The water cycle is how atmosphere, land and ocean processes interact with each other. Since the launch of TOPEX/Poseidon in 1992 lake levels have been monitored, but not on a global scale due to the limitations of the instruments and orbit. The hope is that the future mission, SWOT, will be able to remedy the current issues with radar altimeters as it will have a much larger observation area and measure heights and a finer resolution. [Credit: CNES (Centre National d'Etudes Spatiales) and Mira Productions].