Great Lakes States Track Water Clarity Via Satellite 

States in the Great Lakes Region are leading the country in the use of satellite data as a means for assessing the health of lakes.

Minnesota, Michigan, and Wisconsin together are home to more than 30,000 lakes larger than 10 acres in area. The number of lakes far outstrips the volunteer monitoring resources available, but now a handful of additional monitors —satellites —have joined the scene. These satellites collect and share statistically reliable data on an unprecedented scale. Researchers found that analysis of certain wavelengths of visible light in the satellite data correspond closely with that of on-the-ground Secchi disk readings, allowing accurate estimates of lake clarity for thousands of otherwise unmonitored lakes. Researchers are also mapping water clarity with archived satellite data enabling them to go back into the past and look at historical trends. http://resac.gis.umn.edu/water/regional_water_clarity/regional_water_clarity.htm 

EPA Nonpoint Source News-Notes, August 2005