Abstract
The deterioration of water quality has become a primary environmental concern worldwide. Understanding the status of water quality and identifying the influencing factors are important for water resources management. However, reported analyses have mostly been conducted in small and focused areas. It is still unclear if factors driving spatial variation in water quality would be different in extended spatial scales. In this paper, we analyzed spatial pattern of inland surface water quality in China using a dataset with four water quality parameters (i.e., pH, DO, NH4+-N and CODMn) and the water quality level. We tested the effects of anthropogenic (i.e., land use and socio-economic) and natural (i.e., climatic and topographic) factors on spatial variation in water quality. The study concluded that the overall inland surface water quality in China was at level III (fair). Water quality level was strongly correlated with CODMn and NH4+-N concentration. In contrast to reported studies that suggested land use patterns were the determinants of inland surface water quality, this study revealed that both anthropogenic and natural factors played important roles in explaining spatial variation of inland surface water quality in China. Among the tested explanatory variables, mean elevation within watershed appeared as the best predictor for pH, while annual precipitation and mean air temperature were the most important explanatory variables for CODMn and DO, respectively. NH4+-N concentration and water quality level were most strongly correlated with the percent of forest cover in watershed. Compared to studies at smaller spatial scales, this study found different influencing factors of surface water quality, suggesting that factors may play different roles at different spatial scales of consideration. Therefore management policies and measures in water quality control must be established and implemented accordingly. Since currently adopted parameters for monitoring of inland surface water quality in China are largely influenced by natural variables, additional physicochemical and biological indicators are needed for a robust assessment of human impacts on water quality.
Highlights
Inland surface water areas include different forms of open water bodies such as rivers and streams, lakes and reservoirs, permanent and seasonal wetlands
In contrast with reported studies indicating that land use patterns were the main factors influencing surface water quality [6, 7], especially those conducted in specific areas of China [12, 15], our study found that natural environment were important in explaining spatial variation of the tested water quality parameters and water quality level in China
Water quality level was mainly determined by chemical oxygen demand in manganese (CODMn) and NH4+-N, suggesting that organic matter and nitrogen were the major types of pollutants in China’s inland surface water
Summary
Inland surface water areas include different forms of open water bodies such as rivers and streams, lakes and reservoirs, permanent and seasonal wetlands. Inland surface water quality is considered to be influenced by a wide range of anthropogenic and natural factors, such as land use, social-economic status, topographic and climate variations [2, 3]. Human-influenced land uses have been considered as important drivers of water quality deterioration [4, 5]. Pollutant concentrations in water bodies have been reported to be positively correlated with agriculture and urban land use, but negatively related to cover types of natural vegetation [6,7,8]. Agricultural land use is considered as the primary factor for stream water nitrogen concentration [8], whereas other studies indicate that urban land use had the greatest influence on nitrogen and phosphorus in surface water bodies [10, 11]
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