Volcanic highlands supply water to 40% of the world’s population. Soil degradation threatens this water supply. Studies on geohydrology that affect the effectiveness of land and water management (LWM) practices in reducing soil degradations are limited. To aid in the effectiveness of LWM practices, we conducted a field experiment in the Gomit watershed in the semihumid Ethiopian Highlands on the interaction of hydrogeology and LWM practices. We found that in a watershed with strongly faulted tertiary basalt, 30% of the rainfall was drained through faults to another basin. Consequently, the discharge at the outlet was less than half of that of other watersheds with quaternary basalts. Despite the high sediment concentration, i.e., around 15 g L−1, in the Gomit watershed, the sediment yield of less than 4 Mg ha−1 a−1 was below average for the agricultural watershed in Ethiopia because of the low runoff response. While some faults facilitated drainage, others acted as a barrier. Groundwater stored behind the barriers was used as a municipal potable water source. Since the effectiveness of LWM practices depends on the amount of erosion that can be prevented, considerations of country-wide prioritizing of investments in land and water management practices should include the geology of the watersheds.

中文翻译：

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火山高地的水文地质影响土地管理实践的优先次序

火山高地为世界 40% 的人口供水。土壤退化威胁着这种供水。影响土地和水资源管理 (LWM) 实践在减少土壤退化方面的有效性的地质水文学研究是有限的。为了提高 LWM 实践的有效性，我们在半湿润的埃塞俄比亚高地的 Gomit 流域进行了一项关于水文地质学和 LWM 实践相互作用的现场试验。我们发现，在具有强烈断层第三玄武岩的流域中，30% 的降雨通过断层排到另一个盆地。因此，出口处的流量不到其他四系玄武岩流域的一半。尽管 Gomit 流域的沉积物浓度很高，即大约 15 g L−1，由于低径流响应，埃塞俄比亚农业流域的沉积物产量低于 4 Mg ha-1 a-1 低于平均值。虽然一些断层促进了排水，但其他断层起到了屏障的作用。储存在屏障后面的地下水被用作市政饮用水源。由于 LWM 实践的有效性取决于可以预防的侵蚀量，在全国范围内优先考虑对土地和水资源管理实践的投资应包括流域的地质。