The report from California State Auditor Grant Parks finds, generally, that DWR’s forecasts don’t “adequately account” for climate change and its reasons are unclear for “some reservoir releases.” In its response, DWR said it “respectfully disagrees” with the finding that it has been “slow to account for the effects of climate change on key responsibilities related to managing the State’s water resources” — and points out that it established a climate change program in 2008 and has regularly released phases of its Climate Action Plan. DWR also said it “contends otherwise” on the releases charge, indicating it “maintains records and detailed data sufficient to demonstrate the rationale for reservoir releases.” Among the takeaways:
- The Auditor recommended DWR “implement a forecast verification process by November” to make water supply forecasts as accurate as possible. This, the report said, should include annual evaluations of the forecasts’ accuracy; identification of the likely causes of errors on the side of “greater-than-expected”; yearly assessments of “opportunities for improvement and enhancement, including identifying and evaluating available and emerging forecasting technologies”; and annual reporting on its online page for water supply forecasting to inform the public on “steps it is taking to improve and enhance the accuracy and predictive capability of its forecasts.”
- The Auditor recommended that DWR “continue to implement its plan to adopt an updated water supply forecasting model and updated procedures,” to ensure forecasts of water supply do a better job of accounting for the effects of climate change. It recommended that by November, DWR put a timeline on its website indicating when it will stand up its updated model and procedures; set and publish the criteria it will use to ascertain when the updated model is sufficiently capable to be used; and do annual online updates on the model and procedures’ implementation. In its response, DWR said it “appreciates and will implement” the recommendation it create a “formal process to evaluate forecasting models”; and it agrees “a public-facing web page with annual updates would be helpful for both the department and stakeholders.”
- DWR enumerated its areas of completed improvements from June 2021-February 2022. These included narrowing hydrological data sets to 1991-2020 from earlier years to “better reflect the effect of climate change on snow, precipitation and runoff”; developing new statistical models based on “updated, 30-year hydrology using machine learning techniques”; improved automation of “daily and monthly data collection and calculations”; and setting a new methodology to evaluate and improve “90 percent and 10 percent exceedance forecasts.” The department has also expanded machine learning to “better classify data based on new climate change models”; trained staff on iSnobal, a “physically based distributed snowmelt model,” to “support Aerial Snow Observatory work”; and developed iSnobal models for watersheds in Tuolumne, Merced, San Joaquin, Kings and Kaweah counties. It has also launched a pilot with Airborne Snow Observatories Inc. and the National Center for Atmospheric Research to “develop coupled atmosphere watershed models in the San Joaquin and Feather River watersheds.”
- DWR said in its responses to the audit a shift is “well underway” at the department from a “statistical, record-based forecasting model” to water supply forecasts that “simulate the physics of interactions among the atmosphere, water as rain or snow, and the land surface,” for individual watersheds. This necessitates “substantial financial and human resources,” it said. The department is working with federal partners including NASA, the United States Geological Survey, and the National Oceanic and Atmospheric Administration on coordinating the development of “forecasting and water management capabilities for the benefit of all.” DWR is also “strengthening its partnerships with land stewardship agencies” such as the U.S. Forest Service, the National Park Service, and the California Department of Forestry and Fire Protection for “better observations that support better resource management across the watersheds.” And it continues working with academic partners to take “the best elements of emerging technology and analytical techniques from a research concept to operational implementation.”
“While not every technology or model makes a successful transition, sustained partnerships ensure that the state has the opportunity to keep pace with climate change and its water-related impacts,” DWR said in its response.
