Abstract
Rivers are under increasing pressure from anthropogenic impacts with incremental dam construction, experiencing global and regional alteration due to river disconnectivity, flow regulation, and sediment reduction. Assessing the cumulative impacts of dams on river disconnectivity in large river basins can help us better understand how humans disintegrate river systems and change the natural flow regimes. Using the Yangtze basin as the study area, this study employed three modified metrics (river connectivity index, RCI; basin disconnectivity index, BDI; and the degree of regulation for each river section, DOR) to evaluate the cumulative impacts on river disconnectivity over the past 50 years. The results indicated that the Yangtze had experienced strong alterations, despite varying degrees and spatial patterns. Among the major tributaries, the greatest impact (lowest RCI value) happened in the Wu tributary basin due to the construction of cascade dams on the main stem of the tributary, while the lowest impact (highest RCI value) happened in the Fu tributary basin, which still has no dams on its main stem. Collectively, rivers in the upper Yangtze reaches experienced more serious disturbances than their counterparts in the middle and lower reaches. The BDI results displayed that a substantial part of the Yangtze River, especially the Wu, Min, Jialing, and Yuan tributaries, only maintain connectivity among one to three representative river systems. No part of the Yangtze connects all the 12 representative river systems. This study also revealed that small dams can also exert significant impacts in flow regulation on regional river systems through their sheer number and density. The study results can help promote more environmentally sustainable river management policies in the Yangtze basin.
Highlights
Rapid population growth and economic development are tightly coupled with a surge in demand energy and water resources
Based on the above discussion, this study, using the Yangtze River case study, tried to (a) set up a basic framework for assessing the impacts of large dams on river disconnectivity based on changes in sediment load and water discharge, which can be considered as an initial attempt to investigate what can be done with simple and applicable river disconnectivity analyses; (b) develop a new model to quantify the cumulative impacts of small dams on water regulation in the Yangtze River basin; and (c) investigate the current condition of the Yangtze River and provide an important reference for policymakers for future dam development in the Yangtze River basin
Annual precipitation data from 220 meteorological stations (163 stations located in the Yangtze River basin, 57 stations located outside the basin but in the vicinity of the basin) were extracted from a 728-station precipitation dataset released by the China Meteorological Data Sharing Service System
Summary
Rapid population growth and economic development are tightly coupled with a surge in demand energy and water resources. Numerous small dams constructed in the Yangtze basin intercept natural flows, which was initially delivered downstream where it is again available for river systems, but the magnitude of environmental changes to water resources resulting from more than 42,000 small dams are still not well evaluated. They tend to avoid the more obvious environmental and social disruption of large projects, their cumulative impacts on the Yangtze River are still unknown to the public. Based on the above discussion, this study, using the Yangtze River case study, tried to (a) set up a basic framework for assessing the impacts of large dams on river disconnectivity based on changes in sediment load and water discharge, which can be considered as an initial attempt to investigate what can be done with simple and applicable river disconnectivity analyses; (b) develop a new model to quantify the cumulative impacts of small dams on water regulation in the Yangtze River basin; and (c) investigate the current condition of the Yangtze River and provide an important reference for policymakers for future dam development in the Yangtze River basin
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
