Groundwater modeling for a source water protection tool

Source water is defined as any untreated water that can be used by public drinking water supplies. Amendments made to the Safe Drinking Water Act (SDWA) in 1996 require all the states to develop and implement a US EPA-approved Source Water Assessment and Protection program (SWAP). Under this program the watershed managers need to delineate source water areas, identify potential contamination sources in these areas, and take preventive action against any possible contamination. A software tool called Source Water Assessment and Protection Tool (SWAPT) considers contamination due to over-land sources. This thesis describes the addition of a groundwater component to the SWAPT and an approach taken to analyze susceptibility of drinking water supplies to contamination from various point and non-point contaminant sources through the groundwater route. A tool was designed for the purpose of storing geographic information system (GIS) and the potential contaminant source (PCS) data and running hydrogeologic models to analyze the effect of various contamination scenarios on the point of diversion (POD) of the drinking water supply. The Ogden River watershed was used as the target watershed to demonstrate the abilities of the Source Water Protection Tool. MODFLOW was used as the groundwater flow model and MT3D was used as the subsurface contaminant transport model. A manual calibration interface was provided to help calibrate the flow model. Outputs from the models can be viewed in a graphical format, which makes it easier to understand the results of simulations. Instead of using an arbitrary, excessively restrictive or insufficiently protective source water protection zone delineation method, watershed managers can assess the actual threat of any pollution source in the watershed to the point of diversion using the Source Water Protection Tool.