Assessment Of Typical River Habitat Quality In Taihu Lake Basin

Abstract:River ecosystems degradation has become a hot research issue internationally, and the research ideas are turning to river health and ecological recovery. River habitat assessment is significant part of river health evaluation, and it has great importance in river ecological recovery and management. In this paper, we extensively collected related literatures and references, then selected and studied the theories and practices related to river habitat assessment. River meanings and functions had been identified, and concept, structures and functions of river habitat were also addressed. River habitat research progress and assessment ideas has been generalized while relevant practices on river habitat assessment in America, England, Australia, South Africa and China were summarized to facilitate the study of river habitat quality assessment in Taihu Lake Basin, such as providing theoretical basis and reference methods.With consideration of natural habitat and human disturbance, and study of relevant river habitat assessment practices at home and abroad, an assessment system of river habitat quality in Taihu Lake Basin with three subindices (channel, bank and riparian habitat) and ten indicators was established after defining the assessment parameters, study scale, date collection methods and evaluation criteria. Reaches of Yixing district in Taihu Lake Basin were selected as case study to investigate river habitat quality evaluation and analysis. River habitat quality were compared and analyzed in different aspects such as spatial differences, location in water flow, main stream or tributaries, channel width and different river systems. One-way ANOVA analysis, correlation analysis, and T-test were used to investigate the influence of different landuse types on river habitat quality, and correlations among river habitat quality, water condition and benthic community structure are also conducted.The results showed that:The42sites’scores of the river habitat quality index ranged from29to79, with river habitat quality (IRHQ) grades from Worse to Very Good, indicating that there were apparent variations of grade level. River habitat quality of major sites (85.7%)were in Fair and Bad grades, indicating the obvious habitat degradation in this district. Bank habitat was fairly good (its mean was25.2,4.8%sites’ bank habitat were in Bad or Worse grades), Channel habitat (its mean was18.1,57.2%sites’ channel habitat were in Bad or Worse grades) and riparian habitat (its mean was8.7,61.9%sites’ riparian habitat were in Bad or Worse grades) degenerated seriously. Habitat quality was better in southern hilly area than in vast plain river area, and habitat quality in upstream (IRHQ mean was65.00) was superior than that in midstream (IRHQ mean was44.57) and downstream (IRHQ mean was50.64). There was significant habitat quality differences between main stream and tributaries (P<0.05), and habitat condition in tributaries (IRHQ mean was57.77) was better than that in main stream (IRHQ mean was49.45). There was no significant habitat quality difference between different channel widths. There existed significant differences in river habitat quality under different land use types (P<0.01), being much better in woodland than that in farmland and construction land. Different landuse types affected upstream habitat quality the most conspicuous (P<0.01), downstream fair (P<0.05) and midstream the weakest (P>0.05).The majority of sampling reaches were in eutrophication condition, and there was significant negative relationship between habitat quality and eutrophication (the correlation coefficient was0.346, and accompanied probability was less than0.01). Habitat quality and river water quality were mutually affected and constrained, habitat quality affected river water quality greatly and river water quality was an essential part of habitat quality. There was no significant correlation between benthic community structure indices and habitat parameters except for the significant correlations between few Benthic community structure indices (Gleason Abundance Index, Shannon-Wiener Index, and Pielous Uniformity Index) and habitat parameters (riverbed sediment, riparian landuse, and riparian habitat). Aquatic Benthic organisms do not respond to habitat alteration obviously, and that may associate with the disturbance aquatic ecosystem suffered from human (such as river remediation, water regulation and so on) in highly urbanization area.