To alter the gradient of land surface for decreasing the energyofflow.
二是改变地表的坡度，减小水流的能量。
2
There is no question that the United States imports a great deal ofenergy and, in fact, relies on that steady flow to maintain its economy.
毫无疑问，美国进口了大量的能源。而事实上，美国依靠这种稳定的流动来其维持经济。
3
Unfortunately this early plant experienced the problem common to many forms of renewable energy: the flow in the Wey River was unreliable, and the waterwheel was soon replaced by a steam engine.