By Jackie Miller
Every February, the California Department of Water Resources begins releasing a series of updates known as the B-120 forecasts. These reservoir inflow estimates are based on water year-to-date (WYTD) rainfall and snow water equivalent, combined with a statistically based forecast of inflow for the remainder of the water year.
But the water year (WY) begins October 1.
What about the management decisions that happen from October to February, before the state releases its first update?
Until now, water managers needed to prepare for every possible scenario—drought, flood, and in-between—just to avoid being caught off guard. But in WY 2024-25, Weather Tools’ CRAFT forecast gave customers another option.
Issued the first week of November, the California Reservoir Annual Forecast Tool (CRAFT) offers a fixed range of inflow for 18 California reservoirs, covering the entire water year and available about four months before the B-120. Its primary input is Weather Tools’ California Annual Precipitation (CAP) forecast, now completing its ninth consecutive year of accurate water year precipitation forecasts.
How Do CRAFT and the B-120 Compare For WY 2024-25?
In the plots below, the green line shows the WYTD observed inflow at Lake Shasta (top), Folsom Lake (middle), and Millerton Lake (bottom). The vertical orange bars represent the B-120 forecast range, stretching from the 90% chance of exceedance runoff estimate (dry forecast) to the 10% chance of exceedance value (wet forecast). The first B-120 was issued on February 11, followed by frequent updates as conditions evolved. Between February and June, there were 19 total updates; seven of these are shown in the plots.
In contrast, the blue rectangle shows CRAFT’s fixed-range forecast, issued the first week of November and unadjusted throughout the WY.
When comparing the two forecasts, it’s clear that the CRAFT range is significantly narrower than that of the initial B-120 (see orange and blue text for specific values).
At Lake Shasta, CRAFT subscribers received a WY inflow forecast of 4.727–6.302 million acre-feet (MAF). In contrast, the initial B-120 forecast, delivered four months later, spanned 5.695–10.075 MAF—a range nearly three times bigger than CRAFT’s. As of August 3, 2025, WYTD observed inflow into Lake Shasta sits at 6.32 MAF.
Folsom Lake tells a similar story. The initial B-120 extended well above and below the CRAFT forecast, and then narrowed over time as the forecast adjusted to observed data. As of August 3, WYTD inflow is just shy of CRAFT’s lower limit but expected to verify by the close of the water year.
Further south at Millerton Lake, observed WYTD inflow is about 0.2 MAF below the CRAFT forecast. It’s important to note that going into the water year, the CAP model output (serving as the CRAFT model input) indicated drier conditions for the southern half of California. Because our ability to identify these precipitation gradients is still in early development, we made only conservative adjustments to the inflow forecast. This slight “miss” provides valuable feedback that will help us refine and improve how we interpret and apply model results moving forward.
CRAFT forecasts are available for 15 additional reservoirs. A complete list is available on the Weather Tools website.
CRAFT’s debut year proved its value, delivering steady, accurate inflow forecasts well before the traditional February B-120 updates.
A Forecast That Doesn’t Flinch
One key distinction between CRAFT and the B-120 is forecast stability and predictability. The B-120 shifts almost weekly through the spring, adjusting as new observations are available. CRAFT, on the other hand, provides a fixed forecast, issued early and unadjusted throughout the water year, giving managers a consistent range for planning operations.
Thad Bettner, a fixture in California water and former GM at Glenn-Colusa Irrigation District knows “when forecasts shift frequently, it’s tough for managers to confidently plan for a range of scenarios as well as develop strategies to mitigate risks.”
He noted that while most forecasts hedge with vague probabilities, CRAFT gives a fixed-range estimate early in the season. That changes how water managers think about planning.
“The sooner you have confidence in the forecast, the sooner you can act. Even if you don’t change your systems or operations, you can change the conversation—with your board, with your partners, with landowners. And that really matters.”
How Timing Changes the Game
The implications of a forecast issued the first week of November that holds through spring are significant.
Justin Hopkins, General Manager at Stockton East Water District (SEWD), oversees critical water operations for New Melones and New Hogan reservoirs. SEWD leverages both CAP and CRAFT to guide the district’s water year strategy. Hopkins reflected on the impact of early insights: “Before CRAFT, we’d wait until we received a final allocation—sometimes as late as May—before using any water. But this year, relying on CRAFT’s early forecast, we started releasing water well before a final allocation was confirmed. That kind of confidence lets us operate more efficiently and get ahead instead of waiting around.”
Randy Fiorini, lifelong farmer and former Turlock Irrigation District (TID) board member, believes that if CRAFT had been available during his tenure at TID, it would have added significant decision-making rigor to an already well-managed water operation.
“Precipitation and runoff forecasting is critical to effectively, efficiently, and safely managing a major reservoir in California. Now a reliable precipitation forecast is available in November. CRAFT is a big technological leap forward, informing decisions about releases, recharge, and providing much earlier, more strategic warnings for managed flood control actions,” he says.
Confident Water Decisions Start Here
CRAFT isn’t just about forecasting inflow earlier. It’s about transforming how and when water decisions are made.
As agencies look for tools to support long-range planning, CRAFT offers something rare: accurate insight that arrives early and remains consistent throughout the season.
After years of navigating California’s unpredictable water supplies, Hopkins says, “I definitely recommend CRAFT. This first year with it, it’s been incredibly useful. It almost feels like we’re ‘cheating the system’ because we have a better idea of what the water year will bring.”
Bettner doesn’t mince words, “Here’s your forecast. Use it. Don’t wait until you’re scrambling in crisis mode. It will change how you plan, how you manage, and how you prepare for the future.”
Jackie Miller is the Manager of Data & Product Services at Weather Tools, where she combines a curiosity about weather data with a passion for storytelling. She leads the development of monthly forecast reports, using numbers and narrative to bring clarity to customers navigating complex water year decisions. You can reach her at Jackie@weathertools.org
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