2012届高三英语二轮复习话题训练（8份） 话题七：生态环保类 (一) (2010•安徽
高考) the need to feed a growing population is putting much pressure on the world's supply of water. with 97% of the world's water too salty to be drunk or used in agriculture, the worldwide supply of water needs careful management, especially in agriculture. although the idea of a water shortage(短缺)seems strange to someone fortunate enough to live in a high rainfall country, many of the world's agricultural industries experience constant water shortages. although dams can be built to store water for agricultural use in dry areas and dry seasons, the costs of water redistribution(重新分配)are very high. not only is there the cost of the engineering itself, but there is also an environmental cost to be considered. where valleys(山谷)are flooded to create dams, houses are lost and wildlife homes destroyed. besides, water may flow easily through pipes to fields, but it cannot be transported from one side of the world to the other. each country must therefore rely on the management of its own water to supply its farming requirements.
