens—and run businesses such as farms, restaurants and car washes. The average capacity of all seven reservoirs is 20 trillion gallons. “However,” says Larry Russell, a Ph.D. in civil engineering and chair of MMWD’s five-person elected board, “after two consecutive ‘dry’ years, that capacity could drop to 10 trillion gallons, and we’d declare an emergency and call for a 65 percent rationing of water use.”
During the drought years of 1975 to ’77, equivalent reservoir capacity dipped into the four trillion gallon range. Which is dangerous. “In Sonoma and Marin counties, a 30 percent shortage of water could cost over 33,000 jobs and a $4.36 billion loss in revenue due to layoffs and reduced consumer spending,” says the executive summary of a recent North Bay Economic Insight conference. And with global climate change increasingly evident, it’s hard to predict what the weather holds in store.
Not to be trite, but what’s a water district to do? “The solution always proposed is to simply build more reservoirs or increase the height of existing dams,” says Russell, “but that’s almost impossible.” The federal Endangered Species Act and the State Water Resources Control Board have adamantly and repeatedly thwarted both approaches, he explains. “Protecting the coho salmon, steelhead trout and other natural habitats takes precedence. It’s not something that’s even on the table.”
Other potential solutions to Marin’s precarious water situation: 1) Increase conservation efforts. “This is dependent on voluntary action by users,” says Helliker, “which, until a crisis exists, isn’t always reliable.” 2) Increase the Russian River water allotment. Russell says this would entail a new pipeline and new contracts, both of which would face huge human, environmental and cost obstacles. 3) Construct a desalination plant on San Rafael Bay near the Richmond Bridge.
Though no commitment to desalination has been made, a $1 million pilot project was constructed (it passed all taste tests), a draft environmental impact report has been completed, and public hearings are now being held.
Currently, says Helliker, desalination or “desal” plants are operating successfully in Monterey County and on Southern California’s Santa Catalina Island. Also, after years of stops and starts (only a few technically related), North America’s largest desal plant, in Tampa Bay, Florida, is now converting 25 million gallons of saltwater a day into freshwater.
By fronting on San Rafael Bay, MMWD’s proposed desal plant would take in water that’s warmer and less saline than that processed by oceanfront locations. And because a sanitation plant is nearby, the brine extracted could be mixed with treated wastewater and returned to the bay in an environmentally acceptable way. Moreover, the $115 million plant being proposed would produce five million gallons of freshwater a day and could be expanded, at a cost of $60 million, to double that amount.
Although considerable discussion and analysis are still needed, the MMWD’s plan for a water desalination plant appears superior to other alternatives for tackling Marin’s water quandary. It is a progressive, proven and permanent solution. That’s my point of view. What’s yours?