The world population is expected to increase to more than 9 billion by 2050 (FAO, 2011). Demand for food and fiber will also increase as incomes and standards of nutrition rise and as people consume more land- and water-intensive diets (i.e., consumption of more meat and dairy products). Current estimates suggest that by 2050 annual cereal production will rise to about three billion tonnes and meat production to more than 200 million tonnes (FAO, 2006). To produce this amount of food, irrigated land must increase by 35%, and 20% more water must be diverted to agriculture. However, due to increasing inter-sectoral competition for water and decreasing investment in irrigation development, expansion of irrigated lands will be no more than 5%, and water diversions for irrigation are projected to decrease by 8% because of climate change and other management issues. Thus in the future irrigation's con-tribution to food security will have to come from improving existing systems and increasing the productivity of available water resources. Under the "business as usual" scenario (i.e., continuing with the current agricultural practices and water productivity levels), 4500 km 3 yr-1 more water will be needed to feed the world's population by 2050 (Falkenmark et al., 2009). This is roughly twice the amount of water presently used in irriga-tion (Kijne et al., 2009).
