Management of reservoir sedimentation due to turbidity currents by technical measures

The growing demand of water and food all over the world can be satisfied in arid regions only by artificial reservoirs. They supply water for drinking and irrigation, but may be endangered by sedimentation. Without effective measures their sustainability is questioned. Deposits of sediments not only affect the loss of life storage, but also the proper functioning of outlet structures such as intakes and bottom outlets. In narrow reservoirs with rather steep bottom slopes, turbidity currents are often the main process in the reservoir sedimentation. The highly sediment-laden density current not only transports the sediments along the thalweg to the dam but also erodes already deposited fine sediments. Technical measures to influence and govern turbidity currents are therefore very important in view of a sustainable reservoir sedimentation management. To control the sedimentation within the reservoir, the effects of obstacles, screens, water jets and bubble curtains on the turbidity current were investigated with physical experiments and numerical simulations. In the physical experiments, measurements of the spatial and temporal evolution of the deposits, of vertical velocity profiles and of the front velocities were recorded. The investigated measureswere simulated using a three-dimensional numerical model, based on the flowsolverCFX-4.4. The investigations showed that turbidity currents could be influenced effectively by properly designed constructive measures. Based on the results of the physical experiments and numerical simulations, some design recommendations as rules of thumb are given for the application of the investigated measures.