Аннотация:Express diagnostics of large freshwater reservoirs is of great interest for both scientists and local authorities especially within a summer period due to rapid growth of phytoplankton (so-called algal bloom). Points of interest include changes of natural ecosystems and fresh water supply quality control during algal bloom. Conventional contact methods are of high man-power consumption and remote probing methods are of high demand. Laser remote probing methods are of great interest in optic remote probing methods due to quality of the information provided. Laser technology progress resulted in a compact LIDAR systems development that could be installed on unmanned aircraft vehicle. Results of laser remote probing of algal bloom in south area of Gorky freshwater reservoir are presented. Compact Raman LIDAR system was installed on ship and a backscattered spectra of upper water layer were digitized along the ship route. The perspectives of laser remote probing for express diagnostics of alga types variations were demonstrated. Elastic and Raman scattering as well as chlorophyll fluorescence were quantified, mapped and compared with data acquired by commercial STD-probe installed at a depth of 0.3 m below water surface. A good correlation between laser remote probing results and STD-probe data for algae concentration was established. Accuracy of water temperature measurements by Raman OH-band profile was shown to be dependent on chlorophyll fluorescence spectra interference due to high phytoplankton concentration. The results of laser remote probing of algal bloom in freshwater reservoir promote development of compact LIDAR systems installed on unmanned aircraft vehicles for fully automatic measurements of water properties at large area.