SACRAMENTO, Calif. (CN) — The California state auditor blasted the Department of Water Resources for failing to properly plan for climate change, and for a lack of transparency around water management decisions.
California has experienced increasingly extreme conditions including multiple droughts and floods. During drought emergencies, the state sometimes curtails water allocations due to forecasts that the water supply is too low to meet all water demands. State law requires the department to develop annual forecasts of seasonal water supply, including surface water from rain and snowfall runoff, which local agencies can rely on to determine the supply within a water year.
But State Auditor Grants Parks said in a report Thursday that the agency’s forecasts are unreliable due to outdated models, causing errors. Such errors can potentially lead to projects releasing more water from reservoirs or exporting less from the Sacramento Delta. The department's overestimation of inflow for Folsom Lake in 2021 caused the operating district to forego diverting about 925 acre-feet of water into storage — the amount used by 2,750 households in a year.
The department says it has a plan to improve forecasts, and piloted a new model in certain watersheds in 2022. But Parks said the plan does not include accountability mechanisms or specific criteria for determining whether the new model is accurate. He said the agency must improve those forecasts, switching from using historical medians to develop future estimates to account for other hydrologic processes, like soil moisture and the effect of rain on snow.
The agency also has not developed a long‑term plan for managing the State Water Project, which stores and delivers water from the north to the San Francisco Bay Area and Southern California, to nearly 27 million Californians and 750,000 acres of farmland.
“By not updating its 2010 drought plan in more than a decade, DWR has missed opportunities to incorporate into the plan the lessons learned from the significant drought and dry periods that occurred during that time,” Parks said.
Parks also said the department lacks transparency around decisions for what to do with reservoir water, for example at Lake Oroville. Federal law requires the department to operate Lake Oroville for flood control purposes.
Parks said the agency has not maintained documents explaining how it decided that releases from the lake in 2021 and 2022 were appropriate. The department released about 153,000 acre-feet — or about twice the amount the U.S. Fish and Wildlife agreement requires — in 2020. In 2021, it exceeded the minimum releases required by the agreement by more than 18,000 acre-feet — enough for about 54,000 households for one year — without any internal records explaining why.
The department also has not incorporated an assessment of the effects of climate change into its near‑term operations. Since 2005, it has based initial November estimates of the project’s water supply on historical data, which does not account for extreme conditions.
Parks recommends that the agency implement a forecast verification process by November, with public, annual evaluations of monthly forecast accuracy and opportunities for improvement. He said the agency should publish a public timeline affirming when it will implement an updated model across all watersheds, and criteria used to determine when that model has demonstrated the capability for use in all watersheds.
By May 2024, the agency should develop a long‑term plan for proactively mitigating and responding to the effects of severe drought on the State Water Project. It should also include strategies to mitigate the effects of drought while achieving project goals, with a policy to document monthly and annual plans for operating the project – including the rationale behind determining how much water to release, store and export.
DWR should also develop a formal, written process for reviewing planning and operations at least once annually, Parks said.
The auditor said that the manager of the agency's forecasting unit disagreed that it delayed updating the forecasting model to account for the effects of climate change. But he acknowledged the 2021 forecast errors illustrate the importance of shifting away from statistical approaches relying on historical records that no longer reflect observed conditions.
In a published response, the department disagreed with most findings and recommendations from the audit.
“Multiple DWR initiatives mitigate the effects of climate change including severe droughts on the State Water Project,” said director Karla Nemeth. “Those initiatives — some complete, others underway — are not encapsulated in a separate document called the ‘long-term drought plan,’ but these initiatives nevertheless constitute a comprehensive strategy to mitigate the effects of future droughts.
“We recognize the importance of forward-looking forecasting that embraces extremes,” she added.
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