Changing trends of river flows in the Upper Vistula Basin (East-Central Europe)

Marek Górnik

doi:10.1007/s11600-020-00400-9

Abstract

The mean annual, winter half-year and summer half-year flows at 86 water level gauges in the Upper Vistula Basin in the years 1951–2015 were examined. The Ward’s hierarchical cluster analysis was used for grouping sub-catchments in reference to the standardized aforementioned flows. Trends analysis was performed for each cluster of catchments in all combinations of periods not shorter than 20 years. Spatial distribution of clusters of catchments has been analysed according to geographical locations. There are observed different trends in distinguished groups of catchments, wherein the substantial differences concern long-term trends. Changes in trend direction in the years 1951–2015 were revealed, which indicate flow fluctuations. Presumably, physiographical heterogeneity of the Upper Vistula Basin is reflected in no unequivocal trends occurring in clusters of catchments. Some similarities were stated in short-term trends occurring in particular groups of catchments.

Highlights

Increase in air temperature and changes in precipitation have been noted in many areas but their effect on river flow has been difficult to pinpoint
River runoff integrates the influence of this complex phenomenon over a watershed; the analysis of long time series of river discharge datasets does not result in unequivocal satisfactory and expected results
The share of the outflow from the Upper Vistula Basin in relation to the outflow from the whole Vistula basin amounts to 41%, it occupies only 25% of the entire Vistula River Basin (Chełmicki 1991)

Summary

Introduction

Increase in air temperature and changes in precipitation have been noted in many areas but their effect on river flow has been difficult to pinpoint. The catchments were clustered into a few regions broadly homogenous in terms of standardized annual (S_ STD SQY), standardized winter half-year (S_STD S QW) and standardized summer half-year (S_STD S QS) river flow series in the studied multiannual period. The catchments are clustered into eight groups, which are broadly homogenous in terms of variability of the summer half-year river flow (Fig. 6). Trends of the summer half-year average river flow starting between 1951 and 1961 are positive for the groups SI, SII, SIII, SV and likewise for the groups SIV, SVI and SVII but only until the middle of the 1980s followed by negative trends onwards. Negative trends occur merely in periods starting between 1971 and 1975 and ending in 1995 in this group

Discussion

Conclusions

Findings

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