## 3 Results and Discussion
### Groundwater Quality and Assessment for Drinking  
The pH of the water samples ranges from 6.94 to 8.34 in 2013 and from 6.82 to 8.2 in 2016. All samples are within the acceptable limits for human consumption, which vary between 6.5 and 8.5 [43]. However, for 2019, these values vary from 4 to 7.4, indicating that they are not within the permissible limits. Groundwater temperature values range from 19.1 \({}^{\circ}\)C to 27.8 \({}^{\circ}\)C in 2013, showing that some samples are off limits. Temperature measurements for 2016 and 2019 range from 18.4 \({}^{\circ}\)C to 24.3 \({}^{\circ}\)C and 17.1 \({}^{\circ}\)C to 21.8 \({}^{\circ}\)C, respectively. This may indicate that they meet the 25 \({}^{\circ}\)C guideline for drinking water [43]. The electrical conductivity of groundwater ranges from 1.8 to 6.7 ms/cm in 2013, from 1.2 to 11 ms/cm in 2016, and from 0.7 to 2.07 ms/cm in 2019. The TDS values range between a minimum of 928.52 mg/L and a maximum of 4052.82 mg/L in 2013, between 1106.51 and 11,589.5 mg/L in 2016, and from 1009.234 to 696.231 mg/L in 2019. This may indicate that all groundwater samples have TDS values above normalized limits, with the exception of wells 8 and 9 in 2013 [43]. According to the classifications of [44; 45; 46], groundwater in the study area is predominantly brackish and, therefore, not suitable for human consumption. The spatial distribution of major ion concentrations displays a wide range of variation. The sodium contents vary from 89.69 to 828.75 mg/L in 2013, from 150.88 to 2838.3 mg/L in 2016, and from 168.9 to 1482 mg/L in 2019. This suggests that all samples were above the WHO standard of 200 mg/L, with the exception of wells 7, 8, and 9 in 2013; well 13 in 2016; and wells 2 and 13 in 2019. Sodium contents increased over time from 2013 to 2019 in the same direction as groundwater flow. However, in the northwestern part of the basin, groundwater samples collected from wells 1, 2, 3, 5, 10, and 14 exhibit sodium concentrations that decrease over time. Calcium concentrations that gradually increase in the direction of flow and over time vary from 106.72 mg/L to 705.57 mg/L in 2013, from 97.13 mg/L to 869.7 mg/L in 2016, and from 102.7 mg/L to 1013 mg/L in 2019 (Figure 6). The desired drinking water limit for Ca\({}^{2+}\) is set at 75 mg/L [47]. According to the standard guideline values, all groundwater samples are unsuitable for drinking water. These higher concentrations are mainly related to natural mineralization processes, such as the dissolution of carbonate and evaporative minerals and cation exchange [36]. Consequently, the optimal concentration of Ca\({}^{2+}\) prevents heart disease and supports the normal functioning of the human metabolic process. The spatial distribution maps (Figure 6) show that Mg\({}^{2+}\) concentrations, which vary significantly between 34.15 and 216.3 mg/L in 2013, increase from south to north of the study area from 32.21 to 254 mg/L in 2016 and between 60.34 and 273 mg/L in 2019. The majority of groundwater samples are characterized by Mg\({}^{2+}\) concentrations above the WHO-proposed allowable limit (150 mg/L), which can be explained by the dissolution of dolomite and/or epsomite. They provide drinking water that exceeds the recommended limits for Mg\({}^{2+}\) and increases the risk of cardiovascular disease and a serious drop in blood pressure [48]. The chloride content shows an overall trend with an increase from upstream to downstream. They range from 102.95 to 1996.87 mg/L in 2013 and from 111 to 1005 mg/L in 2019. However, in 2016, the chloride concentration varied between 161.99 and 5564.6 mg/L, with a maximum measured toward the south eastern part of the basin, near Oued Meliane, highlighting the significant impact of wadi wastewater on groundwater contamination (Figure 7). Taking into account the WHO-permitted chloride limits for drinking water of 250 mg/L, all groundwater samples exceed the WHO guidelines. High concentrations of chloride in drinking water can result in repeated vomiting and diarrhea [49].