Hydrological characteristics of Australia: relationship between surface flow, climate and intrinsic catchment properties

Abstract

Streamflow and baseflow dynamics are driven by complex, interconnected catchment properties. A national study was conducted to assess the relationship between surface flow, climate and intrinsic catchment attributes in Australia. Subcatchments were delineated based on Horton's 5th stream order and were characterised by identifying parameters that influence streamflow and flood behaviour. Because observational datasets like rainfall and streamflow commonly have a non-normal distribution, the method of L-moments was applied to several time series. Surface hydrology and baseflow patterns were represented by twenty indices, which were statistically summarised via principal component (PC) analysis, yielding six PCs. Forty catchment descriptors from the themes of climate, topography, surface condition and hydrogeology were used to investigate their link with runoff patterns. Among these is the land surface value, a newly defined index incorporating soil properties and land use to estimate the capacity for water infiltration. All metrics were explored via correlation and regression analysis against the surface hydrology PCs and their influence on runoff discussed. The predictive skill of the regression models is improved when non-perennial waterways are excluded. Although rainfall characteristics dominate streamflow behaviour, topographical and surface conditions also greatly impact on runoff, especially during low-flow periods.