Influence of Climate Characteristics on Streamflow in the Murray–Darling Basin

Understanding the relationship between streamflow and climate input is important to inform how streamflow characteristics could change under climate change. The first part of this study assessed the relationship between annual streamflow and climate characteristics using rainfall, potential evapotranspiration (PET) and streamflow data from 133 catchments across the Murray–Darling Basin (MDB). The second part assessed the response of key streamflow metrics (mean annual runoff, high-flow days, low-flow days and minimum three-year flow) to changes in rainfall characteristics and PET using a weather generator and five hydrological models. The results indicate that annual streamflow is strongly correlated to many rainfall characteristics. However, these rainfall characteristics are also strongly correlated to annual rainfall, and therefore annual rainfall is generally a good predictor of annual streamflow. Rainfall characteristics that have a secondary influence on annual streamflow include effective rainfall, which is defined as the cumulative positive differences between daily or monthly rainfall and PET, rainfall seasonality, multi-day rainfall totals and multi-year rainfall lows. The change in future mean annual streamflow is driven primarily by the change in mean annual rainfall and PET, followed by some of the rainfall characteristics above. In addition to mean annual rainfall, high flows are also strongly influenced by multi-day rainfall totals, while multi-year hydrological droughts are also influenced by multi-year rainfall lows and annual rainfall variability. These results are useful to identify the key climate characteristics in assessing the impacts of future climate change on water availability, and potentially for developing next-generation hydrological models that can deal with non-stationarity and better predict streamflow under a changing climate.