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1/2006 Sydney Harbour dioxin threat post Olympics 2000


22/3/05...MP Turnbull useful contribution to Sydney water recycling push, break up of Sydney Water monopoly on World Water Day

16/3/05...So called 'draft' (but really approval) conditions for Port Botany expansion, with introduction on the NSW framework of Environmental Impact Assessment (EIA) and Commission of Inquiry (CoI) process.

15/3/05...Strong opinion piece by Fairfax journalist on dodgy urban planning by Sydney Harbour Foreshore Authority affecting critical open space and waterways.

12/2/05...Carr govt fails Gwydir wetlands, greenies legal appeal goes down

9/2/05...NSW Greens grim take on river ecology on the way out here

15/1/05...strong statistics on 1/3 Sydney's water use threatening health of Shoalhaven: Peatling SMH

13/1/05...cut Sydney water use by half says industry reform group, but Premier says no, with good links: AP via SMH


Sydney Water Project - 1994

Following are project sheets of the "Sydney Water Project" environmental water reform plan (originally published 1994) by a collective of NSW based environment groups. It has dated very well and still provides a template for the future. The first two sheets are here and the others will be added in due course (a copy can be mailed by request to ecology action, 1 Henry St Turrella 2205 and $10 for copying, postage, handling):

Project sheet titles are:

  1. estuaries, beaches & coastal waters
  2. rivers
  3. sludge
  4. stormwater
  5. source control
  6. sewage treatment
  7. Indicators of environmental quality
  8. water efficiency
  9. water re-use



1. estuaries, beaches & coastal waters

A diverse range of marine and estuarine ecosystems are affected by Sydney Water's activities. They include estuaries of the major urban rivers &endash; the Hawkesbury, Georges, Parramatta, Lane Cove, Cooks and Hacking Rivers; Sydney Harbour and Botany Bay; Lake Illawarra; numerous smaller river and lagoon systems; and the ocean beaches of Sydney and the Illawarra.

This leaflet focuses on the effects of the discharge of sewage effluent, sewer overflows and stormwater on these areas.

coastal sewage effluent discharges

* Ten sewage treatment plants (STPs) [as at 1995] discharge sewage effluent to coastal waters off Sydney and the Illawarra, as well as two small outfalls which discharge untreated sewage. All up these account for more than 85 percent of sewage flows generated in Sydney Water's area &endash; or around 1040 million litres (enough to fill more than 500 Olympic swimming pools!) &endash; of effluent every day. [Sydney Water was previously known as the Water Board.]

The level of treatment provided by the coastal STPs is generally low &endash; primary or less at the largest plants in Sydney and the Illawarra. Less than 5 percent of flows receive secondary treatment.

Should Sydney Water follow other Australian coastal cities and provide a higher level of treatment to effluent discharged to the ocean? For instance, in Perth, where around the same percentage of sewage effluent is discharged to the ocean, half receives secondary treatment. At coastal STPs in the United States, secondary treatment is required by law. This is a more cautious long-term approach to protecting marine organisms and habitats.

However, similar or greater environmental benefits may result by keeping full primary treatment as the goal, but improving the opportunities for re-use (of effluent and sludge) and decentralisation within the system. When financial resources are limited, investing large sums of money in improved treatment processes at the 'end of the pipe' tends to encourage centralised treatment systems, and can act as a disincentive for re-use.


  • Primary treatment: initial stage where sewage is settled in tanks so that solids sink to the bottom and oil, fats and grease float to the surface. Removes up to 60 percent of suspended solids and 30 percent of organic matter.
  • Secondary (or biological) treatment: the next stage, in which bacteria are used to
  • break down organic matter in sewage and further settling of solids occurs. At least 85 percent of both components are removed.
  • Tertiary treatment: processes, including sand filtration, oxidation ponds and use of wetland filters, to further improve secondary quality effluent, including removal of nutrients and greater than 95 percent of suspended solids.
  • Faecal coliform bacteria: bacteria that inhabit the intestines of humans and warm-blooded animals and that are present in faeces.
  • Organochlorine: synthetic chemicals containing chlorine and carbon. Most are toxic, break down very slowly in the environment, and can accumulate in tissues of aquatic organisms. Important examples are pesticides such as chlordane and heptachlor.
  • Biota: the total of all living things in a designated area.
  • Bioaccumulation: process whereby chemical substances are taken up by aquatic organisms directly from the water or from consumed food, concentrated within body tissues and passed from one organism to another through the food chain.private sewer: pipes that connect individual homes, businesses and industrial premises to the main (Sydney Water owned) sewer. It is the property owner's responsibility to maintain these pipes.

taking sydney's sewage further out to sea

* You may remember the environmental degradation resulting from years of shoreline sewage discharge at Bondi, Malabar and North Head. By the late 1980s water quality at most Sydney beaches was extremely poor.

