In their upper reaches, mountain streams are full of energy. 上游地段的山涧充满活力

20. Such is the height of these falls
    具有如此这般高度的瀑布
21. that long before the water reaches the base in the Devil's Canyon
    在水还未落到恶魔谷底之前
22. it's blown away as a fine mist.
    便已被吹散成雾霾
23. In their upper reaches, mountain streams are full of energy.
    上游地段的山涧充满活力
24. Streams join to form rivers,
    溪流汇聚成河
25. building in power,
    随着力道的积聚
26. creating rapids.
    形成激流

来自《行星地球 第一季 第三集 Planet Earth S01E03 淡水》第 23 行