First Sediment Transport Measurements at the Vjosa River in Albania - Ecological Implications and Limits for Future Hydropower Use

The Vjosa River in Albania is one of Europe’s last free flowing wild rivers, which by its spatial extent is unique in Europe despite of Russia. Coming from Greece its course of 270 km comprises a mosaic of various habitats and forms a highly dynamic natural ecosystem for flora and fauna that has largely disappeared from other European rivers. Almost all of the tributaries in the basin are laterally and longitudinally well connected, which forms the basis for a good hydromorphological status attaining an outstanding situation compared to other European rivers of this size.

However, due to economic interests, this sensitive and heterogeneous river system is under the pressure of human impacts. 38 hydropower plants are planned to be built in the whole catchment, 8 of which are projected at the Vjosa itself. Alltough hydropower has the reputation of being clean and sustainable this anthropogenic interference goes along with irrecoverable changes for the whole river system and its biosphere, facing e.g. reservoir flushing, hydropeaking, colmation, loss of habitats and connectivity.

Not only ecological, but also economic issues have to be taken into account in this context. When dealing with sedimentation of reservoirs, river bed incision downstream of the dams as well as coastal erosion, knowledge about sediment transport yields is indispensible. Therefore for the first time sediment transport in the Vjosa River was addressed within this study in order to subsequently characterize transported sediments and calculate sediment yields over longer periods of time. Direct bed load transport measurements were performed using a basket sampler from a bridge near Pocem at different hydrological situations. In order to quantify sediment yields, discharge measurements were performed to derive rating curves.

First results show that initiation of motion takes place at a discharge of 300 m³s^-1 with a measured bed load transport of 1 kgs^-1. Transport intensity then and rises strongly with discharge, leading to a highly morphologically active system. The measurements within this study are a first and important information and form the basis for further ecological as well as economic considerations on the Vjosa. The knowledge about sediment transport processes and hydromorphological monitoring shall contribute to find sustainable solutions for the unique ecosystem Vjosa. Moreover, based on the presented study it is aimed to derived sediment monitoring standards for requested environmental impact assessments (EIAs) for hydropower projects in the entire Balkan region.