Bathing waters at popular beaches close to these outfalls failed guidelines for faecal bacteria on up to 80-90 percent of days. Visible sewage pollution, such as litter and grease, occurred frequently. Studies showed the risk of respiratory illness and gastrointestinal infections was much higher for people who swam at beaches affected by sewage pollution than in the general population.

Since these outfalls have been relocated to deeper waters &emdash; two to four kilometres out to sea &emdash; there has been a dramatic improvement in the degree and frequency of bacterial contamination of bathing waters.

Sydney beaches on the whole are clean (in terms of faecal coliform levels) on 95 percent of days, while incidences of visual sewage pollution are much reduced. For instance, in the 1989-90 summer levels of faecal coliform bacteria at South Steyne Beach exceeded guidelines 70 percent of the time; by the summer of 1992-93 it was down to 6 percent. At Bondi, it decreased from 50 to 4 percent of days.

not out of sight, out of mind

* Discharging sewage further out to sea does not put it out of sight, out of mind forever. The long-term effects of discharging minimally treated sewage on the marine ecosystems of the deeper waters are not known.

The NSW Environment Protection Authority has undertaken the Environmental Monitoring Program (EMP), which detected significant changes in the abundance of soft sediment organisms and fish in the vicinity of the deep ocean outfalls. The factor responsible has not been identified.

Some fish near the old shoreline outfalls had accumulated levels of organochlorine chemicals and metals, which &emdash; under current guidelines &emdash; made them unsuitable for human consumption. As these contaminants can be transferred and magnified through food chains in a process called bioaccumulation, there was the potential for widespread effects on the marine ecosystem.

The EMP has found no evidence as yet of significant accumulation of metal and organochlorine contaminants in the sediments and in local fish, or in experimental oysters moored near the deep ocean outfalls. But since the outfalls have been in operation, only two years' data has been collected.

The measurement phase of the EMP, which ran for five years, has now been completed. Long-term environmental monitoring of coastal sewage discharges overseas shows that the magnitude and geographical extent of effects generally increase over time. Further studies will be required for Sydney's deep ocean outfalls.

The long-term effects of sewage discharge on nutrient levels and the growth and composition of marine plant life also needs detailed investigation. Excessive nutrient levels in a body of water causes abundant growth of aquatic plants &emdash; for example, blooms of red tide algae &emdash; and can lead to depletion of dissolved oxygen in a process called eutrophication. Eutrophication is a widespread and serious problem in coastal waters around the world.

sewage discharge at the shoreline

* Three STPs still discharge primary treated sewage from shoreline outfalls. Port Kembla and Bellambi STPs in Wollongong are being overloaded by increased sewage flows. Bacteriological guidelines at adjacent beaches are frequently exceeded, and visual sewage pollution often reported by Sydney Water and local authorities.

Boat Harbour, next to the Cronulla STP outfall, is now the dirtiest beach in Sydney and only meets guidelines for faecal bacteria on 75 percent of days. A study by Sydney Water confirmed Cronulla STP as the source of most of this pollution.

problems in one of sydney's few remaining natural areas

* Two of Sydney Water's STPs discharge tertiary treated effluent to Berowra Creek, an estuarine tributary of the Hawkesbury River. Nutrients, particularly nitrogen, in the effluent, along with urban runoff, septic seepage and other sources in the Hornsby area, have contributed to frequent dramatic blooms of red tide algae in recent years. On several occasions the algae have been toxic, or have reduced the dissolved oxygen to the point of causing large kills of fish, mussels, barnacles and other invertebrates.

Although nitrogen is the most important nutrient controlling algal growth in estuarine systems, the STPs do not remove enough of it, and in 1992-93 around 500 kilograms of it was added to the creek each day.

