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This focus article presents the state of the West African rainforest (WARF), its role in atmospheric moisture transport to the Nile Basin, and the potential impact of its deforestation on the Nile Basin's water regime, as well as options for improving transboundary water governance. The Nile is the longest river in the world, but delivers less water per unit area than other major rivers. Pressures from the Basin's rapidly growing population and agricultural demand risk exacerbating transboundary water conflicts. About 85% of the surface water reaching Aswan in Egypt originates from the Ethiopian Highlands which comprise less than 10% of the Nile Basin's total area (3.3 million km(2)). Some of the atmospheric moisture reaching the Highlands crosses over the WARF; other moisture source areas include the Mediterranean Sea, the Indian Ocean, and the Atlantic Ocean. The WARF adds atmospheric moisture and modifies the regional climate system. Deforestation in the WARF has the potential to alter rainfall patterns over the Ethiopian Highlands and thus flows in the Nile River, with reductions a likely outcome. Transregional governance that looks beyond basin boundaries to the sources and routes of moisture transport (the precipitationshed) has yet to be integrated into land-atmosphere and water management negotiations. To better achieve sustainable land management and water resource development in the Nile Basin, scientific and governance frameworks need to be established that include the WARF region states in the ongoing negotiations between the Nile riparian states. This article is categorized under: Engineering Water > Planning Water Human Water > Water Governance Science of Water > Methods