Reconstructing lake hydrological variability using satellite Imagery: a case study for western Victoria, Australia

Abstract

Australia is well known for its climate of relatively low rainfall and high rates of evaporation and due to these sorts of conditions, lakes can be considered quite rare. However, even due to this rarity, lakes in Australia represent important landscape features that hold environmental, cultural and economic value. With forecasted increases in temperature and declines in rainfall for the future, this will have a negative impact on Australia’s lakes, however, these effects are poorly understood. Therefore, there is a need for research that examines the response of lake hydrology to climate change. One approach that has proven effective is the involvement of satellite-based observation methods. This study adopted an approach of using Landsat imagery to reconstruct the surface area of 15 lakes in western Victoria. Data were obtained from the Water Observations from Space (WOfS) algorithm accessed through the Digital Earth Australia (DEA) data platform to infer lake surface area change from 1987 – 2020. By comparing surface area changes to annual rainfall and evaporation data, the resulting correlations give better insight into explaining if the correlations are best described by either one of these variables independently, or if lake variation is determined more so by a combination of factors. The results of this study demonstrate that each of the 15 lakes shows very similar responses in annual maximum surface area variation. Despite morphological differences between the lakes, the similarity in their surface area responses implies a universal factor being strongly responsible for their hydrological variability – namely climate variability. Correlations of individual climate variables with lake surface areas are low, leading towards the idea that lake variation cannot be examined through only one independent variable, but rather a combination of factors that all have differing effects on lake fluctuation through time. Understanding which combination of factors determines individual lake fluctuation is crucial to understanding how lakes respond to changing climate conditions. To ensure lake survival into the warming and drying future, more focussed, process-based research into the fluxes of water into and out of these lakes is needed in order to comprehend the resilience of the lakes under future climate changes.