Study on Agricultural Water Use Systems and Environmental Preservation in the Paddy Field Areas

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The area of this study are following next three irigation area ; the Nakagawa river basin in Saitama Prefecture, the Ohtone irrigation district in Chiba prefecture and the Ashigara plain in Kanagawa prefecture.Methods of this research are measuring river and agricultural water flow and analysing water quality in irrigation and nonirrigation peorids. The results are shown next ;(1) In the case of the Nakagawa river vasin, much agricultural water have taken in the irrigation district so the water pollution showed low level concentration.(2) In the case of the Ohtone irrigation district, supplied not enough agricultural water quantity, so water pollution has been progressed.(3) In the case of Ashigara irrigation plain, the irrigation method is a plot-to-plot irrigation, this is effective to rise water tempretutre for irrigation. The water concentration is showed low level through paddyfields, this is a function of paddy fields on polluted water dilution.