Global land surfacewater mapping and analysis at 30 m spatial resolution for years 2000 and 2010

Abstract

Land surface water (LSW), one of the important components of land cover, is indispensable and important basic information for climate change studies, ecological environmental assessment, macro-control analysis, etc. In 2010 China launched a global land cover (GLC) mapping project, the aim of which was to produce a 30 m GLC data product (GlobeLand30) with 10 classes for years 2000 and 2010. This chapter describes an overall study on LSW in the project. Through collection and processing of Landsat TM/ETMC, China’s HJ-1 satellite imagery and other remotely sensed data, the program achieves an effective overlay of global multi-spectral images at 30 m resolution for two base years, namely, 2000 and 2010. The water information was extracted in an elaborate way by combining a simple operation of pixel-based classification with a comprehensive utilization of various rules and knowledge through object-oriented classification, and finally the classification results were further optimized and improved by the human-computer interaction, thus realizing high-resolution remote sensing mapping of global water. The completed global LSW data results, including GlobeLand30-Water 2000 and GlobeLand30-Water 2010, are classification results featuring the highest resolution on a global scale, and the overall accuracy of self-assessment is 96%. Based on the GlobeLand30-Water 2000/2010 products, this research analyzed the spatial distribution pattern and temporal fluctuation of land surface water at global scale. The GlobeLand30-Water products were corrected for the temporal inconsistency of the original remotely sensed data using MODIS time-series data, and then indices such as water area, water ration and coefficient of spatial variation were calculated for further analysis. Results show that the total water area of land surface is about 3.68 million km2 (2010), and occupies 2.73% of land area. The GlobeLand30- Water products and their statistics provide fundamental information for analyzing the spatial distribution and temporal fluctuation of land surface water and diagnosing the global ecosystem and environment.