Abstract: Recent diversion of external salt spring has resulted in a steady decrease of the salinity in Lake Kinneret (Israel).Since Kinneret waters are primarily used for domestic purposes, the decrease in salinity is considered worthwhile but changes in salinity might be detrimental to endemic organisms in the lake.By means of experimental analysis, it was found that changes in salinity of the lake water caused a shift in the bacterial population structures.Moreover, a relationship between the salinity and the size of bacterial populations was observed.The results indicate that salinity changes are important in the preservation of water quality and for future lake managements.