- Bioregional Assessment Program
- Namoi subregion
- 1.1 Context statement for the Namoi subregion
The context statement brings together what was known about the geography, geology, hydrology and ecology of the Namoi subregion as at June 2014.
The Namoi subregion spans an area of approximately 29,300 square kilometres. It includes the regional towns of Gunnedah, Narrabri, Quirindi, Walgett, Werris Creek and Wee Waa in New South Wales. The landscape is dominated by highlands in the east and south and a broad floodplain in the west.
The population of the subregion is estimated to be about 27,000 people concentrated along the Namoi River between Gunnedah and Narrabri. The river basin is home to the Indigenous communities of the Gomeroi people.
About 80% of the subregion is used for agricultural production and forestry.
The Namoi subregion has two distinct geological basins, the Gunnedah Basin and the Surat Basin. These basins are sedimentary in origin forming in the Paleozoic and Mesozoic eras, from approximately 80 to 300 million years ago. The Gunnedah Basin overlies the Lachlan Fold Belt, a zone of sedimentary rocks formed some 300 to 450 million years ago.
The Gunnedah Basin is the principal geological domain for this subregion as it contains coal-bearing sequences, which are the focus of current coal seam gas and coal mining development.
Surface water and groundwater
The main surface water resource of the Namoi subregion is the Namoi river basin which includes the Namoi, Peel and Manilla rivers. The subregion is bounded by the Great Dividing Range in the east, the Liverpool and Warrumbungle ranges in the south, and the Nandewar Range and Mount Kaputar in the north. Lake Goran is the largest inland water body in the subregion.
The average annual rainfall ranges from more than 1100 millimetres east of the subregion to less than 500 millimetres west of Walgett. Groundwater resources in the Namoi subregion are the most intensively developed in New South Wales and the subregion has one of the highest levels of groundwater extraction within the Murray–Darling Basin. Due to over-extraction, in 2006–07 parts of the subregion recorded their lowest groundwater levels on record.
The environment of the Namoi subregion has been altered considerably since European settlement. Despite significant land use changes, many ecologically significant habitats remain in the subregion with approximately 3200 square kilometres of native woodlands and forests protected in national parks and nature reserves.
The Namoi river basin also contains a wide range of aquatic habitats including the endangered Darling River ecological community downstream of Narrabri.
The subregion is home to 152 threatened species listed under New South Wales or Commonwealth legislation.
Within the broader Namoi river basin there are approximately 2770 wetlands, totalling 46,398 hectares, including Lake Goran, a wetland of national importance, covering more than 60 square kilometres and providing habitat for large numbers of waterbirds.
- 1.1.1 Bioregion
- 1.1.2 Geography
- 1.1.3 Geology
- 1.1.4 Hydrogeology and groundwater quality
- 1.1.5 Surface water hydrology and water quality
- 1.1.6 Surface water – groundwater interactions
- 1.1.7 Ecology
- Contributors to the Technical Programme
- About this technical product