Assessment of Groundwater Vulnerability to Nitrate Contamination Using an Improved Model in the Regueb Basin, Central Tunisia

In recent years, Regueb basin has been facing groundwater quality degradation due to the excessive use of fertilizers and pesticides, which is the result of strong agricultural activities. Physicochemical elements (TDS, NO3-) and several factor types (geologic, hydrogeologic, and geomorphologic) were used in this study. The weighted model (TDLFSGC) was used to determine the groundwater vulnerability index (VI) to the pollution which is subsequently validated by Pearson correlation with nitrate concentrations. The results show that the TDS in groundwater ranged between 1.19 and 16.92 g/L and the NO3- concentrations varied from 150 to 920 mg/L. The vulnerability map generated using GIS shows three classes of VI in the study area, namely low (31.5-60), moderate (60-75), and high (75-13). The validation of the vulnerability model revealed a good correlation with NO3- and provided a high discretization of the groundwater vulnerability from anthropogenic pollution. This approach implies that more efforts should be taken to preserve the groundwater of the Regueb basin from contamination. And it could be used as a tool for water resource management in the future in similar regions.