Impact Of Hydropower Station Operation In Typical Small Watersheds On The Tibetan Plateau On Carbon Composition And Flux

As an important indicator of the carbon cycle,carbon flux is an important foundation for measuring the carbon cycle in a certain period of time,and river carbon flux is not only an important component of carbon flux but also an important carrier connecting various carbon pools.And its biogeochemical properties are quite sensitive to the response of the river basin surface processes and human activities.Under the background of global change,more and more attention has been paid to the impact of the river carbon cycle of the plateau cold regions on the global carbon cycle and the regional ecological environment.However,the study on how the hydropower development in plateau environment affects the river basin carbon cycle process and the regional environment is still very limited and a research gap in China.In this study,Bodui Zangbu,a typical glacier small watershed in southeast Tibet of the Tibetan Plateau,was used as the research object.The multidisciplinary comprehensive analysis method was adopted to stabilize total suspended solids?TSS?,particulate organic carbon?POC?and dissolved inorganic carbon?DIC?.Comprehensive analysis of basic physical and chemical indicators,such as carbon isotope and water temperature,dissolved oxygen,electrical conductivity,pH value,etc.,reveals their characteristics of spatial and temporal changes,discusses the extent to which the carbon cycle of the watershed and the local environment are changed due to the hydropower development and operation.The research results can contribute to the in-depth understanding of the response-feedback mechanism of global change and human activities,and can provide scientific support for formulating reasonable hydropower development plans and river basin ecological environmental protection policies.Through the research on the impact of hydropower stations on the change of the basin's carbon flux within a glacier-shaped small watershed of the Bodui Zangbu,the following conclusions could be drawn through this thesis:1.The storage function of the hydropower station can have a significant impact on the physical and chemical properties of the river water,specifically as follows:the water temperature in the reservoir area of the hydropower station rises?an average rise of about 1°C?,the conductivity value rises?an average rise of 17s/m?,the pH value drops?an average drop of 0.3?and the range of dissolved oxygen change is reduced?about 55%of the upstream and downstream neighboring points?.2.The variation range of pCO₂ at the hydropower station is quite significant,which is 2 and 4 times of the upstream and downstream neighboring points,respectively.This indicates that reservoir storage can cause more CO₂ to escape from the atmosphere and become a carbon source of atmospheric CO₂.3.The hydropower station can form a blocking effect on TSS and POC.The POC%at the hydropower station shows a significant decrease.This decrease together with the variation of pCO₂ in the water body indicates that the reservoir storage effect has strengthened the oxidative decomposition of organic carbon in the river,thus changed the composition and flux of the organic carbon output.4.The DIC stable carbon isotope(?¹³C_DIC)of river water in the river basin is overall positive,indicating that the source of river water DIC is mainly controlled by the carbonate rock weathered in the river basin;The?¹³C_DIC value in the reservoir area is significantly more negative than that in the river channel,which further confirms that the"lakeing"effect of the hydropower station reservoir area and its changes to hydrochemistry and important carbon cycle processes.In summary,the development of hydropower stations in cold regions of the plateau can seriously affect the hydrochemical characteristics of the water body and the carbon cycle process,thereby profoundly affecting the regional and global carbon cycle and the balanced development of the ecological environment of the river basin.Plateau reservoirs/lakes have a different"lakeing"effect with other areas,i.e.organic carbon oxidative decomposition is the dominant process that changes the composition of water chemistry and carbon flux in the reservoir area,thereby increasing the CO₂ escaping flux in the reservoir area and in the carbon cycle.As China plays the role of carbon source?rather than the common role of carbon sinks in other regions?,great attention should be given in relevant research and management decisions.