Abstract: Macroinvertebrates were sampled at 21 sites in Liuxi River, Guangdong Province in February, June, September and December of 2015. In total, 114 species from 95 genera and 54 families of macroinvertebrate were identified. There were 81 species in Insecta, accounting for 71.05% of the total species; 23 species in Mollusca (Gastropoda, Lamellibranchia), accounting for 20.18%; and 10 species of Hirudinea, Oligochaeta and Crustacea, accounting for 8.77%. The spatial distribution range, discrimination, and paired Pearson correlation of 21 candidate metrics were explored over the sampling sites, including 6 reference sites and 15 impaired sites. Six biological metrics were finally selected for the B-IBI index, including Shannon’s diversity index, EPT number of taxa, percentage of Chironomidae taxa, percentage of Tubificidae taxa, the number of sensitive taxa and percentage of tolerance taxa. These six biological metrics were calculated in their relative values based on the disturbance, and B-IBI was the summation of all the six metrics. According to these established ranking criteria, our assessment showed that among 21 sites of Liuxi River, 5 sites were healthy, 3 sites subhealthy, 10 sites fair, and 3 sites unhealthy. Overall, the Liuxi River was fair in health status; the upstream and the branches (including Guifeng River, Shiba River, and Lvtian River) were healthy, the midstream and the downstream, Niulan stream, most of the branches were fair or poor. Our results suggested that the B-IBI was suitable for evaluating the water quality of Liuxi River, and human activities had great impacts on the community structure of macroinvertebrates.

Key words: water use efficiency, yield, soil water, winter wheat, conservation tillage