Gwydir

The Gwydir River begins high in the Great Dividing Range of northern New South Wales and flows westwards through steep valleys and out onto wide plains. The river splits into many anabranches and creeks on the floodplain, where wetlands and swamps soak up much of the flow of the river. During a flood, water flows across the floodplain to the Barwon River.

The Gwydir Wetlands are among the most extensive and significant semi-permanent wetlands in north-west New South Wales. The wetlands include 4 Ramsar listed sites. They provide habitat for a number of rare, endangered and threatened animal and plant species. When flooded, the wetlands support large numbers of waterbirds and host major waterbird-breeding events.

The Gwydir catchment is home to about 1.3% of the population of the Basin. Irrigated cotton production is a major source of income and employment in the region.

Snapshot

Catchment area	Around 2% of the Murray–Darling Basin
Contribution to Basin water	3.4%
Annual stream flow	336 GL (Bundarra – unregulated flow)
River length	480 km
Tributaries	Copes, Moredun, Georges and Laura creeks; Horton River
Distributaries	Mehi River, Carole–Gil Gil creeks, Gingham Watercourse (northern arm) and lower Gwydir or Big Leather Watercourse (southern arm)
Towns include	Moree, Uralla, Guyra, Bingara, Warialda
Water storages	Copeton Dam (1,364 GL)
Water users	Irrigated agriculture, urban water supply, stock and domestic, mining

The landscape and its water

The Gwydir River rises west of Armidale on the New England Tablelands in the Great Dividing Range, New South Wales. The river flows north-west through the steep valleys of the tablelands and down the north-western slopes of New South Wales. The valley widens into an almost completely flat alluvial floodplain near Pallamallawa and flows, where the river flows slowly westward towards the Barwon River.

Downstream of Moree, the Gwydir River diverges at the Gwydir Wetlands into the Gingham Watercourse and the lower Gwydir (or Big Leather) Watercourse. These watercourses flow into the Gwydir wetlands. The lower half of the catchment is characterised by numerous anabranches and effluents, the most significant being the Mehi River and Moomin Creek to the south, and the Carole–Gil Gil Creek system to the north. The latter creek system joins with the southern effluents of the Border Rivers. Several of the branching streams from the Gwydir enter the Barwon River between Collymongle and north of Collarenebri.

The tablelands where the river and its feeding streams rise on the tablelands have an an elevation up to 1,200 metres. Lower but still significant ranges define the catchment, with the Mastermans Range in its north and the Nandewar Range, with remnant volcanoes, in the south. The wide western floodplains that cover much of the catchment have an elevation between 100 and 300 metres.

The eastern half of the catchment has an annual average rainfall of 700–900 mm. Average annual rainfall on the floodplains of the western portion, ranges from 450–550 mm. Rainfall throughout the catchment is summer dominant and the climate is described as sub-humid and sub-tropical.

The major groundwater aquifers in the Gwydir catchment are found in extensive unconsolidated alluvial sediments, associated with rivers and channels in the western half of the catchment. Groundwater is found in fractured rock of several types in the eastern part of the catchment. There is a relatively small seam of porous rock aquifers in the middle of the catchment, which yields water from the Great Artesian Basin lying deep below the catchment.

People, industry and water use

The Gwydir catchment is within the traditional lands of the Gomeroi/Kamilaroi people. The Gomeroi is a large Nation, which extends from around Singleton in the Hunter Valley through to the Warrumbungles in the west, and up through the Namoi and Gwydir valleys to just over the Queensland border.

Europeans started establishing settlements in the region in the 1830s, and by 1848 the Gwydir pastoral district was recognised. Grazing was the main agricultural pursuit and its advance onto the western plains was made possible by the rivers and ready access to artesian groundwater. The establishment of railways made grain production feasible and the region became a key grain producing area in Australia. The development of irrigation has seen the region become a hub for cotton production and processing.

The Gwydir catchment has about 1.3% of the population of the Basin. The town of Moree is the major service centre of the region located on the plains and has a population of about 9,000 people (ABS 2016). The rest of the catchment's residents live in small towns and villages such as Uralla, Guyra, Bingara and Warialda, or in rural localities. In 2006, the most significant employment sector for the region's workforce was agriculture, followed by wholesale and retail trade, education, and health and community services.

Land use is dominated by extensive grazing for cattle and sheep production, with lucerne and pasture grown on the narrow alluvial floodplains of the upper Gwydir River for grazing enterprises. Dryland cropping occurs predominantly on the plains. Wheat is the main crop but a range of other cereals, legumes and oilseeds are also grown. Irrigated crops account for a small amount of land use (about 5%) but are a significant contributor to the regional economy, especially cotton growing and ginning. As of 2008, the Commonwealth Scientific and Industrial Research Organisation (CSIRO) reported on average 41% of available surface water was extracted for use annually, which is high compared with other catchments in the Basin. Water in the catchment is diverted from the river system for irrigation, stock, domestic, and urban use.

