Rivers are recognized as major natural resources, not only as sources of domestic, industrial and agricultural water and hydro-electric power, but also for food production and increasingly for recreation and tourist promotion. This awareness has led to increased study of lotic limnology, particularly with respect to the development of the potentials of river systems. The concern over deterioration of watercourses as a result of poor land utilization and their use as repositories for man's rejectamenta has stimulated research into the basic dynamics of the river environment and its biotic...