_(Released November 17, 2022)_ The California Central Valley Groundwater–Surface Water Simulation Model - Coarse Grid (C2VSimCG) is an integrated hydrologic model that simulates the movement of water through the linked land surface, groundwater, and surface water flow systems in the 20,000 square mile area defined by the alluvial Central Valley Aquifer. C2VSimCG was developed using the Integrated Water Flow Model (IWFM2015) application, an open-source software package that couples a three-dimensional finite element groundwater flow simulation component with one-dimensional land surface, stream flow, lake, unsaturated zone, and small-stream watershed components. C2VSimCG Version 1.0 dynamically calculates crop water demands, allocates contributions from precipitation, soil moisture and surface water diversions, and calculates the supplementary groundwater pumping required to meet the remaining unmet consumptive water demands. The model simulates the response of the Central Valley’s groundwater and surface water flow system to predefined stresses and can also be used to simulate the alternative scenarios. Two applications of the C2VSimCG v1.0 are available: __Historical Run:__ Simulates the historical period for water years 1974 through 2015. The input data uses historical values for precipitation, land use, evapotranspiration, reservoir releases, and surface water diversions. Required groundwater pumping is computed dynamically. __Baseline Runs:__ The baseline model represents “Existing Conditions” and serves as a representation of the historical hydrology with a current level of land use development and water demands. The C2VSimCG Baseline model can be run with two sets of initial conditions for groundwater levels: pre-drought conditions (representing Fall 2010-2012) and post-drought conditions (representing Fall 2018-2020). Each simulation runs for water years 1922-2015, a period of 94 years.