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).
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.
Black winged stilts in the Gwydir wetlands. Photo: Bruce Campbell, CEWO
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 nationally significant 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. Other significant environmental assets in the catchment include the Mallowa Wetlands, Gwydir River channel and the distributaries including the Mehi River and Carole and Moomin Creeks.
Four discrete wetland areas form the Gwydir Wetlands Ramsar site, covering 823 ha in total on the Gingham and Lower Gwydir (Big Leather) watercourses. These wetlands provide a typical example of an inland terminal wetland delta system. The largest stand of marsh club-rush in NSW (listed as a critically endangered ecological community), can be found on the Gingham Watercourse and covers some 1300 hectares.