Hydrology

 The water resources of the Cocos (Keeling) Islands consist essentially of groundwater and rainwater. Where conditions are favourable, fresh groundwater on coral islands occurs in the form of shallow freshwater lenses. Such lenses are found in some of the larger islands within the Cocos (Keeling) Islands. The upper surface of a freshwater lens is the water table and the lower surface is a boundary between freshwater and saline water. The lower boundary is not a sharp interface but rather is in the form of a transition zone over a number of metres.

The groundwater from these lenses has been and is currently used as the major source of freshwater for potable and other uses on the Southern Home and West Islands. North Keeling Island is too narrow for a fresh water lens to develop. Due to the generally porous nature of the soils and underlying geology, there is no significant surface run-off. Run-off only occurs in localised areas where the ground is compacted and only for very short periods after heavy rain.

Pulu Keeling is also listed as an International Ramsar site

The Ramsar site includes the marine area surrounding the Island along with the terrestrial area of North Keeling Island, matching the boundary of Pulu Keeling National Park.

As an island atoll in its most natural state, North Keeling is a significant biological resource and is internationally important for the conservation of biodiversity. The Ramsar site is one of the few remaining islands where rats have not yet been introduced, and is generally unaffected by feral animals.

The Ramsar site is also an internationally significant seabird rookery. Fifteen species of birds recorded on the Island are listed under international migratory bird agreements and 15 seabird species use the atoll for nesting. The breeding colony of the dominant bird species, the red-footed booby, is one of the largest in the world. It is also the main locality of the endemic Cocos buff-banded rail.

Find out more about Pulu Keeling as a Ramsar site