Ecosystem restoration at Fundu Mare Island in the Inner Danube Delta near Braila (Romania) - Hydrodynamic optimisation

摘要

Within the last century, the extensive implementation of engineering measures in European rivers has caused significant changes in river hydrology, water quality and local ecology, inducing major impact on the environment of wetlands. As a result, degradation of habitat quality in combination with loss of biodiversity are the major consequences. Along the Romanian Danube River, large parts of former wetlands, lakes and braided river reaches have disappeared, with the wetland Fundu Mare Island representing one of its last remains. In recent years, a reduction of the water levels and willow encroachment into the aquatic zone were observed, affecting the high biological diversity of the island. In order to protect biodiversity, the implementation of restoration measures in Fundu Mare Island is investigated within the project Restoration of the aquatic and terrestrial ecosystems complex, from Fundu Mare Island, part of the Small Wetland of Brăila funded by EEA-grants. As part of the project, this work aims at the investigation of a number of restoration scenarios that allow conservation of biodiversity. The implementation of a two-dimensional numerical model was examined in Delft3D. Due to the time restrictions of the thesis and unforeseen problems during model calibration, a general investigation by the application of a simplified water balance approach was applied. Based on the results, it can be concluded that the water levels on the island can be positively influenced by the implementation of weirs. In order to meet the requirements regarding security, hydrological uncertainty, and ecological demands, the installation of the bag weir is recommended. The demands of fish in the area can be met by seasonal opening of the channels on the island to enhance water exchange and provide connectivity between Fundu Mare Island and the Danube. However, further research needs to be carried out to analyse the feasibility of the implementation with regard to the simplifications made in this approach.