[Relationships between river water quality and land use type at watershed scale]

Based on the remote sensing images of 54 water quality monitoring stations within the Suzi River watershed, the riparian buffer zones at 6 scales were constructed by ArcGIS, and the 8 landscape indices at landscape and class levels were calculated with FRAGSTATS software. A correlation analysis on the landscape indices and river water quality was made from the viewpoints of landscape space pattern and composition. In the watershed, the landscape pattern in different riparian buffer zones had different effects on the river water quality. When the distance of the buffer zones was less than 300 m, the main landscape types were dry land, construction land, and paddy filed, and their area ratio, patch number, patch density, maximum patch index, maximum shape index, and aggregation index were higher. In these buffer zones, farmlands had higher connectedness, and thus, had greater effects on the river water quality. When the distance of the buffer zones was more than 300 m, forest land had a larger area ratio and a higher connectedness, which would benefit the improvement of river water quality to some extent. In the watershed, farmland and construction land played a key role in affecting the river water quality.