Vízügyi Közlemények, 1995 (77. évfolyam)
3. füzet - Nováky Béla: A regionális klíma változás hidrológiai hatásai az Aföldön
314 A regionális klímaváltozás hidrológiai hatásai az Alftildön Annual runoff fluctuates substantially around the mean value. Grouping of wet and dry years can be observed. Annual runoff deceases at certain stations but the rate is not significant (Figure 8.). The coefficient of variation of annual runoff exhibits good correlation with that of the annual precipitation (Figure 9.). The time series of annual runoff can be divided into two components, the one which is determined by the climate and a residual independent of the climate (Figure 10.). With a few exceptions no significant trends can be recognized in the time series of the annual extreme values (minimum and maximum) of water level and discharge. Certain grouping and regular alternation of years with and without floods can also be identified. In the early 1990-ies lower discharges have been measured at many rivers of the Alföld, than what was measured earlier. Analyses of the tendency of water regime characteristics did not verify assumptions of climate change, although some of the results do not fully exclude this. No overall climate impact study on the surface waters of the Alföld has yet been made. Climate impact assessments were mostly restricted to areal relationships, in-time analogies and to empiricalstatistical relationships and also to certain drainage basins, investigating the average runoff conditions of longer periods (annual, seasonal and low/high flow periods) only. These investigations do not allow the drawing of fully generalizable conclusions. Effects of temperature increase on the seasonal pattern of runoff has been analyzed for the Nagymaros Station of the River Danube with a conceptual model of daily time-scale (Figure 11). Effects of climate change on annual runoff have been studied with a relationship of the form R=P exp [(a+bT))" 1, where P, T, and R the annual precipitation, annual mean temperature and the runoff, respectively and the parameter values are: a135.7 and h— 152.5. Expectable effects of precipitation changes on summer low flow have been analyzed with statistical relationships (Figure 12). Change of the climate might modify the relationship proper (Figure 13.). Effects of climate changes on the springtime high runoff and on the excess water occurrence of late winter-early spring have been assessed on the basis of graphical relationships (Figures 14 and 15) that were constructed on the basis of records of past events. In the first phase of regional climate change, associated with 5% decrease of precipitation and 0.5 °K rise of annual mean temperature, one may expect the decrease of annual runoff and of summer low flows of the rivers of the Alföld. Springtime high runoff and excess water occurrence in the end of the winter/early spring period may also be decreased, while the peak flow of the first, snow-melt, flood hydrograph may be increased. The author summarizes the main uncertainities of assessing the effects of climate change, pointing out the future tasks of research. * * * Hydrologische Auswirkungen der regionalen Klimaveränderung in der ungarischen Tiefebene von Dr.-Ing Hydr. Béla NOVÁKY. CSc. Im Beitrag wird ein bewertender Uberblick über die ungarische Fachliteratur geboten, die sich mit den klimatischen Beziehungen der Oberflächengewässer der Ungarischen Tiefebene bzw. mit den darauf ausgeübten Auswirkungen eventueller Klimaveränderungen befaßt. Der ursprüngliche Wasserhaushaltzustand der Ungarischen Tiefebene wurde durch die Ausrodungen und die im 19. Jh. begonnen Gewässerregulierungen grundlegend verändert (Bild 1). Der gegenwärtige Wasserhaushalt der Tiefebene ist ein durch tehnische Anlagen geregelter und aufrechterhaltener, künstlicher Wasserhaushalt. Das Abflußregime der Flüsse der Tiefebene wird durch das Klima des umliegenden Berglandes, der Abfluß der Flachlandgebiets aber durch das Klima der Tiefebene selbst geregelt. Zwischen dem Klima des Berglandes und des Flachlandes kann eine gewisse Gleichschaltung beobachtet werden (Bild 2).
