Drought Susceptibility and its Related Situations of Irrigation Water Users Associations in the Kanto Region, Japan

Abstract

We surveyed the current situation that irrigation water users associations face in the Kanto region and classified their drought susceptibilities by means of a questionnaire-based survey. The following facts were obtained: 1) 80% of the water users associations see the puddling and transplanting period as being the most critical period; 2) pipeline systems tend to mitigate the disparity in water availability between upstream and downstream users; 3) the water users associations take care to be impartial over the whole beneficiary area when responding to drought conditions; 4) drought impact can be shown as a power function of the irrigation water deficit rate, and the exponent of the function can take a value of less than unity depending on the associations' situation; 5) the drought susceptibility of water users associations is not constant over the irrigation season and varies according to the cropping stages; and 6) the drought susceptibility of Tochigi and Gunma Prefectures, located at the upstream sections of the Tone river basin is relatively low, but that of Saitama and Chiba Prefectures, located on the south side of the Tone river, is high.