[Preliminary analysis of spatiotemporal variation of water quality and its influencing factors in the Jiulong River watershed].

Twenty one sub-watersheds in the Jiulong River watershed were chosen for in-situ monitoring water quality of baseflow in flood season, dry season and average season in 2010. Geographical information system and multivariate analysis were coupled to characterize the spatiotemporal variation of water quality and identify its influencing factors. The results show that the water quality in dry season is the worst whereas the water quality in flood season is comparatively good. The first principal component representing sanitary and industrial wastewater pollution, explained 45.58% of the total variance of water quality. The second principal component concerning pollution due to agricultural activities, explained 21.28% of the total variance. NH4(+) -N, SRP, potassium permanganate index, K+, Cl-, Mg2+ and Na had a significantly positive correlation with percentage of built-up and density of population. NO3(-) -N was correlated positively with percentage of cropland. The sub-watersheds with high proportion of build-up area and density of population show high concentration of NH4(+) -N, SRP, potassium permanganate index, K+, Cl-. Comparatively, the sub-watersheds with high percentage of cropland show high level of nitrate concentration. Improvement of the wastewater treatment efficiency and increased recognition of agricultural non-point source pollution were finally highlighted from watershed management perspectives.