FIRO: Can Data Really Tame California's Water Wars?
Betting on Better Forecasts: FIRO and California's Water Future
California's always been a high-stakes game when it comes to water. Too little, and you've got dustbowl conditions. Too much, and you're looking at floods that can rewrite the map. Forecast Informed Reservoir Operations (FIRO) is the state's latest bet: that better data, crunched smarter, can help manage that precarious balance. The core idea? Use enhanced monitoring and improved weather forecasts to make smarter decisions about when to hold water and when to release it.
The linchpin of FIRO is the Atmospheric River Reconnaissance (AR Recon) program, spearheaded by the Center for Western Weather and Water Extremes (CW3E) at UC San Diego. They're flying aircraft right into atmospheric rivers (ARs)—those long, narrow bands of concentrated water vapor. Think of them as the Mississippi River in the sky, but sometimes carrying 15 times the Mississippi's flow. The AR Recon program isn't just about bragging rights; it's about getting real data. Dropsondes and ocean buoys are deployed to collect information directly from these storms, improving precipitation forecasts by up to 12% for extreme events. That might not sound like much, but in a state where 85% of the variance in annual precipitation in Northern California comes from the wettest 5% of days (almost all AR events), that 12% can be a game changer. In 2025 alone, 58 AR Recon missions were flown over a three-month period.
Lake Mendocino, a poster child for FIRO, provides some concrete examples. During the drought year of 2020, FIRO resulted in 18% more water going into the summer. That's enough to supply 20,000-30,000 households for a year. Fast forward to the flood year of December 2022/January 2023, and FIRO again proved its worth. It allowed operators to manage the reservoir level during an onslaught of atmospheric rivers, resulting in 13% more water than would have been available without FIRO. Again, enough for 20,000-30,000 households. It's worth noting that in 2025, FIRO rules were used to add 10,000 acre-feet of additional storage at Lake Mendocino. NOTEBOOK FEATURE: From forecast to flow: Optimizing California’s reservoirs with FIRO - Maven's Notebook
But here's where my skepticism kicks in. These numbers are impressive, but they also raise some questions. How much of this success is actually attributable to FIRO, and how much is due to natural variability in weather patterns? Could similar results have been achieved with more traditional methods, given the same amount of investment in forecasting technology?
The Devil's in the Water Control Manuals
Reservoir operations are governed by Water Control Manuals, prepared by the U.S. Army Corps of Engineers. These manuals outline the operational guidelines for managing water levels, including those all-important "rule curves" that dictate how high or low the water level should be at different times of the year. The problem? A lack of appropriations has hindered meaningful updates to these manuals for many reservoirs. You can have the best forecasting system in the world, but if the rules on the ground don't reflect that, you're still fighting with one hand tied behind your back.
A recent report released by the Department of Water Resources (DWR) examines how strategies, most importantly the Delta Conveyance Project, can help the State Water Project (SWP) maintain reliable water deliveries to 27 million Californians. The Delta Conveyance Project is a proposed project to build a tunnel to convey water from the Sacramento-San Joaquin Delta to the State Water Project and Central Valley Project. The question becomes, how do these large infrastructure projects interact with FIRO? Are they complementary, or are they competing for resources and attention?
CW3E is currently working on a FIRO viability assessment on Seven Oaks Dam with San Bernardino Valley Municipal Water District, who are planning for a successful FIRO viability assessment by building recharge basins. In Southern California, FIRO is used at Prado Dam to increase groundwater recharge, potentially averaging about 7,000 acre-feet over time. These numbers are promising, but they're also projections. The real test will come when these systems are put to the test during actual flood and drought events.
I've looked at enough of these proposals to know that the projected benefits are often…optimistic. What happens when the atmospheric rivers don't behave as predicted? What happens when the models are wrong? What's the plan B?
Storm Clouds on the Horizon?
The meteorology community isn't universally thrilled either. There are concerns that changing policies associated with the new administration are endangering the "weather and water enterprise," which is heavily dependent on NOAA. Dr. Ralph serves on a national committee legislated by Congress to advise NOAA on innovations and report to Congress on NOAA's actions. A draft report prepared by Dr. Ralph's committee is posted on the NOAA Science Advisory Board website, detailing concerns about changes affecting the weather and water enterprise. The committee recommends being used as an independent, objective source of input on changes to ensure the system isn't damaged.
The economic impact of the "weather and water enterprise" is about $100 billion a year to the US economy. That's a big number, and it underscores the importance of getting this right. But it also raises the stakes. When you're talking about that kind of money, you're going to have competing interests, political pressures, and a whole lot of noise.
A Glimmer of Hope, But Still a Gamble
FIRO represents a step in the right direction—a move towards using data and technology to make smarter decisions about water management. But it's not a silver bullet. It's one piece of a much larger puzzle. Until California gets serious about updating its Water Control Manuals, investing in infrastructure, and addressing the political challenges that plague its water system, FIRO will remain just that: a forecast.
