A Global ~90 m Water Body Map Derived from Multi-temporal Landsat Images and Its Application to Global Hydrodynamic Modelling

Abstract:

Here we introduce the Global 3-second Water Body Map (G3WBM), developed by an automated algorithm to process the multi-temporal Landsat Global Land Survey (GLS) database. We used 33,890 scenes from 4 GLS epochs in order to delineate a seamless water body map, without cloud and ice/snow gaps. Permanent water bodies were distinguished from temporal water-covered areas by calculating the frequency of water body existence from overlapping, multi-temporal, Landsat scenes. By analyzing the frequency of water body existence at 3 arc-second resolution, the G3WBM separates river channels and floodplains more clearly than previous studies. The global totals of delineated permanent water body area and temporal water-covered area are 3.25 and 0.49 million km2 respectively, which highlights the importance of river-floodplain separation using multi-temporal scenes. The accuracy of the water body classification was validated in Hokkaido (Japan) and in the contiguous United States using an existing water body databases. There was almost no commission error, and about 70% of lakes >1 km2 shows relative water area error <25%. Though smaller water bodies (<1 km2) were underestimated mainly due to omission of shoreline pixels, the overall accuracy of the G3WBM should be adequate for larger scale research in hydrology, biogeochemistry, and climate systems and importantly includes a quantification of the temporal nature of global water bodies.

At the AGU presentation, we will also discuss how this new water body map can be used to improve global river hydrodynamic simulations. Using the developed water body map and other data sources, we generated the global 3-second flow direction map, global river width map, and hydrologically adjusted DEM. Beyond the SRTM and HydroSHEDS domain (60N-60S), these new datasets cover all land areas except Antarctica (i.e. N85-S60, except Antarctica). We will show how these new topography datasets will improve the river-floodplain hydrodynamic simulations.