Comparison of different methods for modelling total dissolved gas transportation downstream of the hydropower plant Brokke at river Otra

In Norway, downstream of Brokke, which is a high-head hydropower plant, supersaturated dissolved gas is released into River Otra. This supersaturated dissolved gas is a potential threat to aquatic life. For this reason, the natural degassing process during transport has been investigated in this project for the downstream river reach of the hydropower plant Brokke. The aim of this master’s project is to find a suitable model in order to improve the simulations of the total dissolved gas (TDG) transport. Therefore, different flow scenarios (with 138% to 172% TDG content) using three different methods have been simulated. The results show that the Finite Difference Method performs the best for the scope of the study. The limitations of the Finite Difference Method are connected to the calibration and the resolution. These limitations need to be reduced in further studies, and combined with additional field measurements.