Covering an area of 81,527 square kilometres, the Murrumbidgee valley includes 26 storage or diversion structures, along with a 1690-kilometre stretch of the river, and surrounding wetlands.
The Murrumbidgee catchment saw increasingly wet conditions and above average inflows during summer and autumn 2020–21. This resulted in 100% general security allocations being reached by 15 January 2021 (the average carryover was 18%) with about 30 gigalitres of NSW environmental water allowances available for use.
The focus of water managers in 2020–21, with an increasing resource availability scenario as identified in the Murrumbidgee catchment: Annual environmental watering priorities 2020–21, was aimed at restoring a more normal flow pattern to support a robust food web and other system functions. Dry conditions continued until early 2021 when wetter than expected conditions occurred.
Water was carried over from the 2019–20 water year to build on low starting allocations. Under these conditions, environmental water managers worked with the Commonwealth Environmental Water Holder to water the Gayini (Nimmie-Caira) wetlands, located in the Lowbidgee region. This private property event inundated over 15,000 hectares of lignum wetlands and creeks, triggering significant colonial waterbird breeding events.
Remaining water for the environment was used to maximise native fish passage as well as habitat important to waterbird species such as Australasian bitterns and brolgas. Significant outcomes included:
- improved condition of wetland vegetation communities in the Lower Murrumbidgee
- improved fish habitat within the river channel and on the Lowbidgee floodplain
- southern bell frog recolonisation
- Australasian bittern breeding in Eulimbah swamp and Yanga National Park
- brolga breeding in Wanganella swamp.