
Catchment conditions
During the 2021–22 year the Lachlan catchment experienced very wet La Niña weather conditions, with rainfall in some parts of the catchment breaking records. Inflows into Wyangala Dam led to the full 350,000 megalitres (ML) of translucent flow delivered past Lake Brewster Weir from July to September 2021. Wyangala Dam remained under flood management operations for the remainder of the water year.
Wyangala Dam spilled in September 2021 and again in March 2022, with general security entitlements reset at 115% and 121%, respectively. As a result, the Lachlan River and creek systems ran high for most of the water year and connected to riparian and floodplain wetlands for durations not seen in decades.
Water for the environment was managed primarily to extend the duration, depth and lateral connectivity of floodplain inundation in the lower Lachlan distributary creeks and to support colonial waterbird breeding.
About the catchment
The Lachlan catchment is in central western NSW, covering an area of 90,000 square kilometres. Climatic zones of the Lachlan catchment vary markedly as it flows from the headwaters and tablelands in the east through the slopes of the middle catchment, to the flat, western plains.
The major river is the Lachlan with nearly 1,300 kilometres of the 1,400-kilometre river regulated by water storages, of which Wyangala Dam is the largest at 1,220 gigalitres (GL). It starts as a chain of ponds near Gunning and ends in the Great Cumbung Swamp, only flowing through to the Murrumbidgee when both rivers are in flood.
The Lachlan catchment is characterised by alluvial floodplains and distributary creek systems. It maintains some of the most diverse assemblages of wetland habitats, some only found in this catchment. Important sites include the Booligal Wetlands, Lake Brewster, Lake Cowal, Great Cumbung Swamp and Lachlan Swamps, all of which are listed in the Directory of Important Wetlands in Australia.
Traditional owners
The Lachlan is Country to the Wiradjuri, Nari Nari, Mutthi Mutthi, Ngiyampaa and Yita Yita First Nations.