Vízügyi Közlemények, 2004 (86. évfolyam)

1-2. füzet - Konecsny Károly: A 2003. évi nyári aszály kialakulásának időjárási és hidrológiai okai és vízjárási következményei a Felső-Tisza vidékén

194 Konecsny Károly Hydrological and weather causes and water-regime consequences of the summer drought of 2003 in the Upper Hungarian Tisza region by Dr. Károly KONECSNY, Hydrologist PhD. The Hungarian hydrological literature has extensively been dealing with the high-water-flood water conditions and in last decades several such works were made for the Upper Tisza River Region as well. The literature on drought is also significant and the nation wide variation and distribution of the drought index PAI of Dr. Pálfai (Pálfai, 1998, 2002, 2003a) has been investigated along with similar investigations made for the entire Carpathian Basin. In the agriculture drought hits large areas and the damages caused are higher than those of the floods and inland excess waters. In the year 2003 the weather conditions of the Upper Tisza region were characterized by extremes. The annual mean temperature in Nyíregyháza was higher than the multi-annual mean and the temperature was also higher than the average in the growing season (Table 1, Figure 1). As it is shown in Figure 2 the precipitation was lower than the mean in the area of the Environmental and Water Management Authority of the Upper Hungarian Tisza Region (Fetikövizig). If we consider the driest February-August period then the precipitation shortage, compared to the multi-annual mean, was 170 mm. In the spring snow-water was supplementing the shortage of precipitation, since in the period 5-10 February the snow-water storage of the area of Fetikövizig was 355 million m

3 and this quantity has been melted by the middle of March. On the 10

t

h of February the snow-water storage of the catchment area of the Tisza upstream of station Tokaj was 2.4 billion m

3 (Figure 3). In Nyíregyháza precipitation-free period longer than 12 days have occurred eight times in 2003 and in the period 07 February 2003 and 08 March there was no precipitation for 30 days (Figure 4.). In the growing season there was by 35-85% less precipitation in the area of Fetikövizig than the multi-annual mean (Figure 5). The precipitation time series of the growing season (months 04-09) of Nyíregyháza shows a decreasing linear trend and the low precipitation sum of the growing season of 2003 well suits this general scheme (Figure 6). Comparing the monthly pan-evaporation values (of the period April-October) of Császárszállás to the multi-annual mean one finds that it was in every month higher than the mean and the cumulated value of the seven months was 230 mm. The pan evaporation value of June (170 mm) was extremely high (Figure 7). In the growing season of 2003 the evaporation sum was 813 mm, while in the same period the precipitation was 21 mm, that is the total water shortage was 603 mm. The extent of the drought was evaluated by the index PAI. This index takes both meteorological factors and water regime factors into consideration. Values of PAI indicate small drought when in the range 6-8, medium when 8-10, severe when 10-12 and extremely high when >12. In Pátyod the ever highest PAI value of 10.4 was determined for the year 2003 (Figure 8).