Macquarie-Castlereagh catchment
Legend
Ramsar site
DIWA site
| Security | Registered entitlements (ML) |
|---|---|
| High | |
| General | 93,703 |
| Supplementary | 1,888 |
| Total | 95,591 |
* Macquarie/Cudgegong
Environmental watering in the catchment in 2011-12
Environmental watering in the catchment in previous years
In 2010-11, over 900 gigalitres (GL) of water from significant rainfall reached the Macquarie Marshes. This water filled the Macquarie Marshes for the first time in over a decade and inundated 175,000 hectares. As a result of the water flows, over 100,000 pairs of colonial nesting water birds bred in 12 colonies during the year.
A combination of 25 GL of Commonwealth environmental water and 110 GL of environmental water from the NSW government was delivered in March and April 2011 to the Macquarie Marshes. This watering action contributed to the completion of the significant waterbird breeding event and supported the continued ecological function of a wide range of vegetation communities including river red gums.
For further information about Commonwealth environmental watering in the Macquarie-Castlereagh and the outcomes achieved, please refer to the Commonwealth environmental water Outcomes Reports and Annual Reports.
Catchment profile
Where is it?
The Macquarie-Castlereagh catchment is situated in central western NSW and is based around the Castlereagh, Macquarie and Bogan River valleys. The catchment rises near Oberon on the western side of the Great Dividing Range and flowing to the Barwon River near Carinda. The catchment is flanked by the Barwon-Darling catchment to the north and west, the Lachlan to the south and the Namoi to the north.
The Macquarie-Castlereagh catchment covers 91,985km2 (or 8.8 per cent of the MDB area) and contains two major storages, Windamere Dam (capacity 368 GL) on the Cudgegong River and Burrendong Dam (capacity 1,188 GL) on the Macquarie. There are several distributary rivers and creeks that enter the Macquarie river, including Bell, Little and Talbragar Rivers. The landscape of the Macquarie-Castlereagh region varies markedly from east to west and grades from the headwaters (or tablelands) to plains in the west. The Ramsar-listed Macquarie Marshes are located in the far west of the catchment. Since the construction of the Burrendong Dam in 1967, the Macquarie Marshes have declined significantly in health, as it has caused a significant change to natural water flows in the system and specifically to the Marshes.
The Macquarie Marshes during a flooding event
Photo: D Eastburn
What makes this place so special?
The Macquarie-Castlereagh catchment is an ecologically significant area because it includes:
- wetlands of international significance listed under the Ramsar Convention
- other flow-dependent assets including the Macquarie River channel, the Lower Macquarie River, and the Effluent Creeks (e.g. Marra Creek, Crooked Creek and Duck Creek) on the western side of the Marshes
- a diverse range of vegetation including river red gum forest and woodland, black box woodland and lignum
- migratory bird habitats
- wetlands of international significance listed under the Ramsar Convention
The region contains one of the largest and most important wetlands in the Murray-Darling Basin, the Macquarie Marshes. Approximately 200,000 hectares of the Marshes have been listed as nationally important in the Directory of Important Wetlands in Australia (DIWA), while some 18,700 hectares of the Macquarie Marshes has also been listed under the Ramsar convention. The Ramsar listing consists of three separate reserve areas: the Northern Marsh, Southern Marsh and Eastern Marsh.
The Macquarie Marshes contain a wide range of vegetation types, determined by the frequency and duration of flooding. These include river red gum woodland, water couch grasslands, extensive beds of common reed, coolabah, black box, lignum, reed swamp, cumbungi and river cooba.
The range of vegetation found throughout the wetlands provides habitat for many species including 211 bird species (including four waterbird species listed as threatened in NSW), eight species of native mammal, 15 frog species, 56 reptile species and 24 native fish species. Seventeen waterbird species of the Marshes, including the black-tailed godwit and fork-tailed swift, are listed on the JAMBA, CAMBA and/or RoKAMBA international migratory bird agreements.
What does the latest science say about the ecological health of the catchment?
The Murray-Darling Basin Commission Sustainable Rivers Audit (SRA) study used several criteria to rate the overall health of river ecosystems in the Murray-Darling Basin. The SRA reports the Macquarie Valley River as being in very poor health.
The CSIRO Sustainable Yields Report on the Macquarie Valley Catchment indicated that the current level of surface water extraction in the Macquarie valley (excluding the Castlereagh and Bogan Rivers) is moderately high, with 27 per cent of average available water being diverted for use.
While the upper reaches of the Bogan and Castlereagh Rivers are largely unregulated, the Macquarie River is highly regulated. River regulation and water extraction has had substantial effects on flow regimes, with changes to seasonal flow patterns, reduced variability and changes to flood intensity. The average period between significant flood events for the Macquarie Marshes has increased by 114 per cent. The average volume of these floods has also been reduced.
The average period between large flood events for the Macquarie Marshes has increased by 114 per cent. The average volume of these large floods has also been reduced.
Under the best estimate 2030 climate conditions, average surface water availability would be reduced by 8 per cent and end-of-system flows would be reduced by 9 per cent.
It should be noted that the boundaries of this catchment as defined by the Sustainable Yields report differ slightly to the area defined at the top of this page.