Author(s): Xiaoqiang Chen; Yuhong Gao; Shiguo Xu
Keywords: No Keywords
Abstract: Heavy rainfall event is an important reason resulting in the destruction of the reservoir situation during the flood season. An intensive sampling campaign was conducted in the Biliuhe reservoir, which located in Dalian city, China, after the heavy rainfall on August 2,2017. The results show that rainfall runoff, containing a large amount of particulate nutrients and sediments, entered the reservoir and took the shape of the density flow. The density flow layer was created under the water between transition zones and the zones before the dam, and the thickness of interflow reached up to 10m before the dam. Water quality in reservoir was strongly affect by the density flow. The concentrations of total phosphorus (TP) and total nitrogen (TN) were increased significantly due to the intrusion of density flow in the middle and lower of water, with the peak values of TN and TP were1.6 and 4.3 times higher than that in normal condition. It leads to consequence in serious water pollution with short period. The seasonal thermal stratification layer was destroyed due to the intrusion of density flow existing in the bottom of reservoir. An obvious DO concentration was observed at the upstream the reservoir, the dissolved methane was decreased with the aerobic state. The rapid conversion of the aerobic state to anaerobic state was carried out at the high depth of water more than 25m due to the density flow with the depth of 5-15m, it resulted into an enormous increase of dissolved methane to 690 times saturability. The dissolved nitrous oxide in reservoir also reached at the maximum levels with the rapid transform of water environment. The heavy rainfall event resulting the density flow not only lead to the deterioration of water quality, and also drive the production of the greenhouse gases in reservoir.