This study outlines the scientific principles of freshwater ecology and their application to the management and conservation of lakes, rivers and streams and the life they support. A description of the physical and chemical characteristics of water and the ecological structure of freshwater environments are discussed first, followed by their plant and animal communities. The second half of the study is devoted to a consideration of the human impact on the aquatic environment and how ecologiccal consideration is given to eutrophication, pollution, water farming and acid rain, using case studies from all over the world. The book concludes with an assessment of future trends and the likely role of conservation measures.