Sydney Water plans to expand these plants and improve nitrogen and ammonia removal. However, if urban development in the sensitive Berowra Creek catchment continues at a rapid rate, environmental improvements from better treatment are likely to be eroded by any additional volumes of effluent.

unsewered areas: a different kind of challenge

* Unsewered areas relying on local or on-site sewage disposal methods remain on the fringes of Sydney and Wollongong.

Badly suited or antiquated methods, such as septic systems, have polluted local creeks and lagoons in many of these areas including Gerringong-Gerroa, and north of Wollongong from Wombarra to Otford. Others, such as Bundeena-Maianbar, Brooklyn and Pittwater are surrounded by national park or within protected areas.

For a number of reasons including high costs, standard engineering solutions are not suitable. Could these areas be prime candidates for non-traditional innovative solutions, such as small scale treatment systems with local re-use? Or a holistic plan that incorporates the total water cycle of water supply and sewage treatment?

the legacy of past planning: sewer overflows

* Frequent sewer overflows are a symptom of aging and extended sewerage systems, which have been stretched beyond their intended capacity by continuing urban sprawl. The problem is that stormwater enters the sewers when it rains.

Illegal connections of roof drain pipes, cross-connections with stormwater systems, poorly sealed access lids and infiltration through cracks and joints in pipes are just some of the ways stormwater gets in.

Overflow points relieve the pressure when wet weather sewage flows are too large for the sewer; when blockages form; or in the case of mechanical and electrical failures. There are more than 3,000 points designed into the coastal sewerage systems, and at least an equal number of access fittings, from which sewage can overflow. They discharge to stormwater channels direct to the harbour and to estuaries, rivers, lagoons and beaches.

Wet weather problems are worst in Sydney Harbour and the lower reaches of the Lane Cove, Parramatta, Georges and Cooks Rivers. For instance, in a large storm in February 1992 around 6,700 megalitres of sewage flowed into the Harbour. This was more than five times the volume of sewage that reached North Head STP. [This may change depending on the success of the NorthSide Sewerage Tunnel or NSST still to be fully operational, FoE editor 2001.]

The short and long-term effects on aquatic organisms and habitats are poorly understood. Water quality is influenced by factors such as the nature of the sewage and whether the waterway is well flushed. Others are: oxygen depletion; contamination with faecal bacteria; elevated levels of nutrients and ammonia; and turbidity (muddiness). Waterways can be unsuitable for recreational use for several days after overflows.

Oysters and other filter-feeding shellfish accumulate pathogens (viruses and bacteria) and other contaminants in sewage overflow, making them unsafe to eat. This has already been a problem in the Georges River estuary and Woolooware Bay. Economic and human health consequences can be serious.

urban sprawl threatens marine and estuarine areas

* The new urban growth planned for fringe areas of Sydney and the Illawarra will add to the load on existing coastal sewerage systems.

For instance, by the year 2021:

* flows of sewage to the coastal plants may increase by around 30 percent &emdash; or an extra 320 million litres each day; and

* sewage flows to the Berowra Creek plants may increase by up to 50 percent.

And it seems the ocean has been earmarked as the disposal route for wastes from much of this forecast urban growth.

what Sydney Water has proposed

* Sydney Water's discussion paper Choices for Clean Waterways, released in March 1994, outlines the financial and environmental risks and benefits for a number of strategic options for sewage and stormwater services.

Options relating to coastal and estuarine areas boil down to the following:

* improved control over domestic and trade sources of waste;

* modifying sewerage systems to reduce overloading and increase efficiency; and

* treatment upgrades at the coastal plants to at least full primary treatment, starting at the minor plants with shoreline discharge and working up to the larger plants.

Upgrades are expensive. Costs are estimated at $300 million for full primary treatment at all plants (roughly $230 per household), $2 billion if these all have high dilution outfalls (roughly $1,500 per household), and $3.5 billion for minimal secondary treatment at all facilities (roughly $2,700 per household). [1994 figures.]

Many options in Choices and other strategic planning reports revolve around reducing the number of coastal STPs and discharging a greater proportion of the wastes generated by people in the Sydney area to the ocean. They also hinge on longer outfalls (which achieve greater dilution of effluent with seawater) as the main tool for managing sewage pollution.

One widely discussed proposal involves transferring effluent or untreated sewage from inland plants, &emdash; particularly from the Hawkesbury-Nepean &emdash; to the coast.

Effluent transfer is not limited to inland plants. For example, in current plans to upgrade Cronulla STP, one proposal is to close the Potter Point outfall and pipe either untreated sewage or treated effluent from Cronulla to Malabar STP for discharge and/or treatment.

