The Niger River Basin is a transboundary basin covering nine riparian countries to the Niger River that are increasingly putting pressure on the available water resources as their populations expand. Yet, the nine countries are also among the poorest in the world and adequate exploitation of the water of the basin could be part of a broader strategy for poverty reduction in these countries. Major challenges to that end are the lacking water infrastructure and growing vulnerability to extreme weather hazards as the climate changes. In that context, a better understanding of the state of water resources in the basin is a crucial departure point for any measures towards the sustainable use of water. The Water Accounting Plus (WA+) system designed by IHE Delft with its partners FAO and IWMI has been applied to gain full insights into the state of the water resources in the basin.