The potentialities of Satellite Image Time Series (SITS) are being tested to complete the monitoring of key limnological ecological parameters of French reservoirs (e.g., water temperature, level fluctuations, transparency...). This paper presents developments and results for the retrieval of water surface temperature from LANDSAT Thermal-infrared (TIR) archive data and tracking level fluctuations from very high spatial resolution SITS (Pleaides, COSMO-SkyMed, TerraSAR-X). Results obtained are satisfactory (r2 values are above 0.90 and RMSE are comprised between 1 and 2 °C for water temperature and r2 = 0.963 and RMSE = 0.42m for water level fluctuation). Given both their new affordability politic, recent progresses in acquisition and atmospheric correction processing, SITS will be an inescapable tool in the monitoring of the lacustrine ecological quality. Today, we are analyzing the potentialities of Sentinel-2 for the retrieval of chlorophyll A, colored dissolved organic matter and inorganic suspended matter in developing specific bio-optic algorithm for French lakes.