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 glacier basins in particular, inferences concerning catchment-scale processes have been developed from the varying form and magnitude of the diurnal hydrograph in the proglacial river. To date, however, such classifications of proglacial diurnal hydrographs have developed in a relatively subjective manner. This paper develops an objective approach to the classification of diurnal discharge hydrograph 'shape' and 'magnitude' using a combination of principal components analysis and cluster analysis applied to proglacial discharge time-series and to diurnal bulk flow indices. The procedure is applied to discharge time-series from two different glacier basins and four separate ablation seasons representing a gradient of increasing hydrological perturbation as a result of(i) variable water inputs generated by rainstorm activity and (ii) variable location and response of hydrological stores through a systematic decrease in catchment glacierized area. The potential of the technique for application in non-glacial hydrological contexts is discussed. Copyright (C) 2000 John Wiley & Sons, Ltd.