Abstract
Abstract. The rural population in parts of the Cuvelai-Etosha Basin (CEB) in Namibia depends on groundwater as a source for drinking and livestock watering. The aim of this study is to investigate spatial-temporal patterns for understanding water origins and recharge processes of perched aquifers in the CEB. The study uses hydrochemical data and water stable isotope signatures (18O and 2H) of samples collected during (10) ten field campaigns over a three-year period (from 2014 to 2016) originating from two regions within the basin (Ohangwena and Omusati). A clear distinction between the shallow groundwater in the Omusati and Ohangwena regions documented by TDS values, hydrochemical water types as well as the isotopic compositions of water. These differences are influenced mainly by their location in the landscape, depth to water table, the type of well infrastructure and aquifer material. Spatial and temporal variations indicate that even though these perched aquifers are both within the same basin, they are chemically different because of the rock materials in which their flow. Therefore, these differences in the water hydrochemical composition as well as the processes governing perched aquifers must be taken into account when planning groundwater management in the basin.
Highlights
More than half of the rural communities in the Namibian part of the Cuvelai-Etosha Basin (CEB) depend on groundwater as a main source of domestic water supply
Different spatial and temporal scales are important for arid environments due to the high heterogeneity associated with these environments
High total dissolved solids (TDS) values are observed in Omusati compared to the Ohangwena region (Fig. 2)
Summary
More than half of the rural communities in the Namibian part of the Cuvelai-Etosha Basin (CEB) depend on groundwater as a main source of domestic water supply. The majority of people live in rural areas and are supplied by groundwater wells that tap both shallow and deep aquifers. The shallow groundwater which is trapped on both local, discontinuous impermeable layers (perched aquifers) and shallow regional aquifers is commonly tapped by traditional handdugs wells that are more affordable and cheap in comparison with deep boreholes. Different spatial and temporal scales are important for arid environments due to the high heterogeneity associated with these environments. Ledesma-Ruiz et al (2015) highlighted that spatial and temporal variability evaluation of major ions are commonly used in groundwater to give insight to aquifer’s heterogeneity and processes controlling the groundwater chemistry. Different spatial and temporal scales are important for arid environments due to the high heterogeneity associated with these environments. Ledesma-Ruiz et al (2015) highlighted that spatial and temporal variability evaluation of major ions are commonly used in groundwater to give insight to aquifer’s heterogeneity and processes controlling the groundwater chemistry. Wanke et al (2014) described water quality from hand dug wells of different areas in Namibia, and concluded that the water in hand-dug wells is not acceptable for drinking and domestic purposes mainly because of its high turbidity, total dissolved solids (TDS), fluoride and nitrate values. Hamutoko et al (2017) characterized the hydrochemical and Published by Copernicus Publications on behalf of the International Association of Hydrological Sciences
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