Lachlan 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 Lachlan 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 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 Lake Rowlands on Coombing Creek and Lake Endeavour on Billabong Creek.
- To ensure long-term achievement of the WQOs, existing land-management programs aimed at maintaining or improving drinking water quality should continue and be reviewed. These programs include efforts to reduce erosion in the catchments, the frequency of algal blooms in the dams, and other pollutant sources that limit drinking water quality. Raw water sourced from these catchments will need to be of high enough quality for available treatment to be effective.
- Not all parts of large river systems can be protected from human activities that degrade drinking water quality. See 'Uncontrolled streams' and other categories, below, for objectives that apply to drinking water offtakes.
- Local factors to be considered include the effects of land management on volumes and times of runoff, particularly in droughts; flow needs of ecosystems and people within the area and downstream; and reliability of town supplies.
Mainly forested areas
Streams in mainly forested areas are often valued for their conservation or recreational values. They often have relatively natural flows and water quality. Many are in national parks or state forests. Others are generally in the upper parts of catchments.
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
- In some cases, this river type will have agricultural land uses along the upstream section of the river (see 'Uncontrolled streams', below). In these cases, management will be needed to achieve the WQOs and RFOs. In forested upper catchment areas, drinking water (with treatment) may be a desired objective and requires very good water quality, particularly with regard to turbidity and pathogens (disease-causing organisms). In extensive private forests, livestock and homestead water supplies may be desired uses, in which case they should be included as local objectives.
- In upper catchment forested areas, the flow regime will be substantially natural and should be protected. Lower in the catchment, forested areas may have a flow regime highly altered by upstream uses. These lower areas should be a priority for remedial action.
- The extensive areas of natural vegetation that are not in state forests or national parks should be identified so that their contribution to water quality can be recognised.
Waterways affected by urban development
Waterways within urban areas are frequently 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 minor creeks within towns such as Blayney, Canowindra, Condobolin, Cowra, Forbes, Parkes, West Wyalong and Young.
- Flows have been modified by increased runoff owing to hard-surfacing of the urban area. Affected creeks and wetlands (for example Lake Forbes) will flood to higher levels and may be wetter than natural.
- 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 ecosystems.
Waterways affected by irrigation drainage
These are often natural watercourses whose flow is now dominated for substantial periods by irrigation drainage. Flow and water quality are therefore unnatural.
Map: These waterways are shown as green lines on the map.
Water Quality Objectives
Protection of:
Other objectives may be needed to meet water uses within these systems and downstream.
River Flow Objectives
Supporting information
- This category includes Nerang Cowal, Bogandillon Swamp, and the creek between them, and Mirrool Creek.
- Irrigation drainage is often saline and contains increased amounts of nutrients and pesticides.
- There is no formal drainage scheme from the irrigation district west of Jemalong Weir, but irrigation runoff does enter floodways and wetlands and can be flushed into creeks, lakes Cowal and Nerang, and Bogandillon Swamp. Saline groundwater levels are also rising in this area.
- Mirrool Creek receives irrigation drainage from the Murrumbidgee irrigation schemes.
Uncontrolled streams
This category covers uncontrolled waterways that are not in the other categories. Their flow patterns are largely natural.
Map: These streams are shown as blue lines on the map.
Water Quality Objectives
Protection of:
River Flow Objectives
Supporting information
- Most rivers in the Lachlan River catchment fall into this category. Available water quality data indicate that the water quality is often inadequate to support some of the current uses and desired objectives, particularly swimming (primary contact recreation), and irrigation of moderately salt-tolerant crops.
- Drinking water is taken from several offtake points on uncontrolled streams; for example, Boorowa (river offtake) and Gunning (bores). Special zones for protection of water quality may need to be designated upstream of drinking water offtakes or around recharge areas for borefields.
- Lake Cowal is a significant wetland area and receives water from Bland Creek (uncontrolled) and the Lachlan (regulated). Irrigation drainage and rising saline groundwater may affect the water quality of Lake Cowal and its value as a wetland. Similarly, changes to the flooding regime would have a significant impact.
- Developments such as the Cadia and Lake Cowal mines will need to be managed effectively to minimise effects of changes in water quality and flows.
- Protecting the water levels in the river in dry times is particularly important for aquatic animals.
- Dryland salinity is a major problem in the Upper Lachlan River catchment, particularly in the Boorowa area. A contingency allocation is stored in Wyangala Dam for release if levels of salinity affect human uses of water downstream.
- RFO Minimise effects of weirs and other structures is important throughout the catchment. Local factors include the wish to restore native fish populations; and the filling of natural waterholes by sediment, which causes increased dependence on weirs to secure stock and domestic supplies.
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 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
No RFOs were recommended in 1999 as flow rules were in place. A Water Sharing Plan has been in place since 2004.
Supporting information
- These rivers include the Lachlan between Wyangala Dam and Oxley; Belubula River below Carcoar Dam; and several anabranches around Condobolin.
- A Water Sharing Plan for the Lachlan Regulated River was gazetted in 2004.
- Achieving drinking water objectives for these streams will mean that the water drawn from the river or groundwater at the point of supply is of adequate quality in the long term for the available level of treatment to be effective. Towns on the major regulated rivers that extract water from streams or bores for drinking water include Cowra, Forbes, Condobolin (river), Lake Cargelligo (lake supplied from river) and Hillston (bores).
