The goal of this research is the creation of a non-point source pollution water quality model using a Geographic Information System. The area chosen for the study is the City of Austin, which partly overlays the recharge zone of the Edwards Aquifer. A model based on raster data that takes into account the presence of the recharge zone was created both in ArcView and in Arc/Info for mean annual flows and pollutant loadings. The model is able to perform the following tasks: 1) compute current pollutant loadings for TSS, BOD, COD, TOC, DP, TP, NH3, TKN, NO3, TN, Cu, Pb and Zn, 2) compute future loadings for the year 2040 for the same constituents, 3) model the effect of located and regional Best Management Practices. The model was designed so that it could deal with different sets of input parameters and locations.