The Cataract River is a tributary

Tributary

A tributary or affluent is a stream or river that flows into a main stem river or a lake. A tributary does not flow directly into a sea or ocean...

 of the Nepean River

Nepean River

The Nepean River is a river in the coastal region of New South Wales, Australia.The headwaters of the Nepean River rise near Robertson, about 100 kilometres south of Sydney and about 15 kilometres from the coast. The river flows north in an unpopulated water catchment area into Nepean Dam, which...

, and hence of the Hawkesbury River

Hawkesbury River

The Hawkesbury River, also known as Deerubbun, is one of the major rivers of the coastal region of New South Wales, Australia. The Hawkesbury River and its tributaries virtually encircle the metropolitan region of Sydney.-Geography:-Course:...

, in New South Wales

New South Wales

New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...

, Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

. The headwaters of the river are in the Wollondilly Shire local government area.

The headwaters of the river are located on the west slopes of the coastal escarpment about 1 kilometre (0.621372736649807 mi) north-west of Mount Pleasant

Mount Pleasant, New South Wales

Mount Pleasant is a suburb in the city of Wollongong, New South Wales, Australia. It is situated on the northern flank of Mount Keira extending across to the Illawarra escarpment. It is home to the Rhododendron Park, found on Parrish Avenue.-History:...

 and are impounded by the Cataract Dam. One of the two arms of the reservoir impounded by this dam reaches to within 5 kilometres (3.1 mi) of the Pacific Ocean

Pacific Ocean

The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

. Below the dam, the river flows in a north-westerly direction before joining the Nepean River at Douglas Park

Douglas Park, New South Wales

Douglas Park is a town of the Macarthur Region in New South Wales, Australia in Wollondilly Shire. It is near the Hume Highway and on the Main Southern railway line. Its station is served by CityRail's Southern Highlands services. It is about 80 km southwest of Sydney. Locals refer to the...

. In total, the river is some 30 kilometres (18.6 mi) long.

The river is an important source of water for the Sydney

Sydney

Sydney is the most populous city in Australia and the state capital of New South Wales. Sydney is located on Australia's south-east coast of the Tasman Sea. As of June 2010, the greater metropolitan area had an approximate population of 4.6 million people...

 region. Water is collected by the dams, weirs and aqueducts of the Upper Nepean Scheme

Upper Nepean Scheme

The Upper Nepean Scheme is a series of dams in the catchments of the Cataract, Cordeaux, Avon and Nepean rivers of New South Wales, Australia. The scheme includes four dams and supplies the Macarthur and Illawarra regions, the Wollondilly Shire, and metropolitan Sydney.- History :The Upper Nepean...

.