Bioindicator Assessment Framework of River Ecosystem Health and the Detection of Factors Influencing the Health of the Huai River Basin, China

Abstract

River ecosystem health assessments are a hot topic in global water resources management. The Huai River Basin is a representative basin faced with serious environmental problems due to high water pollution and numerous water projects. Comprehensive investigation of the factors affecting river ecosystem health is an urgent precursor to the successful management of the Huai River Basin. Based on a series of aquatic ecosystem indicators, monitoring, and standards, such as phytoplankton, zooplankton, and benthic macroinvertebrate data, an assessment framework of river ecosystem health is proposed using a multistep gray correlation evaluation method. Environmental impact factors including climate, land cover, edaphic factors, hydrology, water projects, and water quality were identified using the Kruskal-Wallis test and distance-based redundancy analysis method. The ecosystem was found to be subhealthy with 44% (31/71) of sites in a healthy condition, 51% (36/71) subhealthy, and 5% (4/71) unhealthy. Climate and hydrology were the dominant factors that together contributed 37.5, 24.1, and 6.9% of the variation in phytoplankton, zooplankton, and benthic macroinvertebrates, respectively. The main variables affecting variation were minimum temperature, relative humidity, solar radiation, and the magnitude, frequency, duration, and timing of monthly runoff. Together, these variables explained 24.5% of the variation in the ecosystem health of the whole river. Thus, to improve river ecosystem health in the basin, the regulation of dams and sluices should give priority to ecological outcomes, and the threat of climate change should not be underestimated. This paper provides a blueprint for ongoing ecological monitoring and restoration programs in China, and is expected to be a successful case and reference to transition from water quantity management to river health management in the Huai River Basin.