評論
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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.
匱乏也好，充沛也罷，最重要的一點是水具有地方性的特點。水很重——一立方的水重達一公噸——成本太高而難以移動。地表水——主要儲存于江河、湖泊和水庫內——如果沒有人工的疏導，不會由一個盆地自動流往另一個盆地，一般只能使用抽水機抽取。在一個盆地之內，河流上游的水也許可以用于灌溉、工業以及家庭活動。不過，當它們快要流入大海時，這種能利用的機會就會減少，在那里除了維持出?？诘娜侵藓蜐竦?，以及將沉積在河口的泥沙沖出大海之外,就沒有其他用途了。
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.
這些情況不容忽視。如果江河水不流動，里面的生物就不可能生存。目前，一個世紀之前世界上的淡水魚類中超過五分之一瀕臨滅絕或已經滅絕。在過去的200年間，世界上的濕地有一半也已經消失。然而，現在的問題是，即便在同一個盆地內，水的價值在一些地方也會比其他地方的價值要大。
