The purpose of this paper is to define the actual condition of water use of Toyogawa irrigation system and the pattern of water use. This system was opened in 1968. It influenced agriculture, industry, human life and land use .Especially, due to this, the area has changed to high-agricultural area in Japan. But, in recent years, the lack of water is getting aggravated in this area. The outline of this paper is as follows; 1)change of Atsumi agriculture 2)actual water uses(each branch of water supply) 3)water use pattern to land use 4)calculating a unit of water demand 5)change of water use 6)cause of water problems 7)the conclusion.
