The Rio Grande, which flows from southwestern Colorado for before entering the Gulf of Mexico, was classified in 1993 as one of North America's most endangered or imperiled rivers. The Rio Grande flows south into the Albuquerque Basin between the Sandia and Jemez mountains. Before entering the basin the river is impounded by the Cochiti Dam, built in 1975. After leaving the basin via Socorro, the river is impounded by the Elephant Butte Reservoir, built in 1916. Within the stretch between these dams, the river passes three mainstream structures that divert water into of levees, canals and drains in the section between Algodones and the Bosque del Apache National Wildlife Refuge. When the river is low, the diversion dams at Isleta and San Acacia can divert all water from the Rio Grande along a stretch of the river. Tributaries include the Jemez River and Rio Puerco from the west, and the Santa Fe River and Galisteo Creek from the east.