Firo: Optimizing California’s reservoirs – What we know

FIRO: A Calculated Gamble Worth Taking?

The U.S. Army Corps of Engineers (USACE) and Sonoma County Water Agency have officially updated the water control manual for Coyote Valley Dam and Lake Mendocino, incorporating Forecast-Informed Reservoir Operations (FIRO). The promise is a more dynamic approach to water management, balancing flood control and water supply using advanced weather forecasting. It's a bold move, shifting from static rules to a system that hinges on the accuracy of atmospheric river predictions. But is this reliance on forecasts a leap of faith, or a calculated gamble that will pay off?

The core of FIRO lies in its ability to use weather forecasts, particularly those concerning atmospheric rivers, to make informed decisions about reservoir water levels. Instead of blindly releasing water based on historical averages, FIRO allows operators to strategically release or retain water based on predicted storm events. The revised manual apparently allows for an additional 11,650 acre-feet of water storage, at USACE discretion, when forecasts indicate it's safe. The claim is that this approach has already proven successful, with a 19% increase in water storage during Water Year 2020 (a dry year), thanks to FIRO.

But let's unpack that 19% figure for a moment. It sounds impressive, but what does it really mean? How much did that 19% actually buffer water users, and what was the margin of error in the forecast that allowed that extra storage? The reports highlight that FIRO saved nearly 30,000 acre-feet of water in Lake Mendocino over three years. While a positive result, it's essential to put this into perspective. Lake Mendocino's total capacity is roughly 122,000 acre-feet. So, we’re talking about a potential increase of around 25% of the total capacity over three years, or about 8% per year.

The Atmospheric River Wildcard

The success of FIRO is inextricably linked to the accuracy of atmospheric river forecasts. These "rivers in the sky," as they're sometimes called, are responsible for a significant portion of California's precipitation, but they're also notoriously difficult to predict. The Atmospheric River Reconnaissance Program, which uses "Hurricane Hunter" aircraft and other advanced tools, has undoubtedly improved forecasting capabilities. The data suggests that the program has improved precipitation forecasts by up to 12% for extreme events.

However, a 12% improvement, while significant, still leaves room for error. And in the world of water management, even small errors can have big consequences. Overestimating an incoming storm could lead to reservoirs being too full, increasing flood risk. Underestimating a storm could result in missed opportunities for water storage. The question is: how much of a buffer are they building into the system to account for forecast inaccuracies?

I wonder, are we truly prepared for the inevitable scenario where a forecast fails? What are the contingency plans in place to mitigate potential flooding or water shortages if the atmospheric rivers don't behave as predicted? These details are conspicuously absent from the published reports. New forecast-informed decision-making tool implemented at Coyote Valley Dam and Lake Mendocino

Beyond Lake Mendocino: A Scalable Solution?

Lake Mendocino is just the first FIRO project. The approach is being considered for other reservoirs across California and beyond. The Yuba-Feather system, for example, could see an additional 265,000 acre-feet of flexible storage thanks to FIRO. But each watershed is unique, with its own climate patterns, topography, and infrastructure. What works in Mendocino County may not necessarily work in the Sierra Nevada.

And this is the part of the analysis that I find genuinely puzzling. The reports emphasize the need for tailored approaches based on local conditions, but they offer little detail on how these tailored approaches will be developed and implemented. Will there be sufficient resources allocated to conduct the necessary research and modeling for each individual reservoir? Or will FIRO be rolled out as a one-size-fits-all solution, potentially leading to unintended consequences?

The move towards Forecast Informed Reservoir Operations reflects a broader trend: a shift from reactive to proactive water management. That is, we're moving from simply responding to events as they happen to anticipating and preparing for them in advance. It's an ambitious goal, one that requires not only technological advancements but also a fundamental change in how we think about water. It’s like moving from driving by looking in the rearview mirror to using a GPS – more efficient, but you better hope the GPS is accurate.

The Forecast Still Isn't Perfect

The updated water control manual for Lake Mendocino represents a significant step forward in water management. But it's not a silver bullet. The success of FIRO hinges on the accuracy of weather forecasts, the adaptability of water managers, and the willingness to acknowledge and mitigate potential risks. It's a calculated gamble, one that could pay off handsomely in terms of increased water supply and reduced flood risk. But it's a gamble nonetheless, and it's essential to understand the odds before placing our bets.