Main Participants: Wang Yuchun, Hu Mingming, Wang Shilu, Bao Yufei, Cheng Yao, Li Shanze, Yin Shuhua, Wang Zhongjun, Zhang Panwei, Li Ang, Zhang Jiannan, Mu Zheng, Yu Yang, Wenjie, Liu Qiqi

Damming of natural rivers has become the most recent and impressive human impact that causes global change, yet the scientific understanding of the "water-storing river" process caused by cascade hydropower development is still limited. On the one hand, the research on runoff change and ecological processes of "water-storing rivers" in cascade hydropower development has not gone far enough to form any research paradigm. On the other hand, monitoring methods and scientific observation data in respect of water-storing rivers are greatly insufficient, hindering the further study on the water environment evolution of deep and large reservoirs. This research project conducted comprehensive monitoring of the "river-reservoir" system of the Lancang River, and developed the online sensing technology for deep and large reservoirs, which could effectively improve the comprehensive monitoring capacity in cascade hydropower development of rivers, in a bid to promote the coordinated, green and shared development of basin-wide hydropower development.

·   Monitoring, analysis and evaluation on the water environment and substance fluxes in the Lancang River basin based on cascade hydropower development;

·   Analysis of the key evolution processes of the water environment in Lancang River basin  based on cascade hydropower development;

·   Study on the water environment evolution and environmental effects of deep and large reservoirs on Lancang River;

·   Having revealed the environmental characteristics and their evolution mechanism of the rivers  for cascade hydropower development: clarifying that cascade hydropower development causes structural changes in water chemistry and microbial community in rivers, and demonstrating the microorganism-driven mechanism of water quality evolution in deep and large reservoirs;

·   Having illustrated the changes in substance fluxes of the rivers for cascade hydropower development and their impact: establishing an original model for estimating the biogenic  substance flux in water-storing rivers (LCR-News), formulating a mathematical expression for substance "migration-interception-conversion" in water-storing rivers; and estimating the impact of cascade hydropower development on substance fluxes in downstream rivers;

·   Assess the potential capacity of deep and large reservoirs on the Lancang River for achieving carbon neutrality: quantifying the carbon cycle and mass balance (C-Mass Balance) of river-reservoir systems and developing a reservoir carbon accounting model based on carbon cycle (DHI Ecolab);

·   Having developed the intelligent online sensing technology and equipment for the water environment of deep and large reservoirs with independent intellectual property: developing China's first 300m deep-water profile environment buoy system, which constitutes the complete set of technology and equipment for carbon flux inspections on all-inclusive reservoirs; and develop portable fixed-depth samplers and other devices for collecting water and sediment from deep and large reservoirs.

This research project has practically enhanced the comprehensive river monitoring capacity for cascade hydropower development on Lancang River, and the related outcomes are applied by water-related authorities including the Bureau of Hydrology of Yunnan and the Bureau of Hydrology of Tibet. The research findings include the system of carbon balance, migration and conversion in deep and large reservoirs as well as key parameters and interface processes of water stratification in deep and large reservoirs, providing strong support for the green development of hydropower and the watershed environmental protection, with significant socio-economic benefits.

Fig.1 The data platform for automatic buoy moni-buoy status query

Fig.2 Schematic diagram of the deep-water buoy structure and the buoy arrangements at the Nuozhadu Hydropower Station

Fig.3 Comparison of total phosphorus retention rate in different sections of Lancang River, 2012-2017

Fig.4 Correlations among unstable phosphorus, unstable iron and unstable manganese at all sampling sites