A new GIS approach for estimating shallow groundwater recharge and discharge

Groundwater recharge and discharge define the relationships among groundwater storage, precipitation, evapotranspiration, and surface water. Understanding and quantifying groundwater recharge and discharge is crucial for developing effective management options for water supply. Traditional recharge and discharge studies usually require time-consuming (months or years) and labor-intensive field characterization. Therefore, a fast initial recharge and discharge estimation will help scientists and decision makers design more accurate and cost-effective research plans and management strategies. A new GIS based methodology along with an ArcMap plug-in package, PRO-GRADE, was developed to help hydrogeologists estimate recharge and discharge in a more efficient way than conventional methods. The Groundwater Recharge And Discharge Estimator (GRADE-GIS) in the PRO-GRADE package uses a mass balance approach for steady state two-dimensional unconfined aquifers. GRADE-GIS only requires relatively short preparation time (hours) using readily available data for water table and bedrock elevations, and hydraulic conductivities. The Pattern Recognition Organizer (PRO-GIS) in the PRO-GRADE package uses multiple image processing algorithms to estimate and visualize shallow recharge and discharge patterns and rates with GIS. The output of PRO-GRADE can be used as an initial guideline for conventional field study planning and decision making, or an initial condition for numerical simulations. © 2008 The Authors. Journal compilation © 2008 Blackwell Publishing Ltd.