Location of my research are reservoirs which have an area of 47 and 62 km2.
I need a better image resolution than Landsat(Pan).
Geographic Information Systems Stack Exchange is a question and answer site for cartographers, geographers and GIS professionals. It only takes a minute to sign up.Sign up to join this community
You could try the MODIS Gridded Vegetation Indices.
I've worked with MODIS products before and can vouch for their quality, although I haven't done any chlorophyll analysis like the one that you mention.