Macquarie-Bogan River
Water Quality and River Flow Objectives
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At a Glance |
This section gives the Water Quality Objectives (WQOs) and the River Flow Objectives (RFOs) for the Macquarie-Bogan River catchment, which should be used to develop plans and actions affecting water quality and river health. Only the priority RFOs are listed in this section, but the remaining objectives still need to be considered when developing flow management plans or dealing with particular local river conditions.
Town water supply subcatchments
The streams in town water supply subcatchments typically feed into a town's water supply storage. In many cases, the catchment may be declared as specially protected to minimise land use effects on water quality.
Map: This category applies to streams running through areas coloured light blue on the map.
Water Quality Objectives
Protection of:
River Flow Objectives
Supporting information
- This category includes Ben Chifley Dam catchment, Fish River water supply scheme catchment and Orange City's dam catchments.
- To ensure long-term achievement of WQOs for drinking water catchments, existing land management programs aimed at maintaining or improving water quality should continue and be reviewed (see DLWC's Ben Chifley Dam Catchment Action Plan, 1998). Programs include efforts to reduce erosion, dryland salinity and the frequency of algal blooms in dams.
- For example, in Ben Chifley Dam catchment, local communities, the Australian National University, DEC and DNR have collaborated to develop a tool to help water quality managers in their decision-making. The project measured the input of nutrients from different parts of the catchment into the reservoir, how they moved within the water storage, and the main factors which stimulate problem algal blooms. Management options can be modelled at different scales to identify where significant pollutants are generated and transported and hence where to target action. This research effort has been combined with practical programs to reduce erosion, dryland salinity and the frequency of algal blooms in dams.
- The Fish River water supply scheme, which supplies Oberon, Wallerawang power station, Lithgow and Katoomba, currently relies on disinfection-only treatment. Objectives in this subcatchment include ensuring good raw water quality so that, after treatment, it is both safe to drink and to use in the power station.
- WQOs applying to other town water supplies include ensuring that water quality is high enough for clarification and disinfection to be effective in the future.
- Local factors include maintaining natural flows from springs (groundwater) and any effects of land management on volumes and times of runoff, particularly in droughts; flow needs of ecosystems and of people within the area; reliability of the town supplies; and needs of ecosystems and of people downstream.
- Protecting freshes and high flows does not currently require action but is essential for town water reliability and ecosystems. Minimising any adverse effects of weirs should continue.
Mainly forested areas
Streams in mainly forested catchments are often valued for their conservation or recreation values. They often have relatively natural flows and water quality. Many are in national parks or state forests.
Map: This category applies to streams running through areas coloured green on the map (state forests, national parks and nature reserves). It also applies to other forested areas if any are defined locally.
Water Quality Objectives
Protection of:
River Flow Objectives
Supporting information
- Where the whole catchment of a stream is naturally vegetated, WQOs and RFOs are generally, though not always, achieved. High-level protection should be given to flows and water quality in these least-affected streams and in other streams with high conservation values. Existing management practices in national parks or other reserves may already aim to achieve this. In some streams, local circumstances restrict achievement of objectives; for example, cattle using streams in state forests may conflict with achieving water quality suitable for swimming.
- Some streams flowing from disturbed vegetation, plantations or regrowth may meet all water quality and flow objectives, but streams below recently disturbed sites may have increased turbidity and downstream sedimentation. Extensive areas of rapidly growing trees may reduce low flows in adjoining streams. Forests with thick groundcover may absorb storm peaks and increase the duration of some flows.
- Some of the state forests and other reserves marked on the map include streams that start in largely cleared land. Water quality and flow patterns through the forests generally reflect any upstream impacts. There may be high public expectations for the water quality in these streams owing to the public accessibility of these areas, particularly for recreation.
- Streams flowing out of naturally vegetated areas, including private forests, can provide clean waters for downstream uses such as homesteads or livestock. These downstream benefits should be defined locally to provide specific protection.
- Native vegetation on stream banks and floodplains can provide good habitats for native fish, other animals and plants. The effective value of these habitats is likely to be limited if the water quality is inadequate or if flow patterns are not sufficiently close to natural to provide correct cues for breeding and to enable the survival of offspring. Returning water quality and flow patterns as close as possible to natural is therefore desirable.
- If a river management committee considers that there are streams outside reserves with high conservation value and to which a high level of protection should apply, it may seek local views and make recommendations to Government.
