Progress in research on the impact of heavy rainfall and other hydrological processes on reservoir ecosystems

【 Instrument R&D 】In the context of global climate change, the frequency and intensity of extreme rainfall events such as heavy rainfall and heavy rain will increase, resulting in increased runoff, which can carry a large amount of suspended solids, nutrients, heavy metals and organics in the watershed and surrounding cities The entry of pollutants into the water body of the lake and reservoir will surely affect the physical and chemical processes of the lake and reservoir and the structure and function of the ecosystem.

With the support of the National Natural Science Foundation of China and the frontier key projects of the Chinese Academy of Sciences, Zhang Yunlin, a researcher from the Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, conducted a study on the impact of heavy rainfall events on the ecological environment of the reservoir in Qiandao Lake using in-situ high-frequency buoys and remote sensing data . The research results show that the water area of ​​the high turbidity area caused by heavy rainfall events in Qiandao Lake ranged from 41.3 km2 to 148.1 km2 from 2009 to 2014, and the suspended solids concentration in the estuary after rain (6.6 ± 1.0 mg/L) was significantly higher than that of rain Before (3.7 ± 1.3 mg/L). Among them, remote sensing images observed that a large rainfall event from February 21 to March 12, 2010 caused the area of ​​the Qiandao Lake high turbidity area to be as high as 148.1 km2, accounting for about a quarter of the area of ​​the reservoir, and the farthest radiation distance is up to 13.3 km. The area of ​​high turbidity area, the concentration of suspended matter and precipitation are significantly positively correlated, and increase with the increase of rainfall intensity.

The study also found that heavy rainfall can trigger the complete mixing of the water body in the estuary of Qiandao Lake, completely destroy the thermocline, and improve the dissolved oxygen level of the water body; heavy rain and moderate rain can significantly reduce the thermal stability of the water body, expand the mixing range, and simultaneously affect the surface layer. The reoxygenation of the water body has a positive promotion effect, especially the middle rain will also induce the original single-temperature thermocline structure to change to the double-temperature thermocline structure. The weakening effect of rainfall on water layering is mainly achieved by reducing the surface water temperature, increasing runoff, and increasing the intensity of physical disturbance. In addition, the observation results in the transition zone and deep water zone show that the thermal stratification state of these areas only responds to the rainstorm event obviously, and a large amount of organic matter transported from the upstream stays inside the thermocline layer and cannot be transported quickly and Decomposes, thereby consuming dissolved oxygen and worsening the chemical environment of the bottom water body.

Related research results were published in the journals of Hydrology and Hydrological Processes in the field of hydrology.