Vízügyi Közlemények, 2000 (82. évfolyam)

2. füzet - Hankó Zoltán: Gondolatok a Duna Szap és Szob közötti szakaszának fejlesztéséről

Gondolatok a Duna Szap és Szob közötti szakaszának fejlesztéséről 299 All these changes were substantially modified after 1992, when Slovakia put the modified upper part of the GNV system, the Dunacsúny-Bös power-canal type hydropower scheme into operation. The study of Rákóczi (2000) states in a summarising way that upon the launching of the operation of the upper subsystem of the GNV system in 1992 the natural supply of bed-load of channel forming capacity, has ceased. On the other hand the rejoining of the tail-water canal of the hydropower scheme at Szap (r.km 1811) created flow conditions, which differed from the previous ones to a large extent and caused considerable bank and channel erosion. This latter resulted in the launching of a „bed-load wave", which crawled towards downstream in a flattening way. This process lasts until a natural balance is reached between the erosion and the sediment transport. The conditions are further complicated by the upstream-reach character of the Danube channel between Gönyü and Szob (r.km 1791-1708), because natural channel-erosion and the excessive industrial dredging together resulted in a channel erosion (scouring) in which more material has left the channel in concern than what arrived from the upstream and thus the channel is sinking. All these problems were to be resolved in the impounded headwaters of the Nagymaros dam. The resolution of the Hungarian Parliament (MO 1991), however, excluded the option of river canalisation and thus the only alternative which remained for the solution of these problems is to be achieved by river training. The most important nature conservation objectives to be achieved are the regulation of groundwater levels in the alluvial zone of the river (including the protection of bank-filtered drinking water resources) and the provision of adequate supply of water to the braided side-arm system of the river (this latter is the highest nature-conservation objective). The most important social objectives are: release of design flood flows at water levels not exceeding the respective water surface profile and assurance of conditions required by international navigation. Plans and designs made in the past quarter of this century may serve as the basis for the design and planning of the activities mentioned above, these are: channel survey of 1975; plans for the canalisation of the river (1977); environmental rehabilitation and navigation development without impoundment ( 1992/96); river regulation plans of 1994—1996. These plans might form the basis of the initial steps in forming the concept of handling this new situation. Following the guidance of the Office of the Prime-minister and the Ministry for External Affairs the conceptual plan of the development of the common Hungarian-Slovak Danube border section (between Rajka and Szob) was made on the basis of the plans mentioned above. This was handed over to the Slovak Government in December, 1999, as a material forming the basis of further negotiations concerning the problems of the GNV project. This material hardly deals (downstream of Szap) with anything else than the rehabilitation of side river arms and thus can hardly form the basis of further planning and development. The release of flood imposes further problems. The height of the levee is too low in the vicinity of Esztergom and on the Slovak side a levee was constructed that meets the safety demands of the impounded river reach and has no respective counter-levee on the Hungarian side. Requirements of international navigation cannot be meet with river training facilities (although the plan outlines a much disputable solution for the handling of the problems of low-flow fords, Figure 4). The question of groundwater level regulation has not been dealt with (and thus the protection of bank-filtered drinking water resources was neglected). Consequently this plan meets neither the requirements of the Parliament Resolution (MO 1991) nor is it able to comply with the guidelines of the Parliamentary Assembly of the Counci' of Europe (ETPK 1994), not mentioning the non-compliance with the judgement of the Intet • national Court of Justice (ICJ 1997). * * *