Landsat’s data archive allows us to trace the life history of each spot of land. thumbnail: http://svs.gsfc.nasa.gov/vis/a000000/a004000/a004013/landtrendr_agu35.08000_gal.png

Above the Earth, Below the Surface: Landsat’s Role in Monitoring Water Quality
Safeguarding freshwater resources is crucial, and while scientists use a variety of ground-based techniques to gauge water quality, the Landsat program has provided water quality data from orbit for decades.