Six wells plunging up to 60 feet into deep gravel beds beneath the Russian River near Forestville draw out water that supplies 600,000 residents in Sonoma and Marin counties.
Massive pumps with a combined 14,750-horsepower rating pull water from the gravel aquifer and propel it into a distribution system that serves six cities and three water districts from Windsor to Sausalito.
Technically, it is all Russian River water. But it comes to the pumps from a system that stretches nearly 100 miles to the north and collects rainfall from 235 square miles of watershed in hilly, rural reaches of Sonoma and Mendocino counties.
Two reservoirs — Lake Sonoma near Healdsburg and Lake Mendocino near Ukiah — hold enough drinking water to cover 282,000 football fields a foot deep (or 282,000 acre feet). That's a whopping 92 billion gallons of water behind two dams, which also serve as Russian River flood-control facilities.
Lake Sonoma backs up behind a $360 million federally built dam northwest of Healdsburg that was the object of a prolonged political battle and two public votes in the 1970s.
Coyote Dam, completed in 1959, blocks the East Fork of the Russian River, forming Lake Mendocino, which provides water to Ukiah and Mendocino County farms and about half of Sonoma County's supply, with the other half flowing from Lake Sonoma.
And even farther to the north, a source of both water and controversy, is a mile-and-a-half tunnel blasted through a rock mountain in the early 1900s, before permits and policy replaced the rugged western entrepreneur's urge for water and electrical power.
The tunnel sucks water from the Eel River, which flows north into the Pacific Ocean near Eurkea, and diverts it into the Russian River through a powerhouse in Potter Valley that still generates electricity.
Eel River diversions, which have been cut in half in recent years, remain a point of contention as federal, state and local agencies balance the water needs of people and endangered fish species in both the Eel and Russian rivers.
Warm Springs dam, completed in 1983, is the Sonoma County anchor of a system with about 79 miles of underground pipeline and 18 steel water storage tanks that delivers Russian River water to residents and businesses in Santa Rosa, Windsor, Rohnert Park, Cotati, Petaluma and Sonoma and to water districts in Sonoma Valley and Marin County.
The rest of Sonoma County, including Sebastopol, Healdsburg and Cloverdale and most of the area outside city limits — including most farms, dairies and vineyards — gets its water from wells.
Both reservoirs are watched closely these days, especially in water-poor years when mandatory conservation measures are imposed, but they were conceived and built to curb destructive floods along the Russian River.
Warm Springs Dam is a 319-foot compacted earthen barrier at the confluence of two small creeks — Warm Springs and Dry Creek — at the far end of scenic, wine-producing Dry Creek Valley northwest of Healdsburg.
Lake Sonoma holds 212,000 acre feet of water for human consumption, a two-year supply, officials say. That abundance enabled Santa Rosa to become the 28th fastest growing city in the United States in the 1980s.
Today, however, the region's water dynamics are more complicated. The two reservoirs must not only provide water to 600,000 people, but also maintain minimum summertime flows in the Russian River to preserve endangered fish species.
Lake Mendocino, which depends on spring rains for annual refilling, is solely responsible for the river flow between Ukiah and Healdsburg.
A further complication stems from limits on the amount of water that can be released from Lake Sonoma down a 14-mile stretch of Dry Creek to the Russian River, based on findings that too much water is bad for the young fish maturing in the creek.
If a proposed reconfiguration of Dry Creek fails to protect the fish against higher flows, the county may have to build an expensive pipeline from the dam to the Wohler pumps.
Sonoma County Water Agency officials refer to their resource as "home grown" water, coming from moisture that sweeps across the Pacific Ocean in clouds and falls nearby on mountains in California's coast range.
As such, it is distinct from the water that comes from the Sierra snowpack and is transported hundreds of miles to the metropolises of the Bay Area and Southern California, as well as vast farmlands of the Central Valley.
The coast range and the Sierra are the only rainfall-rich regions of the state, which is otherwise a semi-arid land transformed by water engineers into an agricultural powerhouse and the nation's most populous state.
The State Water Project transports 2.4 million acre feet of water per year, flowing through 700 miles of aqueducts, canals and pipes from Lake Oroville in Butte County to Lake Perris in Riverside County.
The local water agency, in contrast, is legally entitled to draw no more than 75,000 acre feet annually from the Russian River, and last fiscal year pumped just 45,873 acre feet from the Forestville wells.
That's down nearly one-third from the 66,556 acre feet pumped in 2003-04, the peak consumption in the past 15 years.
Aggressive water conservation measures adopted during three drought years (2007-09) account for much of the drop in consumption, according to Mike Thompson, the water agency's assistant general manager.
Cities and water districts supplied by the agency have also turned to increased use of groundwater from their own wells, reducing demand on the Russian River, he said.
The close-to-home water source may bode well for the region's future, as climate change is expected to shrink the Sierra snowpack, possibly triggering a water supply crisis.
Experts aren't certain whether the coast range will get wetter or drier in future decades. "Right now we don't know a whole lot," said Pam Jeane, water agency assistant general manager. "The scientific jury is out."
You can reach Staff Writer Guy Kovner at 521-5457 or guy.kovner@pressdemocrat.com.
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