The effects of land use on water quality of alpine rivers: A case study in Qilian Mountain, China.

Land use influences the variation of river water quality. This effect varies depending on the region of the river and the spatial scale at which land use is calculated. This study investigated the influence of land use on river water quality in Qilian Mountain, an important alpine river region in northwestern China, on different spatial scales in the headwaters and mainstem areas. Redundancy analysis and multiple linear regression were used to identify the optimal scales of land use for influencing and predicting water quality. Nitrogen and organic carbon parameters were more influenced by land use than phosphorus. The impact of land use on river water quality varied according to regional and seasonal differences. Water quality in headwater streams was better influenced and predicted by land use types on the natural surface at the smaller buffer zone scale, while water quality in mainstream rivers was better influenced and predicted by land use types associated with human activities at the larger catchment or sub-catchment scale. The impact of natural land use types on water quality differed with regional and seasonal variations, while the impact of land types associated with human activities on water quality parameters mainly resulted in elevated concentrations. The results of this study suggested that different land types and spatial scales needed to be considered to assess water quality influences in different areas of alpine rivers in the context of future global change.