The Physico-chemical characteristic of water, aquatic weeds and bank flora of three water reservoirs located in Krishnagar city (longitude 88033/E, latitude 23024/N) State of West Bengal, were studied for a period of 24 months. Altogether 13 genera of aquatic macrophytes belonging to 10 families, and 24 plant species (bank flora) belonging to 16 families were identified in the present investigation. The Physico-chemical characteristic of pond water was found to be altered due to these aquatic plants. We have found a general relationship between trophic status of a water body and the aquatic plants present there. We have also found the alteration of water quality due to presence of various aquatic plants. Aquatic weeds are treated as nuisance plants in large parts of the world for their rapid vegetative growth and high dispersal rate. In many places they seriously interfere with human activities and decrease fish population. The most spectacular examples of hazards of aquatic weeds come from our subtropical and tropical areas.