Nitrate pollution in groundwater in two selected areas from Cameroon and Chad in the Lake Chad basin

The shallow aquifer in the Lake Chad basin is highly vulnerable to pollution. Analysis carried out on 316 wells and boreholes have showed a tendency towards an increase of nitrate values, exceeding 50 mg l−1. Nitrate concentrations ranged between about 1 and 300 mg l−1. Large variation in concentration was observed in wells and boreholes that are only short distances apart. High concentrations of nitrate in wells, especially in a recharge area along the sand dunes, or via infiltration from river banks, irrigation channels, and infiltration of urban wastewater into groundwater from septic tanks, pose a serious problem for drinking water supply. In Cameroon and Chad, the results of the investigation indicate a variation of nitrate concentration in groundwater between the two areas. The primary origin of this pollution is agricultural proliferation activities that are developed and stressed by socio-economic needs outside the urban area, and by urban expansion within the area served by a decrepit network of urban area sewers. Substancial differences in values of nitrate concentrations were observed in groundwater from adjacent wells and boreholes, indicating local rather than regional contamination.