Selection of Route of Temporary Irrigation Water Supply Line with GIS in Emergency Situation

概要

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In natural disasters, the agricultural activity sometimes suffers enormous damage such as failure of an irri-gation tank and a water channel. To produce an agricultural commodity in such emergency circumstances, water has to be supplied by temporary works. In many cases, the water supply line is temporarily built from undamaged tanks or head works. In this paper, the selection method of the temporary irrigation water supply line with GIS was presented. The digital elevation model having 2.5 m resolution was used in GIS. The functions of GIS software were used as much as possible because the method has to be easily and quickly operated. Since the facility has to be constructed economically and rapidly, it was assumed that the water supply line would be constructed on the ground surface without excavation works and the gravity irrigation of a closed type pipeline would be adopted. For the siphon design, the location giving the high negative pressure was avoided. To examine the selected routes, the indexes indicating the ratio of positive pressure, the length of the line and the undulation of the route were introduced. It was found that the method using the information of elevation gave the economic route and the method using the gradient and slope direction information gave the safe and easy constructible route.