Relationships between Land Use Pattern and Surface Water Quality in the Plain River Network Area:A Case study of Wujiang in Jiangsu Province

Human activities being characterized by land use are primary sources of water pollution,such as agriculture,resident,industry.The type,size and distance of different land use types to water bodies are usually studied in a manner relating them to water quality.The authors performed a preliminary study on exploring the relationship between land use and water quality in Wujiang,a county-level city with the typical river net plain in the Taihu Lake catchment.In the study area 29 monitoring sites for water quality assessment were distributed and utilized.Based on GIS spatial analysis,strip and round types of contributing zones were developed around these sites,and the proportions of five types of land use types were extracted from buffer zones with radii ranging from 100 m to 2000 m.On the basis of three water quality variables including CODMn,NH3-N and DO,the correlation relationship between water quality and land use pattern over different contributing zones was examined.Results showed that the land use patterns in Wujiang had great impacts on surface water quality.Also,the land for urban construction exhibited a significant positive relation with CODMn and NH3-N,but a negative relation with DO.The forestland negatively correlated with CODMn and NH3-N for all strip buffers and some of round buffers.Also,there existed a positive correlation between cultivated land and DO in part of scales of round and strip contributing zones.It was suggested that the expansion of urban construction land leaded to negative effects on water quality of Wujiang city.Nevertheless,the cultivated land and forestland showed positive effects to some extent.Furthermore,partial correlation analysis results demonstrated that the dominant role of the land for urban construction in affecting water quality.This meant that the urban non-point pollution could be a major factor degrading water quality compared to other sources,like agricultural non-point pollution.Third,statistical analysis suggested the scale effect caused by different land use types.The closer cultivated land was suitable for improvement to water quality.The construction land brought more impacts on water quality at scales larger than 500 m.The study would be greatly helpful for land use planning and regional development policy making,progressively addressing water environmental problems in the Taihu Lake catchment.