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Commonwealth environmental water in the Warrego catchment
Options for Commonwealth environmental water use in 2012-13
Annual Water Use Options 2012-13: Northern Murray-Darling Basin Unregulated Rivers identifies potential Commonwealth environmental watering actions for 2012-13.
Annual Water Use Options 2012-13: Northern Basin Unregulated Rivers – Fact Sheet summarises the approach and some of the options for using Commonwealth environmental water, as well as identifies how anyone may provide suggestions for use of environmental water.
Environmental watering in the catchment in 2011-12
During 2011-12, 34 gigalitres of environmental water was taken in the Warrego:
- to support natural flow events in the upper Warrego system including a flow that was the first in the season to reconnect waterholes in the upper and middle reaches and provide a cue for the migration and spawning of native fish;
- to support natural flow events in the lower Warrego including the first inflow connecting the main river to the nationally significant waterbird breeding and feeding habitat in the Cuttaburra Basin;
- to provide flows from the New South Wales lower Warrego at Toorale downstream towards the Darling; and
- to inundate the Western Floodplain of Toorale Station to continue restoration of waterbird habitat and floodplain vegetation communities.
Environmental watering in the catchment in previous years
The Warrego catchment received above average rainfall during summer 2010-11. Summer streamflow at Cunnamulla in the mid-catchment was the third highest by volume in the last 20 years. The large summer events connected waterholes in the upper and middle reaches and provided beneficial flows to the nationally significant lower Warrego distributary system and Yantabulla Swamp.
A total of 16 gigalitres (GL) of Commonwealth environmental water was delivered within the Warrego catchment during the year. Since 2009, more than 32.6 GL of Commonwealth environmental water has been used to complement natural flows in the Warrego and Nebine catchments. This water made a small but valuable contribution to the ecological benefits of flow events in these systems.
In the Upper Warrego, Commonwealth environmental water complemented natural flow events that occurred between September and April, with benefits including reconnection of waterholes in the Warrego River Waterholes site. In the Lower Warrego, water used in October 2010 contributed to the first post-winter flow in the system, which is known to be a critical spawning cue for native fish species. During March to April 2011, water was used to contribute to an overbank flow that charged the nationally significant Warrego River distributary system and Yantabulla Swamp.
For further information about the Commonwealth environmental watering in the Warrego and the outcomes achieved, please refer to the Commonwealth environmental water Outcomes Reports and Annual Reports.
Where is it?
The Warrego Catchment is predominantly in Queensland and spans the area from the Carnarvon Range at the northernmost point of the Murray-Darling Basin to the Darling River in northern New South Wales. It is bounded to the east by the Condamine-Balonne region, to the west by the Paroo region and forms the northern edge of the MDB. The region is generally flat with a gentle southwards gradient. The upper catchment of the Warrego River includes the Warrego and Chesterton ranges.
It covers a total area of 87,749km2, or 8.4 per cent of the Murray-Darling Basin. Tributaries to the Warrego include the Nive and Langlo Rivers. The Warrego River enters the Darling River downstream of Bourke, and during times of flood is connected to the Paroo River via Cuttaburra Creek. This system is one of the last unregulated systems in the MDB.
What makes this place so special?
The Warrego catchment is an ecologically significant area because it includes:
- a wide variety of vegetation including native grasslands, saltbush shrubland, mulga woodlands and shrublands, brigalow and eucalypt stands
- one of the only places where silver perch breed naturally
- a diverse range of other fish communities including bony herring, golden perch and Australian smelt
- species listed under the NSW Threatened Species ACT 1995 (TSC Act) including Major Mitchell's cockatoo and brolga
- wetlands covering a total area of approximately 345,000 ha which are of critical importance to waterbird populations of the MDB.
Many wetlands in the Warrego River catchment are recognised as being of national importance; the two which have been most extensively researched are Yantabulla Swamp and the Warrego River Waterholes.
Yantabulla Swamp is part of the Cuttaburra Basin system, which is filled from various sources including Cuttaburra Creek and Paroo River overflow. The swamp covers over 37,000 ha and has been identified as the most important waterbird breeding site in north-west NSW. The main vegetation communities are cane grass, lignum, fringing yapunyah, river red gum, coolabah and river cooba.
The Warrego River Waterholes are a string of large permanent and intermittent waterholes covering some 500 ha along the river channel in Queensland. These sites are flooded seasonally in most years. They provide an invaluable habitat and refuge for a wide range of aquatic fauna including species listed under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) such as Murray cod. Significant waterbird populations are known to inhabit the waterholes particularly during periods of high flows.
What does the latest science say about the ecological health of the catchment?
The Murray-Darling Basin Commission Sustainable Rivers Audit (SRA) rated the overall health of river ecosystems in the Murray-Darling Basin. The SRA reports the overall ecosystem health of the Warrego catchment as poor.
The CSIRO Sustainable Yields Report on the Warrego indicated that the current level of surface water extraction is very low. Surface water use is strongly influenced by the seasonal rainfall patterns which dictate runoff and stream flow; use varied between about 2 GL to 11 GL per year between 1993 and 2005. This represents less than one per cent of the surface water use in the MDB. The best estimate 2030 climate scenario indicates a six per cent reduction in river inflows leading to a seven per cent reduction in total end-of-system flows.
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.