Vízügyi Közlemények, 2002 (84. évfolyam)
3. füzet - Pálfai Imre: Magyarország aszályossági zónái
354 Pálfai Imre Vränceanu, AI. V.-Canarache, A.-Càrstea. S. \ State of the art of the National Drought Mitigation Strategy in Romania. Proceedings of the Central and Eastern European Workshop on Drought Mitigation (eds.: Vermes, L. and Szemessy, Á.). Budapest, 2000. * * » Drought zones of Hungary by Dr. Imre PÁLFAI C.E. The geographic conditions of Hungary are mostly favourable ones for agricultural production, but droughts represent (among other weather factors) a significant risk. The extent (strength) and spatial distribution of the droughts show significant differences among the years. However, investigating a longer period of time one is able to identify certain zones, according to the degree of drought, within which the climatic-hydrological risk factor can be represented by identical and numerically quantifiable values. In the first part of the study definitions relevant to drought are given. Next natural and anthropogenic factors, affecting the development of drought are listed, naming the numerical values of drought at the end of this section. Within this the Pál fai Aridity Index (PAD, developed by the author is described in detail. The base value of PAI (PA to) is calculatcd as the ratio of the five-month (April-August) mean temperature to the eleven-month (October-August) weighed precipitation sum. The weighing factors reflect the time-varying water demand of the vegetation, having the following values: October 0.1 , November 0.4, December-April 0.5, May 0.8, June 1.2, July 1.6 and August 0.9. The base value of the index is correctcd by three factors: The number of days of heat in comparison with the multiannual mean; the length of the precipitation-poor period of the summer (3); the depth of the groundwater table (4) below the terrain. Index PAI is obtained as the product of the PAIo and the correction factors (5). Hungarian experiences indicate that the threshold level of drought is PAI= 6.0 °C/100 mm. The various degrees of drought are as follows: PAI 6-8, moderate drought; PA! 8-10 medium drought; PAI 10-12 heavy drought; PAI 12 extremely heavy drought. I the second part of the study examples are given (on the basis of processing PAI values) for the temporal (annual) (Figure I. ) and spatial (Figures 2—5) variation of the drought. A short summary on the probability of drought in Hungary is also given. The country average PAI values are given in Table I. For the period 1931—2002. The aridity zones of Hungary arc dcscribcd in the third part of the study. A literature review of the various drought indices used in Hungary is presented by multiannual mean values (probability of occurrence values) and in spatial distribution, with several illustrating figures (Figures 6-15). The drought map of the author is based on the 10% probability of occurrence value of PAI (PAI\o%) for 73 stations (Table II). The areal distribution of these values is shown in Figure 16. Comparing this result to similar results by others (OMSZ I960 and Varga, 1984) made for the mountainous areas, having denser station network, the author identified six drought zones, taking the topographic conditions of the country also into consideration: I. drought-free zone (PAI\o%)\ II Mild-drought zone (PAI\o% 5—6); 111 Moderate drought zone (PAIio% 6-7); IV medium-drought zone (PAIio% 7-8); V. heavy-drought zone (PAI ю% 8—9) and VI. Extremely heavy drought zone (PAI ю% 9-10). The scaled-down black and white copy of the originally coloured map of 1:500 000 scale is shown in Figure / 7. The areas of the zones and their percentage ratio to the total area of the country is given in Table III.