Effluent re-use and no-discharge options such as composting toilets and on-site re-use are investigated in Choices. But they need to be evaluated against the long-term environmental benefits of reducing or ceasing discharge of sewage wastes to the ocean. After all, it's much easier for Sydney Water to be positive about the 'pipes and plants' solution it knows best.


* Future proposals for the current system raise three key questions:

* Is it ecologically sustainable or scientifically justifiable to build more deep ocean outfalls? This sees the ocean as a manageable ecosystem for our wastes and assumes it has the capacity to assimilate all components in the waste.

* Is it equitable to transfer wastes from inland areas or coastal catchments to one place for ocean discharge? This may amount to protecting one environment at the expense of another.

* Is a genuine attempt being made to change the 'pipes and plants' way of thinking?

We do not know precisely to what extent the ocean can cope with wastes, nor can we find out without an ongoing, rigorous and independent environmental monitoring program. We already know this capacity does not exist for certain toxic and persistent compounds. Yet we continue to plan for the ocean to take greater volumes and loads of pollutants. Would it not be more prudent to apply the precautionary principle, whereby if there's any reason to suspect adverse effects, we do not discharge that substance to the marine environment?

Alternative strategies that embrace the precautionary principle include:

* decentralised sewage treatment schemes,

* on-site sewage treatment, such as composting toilets;

* greater re-use of effluent and water conservation;

* pollution prevention (through clean production), with the ultimate goal of zero discharge of wastes;

* setting binding targets for reducing the loads of toxic and/or persistent pollutants discharged in sewage;

* regulatory approaches such as load-based licensing (where the polluter pays for each substance discharged on the basis of possible environmental damage).

tackling sewer overflows

* Options for fixing up overflows include: sealing leaky and broken pipes; eliminating illegal sewer connections; duplicating sewers and building extra storage into the system.

In Choices for Clean Waterways, Sydney Water asks the community to decide to what standard they want the systems repaired. None of the options come cheap, with prices starting at around $2 billion, or roughly $1500 per household. [1994 figures]

Questions raised by these options include:

* When should the large scale sewer repair program begin and how fast should it proceed?

* How can the community decide on the standard of repair particularly when knowledge of long-term effects on aquatic ecosystems is so limited?

* Are we being encouraged to focus on human-use criteria (for example, "swimmability") for sewer repair? This could exclude wider ecological objectives, such as protecting important estuarine habitats, flora and fauna.

* Are problems of leaky and defective private sewers (whose length is equivalent to Sydney Water's sewers) being adequately addressed?

These questions raise the broader issue of what form and size we want our future cities to be. This is not adequately dealt with in Sydney Water's Choices document. Is it ecologically sustainable to continue to expand and build new sewers while existing ones still leak? Won't we be letting ourselves in for more of the same problems of maintenance and stormwater entry?

Could strategies to reduce sewage volumes &emdash; for example, reducing water consumption and limiting new connections to existing systems &emdash;ultimately be more effective than the options presented by Sydney Water?

what can you do?

* Find out how to change the way you use water and put wastes down the sink and toilet. Other leaflets in this series on water conservation, effluent re-use and source control are a good start. Technical reports are also available from the Sydney Water Project.

Sydney Water's public consultation process on its strategic directions provides an opportunity to influence its policies on decentralisation; effluent re-use; water conservation; and other ecologically sustainable approaches to managing water and waste water.

Written by Christine Mercer, Edited by Claire Gerson, Original brochure design by Steve [Bee] (1994).

2. rivers

Sewage treatment and water supply operations of Sydney Water (previously known as the Water Board) have a major impact on rivers and other freshwater environments. In the Hawkesbury-Nepean River system, sewage treatment plants (STPs) discharge approximately 113 million litres of effluent per day (1994 figures). Discharges from these facilities account for 13 percent of the total effluent discharged by Sydney Water's STPs. The remainder is discharged to the ocean.

The effects of the Sydney Water's operations in the Hawkesbury-Nepean are compounded by six dams in the upper catchment, which disrupt the natural flow pattern of the rivers. In other river systems, the impact is mainly restricted to sewer overflows. Although these affect a number of freshwater creeks, the upper and central Georges River are the worst affected.

