Gwydir catchment
Legend
Ramsar site
DIWA site
| Security | Registered entitlements (ML) |
|---|---|
| High | 375 |
| General | 89,525 |
| Supplementary | 19,100 |
| Total | 109,000 |
Environmental watering in the catchment in 2011-12
Environmental watering in the catchment in previous years
During 2010-11, the Gwydir catchment experienced relatively more moderate flows compared to other parts of the Basin. Whilst inflows were not as high as other parts of the Basin some parts of the Gwydir wetlands were inundated from rainfall for the first time in over a decade.
The goal for use of Commonwealth environmental water in 2010-11 was to support six to eight months of continuous wetland inundation across a large portion of the Gwydir wetlands to promote the recovery of wetland vegetation and create habitat for threatened and migratory species.
A total of 13 gigalitres of Commonwealth environmental water was delivered in August 2010 and February- March 2011, to help achieve the objective for the Gwydir wetlands.
For further information about Commonwealth environmental watering in the Gwydir and the outcomes achieved, please refer to the Commonwealth environmental water Outcomes Reports and Annual Reports.
Catchment profile
Where is it?
The Gwydir catchment is in north-eastern New South Wales and is based around the Gwydir River. The catchment is bordered to the north by the Border Rivers, to the south by the Namoi River, to the east by the Great Dividing Range, and to the west by the Barwon River (a tributary of the Darling).
Semi-permanent wetlands develop as floodwaters flow through natural channels and swamps in the Gwydir
Photo: D Albertson DECC
The Gwydir catchment covers 28,998 km2, which represents 2.78 per cent of the total area of the MDB. The river flows in a westerly direction from its headwaters in the Great Dividing Range near Armidale. The region's topography spans from tablelands in the east, through the central slopes to the western plains where the Ramsar-listed Gwydir Wetlands are located. The main tributary of the Gwydir is the Horton River. Downstream of the catchment's largest town, Moree, the Gwydir River breaks into two major streams: the Gingham Watercourse (northern arm) and the Lower Gwydir or Big Leather Watercourse (southern arm). The Gwydir River is regulated by the Copeton Dam which stores water for towns, stock, domestic use and irrigation. There are also many farm dams and ring tanks in the region.
Semi-permanent wetlands in the Gwydir include natural channels and swamps. Widespread inundation of the catchment's wetlands occurs primarily from floods originating in the upper catchment.
What makes this place so special?
The Gwydir River catchment is an ecologically significant area because it includes:
- systems or subcatchments considered to have high conservation value, such as the Georges Creek Subcatchment
- wetlands of national significance, including the New England Wetlands
- a diverse range and large areas of flora, include approximately 60,000 ha of wetland vegetation (particularly coolabah woodlands) and one of the largest expanses of water couch in NSW
- an appreciable assemblage of rare, endangered and vulnerable species including the Australian bittern, the silver perch and the painted snipe.
The Gwydir Wetlands, which feature on the floodplain of the lower Gwydir River, cover an area of 102,120 hectares. These are among the most extensive and significant semi-permanent wetlands in north-west New South Wales. Portions of these DIWA-listed wetlands are also listed under the Ramsar Convention: the Lower Gwydir Watercourse and the Gingham Watercourse. The Gwydir Wetlands Ramsar site has four components, covering 823 ha in total. These wetlands provide a typical example of an inland terminal wetland delta system. The Gingham Watercourse is also host to the largest stand of marsh club-rush in NSW (listed as a critically endangered ecological community), which covers some 1300 ha. Other significant assets in the catchment include the Gwydir River channel and the distributaries including Mallowa Wetlands on Mallowa Creek.
What does the latest science say about the ecological health of the catchment?
The Murray-Darling Basin Commission Sustainable Rivers Audit (SRA) used several criteria to rate the overall health of river ecosystems in the Murray-Darling Basin. The SRA reported the overall health of the Gwydir Valley Catchment as being poor.
The CSIRO Sustainable Yields Report on the Gwydir Valley Catchment report was developed for the Gwydir area and it found that the current level of surface water extraction is very high, with 41 per cent of average available water being diverted away from the waterways. This report indicated that the average period between flood events that inundate at least 20 per cent of the Gwydir Wetlands has increased by more than 75 per cent. Ecosystems in the Gwydir Wetlands are adapted to floods, and many species require inundation to trigger breeding events.
Under the best estimate 2030 climate the report found the average surface water availability would be reduced by 10 per cent and flows at the downstream end of the waterway would be reduced by 6 per cent.
Under the best estimate 2030 climate the report found the average surface water availability would be reduced by 10 percent and flows at the bottom end of the waterway would be reduced by 6 per cent.
Note that the boundaries of this catchment as defined by the Sustainable Rivers Audit and the Sustainable Yields report differ slightly to the boundaries used here.