International Science Community Association International Research Journal of Earth Sciences 14 2 2026 08 25 Hydrogeochemistry of boreholes’s waters from Continental Terminal, basement rock and Korama geological formations (Zinder, Niger) 1 7 EN Issa Salifou 1 Multi-purpose Laboratoire Polyvalent, Diffa University, PO Box: 78 Diffa, Niger and Department of Water and Fisheries Resources, High Institute of Environment and Ecology, Diffa University, PO Box: 78 Diffa, Niger Anabi Toudjani Assane 2 Department of Water and Environment, Faculty of Agronomic and Ecological Sciences, Diffa University, PO Box: 78 Diffa, Niger Maman Maazou Ahmed 3 Faculty of Agronomic Sciences and Food Technologies, Boubacar Bâ University of Tillabéri (UBBTi), PO Box: 175 Tillabéri, Niger Adamou Zanguina 4 Department of Chemistry, Faculty of Science and Technology, Abdou Moumouni University, PO Box: 10662 Niamey, Niger Natatou Ibrahim 5 Department of Chemistry, Faculty of Science and Technology, Abdou Moumouni University, PO Box: 10662 Niamey, Niger > Research Paper 2026 6 4 2026 08 25 In arid and semi-arid areas, surface water resources are scarce or totally unavailable during the year. Consequently, groundwater resources remain the principal source of drinking water. In addition to this, there are some variations in water mineralization across different areas within the same aquifer. The present study aimed to understand the hydrogeochemistry of waters from borehole through the continental terminal, basement rock, and Korama formations in the Zinder region. To reach this objective, thirteen (13) boreholes were chosen and fifty two (52) samples were collected and analyzed over a year. The Water Quality Index (WQI) was calculated to determine the water types and their potential uses. The hydrochemical characteristics of the water were established based on the Schöeller-Berkaloff model. The Water Quality Index (WQI) showed generally good water quality. However, 23.1% of the water sources are unsuitable for drinking due to nitrate ion concentration exceeding WHO’s standards. The water showed two major facies: a bicarbonate facies in 84.6% of the boreholes with calcium and sodium potassium poles and a chloride facies observed in 15.4% of the boreholes with a calcium pole. The mineralization of this water could be attributed to the surrounding rock, the transfer of water originating either from the Korama aquifer (due to its high permeability and low water level) or from the bedrock (due to its fault), and anthropogenic inputs. In order to globally understand the hydrogeochemistry of these waters, there is an need to support this study by the monitoring of certain isotopic signatures to better discriminate the water transfer as well as the mineralization. Copyright@ International Science Community Association