Warrego River

Course and features

The river rises from below Mount Ka Ka Mundi in the Carnarvon Range, near Tambo in Queensland, and flows generally south, reaching its confluence with the Darling River, downstream from Bourke. The river is joined by thirty-seven tributaries, including the Nive and Langlo rivers, descending 528 metres (1,732 ft) over its 1,380-kilometre (860 mi) course. The river flows through a series of reservoirs, including the Dillalah Waterhole, Ten Mile Waterhole, Lower Lila Dam, Six Mile Dam, Turtle Waterhole, and Boera Dam.

The towns of Augathella, Charleville, Wyandra and Cunnamulla are located on the banks of the river.

Inflows

Most of the basin of the Warrego is too dry for cropping and has a very erratic rainfall of between 350 and 500 millimetres (14 and 20 in). It is covered with a natural vegetation of grassland on more fertile clay soils, and saltbush shrubland on less fertile red earths. The predominant land use is low-intensity grazing of sheep and cattle: the river's flow is much too erratic to permit irrigated cropping. The Warrego is essentially an ephemeral stream: it is not unknown for years to pass without any flow in the basin and substantial amounts of water reach the Darling River only in wet years almost always associated with La Niña events.

Outflows

Below Wyandra the river forms a series of outflowing creeks and anabranches. During floods, the Widgeegoara, Kudnapper and Noorama Creeks allow water to channel into Nebine Creek, a tributary of the Culgoa River. Cuttaburra Creek connects the Warrego to the Paroo River via a distribution system that flows through channels, floodways and wetlands. The Irrara Creek anabranch flows into Kerribree Creek which continues into a number of wetlands before filling Utah Lake.

Flooding

When La Niña occurs, flooding is usual along the Warrego: major floods associated with La Niña events occurred in 1950, 1954 to 1956, 1971, 1973, 1998 and 2008. Oddly, the most destructive flood ever recorded on the river took place in the absence of La Niña. In April 1990, as a result of two extremely strong troughs in the easterlies, over 400 millimetres (16 in) of rain fell in Cunnamulla in two weeks, being more than the annual rainfall in over 60 percent of years. The river, along with most tributaries of the Darling, reached near-record levels and the towns of Augathella and Charleville were devastated. At Charleville a river height peak of 8.54 metres (28.0 ft) was recorded.