U.S. ARMY CORPS OF ENGINEERS Forecast Informed Reservoir Operations
Forecast Informed Reservoir Operations As weather extremes become the norm, USACE and partners pioneer a new way to manage water resources.
A
lthough nobody knew it yet in January and February of 2020, the state of California was in the early months of what would become the driest three-year period in the state’s recorded history. But when rain fell in one of the region’s watersheds – BY CRAIG COLLINS
104 I AMERICA’S ENGINEERS
the Russian River basin, which drains 1,485 square miles in Mendocino and Sonoma Counties – water managers at one of the system’s reservoirs, Lake Mendocino, were able to exercise a choice they wouldn’t have had under their existing management plan. The 2019-2020 “water year” – which, in California, begins on Oct. 1 and ends on
Sept. 30 of the following year – was when U.S. Army Corps of Engineers (USACE) and its partners at Lake Mendocino piloted a new approach, Forecast Informed Reservoir Operations (FIRO). Traditionally, decisions about whether to hold water behind a dam, or whether to release it downstream, are influenced or determined by conditions on the ground. “Under our normal operating rules, all water within the flood control space would have had to be released,” said Patrick Sing, lead water manager for USACE’s San Francisco District. “But we had a temporary deviation agreement in place that allowed us to implement FIRO, and we had some dry weather forecasts in place at the time, so USACE was able to retain some of that water.” In total, the amount of water held back was 20% more than it would have been under previous guidelines: an additional 11,650 acre-feet, enough to supply up to 24,000 households for a year. According
