Evaluation of the quality of groundwater for its appropriateness for drinking purposes in the watershed of Naâma, SW of Algeria, by using water quality index (WQI)

Naâma watershed is situated in the southwest of Algeria, where the climate is arid. It is highly dependent on groundwater resources, which are the only available resources for irrigation and domestic purposes. The study was carried out to assess groundwater appropriateness in the study area for drinking uses through a water quality index (WQI) and geographic information system (GIS). Fourteen (14) groundwater samples were collected, and several physicochemical parameters such as electrical conductivity (EC), potential for hydrogen (pH), total dissolved solids (TDS), cations (Ca, Mg, Na, K), and anions (SO4, NO2, HCO3, Cl) were analyzed. The results report that the different water quality parameters were within the permissible limit given by the World Health Organization and Algerian Standards guidelines, except for some boreholes near the Sabkha of Naâma. Eleven (11) parameters were chosen to compile the water quality index. The results showed that 50% of groundwater sites sampled in the study area had excellent water quality, while 50% were suitable. By carefully examining the data, it was revealed that boreholes distant from Sabkha present an excellent groundwater quality, where the WQI ranges between 37 and 41.6 mg/L. On the other hand, the boreholes close to Sabkha are characterized by a high concentration of electrical conductivity, TDS, sodium, and sulfates, explained by the contamination of the surrounding area through the infiltration of salt elements from the Sabkha. This salt contamination of groundwater would be accentuated by the discharge of wastewater from Naâma town into the Sabkha, the irrational use of chemical fertilizers, pesticides, and intensive pumping. The spatial distribution of the physicochemical parameters and water quality index was generated using the inverse distance weighted interpolation method (IDW). This study demonstrates that the combination of WQI and GIS methods could be a helpful tool for water resources management and decision making.