Report 2022-106 Recommendation 1 Responses

Report 2022-106: Department of Water Resources: Its Forecasts Do Not Adequately Account for Climate Change and Its Reasons for Some Reservoir Releases Are Unclear (Release Date: May 2023)

Recommendation #1 To: Water Resources, Department of

To ensure that its B120 water supply forecasts are as accurate as possible, DWR should implement a forecast verification process by November 2023 that includes the following:

1. An annual evaluation of the accuracy of each of its monthly forecasts using multiple means in accordance with best practices, including an assessment of whether actual runoff fell within its probability range and an assessment of the accuracy of its median forecast.

2. Identification of the likely causes of greater-than-expected forecast errors.

3. An annual assessment of opportunities for improvement and enhancement, including identifying and evaluating available and emerging forecasting technologies.

4. The development and implementation of plans to improve its forecasts based on the findings from its annual evaluation.

5. Annual reporting on its water supply forecasting web page about the above actions so that the public is aware of the steps it is taking to improve and enhance the accuracy and predictive capability of its forecasts.

1-Year Agency Response

Department of Water Resources (DWR) has established the public-facing website where observations, forecast information related to the snowpack, annual evaluations, and progress on forecast improvement are posted. It is https://snow.water.ca.gov. DWR has published on this website for Water Year 2023 a technical discussion that identifies likely causes of forecast error in 2023 and an accompanying Hydrometeorological Summary for the water year, which allows readers to explore the month-to-month climate variability that may lead to forecast error. Forecast verification material, development documentation, and annual updates to the Roadmap to Climate Resilient Forecasting will be posted on the website as they are produced.

California State Auditor's Assessment of 1-Year Status: Fully Implemented

6-Month Agency Response

The implementation of improved forecast models, including the adoption of new and emerging technologies, is currently under development and will be implemented over a series of several years.

The Department of Water Resources (DWR) currently posts forecasting information on the California Data Exchange Center (CDEC) website (https://cdec.water.ca.gov/snow/) where forecast assessment data are available within Bulletin 120.

In addition, DWR will launch a new public website for the California Cooperative Snow Surveys Program (https://snow.water.ca.gov) in November 2023. The website will display regional and statewide snowpack conditions and include dashboards that provide water supply forecast verification, water supply data, and forecast comparisons.

The website will also include an annual evaluation of forecast accuracy and documents areas for improvements and implementation plans such as the Roadmap for a Climate Resilient Forecasting Framework (https://water.ca.gov/roadmap) for these improvements.

Additionally, DWR continues to expand information and data available on its existing public-facing website, California Water Watch (cww.water.ca.gov.) The site is a comprehensive resource for drought and precipitation information and is promoted to the public, media outlets, and interested parties on a regular basis.

California State Auditor's Assessment of 6-Month Status: Pending

60-Day Agency Response

The implementation of improved forecast models, including the adoption of new and emerging technologies, is currently under development and will be implemented over a series of several years.

The Department of Water Resources (DWR) currently posts forecasting information and tools on the California Data Exchange Center (CDEC) website (https://cdec.water.ca.gov/snow/) where forecast assessment data are available within Bulletin 120. In addition, DWR continues to perform forecast variance analysis annually.

California State Auditor's Assessment of 60-Day Status: Pending

All Recommendations in 2022-106

Agency responses received are posted verbatim.