Baiyinbaoligao, XU Feng-ran, CHEN Xing-ru, CHEN Wen-xue (China Institute of Water Resources and Hydropower Research, Beijing 100038, China)

Abstract: During sediment flushing of the Xiaolangdi Reservoir in the Yellow River, fish deaths were usually observed in downstream river reach. Explains for the phenomenon were studied by field survey and laboratory experiments. In the process of sediment flushing in 2010, high concentrated sediment flow played an important role in the destruction of habitat. Investigation showed 11 fish species from 5 families and 5 orders were affected by the lethal concentration. It could be demonstrated, by variation process of sediment concentration and dissolved oxygen from field and laboratory study, that high concentrated fine sediment flow, which caused the clogging of fish gills, is one of the dominant reasons for fish mortality. When the sediment content was higher than 80kg/m 3, the dissolved oxygen concentration fell below 2mg/L which was lower than the limit for fish living requirements. In this circumstance, fish went to death in a short period caused by hypoxia. While sediment content was lower than 60kg/m 3, by survey and experience, there were no deaths of fish in downstream river reach. There is a direct correlation between DO and sediment concentration downstream of the reservoir during sediment release period, which means that DO would decrease with the increase of sediment concentration. Thus, through reasonable and proper operation, sediment concentration and duration of dam flushing could be regulated to relieve adverse effects on fish.

Key words: sediment flushing, sediment concentration, dissolved oxygen, fish

Published in: Journal of Hydraulic Engineering, Vol. 43, No. 10, 2012