评论
打印
Scarce or plentiful, water is above all local. It is heavy—one cubic water weighs a tonne—, so expensive to move. Surface water—mostly rivers, lakes and reservoirs—will not flow from one basin into another without artificial diversion, and usually only with pumping. Within a basin, the water upstream may be useful for irrigation, industrial or domesticuse. As it nears the sea, though, the opportunities diminish to the point where it has no uses except to sustain deltas, wetlands and to carry silt out to sea.
匮乏也好，充沛也罢，最重要的一点是水具有地方性的特点。水很重——一立方的水重达一公吨——成本太高而难以移动。地表水——主要储存于江河、湖泊和水库内——如果没有人工的疏导，不会由一个盆地自动流往另一个盆地，一般只能使用抽水机抽取。在一个盆地之内，河流上游的水也许可以用于灌溉、工业以及家庭活动。不过，当它们快要流入大海时，这种能利用的机会就会减少，在那里除了维持出海口的三角洲和湿地，以及将沉积在河口的泥沙冲出大海之外,就没有其他用途了。
These should not be overlooked. If rivers do not flow, nothing can live in them. Over afifth of the world's freshwater fish species of a century ago are now endangered or extinct. Half the world's wetlands have also disappeared over the past 200 years. The point is, though, that even within a basin water is more valuable in some places than in others.
这些情况不容忽视。如果江河水不流动，里面的生物就不可能生存。目前，一个世纪之前世界上的淡水鱼类中超过五分之一濒临灭绝或已经灭绝。在过去的200年间，世界上的湿地有一半也已经消失。然而，现在的问题是，即便在同一个盆地内，水的价值在一些地方也会比其他地方的价值要大。
