Hyperpycnal sediment-laden river plumes in lakes

The inflow of a river into a lake also brings other substances (sediments, nutriments, oxygen and contaminants) into the lake that are of critical importance for the water quality. This project is on sediment- laden hyperpycnal river inflows. Hyperpycnal means that the density of the river water is higher than the density of the lake water. The focus is on the flow patterns and the interactions between the flow, the sediment and the lake bottom. The current insight in hyperpycnal inflows is largely based on simplified constant-width geometries and the effect of sediment is poorly understood, which can be attributed to a lack of data from field monitoring and laboratory experiments. This project will address three research questions for a broad range of realistic geometries: (i) What are the main flow processes and on what parameters do they depend? (ii) What is the effect of sediment on these processes? (iii) What are the dominant interactions between the flow, sediment and lake bottom? This project will build on a preparatory phase that included: (i) the design of an innovative field set-up at the inflow of the Rhône River into Lake Geneva that combines measurements of velocity and sediment concentration from a moving boat with simultaneous continuous imagery of the water surface near the river inflow in the lake, and its application for data collection covering a broad range of conditions; (ii) the validation of a large-scale laboratory infrastructure for investigating hyperpycnal river inflows without sediment; (iii) the establishment of the two-phase numerical model SedFOAM for sediment-laden flows. This project will integrate and further extend the field investigation, laboratory experiments and numerical modelling. The available field data will be analysed and new data will be acquired if needed. The large-scale laboratory infrastructure will be accommodated and used for sediment-laden river inflows. Numerical experiments with the SedFoam model will generalize the outcomes of the field and laboratory investigations. The project will lead to original and innovative advances. Existing conceptualizations of hyperpycnal river inflows into lakes will be extended in two way. First, their validity range will cover a broader range of geometries. Second, they will consider interactions between the flow, the sediment, and the lake bottom. High-quality data and source codes from the field monitoring, laboratory experiments and numerical simulations will be made publicly available. A Postdoc will perform the field investigation, a PhD the laboratory experiments, and a Postdoc the numerical modelling. They will be supervised by Koen Blanckaert (TU Wien, Austria), Eletta Negretti (CNRS-LEGI, France) and Julien Chauchat (UGA/GINP-LEGI, France).