SIMILARITIES AND DIFFERENCES OF THE HYDROLOGICAL EXTREMES ON THE DUNA/DANUBE AND TISZA/TISA RIVERS (1921-2012)
KONECSNY K., NAGY Z.
ABSTRACT. Similarities and differences of the hydrological extremes on the Duna/Danube and Tisza/Tisa rivers (1921-2012). In terms of the water management in Hungary, both rivers have a highlighted importance, which is also indicated by the fact that 50-55% of the territory of the country is divided between the two catchment areas. Though the Tisza is the tributary of the Duna River, its catchment area, its bed length, its typical discharges are smaller than those of the host Duna, but on the Hungarian territory there is no size difference between them. Thus, the catchment area of the Tisza River above the Hungarian-Serbian border (at Szeged) is 138.408 km2, the catchment area of the Duna River above Budapest (at Nagymaros) is 183.534 km2, so the spatial difference is aproximatively 25%. In the medium many years discharge the difference is almost three times, on the Tisza at Szeged it is 834 m3/s, on the Duna, at Nagymaros is 2308 m3/s. On the Tisza River, at Szeged the maximum discharge exceeds 75 times the minimum discharge, on the Duna River, at Nagymaros it exceeds 16 times, thus the Tisza water regime is more extreme than the Duna. The present study aims to analyse and compare main characteristics of the water regimes on the two rivers and those change tendencies in time on the longest period having reliable common data (1921-2012) concerning to the section of the Duna Nagymaros and Tisza Szeged gauge stations. Investigations carried out with hydrological statistical methods have been performed on a period of 92 years, further on within this entire period they have been performed on partly periods of 46 and 23 years as well. It have been analysed the linear trend of the yearly minimum and maximum water level and water discharge series, the temporal changes in the monthly frequency of the yearly extreme values occurred.
Keywords: minimum and maximum discharge, low flow periods, high flow periods.