ABSTRACT:With the rapid development of the regional economy, water pollution has gradually become an environmental problem that cannot be ignored. As an important water source in central China, the Han River should strengthen water quality monitoring and management in order to ensure the sustainable development of watershed and related areas. Taking typical sections of middle and lower reaches of the Han River as the study area, this paper focuses on rapid river water quality assessment using multispectral remote sensing images.Based on measured water quality data and synchronous spatial high and medium-resolution remote sensing data (multi-spectral data of ZY3 and HJ1A) in 2013, neural network algorithm is used to establish water quality index retrieval model for the study area, and then water quality status is assessed accordingly. The results show that BP neural network retrieval model of water quality index that is established based on multispectral data of ZY3 satellite has higher accuracy and that its assessment results are of high credibility and strong applicability, which can really reflect changes in water quality and better achieve water quality assessment for the study area. In addition, water quality assessment results show that major excessive factors in the study area are total nitrogen and total phosphorus; the polluting type is organic pollution; water quality varies greatly with seasons.
INTRODUCTIONWater quality evaluation is a fundamental link in water environment management and monitoring. Only through water quality monitoring can water quality be reasonably evaluated and targeted water environment management planning and scheme be developed. In terms of water quality evaluation, traditional methods like water sample collection, indicator analysis and grade evaluation can only provide water quality status at the sampling point instead of large area of waters, while large-scale field sampling will consume a large amount of manpower, materials and financial resources. In recent years, with the rapid development of remote sensing technique, more and more researchers carried out fast, continuous and dynamic monitoring on waters by means of remote sensing technique.Further, this technique has been adopted by lots of domestic and foreign scholars on water quality evaluation (Wu, 2012, Gu, 2014, Zhu, 2013, Bitelli, 2010, Markogianni , 2014, Syahreza ,2012, Alparslan, 2007, Thiemann , 2000, and most of these studies used remote-sensing data to quantitatively retrieve concentration of water quality parameter and then establish a water quality evaluation model on this basis. The difficulty of this method mainly lies in the establishment of a definite linear relationship between remote sensing data and water quality parameter. Existing studies have shown that neural networks can better simulate the complex nonlinear relationship between remote sensing signal and water quality parameter concentration and have significantly higher retrieval accuracy than empirical models (Keiner,1998, Buckton, 1999, ...