Firo: Optimizing Reservoirs in California

Forecast-Informed Reservoir Operations: Is California's Water Future Really "Smarter," or Just More Complicated?

The promise of Forecast-Informed Reservoir Operations (FIRO) is seductive: more water storage, less flood risk, all thanks to better weather forecasting. The core idea is that instead of relying on static, calendar-based rules for managing reservoirs, operators can use weather forecasts to dynamically adjust water levels, releasing water before a storm hits and holding it back if no storm is on the horizon. It’s presented as a win-win, but as any analyst knows, the devil is always in the details and hidden assumptions.

The Lake Mendocino pilot project is often cited as a success story. Implemented in 2017, the revised water control manual allows for an additional 11,650 acre-feet of water storage. In Water Year 2020, a dry year, FIRO purportedly enabled a 19% increase in water storage. Impressive, if true. But how replicable is this? Lake Mendocino is a relatively small reservoir. Scaling this approach to larger systems, like Lake Oroville, presents a whole new set of challenges. New Forecast-Informed Decision-Making Tool Implemented at Northern California Reservoir

The Atmospheric River Wildcard

Much of FIRO's success hinges on accurately forecasting atmospheric rivers (ARs), those narrow bands of concentrated water vapor that can deliver immense amounts of precipitation. Dr. Marty Ralph, Director of the Center for Western Weather and Water Extremes (CW3E), notes that in Northern California, 85% of the variance in annual precipitation comes from the 5% wettest days, which are almost all AR events. So, the entire water year boils down to correctly predicting a handful of storms.

This is where I start to get skeptical. (I've looked at hundreds of weather models, and they're only as good as the data that goes in.) While forecasting has improved, it's not perfect. The Atmospheric River Reconnaissance (AR Recon) program, which uses "Hurricane Hunter" aircraft to gather data, has reportedly improved precipitation forecasts by up to 12% for extreme events. That's a significant improvement, but it still leaves a margin of error. What happens when a predicted AR doesn't materialize, or is weaker than expected? You've released water unnecessarily, diminishing supply. Conversely, what if a surprise AR slams the coast? The consequences could be catastrophic.

California's reservoirs are typically managed for both flood control and water supply, a dual purpose that inherently creates conflict. For water supply, you want to keep reservoirs as full as possible. For flood control, you need to maintain empty capacity. FIRO attempts to thread this needle, but the risk of miscalculation remains.

One of the key challenges is updating the Water Control Manuals, which govern reservoir operations. These manuals are prepared by the U.S. Army Corps of Engineers, and ideally, they should be regularly updated to reflect advancements in technology and changing climate conditions. However, updates have been hindered by a "lack of appropriations." In other words, bureaucracy and budget constraints could undermine the entire FIRO initiative.

FIRO isn’t just about technology; it's about changing the culture of water management. It requires a shift away from calendar-based operations to a more dynamic, forecast-based decision-making process. This shift can meet resistance in organizations accustomed to traditional approaches. The human element – the judgment of reservoir operators – becomes even more critical, and potentially more prone to error. Details on how these operators are being trained and how their decision-making is being audited remain scarce, but the impact is clear.

Is This Progress, or Just Sophisticated Guesswork?

The promise of FIRO is tantalizing, but the reliance on weather forecasts introduces a significant element of uncertainty. While forecasting has improved, it's not foolproof, and the consequences of a wrong call could be severe. The implementation of FIRO also faces institutional and bureaucratic challenges, including updating Water Control Manuals and shifting the culture of water management. Until these challenges are addressed, FIRO remains a promising but unproven approach to managing California's water resources.

A Data-Driven Leap of Faith?