Water constraints and environmental impacts of agricultural growth

Water, the environment, and food production are closely interrelated at the local, regional and global levels. With rapidly increasing water demands, the competition among household, industrial, environmental, and agricultural water uses has been escalating in many regions. Although the achievements of irrigation in ensuring food security and improving rural welfare have been impressive, past experiences also indicate problems and failures of irrigated agriculture, often related to environmental issues including groundwater overdraft, water quality reduction, waterlogging, and salinization. Hydrological records over a long period have shown a marked reduction in the annual discharge on some of the world's major rivers (OECD), due in significant part to growth in agricultural water consumption. These developments raise the question of whether water scarcity will constrain food production growth, particularly in the developing world. This paper assesses the impact of water supply on future food production growth, and the tradeoffs between increased allocation of water to environmental purposes, the elimination of groundwater overdraft, and food production. The analysis uses an integrated global water and food model and employs alternative scenario assessments to examine the degree to which water will constrain future food production, and the implications of competition for water between agriculture and the environment.