A river basin, also known as a drainage or catchment area, encompasses the area drained by one river and all its tributaries. The map shows the main river basins of the world. Smaller basins are included as regional clusters.

The volume and quality of water available are important factors for agriculture, rural development and livelihoods. A water scarcity ratio can show where geographic areas and populations are at risk from low water security. It is calculated by comparing total water withdrawals (domestic, industrial, and agricultural) with the total renewable water resources. A river basin suffers from extremely high water stress if the ratio of withdrawals to renewable water resources is above 80 percent.

Agriculture, sewage plants, decaying plant material, and runoff from urban areas and industries can lead to damaging levels of nitrogen (N) and phosphorus (P) in a river, threatening human and ecosystem health. The N-index and P-index maps show which basins are most affected from water pollution.

The river basin boundaries presented here are used in the IMPACT model (Rosegrant, 2012), and were delineated based on HydroSHEDs and Hydro1K, with a few basins updated based on the basin boundaries made available by the CGIAR Challenge Program on Water and Food.

For more information:IFPRI Water Policy program