Seasonal variations of river and lake water surface areas at global scale

Abstract Much progress has been made over the last decade to build global inventories of freshwater resources. However, existing freshwater inventories are generally produced for a fixed period in time and/or do not discriminate lakes from rivers. The emergence of deep learning methods and Big Data platforms such as Google Earth Engine offers a potential solution. Here we present a unique raster dataset at 10 m spatial resolution which classifies freshwater into rivers and lakes for a study site covering 89% of the terrestrial landmass and for the months of April, July and October 2021. This data gives us the first global-scale direct count of lakes larger than 1 hectare as ~7.3 million. We also present the first intra-annual ranges for the areas distinctly occupied by rivers and lakes where we find that basins influenced by the Asian summer monsoon (e.g. the Ganges) closely followed by the Amazon display the largest intra-annual range of river area per unit basin area. Finally, we find that whilst maximum of lake water surface occurs in October 2021, the maximum river surface is in July 2021 leading us to conclude that the global maximum occurrences of river water and lake water are not synchronous.