Lake Eyre is the lowest point in Australia, at approximately 15 m (49 ft) (AHD) below sea level, and, on the rare occasions that it fills, the largest lake in Australia. It is the focal point of the vast Lake Eyre Basin and is found some 700km north of Adelaide.

Geography

The lake was named after Edward Eyre who was the first European to sight it in 1840. The lake is located in the deserts of central Australia, in northern South Australia. The Eyre Basin is a large endorheic system surrounding the lakebed, the lowest part of which is filled with the characteristic playa salt pan caused by the seasonal expansion and subsequent evaporation of the trapped waters. Even in the dry season there is usually some water remaining in Lake Eyre, usually collecting in a number of smaller sub-lakes on the playa.

During the rainy season the rivers from the northeast (in outback Queensland) flow towards the lake through the Channel Country. The amount of water from the monsoon determines whether water will reach the lake and if it does, how deep the lake will get. In strong La Niña years the lake can fill. Since 1885 this has occurred in 1886/1887, 1889/1890, 1916/1917, 1950, 1955, 1974-1976, with the highest flood of 6m in 1974. Local rain can also fill Lake Eyre to 3-4m as occurred in 1984 and 1989. Wave built shingle terraces on the shore suggest that during the Medieval Warm Period and centuries immediately prior Lake Eyre possibly held permanent water at levels above those of 1974. Torrential rain in January 2007 took about six weeks to reach the lake but put only a small amount of water into it.

When recently flooded the Lake is almost fresh and fresh water fish, such as Bream, can survive in it. The salinity increases as the 450mm salt crust dissolves over a period of six months resulting in a massive fish kill. When over 4m deep the Lake is no more salty than the sea and salinity increases as the water evaporates with saturation occurring at about 500mm depth. The Lake takes on a "pink" hue when saturated due to the presence of beta-carotene pigment caused by the algae Dunaliella salina.

Typically a 1.5 m (5 ft) flood occurs every three years, a 4 m (13 ft) flood every decade, and a fill or near fill four times a century. The water in the lake soon evaporates with a minor and medium flood drying by the end of the following summer.

credited to wikipedia and flickr: Julie Fletcher Photography