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 supplies water for Sydney. North of the dam, the river forms the western edge of the Sydney Basin, flowing past the towns of Camden and Penrith, south of which flowing through the Nepean Gorge. Near Penrith it is joined by the Warragamba River. North of Penrith, at the junction of the Grose River near Yarramundi, the Nepean becomes the Hawkesbury River.

There are 11 weirs located on the Nepean River that significantly regulate its natural flow. The river has been segmented into a series of ‘weir lakes' rather than a freely flowing river and is also impacted by dams in the Upper Nepean catchment.

The Wallacia Weir was initially built as a wooden weir for the John Blaxland flour mill at Grove Farm. The first Australian fishsteps were built when the current concrete weir was built at the beginning of the Nepean Gorge, an anticendant entrenched meander caused by the slow uplift during the Blue Mountains orogeny carved down through the Hawkesbury sandstone ~50Mya.

In the 1950s the building of the Warragamba Dam across the steep gorge of the Warragamba River, the Nepean’s major tributary, intercepted the flow of the great bulk of its waters and diverted them to meet the needs of the growing Sydney metropolitan area, reducing the river to a shadow of its former self.

These dams and weirs have had a potent effect, blocking migratory native fish like Australian bass (also locally commonly known as perch) from much of their former habitat, and reducing floods and freshets needed for spawning. Nevertheless, the Hawkesbury/Nepean remains an important and popular wild bass fishery.

The luscious banks of the Nepean River provide a natural haven for local flora and fauna and a quiet location for local residents to relax. At Emu Plains, the western bank of the river provides a location for outdoor theatre productions on warm summer nights. The eastern bank at Penrith provides barbecue facilities and children's play equipment, as well as a wide pathway running for several kilometres for strolls along the riverbank. The eastern bank is also the home of the Nepean Rowing Club.