This leaflet discusses:

  • the ecological implications of Sydney Water's operations for riverine environments;
  • the proposed strategies to reduce these effects; and,
  • asks a number of questions about how to mitigate these effects.
  • what are the effects of Sydney Water's sewage effluent discharges?

The discharge of sewage effluent from Sydney Water's sewage treatment plants (STPs) to the Hawkesbury-Nepean River system is one of the major factors contributing to the river's water quality problems.

Currently, all of the tributary creeks receiving sewage effluent from Sydney Water's treatment facilities are adversely affected. Where there are a number of treatment plants close together, water quality problems extend to the main river channel.

The increases in the number of algal blooms, weed infestations and fish kills in the river are signs of water quality problems. Some of the algal blooms are made up of species of blue-green algae. These produce toxins that are harmful if ingested by livestock or people who use the river.

nutrients, health and toxics &emdash; what objectives are achievable?

*The outbreak of algal blooms in the early 1980s prompted Sydney Water to install phosphorus and nitrogen removal facilities at a number of its STPs. Phosphorus, in particular, was targeted as it is thought to be the nutrient which limits freshwater plant growth.

Sydney Water's efforts to remove phosphorus have met with some success. Its efforts to remove nitrogen from sewage effluent have not been as successful. This is mainly because nitrogen is much more difficult to remove. Furthermore, nitrogen removal has not been a priority because it is believed &emdash; perhaps mistakenly &emdash; that high levels of nitrogen and low levels of phosphorus limit the growth of toxic blue-green algae.

The problem with only targeting phosphorus is that it fails to take into account that fresh water flows downstream into the estuary and ocean. In these salt water areas nitrogen is thought to be the nutrient which promotes algal blooms, not phosphorus.

Sewage discharges into the Hawkesbury-Nepean also raise a number of health issues. Recent data from the NSW Environment Protection Authority shows the river is so contaminated by sewage-related bacteria that the only area suitable for activities such as swimming is below the junction of the Colo River.

Although there is considerable data examining the effect of nutrients, virtually nothing is known about the effects of other environmentally damaging compounds in sewage such as metals, pesticides and herbicides. Should removing phosphorus be the main priority? While algal blooms are a problem, they would occur in any case as part of the river's natural cycle, albeit far less often. If, however, heavy metals are causing fish to develop deformities or cancers, it is a very different problem and one requiring immediate and possibly very different action.

A number of objectives are achievable within five or ten years (as at 1994). These include a river that people can swim in safely; a river where nutrient levels in the mainstream do not adversely affect water quality; improved knowledge about the effects on river ecology of substances present in sewage; and, increased efforts to reduce the total load of toxic substances discharged to the river.

  • How should Sydney Water reduce the quantity of pollutants discharged into the river?
  • What investigations into river ecology are needed?
  • What environmental effects should we be concerned with?
  • Should Sydney Water target all pollutants or should specific pollutants be targeted based on known effect?

what future sewage treatment strategies is Sydney Water proposing?

* Sydney Water has outlined a number of options for reducing the level of pollution discharged to the Hawkesbury-Nepean in its discussion paper, Choices for Clean Waterways, published in March 1994. The options presented can be reduced to four strategies.

1. Improve the level of treatment at existing facilities

This strategy is designed to lower phosphorus levels in the effluent and in turn reduce the occurrence of algal blooms. How these 'improved' processes will reduce the level of other pollutants remains unclear. The compounds remaining in the treated effluent may cause far greater environmental damage than phosphorus.

Improved treatment processes will result in better water quality in the short-term; their effectiveness, however, in the long-term may be undermined by population growth. Upgrade strategies can be like a dog chasing its tail: as effluent volumes increase with population growth, Sydney Water will have to upgrade its plants again and again to retain the same level of water quality in the rivers.

For this strategy to be effective, it has to prevent the total pollutant load from continuing to increase. Source control is one approach that could help. This means reducing the quantity of contaminants produced at the source, that is, in Sydney's homes, factories, shops and offices.

A strategy based solely on improved treatment may not be enough. The need for water conservation, and the value of sewage effluent as a reusable commodity must also be recognised.

2. Reduce/eliminate effluent discharges by re-using the treated effluent

Apart from the obvious environmental benefits that come from reducing the volume of effluent discharged to the river, effluent re-use offers other advantages.

  • It can reduce fresh water consumption, thus delaying or preventing the need to build further costly and environmentally damaging dams.
  • It can be used for irrigation and, in the process, return valuable nutrients to the soil.

