Further Readings
You will find bibliographies linked from the individual project galleries. Some introductory recommendations include:

Edward Abbey
The Brave Cowboy; An Old Tale In A New Time. New York: Dodd, Mead, 1956.
Desert Solitaire: A Season in the Wilderness. New York: McGraw-Hill, 1968.
The Monkey Wrench Gang. Philadelphia: Lippincott, 1975. 

Katie Lee
All My Rivers Are Gone: A Journey of Discovery Through Glen Canyon. Boulder, CO: Johnson Books, 1998.

John McPhee
Encounters with the Archdruid. New York: Farrar, Strauss, and Giroux, 1971.

Marc Reisner
Cadillac Desert: The American West and Its Disappearing Water. New York: Viking, 1986.

William DeBuys
Seeing Things Whole: The Essential John Wesley Powell. Island Press, 2004.

John Wesley Powell
The Exploration of the Colorado River and Its Canyons. Penguin, 2003.

Rebecca Solnit
Wanderlust (2000). New York: Viking Pess.