| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1987: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1986: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
The Rokugo alluvial fan lies 39 25' north latitude and 140 34' east longitude in northern Japan. It covers an area of nearly 14 square kilometers. The distance between the head (90 meters above sea level) and outer fringe (45 meters above sea level) of the fan is about four kilometers. The center of Rokugo town which is situated on the fringe numbers 7,000 inhabitants. they privately bore shallow wells and pump unconfined ground water for domestic uses. Ground water is recharged in the fan's area, which is utilized mainly for rice cultivation.
Ground water levels are high during the season of melting snow and the period of irrigation activities from May to August. The highest level appears at the end of the melting of the snow and the beginning of irrigation, and the lowest one occurs around the time when snow cover reaches a maximum, which is usually about 130 centimeters in depth.
Gound water recharge via paddy fields was tested during the winters of 1985/86 and 1986/87 in order to protect declining water levels. The site was selected fron an area of paddy fields in the middle of the fan : 12,493 square meters in 1985/86 and 15,588 square meters in 1986/87. This place was known through field observations to be one of the most effective recharge areas for the ground water in the fringe. A volume of water, which was withdrawn from an irrigation canal, was supplied at the rate of ca. 1,600 liters per minute from Nov. 7, 1985 to March 31, 1986 and of ca. 3,000 liters per minute from Oct. 24, 1986 to March 31, 1987.
It could be found that the recharge tests had an effect as regards the rise of ground water levels. A reference to water quality is omitted in the abstract.
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