Predicting the Transport Time of Supersaturated Total Dissolved Gas in a Large Deep Reservoir

Abstract During dam discharge, supersaturated total dissolved gas (TDG) is generated in the plunge pool and transported downstream for a long distance. Fish living in supersaturated TDG water may suffer from gas bubble disease and even death. Investigating the transport time of supersaturated TDG helps to predict better the downstream impact range and duration of TDG supersaturation and then facilitate mitigation measures for fish in time. From another perspective, it also contributes to optimizing flood discharge management and enhancing the effectiveness of ecological management strategies. This is essential for improving the effectiveness of ecological management strategies. This study utilized a laterally averaged numerical model to investigate the factors influencing the supersaturated TDG transport time in a large deep reservoir. The Baihetan (BHT)–Xiluodu (XLD) hydropower stations were selected as the research object. Simulations under various BHT–XLD joint operation strategies were conducted to analyze the supersaturated TDG transport time in the XLD Reservoir. It is revealed that the transport time of supersaturated TDG is associated with the discharge flow and reservoir characteristics. A power function relationship was identified between the transport time and the transport distance as well as the discharge flow. The relationship among the transport time, water depth, and total volume follows a linear function. Furthermore, a quantitative relationship between the transport time and these four influencing factors was established. The results provide a scientific basis for the accurate prediction of the supersaturated TDG transport process in large deep reservoirs and the formulation of effective regulation and early warning schemes.