Stress testing climate change impacts on snow cover and streamflow in southeast Australia

This study addresses the impact of climate change on snowmelt and its implications for water supply in southeast Australia. Snow affects only a small proportion of mainland Australia, yet it is a significant hydrological component for key systems such as the Murray Darling Basin, where seasonal snowmelt is an important source of irrigation water. Although it is desirable to incorporate snow hydrology into water resource planning, a key challenge is for modelling to be sufficiently parsimonious to be amenable to techniques which test water resource systems under a wide range of climatic conditions, such as stress-testing. For southeast Australia, a further challenge is the limited availability of snow data, which has hindered previous studies. Here, we present a practical method to incorporate snow hydrology into water resource assessments, focusing on the southern Murray-Darling Basin as a case study. An existing temperature-dependent threshold approach is used to estimate snow cover on a monthly timestep, calibrated using remote sensing data. This approach is integrated into an existing rainfall-runoff model and applied to the Snowy Mountains region of the Murray Darling Basin, stresstesting against a variety of climatic conditions. The results demonstrate the importance of snow processes in determining the seasonal sensitivity of regional streamflow to climate, particularly temperature. More broadly, this study demonstrates a simple and widely applicable method for investigating climate impacts on snow and water resources in the face of climate change.