During the wet season, water carried down from the Arnhem Land plateau often overflows from creeks and rivers onto nearby floodplains. Alluvial soils carried in the floodwaters add nutrients to the floodplains. Nutrient-rich soils along with an abundance of water and sunlight make the floodplains an area of prolific plant and animal life. During the dry season the water drains into rivers, creeks and isolated waterholes or billabongs. Kakadu’s wetlands are listed under the Convention on Wetlands of International Importance (the Ramsar Convention) for their outstanding ecological, botanical, zoological and hydrological features.