Green and blue water accounting in the Ganges and Nile basins: Implications for food and agricultural policy

Most food globally is produced from soil moisture that comes exclusively from precipitation, or green water. Moreover, most of the water reaching plants in irrigated systems also stems from precipitation. Despite this, irrigation or blue water has typically been the focus for policy analysis in the past, given the possibility for human manipulation of these resources. This paper analyzes alternative water futures using a combined green and blue water accounting framework embedded within the water simulation components of IFPRI's International Model for Policy Analysis of Agricultural Commodities and Trade (IMPACT). Recently developed future scenarios for the International Assessment of Agricultural Knowledge, Science and Technology for Development (IAASTD) and other work are assessed with this adjusted green/blue water accounting framework. Accounting explicitly for green water resources broadens the scope of options for decision-makers trying to improve agricultural production in the face of rising food and energy prices and a degrading water and land resource base in the face of increasing demands. Results highlight the importance of green/blue water accounting presenting a wider range of agricultural science and technology policy options for increasing global crop productivity across a span of potential futures. (C) 2009 Elsevier B.V. All rights reserved.