An approach to hydrograph classification

The stream hydrograph is an integration of spatial and temporal variations in water input, storage and transfer processes within a catchment. For glac ier basins in particular, inferences concerning catchment-scale processes h ave been developed from the varying form and magnitude of the diurnal hydro graph in the proglacial river. To date, however, such classifications of pr oglacial diurnal hydrographs have developed in a relatively subjective mann er. This paper develops an objective approach to the classification of diur nal discharge hydrograph 'shape' and 'magnitude' using a combination of pri ncipal components analysis and cluster analysis applied to proglacial disch arge time-series and to diurnal bulk flow indices. The procedure is applied to discharge time-series from two different glacier basins and four separa te ablation seasons representing a gradient of increasing hydrological pert urbation as a result of(i) variable water inputs generated by rainstorm act ivity and (ii) variable location and response of hydrological stores throug h a systematic decrease in catchment glacierized area. The potential of the technique for application in non-glacial hydrological contexts is discusse d. Copyright (C) 2000 John Wiley & Sons, Ltd.