Experimental setup for flow and sediment flux characterization at desanding facilities

Desanding facilities are located between the water intake and the penstock of medium and high-head hydroelectric power plants to avoid the entrance of suspended sediments into the penstock and therefore to reduce hydro-abrasion at turbine parts. This paper focusses on the selection and description of measurement instrumentation to characterize flow and sediment flux at desanding facilities with high spatial and temporal resolution. The selection criteria for the instrumentation are highlighted and the capabilities and limitations of the devices and techniques are described. The modular design of mounting system carrying the instrumentation allows for measurement under several structural constraints. The chosen concept for data acquisition in terms of measurement grid, measurement duration and sampling frequency provides high resolution data of flow quantities and sediment flux. For reliable quantification of sediment fluxes, in-line measurements of turbidity are correlated with suspended sediment concentration obtained by water sampling, also considering density and temperature. Selected findings from the field measurement campaign at two sites in Switzerland are presented and discussed. The employed experimental setup proved to be appropriate and reliable to characterize the flow field and sediment fluxes in desanding facilities at high resolutions.