Influence of groundwater on the evaporative evolution of saline lakes in the Wimmera of south-eastern Australia

A hydrogeochemical study conducted in the southern Wimmera of western Victoria, south-eastern Australia reveals a small group of lakes that possess a range of chemical character so diverse that it compares to that recorded for lakes from the entire region of western Victoria and south-eastern South Australia. Principal Components Analysis and reaction path modelling using PHRQPITZ confirm that the chemical diversity of the lakes is largely inherited from the groundwater system. Three end-members (in the Eugster–Jones–Hardie framework) were identified: (i) Path 1B groundwaters transmitted via the fractures of a sandstone monolith; (ii) Path 2A-1A groundwaters derived, in part, from a limestone aquifer; and (iii) groundwaters that carry an essentially meteoric, Path 2A signature. The relative contribution of these path 1B and/or path 2A end-members largely determines the evaporative pathway (1B or 2A) that is subsequently followed, and creates a broad spread in the data. Sulphate reduction, ion exchange, silicate hydrolysis and carbonate mineral solubility also play important roles locally, in some cases displacing lake waters from one evaporation field to another. The chemical processes identified likely contribute to aquatic biodiversity in the region, due to the strong control on the ionic composition of the lakes.

L. C. RadkeEmail: