Catchment challenges

The Hawkesbury Nepean catchment is a highly diverse and complex catchment which is facing a number of major challenges.

It is a catchment under pressure from the demands of supplying vast resources to Sydney and the rest of Australia, and is housing much of Sydney's rapidly growing population.

Some of the key issues and challenges identified in the CMA's Catchment Action Plan include:

State	Pressure	Response examples
Unnatural flow patterns with constant low flow levels below dams and consistent high flow levels in some unbanked tributaries	Natural variation in river level is replaced by a constant low flow Some tributaries, notably South Creek, have an artificially high flow level due to STP inflows	Metropolitan Water Plan recognises progressive implementation of an environmental flow regime
Higher frequency and/or lower temperature burns can alter species mix and reduce sustainability of bushland	Bushland, particularly where it adjoins residential development, is subject to frequent burning	Department of Planning and the NSW Rural Fire Service have developed a comprehensive framework to plan for bushfire protection. This framework is currently under review. NSW Planning: Plans for Bushfire Protection
12.3% of original extent of EECs on the Cumberland Plain. Only 0.8% of original extent conserved in reserved lands	Clearing for agriculture and urban development in Western Sydney High value of land makes conservation of remnants difficult to sustain	Structure plans for the NW and SW sectors recognise the importance of maintaining significant remnants and include many within the landscape and rural lifestyle areas (NSW Government 2006c)
Inadequate drinking water supply for urban areas in some parts of the catchment including Goulburn	Rainfall rates are highly variable throughout the catchment with rainfall as low as 600 mm/yr in many areas including the catchment area for Goulburn's water supply	Goulburn Mulwaree Sustainable cities project which is a $32 million project to secure Goulburn's water supply by reclaiming effluent and returning to Sooley Dam. Goulburn: Roads
Loss of water flow in Cataract and Bargo Rivers due to cracking in stream bed	Underground coal mining and excavation for first workings under streams and rivers or within riverine corridor. Potential expansion to Nepean River or vicinity with similar bedrock structure to areas where underground mining has already been linked to major cracking of streams with associated release of methane gas, changed morphology of streams, bank erosion and loss of habitat	The potential impact of long-wall mining as an activity that can alter habitat has been recognised through its listing as a key threatening process under TSC Act in July 2005 National Parks: Long Wall Mining
Lower groundwater levels	High levels of groundwater extraction lower the watertable and impact on sustainable agriculture and groundwater-dependent ecosystems	Groundwater sharing plans are being prepared by Department of Natural Resources (DNR) Kulnura Mangrove Mountain Groundwater Plan. Gazetted: 7 February 2003 Water Sharing
Estuary unable to sustain Sydney rock oyster industry resulting in a loss of sustainable catch of 20 million oysters per year and loss of filtering of 1 GL of estuary water per day Refer: University of Queensland 16 May 2005 or	Oysters increasingly susceptible to QX virus caused by factors such as insufficient flow; high nutrient levels or variations in nutrient levels	Industry restructure package including removal of wooden racks, introduction of Pacific oysters and QX-resistant strains of Sydney rock oysters.
Main stem of Hawkesbury-Nepean River subject to aquatic weed outbreaks and algal blooms Coxs River also subject to frequent algal blooms	High levels of water extraction Retention of water in dams results in less than 5% of natural flow below the dams in Hawkesbury River Coxs River highly regulated for electricity generation	Support for ongoing aquatic weed harvesting program 2006 Metropolitan Water Plan recognises progressive implementation of an environmental flow regime and includes a comprehensive recycling strategy (NSW Government 2006a)
High levels of nutrients in creeks and drainage lines	Effluent from 39 sewage treatment plants (STPs) (including 27 SWC or municipal STPs) servicing much of the catchment population discharges into river system Below Penrith Weir, STP effluent contributes up to 80% of the average daily flow in the main stem of the river Treatment quality is high but large volumes means that there are high nutrient loads overall Intensive agriculture (e.g. poultry, mushroom, market gardening and turf farming) contributes nutrient rich run-off.	Metropolitan Water Plan includes strategies to increase standard of treatment of effluent from STPs to even higher levels before discharge into river system Water for Life: Metropolitan Water Plan Support water-efficient agricultural practices and best practice fertiliser use