The Great Sand Dunes National Park and Preserve is a United States National Park located in the San Luis Valley in Colorado. Originally a National Monument, the area was given the distinction of National Park in September 2004. It is the newest of the United States National Parks.
Situated at the base of the Sangre de Cristo Range, the tallest sand dunes in North America can be seen in these Landsat images, acquired in 1987 and 2011. Evident in these images are the changes in the stream flows of the San Luis Valley. The water flows change from year to year and season to season. Water access is especially critical in the region as center pivot irrigation systems (shown as circular features west of the feeder streams) rely on aquifer recharges.