PRELIMINARY STUDY ON THE GROUNDWATER RESOURCES OF THE KORAMA SUB-WATERSHED IN THE COMMUNE OF DOGO-DOGO/ZINDER REGION: HYDROGEOLOGICAL CHARACTERIZATION AND GROUNDWATER QUALITY

The commune of Dogo-dogo is located in the extreme south of the Zinder Region, in a sub-catchment area of the Korama River, between 12°50 and 13°00 North latitude and 9°10 and 9°32 East longitude. This area is hydrogeologically based on the aquifers of the Malawa sandstone formations, characterized by an important potential groundwater resource and an abundant ecosystem, and has been subjected for years to the phenomena of climate change, the dynamics of land use and a galloping demography. This has resulted in changes in the quantity and quality of the water resource in this area. However, it seems necessary to undertake quantitative and qualitative studies of this resource. The main objective of this study is the hydrogeological and qualitative characterization of groundwater in the town of Dogo-dogo. The methodology adopted was based on the processing and statistical analysis of hydrogeological, chemical and bacteriological data, the elaboration of a piezometric map and a hydrogeological cross-section, which led to the following results The depths of the works vary from 45 to 97 m with an average of 68.73 m giving rise to water column thicknesses of more than 20 m. While, the values of water exploitation flows are very disparate, they vary from 0,3 to 24 m3/h with an average of 5,05 m3/h. Furthermore, the piezometric map shows that the direction of groundwater flow is generally from NW to SE. This general trend tends to follow the direction of flow of surface water, whose hydrographic network is more or less fossilized (Korama). As for the bacteriological results of the water, out of the 111 samples, 84 and 72 show respectively Total Coliforms (TC) and Escherichia. Coli in the groundwater. This could be explained by the lack of hygiene around the water points in conjunction with the shallow depths of the water in some places. All these aspects can compromise the drinking water supply of the populations. Finally, from the chemical point of view on the 111 water samples, two (02) and three (03) of these samples are characterized respectively by Arsenic and Nitrate contents exceeding the WHO standard of water consumption.