There is escalating salinity levels on small islands due to uncontrolled groundwater extraction. Conventionally, this challenge is addressed by adopting optimal groundwater pumping strategies. Currently, on Unguja Island (Zanzibar), urban freshwater is supplied by desalination, which is expensive and energy-intensive. Hence, desalinization cannot be afforded by rural communities. This study demonstrates that the innovative Kilimanjaro Concept (KC), based on rainwater harvesting (RWH) can remediate seawater intrusion in Unguja, while enabling a universal safe drinking water supply. The reasoning is rooted in the water balance of the whole island. It is shown that if rainwater is systematically harvested, quantitatively stored, and partly infiltrated, seawater intrusion will be reversed, and a universal safe drinking water supply will be secured. Water treatment with affordable technologies (e.g., filtration and adsorption) is suggested. The universality of KC and its suitability for small islands is demonstrated. Future research should focus on pilot testing of this concept on Unguja Island and other island nations.

中文翻译：

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乞力马扎罗山概念在坦桑尼亚桑给巴尔扭转海水入侵和保障供水中的应用

由于不受控制的地下水开采，小岛上的盐度不断上升。通常，通过采用最佳地下水抽取策略来解决这一挑战。目前，在安古贾岛（桑给巴尔岛），城市淡水是通过海水淡化提供的，这种方法既昂贵又耗能。因此，农村社区无法承受海水淡化。这项研究表明，基于雨水收集 (RWH) 的创新乞力马扎罗山概念 (KC) 可以修复安古贾的海水入侵，同时实现普遍安全的饮用水供应。其推理植根于整个岛屿的水平衡。研究表明，如果雨水被系统地收集、定量储存和部分渗透，海水入侵将被逆转，将确保普遍安全的饮用水供应。建议使用负担得起的技术（例如过滤和吸附）进行水处理。证明了 KC 的普遍性及其对小岛屿的适用性。未来的研究应侧重于在安古贾岛和其他岛国对这一概念进行试点测试。