Castlereagh 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 Castlereagh 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
Streams within these subcatchments feed into a town water supply storage. In some cases the catchment may be declared specially protected to minimise the effects of land use 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 the small weir from which Coonabarabran draws part of its water supply and Timor Dam, within the same catchment area.
- Timor Dam has experienced algal problems in recent years.
- Raw water sourced from these subcatchments will need to be of high enough quality in the long term for available treatment to be effective. The Australian Drinking Water Guidelines (NHMRC & NRMMC 2004) is an important reference.
- Local factors to be considered in determining how best to meet the RFOs Protect pools in dry times, Protect natural low flows and Manage groundwater for ecosystems include:
- maintaining natural flows from springs (groundwater)
- flow needs of ecosystems and people within the area
- reliability of the Coonabarabran's town water supplies
- needs of ecosystems and people downstream, recognising that the reach of the Castlereagh immediately below the Coonabarabran water offtake weir has been classified as stressed; and
- managing any effects of land use on volumes and times of runoff, particularly in droughts.
- RFO Protect important rises in water levels in streams feeding into these storages is essential for ecosystems and town water reliability. This objective is not listed for action as it is currently being achieved.
- Management of Timor Dam and efficiency of water use within Coonabarabran could be reviewed to assess whether any changes can be made to better achieve these flow objectives without reducing the reliability of the town water supply.
- Not all parts of large river systems can be protected from human activity. See 'Uncontrolled streams' and other river categories, below, for objectives that apply to drinking water offtakes in other parts of the catchment.
Mainly forested areas
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Streams in mainly forested areas are often valued for their conservation or recreational values. They usually have relatively natural flows and water quality.
Map: This category includes state forests, national parks and nature reserves, coloured green on the map. Also applies to other areas of natural vegetation if any are defined locally.
Water Quality Objectives
Protection of:
River Flow Objectives
All RFOs apply and most if not all objectives are currently being met. Priority action is unlikely to be necessary in relation to any flow objectives.
Supporting information
- Where the whole catchment of a stream is naturally vegetated (e.g. in Warrumbungle National Park), WQOs and RFOs are generally 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, the use of streams in state forests by cattle conflicts with the achievement of water quality suitable for swimming.
- Some streams flowing from recently disturbed forest sites may have increased turbidity and downstream sedimentation. Thick groundcover may absorb storm peaks and increase the duration of some flows.
- Waters flowing out of naturally vegetated areas can provide clean water for downstream use by homesteads or livestock. These downstream benefits may be defined locally for specific protection.
- Aboriginal people have identified the consumption of raw aquatic foods as an existing use within the catchment. NSW Health recommends against the consumption of raw shellfish harvested on a non-commercial basis and local communities should be made aware of the risks involved.
- If the catchment management authority or local councils consider that a high level of protection should apply to streams with a high conservation value outside reserves, they may seek local views and make recommendations to the 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 as orange dots on the map.
Water Quality Objectives
Protection of:
River Flow Objectives
Supporting information
- This category includes creeks and minor waterways within towns such as Coonabarabran, Gilgandra, Mendooran and Coonamble.
- In some urban waterways, aquatic ecosystems are considerably modified. A return to pristine aquatic ecosystems in these areas is unlikely and impractical, but water quality conditions for existing ecosystems can be improved greatly for the benefit of local species and broader catchment health. Data from other local aquatic ecosystems of similar type, in areas that are not urbanised, may provide achievable criteria for these modified aquatic ecosystems.
- Action is needed to reduce or avoid the effects of surface and groundwater quality from stormwater and sewage discharges and unsewered villages.
- The Best-Practice Management of
Water Supply and Sewerage Guidelines (DEUS 2004) helps councils in providing and managing drainage in a way that will achieve sustainable outcomes.
- The tendency for urban development to cause rapid rises in storm runoff should be minimised by promoting water sensitive urban design when new developments occur in larger towns, such as Coonabarabran.
- See supporting information under 'Uncontrolled streams', below.
Uncontrolled streams
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This category applies to all streams, wetlands and natural watercourses that are not in the other categories.
Map: Uncontrolled streams are shown as blue lines on the map.
