Generated Title: Lake Mendocino's Water Stash: A Real Fix, or Just Clever Accounting?
Mendocino's New Manual: A Closer Look
On October 22, 2025, there was a ceremony. Officials patted themselves on the back for the updated water control manual for Coyote Valley Dam and Lake Mendocino. The magic ingredient? Forecast-Informed Reservoir Operations (FIRO). The claim is that this new manual unlocks an extra 11,650 acre-feet of storage in the flood control space, all thanks to the U.S. Army Corps of Engineers' discretion. Now, on paper, that sounds impressive.
But let's dig into the numbers. Lake Mendocino is supposedly using FIRO to squeeze out 10,000 acre-feet of additional storage in 2025. Rep. Jared Huffman is singing its praises, and Sonoma Water Board Chair Lynda Hopkins is claiming FIRO has saved water equal to another Lake Mendocino. DWR Director Karla Nemeth is calling Lake Mendocino the first of many such efforts.
Here's where my skepticism kicks in. We're talking about a lake that's a crucial drinking water source for roughly 650,000 people across Mendocino, Sonoma, and Marin counties. It relies on rainfall and diversions from the Potter Valley Project. So, the question isn't just whether FIRO works in theory, but whether it works reliably under real-world conditions.
The historical context is key. Coyote Valley Dam was finished back in 1959, and the water control manual has been tweaked twice before: once for a hydroelectric plant in 1986, and again in 2011 for aquatic habitats. FIRO itself was first tested at Lake Mendocino in 2017. They ran virtual trials with models and forecasts. Apparently, it worked well in both a wet year (2019) and a dry year (2020). In 2020, they claim FIRO boosted storage by 19%, adding over 11,000 acre-feet. Over the last three years, they say FIRO has saved nearly 30,000 acre-feet. New forecast-informed decision-making tool implemented at Coyote Valley Dam and Lake Mendocino - Scripps Institution of Oceanography |
That 30,000 acre-feet figure is interesting. It's a cumulative number, but what were the annual savings? Were they consistent, or did one particularly wet year skew the results? The announcement conveniently omits that level of detail.
Atmospheric Rivers and the Hurricane Hunters
FIRO hinges on better forecasting, specifically of atmospheric rivers. These rivers in the sky can carry as much moisture as the Mississippi River – up to 15 times that amount in the strongest cases. In Northern California, 85% of the variation in annual precipitation happens during the wettest 5% of days, which are almost all atmospheric river events. The Atmospheric River Reconnaissance Program uses Air Force and NOAA "Hurricane Hunters," plus drifting buoys and land-based observations, to gather data.
This is where I start to see potential issues. Relying on atmospheric river forecasts is inherently risky. While forecasting has improved, it's still not perfect. What happens when a predicted atmospheric river fizzles out, leaving Lake Mendocino short on water because they released too much preemptively? Or, conversely, what happens when a bigger-than-expected atmospheric river hits, and the reservoir is already near capacity?
Also, let's not forget the Oroville Dam scare in 2017. Nearly 200,000 people had to evacuate due to fears of collapse after a rain-on-snow event. Reservoir management isn't just about maximizing water storage; it's about public safety. Are we sacrificing safety for a marginal increase in water supply?
The documents state that AB30 (2023) updated legislation to include FIRO as a tool to manage water scarcity and floods. Fine, but legislation doesn't guarantee results. It just codifies intent.
And this is the part of the report that I find genuinely puzzling: they're applying FIRO in different ways across California. At Prado Dam in Southern California, it's used to increase groundwater recharge. Lake Oroville and New Bullards Bar are also in the mix. But each reservoir has its own unique characteristics and challenges. A one-size-fits-all approach seems overly optimistic.
The California Department of Water Resources reported that the state’s snowpack measured 96% of average at its peak on April 1, 2025. Snowpack is a reliable metric. FIRO relies on weather models. Which one do you trust more?
A Gimmick or a Game-Changer?
The numbers, as presented, paint a rosy picture. But I'm not entirely convinced. FIRO appears to be a useful tool, but it's not a silver bullet. It's more like a clever accounting trick that allows water managers to squeeze a bit more out of existing resources. Whether that's enough to make a real difference in the long run remains to be seen. I’d want to see at least a decade’s worth of consistently positive data before I’d celebrate.
