One of the hot topics in environmental science is whether or not to remove dams to restore the natural flow of rivers. Over the centuries, thousands of dams have been constructed on rivers across the United States to store water or produce electricity. Some of these dams influence our national parks. One example is Glen Canyon Dam on the Colorado River in northern Arizona. This dam is 710 feet tall and was completed in 1963 to produce electrical power. It created the Lake Powell reservoir and disturbed the river ecosystem in Grand Canyon National Park downstream. It is also a key player in one of the most interesting ecological experiments in decades, inspired by the work of Dr. John (Jack) Schmidt of Utah State University, and conducted by the Glen Canyon Dam Adaptive Management Program and the Department of Interior.