CalSim 3

Criterion	Explanation
General Description	CalSim 3 is a model for water resources management that optimizes operation and allocation decisions in California's Central Valley. It is based on an underlying model called WRIMS (Water Resource Integrated Modeling System) that has its own domain-specific language (WRESL) for describing operational criteria and translating them into a linear programming problem. It is an update of the CalSim II model that has been in use since 2002.
Model Domain	CalSim 3 is specifically an implementation of the areas served by the California State Water Project (SWP) and Central Valley Project (CVP) operations. It is intended to be the successor of CalSim II, a similar model used for official publications by the state of California, including its delivery reliability reports as well as by the wider modeling community.
Developer	CA DWR
Hardware computing requirements	XA Solver Hardware Key if using XA solver, although this is not the default solver in CalSim 3
Code language	C++ (default Cbc solver) / WRESL (model implementations) / Eclipse (GUI environment) / FORTRAN (XA solver)
Original application	Water operations and allocations for California Central Valley
Public/proprietary and cost	CalSim model: GNU GPLv3 XA Solver (required for reference implementation of CalSim II, other options are the default for CalSim3): Proprietary, $1650
Physically or empirically based	Empirically based, with a focus on optimization to meet numerous flow and diversion constraints.
Mathematical methods used	Surface water is represented as a network of nodes and channels. Model objectives and constraints are optimized via Linear Programming; certain processes (e.g. Delta salinity objectives and groundwater storage) are approximated and linearized in calls to DLLs implementing artificial neural networks (Delta salinity) or IWFM code (groundwater)
Input data requirements	Reservoir inflows, valley precipitation, and operation objectives encoded as WRESL statements. A completely novel scenario involves extensive upper watershed modeling and careful representation of operational criteria in the WRESL framework.
Outputs	Outputs stored in DSS file (file format developed by Army Corp of Engineer's HEC) and include reservoir outflows and allocation decisions on a daily timestep.
Pre-processing and post-processing tools	There is a WRIMS GUI built in the Eclipse framework that can help process and edit the model's (WRESL) files.
Representation of uncertainty	No explicit representation in the model output; could be implemented with multiple scenarios
Prevalence	This model is a new generation of CalSim II, which is the de-facto standard for planning California Central Valley operations and Delivery Reliability Report studies. Use outside of DWR is limited thus far, but userbase is expected to increase over the next several years
Ease of use for public entities	Documentation and tooling are improved compared to CalSim II; the biggest challenges are related to the transition period associated with rewrites of large software models
Ease of obtaining information and availability of technical support	There is a CalSim user group, and DWR support contacts can answer some classes of self-contained questions.
Source code availability	The model is licensed under GPL, but model source would need to be requested. Source code of certain model DLLs (salinity ANNs) does not appear to be publicly available
Status of model development	Model has been released to the public, and development will likely continue as more applications become focused on CalSim 3 instead of its predecessor
Challenges in integration	Based on the model complexity, offline integration as used in many CalSim 2 studies, may be appropriate.

References:
Department of Water Resources (2019) CalSimHydro Model Manual, available online at: https://water.ca.gov/Library/Modeling-and-Analysis/Central-Valley-models-and-tools/CalSim-3

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