NSW Water Quality and River Flow Objectives About the Objectives Department of Environment, Climate Change and Water   Select from the scrolling list, statewide map or catchment list Select a catchment Barwon-Darling and Far Western Bega River Bellinger River Border Rivers Brunswick River Camden Haven and Hastings River Castlereagh River Clarence River Clyde River and Jervis Bay Cooks River Georges River Gosford and Northern Beaches Lagoons Gwydir River Hacking River Hawkesbury-Nepean River Hunter River Karuah River and Great Lakes Lachlan River Illawarra Lake Macquarie and Tuggerah Lakes Macleay River Macquarie-Bogan River Manning River Moruya River Murray River Murrumbidgee River and Lake George Nambucca River Namoi River Richmond River Shoalhaven River Sydney Harbour and Parramatta River Towamba and Genoa River Tuross River Tweed River Williams River

Sydney Harbour and Parramatta River
River Flow Objectives explained

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• Recommending variations to objectives
• Protect pools in dry times
• Protect natural low flows
• Protect important rises in water levels
• Maintain wetland and floodplain inundation
• Mimic natural drying in temporary waterways
• Maintain natural flow variability
• Maintain natural rates of change in water levels
• Manage groundwater for ecosystems
• Minimise effects of weirs and other structures
• Minimise effects of dams on water quality
• Make water available for unforeseen events
• Maintain or rehabilitate estuarine processes and habitats

This section explains each of the River Flow Objectives (RFOs). See the RFOs for the Sydney Harbour and Parramatta River catchment.

In total, there are twelve coastal River Flow Objectives-each dealing with a critical element of natural flows in rivers and estuarine processes.

Flow patterns in many waterways have been significantly altered and will not be returned to natural flow regimes. The NSW Government is not attempting to restore completely natural flow patterns where the community significantly benefits from alterations to flow patterns. Communities and the Government have identified important areas where we can make adjustments to maintain or improve river health while continuing to benefit from water use.

Water sharing plans (WSPs) where developed, will contain integrated actions and timeframes to achieve objectives and implement identified actions in consultation with the community. Different approaches and outcomes may apply across the catchment.

Recommending variations to objectives

The Natural Resources Commission (NRC) will review the role of WSPs in achieving state-wide natural resource management standards and targets after 5 years of the plan being made. As part of this review the NRC will call for public submissions and consider other state-wide policies or agreements that are relevant to the catchment management area. The Minister for Natural Resources will consider the review undertaken by the NRC when deciding whether to extend the duration of the current water sharing plan or to make a replacement plan.

The Minister may also amend plan actions at any time if the plan so allows or if it is deemed to be in the public interest to do so.

	Protect pools in dry times
	Protect natural water levels in pools of creeks and rivers and wetlands during periods of no flows

During dry times, some streams stop flowing or form pools. Pools and wetlands are refuges for aquatic plants and animals. Pumping water from them can make it more difficult for many species to recover after a drought.

Measures to achieve objective

• There should be no water extraction from streams or wetlands in periods of no flow.

Supporting information

• The objective has limited application to this catchment.
• Along with social and economic considerations, WSPs should define when and how to protect specific pools:
• in natural wetlands with licensed pumps
• in streams where flow occurs under the sediment surface
• where these pools have become deeper or shallower.

	Protect natural low flows
	Water extraction and storage are high in dry times and impose long artificial droughts that increase the stress on aquatic plants and animals

Measures to achieve objective

• Share low flows between the environment and water users and fully protect all natural very low flows. These are defined as:
• Very low flows: flows below the level naturally exceeded on 95% of all days with flow
• Low flows: flows below the level naturally exceeded on 80% of all days with flow
• In streams with little water use or important conservation values, minimise risks to ecosystems in low-flow periods.

Supporting information

• The objective has limited application to this catchment.
• WSPs need to identify actions to achieve targets for each stream that balance local environmental, social or economic considerations.
• In urban streams, the changes made to the natural low-flow regime are generally unknown. Streams may be wetter than natural because of garden watering in the catchment. Alternatively, if inputs to groundwater are reduced, streams could be drier than natural during dry times. Site-specific studies and comparison with undeveloped streams would be needed to determine the amount of change.

	Protect important rises in water levels
	Protect or restore a proportion of moderate flows ('freshes') and high flows

Rain causes peaks in river flows. This 'pulsing' of flows may trigger migration of animals or reproduction of plants and animals; provide over-bank flows to wetlands and floodplains; shape the river channel; and control water quality and nutrients. Water storage and extraction can alter or remove freshes, inhibiting these vital processes. The height, duration, season and frequency of higher flow events are all important.