Water Quality Objectives
Protection of:
River Flow Objectives
For wetlands, high-flow channels, remnant floodplain vegetation and adjoining lands and watercourses, the following objectives also apply:
For groundwater areas that sometimes feed into streams, or are naturally shallow enough to supply trees, or have rising water tables:
Supporting information
- This category includes much of the Castlereagh River, most streams flowing into the Castlereagh, and those carrying high flows away from it and to wetlands on the floodplains.
- Some upper-catchment river sections drain through limestone outcrops, resulting in relatively hard water and elevated salinity. Sandy streambeds and subsurface flows are characteristic of a long reach of the Lower Castlereagh River. When establishing locally applicable water quality and flow benchmarks and defining river health, these and other local characteristics will need to be accounted for.
- Monitoring data from other western streams in north-west NSW suggest that water quality in these rivers sometimes fails the criteria for primary contact recreation. Human sources of bacteria, such as sewerage and septic systems, and animal sources were identified, pointing to problems throughout the catchments studied.
- For drinking water needs, many places in the Castlereagh River catchment, such as Gilgandra, Coonamble and Mendooran, rely on pumping groundwater. Water taken at point of supply must be of adequate quality in the long term for the available level of treatment to be effective.
- Local factors to be considered in sharing stream flows, particularly in dry seasons, include:
- interactions between flow and water quality
- downstream human and environmental needs for water
- current limits on the ability of towns, riparian landholders and enterprises to survive for periods without needing to use water from streams, and any viable options for improving this ability
- the continued survival of an uncommon native fish species, the River Blackfish, in some of these streams
- the value of pools to aquatic species that need surface water lasting a minimum period in order to reproduce successfully. For example, most frog species need about 10 weeks for tadpoles to mature in warm water, longer in cool water.
- the water flows under sand in some streams, but extraction of this water may affect ecosystems or delay restoration of flows downstream after small storms.
- The RFO Minimise adverse effects of weirs is an important issue. For example, if fish passage at the bottom end of the Castlereagh was improved, fish could move between the Barwon River and over 300 kilometres of habitat whenever the Castlereagh was flowing.
- Priority objectives for protecting inundation patterns of flood-dependent ecosystems are largely being met, but some action may be appropriate in some of the wetlands and high-flow channels near the lower reaches of the Castlereagh River and Mowlma Creek. Local and scientific views should be considered in relation to social, economic and conservation values in determining what, if any, action is needed. Within this catchment, wetlands are a scarce but valuable resource. The remaining areas of natural floodplain ecosystems, including wetlands and riparian vegetation, are less affected by upstream diversions and intensive irrigation than floodplain ecosystems of many other rivers. They therefore have high economic and conservation values at both local and state levels.
- In relation to RFO Manage groundwater for ecosystems, the river and groundwater management committees will need to confer to identify areas where streamflow or ecosystems could be affected by changes in groundwater levels. In basaltic areas there are aquifers supplying springs on which ecosystems and streamflow may depend. In sandy parts of this catchment there are shallow aquifers so closely connected to the river that lowering of groundwater levels could sometimes affect river flows. River red gum woodlands and populations of some aquatic organisms could be affected by prolonged lowering of the watertable. Grazing properties and some towns also depend on these shallow aquifers, and some people use them for irrigation. There are other areas in the upper catchment where dryland salinity could threaten ecosystems, agriculture or water quality if groundwater rises.
Controlled rivers with reduced flows
A significant proportion of the flow in this river is diverted in dry to normal seasons. Water is diverted upstream of this reach to supply Coonabarabran, and directly from this reach to meet irrigation, stock and domestic needs.
Map: These rivers are shown as red lines on the map.
Water Quality Objectives
Protection of:
River Flow Objectives
Supporting information
- This category applies to the Castlereagh River between Coonabarabran and Greenbah Creek.
- Water quality issues to consider include upstream inputs of agricultural chemicals entering waters, and urban effects from Coonabarabran including discharge of treated sewage effluent. Stability of river banks should be dealt with in conjunction with the proliferation of willows, management of stock access to waters and weed control.
- Water quality can be affected by the loss of diluting or flushing flows where flows have been reduced.
- Trapping and diversion of naturally varying flows, constant release of smaller volumes of effluent, and substantial changes to the riverbank environment have contributed to identification of this reach of the river as stressed.
- Most of the local considerations discussed above under 'Uncontrolled streams' also apply to this reach of the river. Greater effort may be needed to achieve objectives and targets in this part of the catchment owing to current impacts on river flow and water quality.
This page was published 1 May 2006
About the Objectives