Groundwater is generally suitable for irrigation, stock and domestic use throughout the valley, with the exception of small areas in the lower Gwydir catchment where the water is brackish or saline.

Regulation of water in the catchment

The Gwydir River is regulated by a number of weirs, most notable is the Copeton Dam. Before regulation, the lower Gwydir catchment resembled an inland delta, with water inundating the floodplain and wetlands and only flowing through to the Barwon River in major floods. Regulation of the river system has caused a significant reduction in moderate to high flows in the lower Gwydir River. It has also contributed to an increase in the average period between large flows. However, regulation and irrigation supply have resulted in more frequent low flows to the river system and more water flowing through regulated waterways to the Barwon River.

Copeton Dam, 35 kilometres (km) south-west of Inverell, was built to supply water for town water supplies, irrigation, stock and domestic requirements. Completed in 1976, the dam regulates 93% of inflows of the catchment. An upgrade of the dam was completed in 2013, however storage capacity remains at 1,364 gigalitres (GL). Power is generated at the dam when water is released for water users, the environment or for flood management.

A series of weirs and regulators assist the diversion of water to the various watercourses of the lower Gwydir catchment. The first of these is Tareelaroi Weir, about 30 km upstream and 18 km east of Moree, which controls diversions to the Mehi River. Five other major structures are located on the Gwydir River downstream of Moree or on the Mehi River and Mallowa Creek, south-west of Moree.

Environmental importance

The Gwydir catchment supports a wide range of ecosystems, from high altitude forests in the east of the catchment, to open forest and woodlands on the slopes, to scrublands and grasslands on the floodplains. Much of the natural environment is fragmented due to agricultural development.

The floodplains of the Gwydir region include large expanses of wetland vegetation supported by natural channels, semi-permanent wetlands and swamps that have a high conservation value, and are of national and international significance. Widespread inundation of the catchment's wetlands depends primarily on floodwaters originating in the upper catchment. The nationally significant Gwydir Wetlands on the floodplain of the lower Gwydir River cover an area of over 100,000 hectares. These are among the most extensive and significant semi-permanent wetlands in northern-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.

There are 4 discrete wetland areas which form the Gwydir Wetlands, covering some around 800 hectares on the Gingham and Lower Gwydir (Big Leather) watercourses. These wetlands provide are an typical example of an inland terminal wetland delta system, particularly coolabah woodlands, and host the largest stand of marsh club-rush in New South Wales (listed as a critically endangered ecological community). The site is also important for waterbird breeding, fish breeding and as a habitat for native mammals. The wetlands have many archaeological sites of cultural significance to the Kamilaroi people.

The Sustainable Rivers Audit 2 (2012) reported the overall ecosystem health of the Gwydir River valley was poor. The health of the fish community was rated poor, with fewer than expected native species present and an active build-up of alien species. The macroinvertebrate community was rated in moderate condition overall, though the lowland zone was rated poor. Riverine vegetation was rated in moderate condition throughout the valley. The physical form of the river was rated in moderate condition. The overall hydrology of the river system was rated poor, with zone ratings ranging from very poor in the lowland areas to good in the montane eastern mountain areas. The volume and variability of flow in the main-stem river reaches were very different to a reference condition (based on minimal human intervention having occurred) as a result of regulation.

Water recovery

The Basin Plan sets Sustainable Diversion Limits, which is how much water can be used in the Murray–Darling Basin, while leaving enough water for the environment. A Sustainable Diversion Limit (SDL) was established for each catchment (or group of catchments) and the reduction in diversions required to achieve the SDL was identified.

The use of environmental water in a specific catchment or region will vary from year-to-year. The Murray–Darling Basin (MDBA) has a Basin-wide environmental watering strategy to guide the use of environmental water across the Murray–Darling Basin to help achieve the best possible results over the long term. Environmental water managers make the day-to-day decisions on what to water and when, in line with the strategy and taking into account seasonal conditions, priorities and the availability of environmental water. Watering decisions are made in consultation with various waterway managers and local landholders.

Catchment or regionally-specific details about environmental water use in the catchment including watering actions, portfolio details and planning, and monitoring of environmental watering, can be found through the Commonwealth Environmental Water Holder or the state government environmental water manager.

More information

Water management

The management of water resources is the responsibility of local, regional, state and Australian governments.

Delivery to households, industry and farms is managed by local councils or regional water authorities.

State government departments for water ensure the network of authorities manages water responsibly and fairly, that catchment and waterway health is maintained or improved through catchment management authorities, and that water saving, re-use and flood management projects are implemented. State governments must manage their state's water resources according to state and commonwealth water legislation.

In addition to directing operations of the regulated River Murray system, the MDBA implements a number of plans and programs to ensure the waters of the Basin, which flow through four states and one territory, are managed cohesively and in the best interests of all water users of the Basin.

Rural water authority