Waterways affected by urban development
Waterways within urban areas are often substantially modified and generally carry poor-quality stormwater. Local communities are often keen to see these waterways returned to more natural conditions.
Map: These areas are shown in orange or as orange dots on the map.
Water Quality Objectives
Protection of:
River Flow Objectives
Supporting information
- This category includes small creeks running through Bathurst, Orange, Dubbo, Wellington and Mudgee.
- The interim RFOs recognise the impact of urban development and the longer timeframes or higher costs to rehabilitate these streams.
- There is a need to minimise rapid rises by storm runoff in urban waterways.
- Action is needed to reduce water quality impacts from stormwater and sewerage discharges and unsewered villages.
Uncontrolled streams
This category covers uncontrolled waterways that are not in the other categories. Their flow patterns remain largely natural.
Map: Uncontrolled streams are shown as blue lines on the map.
Water Quality Objectives
Protection of:
River Flow Objectives
Supporting information
- This category includes unregulated effluent creeks below Narromine (but not Duck and Gunningbar creeks, which are regulated).
- Towns draw surface water and groundwater for drinking water supplies from these streams and catchments.
- Natural water quality variability of intermittent or ephemeral streams needs to be taken into account when modifying site-specific objectives for aquatic ecosystems.
- Local factors for consideration in sharing river flows in dry seasons and protecting inundation patterns of flood-dependent ecosystems include:
- strong demand for low flows from some streams; for example, Bell River
- occasional reduction of higher flows in some streams, such as Marthaguy Creek
- identified conservation values; for example, native fish in Bogan and Little rivers
- environmental worth and natural inundation patterns of small wetlands, river red gums, and other riparian or floodplain vegetation; for example, effluent creeks.
- Managing groundwater could affect some stream flows or ecosystems in parts of the upper catchment; for example, in the Orange, Molong, Gulgong and upper Talbragar areas. Water tables could rise and threaten ecosystems in aquifers under some irrigation areas. (Local action to limit this is under way.)
- The RFO Minimise effects of weirs and other structures is an important issue throughout the Macquarie-Bogan River catchment. Local factors include the wish to restore native fish populations; and sediment filling natural waterholes, which causes increased dependence of stock and homes on weirs for water supply.
- Programs may be needed to control weeds brought by floodwaters.
Major regulated rivers
These rivers have large dams supplying irrigation water (and usually town and industrial water) for substantial distances downstream. Flows are typically supplemented during the irrigation season, resulting in fairly stable and unnaturally high water levels. River flow is substantially reduced during the non- or low-irrigation seasons. At any time of year in periods which would normally have high or very high flow, flows may be substantially reduced by the trapping of water in a large dam .
Map: These rivers are shown as yellow lines on the map.
Water Quality Objectives
Protection of:
River Flow Objectives
In 1999, no RFOs were recommended by the Government for the Macquarie Cudgegong Regulated River because at that time, the 1996 Macquarie Marshes Water Management Plan contained the environmental flow rules for the regulated streams below Burrendong Dam. In 2002, the former Macquarie-Cudgegong River Management Committee recommended a Water Sharing Plan (WSP) to Government. The Committee considered the River Flow Objectives framework in developing this Plan, as well as regional social and economic factors. The WSP commenced in July 2004.
It includes river flow rules for the Cudgegong River between Windamere and Burrendong dams as well as for the Macquarie regulated river below Burrendong and for the Macquarie Marshes. The Plan provides for an environmental flow reference group to advise the Minister on the management of flows for these rivers and for the Marshes.
Alluvial aquifers adjoin these rivers and their management should consider the interaction with the river. Groundwater levels may affect ecosystems. Action is needed to maintain groundwater within levels critical to ecosystems and to manage other local concerns such as the reliability of bore water supplies for stock and irrigation.
Supporting information
- Major regulated rivers extend from Windamere Dam to Pilligawarrina in the Macquarie Marshes and to the ends of Duck and Gunningbar creeks.
- Drinking water objectives are not currently achieved at some locations. Wellington and Dubbo need to treat their supplies for blue-green algae, at significant community cost.
- The option of stopping flow in Gunningbar and Duck creeks for one to two months in autumn to mimic natural drying was considered, but is not feasible. The local community raised its concerns that any environmental advantages would be outweighed by the negative aspects related to the disruption to town, mine and farm water supplies and the bogging of stock. The Government has therefore decided to exclude this objective from consideration for these creeks.
