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| CalSim II | |
|---|---|
| Name | CalSim II |
| Developer | United States Bureau of Reclamation |
| Latest release | 2012 |
| Operating system | Windows |
| Genre | Hydrology |
| License | Proprietary |
CalSim II is a regional water resources planning and operations model used for the Central Valley Project and State Water Project in California. It supports decision-making by simulating monthly and daily water supply, reservoir operations, and water deliveries under competing demands from agricultural, urban, and environmental stakeholders. The model is maintained and applied by public agencies, consulting firms, and academic researchers for planning studies, environmental compliance, and policy evaluation.
CalSim II is a modular, multi-reservoir simulation and optimization platform developed to represent system operations for the Sacramento River, San Joaquin River, Sacramento–San Joaquin River Delta, and associated conveyance facilities. The tool integrates physical infrastructure such as Shasta Lake, Folsom Lake, Oroville Dam, San Luis Reservoir, and the Delta-Mendota Canal with operational policies like the Central Valley Project Improvement Act and California State Water Resources Control Board water quality and flow standards. Users configure scenarios that reflect actions by institutions such as the California Department of Water Resources and the United States Fish and Wildlife Service. The model supports analyses used in proceedings before the California Water Commission, State Water Project Contractors, and Bureau of Reclamation planning processes.
CalSim II evolved from earlier water system models developed by the Bureau of Reclamation and the California Department of Water Resources during the late 20th century. Major development milestones involved collaborations with consulting firms such as AECOM, CH2M Hill, and research groups at University of California, Davis and Stanford University. Funding and program drivers included mandates from the Central Valley Project Improvement Act and court decisions arising from Bay-Delta water rights controversies. Key technical advances incorporated optimization techniques from linear programming practitioners and hydrologic data assimilation methods from agencies like the National Oceanic and Atmospheric Administration and United States Geological Survey.
The CalSim II architecture comprises modules representing hydraulic routing, reservoir mass balance, conjunctive use of surface water and groundwater linked with the Central Valley Groundwater Basin representations, and an operations optimizer. Core components include time-series inputs for unimpaired flow records from USGS stream gage networks, storage nodes for major reservoirs such as New Melones Reservoir, and conveyance transfer capacities like the California Aqueduct. The optimization engine encodes policy constraints derived from instruments such as the Endangered Species Act relicensing conditions for Central Valley steelhead and Delta smelt protections enforced partly by the National Marine Fisheries Service and the U.S. Fish and Wildlife Service. Scenario configuration uses parameter files, demand tables for agricultural districts like IID and Westlands Water District, and urban supplier profiles including Metropolitan Water District of Southern California.
CalSim II relies on multi-decadal hydrology traces including historic and synthetic unimpaired inflows from the Sacramento Valley and San Joaquin Valley basins, climate-informed projections incorporating datasets from PRISM Climate Group and CMIP output, and operational records from Bureau of Reclamation and California Department of Water Resources databases. Calibration procedures compare simulated deliveries, reservoir elevations, and outflows to observed records from agencies like USGS, DWR, and Reclamation; tuning addresses parameters such as conveyance losses, evaporation from reservoirs like Don Pedro Reservoir, and demand elasticity for districts like Central Valley Project contractors. Stakeholder-reviewed calibration reports have been produced for proceedings before the State Water Resources Control Board and for environmental analysis under the National Environmental Policy Act.
CalSim II is used for long-term planning studies assessing water supply reliability for entities including the Metropolitan Water District, San Francisco Public Utilities Commission, and agricultural districts such as Westlands Water District. It supports environmental analyses for Bay-Delta Plan processes, operations modeling for California WaterFix and Delta Conveyance Project alternatives, and cost-benefit studies for infrastructure such as reservoir expansions at Shasta Lake and conveyance upgrades along the California Aqueduct. The model has been employed in litigation contexts involving water rights adjudications, regulatory compliance analyses for Endangered Species Act consultations, and climate change impact assessments relying on Intergovernmental Panel on Climate Change scenarios.
Model validation compares CalSim II outputs to historical deliveries, reservoir levels, and Delta export records documented by Reclamation and DWR. Peer review panels including experts from University of California, Berkeley, Stanford University, and consulting firms such as HDR, Inc. have evaluated model structure and performance. Sensitivity analyses examine parameter impacts associated with datasets from NOAA and the USGS National Water Quality Program, while Monte Carlo and scenario ensemble approaches draw on statistical methods from Lawrence Berkeley National Laboratory and Scripps Institution of Oceanography to quantify uncertainty in projections.
Critiques of CalSim II emphasize aggregated temporal and spatial resolution that may obscure local processes affecting stakeholders such as small irrigation districts and regional water agencies like San Joaquin River Exchange Contractors. Concerns have been raised about representation of surface-groundwater interactions relative to detailed models used by United States Geological Survey groundwater studies, and about incorporation of ecological response metrics for species protected under the Endangered Species Act such as Delta smelt and Central Valley steelhead. Stakeholders have debated model transparency, documentation completeness, and the role of assumptions drawn from datasets maintained by California Department of Water Resources and Bureau of Reclamation during regulatory and litigation processes.
Category:Hydrology models