Imperial National Wildlife Refuge protects about 30 miles of the lower Colorado River in Arizona and California, including the last un-channeled reach before the river enters Mexico. In the Sonoran Desert, its backwater lakes and wetlands form a green corridor and a rare dependable water source, making it important for migratory birds and desert wildlife. Part of the area is preserved as the 15,056-acre Imperial Refuge Wilderness, and the river corridor also supports recreation and access to old mining camps. The refuge is especially significant for conserving a river landscape and riparian habitat that have been heavily diminished elsewhere along the lower Colorado.