Problems with Bay-Delta water resources modeling have been recognized for decades

The drought years of 2021 and 2022 saw major errors in the Department of Water Resources’ Bulletin 120 runoff forecasts and Delivery Capability Report water supply projections. The Joint Legislative Audit Committee authorized an audit of DWR’s modeling and water management on June 27, 2022. But the model errors are part of larger institutional issues with development and external review of modeling for water resources management, which have been recognized for decades by the Bay-Delta modeling community.

On June 9, 2009 — thirteen years ago — modelers and researchers from state and federal agencies and universities sent a letter to the CALFED Director and CALFED Lead Scientist, titled, Re: Improved Modeling Capabilities Needed for the Bay-Delta Planning Effort. The letter proposed the following:

Longer-term responsibilities for the CALFED Science Program and the community of Bay-Delta modelers include elements of education, evaluation, development, licensing, research, and regular peer-review as part of a commitment to establishing and maintaining a state-of-the-art group of model developers, users, and interpreters. These elements are often discussed within the Bay-Delta modeling community, and there is broad-based support for collaboration and coordination for longer-term model and modeler improvement.

… We recommend that the proposed program include the following:

    • Use of the diverse model and data development talents and capabilities already existing in California’s agencies, universities, and consulting firms
    • Establish community-wide 2-year, 5-year, and 10-year goals for strategic model development
    • Leadership that maintains a consistent application-oriented scientific perspective and maintains focus on achieving strategic modeling goals (2-yr, 5-yr, 10-yr)
    • Requirement of product completion according to 2-, 5-, and 10-year schedules to satisfy near-term modeling needs
    • Proper mathematical verification of model codes and calculations, field testing of models, and peer-review of model algorithms and documentation
    • An external review committee to provide outside scientific advice, oversight, and quality assurance, drawing on expertise from other estuaries
    • Model codes and documentation made freely available in the public domain
    • Identification of a caretaker of model codes and documentation
    • Programmatic investment of $3 million/year for 5 years to support these recommendations

(Underlining added.)

Several months later, the Delta Reform Act of 2009 was passed, and the Bay-Delta Authority was dissolved. The modeling community’s proposal to do proper verification and field-testing of models, as well as peer-review of model algorithms and documentation, was never implemented.

It took a decade for the CALSIM III water operations model to be released. Deliveries in 2021 and 2022 have been 15-23% of model projections for 2-year and 4-year droughts. The model could have created systemic drought vulnerability for water agencies dependent on water from the State Water Project.

The proposal in the 2022-23 Senate Climate Budget Plan to provide $100 million in funding for water management science would be an important and needed step. The Senate’s proposal includes the Delta Independent Science Board, but the Delta ISB would need additional funding to be able to do adequate external reviews.

Further Reading

Anderson, J. Ateljevich, E., Burau, J., Bombardelli, F., Culberson, S. DeGeorge, J., Enright, C., Fleenor, W., Fris, R., Gowdy, M., Gross, E., Fleenor, W., Fris, R., Gowdy, M., Gross, E., Hutton, P., Kawakami, A., Lund, J., MacWilliams, McDonald, A., Monismith, S., Monsen, N., Mueller-Solger, A., Sereno, D., Smith, P., Stacey, M., Smith, T., Wong, H. 2009. Letter Re: Improved Modeling Capabilities Needed for the Bay-Delta Planning Effort.  June 9, 2009.

Related blog posts:

Fatal errors in DWR’s runoff forecasting: comments to the State Water Resources Control Board. March 18, 2022

Senate Climate Budget Plan proposals on water management science. May 30, 2022.

The State Water Project Delivery Reliability Report may have created systemic drought vulnerability. June 16, 2022.

Legislature approves audit of water management by DWR and SWRCB during 2021. June 28, 2022.




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