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The density of epilithic algae and concentration of chlorophyll a, Shannon-Wiener index and primary productivity were chosen to study the river continuum characteristics of Xiangxi River. The results showed that in general, the algal density, chlorophyll a concentration and Shannon-Wiener index tended to be increased with increasing stream order, but this trend was not very evident in the first three orders and even reversed. The primary productivity was also higher in the higher than that in the lower stream orders, and reached the maximum in the fourth order, then decreased slightly. The ratio of gross primary productivity to community respiration was the highest in the first stream orders, which means autochthonous productivity was dominant in the river. The results did not absolutely tally with the RCC forecast, therefore, we can conclude that Xiangxi River had been undergone anthropogenic influence.

Cluster analysis and principal component analysis were used to analyze the physical and chemical characteristics of water samples collected from 19 sampling sites along Xiangxi River. The result of cluster analysis showed that Xiangxi River could be divided into three reaches, which belonged to different sub-basins. The principle component analysis on each reach showed that the main information of water quality was different from each other. In the upper reach, the main information of river water quality was hardness and total alkalinity; in the middle reach, the main information was dissolved phosphorus, total phosphorus and Cl-, in the lower reach, the main information was pH, NO2(-)-N, total nitrogen and COD. Furthermore, considering the geographical and environmental backgrounds of the Xiangxi River basin, the reason that caused the different distribution pattern of water quality in Xiangxi River was discussed. Hence, a simple approach to analyze the spatial distribution of water quality was provided.