Measures to achieve objective

• There is little water harvesting in this catchment, so a target is not needed.
• In areas of new development, ensure that stormwater is managed in such a way that there is no increase in the height or flow rate of high flows.
• In areas of existing development, explore opportunities for improving stormwater management to mitigate flooding.

Supporting information

• High flows may cause flooding, which is a significant community concern. Mitigation requires both better stormwater management (increased detention and infiltration) and planning to avoid the problem (relocating houses and infrastructure away from flood-prone areas and preventing new development in these areas).
• Adequately managing stormwater is more achievable in new developments, and may be costly and difficult to retrofit in existing developed areas.
• All councils in this catchment are required to develop stormwater management plans (under the Urban Stormwater Management Program).

	Maintain wetland and floodplain inundation
	Maintain or restore the natural inundation patterns and distribution of floodwaters supporting natural wetland and floodplain ecosystems

Floodplain and wetland ecosystems develop in response to the flow patterns and the landscape between the river and wetlands or floodplain. Floodplain works can change the flooding patterns, which will then lead to changes in habitat and vegetation. These changes can be expected to result in reduced or different species diversity and abundance (particularly in reduced numbers of native fish) and water quality problems.

Measures to achieve objective

• Management plans and actions for waterways need to include strategies to maintain, restore or mimic natural patterns of inundation, water movement and drying in natural and semi-natural wetlands, and remaining native floodplain ecosystems.
• Ensure adequate access for native fish to and from floodplain wetlands.
• Flooding patterns should not be altered without proper environmental assessment.

Supporting information

• Implementation of this objective will be needed in only a few locations.
• Maintaining wetlands and floodplains will improve water quality and reduce downstream flooding.

	Mimic natural drying in temporary waterways
	Mimic the natural frequency, duration and seasonal nature of drying periods in naturally temporary waterways

In urban areas, the preponderance of hard surfacing (e.g. paved or concreted areas) and garden watering can cause streams and wetlands to be wetter than natural. In streams and wetlands that naturally dry out, this can create problems in maintaining habitat, vegetation, nutrient cycling and signals for breeding. Natural wetting/drying cycles produce diversity of habitat and, therefore, high species diversity.

Measures to achieve objective

• Identify any streams where unnatural flows have greatly reduced drying periods. Assess potential short- and long-term environmental, economic and social effects of this change and of possible management alternatives.
• Decisions on what (if any) action is appropriate to implement this objective in streams should be worked out on a case-by-case basis after giving due consideration to local views.

Supporting information

• The objective has limited application in this catchment.
• There are few streams where drying periods differ significantly from natural conditions. In urban streams, the change to the natural low-flow regime is generally unknown. Streams may be wetter than natural because of watering in the catchment; alternatively, if inputs to groundwater are reduced, streams could be drier than natural during dry times. Site-specific studies and comparison with undeveloped streams would be needed to determine the change.

	Maintain natural flow variability
	Maintain or mimic natural flow variability in all streams

Australia's rainfall and river flows are naturally variable. The way we currently store and divert river water can reduce natural pulsing of water down rivers and maintain artificially high or stable river heights. In urban areas and other places where the ability of the land to absorb or detain rainfall is reduced, more water runs off rapidly, so water levels will rise higher. These changes often create problems with streambank stability, biodiversity and signals for breeding and migration.

Measures to achieve objective

• Identify streams with unnatural flow variability and develop appropriate actions to mimic natural variability.
• Identify streams with potential for flow variability problems and take early action.

Supporting information

• The objective applies mainly to controlled rivers but may apply at some locations or situations on uncontrolled streams, such as in urban streams. In these areas, the objective should be addressed through stormwater management plans.
• The objective may also affect achievement of Water Quality Objectives.

	Maintain natural rates of change in water levels
	Maintain rates of rise and fall of river heights within natural bounds

Water levels may rise too quickly in urban areas, with consequent risk to people and aquatic plants and animals. If water levels fall too fast, water does not drain properly from riverbanks and the banks may collapse. Migration of aquatic animals may also be restricted by such sudden falls in river height.

Measures to achieve objective

• Identify locations where water levels often rise or fall faster than they would naturally. Identify the reasons (in urban areas, usually the result of increased hard-surfacing) and impacts. Remedial action requires case-by-case assessment.
• Identify potential problems and take early action.

Supporting information

• Local information, such as bank erosion, may indicate a need for action (e.g. Toongabbie Creek).
• In urban streams, solutions may require increasing on-site detention or infiltration.
• Of all uncontrolled stream categories, this objective applies most to urban streams.
• Consideration should be given to prioritising the rehabilitation of channelised streams.

