BY IAN JAMESSTAFF WRITER
MAY 27, 2023 5 AM PT
The state auditor has issued a report strongly criticizing the California Department of Water Resources, saying the agency has overestimated the state’s water supply during drought and continues relying on forecasts that don’t adequately factor in the effects of climate change.
The report by State Auditor Grant Parks said the Department of Water Resources has “made only limited progress” in improving its water-supply forecasts to account for climate change, despite acknowledging more than a decade ago that it needed to improve its forecasting methods.
The audit also concluded that DWR “has not developed a comprehensive, long-term plan” for the State Water Project, the system that delivers water from Northern California to Southern California and supplies almost 27 million Californians, to proactively respond to more severe droughts.
The auditor said that in 2021, amid the driest three-year period on record, DWR significantly overestimated the state’s water supply. In February of that year, the report said, the department projected that runoff would be at least twice the volume that actually flowed in the majority of the watersheds that are included in forecasts.
“DWR has continued to rely heavily on historical climate data when developing its forecasts,” the auditor said in the report. “DWR has since begun planning to adapt its forecasting model and associated procedures, but it could better ensure that it is using the best approach available if it adopted a formal process for evaluating the quality of its forecasts.”