COMMON UNITGRAPHS FOR SETS OF RUNOFF EVENTS .1. UNITGRAPH IDENTIFICATION FROM STREAMFLOW DATA

It is demonstrated that a unitgraph can be obtained without using rain fall data, provided data from at least two runoff events are available . A numerical method has been devised which calculates this common uni tgraph for a set of surface runoff events and at the same time determi nes the input (rainfall excess) for each event. The method has been su ccessfully tested on catchments ranging in size from 0.4 to 600 km(2); it requires streamflow observations taken at intervals which retain a ll significant frequencies in the runoff hydrographs. The method also requires application of a baseflow separation procedure which is consi stent for all events. The new approach has the potential to lead to mo re objective studies of the effects of catchment changes on the unitgr aph and provides scope for comparisons of the common unitgraphs with g eomorphological instantaneous unitgraphs.