Influence on fishes of dissolved gas supersaturation caused by high-dam discharging and its countermeasures

Based on the knowledge of the study achievements domestic and international and some representative projects in China, we study the generation mechanism of dissolved gas supersaturation (DGS) during high-dam discharging, discuss the relationships of DGS´s three key indexes (total dissolved gas, dissolved nitrogen and dissolved oxygen) and its varying characteristics downstream along the river, and analyze the influence on fishes of DGS. Through the analysis of the in-situ observation data, we found that among the three key indexes downstream, DO drop quickly, DN almost like TGP drop slowly; high-dam discharging has strong deadly influence on fishes living in surface water-the closer (to the dam), the heavier. Here, we also summarize and analyze the countermeasures (both engineering and non-engineering) and suggest that cascade hydropower stations operation could be an effective action to reduce the influence.