- Secondary contact recreation was not specifically requested during community consultation, but if the water quality is good enough for swimming, it is also safe for boating and wading.
- Recent water quality data indicate that turbidity and nutrient levels are often too high; salinity is generally lowered by water releases from storage but can be a problem during low flows. Water released from Lake Brewster can increase turbidity in the Lower Lachlan during low flows. The water quality of Carcoar Dam is often poor, due largely to blue-green algae; and releases from Wyangala Dam are usually colder than natural.
- All RFOs and WQOs should be considered when the WSP is reviewed by the NRC and if a new WSP is developed.
- In particular, there needs to be a focus on how the WSP could address any RFOs not addressed by the existing WSP, whilst protecting licence holders security consistent with the National Water Initiative.
- The river section below Hillston has substantially modified flows-the frequency and duration of freshes and small floods are reduced and summer flows are more persistent than under natural conditions. This section of the river is included in this category because it is covered by the flow rules.
- Dryland salinity is a major problem in the upper catchment, particularly in the Boorowa area. A contingency allocation is stored within Wyangala Dam for release if levels of salinity affect human uses of water downstream.
- Alluvial aquifers adjoining these rivers need to be managed in association with the rivers. Groundwater levels may affect ecosystems. Action is needed to maintain groundwater within levels critical to ecosystems and streamflows and to deal with other local concerns such as the reliability of bore water supplies for stock.
Controlled rivers with reduced flows-Willandra Creek system
This category covers river reaches downstream of the regulated sections, where the released water is extracted or diverted. In these cases, flows can be substantially reduced throughout the year, though special environmental releases may be possible. These rivers often have persistent low flows. 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
Supporting information
- Water quality can be affected by the loss of diluting or flushing flows, where flows have been reduced, and by the release of stored water (for instance, from Lake Brewster).
- Drinking water quality is a key value to protect in the sections of river supplying water to towns, such as the water supply for Ivanhoe.
- The upstream part of Willandra Creek is also a 'regulated river' but here has been included as a separate category.
- The Willandra Creek system suffers from persistent low flows (due to releases for stock and domestic flows). This means that the RFO Mimic natural drying in temporary waterways is a priority. Restricting the frequency of stock and domestic flows, however, can impose some difficulties on dependent communities, and requires sensitive management and an informed community. To some extent, releases for unforeseen events can compensate for the amount of water extracted upstream, but protecting natural flows from extraction would give extra environmental benefits.
Controlled rivers with reduced flows-Muggabah, Merrimajeel, Merrowie and other creeks in the Booligal region
This category covers river reaches downstream of the regulated sections, where the released water is extracted or diverted. In these cases, flows can be substantially reduced throughout the year, though special environmental releases may be possible. These rivers often have persistent low flows. 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
Supporting information
- Water quality can be affected by the loss of diluting or flushing flows where flows have been reduced, and by the release of stored water (for instance, from Lake Brewster). The downstream ends of these systems are likely to be particularly susceptible to accumulating pollutants such as salts.
- The creek and wetland systems suffer from a reduction of medium to higher flows, and levees that affect inundation. This means that RFO Maintain wetland and floodplain inundation is a priority. Restricting the frequency of stock and domestic flows can impose some difficulties on the dependent communities and requires sensitive management and an informed community. To some extent, releases for unforeseen events can compensate for the amount of water extracted upstream, but protecting natural flows from extraction would give extra environmental benefits.
Controlled rivers with reduced flows-Great Cumbung Swamp
This category covers river reaches downstream of the regulated sections, where the released water is extracted or diverted. In these cases, flows can be substantially reduced throughout the year, though special environmental releases may be possible. These rivers often have persistent low flows. 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
Supporting information
- As the terminal wetland in the Lachlan system except at times of extremely high flows, the Great Cumbung Swamp is particularly susceptible to persistent pollutants such as salts.
- The wetland system receives persistent low flows (the 'left-overs' from releases), and suffers from a reduction of medium to higher flows, and levees that affect inundation. This means that RFOs Protect important rises in water levels, Maintain wetland and floodplain inundation and Mimic natural drying in temporary waterways are priorities. To some extent, releases for unforeseen events can compensate for the amount of water extracted upstream, but protecting natural flows from extraction would give extra environmental benefits.
Controlled rivers with altered flow patterns
In these rivers, the average volume of flow is close to natural, but patterns of flow are altered. Water is released in a pattern to suit downstream stock and domestic demands.
Map: These rivers are marked in brown on the map.
Water Quality Objectives
Protection of:
River Flow Objectives
Supporting information
- This category includes an anabranch north of Lake Cargelligo.
- Restricting the frequency of flows for stock and domestic use can impose some difficulties on dependent communities and requires sensitive management and an informed community.
Artificial channels
This applies to entirely artificial watercourses constructed to supply water for irrigation or other purposes.
Map: Channels are marked in grey on the map.
Water Quality Objectives
Protection of:
River Flow Objectives
No RFOs are recommended for artificial watercourses.
Supporting information
- This category includes the major artificial channel that supplies the Jemalong area.
- River management plans should recommend the human-use values to be protected on a case-by-case basis. Water quality must meet the needs of water uses and values within and downstream of these waters.
- The Growlin Scheme, Jemalong Irrigation Ltd, Klagarthur Station, Lampe Citrus, T A Fields, Twynam "Merrowie" and ICM Agriculture all have channels; Jemalong is the major scheme diverting water.
This page was published 1 May 2006
About the Objectives
