Special to WaterWrights.net
Editor’s Note: Dear Readers, We at WaterWrights.net have come across what sure looks like a solution to the age-old problem farmers face regarding weather forecasts. Not knowing how much precipitation will fall during a water year delays allocations and waiting until April to find out how much snowmelt we’ll have does not allow for the best cropping decisions. Read on to see what Weather Tools has come up with.
A Case Study of CRAFT’s Proven Success at Lake Oroville and Millerton Lake: When Inflow Matters
At Weather Tools, we’re committed to solving our customers’ most pressing challenges by developing tailored solutions using our flexible, seasonal-scale Business Intelligence (BI) core.
The California Reservoir Annual Forecast Tool (CRAFT) allows us to meet the specific needs of water managers, ensuring they have the inflow data necessary to make informed decisions. As we prepare to release CRAFT commercially in November 2024, we wanted to showcase its performance with a look back at how the model performed for two of the sixteen reservoirs where CRAFT is active – the Feather River at Lake Oroville and the San Joaquin River at Millerton Lake.
Water managers across California face increasing challenges in managing reservoirs, balancing water supply and demand, keeping the public safe, and ensuring compliance with regulatory requirements. Inaccurate or untimely forecasts can lead to underutilized resources, missed opportunities, or even flood risks. In response to these challenges, and at the request of a water district manager, we leveraged our BI core to develop a reservoir inflow model. This model connects water year precipitation to inflow, with our California Annual Precipitation (CAP) forecast as the primary input.
A Hindcast of Our Inflow Model at Lake Oroville and Millerton Lake
To evaluate the performance of our model, we conducted a hindcast over the past eight years for all sixteen reservoirs ranging from Lake Shasta and Trinity Lake in the north to Lake Isabella in the south.
For each year, the CAP forecast—a range of California’s expected precipitation (rainfall and snow water equivalent) for the water year—served as the primary input into CRAFT. The inflow regression model then generated a corresponding range of expected reservoir inflow in millions of acre-feet (MAF) for each storage facility.
The results were remarkable across the entire portfolio. While we’ve chosen two reservoirs to highlight, these outcomes are representative of the model’s performance across all sixteen reservoirs. These results highlight CRAFT’s effectiveness in capturing the variability of inflow extremes. 
The lead time that CRAFT provides is as significant as its accuracy. Customers receive the water year inflow forecast during the first week of November, empowering them to make informed decisions and strategically allocate resources proactively, rather than reacting to mid-year updates. This greater lead time, and the fact that the forecast is never adjusted,
allows for reliable long-term planning and improved water storage decisions resulting in more efficient resource management.
Delivering Tailored Solutions with Proven Accuracy
Weather Tools is committed to finding solutions for the needs of the various industries we serve. This is done through our BI core which allows us to efficiently prototype solutions to a wide array of expressed needs. We invite you to contact our team, share your challenges, and explore additional tailored forecasting solutions that could empower you to make confident, data-driven decisions.
E-mail us at: rob@weathertools.org
or call (530-774-5475) to start the discussion.
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