Atmospheric River Research Packed with Potential by Dave Eggerton Feb 22, 2019 Voices on Water The past few weeks have demonstrated how atmospheric rivers, over a relatively short period of time, can completely alter the long-term outlook for water storage. Although the year’s first snow survey in January gave us cause for concern, the outlook quickly changed. By Jan. 31, the second snow survey recorded 50 inches – double that of the first snow survey with the Department of Water Resources declaring the Sierra snowpack at a refreshing 100% of average. By comparison, on Feb. 1 of last year, measurements at Phillips Station revealed only 14% of the early-February average. The good news is, for the first time in a long while, Southern California is receiving as much precipitation as Northern California. The bad news is, in that region and in areas throughout the state, atmospheric rivers are not only filling reservoirs, but resulting in flood warnings. And with reservoirs filling, that in itself underscores the importance of further investment in water storage. You have to wonder, what if we could take even some of the guesswork out of forecasting atmospheric rivers, the primary source of most of the West Coast’s precipitation. Well, progress on that front is moving from mostly fantasy and more toward fact. Research and work on weather modeling is ongoing at local, state and federal levels, including the state Department of Water Resources and Scripps Institution for Oceanography’s Center for Western Weather and Water Extremes (CW3E). Earlier this month, a team of researchers at Scripps created a scale to characterize the strengths and impacts of atmospheric rivers, similar to what is done with hurricanes. This marked one more step toward enhancing our ability to refine response to atmospheric rivers as either beneficial or potential emergencies, or a mix of both outcomes. Demonstrations are underway that are matching improved forecasting with revised methods of reservoir management. For example, at Lake Mendocino during mid-January, advances in forecasting technology and weather modeling accurately predicted when and where an atmospheric river would stream over the Russian River watershed, which feeds the reservoir. Just as importantly, dam operators were allowed to deviate from established procedure and let the forecasting become a deciding factor on whether or not to release extra water. In theory, that approach could be applied statewide. Several atmospheric rivers have delivered an abundance of rain and snow to our state, but we know all too well that’s not always the case. Whether it is a wet or dry year, an enhanced ability to capture and store even a fraction more of what atmospheric rivers bring in precipitation could make a tremendous difference. Improved groundwater recharge would be another benefit. What’s more, the ability to extend atmospheric river forecasting can deliver better flood control and emergency preparedness. The further we can look ahead, the better we can anticipate when to create the most room in reservoirs and prevent as much flood damage as possible. To learn more about the latest in atmospheric river research, see this edition’s Spotlight section on pages 9 and 10.