Groundwater Quality Assessment for Drinking and Agricultural Purposes under Arid Climate in N’Djamena, Chad (central Africa)

The present study was carried out in the N’Djamena and Hadjer-Lamis localities (Lac Chad basin). The main objective was to examine the groundwater quality for domestic and agricultural purposes, using hydro-chemical modeling, Water Quality Index and Geographical Information System Technics. Thus, 66 groundwater samples were collected from 22 boreholes for physicochemical and biological analysis. The analytical parameters considered were: pH, electrical conductivity, Ca2+, Mg2+, Na+, K+, NH4+, HCO3−, NO3−, F−, SO42−, Fecal Coliform, Total Coliform, Escherichia Coli, Fecal enterococci and Mesophyll Aerobic Flora. The results revealed that groundwater of the studied zone presents a neutrality (6.40 ≤ pH ≤ 7.57), very weakly to weakly mineralized (92 ≤ electrical conductivity ≤ 590 µS/cm) with only one water type (Ca–Mg–HCO3), characteristic of the homogenous quaternary aquifer, the most used. The decreasing order of magnitude of the cations is as: Ca2+˃Mg2+˃Na+˃K+, while that of anions is HCO3−˃Cl−˃SO42−˃NO3−. The Water Quality Index varied from 188.41 to 866.89, corresponding to poor (9.09