Thermal infrared data from Landsat is used to determine how much water is used in a farm field thumbnail: http://svs.gsfc.nasa.gov/vis/a000000/a003600/a003632/et_wetfields.0700_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.