Source: USGS Landsat Mission Website
Jan. 3, 2013 • Landsat Surface Reflectance Climate Data Records (CDR) for Global Land Survey (GLS) collections 2000, 2005, and 2010 are now available from the Landsat CDR/ECV data set on EarthExplorer.
The Surface Reflectance CDR is one of a number of higher-level Landsat data products produced to support land surface change studies. More details about Surface Reflectance CDRs can be found on https://www.usgs.gov/landsat-missions/PLSRP.php.

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.