Hydrological similarity and controls of streamflow behaviour in eastern Australian catchments

Abstract:

Along the eastern Australian seaboard, changes to both landscapes and climate are altering the hydrological cycle and impacting catchment outflows. The region supports 80% of the human population and regularly experiences extreme events such as tropical cyclones, floods and droughts. These changes in the hydrological cycle affect water supply for urban population centres, reduce economic activities and threaten water-dependent ecosystems. An important question that emerges from these issues is how human-modified, spatially heterogeneous catchments are responding to hydrological changes and which biophysical factors are driving the streamflow response. In order to organize and classify heterogeneous catchments with regard to their hydrological functioning, this study utilizes daily streamflow and rainfall time series to quantify hydrological similarity across 402 catchments located along the east coast of Australia. We computed several metrics such as runoff ratio, slope of the Flow Duration Curve, and streamflow elasticity to describe how catchments respond to rainfall input over a period of 30 hydrologic years (1980 to 2010). We used ordination analysis and mixed-effect models to evaluate how the landscape and climatic characteristics of catchments are controlling both individual hydrological signatures and the dominant streamflow response. This work provides new insights into how catchments characteristics and climate variability are interacting to control hydrological behaviour.