Green and blue water accounting in the Limpopo and Nile Basins

Implications for food and agricultural policy

Water scarcity is an increasingly critical issue for food production around the world. This is particularly true for the world’s poorest region, Sub-Saharan Africa, due to its growing malnutrition and almost complete dependence on rainfed agriculture. Given that agriculture is the primary consumer of freshwater around the globe and the demand for domestic, industrial, and environmental water uses is steadily rising, strategies for the sustainable use of water in agriculture are urgently required.

Globally, most of the water used for food production is derived from precipitation or “green” water, and most of the water that reaches plants in irrigated systems also stems from precipitation. Irrigation water only dominates in dry seasons or in systems located in arid areas. At the same time, many production systems classified as rainfed involve small-scale applications of supplemental water intended to alleviate plant stress at critical stages of production (for example, via rainwater harvesting schemes). Thus, water applications for crop production follow a continuum, from purely rainfed to purely irrigated, but the majority of crops are produced from rainwater.

This brief is based on a paper that analyzes the changing contribution of both green and blue water for food production under various scenarios in the Limpopo and Nile river basins in Africa in order to inform the development of appropriate policy and investment responses.

Author: 
Sulser, Timothy B.
Ringler, Claudia
Zhu, Tingju
Msangi, Siwa
Bryan, Elizabeth
Rosegrant, Mark W.
Published date: 
2011
Publisher: 
International Food Policy Research Institute (IFPRI)
Series number: 
15-18
PDF file: 
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rb15_18.pdf(156.9KB)