Issa Malam Salmanou Souleymane^1,, Abdou Babaye Maman Sani², Illias Alhassane³, Moussa Issaka Abdoulkader¹

The commune of Gouchi is located in the extreme south of the Zinder Region, resting on a sub-watershed of the Korama, and lies between 13°08' and 13°37' North latitude and 09°26' and 09°47' East longitude (). From a hydrogeological point of view, this zone is essentially underlain by Malawa sandstone and recent sand aquifers. This area, characterized by a high potential groundwater resource and an abundant ecosystem, has been subjected for many years to the phenomena of climate change, land use dynamics and galloping demography. This has resulted in changes to the quantity and quality of the commune's water resources. However, it seems necessary to undertake quantitative and qualitative studies of these groundwater resources, which are the main source of supply for the population, livestock and irrigation. The main objective of the present study is the hydrogeological and qualitative characterization of groundwater in the commune of Gouchi. The methodology adopted can be summed up in three stages: collection and campaign of measurements and samples; laboratory analysis of samples and, finally, processing and statistical analysis of hydrogeological, chemical and bacteriological data, and production of a piezometric map and hydrogeological cross-section. This led to the following results: From a hydrogeological point of view, the depths of the structures, taking into account all the water tables, vary from 2.70 to 49.93 m, with an average of 20.10 m, giving an average depth of 12.85 m. Static levels range from 0.52 m to 28.58 m, with an average of 4.86 m. Water flow rates are highly disparate, ranging from 0.2 to 30 m3/h, with an average of 5.46 m3/h. Furthermore, the piezometric map shows that the direction of groundwater flow is generally from north-west to south-east. This general trend follows the direction of flow of surface water, whose hydrographic network is more or less fossilized (Korama). This suggests that there may be a groundwater-river relationship. As for the chemical results of the 151 water samples, two (02), one hundred and twenty-one (121) and twenty-three (23) were characterized respectively by fluoride, arsenic and nitrate levels exceeding the WHO drinking water standard. Finally, from a bacteriological point of view, of the 151 samples, 56 and 42 showed respectively Total Coliforms (TC) and Escherichia. Coli in groundwater. This could be explained by the lack of hygiene around water points, combined with the shallow depths of the water in places. All these aspects can compromise the population's drinking water supply.

Arsenic, Bacteries, Gouchi, Malawa, Bassin Korama