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SAVING WATER
/ WATER FOR FOOD
source: www.unesco.org/water/
wwap/wwdr/pdf/chap8.pdf
www.ec.gc.ca/water/en/
e_quickfacts.htm
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Each day humans must replace 2.4 litres of water, some through drinking and the rest taken by the body from the foods eaten… - food and agriculture are by far the largest consumers of water. They require perhaps 1 hundred times more than we use to meet basic personal needs, with up to 70% of the water we take from rivers and groundwater going into irrigation;
- global food production has kept pace with population growth in recent decades; yet nearly 800 million people remain undernourished, and the population shift from rural to urban environments will certainly increase the pressures and problems associated with food security. A growing population will need more food and thus more water;
- the Food and Agriculture Organization (FAO) anticipates a net expansion of irrigated land of some 45 million hectares in ninety-three developing countries (to a total of 242 million hectares in 2030) and projects that agricultural water withdrawals will increase by some 14% from 2000 to 2030 to meet future food production needs. The analysis indicates a projected annual growth rate of 0.6%, compared with the 1.9% observed in the period from 1963 to 1999;
- using a hydrologic perspective, trade in food was called trade in ‘virtual water’ that is the water consumed to produce an agricultural commodity. For example, a crop such as wheat consumes about 1 to 5 m3 of water (a cubic metre is equivalent to 1,000 litres) to produce 1 kg of cereal. Another example: approximately 1,000 litres of water are required to grow 1 Kg of potatoes;
- the production of meat requires between 6 and 20 times more water than for cereals, depending on the feed/meat conversion factor. For poultry, the virtual water content would be 6 m3/kg of poultry meat. For cattle, the virtual water content of 1 kg of beef would be 15m3;
Product Unit Equivalent water in m3 per unit| product | unit | m3/litres | | cattle | head | 4,000 | | sheep and goats | head | 500 | | fresh beef | kg | 15 | | fresh lamb | kg | 10 | | fresh poultry | kg | 6 | | cereals | kg | 1.5 | | citrus fruits | kg | 1 | | palm oil | kg | 2 | | pulses, roots and tubers | kg | 1 |
Source: FAO, 1997
A rough calculation of global water needs for food production can be based on the specific water requirements to produce food for one person… - depending on the composition of meals and allowing for post-harvest losses, the present average food ingest of 2,800 kcal/person/day may require roughly 1,000 m3 per year to be produced. With a world population of 6 billion, water needed to produce the necessary food is 6,000 km3 (excluding any conveyance losses associated with irrigation systems);
- most water used by agriculture stems from rainfall stored in the soil profile and only about 15% of water for crops is provided through irrigation. Irrigation therefore needs 900 km3 of water per year for food crops (to which some water must be added for non-food crops). On average, about 40% of water withdrawn from rivers, lakes and aquifers for agriculture effectively contribute to crop production, the remainder being lost to evaporation, deep infiltration or the growth of weeds. Consequently, the current global water withdrawals for irrigation are estimated to be about 2,000 to 2,500 km3 per year.
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