水体颜色是太阳光与水中物质相互作用的结果，与叶绿素a、悬浮物、有色可溶性有机物等水质参数密切相关。水体颜色观测早在一百年前已经开始，通过福莱尔水色计将水体颜色从深蓝到红棕色分为21个级别，称为水体颜色指数。近几年来，卫星遥感被应用于提取水体颜色指数，用来分析研究区水体颜色及其反映的水质的时空变化。但是，这些研究工作刚刚起步，还有很多需要解决和完善的问题。本项目将开展基于卫星遥感的长时序大范围湖库水体颜色指数时空变化研究，分析水体颜色指数与湖库典型水质参数的关系及其不确定性，发展基于Landsat系列卫星（TM/ETM+/OLI）的湖库水体颜色指数遥感提取方法，生产1986年以来全国面积大于1km2的湖库水体颜色指数产品，并分析其时空变化特征及其影响因素。该研究将有利于更加科学的认识我国湖库水环境演化机制，为我国湖库水环境保护和治理提供科学决策支持，具有重要的科学意义和现实意义。

Water color is a direct consequence of sunlight interactions with water constituents, and it is closely related to water quality parameters, such as the contents of Chlorophyll-a, suspended matter, and colored dissolved organic matter in water. Water color has been recorded and characterized by the Forel-Ule scale for more than 100 years. The Forel-Ule scale divides the natural water color into 21 classes covering water colors from dark blue to yellowish brown, and the water color classes are called as Forel-Ule Index (FUI). In recent years, satellite remote sensing has been applied to calculate FUI, then the spatial and temporal changes of water quality can be analyzed based on the FUI results. However, the use of FUI in satellite remote sensing is still in the early stage, and there are many problems to be solved and further studied. This project will research on the water color temporal and spatial change over lakes in large scale and long time series based on satellite remote sensing. Firstly, the FUI calculation algorithm will be developed for Landsat sensors (i.e. TM/ETM+/OLI). Then, the relationship and uncertainties between FUI and classic water quality parameters will be analyzed. Finally, the FUI product for the nationwide lakes in China will be produced in long time series from the year of 1986. Based on this, the temporal and spatial water color changes will be analyzed for the nationwide lakes. Moreover, the environmental factors of water color change will be discussed for the lakes in different regions in China. Therefore, studying on the water color change over the nationwide lakes has a as a very important scientific and practical significance, which will help to fill the knowledge gap in the evolution mechanism of lake water quality in China, and provide scientific decision-making support for the protection and treatment of lake water quality in China.