DBPapers
DOI: 10.5593/SGEM2016/HB33/S02.039

THE ANALYSIS OF THE SEASONALITY AND TRENDS OF THE ANNUAL MAXIMUM DISCHARGES IN THE UPPER DANUBE RIVER

R. Markova, A. Xhaja, S. Kohnova
Friday 11 November 2016

References: 16th International Multidisciplinary Scientific GeoConference SGEM 2016, SGEM Vienna GREEN Extended Scientific Sessions, www.sgemviennagreen.org, SGEM2016 Conference Proceedings, ISBN 978-619-7105-81-0 / ISSN 1314-2704, 2 - 5 November, 2016, Book 3 Vol. 3, 303-310pp, DOI: 10.5593/SGEM2016/HB33/S02.039

ABSTRACT

The presented study deals with the analysis of the seasonality of annual maximum floods and their trends in the Upper Danube River region. Due to the increasing frequency and severity of flood events (not only in Slovakia but also in the world), it is important to examine their behaviour and regimes in order to be able to properly and timely respond to risks that may result from these situations. In recent years, considerable attention has been devoted (particularly in Europe) to the detection and analysis of trends in flood characteristics such as annual maximum flows, maximum water stages or flood frequencies. Seven gauging stations on the Upper Danube River were investigated. The stations were located between Danube spring (the Black Forest mountains) and Devín Gate (Porta Hungarica). The Upper Danube River basin is characterized by high precipitation totals. The goal of the investigation was to estimate the causes of the formation of runoff, to determine of time variability of summer and winter floods and to identify trends and their changes. For the analysis of the seasonality or trends it is possible to use many different statistical applied methods. We focused on circular statistics [1] for the seasonality analysis. This method consists of defining the mean daily flood (directional mean) and the flood variability measure. The seasonality analysis showed that annual maximum discharges in the winter season are concentrated in January and February, whilst the annual maximum discharges in the summer season was noticed between June and July. The winter floods had a strong seasonal occurrence (0.8-0.9) and arose principally from snowmelt. The summer floods had a high variability occurrence (0.2-0.7), and arose from torrential rains. They are influenced by oceanic and warm, humid continental climate. The different climatic systems influenced rainfall and air temperature. The Berg station, which was the closest gauging station to the river source, was influenced by oceanic climate (based on Köppen-Geiger classification [12]), while the other gauges were influenced by warm, humid continental climate. The Standard Normal Homogeneity Test (SNHT) [6] was used at a significance level of 5 %. All gauging stations were homogeneous and this allowed the use of linear regression for trend detection. The modified Mann-Kendall test was used for the moving window and Theil-Sen slope for the trend analysis. The results of linear regression in the most cases showed increasing trends in maximum annual discharges. The Berg station showed a decreasing trend because it was the only station influenced by a different climate system. The modified Mann-Kendall method for the moving window showed mostly upward but not significant trends for the Upper Danube River basin.

Keywords: annual and seasonal floods, Mann-Kendall trend, circular statistics, seasonality

PAPER DOI: 10.5593/SGEM2016/HB33/S02.039, THE ANALYSIS OF THE SEASONALITY AND TRENDS OF THE ANNUAL MAXIMUM DISCHARGES IN THE UPPER DANUBE RIVER

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