The river we now know as the Colorado was once called the Grand. Said by John Wesley Powell, head of the U. S. Geological Survey a century ago, to "have its source five or six miles west of Long's Peak," from there it meanders down a glacial valley and into Grand Lake. It runs with few impediments in Colorado. Every river west of the Continental Divide that heads within the state eventually merges with the Colorado River.
Downstream from Lake Granby the Colorado picks up the flows from Willow Creek, the Fraser River, the Williams Fork, Muddy Creek, and the Blue, Eagle, Roaring Fork, and Fryingpan rivers. The Colorado and its tributary streams give Colorado anglers some impressive fisheries.
The Colorado is home to brown trout, Colorado River cutthroats, and rainbow trout. It also holds Colorado River rainbows, a fish that evolved in the river. Hybrid cuttbows swim in its waters. From its headwaters downstream to the Rifle area the Colorado is an outstanding trout stream.