Vízügyi Közlemények, 1997 (79. évfolyam)

1. füzet - Antal Emánuel: A Tisza szabályozásának éghajlatmódosító szerepe

46 Antal Emánuel Climate modifying effect of the regulation of the River Tisza by Dr. Emánuel ANTAL, Meteorologist, С. Sc. The general public also the scientific society became concerned several times with drought periods of the past 100-150 years, blaming sometimes seriously the regulation works of the River Tisza and the drying out of floodplains and wetlands for the occurrence of drought. This disbelief was repeatedly propagated also in this century, stating that the climate of the Hungarian Great Plains Alföld has been changed by the flood and excess water control activities (Figure 1.), causing the desertification of this area. Moreover some sources stated that the annual precipitation was reduced by as much as 200 mm. In the present study the author reviews those climatic investigations and publications which have, ever since the middle of the past century, disproved this misbelief. For the investigation of the climate modifying effect of the regulation works of the River Tisza the temperature time series of various periods (Figure 2., 4., 9., and 10.) and partly the precipitation records (Figures 3., 5., 6. and 10.) have been utilized. Changes in the time series, which could be related unambiguously to the regulation works of the Tisza can be found neither in the temperature, nor in the precipitation records. Although there is a slight rising trend in the temperature record (Figure 10.) in the national average value, it not the consequence of the regulation of the River Tisza, but it is due to the global warming tendency as shown in Figure 8. Annual precipitation has also been decreasing (Figure 6.) in the past decades. This decreasing trend, however, characterizes not only the flood prone (flood protected) areas but the entire Carpathian Basin (Figure 5.). It can be thus unambiguously stated that decreasing precipitation trends are not the consequences of the regulation of the River Tisza, but regional phenomena of larger scale. Calculations made on the total water budget of the atmosphere (Figure 7.) can not justify the effect of flood control activities on precipitation, either (Table I.). As a final conclusion the author stated, that water regulation works of the past century had favourable and unfavourable climatic effects, but it can not be numerically shown, that there are climate changes which involve the Hungarian Plains Alföld too ("drying out", "desertification"). The only fact which can be demonstrated is that the local climate, or the microclimate system, of former water prone areas has been modified as the consequence of flood regulation activities. Auswirkung der Theißregulierung auf das Klima von Dr.-Meteor. Emánuel ANTAL, CSc. Kam es in den vergangenen 100-150 Jahren zu bedeutenderen Trockenperioden, haben sich damit nicht nur die Volksmeinung, sondern auch die wissenschaftlichen Kreisen beschäftigt. Dabei gab es immer ganz ernst gemeinte Ansichten, nach welchen die Hauptursachen der Dürreperioden die Theißregulierung, die Trockenlegung der Flutgebiete und der Sümpfe wären. Sogar in unserem Jahrhundert wurde mehrere Male der Irrwahn geäußert, das Klima der Großen Ungarischen Tiefebene sei durch die Hochwasserschutz- und Entwässerungsmaßnahmen im Theißgebiet (Bild 1) verändert worden, was zu ihrer allmählichen Verödung geführt hätte. Es wurde sogar behauptet, daß diese Maßnahmen die jährliche Niederschlagssumme um mindestens 200 mm verringert hätten. Die vorliegende Studie bietet einen Überblick über die Untersuchungen und Veröffentlichungen, welche seit Mitte des vorigen Jahrhunderts zur Widerlegung dieses Aberglaubens erschienen sind. Als Grundlagen für die Untersuchung der klimaändernden Rolle der Theißregulierung dienten