Influence of turbidity currents on reservoir sedimentation - venting through a bottom outlet as an alternative

Sedimentation is an increasing problem in Alpine reservoirs. It leads to a reduction of storage capacities of reservoirs on one hand and might endanger the operating equipment like bottom outlets as well as power conduit inlets and gates on the other hand. The presented measurements are a part of the project Influence of turbidity currents on reservoir sedimentation – venting through a bottom outlet as an alternative. The performed measurements, which should be showcased in this contribution, are the determination of the velocity distribution (ADCM), turbidity, temperature and conductivity in two locations in the reservoir Großsölk in Austria. The velocity profilings have been carried out with two down looking SONTEK Argonaut XR. The distance between the Argonauts and the bottom is about 8 meters. The other probes have been measured at the same locations. Besides the measurements in the reservoir additional probes are installed upstream and downstream of the reservoir. The first measurements show promising results. It could be demonstrated that during floods turbidity currents follow the Thalweg until they reach the dam, although the turbine was in operation and the bottom outlet was closed. This shows that a venting of turbidity currents might be possible during higher floods when the bottom outlet will be opened. This project was funded by the Austrian Research Council (Österreichische Forschungsförderungsgesellschaft mbH -FFG) within the framework of the BRIDGE-Programme.