Abstract
With regard to hydrology, water budget, water, quality, and ecology of Lake Biwa-ko, we analyzed their seasonal characteristic within one-year basic cycle and tried to present average aspects of the seasonal changes of the water environment in the form of a calender. As a result, it was proved that four seasons can be set : in hydrological calender in compliance with seasonal change of precipitation; in water budget calender in compliance with the process of formulation and collapse of lake water temperature stratification; in water quality calender in compliance with seasonal change of nutrition salt, organic matters, plant planktons and so on; and in ecological calender in compliance with seasonal change of plant planktons, hydrophytes, benthos, and fishes. Preparation of these water environment calenders is highly effective and helpful in pigeonholing and consolidating existing knowledge and findings regarding water environment of lakes and marshes, in grasping them as a whole, and in establishing supporting system for actual maintenance and protection of the water environment.
