Enhancement of the Aquifer Recharge Factor in DRASTIC Model using SWAT and GIS Techniques

The robustness of groundwater vulnerability assessment using the conventional DRASTIC model is highly dependent on the quality of the input data. The current research aims at examining the improvement of the Aquifer Recharge Factor (R) factor by utilizing and incorporating both SWAT model and GIS techniques. Two approaches were used to compare the use of conventional recharge map versus a SWAT-based recharge map in the DRASTIC model as to account for the level of aquifer vulnerability. To prepare a more accurate recharge map, ArcSWAT was used by utilizing four main factors (Land Use, Soil Cover including vegetation, Slope of surface and Weather). The remaining DRASTIC factor was prepared based on a conventional method with reliable data and two final DRASTIC outputs were developed. The results indicated that the newly developed approach using SWAT model for recharging map has resulted in a better resolution of DRASTIC vulnerability classes where the resolution was enhanced by 54%. Recommendation for further enhancement of the DRASTIC model is to incorporate more in-depth calculations of other factors including the A factor (Aquifer Media) and C factor (Conductivity) through more segmented calculations of the model cells leading into more accurate and higher resolution map outputs. This can be done by incorporating additional models, field data and refined calculations to improve the final results, thus improve the decision making process.