Analyzing spatial and temporal variations in the flow regime changes in the Yangtze River using a framework combing the eco-flow metrics and IHA metrics

Abstract:

Changes in the flow regime has significant impact on the aquatic ecosystem in the Yangtze River. We proposed an efficient framework that combined the eco-flow metrics (ecosurplus and ecodeficit) and Indicators of Hydrologic Alteration (IHA) metrics to investigate the flow regime changes in the Yangtze River. A distributed hydrological model was used to quantitatively separate the impacts of human activity and climate variation on flow regime changes. The results showed that the flow regime changes showed significant differences between the main channel and major tributaries, and also differed from the upper Reach to the middle and lower reach. In general, human activities had larger impact on the flow regime pin the upper reach than in the middle and lower reach. Autumn streamflow significantly decreased in the main channel and in the tributaries of the upper Yangtze River due to the impact of climate change and human activity. The reservoir operation resulted in a significant increase in winter streamflow in the main channel and in the Minjiang, Wujiang, and Hanjiang tributaries. Reservoir operation and climate variation were the main causes for the significant reduction in low flow pulse duration in the middle reach of the Yangtze River. Reservoir operation also led to an increase in the frequency of low flow pulses, an increase in the frequency of flow variation and a decrease in the rate of rising flow in most of the tributaries. The ecological impact of flow regime changes in the Yangtze River need further studies in future work.