ON THE DALLOL BOSSO WATER QUALITY: A CASE STUDY OF THE FILINGUE AND BALLAYARA DEPARTEMENTS GROUNDWATER

The main objective of our study is to improve knowledge on the quality of groundwater in the Dallol Bosso area, particularly in the departments of Filingu? and Balayara (Tillab?ry Region). Thirty-six (36) samples were taken from eighteen (18) water points in three (03) municipalities in these departments. Seventeen (17) physico-chemical and two (02) bacteriological parameters were analyzed, on site and in the laboratory. The so-called GOD method was used for water vulnerability assessment. The analyzed waters have an acidic pH with a neutral tendency in places, between 5 and 7.6. They are weakly mineralized with an electrical conductivity varying from 48.2μS/cm to 735μS/cm. The result of these analyzes show that the physico-chemical quality of the waters is acceptable. However, 83.3% of the water points in the study area are polluted with nitrates due to a probable influence of human activities. 33.3% of the samples analyzed contain a nitrate concentration above the maximum limit of 50 mg/L set by the WHO. The main source of mineralization in the waters of the study area is natural, with local anthropogenic inputs of nitrates and potassium. The results of the bacteriological analyzes revealed a large proliferation of bacteria indicative of contamination of faecal origin (Total and Faecal Coliforms). From a physico-chemical point of view, the quality of the waters in our study area is acceptable, but it is bacteriologically unfit for human consumption without prior treatment. These analyzed waters belong to 66.7% of the class (excellent for irrigation) and 33.3% of the class (good for irrigation). It appears that the groundwater table is vulnerable to pollution of all kinds throughout the study area. The degree of vulnerability varies from low to high and moderate. Thus, moderate vulnerability occupies 44.4%, the other two (low and high) each occupy 27.8%.