Vízügyi Közlemények, 1996 (78. évfolyam)
1. füzet - Szlávik L.-Galbáts Z.-Kiss A.: Az 1995. decemberi Körös-völgyi árvíz és a szükségtározások hidrológiai elemzése és értékelése
104 Szlávi к L.—Galbáts Z Kiss A. and snowmelt, are presented. The water level time series of the river Sebes-Körös has been influenced by the operation of a series of mountainous and hilly reservoirs (Table /.). The ever highest water stages of the gauging stations of the Körös River System are shown in Table II, along with those of the year 1995. Slope conditions and the intensity of flooding are shown in Table III. Results of intensified discharge measurements during the flood have been summarized in Figures 6-9. The highest measured and calculated discharges of the Körös system are presented in Table IV. Discharge rating curves indicate well the "flood loop phenomenon " that had been first described by Sámuel Hirschfeld (Hajós), as well as the effects of the emergency reservoirs. The most important basic data of the operation of emergency reservoirs are presented in Table V. The effects of emergency reservoirs on water stages and discharges are illustrated by the actual and estimated water level time series of discharge measuring stations, of which the time series of the station of Gyula (Fig. 10.), Remete (Fig. 11.) and Békés (Fig. 12.) are presented as examples. In the history of this flooding event of the Körös Valley and of that of the successful flood defence operations the emergency reservoirs of Mályvád and Mérges played a crucial role. The time and extent of their opening had decisively determined the peaking of the flood. Therefore the authors present the detailed analysis of the operation of these emergency reservoirs (Figures 13. and 14.). Water volumes carried by the flood have been determined with the help of the discharges in excess of the Stage I. Flood level. In the light of the summary presented in Table VI. the flood of 1995 ranked as the 5 th in line with its flood volumes of 144 million m 3 and 133 million m 3 of Remete and Gyula stations, respectively. On the basis of the estimated flood hydrographs (Table VII.) the flood of 1995 was, in terms of water stages, the second largest at remete, Dobos and Békés, while it could have been the largest at Gyula with the estimated water stage of 8.86 m, exceeding the ever measured highest level of 7.94 m, if the Mályvád emergency storage scheme had not been opened. The authors present the evaluation of water levels forecasts that had played a substantial role in the operation of the emergency reservoirs. Figures 15. and 16. illustrate the reliability of the forecasts made. As a final conclusion it is stated that both of the forecasts made for the Fekete-Körös (Remete) and Fehér-Körös (Gyula) have proved to be 100% reliable. Extreme floods in the month december are rare in the Körös river system. The last december ice-flood occurred on the 23rd December, 1925, causing several dike ruptures but only relatively little damage. Highest measured flood levels are increasing steadily and substantially (the increase at station Ant of the Fekete-Körös was 1.72 m between 1966 and 1981) and therefore the development of the system of emergency storage reservoirs is needed, along with the improvement of their operation. In respect to the operation of emergency reservoirs the most important factors are the expansion of the network of tele-transmitting water level gauges and the establishment of a special hydrographic monitoring and information forwarding system. In order to improve the reliability of forecasts one should investigate, in the framework of bilateral cooperation in the field of transboundary rivers, the effects of the mountainous reservoirs of Romania on the fate of the flood hydrographs.
