Spotlight Nov 2021: Sonoma Water Puts Conjunctive Use to Work in Building Resiliency to Climate Extreme by ACWA Staff Nov 19, 2021 Newsletters Sonoma Water serves a region that exemplifies flashy hydrological conditions, swinging from floods – such as on the Russian River in the above photograph from 2014 – to the current drought, which has left Lake Mendocino nearly dry in the photograph on the opposite page. Photos courtesy of Sonoma Water. Weather and water experts frequently encapsulate California’s new reality as one of “wetter wets and dryer dries.” Sonoma County offers a case study in what those flashy extremes look like within a single region. But that case study comes along with a rare success story about how an area among the hardest hit by the latest drought is adapting through locally managed conjunctive use of water. ACWA member agency Sonoma Water depends on the Russian River for most of its water supply. The same river flooded during early 2019 and nearly left the town of Guerneville underwater. Two years later, drought slammed the region into the other end of the climate scale. In April, Gov. Gavin Newsom declared the Russian River watershed as California’s first regional drought emergency, making his announcement from the dry bed of a drastically lowered Lake Mendocino. Dairy farmers in the hills west of Petaluma have had to purchase tanker trucks of water to keep their herds alive after many of their wells went dry. “The challenge we faced was, ‘how do we keep the water flowing out west and not have the city of Petaluma be affected?’,” said David Rabbitt, who serves on Sonoma Water’s Board of Directors as part of his role as a Sonoma County Supervisor. By August, the State Water Resources Control Board mandated a 20% curtailment on diversions among Russian River water rights holders, including Sonoma Water, which had already enacted conservation measures early in the year. Conservation is working, and Sonoma Water has actually reduced Russian River diversions by 24%, beyond the 20% mandated by the state. However, conservation isn’t the only key to that success. The agency recently re-activated an 808-foot production well that is now supplying 1.6 million gallons a day, the first of two phases in Sonoma Water’s Santa Rosa Plain Drought Resiliency Project. The second phase will upgrade water treatment and piping for two additional wells for use during extreme droughts or emergencies. Sonoma Water will also add recharge capabilities to at least one of the three wells, allowing it to pump Russian River water back into the ground during rainy seasons. Most of the wells in the area draw from a shallow, fractural aquifer that grew unreliable as the drought progressed. The production wells sink into a deeper aquifer and range in depth between 794 feet to 1,060 feet. Originally drilled in the mid-1970s drought, the production wells also helped Sonoma Water augment its supply during the 2012-’15 drought. They have remained primarily offline since 2015; averaging only 20 acre-feet of production each year while allowing the local aquifer system to fill back up. For comparison purposes, Sonoma Water annually delivers an average of about 45,000 acre-feet of Russian River water to its contractors, who collectively serve more than 600,000 people. Reservoirs such as Lake Sonoma, also built during the 1970s, were designed to store three years of water supply. Sonoma Water has collaborated with state and federal agencies to explore how advanced forecasting methods can dovetail with Forecast-Informed Reservoir Operations to maximize existing surface storage. However, nobody’s building more reservoirs anytime soon, Rabbitt said. “If we can get 5% more efficiency out of our reservoir, that’s huge,” Rabbitt said. “But conjunctive use is really the way to build resiliency. The reservoir of the future is going to be beneath our feet.” .