Actual crop water use in project countries : a synthesis at the regional level

This report aims to synthesize the results of a crop water use study conducted by country teams of the GEF/World Bank project, Regional Climate, Water, and Agriculture: Impacts on and Adaptation of Agro-ecological Systems in Africa. It also presents the results of the second phase of the study based on climate change scenarios, conducted by the South Africa country team. The actual evapotranspiration of five commonly grown crops-maize, millet, sorghum, groundnuts, and beans-in two selected districts were analyzed by six country teams. In addition, two country teams also analyzed other crops grown in the districts. The regional analysis shows that the actual yield of the different crops-specifically of maize and groundnuts-improves with an increase in actual evapotranspiration, although the gap remains wide between actual and potential yield and actual and maximum evapotranspiration, especially for the rainfed crops. This highlights the importance of improved water management if agriculture is to play an important role as a source of food security and better livelihoods. The report highlights the vulnerability of maize to water stress and the increased risks to the viability of rainfed farming systems based on this crop. The results of the second phase of analysis show that a 2°C increase in the temperature and a doubling of carbon dioxide concentration in the atmosphere will shorten the growing period of maize, which will result in decreased crop water requirement and use. The authors recommend extending this type of analysis to other crops as well as to other countries to developa clearer picture of the changing pattern in crop water use of the major crops grown in the project countries.