Re-using effluent for agriculture means the nutrients in the sewage don't have to be removed. This is fine in dry weather, but what happens when it rains and the effluent is not needed for irrigation? Storage facilities will be needed.

If the effluent can't be stored it will need to be further treated and the nutrients removed before it can be discharged to the river.

3. Divert effluent from the Hawkesbury-Nepean to the ocean

This option would result in environmental benefits to the Hawkesbury-Nepean River system by reducing the volume of effluent discharged.

The protection of this system would represent a trade-off between river pollution and ocean pollution. The consequences of diverting this effluent to the ocean are largely unknown.

Diverting effluent away from the river would reduce river flow unless more water is released from the dams to compensate. The implications of reduced flow are unknown. Ocean transfers represent a net loss of a scarce water resource and are therefore at odds with the principles of Ecologically Sustainable Development.

4. Small-scale treatment

This ranges from individual systems such as composting toilets to treatment plants for communities of 500 to 10,000 people.

Community systems can reduce the risk of sewer overflows by reducing the need for extensive reticulation systems.

Although very different in scale, these systems can reduce environmental damage by increasing the potential to redirect effluent for re-use.

Individual household re-use involves the on-site recycling of grey water. However, there are concerns that nutrient runoff and health risks can result from inadequate treatment and inappropriate siting.


Improved treatment processes will result in better water quality in the short-term; their effectiveness, however, in the long-term may be undermined by population growth. Upgrade strategies can be like a dog chasing its tail: as effluent volumes increase with population growth, the Water Board will have to upgrade its plants again and again to retain the same level of water quality in the rivers.

what are the effects of sewer overflows?

* Overflows from the sewerage system can occur during both wet and dry weather.

Dry weather overflows generally occur due to chokes in the system or mechanical failures.

Wet weather overflows, however, occur when rainwater or groundwater enters the sewers through damaged pipes or cracks in joints (infiltration), or from faulty plumbing or illegal roof pipe connections (inflow). About 90 percent of sewer overflows occur as a result of infiltration.

Many of the 3,000 or more relief structures, which are designed to release the buildup of pressure in the sewerage system, discharge to waterways.

The discharge of large volumes of raw or partially treated sewage into our rivers and creeks in wet weather causes a number of environmental and public health problems.

Major freshwater areas adversely affected by sewer overflows include the upper and central Georges River.

The environmental effects of sewer overflows include:

  • low levels of dissolved oxygen, which make it difficult for fish and other organisms to survive;
  • increased nutrient levels, which result in excessive plant growth; and,
  • high levels of sewage-related bacteria and viruses, which make rivers unsafe for recreation.

The effects of other pollutants discharged during sewer overflows are largely unknown. In the 1990's during dry weather, raw sewage from the Georges River catchment was treated by either Glenfield or Liverpool STPs, and then transferred to a trunk sewer for discharge at Malabar Ocean Outfall.

During wet weather, however, when sewage volumes greatly increase due to inflow and infiltration, effluent from a number of suburbs were diverted to Fairfield Storm STP. This STP only operated during wet weather and only provides partial treatment before discharging directly to a tributary of Prospect Creek.

Sewage discharges from Fairfield Storm STP have been one of the major contributors to poor water quality in this area; the other being urban runoff. Water quality problems are made worse because it takes several weeks for pollutants to be flushed from the creek.

One of the major issues facing Sydney Water in the Georges River catchment is the increase in sewage volumes caused by population growth. It is anticipated that by 2011 dry weather flows will overload the existing sewer. Sydney Water is considering a number of options, including: duplicating the existing sewer; possibly building a new STP on the Kurnell Peninsula; or reducing the number of existing plants.

  • What should Sydney Water be doing to reduce and prevent sewer overflows? Approximately, fifty percent of sewer overflows occur as a result of faulty house service lines which are currently the responsibility of the home owner.
  • What can be done to encourage home owners to address this problem?

Sydney Water has made a commitment to eliminating all dry weather overflows throughout its area of operations. This is the proper approach. Sydney Water must aim to progressively reduce the impact of wet weather overflows by continuing its current program of repairing damaged pipes and removing illegal connections. The problem of faulty house service lines is an issue that needs to be addressed if sewer overflows are to be effectively eliminated.

what are the ecological consequences of Sydney Water's water supply operations?

