Hawkesbury River Subcatchment
The Hawkesbury River subcatchment lies on the agricultural and peri-urban fringe of urbanised North Western Sydney.
The upper section of this subcatchment extends from the Nepean River confluence with the Grose River near Yarramundi to the lower estuary of the Hawkesbury River at Webbs Creek near Wiseman's Ferry. The tidal influence in the Hawkesbury River extends into this subcatchment, reaching approximately 145km upstream from Broken Bay.
The Hawkesbury River in this location is under threat from a multitude of land use impacts. The river receives highly reduced flows due to extensive upstream impoundment for Sydney's drinking water. Licensed surface water extraction from this subcatchment is also high, supporting the most intensive and productive agricultural operations in the Sydney basin. The floodplains and riverbanks have been largely cleared for agriculture and recreational use, and riverbank erosion is a serious issue.
There are a number of major Sewerage Treatment Plants discharging into the Hawkesbury River subcatchment which impact on water quality and flow.
The Hawkesbury River has an extremely high social and economic value supporting significant agriculture, recreation and tourism industries in the subcatchment, and there is a very high level of community based environment activity.
This lower estuary area is dominated by bushland interspersed with small, local foreshore settlements. Reserved areas include Ku-ring-gai Chase, Marramarra and Dharug National Parks, and Muogamarra Nature Reserve. These reserved areas help to protect the valuable mangrove communities along much of the foreshore. The tidal influence in the Hawkesbury River extends approximately 145km upstream.
The flows reaching the Hawkesbury River Estuary are highly reduced due to a number of upstream weirs and reservoirs (23 in-stream structures in total) including the major impoundments for drinking water of Sydney's metropolitan area and the Gosford/Wyong areas on the Central Coast. The floodplains of the lower Hawkesbury estuary have been significantly modified by agricultural, recreation and village developments.
The Hawkesbury Estuary has extremely high social and economic values including high recreational usage and commercial fishing. The Hawkesbury River estuary supports the second largest commercial coastal fishery of estuary prawns, oysters (prior to the outbreak of QX disease ) and fish in NSW with a wholesale value of $6.3 million annually. Community based environment activity is very high.