San Luis Reservoir
San Luis Reservoir on May 29, 2019 (California Department of Water Resources)

Press Release Provided by the California Department of Water Resources

The Bureau of Reclamation and the California Department of Water Resources (DWR) today released the next versions of two computer models that simulate operations of the State Water Project (SWP) and the Central Valley Project (CVP). Water managers use the models – CalSim II and CalSim 3 – to examine project operations under various assumptions for hydrologic conditions, project  facilities and regulatory requirements.

“Having the ability to model events in a virtual world is a tremendous help in drought planning and improving sustainability of our water resources,” said Erik Reyes, DWR’s Supervising Engineer. “These highly complex and extensive models allow for studying a number of key changed conditions, including climate change.”

A beta version of CalSim 3 was originally released in 2017 for public comment. Since then several changes have been made to the model, including the full incorporation of the San Joaquin River, updated integration of groundwater and surface water interaction and new areas of simulation coverage in upstream watersheds. Both CalSim 3 and CalSim II, which are being updated from the last public release in October 2019, include refinements to the depiction of many regulatory criteria. 

“The inclusion of enhanced physical modeling in CalSim 3, particularly the implementation of stream-groundwater interaction, represents a great stride forward in analytical capabilities for Central Valley Project and State Water Project planning studies,” stated Derya Sumer, Reclamation’s Water Supply and Operations Analysis Branch Chief.

These and other improvements enhance the ability to model the ever-changing conditions that dynamically affect the projects, including impacts to infrastructure, operating or regulatory criteria, land uses and climate change. 

The models and preliminary documentation are available at Full documentation is expected to be made available in November 2021.

For more information about these benchmark studies or to provide comments, you may contact Erik Reyes, California Department of Water Resources,, (916) 653-5569; or Derya Sumer, U.S. Bureau of Reclamation,, (916) 978-5188.

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