* Dams and weirs on both the Hawkesbury-Nepean and the Shoalhaven Rivers significantly alter the river's natural flow. As a result, wetlands are not flooded as often, fish breeding and migration is inhibited, and habitat for aquatic animals and plants is reduced.

These effects could be reduced by Sydney Water and other government agencies.

Obstacles to fish migration could be greatly reduced by installing fishways on weirs and by applying fish transfer methods at large dams. The majority of dams and weirs are owned by Sydney Water or the Department of Water Resources (DWR). The Department of Fisheries can direct these organisations to implement fish transfer methods.

Fish breeding, periodic flooding of wetlands and habitat maintenance could all be improved by periodically releasing water from Sydney Water's dams to mimic the river's natural flow. At present, Sydney Water ensures that no less than 50 megalitres per day flows over the weir at Penrith. This volume of water was determined in order to compensate downstream landholders for reduced river flow, and doesn't take into account how much water might be needed to rehabilitate and maintain the river ecosystem.

  • Should Sydney Water and the DWR cooperate in developing techniques to help fish overcome obstacles in the river?
  • Should the operating rules for Sydney Water's dams include the release of water for environmental purposes?
  • What criteria should be used to decide acceptable flows (e.g. maintenance of wetlands, protection of endangered species, and so on)?

what are the likely effects of Sydney Water's future water supply operations?

* In the mid 1990's Sydney Water proposed to increase its water supply operations by various means. One was the raising the wall of Warragamba Dam. After much debate and controversy this proposal was rejected. Other proposals were also considered. Significant ecological consequences would have included:

1. Transfers from the Shoalhaven River to dams in the Hawkesbury/Nepean river system

Transferring water from one catchment to another may introduce a number of exotic fish species into the Hawkesbury/Nepean, which may then displace native fish populations. The broader ecological consequences of transferring water from and between catchments has not been determined.

The transfer of water from the Shoalhaven to the Hawkesbury-Nepean should only be permitted during periods of extreme and prolonged drought. As Sydney's population increases, the demand for water will increase. Transfers from the Shoalhaven should not be seen as a solution to this problem. Inter-basin transfers should be viewed as a last resort. If Sydney's water supply levels do begin to approach critical levels, water restrictions can be used to limit water demand.

* Under what circumstances should Sydney Water transfer water from the Shoalhaven to the Hawkesbury-Nepean?

2. Construction of a new dam at Welcome Reef on the Shoalhaven River

Sydney Water has stated that no new dams will be required before 2030. If Sydney Water were to implement water conservation strategies and re-use on a large scale, the proposed Welcome Reef Dam on the Shoalhaven River could be postponed indefinitely.

3. Raising Warragamba Dam: its potential to reduce periodic downstream flooding

The proposal to increase the flood mitigation capacity of Warragamba Dam would have meant frequent major flooding denied to the river downstream. This could have serious consequences for the river's ecosystem.

4. Raising Warragamba Dam: its potential implications for downstream urban development

A study in in 1994-5 into floodplain management in the Hawkesbury-Nepean River by the NSW Public Works Department considered whether there was a reduced risk of flooding in the Hawkesbury-Nepean basin. If studies show the flooding risk is reduced, it may encourage the NSW government to relax the present land use restrictions and release new areas of land on the floodplain for urban development. This would lead to increased pollution from effluent discharges and urban runoff.

* Should the NSW Government be permitted to relax planning restrictions on urban development in the Hawkesbury-Nepean floodplain and allow the release of more floodplain land for urban development?

5. Raising Warragamba Dam: Reservoir-Induced Seismicity

If the Warragamba Dam wall had been raised by 23 metres to reduce the risk of flooding, it would have caused an enormous additional weight of water to enter the reservoir during large floods. This will increase the risk of a phenomenon known as reservoir-induced seismicity.

Dams are built to withstand the effects of these types of earthquakes, but localised environmental effects may occur. The extent of these effects would depend upon the magnitude of the earthquake.

* Is the increased risk of an earthquake acceptable in order to lower the risk of flooding in the Hawkesbury-Nepean valley?

When the environmental consequences of raising the dam wall for flood mitigation are assessed, the risk of inducing seismic events should also be considered.


* Sydney Water's operations have a range of impacts on the health of our rivers. This leaflet highlights some of these issues.

Sydney Water is now planning for the future, and there is a chance for you to have your say and ensure the crucial questions are being considered.


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