The 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 evaporation. Groundwater from Kuzikus/Ebenhaezer shows an evaporation effect, probably evaporation occurs during infiltration since it is observed in all sampling seasons. All groundwater from three sites plot in the same area with rainwater depleted in stable isotopic values, which could indicates that recharge only take place during January, February and March. CMB method revealed that Waterberg has the highest recharge rate ranging between 39.1 mm/a and 51.1 mm/a (8.7% – 11.4% of annual precipitation), Tsumeb with rates ranging from 21.1 mm/a to 48.5 mm/a (3.5% – 8.1% of annual precipitation), and lastly Kuzikus/Ebenhaezer from 3.2 mm/a to 17.5 mm/a (1.4% – 7.3% of annual precipitation). High recharge rates in Waterberg could be related to fast infiltration and absence of evaporation as indicated by the isotopic ratios. Differences in recharge rates cannot only be attributed to the precipitation gradient but also to the evaporation rates and the presence of preferential flow paths. Recharge rates estimated for these three sites can be used in managing the savannah aquifers especially at Kuzikus/Ebenhaezer where evaporation effect is observed that one can consider rain harvesting.

地下水资源的量化至关重要，尤其是在纳米比亚等缺水国家。使用氯离子质量平衡（CMB）方法和同位素组成确定沿三个地点的降水梯度的地下水补给量：Tsumeb（600 mm / a降水）；Waterberg（450毫米/年的降水量）和Kuzikus / Ebenhaezer（240毫米/年的降水量）。2016-2017年收集了地下水和雨水。每月收集雨水，而在雨季之前，期间和之后收集地下水。对于δ雨水同位素值¹⁸ O和δ ² ħ范围从-10.70 6.10‰，从-72.7至42.1‰分别。对于δ地下水同位素值¹⁸Tsumeb的O范围为-9.84至-5.35‰; 从-10.85至-8.60‰为瓦特和从-8.24到-1.56‰为Kuzikus / Ebenhaezer，而对于δ ²Tsumeb的H范围为-65.6至-46.7‰; 沃特贝格为-69.4至-61.2‰，库兹库斯/埃本海泽尔为-54.2至-22.7‰。雨水沿GMWL扩散。与11月，12月，4月和5月相比，1月，2月和3月收集的雨水中的重同位素更加贫乏。GMWL上的Waterberg地下水图表明没有蒸发。Tsumeb地下水位于GMWL上/附近，除了喀斯特湖Otjikoto的地下水正在蒸发外。Kuzikus / Ebenhaezer的地下水表现出蒸发作用，因为在所有采样季节都可以观察到，因此渗透过程中可能发生了蒸发。来自三个地点的所有地下水都分布在同一区域，且雨水以稳定的同位素值消耗，这可能表明补给仅发生在1月，2月和3月。CMB方法显示，沃特伯格的补给率最高，介于39.1 mm / a和51.1 mm / a之间（占年降水量的8.7％– 11.4％），Tsumeb的补给率介于21.1 mm / a至48.5 mm / a（3.5％–年降水量的8.1％），最后Kuzikus / Ebenhaezer从3.2 mm / a到17.5 mm / a（1.4％– 7.3％的年降水量）。沃特伯格的高补给率可能与同位素渗透率表明的快速渗透和蒸发的缺乏有关。补给率的差异不仅可以归因于降水梯度，还可以归因于蒸发率和优先流动路径的存在。估计这三个位置的补给率可用于管理大草原含水层，特别是在Kuzikus / Ebenhaezer，那里的蒸发作用很明显，可以考虑降雨。