This is the wash cycle, where the rapid takes charge. Let's just say that the Colorado River has some very animated water in many places along the 278 mile length of it's Grand Canyon! All but one of the 23 named rapids from Phantom Ranch (RiverMile 88.3) to our pull out at RM 187.5 are caused by debris flows from side canyons and tributary streams. Before the dam, large floods tended to disperse boulders downstream making the area of the rapids a little less problematic for river runners. The Glen Canyon dam has significantly changed the character of the entire river ecosystem in other ways too. It traps silt and particulate debris in Lake Powell so the water runs relatively clear and because water is released from the middle depth of the lake, at 46 degrees, it is much colder than before. The flow of water ebbs and surges regularly over a 24 hour period like an ocean tide, it's flow rate (from 1,000 to 92,000 cfs = cubic feet per second) moderated by our voracious demand for water, doesn't come close to historical floods exceeding 240,000 to 300,000 cfs. For better or for worse, for the blink of an eye or for an eternity, in seen and unseen ways, the hand of man is now an integral part of this spectacular landscape.