Visible in this southeast-looking, low-oblique photograph are Fort Randall Dam, which was completed in 1952, and Lake Francis Case. Approximately 150 miles (242 kilometers) long, Lake Francis Case is used for hydroelectric power, agricultural irrigation flood control, and recreation. Agricultural field patterns are discernible on either side of the lake. Long, linear Lake Andes, northeast of Fort Randall Dam, occupies a valley eroded near the end of the last ice age by glacier meltwater. The lake, whose level is maintained by rainfall and two artesian wells, has been set aside as a National Wildlife Refuge. To the south lies the Niobrara River Valley of northern Nebraska.