A GIS-based reconstruction of late Quaternary paleohydrology: Lake Eyre, arid central Australia

Abstract

Lake Eyre is the terminal playa in a large closed basin which receives the majority of its moisture from the summer monsoon. Modern Lake Eyre receives intermittent floodings at times of increased monsoon intensity, generally associated with the La Niña phase of the ENSO cycle. Lake Eyre was a perennial lake during several phases of increased monsoon activity during the late Quaternary, specifically about 125 ka, 80 ka, 65 ka, and 40 ka [Magee (1997) Late Quaternary Environments and Palaeohydrology of Lake Eyre, Arid Central Australia. Unpubl. Ph.D. Thesis, Australian National University, Canberra]. These lake highstands are reflected by elevated shorelines mapped around Lake Eyre and, to a lesser degree, around the Frome–Gregory system to the southeast of Lake Eyre. Comprehensive research in the Lake Eyre catchment over the last several decades has constrained the ages and elevations of these shoreline deposits, which now enable us to use digital elevation models to map these paleo-lakes. By incrementally filling each lake meter by meter, the areas and volumes of the paleo-lakes are calculated and the paleohydrologic processes, including the flow direction across spillovers, are reconstructed. At the peak 125-ka highstand, Lake Eyre stood at +10 m Australian Height Datum (AHD) and covered nearly 35 000 km 2, more than three times the area of the current playa. Together with the Frome–Gregory system, it held 430 km 3 of water. By contrast, the deepest historic filling held 30 km 3. These lake levels represent climatic conditions very different from the modern situation. Due to discontinuous preservation of the shoreline deposits around the lakes and due to the scale of the lake systems, mapping the former levels of Lake Eyre and the Frome–Gregory system has been impossible prior to the availability of a digital elevation model. Paramatizing the area/volume relationships of water required to fill the lake to varying levels will provide data for quantification of climate and precipitation changes over time.