Estimation of groundwater recharge in savannah aquifers along a precipitation gradient using chloride mass balance method and environmental isotopes, Namibia

Publication date: Available online 2 February 2020Source: Physics and Chemistry of the Earth, Parts A/B/CAuthor(s): S. Uugulu, H. W.eAbstractThe quantification of groundwater resources is essential especially in water scarce countries like Namibia. The chloride mass balance (CMB) method and isotopic composition were used in determining groundwater recharge along a precipitation gradient at three sites, namely: Tsumeb (600 mm/a precipitation); Waterberg (450 mm/a precipitation) and Kuzikus/Ebenhaezer (240 mm/a precipitation). Groundwater and rainwater were collected from year 2016–2017. Rainwater was collected monthly while groundwater was collected before, during and after rainy seasons. Rainwater isotopic values for δ18O and δ2H range from −10.70 to 6.10 and from −72.7 to 42.1 respectively. Groundwater isotopic values for δ18O range from −9.84 to −5.35 for Tsumeb; from −10.85 to −8.60 for Waterberg and from −8.24 to −1.56 for Kuzikus/Ebenhaezer, while that for δ2H range from −65.6 to −46.7 for Tsumeb; −69.4 to −61.2 for Waterberg and −54.2 to −22.7 for Kuzikus/Ebenhaezer. Rainwater scatters along the GMWL. Rainwater collected in January, February and March are more depleted in heavy isotopes than those in November, December, April and May. Waterberg groundwater plots on the GMWL which indicates absence of evaporation. Tsumeb groundwater plots on/close to the GMWL with an exception of groundwater from the karst Lake Otjikoto which is showing ...
Source: Physics and Chemistry of the Earth, Parts ABC - Category: Science Source Type: research