Abstract The Takelsa phreatic aquifer currently shows stress signs and the contamination risk of groundwater by different chemical elements and pesticides is a likely concern. Here we assessed the aquifer vulnerability using the Susceptibility Index (SI) method, considered as a specific vulnerability method that takes into consideration the impact of land uses chemical fertilizers, anthropogenic activities and natural factors as a source of contaminants in groundwater. WetSpass and MODFLOW models were applied to quantify groundwater recharge and water table depth, the two of the most important parameters in groundwater vulnerability mapping. The obtained recharge map for 2015 showed values ranging between 0 and 342 mm/year with an average value of 111 mm/yr, corresponding to about 16% of the annual average rainfall. Regarding the groundwater flow model and for a steady and transient state, a reasonable correlation between the observed and simulated values was obtained confirming that results can be used to establish the vulnerability map. The Susceptibility Index (SI) results showed that the groundwater vulnerability of the studied aquifer ranges from low to very high. Most of the area (90%) has moderate to very high pollution susceptibility mainly due to low slope, agricultural land, high recharge rate, sandy soil dominance and low water table depth. The validation of the obtained map was undertaken through a comparison of areas of high salinity hazard with their relative vulnerability index. For most wells, the different salinity hazard parameters matched with areas of moderate to high vulnerability. The integration between the SI method and WetSpass and MODFLOW models for the study area is a valuable and applicable approach for the assessment of the groundwater vulnerability.

中文翻译：

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使用敏感性指数 (SI) 方法绘制地下水脆弱性图：突尼斯东北部 Takelsa 含水层的案例研究

摘要 Takelsa 潜水含水层目前显示出压力迹象，不同化学元素和杀虫剂对地下水的污染风险可能是一个值得关注的问题。在这里，我们使用敏感性指数 (SI) 方法评估了含水层脆弱性，该方法被认为是一种特定的脆弱性方法，它考虑了土地使用化肥、人为活动和作为地下水污染物来源的自然因素的影响。WetSpass 和 MODFLOW 模型被应用于量化地下水补给和地下水位深度，这是地下水脆弱性绘图中最重要的两个参数。获得的2015年补给图显示值介于0至342毫米/年之间，平均值为111毫米/年，相当于年平均降雨量的16%左右。关于地下水流模型以及稳态和瞬态状态，获得了观测值和模拟值之间的合理相关性，确认结果可用于建立脆弱性图。敏感性指数 (SI) 结果表明，所研究含水层的地下水脆弱性范围从低到非常高。大部分地区（90%）具有中到非常高的污染敏感性，主要是由于低坡度、农业用地、高补给率、沙质土壤优势和低地下水位深度。通过将高盐度危害区域与其相对脆弱性指数进行比较，对获得的地图进行了验证。对于大多数井，不同的盐度危害参数与中度至高度脆弱性区域相匹配。