CLUSTER ANALYSIS IN DETERMINATION OF HYDROLOGICALLY HOMOGENEOUS REGIONS WITH LOW FLOW

In the paper results of evaluation of using statistical methods for data agglomeration were made. For determination of hydrological homogeneous regions characterized by low flow and selected physiographic and meteorological features of the catchments cluster analysis was used. The study material included daily flows from the multi-year period of 1963-1983 collected for 15 catchments located in the upper Vistula basin. Low flows were quantified by Q(95)%, i.e. the discharge that is exceeded on 95% of all days of the measurement period. This low flow characteristic is widely used in Europe and was chosen due to its relevance for multiple choices of water management. Then, Q(95)% was subsequently standardized by the catchment area and resulting specific low flow discharges q(95)dm(3)center dot s(-1)center dot km(-2). The calculations and their analysis showed that, statistical methods of data agglomeration may be used for determination of hydrologically homogeneous regions. And with use Ward's method with cut-off level at 40% two homogeneous regions were identified.