An endangered river is one which has the potential to partly or fully dry up, or one that is thought to have ecological issues now or in the near future. Some such issues are natural while others are the direct result of human development. Organisations including the World Wildlife Fund (WWF) have published lists of rivers at risk. The WWF's 2007 list featured the Danube, the Nile, and the Rio Grande amongst others, stating that these "once great rivers" are in danger and "can no longer be assured of reaching the sea unhindered". The US National Park Service reported in 2015 that part of the Rio Grande "often lies dry". Dangers may be the result of the natural change of conditions in the local environment but many are due to human development projects such as dams and irrigation. Humans ha