WASTEWATER, FOOD SECURITY AND PRODUCTION
Agriculture is the single largest user of water. This sector uses an estimated 70 per cent of total global fresh water (Appelgren, 2004; Pimentel and Pimentel, 2008), returning the ma- jority of this water back to the system. Where agriculture takes place in upper catchments, it may be the first cause of contamination in the water basin. However, agriculture also takes place downstream, where the water may already be polluted by other human activities that result in domestic and industrial waste. Hence there is a complex relationship between water quality, agriculture and food quality, which is in turn linked to human and ecological health.
Impact of food production practices on water quality Deterioration of water quality caused by agricultural practices can be addressed by optimizing water use, irrigation practices, crop selection and reducing evaporation, as well as cutting the application of nitrogen and phosphorus fertilizer, and pesticides. It is also necessary to consider the opportunities and threats posed by the reuse of wastewater in achieving these goals.
Irrigation has enabled crop yield to increase by up to 400 per- cent (FAO, 1996) and is one of the practices that has enabled production to keep up with the increased food demands of a growing population, increasing yield by 2.5 times (Kindall and
Pimentel, 1994). The daily drinking water requirement per person is 2–4 litres, but it takes 2 000 to 5 000 litres of wa- ter to produce one person’s daily food (FAO, 2007). Water re- quirements to produce different food stuffs vary hugely (Fig- ure 10). Increased livestock production and associated meat processing consumes large quantities of water and produces significant amounts of contaminated wastewater. Hence, re- ducing meat production will also affect water availability in many regions.
Water originating from the snow and ice in the Kush Hima- layas and Tibetan Plateau currently sustains over 55 percent
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