Water and Agriculture
Water is the key to food security.
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According to OECD, water demand is projected to increase by 55% globally between 2000 and 2050. The increase in demand will come mainly from manufacturing (+400%), electricity (+140%) and domestic use (+130%). In the face of these competing demands, there will be little scope for increasing water for irrigation.
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Agriculture accounts for 70% of total water withdrawals for all (including energy) sectors/human uses, and 90% of all water consumed by these sectors. Relatively speaking, withdrawals for agriculture tend to decrease with increasing levels of development. In many countries, water availability for agriculture is already limited and uncertain, and this is set to worsen.
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Only about 20% of agriculture’s annual water consumption is water from rivers, streams, lakes, and groundwater for irrigation purposes – the rest is from rainfed agriculture.
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Irrigation crop yields are about 2.7 times those of rainfed farming. Therefore, while irrigation covers less than 20% of the world’s cultivated area, it accounts for more than 40% of the world’s agricultural production (FAO, 2011).
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Globally, the area equipped for irrigation increased from 170 million ha in 1970 to 304 million ha in 2008, and there is still potential for expansion, particularly in sub-Saharan Africa and Southern America, provided there is sufficient water available.
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The world population is predicted to grow from 6.9 billion in 2010 to 8.3 billion in 2030 and 9.1 billion in 2050 (UNDESA, 2009). Food demand is predicted to increase by 50% in 2030 and by 70% in 2050 (Bruinsma, 2009).
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Predicting future water demand for agricultural uses is fraught with uncertainty, as it is influenced by population and income levels, the type of food in demand, and quantities consumed. Crop types, yields, and efficiency of agricultural production also affect the quantities of water required, while climatic variations add to the uncertainties.
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The most recent estimates of future global agricultural water withdrawal for irrigated agriculture is an increase of around 5% by 2050, from 2,743 km3 in 2008 to 3,858 km3 in 2050 (FAO, 2011). Much of the increase in irrigation water consumption will be in regions already suffering from water scarcity.