FLOODS OF LAKE EYRE
Lake Eyre South
Lake Eyre South occupies an area of 1 260 km² and can store 2.4 km³ of water at -9.5 m ahd and an average depth of 1.9 m. The deepest region, reaching -13.2 m ahd, is located in a long trough offshore from the southern coastline.
Trustworthy data on the filling of Lake Eyre South are reported for the floodings of 1938, 1955, 1963, 1968, 1973, 1974, 1975, 1976 and 1984. In 1984 Lake Eyre South overflowed to Lake Eyre North (Hutton, 1984). In 1974 water flowed from Lake Eyre North to Lake Eyre South between 19 March and October when an equilibrium level was obtained. Large quantities of salt, estimated at 30 million tonnes (i.e., 7.5% of Lake Eyre North content), were transferred into Lake Eyre South during this event, creating, in its lowest portion, a salt crust up to 290 mm thick for the first time on record (Dulhunty, 1978). Previously the salt layer in Lake Eyre South was never thicker than a 'fraction of an inch' (Bonython, 1961). The return of this salt to the deeper Lake Eyre North is known to occur, but the actual process is not fully understood. An investigation of recent overflow to Lake Eyre North could provide some information on this matter, Allan et al. (1986) state that about 40% of the salts introduced into Lake Eyre South in 1974 returned back into Lake Eyre North in 1984, suggesting that surface hydrology is the major factor in the salt balance.