Author(s): Xiao Yu, Qian Zhang, Yisi Zhu Ge, Qiang Du, Guoqiang Li
Linked Author(s): Xiao Yu
Keywords: Dahuofang Reservoir, thermal stratification, water quality, dissolved oxygen
Abstract: According to the design parameters of Dahuofang Reservoir, the water temperature structure of the reservoir is thermal stratification. In order to study the correlation between stratification and water-quality variance, vertical water temperature and water-quality monitoring in front of the dam was carried out in May, July and September 2010~2012. The result showed that water-quality of surface water was good and stable in the reservoir and could reach Grade II of the National Surface Water Quality Standards. Since the reservoir was operated under a low water level during 2010~2012, thermally stratified period only occurred in summer. The steady temperature gradient could control the water environment of the reservoir, which effectively restricted oxygen transfer and exchange among the vertical water layers. In summer, dissolver oxygen (DO) in surface water was high and over 7mg/l, even to its supersaturation. DO in bottom water was even lower than 4mg/l, which could not meet Grade III water quality. In autumn, the cold water on surface settled down which strengthened the vertical mixture of the reservoir, so DO in surface water reached the lowest all over the year. If the reservoir is operated in a high level for a long time, the time of thermal stratification in Dahuofang Reservoir will increase, thus leading to further decrease of DO in bottom water. It may lead to the formation of hypoxic environment for bottom water which will cause pollutants such as Fe, Mn, H2S to release from sediments. Then, with the strengthening of the vertical mixture of the reservoir in autumn, the pollutant in bottom water will pollute the whole reservoir and cause abrupt water pollution accident which will have a direct threat of the water supply security
Year: 2017