The Dam Data: Is This Really a Win for California Water?
On the surface, the revised water control manual for Coyote Valley Dam and Lake Mendocino looks like good news. Officials are patting themselves on the back for incorporating Forecast-Informed Reservoir Operations (FIRO), which they claim will boost water storage and improve flood control. But let's dig into the numbers and see if this is genuine progress or just another case of politicians spinning a middling upgrade.
FIRO: A Closer Look at the Claims
The core of this update is FIRO, first applied to Lake Mendocino in 2017. The idea is to use better weather forecasting, particularly around atmospheric rivers, to manage reservoir levels more dynamically. Instead of rigidly sticking to historical averages, they're trying to anticipate storms and adjust storage accordingly. New forecast-informed decision-making tool implemented at Coyote Valley Dam and Lake Mendocino - Scripps Institution of Oceanography
Lynda Hopkins, chair of the Sonoma Water Board of Directors, claims FIRO techniques have saved water equivalent to a "second Lake Mendocino." That's a catchy soundbite, but let's break it down. The fact sheet states FIRO has saved nearly 30,000 acre-feet of water over the past three years. Lake Mendocino's capacity is around 122,000 acre-feet. So, we're talking about a quarter of Lake Mendocino’s capacity, not a whole second lake. (A more accurate, though less exciting, claim.)
U.S. Representative Jared Huffman is also singing praises, emphasizing the shift to "science-based operations." But was it not science-based before? It's a rhetorical question, of course. Every politician says their decisions are rooted in science. The real question is: how reliable is the science they're using? Atmospheric river forecasting is improving, thanks to programs like the Atmospheric River Reconnaissance Program (which uses "Hurricane Hunters," no less), but it's far from perfect. How often will these forecasts miss the mark, leading to either unnecessary releases or insufficient storage? I've looked at enough weather models to know that their certainty can be as murky as the lake itself.
The Devil is in the Acre-Feet
The revised manual allows for an additional 11,650 acre-feet of water storage at USACE discretion. This is the key number. It represents the potential upside of FIRO. In Water Year 2020, FIRO enabled a 19% increase in water storage, totaling more than 11,000 acre-feet. So, the new manual is basically codifying what they’ve already demonstrated is possible.
Is this a game-changer? Not really. Lake Mendocino is a crucial water source for 650,000 people, but it's also heavily reliant on rainfall and diversions from the Potter Valley Project. The Potter Valley Project is facing its own set of challenges, and reduced diversions could easily negate any gains from FIRO. Details on how these factors will interact remain scarce, but the potential for conflict is clear.
And this is the part of the analysis that I find genuinely puzzling: Why did it take them so long to formally update the manual? FIRO has been in use since 2017, and the benefits were demonstrated in 2019 and 2020. What was the hold-up? Bureaucracy? Political maneuvering? Or were they waiting for more data to confirm the initial results? It's hard to say, but the delay raises questions about the responsiveness of these agencies.
A Modest Improvement, Not a Miracle
The updated water control manual for Lake Mendocino is a step in the right direction. It acknowledges the potential of FIRO and allows for more flexible water management. However, let's not pretend this is a silver bullet for California's water woes. The gains are modest, and the success of FIRO depends on the accuracy of weather forecasts and the continued availability of water from other sources. Time will tell if this update lives up to the hype, or if it's just another drop in the bucket.
