The Simien Mountains are important not just for biodiversity, but also as a water catchment area. Several rivers rise in SMNP and form tributaries to the Tekeze River, which provides a source of water for millions of users downstream in Ethiopia as well as Sudan and Egypt. Most rivers in this area flow only after the rainy season, therefore the rivers that rise in Simien and flow year-round are a particularly important water source.
If the flow of these rivers is altered in any way, for example through highland deforestation, overgrazing or abstraction for irrigation – all of which are occuring at present – a highland/lowland imbalance results with loss of perennial water in the lowlands. If such a situation arises, the dry season range of the people and their livestock reduces dramatically and they congregate around whatever water source remains. Rangeland degradation then occurs, with a shortage of fodder and soil erosion which can be both rapid and difficult if not impossible to reverse. Downstream users are likely to become increasingly food insecure and aid dependent if the water catchment areas of the Simien Mountains are insufficiently protected.