The Warrego River is situated in south west Queensland and north west New South Wales, Australia. It briefly flows westwards from its source in the Carnarvon Ranges towards Tambo, but then turns to flow basically southwards from the Carnarvon Ranges in central Queensland through to its junction with the Darling River, downstream from Bourke. Tributaries include the Nive, Langlo and Ward rivers.
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 inches), and covered with a natural vegetation of grassland of 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 of 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. When La Niña does strike, 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 of rain (more than the annual rainfall in over 60 percent of years) fell in Cunnamulla in two weeks. The river, along with most tributaries of the Darling, reached near-record levels and the towns of Augathella and Charleville were devastated.