GIS-BASED SPATIAL MODELING FOR GROUNDWATER EXPLORATION AND DEVELOPMENT

A GIS-based spatial modeling tool that solves a modified version of Cooper-Jacob’s solution to solve for pumping rate rather than drawdown was developed to estimate potential aquifer yield while incorporating hydrogeologic data, aquifer pumping test results (transmissivity and storativity), and regulatory guidelines. The model was written using ESRI’s ModelBuilder and Python open-source script. The finished script was added to an ESRI ArcToolbox as a tool. Model output included interpolated surfaces for the top of aquifer, bottom of aquifer, aquifer thickness, available head, available drawdown (equivalent to a 50% threshold requirement), water elevation, and potential aquifer yield in gpm. The model calculates the potential aquifer yield for a pumping well so that water levels in an observation well a certain distance from the pumping well stays in compliance with the regulatory 50% drawdown threshold requirement. The distance to this compliance well is an input of the tool and is the radius variable of the Cooper-Jacob equation. Results were verified using existing aquifer test data and analytic techniques to validate the model’s performance.

Many benefits were gained by creating a tool that facilitated rapid development of surfaces to illustrate the hydrogeologic regime of the project area. The greatest benefit of the tool was realized when running multiple processing scenarios. What used to take hours to process manually could now be done in seconds, leaving more time for data analysis rather than data processing. As a result, this tool allowed for rapid identification of potential production well locations that would minimize potential well interference and comply with regulatory requirements. A 30-day aquifer pumping test of the study area was conducted in July 2011 providing additional calibration and validation of the model.