Developing a customized laboratory setup to assess sensors for real-time suspended sediment monitoring

Sedimentation challenges water reservoir operations globally, particularly for storage hydropower plants (HPPs), necessitating effective management strategies. One such strategy, fine sediment venting through turbines, though effective in managing sediment continuity, increases hydro-abrasive erosion on turbines due to the additional sediment load. Hence, there is a need for precise real-time monitoring of suspended sediments. Existing systems, however, often lack the capability to measure suspended sediment mass concentration (SSC) and particle size distribution (PSD) with low uncertainty, particularly for coarser particles, such as sand. To maintain particles with sizes up to 2 mm in suspension, which is the size of particles vented through the power waterways of the turbines, this study developed a customized laboratory setup with an upward flow column and a closed pump circuit. To foster a homogeneous SSC distribution, the setup was hydraulically optimized by different diffusor designs at the inlet of the upward flow column. We tested particles ranging from 1500 - 2000 mu m at SSCs up to 20 gl(-1) with optical and acoustic sensors to prove our concept. First results yielded as expected mostly linear relationships between instrument outputs and nominal SSC, particularly for larger particles. This indicates that the setup allows keeping particles up to 2 mm in suspension, enabling further measurement series to better understand the impacts of sand particles in combination with silt on sensor performance. This is crucial for enhancing suspended sediment monitoring capabilities for fine sediment venting at HPPs.