C2VSIM (California Central Valley Groundwater-Surface Water Simulation Model)

Criterion	Explanation
General Description	C2VSIM is a model of surface and groundwater movement and consumptive use in California's Central Valley. It has been used to evaluate historical evolution of groundwater use for both agricultural and other uses. It has also been used to make projections for hypothetical scenarios, e.g. involving climate change.
Model Domain	C2VSIM is a specific implementation of the IWFM model to California's Central Valley. The model domain is the Valley floor and surrounding small-stream watersheds.
Developer	California Department of Water Resources (DWR)
Hardware computing requirements	None given. Should run with acceptable run-times on most modern personal computers.
Code language	The underlying numerical model, IWFM, is coded in FORTRAN.
Original application	Simulation of surface and groundwater flow, soil moisture, and consumptive water use in California's Central Valley.
Public/proprietary and cost	Distributed under the GNU General Public License v3.0; Free of charge.
Physically or empirically based	Physically based.
Mathematical methods used	Groundwater flow in the saturated zone is a numerical solution of the Richards' equation via the Galerkin finite element method. Surface flow routing to streams is pre-specified by the user with flow rates based on a Soil Conservation Service curve number approach. Surface flow routing between stream nodes is a mass balance approach with surface levels determined by a user-specified curve number. Evaporation for each land use type is user-specified as a time series input.
Input data requirements	This specific application requires outflows from CA Central Valley's major reservoirs, land-use information including surface water diversions, precipitation and evaporation time series. Accurate treatment of reservoir outflows and surface water diversions include consideration of California's system of water rights and environmental constraints. One common source of this information for a novel scenario would be a comparable simulation using Calsim, but there is not a clean correspondence between CalSim outputs and C2VSIM inputs in all cases.
Outputs	The default output setup is on the monthly timestep for 21 subregions of the Central Valley. Output includes surface and groundwater budget and consumptive use data. Modification of the post-processing scripts can be done to customize the spatial output.
Pre-processing and post-processing tools	There are plugins for ArcGIS to help view and interpret model results. See also information for IWFM model.
Representation of uncertainty	Not explicitly represented in output; could be implemented via multiple scenarios.
Prevalence	C2VSIM is one specific application of the underlying IWFM model.
Ease of use for public entities	Model documentation is detailed and understandable. The largest barrier to entry for a novel application is obtaining representative boundary condition data that takes into account California's water rights and environmental constraints.
Ease of obtaining information and availability of technical support	There is an IWFM users group, and the developers are able to respond to well-formulated questions.
Source code availability	The underlying IWFM source code is available on its website. The C2VSIM implementation is editable with typical text-editor software.
Status of model development	The model is mature and available for use.
Challenges in integration	The model is flexible, open-source, and well-documented, so few challenges exist to its modification for other uses. Input data dependent on water allocation decisions needs to be handled outside of the model.

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