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

Hacking 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 each part of the Hacking River catchment.

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

Flow patterns in many rivers have been significantly altered and will not return to natural flow regimes. The NSW Government is not attempting to restore completely natural flow patterns where the community benefits significantly from altered 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 will apply across different parts of 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 and form pools. Pools and wetlands are refuges for aquatic plants and animals. Pumping water from them can make it harder 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 water flows under the sediment surface
• where these pools have become deeper or shallower.

	Protect natural low flows
	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 very low natural flows.
• 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 with important conservation values, minimise risks to ecosystems during low flows.

Supporting information

• The objective has limited application in this catchment.
• WSPs need to identify actions to achieve targets for each stream that will balance local environmental, social and economic considerations.
• In urban streams, changes made to the natural low-flow regime are generally unknown. Streams may be wetter than natural because of garden watering in the catchment; or, 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, and their duration, may trigger migration of animals and 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 flows 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 so that there is no increase in the height or 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 from flood-prone areas and preventing new development in these areas).
• Stormwater is easier to manage properly in new developments, but may be costly and difficult to retrofit in existing developed areas.

	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 flow patterns and the nature of the landscape between the river and the wetlands or floodplains. Floodplain works can change the flooding patterns, with consequent changes in habitat and vegetation. These changes can be expected to reduce or change the diversity and abundance (or both) of species in the ecosystem. In particular, they can lead to reduced numbers of fish, and water quality problems.

Measures to achieve objective

• In management plans and actions for waterways, include strategies to:
• maintain, restore or mimic natural inundation and drying patterns 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 environment assessment.

Supporting information

• This objective needs to be implemented in only a few locations
• Maintaining wetlands and floodplains will improve water quality and reduce downstream flooding.
• Property protection issues need to be taken into account.

	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 would dry out naturally if these impacts were absent, this can create problems in maintaining habitat, vegetation, nutrient cycling and signals for breeding. It can also lead to a high watertable and associated salinity problems. Natural wetting and 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-out periods. Assess the potential short- and long-term environmental, economic and social effects of this change, and of possible management alternatives.
• Decide what (if any) action is appropriate to implement this objective in streams and wetlands on a case-by-case basis, after giving due consideration to local views.

Supporting information

• This objective has limited application in the catchment.
• There are few streams where drying periods differ significantly from those under natural conditions. In urban streams, changes to the natural low-flow regime are generally unknown. Streams may be wetter than natural because of watering in the catchment; or, 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 changes.

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

Supporting information

• This objective applies mainly to controlled rivers but may apply in some locations or situations in uncontrolled streams, such as in urban streams. In these areas, the objective should be addressed through stormwater management plans.
• This objective may also affect the 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 they may collapse. Migration of aquatic animals may also be restricted by 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 observations, such as of bank erosion, may indicate a need for action.
• In urban streams, solutions may require increasing on-site detention or infiltration.
• Of all categories of uncontrolled streams, urban streams are most affected by this objective.
• 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 may be primary sources of water for wetland, 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. Lowering groundwater in many coastal areas may expose acid sulfate soils.

Measures to achieve objective

• Implement the State Groundwater Policy (DLWC 1997a, 1998b).
• Identify any streams or ecosystems that may depend on high groundwater levels, and assess whether impacts on these may be caused by changed recharge rates or excessive pumping.
• Identify areas where groundwater may be rising and likely to threaten ecosystems or the quality of surface waters.
• Determine appropriate action to keep changes in groundwater levels within acceptable bounds.

Supporting information

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

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

Most instream structures (e.g. Audley Weir) convert flowing water to still water, thus altering habitat and increasing the risk of algal blooms or other water-quality problems. Barriers restrict the 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 reduce the impact on native fauna of other structures that impede the movement of water-e.g. floodgates, tidal barriers, and culverts.

Supporting information

• The 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 dams release water from the bottom of reservoirs, where temperatures and levels of dissolved oxygen are low and nutrient concentrations are high. These differences in water quality 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 water quality from dam releases limits achievement of WQOs in unregulated streams and, if so, develop appropriate actions.

Supporting information

• This objective has limited application in this catchment but may apply to releases from urban stormwater detention basins or floodgates, particularly with regard to levels of dissolved oxygen, acidity and algae.

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

River systems can sometimes be affected by unforeseen or irregular events-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 in this catchment.
• Protecting or mimicking elements of a natural flow regime is preferable to making water available for unforeseen events.

	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 disturb acid sulfate soil deposits, which can 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 deplete food sources for estuarine species. These effects can contribute to a decline in the number of species that use estuaries as habitat, nursery grounds or both.

Measures to achieve objective

• Dredging beyond the minimum needed to maintain navigation channels should be subject to environmental assessment before being allowed to proceed.
• Minimise draining or disturbance of areas of potential acid sulfate soils.
• Protect fish habitats-such as protected areas, seagrass beds and mangroves-from pollution and increased sedimentation or erosion. Polluted sites should be rehabilitated.
• Ensure that water-based activities have minimal impact on fish habitat.
• Deal with other processes affecting (or potentially affecting) estuary health-e.g. the impact of increasing urbanisation.

Supporting information

• Dredging or drainage could expose acid sulfate soils. As treatment of acid sulfate soils is expensive and relatively untested, the priority is to minimise exposure of these soils.
• Sedimentation is a problem in most enclosed bays that receive stormwater, and the community frequently calls for dredging. The objectives for dredging need to be clearly established, adequate environmental assessment should be made, and a management plan for the proposal should be 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.
• Marinas and extensive moorings may affect water circulation patterns or aquatic habitats. As a result, acid sulfate soils and contaminated sediments may be exposed, affecting water quality and tidal flows generally.

This page was published 1 May 2006