Effects of land use on water quality in a River Basin (Daning) of the Three Gorges Reservoir Area, China: Watershed versus riparian zone

摘要

Water quality is important for domestic, industrial, agricultural and environmental purposes, and is reported to be strongly affected by land use including land use composition, configuration and intensity, whereas, the linkages are highly variable at multiple spatial and seasonal scales. We evaluated the land use effects on water quality in a typical river basin (Daning River Basin) of the Three Gorges Reservoir Region (TGRR), through comparing watershed and riparian zones. Multiple spatial-temporal scales of land use and water quality in this region are rare, while it is important for water conservation for the world largest reservoir- the Three Gorges Reservoir. Consequently, to quantitatively explore the multi-temporal and spatial impacts of land use on water quality in the Daning River Basin, we used multivariate statistical and empirical models, and indicators of land use for water quality were therefore developed. The redundancy analysis (RDA) reported that the effect of land use on overall water quality parameters was the strongest at watershed scale both in the wet and dry seasons. As regards riparian land use effects, 200 m, 300 m and 500 m buffer zones was slightly stronger during the wet season than the dry season, but the other buffer scales (i.e., 50 m, 100 m and 400 m buffer zones) were the opposite. The most important explanatory variable (MIEV) was water in multiple buffer zones, whereas the MIEV in watershed scale was Shannon's diversity index (SHDI) across seasons. Multiple linear regression (MLR) modeling reported that the linkages between single water quality parameter and land use variables were highly dependent on hydrological seasonality and spatial sales. Water, landscape shape index (LSI) and SHDI were the main predictors of riverine water quality. Water and SHDI were positively correlated with total nitrogen (TN), total dissolved nitrogen (TDN) and total phosphorus (TP), LSI was negatively correlated with TP. We highlight the importance of multiple time-space scales for understanding the impacts of anthropogenic activities (e.g., land use) on water quality, which could provide key information of land use planning for water conservation, and developing land use indicators for water quality.