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Groundwater Model

graphic of a groundwater modelGroundwater modeling is an important part of many hydrogeologic projects as it provides a complex and robust tool to evaluate groundwater conditions and provides a means for evaluating solutions to various scenarios and problems while incorporating changes in conditions with time.

A groundwater model for the Mid-County groundwater basin is being developed to better evaluate the effectiveness of proposed long-term water resources projects and guide solutions to the overdraft conditions and seawater intrusion. This computerized model will utilize GSFLOW, an integrated surface water-groundwater model developed by the US Geological Survey (USGS). (link to  The Department of Water Resources regulations for Groundwater Sustainability Plans set surface water-groundwater models as best available science for evaluating projected groundwater conditions.

Uses of Groundwater Model:

  • Evaluating historic and projected water budget
  • Comparing projected groundwater levels to protective elevations for preventing seawater intrusion
  • Estimating the time needed to achieve basin recovery, i.e. raise groundwater levels to protective elevations, under various pumping and recharge/injection scenarios
  • Assessing the impact of various pumping and recharge/injection scenarios on ongoing seawater intrusion
  • Evaluating the impact of various pumping and recharge/injection scenarios on streamflows
  • Coordinating pumping between water agencies

A Technical Advisory Committee has been established to provide guidance and input on the model's development. The TAC members are: Bruce Daniels, Andy Fisher, Barry Hecht, Brian Lockwood, and Robert Marks.  The TAC has reviewed the draft technical memorandums posted to this website, but model documentation is subject to change as the model undergoes ongoing development and calibration.

The figure below shows the model area compared to the basin boundaries as well as the hydrostratigraphic unit outcrops for the nine layer model.

A recording of the Groundwater Model webinar presenting information on the model and its uses on February 11, 2019.

A presentation was given at Orientation Session #4 all about the groundwater model, which is available to view on the Orientation Sessions page.

The documents below provide detailed information about the Model:

Model Uses and Capacities

Model Scope for FY 2016-2017

Technical Memo, Climate, Aug 2017

Technical Memo, Simulation Concepts, Nov 2016

Technical Memo, PRMS, Aug 2016

Technical Memo, Subsurface Modeling, Nov 2015

Technical Memo, Boundaries

Work Plan_Basin Implementation Group