However, large storms tend to be more common in summer when the occasional remnants of tropical cyclones drift over central Australia. The only occasion that stream flow occurs is after rainfall events. In small catchments streamflows are relatively short, perhaps a few hours to a few days. Thus, it may take one or two months for the water in the upper reaches to get to the lower reaches. When in flood, rivers such as Cooper Creek may spread as wide as 50km.
Most rivers contain very little permanent water.
All the water exists in a series of waterholes, most of which disappear after a year or two with no flow. Turbidity, caused by fine clay particles, is typically exceptionally high. The following is a short summary of each. A map of the Bulloo-Bancannia Drainage Division is at the end of the item. The Bancannia system consists of a series of small isolated creeks and lakes which remain poorly sampled.