Our modern plumbing system

Turn on your faucet, fill up a glass and take a long cool drink. That Petaluma city water that just quenched your thirst likely started out in Lake Sonoma, Lake Mendocino, or even in the upper reaches of the Eel River, two watersheds away.

We have a complex multi-million dollar network of plumbing to thank for the water that comes out of our taps here in Petaluma, though many residents in the city probably don’t know where our water comes from or what it takes to get it here.

The veil is about to be partly lifted on a section of water pipes in Petaluma, giving us a glimpse at the water delivery system that most of us take for granted. The Sonoma County Water Agency is embarking on a $1.3 million project to upgrade the 56-year-old Petaluma Aqueduct, which delivers drinking water to residents in Petaluma, Cotati, Rohnert Park and northern Marin County.

The project will upgrade the pipeline’s cathodic protection system, which uses so-called “sacrificial metal anodes” that stop the pipe from rusting or corroding. The work will dig up parts of Petaluma Boulevard South, causing traffic delays this summer, but it will be worth it to preserve the longevity of a safe, reliable water delivery system.

This is also a good reminder, as the rainy season begins to wind down, that our region is never far away from the next drought. While we currently have adequate reserves of water stored in our hydrological system, with a couple more dry winters we could be back to severe water shortages. It makes sense, then, to continue exercising prudent water conservation practices first undertaken just a few years ago.

The aqueduct is the last leg of an intricate water deliver service to Petaluma that begins in the creeks that feed into Lake Pilsbury.

In 1900, the communities of Sonoma County realized that the Russian River would not be able to provide water for the growing population of the region and launched a project to divert the Eel river through a tunnel at Potter Valley and into the East Fork of the Russian River.

The Scott Dam, which forms Lake Pilsbury, was built in 1922, providing a reliable flow on the upper Eel, which could be diverted south toward Sonoma County. In 1959, the Coyote Valley Dam was built forming Lake Mendocino, providing a critical water storage basin for dry year s.

In 1982, the U.S. Army Corps of Engineers built the Warm Springs Dam across Dry Creek, forming Lake Sonoma. Besides aiding in flood control, the lake stores 381,000 acre feet of water which, when released, replenishes the Russian River, Sonoma County’s main drinking water supply.

Down stream from Dry Creek, aqueducts dip into the Russian River like drinking straws around Forestville. The Santa Rosa Aqueduct, completed in 1959, links up with the Cotati Aqueduct, forming the Petaluma Aqueduct. Completed in 1962, it delivers Russian River water over the Cotati Grade and into the Petaluma Watershed, where it is stored around the city in 10 water storage reservoirs, like the two tanks on La Cresta Ridge.

From there, the water travels through 278 miles of pipes under the city to the faucets of the 60,000 Petaluma residents.

So, turn on your tap, fill up a glass, and pause before taking that long cool drink while you contemplate the complex journey your water has taken. Be glad we are upgrading our modern water delivery system, and be mindful about the need to conserve water.