Developing a baseline and tools for the future assessment of the ecological status of rivers within the Three Gorges Reservoir catchment, China

Abstract

To comprehensively understand the current ecological status of rivers within Three Gorges Reservoir catchment (TGRC), and provide a baseline and tools for the future assessment, macroinvertebrates from 26 tributaries were collected in April, 2010, and a multi-metric index based on macroinvertebrates (SXMMI) and the corresponding rating criteria for assessment were established. Five metrics, including percent model affinity (PMA), percentage of individuals of 1st dominant taxa (Dom01Pct), Hilsenhoff biotic index (HBI), total taxa number (TotalTax), and the taxa number of Ephemeroptera, Plecoptera, and Trichoptera (EPTTax) were selected to join into the final index system by several steps. A combination of an “a priori” (experts judgment) and an “a posteriori” (PMA) approach was used to improve the accuracy of pre-classification. According to the results of assessment, the ecological status of the 26 tributaries in TGRC was not good; the rates high and good were relatively low, and there was a trend the ecological status in most tributaries deteriorates from upstream to downstream. The results of multivariate analysis and relationships among the SXMMI, the latent environment gradient, and abiotic and biotic parameters indicated that our final index was a robust assessment tool. In future, the SXMMI should be refined and verified with additional data.