Non-conventional water resources and opportunities for water augmentation to achieve food security in water scarce countries

摘要

Given current demographic trends and future growth projections, as much as 60% of the global population may suffer water scarcity by the year 2025. The water-use efficiency techniques used with conventional resources have been improved. However, water-scarce countries will have to rely more on the use of non-conventional water resources to partly alleviate water scarcity. Non-conventional water resources are either generated as a product of specialized processes such as desalination or need suitable pre-use treatment and/or appropriate soil-water-crop management strategies when used for irrigation. In water-scarce environments, such water resources are accessed through the desalination of seawater and highly brackish groundwater, the harvesting of rainwater, and the use of marginal-quality water resources for irrigation. The marginal-quality waters used for irrigation consist of wastewater, agricultural drainage water, and groundwater containing different types of salts. In many developing countries, a major part of the wastewater generated by domestic, commercial, and industrial sectors is used for crop production in an untreated or partly treated form. The protection of public health and the environment are the main concerns associated with uncontrolled wastewater irrigation. The use of saline and/or sodic drainage water and groundwater for agriculture is expected to increase. This warrants modifications in the existing soil, irrigation, and crop management practices used, in order to cope with the increases in salinity and sodicity that will occur. It is evident that water-scarce countries are not able to meet their food requirements using the conventional and non-conventional water resources available within their boundaries. Another option that may help to achieve food security in these countries is the 'physical' transportation of water and food items across basins, countries, and regions. Long-distance movement of surface freshwater or groundwater and transporting the water inland via large pipelines or across the sea in extremely large bags are examples of 'physical' transportation. Most interregional water transportation projects are still in their infancy, though the trade of food items between countries has been going on since international trade began. Although food is imported in the international food trade, the water used to produce the food that is imported into water-scarce countries is equivalent to large water savings for those countries: without the imports, almost the same amount of water would be needed to produce that food domestically. The term 'virtual water' has been used to illustrate the important role that water plays in the trade in food between countries with a water surplus and those with a water deficit, which must rely in part on importing food to ensure food security. Because the major food-exporting countries subsidize their agricultural production systems, food-importing countries need to consider both the policies and political situations of food-exporting countries, while simultaneously using food trade as a strategic instrument to overcome water scarcity and food deficits. This paper reviews the literature and issues associated with the use of non-conventional water resources and opportunities for achieving food security in water-scarce countries.