In the Greater Serengeti-Mara ecosystem, with the Serengeti National Park (SNP) at its core, people and wildlife are strongly dependent on water supply that has a strong seasonal and inter-annual variability. The Mara River, the only perennial river in SNP, and a number of small streams originate from outside SNP before flowing through it. In those watersheds increasing grazing pressure from livestock, deforestation, irrigation and other land uses affect river flows in SNP that subsequently have impacts on wildlife. We quantified the changes since the 1970s of river discharge dynamics. We found that the baseflow recession period for the Mbalageti River has remained unchanged at 70 days, which is a natural system inside SNP. By contrast it has decreased from 100 days in the 1970s to 16 days at present for the Mara River, coinciding with increased commercial-scale irrigation in Kenya that extract Mara River water before it reaches SNP. This irrigation will result in zero flow in the river in SNP if the proposed dams in the river in Kenya are built. We observed high flash floods and prolonged periods of zero flows in streams draining livestock grazed watersheds, where severe major erosion prevails that results in gully formation. This eroded sediment is expected to silt and dry out the scattered dry season water holes in SNP, which are an important source of drinkable water for wildlife during the dry season. It appears likely that the future water supply of SNP is at risk, and this has major consequences for its people and wildlife. Ecohydrology-based solutions at the catchment scale are urgently needed to reduce catchment degradation while ensuring sustainable water provision.

在大塞伦盖蒂-马拉生态系统中，以塞伦盖蒂国家公园（SNP）为核心，人和野生动植物严重依赖季节性和年际变化很大的供水。马拉河是SNP唯一的常年河流，许多小溪在流经SNP之前就从SNP外部流出。在这些流域中，牲畜，森林砍伐，灌溉和其他土地利用带来的放牧压力增加，影响了SNP中的河流流量，随后对野生生物产生了影响。我们量化了自1970年代以来河流排放动态的变化。我们发现，Mbalageti河的底流衰退期保持在70天不变，这是SNP内部的自然系统。相比之下，马拉河的时间从1970年代的100天减少到目前的16天，恰恰与肯尼亚商业规模灌溉的增加相吻合，后者在马拉河水到达SNP之前将其提取。如果在肯尼亚河中修建了拟建的水坝，这种灌溉将使SNP的河流零流量。我们观察到大量的山洪暴发和流向牲畜放牧流域的溪流长时间零流量，在那里严重的主要侵蚀盛行，导致形成沟壑。预计这些被侵蚀的沉积物会淤积并干燥SNP中分散的旱季水坑，这是旱季野生动植物饮用水的重要来源。SNP的未来水供应似乎处于危险之中，这对其人民和野生动植物造成重大影响。