title: Hydrogeochemical and isotope study of perched aquifers in the Cuvelai-Etosha Basin, Namibia.
abstract: A hydrogeochemical and stable isotope study (2H and18O) was carried out in the Cuvelai-Etosha Basin in order to characterize available groundwater and to identify possible recharge mechanisms for the perched aquifers. Data were collected during seven field campaigns between 2013 and 2015 from a total of 24 shallow and deep groundwater hand-dug wells. In the investigated groundwaters, hydrogencarbonate is the dominating anion in both well types, whereas cations vary between calcium and magnesium in deep wells, and sodium and potassium in shallow wells. Groundwater chemistry is controlled by dissolution of carbonate minerals, silicate weathering and ion exchange. Stable isotopic composition suggests that deep groundwater is recharged by high-intensity/large rainfall events, whereas the shallow wells can even be recharged by less-intense/small rainfall events. Water in deep wells reflect a mixture of water influenced by evaporation during or before infiltration and water that infiltrated through fast preferential pathways, whereas shallow wells are strongly influenced by evaporation. The findings of this research contribute to improve the understanding of hydrogeochemistry, recharge paths and temporal variations of perched aquifers.
authors.affiliation: a Geology Department , University of Namibia , Windhoek , Namibia.
authors.forename: Josefina T
authors.initials: JT
authors.lastname: Hamutoko
authors.affiliation: a Geology Department , University of Namibia , Windhoek , Namibia.
authors.forename: Heike
authors.initials: H
authors.lastname: Wanke
authors.affiliation: b Federal Institute for Geosciences and Natural Resources (BGR) , Hanover , Germany.
authors.forename: Paul
authors.initials: P
authors.lastname: Koeniger
authors.affiliation: b Federal Institute for Geosciences and Natural Resources (BGR) , Hanover , Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Beyer
authors.affiliation: b Federal Institute for Geosciences and Natural Resources (BGR) , Hanover , Germany.
authors.forename: Marcel
authors.initials: M
authors.lastname: Gaj
mesh_terms: D001639:Bicarbonates / Q000032:analysis*; D002118:Calcium / Q000032:analysis; D003903:Deuterium / Q000032:analysis*; D004784:Environmental Monitoring / Q000379:methods*; D060587:Groundwater / Q000737:chemistry*; D062070:Hydrology; D008274:Magnesium / Q000032:analysis; D009276:Namibia; D010103:Oxygen Isotopes / Q000032:analysis*; D011188:Potassium / Q000032:analysis; D012964:Sodium / Q000032:analysis; D062066:Water Resources
chemical_list: D001639:Bicarbonates; D010103:Oxygen Isotopes; D012964:Sodium; D003903:Deuterium; D008274:Magnesium; D011188:Potassium; D002118:Calcium
keywords: Cuvelai-Etosha Basin; Namibia; groundwater; hydrogen-2; hydrogeochemistry; isotope hydrology; oxygen-18; perched aquifer