Vízügyi Közlemények, 1995 (77. évfolyam)

1. füzet - Goda László: A Duna gázlói Pozsony-Mohács között

100 Goda László Analyzing the hydrologieal conditions of the period in concern it was found that no trends of the flow conditions can be identified (Figures 2. and 3., Table I.). The annuel distribution of the occurrence of extreme shallows was analyzed on the basis of the monthly sum of the days with critical shallows (fords) for the river reaches between Pozsony and Szob and Szob-Mohács (Figures 3. and 4.). It is concluded that the occurence of shallows depend, in addition the annual mean flow, of the annual variation pattern of the river flow (Figures 4. and 5.). I laving the water regime analyzed the causes of the occurrence of shallows is analyzed for each river reach with special regard to slope conditions, sediment discharge, conditions of river bends and to river training activities and commercial gravel dredging. Presenting the frequency distribution of the shallows of the river reach between Pozsony/Bratislava and Mohács (Figures 5. and 6.) it is pointed out that there are 8 fords of importance between river kilometres 1810 and 1800. River reaches of identical characteristics arc defined on the basis of minimum ford depths and maximum periods of shallows (Figure 7.). Figures S. and 9. show the longitudinal variation of minimum ford depths as observed in the period 1961-1990. The detailed characterization of the ford conditions was made for the partial river reaches shown in Figures 10. and 11. Temporal and longitudinal variation of ford depths are utilized for this characterization. The density of fords within the selected partial river reaches are also analyzed along with the depths and the length of the periods with shallows. Effects of river training activities and dredging operations are also investigated. An attempt to determine the relationship between river water levels and shallow depths was made for the fords of Dömös and Budafok (Figures 12. and 13). Figure 1. shows the characteristic temporal variation of shallow conditions. On the basis of the data it was concluded that the conditions of shallow fords have deteriorated in the Pozsony/Bratislava-Szob river reach, while they were slightly improving along the river reach Szob-Mohács. The importance of the shallows of the common Hungarian-Slovak and the Hungarian river reach in the navigability of the River Danube as a whole is also emphasized. It is pointed out that the river reach between Pozsony/Bratislava and Gönyű is of deterministic importance from the view point of both the spatial density of fords and the sum of days with critical ford depths (Figure 15). Similar conclusion is drawn on the basis of the temporal variation of average ford characteristics (Table II.) and also on the basis of analyzing the decisive role of the individual fords (Figure 16.). * * * Die Furten der Donau zwischen Bratislava lind Mohács von Dr.-lng László GODA. CSe. Der Verfasser hat für die Hydrologische Arbeitsgruppe der Donauländer (RZdD) das Manuskript eines Monograhie-Folgebandes über die Furten der Donau zusammengestellt. Im vorliegenden Beitrag werden daraus die für die Periode 1961 -90 kennzeichnenden Furtverhältnisse der für Ungarn am meisten interessanten Donaustrecke zwischen Bratislava (Preßburg) und Mohács erörtert. Aufgrund einer Analyse des Abflußregiines der Untersuchungsperiode wird festgestellt, daß darin keine trendartigen Veränderungen nachgewiesen werden können (Bilder 2 und 3, Tabelle I). Ausgehend aus den monatlichen Summen der Furttage wird die inncrjährliche Verteilung des Auftretens von Furten sowohl für die Strecke Bratislava-Szob, als auch für diejenige Szob-Mohács charakterisiert (Bilder 3 und 4). Es wird festgestellt, daß bei dem Enstehen der Furten, außer dem mittleren Jahresabfluß, auch die innerjährliche Verteilung der Abflüsse eine bedeutende Rolle spielt (Bilder 4 und 5). Nach den Faktoren des Abflußregimes werden für die einzelnen Donaustrecken die Ursachen der Entstehung von Furten analysiert,mit besonderer Rücksicht auf die Gefälleverhältnisse, auf die