	Manage groundwater for ecosystems
	Maintain groundwater within natural levels and variability, critical to surface flows and ecosystems

Some shallow groundwaters are directly linked to flows in streams and wetlands. They may provide base flows in rivers during dry periods and they may be primary sources of water for floodplain and riparian vegetation. Also, serious depletion of groundwater in dry times may lead to unnatural recharge of groundwater from surface waters during the next flow event. Lowering groundwater in many coastal areas may expose acid sulfate soils.

Measures to achieve objectives

• Implement the State Groundwater Policy (DLWC 1997a, 1998b).
• Identify any streams or ecosystems that may depend on high groundwater levels, and assess impacts of reduced recharge or excessive pumping or drainage.
• Identify areas where rising groundwater may threaten ecosystems or surface-water quality.
• Determine appropriate action to keep ground-water level changes within acceptable bounds.

Supporting information

• WSPs should identify areas and actions needed, particularly where there are threatened ecosystems.
• This objective also covers areas of acid sulfate soils, where draining can mobilise acid and toxic metals, affecting surface ecosystems.

	Minimise effects of weirs and other structures
	Minimise the impact of instream structures

Most instream structures (e.g. weirs) convert flowing water to still water, thus altering habitat and increasing the risk of algal blooms or other water quality problems. Barriers prevent passage of plant propagules (e.g. seeds) and animals.

Measures to achieve objective

• Implement the NSW Weirs Policy (DLWC 1997b).
• Identify, and take action to minimise, the impact on native fauna of other structures that impede movement of water-e.g. floodgates, tidal barriers, culverts.

Supporting information

• The Government's NSW Weirs Policy (DLWC 1997b) and weir review process helps set priorities and assess management options.

	Minimise effects of dams on water quality
	Minimise downstream water quality impacts of storage releases

Many storages release water from the bottom of reservoirs where temperatures and dissolved oxygen are low and nutrients are high. These changed water quality conditions can affect the river downstream for hundreds of kilometres. For instance, many native fish will not breed in colder water.

Measures to achieve objective

• Determine whether the water quality of storages limits achievement of Water Quality Objectives in unregulated streams and, if so, develop appropriate actions.

Supporting information

• Limited application in this catchment, but may apply to releases from urban stormwater detention basins or floodgates, particularly with respect to dissolved oxygen, acidity and algae.

	Make water available for unforeseen events
	Ensure river flow management provides for contingencies

Unpredicted events occur in rivers at various times, such as algal blooms or the start of bird breeding seasons. As river flows are a major determinant of many of these processes, we can sometimes alleviate a water quality or environmental problem by better managing river flows.

Measures to achieve objective

• There is no specific target.

Supporting information

• The objective does not apply to this catchment.

	Maintain or rehabilitate estuarine processes and habitats
	Maintain or rehabilitate estaurine processes and habitats

Coastal lagoons, estuaries and river mouths often change naturally in response to storms or tides. Flood mitigation structures, weirs and other works also affect estuaries by limiting tidal flow, changing salinity conditions or altering water levels. Development of estuarine areas can also lead to disturbance of acid sulfate soil deposits, which can then release large amounts of sulfuric acid and toxic metals into the estuarine environment.

Upstream management of rivers also affects estuaries and lagoons. Stormwater carries nutrients, organic matter and sediments. Scouring as a result of flooding can affect the opening and closing of river mouths. Reduced freshes and flooding in estuaries severely depletes food sources for estuarine species. This can contribute to a decline in species that use estuaries as habitat or nursery grounds.

Measures to achieve objective

• Dredging beyond minimal maintenance dredging for navigation requires environmental assessment.
• Draining or disturbance of areas of potential acid sulfate soils must be minimised.
• Water-based activities should be controlled to minimise impact on fish habitat.
• Other processes affecting or potentially affecting estuary health need to be addressed-e.g. the impact of increasing urbanisation.

Supporting information

• Dredging or drainage could expose acid sulfate soils. Treatment of acid sulfate soils is expensive and relatively untested; minimising their exposure is the priority.
• Sedimentation is a problem in most enclosed bays that receive stormwater, and dredging is frequently called for by the community. The objectives for dredging should be clearly established, adequate environmental assessment made, and a management plan for the proposal written (and implemented) covering aspects such as minimising the impact on water quality and disposal of sediments. This is particularly important, as many of the sediments (especially those adjacent to industrial or former industrial sites) are contaminated by heavy metals, persistent chemicals and hydrocarbons.
• Fish habitats, such as protected areas, seagrass beds and mangroves, should be protected from pollution. Polluted sites should be rehabilitated.
• Marinas and extensive moorings may affect water circulation patterns or aquatic habitats. In the upper estuarine sections of the Parramatta River, the ferry services may be having an undesirable erosion effect on the banks. This may expose acid sulfate soils and contaminated sediments, and affect the water quality and tidal flows generally.

This page was published 1 May 2006