Vízügyi Közlemények, 1977 (59. évfolyam)
3. füzet - Kovács Dezső-Károlyi Zoltán: A magyar-jugoszláv közös érdekű Duna-szakasz jégjárásváltozásának vizsgálata
390 Kovács D. és Károlyi Z. ледовых заторов и зажоров. Согласно современным принципам регулирования Дуная усилия направлялись на обеспечение 370 —400 метровой ширины русла по зеркалу воды. Фронт регулировочных работ при этом постепенно переместился на участок г. Бая—устье Дравы (1479-1383 ркм.). Наряду с проведением согласованных регулировочных работ, начиная с 1959 г появились и первые ледоколы. Между согласованными действиями ледокольного флота и сокращением числа дней с ледоставом обнаруживается причинная связь. Современными способами регулирования русла удается снизить опасность наступления „ледовых" наводнений, обнако такие эффективные средства борьбы против льда как ледоколы и в дальнейшем остаются на вооружении на только в цельях борьбы после образования зажоров но и для предупреждения наступления их. * * * Changes in tlic iee regime over the Hungarian Danube section of common interest to Hungary anil Yugoslavia By D. Kovács—Z. Károlyi, Civ. Engrs. Reviewing a longer period it has been concluded that ice-carrying floods have occurred every 6th, or 7th year on the average over the Hungarian section of the Danube of common interest to Hungary and Yugoslavia. On the other hand, no dangerous ice jam has occured since 1956 over this section. For clearing the situation observed during the past 20 years an investigation has been performed in Hungary, the main fondings of which are presented briefly below. The variations in water temperature in the Danube and in air temperature have been examined between 1646 and 1976, and for the period 1936-1976, respectively, for the Mohács gaging section (R.St. 1447 km). The temperature of Danube water in the winter months (December, January, February) during the past 15 to 20 years was found to have been higher by round 10 per cent than in the earlier periods. During the same period an increase of about 20 per cent was observed in air temperature as well. The variations in water- and air temperature are evidently related to each other. Analysing the ice conditions over the Danube section downstream of Dunaföldvár (R.St. 1560 km), the number of days with freezing temperatures was found to be substantially the same for the periods 1936-1956 and 1956-1976. The number of days with a solid ice cover, has decreased from 511 to 176 between the two periods. A reduction of this extent cannot be attributed exclusively to a change in air temperature alone. Efforts have been made as early as the past century at minimizing the danger of ice jamming over this particular section of the Danube. The first step of river training involved the cutting of 23 bends, while several training works of rock have been constructed after the turn of the century up to 1956. Thanks to these river training works the danger of ice jam floods has decreased materially over the Danube section upstream of Baja town. The ice jam flood of 1956 has demonstrated, however, that devastating ice floods may still be triggered by the adverse coincidence of the factors involved in the development of ice phenomena. For this reason the principal objective of river training works performed between 1956 and 1976 was to improve the conveyance conditions over the channel reaches where ice jams are liable to form. The efforts were directed mainly at the establishment of the 400 to 370 m regulation width estimated on the basis of the new regulation principles. During this period river training efforts have graudally shifted to the section between Baja town and the mouth of the Dráva River (R.Sts. 1479-1383 km). Besides river training activities the fleet of ice breaking vessels has also appeared in 1959-1960. A definite relationship can be established between the concerted operation of the ice breakers and the decrease in the length of ice cover periods.
