Grand Canyon, it is one of the seven natural wonders of the world. Thousands of feet deep and miles wide it has been carved by the power of the Colorado River over millions of years. Forget everything you imagine about the natural state of this mighty river in Grand Canyon. Since the gates of Glen Canyon Dam were closed in 1963, the ecology of the Colorado River in Grand Canyon, has been altered; impacting bugs, fish, flow regimes, beaches and vegetation. Some fear there is no going back. (Produced by David Wallace and Michael Chow)