Water quality in the upper Han River basin, China: the impacts of land use/land cover in riparian buffer zone

Vegetated riparian zones adjacent to rivers and streams, can greatly mitigate nutrients, sediment from surface through deposition, absorption and denitrification, yet, human activities primarily land use practices have dramatically reduced the capacity. In this study, 42 sampling sites were selected in the riverine network throughout the upper Han River basin (approximately 95,200 km²) of China. A total of 252 water samples were collected during the time period of 2005–2006 and analyzed for physico-chemical variables and major ions. Correlation analysis, principal components analysis and stepwise least squares multiple regression were used to determine the spatio-temporal variability of water quality variables and in particular their correlations with land use/land cover in the 100 m riparian zone along the stream network. The basin in general has a better water quality in the dry season than the rainy season, indicated by the primary pollutants including COD_Mn and nitrogen. Major ion compositions display large spatial and seasonal differences and are significantly related to land use and land cover in the riparian zone, while riparian landscape could not explain most of the water quality variability in T, pH, turbidity, SPM and COD_Mn. The research could provide help develop sustainable land use practice of the riparian zone for water conservation in the basin.