Experimental study on total dissolved gas supersaturation in water

More and more high dams have been constructed and operated in China.The total dissolved gas (TDG) supersaturation caused by dam discharge leads to gas bubble disease or even death of fish.Through a series of experiments,the conditions and requirements of supersaturated TDG generation were examined in this study.The results show that pressure (water depth),aeration,and bubble dissolution time are required for supersaturated TDG generation,and the air-water contact area and turbulence intensity are the main factors that affect the generation rate of supersaturated TDG.The TDG supersaturation levels can be reduced by discharging water to shallow shoals downstream of the dam or using negative pressure pipelines.Furthermore,the TDG supersaturation levels in stilling basins have no direct relationship with those in reservoirs.These results are of great importance for further research on the prediction of supersaturated TDG generation caused by dam discharge and aquatic protection.