About the Hawkesbury-Nepean catchment
Located on the NSW Central Coast in Greater Sydney, the Hawkesbury-Nepean catchment is one of the largest coastal basins in NSW.
The catchment includes the coastal reaches from Turimetta Headland to Barrenjoey near its mouth. It also includes the catchments for Warragamba, the Upper Nepean and the Mangrove Creek dams, the main water supply reservoirs for the Sydney metropolitan area, including Gosford, Wyong and Wollongong.
With an area of 21,400 square kilometres, over 70 per cent of the catchment consists of mountainous terrain, with about 10 per cent of flat terrain. The south terrain, around 10 per cent of the total catchment, comprises undulating plateau type country. The maximum elevation is about 1,290 metres.
Rivers and tributaries
The main rivers and tributaries include the Hawkesbury-Nepean, Avon, Cataract, Colo, Cordeaux, Coxs, Grose, McDonald, Wollondilly, Warragamba and Wingecarribee rivers.
There are also many creeks including Berowra, Bundanoon, Cascade, Cattai, Cowan, Mangrove, Sooley, South and Mooni Mooni creeks.
Water storages
While the basin is considered unregulated, river flows within much of the catchment are heavily controlled by 5 major dams, as well as various major weirs which retain river flows. These storages include Warragamba, Mangrove Creek, Nepean, Lyell, Avon, Cataract and Cordeaux.
Towns
Penrith, Gosford, Goulburn, Camden, Katoomba, Lithgow, Richmond, Windsor, Moss Vale, Mittagong and Bowral.
Water users
The Hawkesbury-Nepean River system supports a $259 million agriculture industry. Major water users in this catchment include WaterNSW, local councils, the irrigated agriculture, tourism, fishing and oyster industries, and various recreational users. Sydney Water supplies water to most homes and businesses within the greater metropolitan area.
The Hawkesbury-Nepean river is an important environmental asset. Dams and weirs in rivers affect the natural flow of water, water quality, fish migration and habitat. Environmental flows, or water released from a dam or weir, improve water quality, fish passage and habitat conditions.
While the natural flow of many rivers and streams in the Hawkesbury-Nepean River Basin has been significantly altered by water storages such as dams and weirs, the basin is considered an unregulated system. This is because the water storages do not regulate flows downstream – they do not capture and then release water into the river downstream for extraction by users.
Most water storages in the basin are owned and operated by WaterNSW, so Sydney Water can supply homes and businesses in Greater Sydney with a reliable reticulated water supply.
Significant alteration of the natural river flow, intensive urban and industrial development as well as numerous, competing needs for water are key water management challenges.
Specific water management issues include:
- water quality including pollution, algae and weed growth
- river bank management for urban and agricultural development, instream constructions such as pontoons and wharves
- environmental water, ensuring sufficient flows and freshes to maintain river health
- increasing demand for water due to urban population and industry growth
- water accounting.