The Global Surface Area Variations of Lakes and Reservoirs as Seen From Satellite Remote Sensing

Natural lakes and artificial reservoirs are important components of the Earth system and essential for freshwater, food, and energy. Relatively little is known about the variations of lake and reservoir surface area globally. For the first time, this study presents the global variation of lake and reservoir surface areas for all water bodies larger than 1 km(2). Using radar remote sensing, we found that global aggregate area variations were only 2% of total surface area over a 3 year period. When considering the total surface area of shoreline regions that transition between land and water, these variations equaled 20% of total lake and reservoir surface area, largely driven by variations of smaller water bodies. Additionally, surface areas of reservoirs tends to be more variable than the surface area of lakes of similar size. The large surface area variations evidenced here, could have a previously underappreciated impact on the Earth System. Plain Language Summary Natural lakes and artificial reservoirs are important parts of the Earth system and provide many benefits for humanity. Despite this importance, there are key things about lakes and reservoirs that are unknown globally, including how and when surface areas vary. This study uses satellite-based radar observations to estimate surface area variations in a set of the world's largest lakes and reservoirs. We found that the total surface area variability was relatively small when aggregated globally, only accounting for 2% of mean global surface water area. However, the total shoreline area that transitioned between water and land as a result of lake and reservoir variability was much more substantial, around 20% of mean global surface area. The variability of smaller water bodies contributed more to these transitional areas than larger water bodies. We also found that artificial reservoirs tended to be more variable than similarly sized natural lakes. Ultimately, the large surface area variations evidenced here, particularly in small water bodies, could have a previously underappreciated impact on the Earth System.