Controlled rivers with reduced flows
This category covers two cases:
- River reaches downstream of regulated sections, where the released water is extracted or diverted. As a result, the flow is substantially reduced throughout the year (Macquarie River below Pilligawarrina River gauge).
- Sections of rivers immediately below major town water supply dams, where water is diverted directly from the dam (streams below Oberon, Suma Park and Winburndale dams and Bathurst town water supply offtake).
In these cases, flows can be substantially reduced throughout the year, though special environmental releases may be possible. Water quality can be affected by the loss of diluting or flushing flows.
Map: These rivers are shown as red lines on the map.
Water Quality Objectives
Protection of:
River Flow Objectives
All controlled rivers with reduced flows:
Additional objectives for controlled rivers with reduced flow in the Lower Macquarie:
Supporting information
- Flows in much of the Fish River are often substantially reduced by diversion of water to meet urban and power generation needs. A separate Water Sharing Plan is to be developed for the Fish River.
- Flows below Suma Park Dam are reduced by diversions supplying Orange. Landholders downstream depend on the remaining flow and contribute to further reductions. Access rules developed under Macro Water Sharing Plans will contribute toward achieving the RFOs by setting rules for access by water licences to vary low flows.
- Augmentation of town water supplies in the future will require a review of environmental flow releases conditions to contribute to the RFOs.
- Local factors include support for protection of native fish and landholders' needs.
- The lower Macquarie (below Pilligawarrina gauge) is an ecologically significant stream. Upstream dams and irrigation diversions have reduced the flows. Extraction within this reach is significant. This requires appropriate actions to meet RFOs. Actions should take account of local factors, including financial effects; environmental flows delivered under the Macquarie Marshes Water Management Plan; and the important contributions that flows from the Macquarie make to flows in the Barwon River.
Controlled rivers with altered flows
In these rivers, the average volume of flow is close to natural, but patterns of flow are altered by a moderately large dam. Water trapped by the dam is released in a pattern to suit downstream town water demands.
Map: Controlled rivers with altered flow patterns are marked in brown on the map.
Water Quality Objectives
Protection of:
River Flow Objectives
Supporting information
- This category applies only to sections of Campbells and Macquarie rivers used to deliver town water.
- Drinking water is a key environmental value in sections of rivers supplying water to towns from dams; for example, sections of Campbells and Macquarie rivers linking Ben Chifley Dam with Bathurst's drinking water offtake. Bathurst both clarifies and disinfects the supply. It often also needs to treat the water for blue-green algae, at significant community cost.
- The augmentation of Ben Chifley Dam included specification of release rules to achieve selected flow objectives downstream. Rules developed to manage licensed extraction will protect the environmental releases from Ben Chifley and the flow objectives they support. As works are managed to maintain a supply for town water and other essential purposes, pool levels exceed the natural level at times that would naturally have no flow. It is not appropriate to reduce flows to natural levels, so no action to implement RFO Protect pools in dry times or RFO Mimic natural drying in temporary waterways is needed. The dam will continue to reduce the frequency of freshes and high flows in some years. Efficiency improvements in urban water use may avoid further reduction of these flows.
- Extraction for other purposes between Ben Chifley Dam and Bathurst's offtake are managed through access rules in the Macro Water Sharing Plan for this area. These access rules compliment and protect the dam release rules.
Artificial channels
Water is frequently supplied for irrigation or town water supplies through constructed channels. RFOs do not apply to entirely artificial channels, but some WQOs do apply.
Map: Major channels are marked in grey on the map.
Water Quality Objectives
Protection of:
River Flow Objectives
- No RFOs are recomended for artificial watercourses.
- Some channels need to be managed in ways consistent with environmental objectives or rules applying downstream or nearby. The Macquarie Marshes Water Management Plan already provides rules for operation of the Northern Bypass Channel through the marshes.
Supporting information
- This category includes Albert Priest Channel.
- Aquatic ecosystems exist downstream of artificial channels and may also exist in them. The priority is to protect downstream ecosystems. Any future protection of aquatic ecosystems in channels should reflect their modified conditions.
- Human-use values that need to be protected should be recommended on a case-by-case basis. Water quality will need to be consistent with water uses and values within and downstream of these waters.
- Albert Priest Channel is a drinking water supply channel. Water quality at points of supply should meet criteria that enable effective treatment by clarification and disinfection.
This page was published 1 May 2006
About the Objectives
