Total renewable surface water in Nigeria 2020, by source

The release date is the date of access.

The source notes that total renewable surface water is the sum of the internal renewable surface water resources and the total external renewable surface water resources.
Surface water refers to all waters on earth's surface found in streams, rivers, lakes, marshes or wetlands, and ice and snow.

Internal renewable surface water resources refer to long-term average annual volume of surface water generated by direct runoff from endogenous precipitation (surface runoff) and groundwater contributions.
External renewable surface water resources refer to the sum of the actual inflow not submitted to treaties, actual inflow secured through treaties, the accounted flow of border rivers and the accounted part of shared lakes, minus the outflow reserved for downstream countries through treaties.