With extreme weather increasing around the world, scientists are working to help critical infrastructure, such as water management systems, adapt. On the U.S. West Coast, where both periods of prolonged drought and intense atmospheric river storms are common, effective water management can be particularly tricky. One strategy that water managers are now pursuing is known as Forecast Informed Reservoir Operations (FIRO). The method relies on increasingly accurate weather forecasts to improve water supply reliability without increasing flood risks to downstream communities. Rather than release water from reservoirs at the onset of the wet season, more water can be held in reservoirs until wet weather is forecasted, when it can then be released ahead of the storm to make room for incoming streamflow. This makes it possible to retain water in cases when rains never arrive, preserving water for the inevitable dry periods. Implementing this system at every reservoir isn't yet possible, and evaluations of where weather and streamflow forecasts are advanced enough to use this strategy are ongoing. A new study helps advance the evaluation process by identifying the physical and operational constraints that influence how much forecast lead time would be needed to safely use FIRO at a given reservoir.
The research, published in Water Resources Research , was led by DRI's Christine Albano. She and her colleagues developed a systematic approach for gaining early insights into the opportunities and challenges of using FIRO at individual reservoirs. The approach identifies watershed and reservoir characteristics that govern how incoming flows historically compare to the amount of storage space available in the reservoir, as well as the rates at which water can be safely released. "These are key determinants of how flexibly water can be safely moved and managed," Albano said. "To make these comparisons, we combined historical streamflow and reservoir storage data with information on reservoir structures and water release capacities that were compiled by the US Army Corps of Engineers as part of their FIRO screening process", she said. "This type of analysis is important because it captures the nuances of the day-to-day operational realities in these reservoirs that aren't necessarily well-represented in theoretical simulations typically used for planning."
Applying the framework to 32 reservoirs across California and Nevada, the researchers found that operational flexibility is generally more constrained in reservoirs on snowmelt-dominated rivers than at reservoirs on rivers where precipitation falls primarily as rain. This is because watersheds that have been historically snow-dominated typically have reservoirs with large storage capacity, but because their designs relied on a slow snowmelt process, these systems were not designed to safely release large amounts of water quickly. This means that weather forecasts would need to accurately predict incoming storms much further in advance to make room for incoming flows without increasing flood risks to downstream communities. Additional water management strategies such as managed aquifer recharge may be need to be utilized to maintain water supplies without increasing flood risks.
By providing a transferable methodology for evaluating watershed and reservoir characteristics, the study offers water managers, hydrologists, and reservoir operators a practical tool for identifying where FIRO may safely provide the greatest benefits and where additional adaptation strategies may be needed. "With the nationwide screening of FIRO suitability currently underway for dams owned and regulated by the US Army Corps of Engineers, tools such as this add to our ability to prioritize where FIRO can and should be implemented next", said Cary Talbot, National Lead for the FIRO research program within the US Army Corps of Engineers.
The research also highlights the importance of considering future climate conditions. In the last two decades California has experienced two of the driest 3‐year periods on record, two of the wettest years on record, and groundwater levels have declined in nearly half of all of the State's wells. These stresses are motivating important changes to California water management, but reservoir infrastructure and water management protocols are typically decades old and were established under very different data-availability, water supply, and demand realities. A warmer atmosphere means more water demand by crops and people, less predictable wet seasons, reduced snowpacks, earlier snowmelt, and more intense atmospheric river storms. These changing conditions reinforce the need to update surface water management operations. Understanding the operational flexibility of a given reservoir, as well as the watershed and infrastructure attributes that limit flexibility, provides important insights into the tradeoffs between flood protection, water supply, and other reservoir objectives.
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More information: The full study, Characterizing Watershed Responses and Reservoir Operational Flexibilities: Analyses to Support Forecast Informed Reservoir Operations (FIRO) Planning and Assessments, is available from Water Resources Research at https://doi.org/10.1029/2025WR042131
Study authors include: C. M. Albano , E. J. Shearer , J. C. Forbis , E. M. Yeates , J. Kalansky , C. A. Painter , B. Tustison , A. M. Wilson , M. L. Anderson , M. D. Dettinger , F. M. Ralph , C. A. Talbot
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