Presenter: Dr. Guangdong Wu, Changjiang River Scientific Research Institute
Sub-theme
4. Supporting Aquatic Ecosystem Health and Functions
Topic
4-2. Maintenance and restoration of the river basin eco-hydrological process
Body
The source region of Yangtze River (SRYR) is located in the hinterland of the Qinghai-Tibet Plateau and is an important part of China's ecological security barrier. The ecosystem in the source area has a simple structure, poor resilience and low self-recovery ability, and once the ecological environment is damaged, it may lead to ecosystem collapse. Baseflow as a critical component of watershed water cycle can reflect the changes in underground water storage, which plays an important role in sustaining the ecosystem during dry seasons in the SRYR. Because of climate change, the temperature and streamflow have been reported to rise largely in past decades in the SRYR, but the changes in baseflow have not been completely understood. The objective of this study is thus to indentify the dynamic characteristics and attributions of baseflow in the SRYR. Daily streamflow data for the Zhimenda station was selected for baseflow separation. A total of 9 baseflow separation methods were chosen, and based on their performance, the Eckhardt method was employed to obtain a baseflow time series. We systematically characterized the temporal patterns of baseflow through statistical analyses, and subsequently investigated the response to climate change and human activities. It is shown that a remarkable increasing trend in baseflow was identified using the Mann-Kendall Trend Test. Generalised Additive Models for Location, Scale and Shape (GAMLSS) statistical analysis shows historical baseflow is related to climate parameters. Besides, the increases in baseflow in the SRYR are more sensitive to temperature and precipitation variation compared to evapotranspiration, which exhibits two months of time lag, and the sensibility and hysteresis varies with different seasons. The warming-associated snow and glacier melting have a huge influence on the increase in baseflow. Our results also indicate that climate change rather than human activities dominants the variation in baseflow in the SRYR.