Model files and technical memorandum for one-dimensional subsidence models that are discussed in DWR's DRAFT subsidence best management practices (BMP) document that is available at https://water.ca.gov/Programs/Groundwater-Management/SGMA-Groundwater-Management/Best-Management-Practices-and-Guidance-Documents.

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The Central Valley, and particularly the San Joaquin Valley, has a long history of land subsidence caused by groundwater development. The extensive withdrawal of groundwater from the unconsolidated deposits of the San Joaquin Valley lowered groundwater levels and caused widespread land subsidence—reaching 9 meters by 1981. More than half of the thickness of the aquifer system is composed of fine-grained sediments, including clays, silts, and sandy or silty clays that are susceptible to compaction. In an effort to aid water managers in understanding how water moves through the aquifer system, predicting water-supply scenarios, and addressing issues related to water competition, the United States Geological Survey (USGS) developed a new hydrologic modeling tool, the Central Valley Hydrologic Model (CVHM; Faunt and others 2009). The data presented in this data release will be used to facilitate updates to the original CVHM and represent subsidence and aquifer-system compaction observations (measurements) using various methods during 1926–2018. In the context of this report, subsidence is defined as the lowering of the land-surface elevation as a result of aquifer-system compaction and is calculated by differencing repeated elevation measurements derived from geodetic surveys, continuous GPS (CGPS), and Interferometric Synthetic Aperture Radar (InSAR) techniques. Aquifer-system compaction is measured using vertical borehole extensometers to monitor changes in the distance between the top of a cable or pipe that is anchored or placed at depth, and a reference point at or near land surface. For more detailed information on the methods discussed in this data release, please see Sneed and others, 2013; 2018).

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This digital dataset includes three sets of observational data (groundwater level, streamflow, subsidence) used to calibrate the updated Central Valley Hydrologic Model (CVHM2). CVHM2 is a tool that can be used to quantify the sustainability of groundwater resources in the Central Valley.

_(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.

The Department of Water Resources (DWR) has developed a new model, the Sacramento Valley Groundwater-Surface Water Simulation Model (SVSim). This new model will support two important DWR programs and has two main goals: 1) Water Transfer Program - develop a tool that meets essential modeling requirements for evaluating project-specific impacts of groundwater substitution transfers on stream depletion in the Sacramento Valley and: 2) Sustainable Groundwater Management Program - develop a tool for evaluating water budgets, surface water-groundwater interactions, and sustainable groundwater management scenarios in the Sacramento Valley. The intended users of SVSim are DWR, water transfer projects, Groundwater Sustainability Agencies, local agencies, and all other interested parties. SVSim is an application of the Integrated Water Flow Model (IWFM-2015) numerical code and is based on DWR’s C2VSim model (2013). SVSim provides an updated analysis of geologic and hydrogeologic data for the Sacramento Valley and adjacent areas. The model domain includes the Sacramento Valley Groundwater Basin, the Redding Area Groundwater Basin, and the Delta. The southern model boundary lies between the Mokelumne and Calaveras Rivers. SVSim includes nine (9) layers of variable thickness that span the entire groundwater system. The base period of the model simulates conditions from 1973 to 2015. A calibrated version of SVSim Version 1.0 is now available. The model input files, output files/data, and the executable program for SVSim Version 1.0 are available for download below. Version 1.0 supersedes the SVSim Beta Version released in April 2020). Documentation of SVSim model design, input data development, and model calibration and sensitivity analysis is also available.

This digital dataset contains datasets used to develop the Subsidence Package in CVHM2. Data includes number of delay interbeds per model cell (Neq), equivalent thickness for a delay interbeds (Beq), and the zones used to define subsidence parameters. Beq and Neq are calculated from the database of well logs, which is provided in the parent dataset. Eight zones are used to define subsidence parameters.