Lake Carnegie is an ephemeral

Ephemeral

Ephemeral things are transitory, existing only briefly. Typically the term is used to describe objects found in nature, although it can describe a wide range of things....

 lake

Lake

A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

 in Western Australia

Western Australia

Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...

. It fills with water only during very rare periods of significant rainfall, such as during the huge 1900 floods

1900 Western Australian floods

The 1900 Western Australian floods were a series of flooding events from March to May of 1900 that affected large areas of Western Australia, primarily in the Pilbara and Gascoyne regions, though it extended to cover most of the state except the more humid Kimberley and Southwest regions.The...

 and in numerous recent tropical wet season

Wet season

The the wet season, or rainy season, is the time of year, covering one or more months, when most of the average annual rainfall in a region occurs. The term green season is also sometimes used as a euphemism by tourist authorities. Areas with wet seasons are dispersed across portions of the...

s when the monsoon

Monsoon

Monsoon is traditionally defined as a seasonal reversing wind accompanied by corresponding changes in precipitation, but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea...

 and tropical cyclones have been moved south by recent climate change

Climate change in Australia

Climate change has become a major issue in Australia due to drastic climate events since the turn of the 21st century that have focused government and public attention. Rainfall in Australia has increased slightly over the past century, although there is little or no trend in rainfall in northeast...

. In dry years, it is reduced to a muddy marsh

Marsh

In geography, a marsh, or morass, is a type of wetland that is subject to frequent or continuous flood. Typically the water is shallow and features grasses, rushes, reeds, typhas, sedges, other herbaceous plants, and moss....

.

Water entering the lake, unlike in more easterly playas of the Australian arid zone, does not come from well-defined river channels since the soils of the region are so weathered - lacking tectonic or glacial activity since the Carboniferous

Carboniferous

The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...

 ice age

Ice age

An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...

s - that sediment

Sediment

Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....

 is completely absent and the terrain so flat that only the most unweatherable rocks remain on the surface and well-defined river channels cannot form especially since the extreme age of the soils and consequent hihg rooting density of native flora limits runoff to an extreme extent.