Determining Critical Thresholds of Environmental Flow Restoration Based on Planktonic Index of Biotic Integrity (P−IBI): A Case Study in the Typical Tributaries of Poyang Lake

Abstract

Hydropower construction and climate change have aggravated river hydrological changes, which have reduced the water flow regime in the Ruhe River Basin. The reduced flow of the river seriously affected the water supply of nearby residents and the operation of the river ecosystem. Therefore, in order to alleviate the contradiction between water use for hydropower facilities and environmental water use, the urgent need is to explore the ecological flow-threshold of rivers. This study took the Fuhe River Basin as the research object, and summarized the monitoring data of eight hydrological stations from recent decades. Based on this, we explored the response law of P−IBI and flow, a tool to quickly measure the health of the ecosystem. Through the response relationship between alterations in environmental factors of the river and phytoplankton index of biotic integrity (P−IBI), it was determined that environmental flow was the dominant influencing factor of P−IBI. According to P−IBI, the threshold of environmental discharge in the Fuhe River was limited to 273~826.8 m3/s. This study established a regulatory framework for the river flow of large rivers by constructing P−IBI and determining the critical thresholds of environmental flow by constraining the constitution. These results provide a theoretical basis for better planning and improvement of river ecosystem restoration and river utilization.

Development and Evaluation of the Plankton Biological Integrity Index (P-IBI) in Dry and Wet Seasons for Dianchi Lake

“…We used the ratio standardization method, one of the most accurate and effective [39,40]. For the indicators that decrease with stronger interference, the 95% quantile of all parameter samples was the expected value, and the indicator score was equal to the parameter value divided by the expected value.…”

“…It is possible that the difference between the TLI and P-IBI scores is due to variations in the classification of key parameters. The aforementioned method had also been employed to evaluate lakes situated in the Yangtze River [38] and Poyang Lake [39]. By reducing errors caused by spatial and temporal changes across various hydrological periods, the P-IBI represents a more scientifically rigorous technique for assessing the health of water bodies over extended time frames.…”