Use of similarity criteria for transposing gauged streamflows to ungauged locations

摘要

This paper presents a methodology for transposing streamflow data from a gauged to an ungauged catchment, and practical tools for transposition of streamflow anywhere in Victoria are presented. Firstly a measure of the similarity of streamflow regime is developed. Gauged catchments and their physiographic characteristics are used to delineate variation in the streamflow regime in a way that allows the similarity in streamflow regime of two catchments to be estimated. Three streamflow characteristics (base flow index, mean annual flow and medium summer flow) are selected to define the streamflow regime. Multiple linear regression is used to identify the physiographic characteristics that influence the streamflow characteristics defining the streamflow regime, and principal component analysis is used to assess the similarity of catchments based on these physiographic characteristics. The similarity of catchments based on these measures provides the basis for the selection of the most appropriate gauge from which to transpose. While it is clear that a larger catchment will yield more streamflow than a hydrologically similar but smaller catchment, differences in streamflow are generally not directly proportional to catchment size. To aid the transposition of streamflows a regional prediction equation based on catchment characteristics is developed for mean annual flow and the use of mean annual flow as a transpositional factor is described.