Hydrograph recession characteristics of some small agricultural catchments

Abstract

Five-min recession constants were calculated for surface runoff and interflow using hydrographs of runoff from five 1-ha catchments at Greenmount near Toowoomba in south-east Queensland. The recession constants were converted to half-flow periods, i.e. the time required for flow rate to halve during an exponential recession. The half-flow periods of surface runoff and interflow on the 1 ha catchment are compared with published data from catchments of much larger size in New South Wales, and it is shown that the ratio of interflow half-flow period to surface runoff half-flow period does not vary much over six orders of magnitude of catchment size. Calculations of maximum rates of interflow and volumes of interflow storage show that both rates and volumes are possible in the plough depth of surface soil. The results support the evidence of interflow obtained earlier in unit hydrograph studies of runoff on these same catchments.