The theme for the 2021 #WorldWaterDay is valuing water. We would therefore like to use this day to appreciate our Freshwater ecosystems, which are one of our most precious resources, providing people and societies with many important benefits. Rivers, streams and lakes/reservoirs throughout the world provide water for domestic usage as well as for irrigation, for livestock watering and as a source for hydropower and recreation. Wetlands act as a sponge, absorbing and storing excess water to reduce floods and to delay the onset of droughts; wetlands trap sediments, improving water quality in associated watersheds; and freshwater ecosystems provide important habitats for many different species as well as having great cultural and recreational value. Despite their value, Freshwater ecosystems are under threat and need protection to maintain their ecosystem services in the long-term.

Understanding the state of the world’s freshwater water resources is the essential first step to protect and restore them. With the expanding number of satellites with free and open data policies and global observation scenarios, Earth Observation (EO) comes with a great potential for assisting countries and river basins worldwide with their hydrological monitoring requirements.