The influence of physical catchment properties on baseflow in semi-arid environments

The present paper examines the influence of physical catchment properties on baseflow in semi-arid environments. It relates the dimensionless quantity, baseflow index (BFI) derived from data-based mechanistic modelling approach to dimensionless indices representing topographic, geologic and climatic properties. The relationship is derived using a progression of techniques, from inspection and correlation analysis, through stepwise regression and finishing with multiple regression. The BFI has a strong relationship with climate and geology. Catchments with high rainfall or low evapo-transpiration underlain with granites or basalt tend to give high baseflow. Within the topographical parameters tested, drainage density index has strong relationship with BFI. The approach used in this paper provides a viable alternative for baseflow estimation on ungauged semi-arid catchments using drainage density, geology and climate indices as key factors.