Author(s): Ang Chen, Sainan Wu, Wu Miao, Xin SUI, Jingya Wen, Wanlin Jia, Chunna Liu
Keywords: Integrated Water and Sediment Regulation; Riparian ecosystems; Environmental flows; Yellow River;
Abstract: Integrated water and sediment regulation (IWSR) is critical to protecting and safeguarding the flow of the lower Yellow River since 2002. At the same time, hydrological regimes are also highly altered, and lead to increases in aquatic ecosystem degradation risk. In this paper, we systematically analyze the relevant literatures to determine the ecological effectiveness of IWSR. We assess the ecological response to IWSR over the past 20 years, highlighting the benefits and effects on riparian corridors, based on the data analysis of hydrological regime alteration, reservoir sedimentation, remote sensing images and landscape patterns in the lower Yellow River. The results show the following: (1) IWSR can help increase the sediment flushing efficiency. The river bed elevation decreased due to sediment flushing, and the risk of sediment deposition decreased. The runoff has increased compared to the same water level conditions previously. (2) The riverine wetlands in riparian corridors have been severely impacted by continuous drought in the floodplain before the implementation of IWSR, and afterward hydrological connectivity has been restored. However, hydrological regime changes which departed significantly from the historical flow have adverse effects on the components of environmental flows (e-flows), including a decrease in the rate of water condition changes, loss of large flood pulses and frequency, and degradation of high flows and overbank flows. Therefore, the risk of connectivity between wetlands and mainstream has increased. (3) The area of the Yellow River delta wetland has increased by more than 60 km2 since 2008, by implementing IWSR for estuaries. Therefore, this may be feasible for mitigating the “failing kidneys” of wetlands, and it is likely to promote dynamic vegetation successions and restore avifauna habitats. We suggest two initial ways by which to improve the quality of riparian corridors: (1) Establish the ecohydrology relationship between wetlands and e-flows releases. After this, the scientific basis for how flow releases affect riverine wetlands and how WSR affects the delta wetlands will be elucidated. (2) Determine a more systematic approach of e-flows on both natural and social requirements in the lower Yellow River, and launch an optimized operation of cascade reservoirs for multiple objectives.