"... relatively few people are aware of how nineteenth- and twentieth-century patterns impacted the mountain rivers of the . When I moved to Colorado in 1989, I was impressed by the sparkling water of the mountain rivers, and I too assumed that these were natural, fully functional rivers. It was only after I began to read historical accounts of the Colorado and to examine the streams more closely that I realized how dramatically they had been altered. I began to think of them as virtual rivers, which had the appearance of natural rivers but had lost much of a natural river's ecosystem functions."