A successful restoration of a Danube side arm
In the past, the Vojčianske side arm was part of the so-called of the inland Danube delta – a system of free-flowing river branches. After the construction of the Gabčíkovo Water Works, most of the water was diverted to the hydroelectric power plant through the supply channel, which resulted in cutting off the entire branch system from the Danube. The characteristic water dynamics disappeared from the territory, sediments, gravel and nutrients stopped flowing, which was reflected in the overall quality of floodplain habitats. Some parts of the arms were covered with sediments, others were artificially filled in, and the territory was divided by a network of forest roads. This is also the case of the lower Vojčianske side arm.
In addition to the dry and poorly watered sections, the problem here was also the pipe culverts, which did not have the capacity to transfer a sufficient amount of water under the forest roads crossing the side arm. During floods, which this habitat needs for its existence, they used to get clogged. This limited the flow of water that would have washed away the sediments. In addition to the inability to transfer flow, clogged pipes also represented barriers to fish migration.
Inappropriate pipe culverts under forest roads are a thing of the past, they have been replaced by larger frame culverts.
Thanks to the excavation works, the sections of the side arm were deepened and interconnected, which will allow water to flow again in the once dry bed.
From August 2023 to January 2024, the restoration of the flow of the lower Vojčianske side arm with a total length of 3.7 km took place at this location. This is the biggest restoration of its kind within the river branch system so far. By dredging about 12,000 cubic meters of material, two branches were excavated in the place of the original riverbed, weirs A2 and A3 were rebuilt, by replacing narrow pipes with more capacious frame culverts, the riverbed was widened in narrow places, a ford was built to maintain access to the island that was created after turning the shoulder. Locally, in several places, the arm was deepened in order to create suitable wintering grounds for fish. After years, the Vojčianske side arm can be used again for the purpose of recreational sailing.
The restoration of the lower Vojčianske side arm is the result of cooperation between state and non-state organizations. As part of the LIFE Danube Floodplains project under the leadership of BROZ, departmental organizations of the Ministry of the Environment of the SR – Water Management Construction, š. p. and Water Research Institute. Their task was to prepare a study using hydrodynamic modeling, ensure the development of project documentation and perform post-implementation monitoring. In addition, the impact of diversion on target habitats and species is also monitored. The actual implementation of the works was ensured by BROZ.