Experimental Study of Basin Artificial Recharge of Ground Water in Rokugo Alluvial Fan, Northern Japan
1999 Volume 41 Issue 1 Pages 23-33
Details
1999 Volume 41 Issue 1 Pages 23-33
The Rokugo alluvial fan lies around 39°25' N and 140°34' E in northern Japan. The distance between the proximal fan on 90m above sea level and the distal fan on 45m is about 4km. Artificial recharge of unconfined ground water using basin method was tested in a period from April 13 to 27,1998. The basin was constructed on the central part of the fan, and has 1,045m2 bottom area and 3m depth. Aquifer of the fan consists mainly of gravel, of which hydraulic conductivity is in order of 10°∼10-2cm/sec and specific yield is over 20%.
We obtained the following results through the test.1. During the test period, average water supply recorded 71.2l/sec, and average infiltration amounted to 24.5cm/hour.2. At one of the observation wells,480m apart from the basin, ground water level began rising two days after, and the maximum ground water level appeared 11 days after the beginning of the recharge. Difference of the ground water level for the nine days was 1.40m.3. Ground water mound was formed under the basin during the recharge test.4. In area of west and northwest direction of the recharge basin, water table was raised due to the formation of the ground water mound. Although ground water level at the Kotohira observation well goes down usually in April, it moved almost same level during the test period.5. Effects associated with ground water level conservation ranges to the toe of the fan. Ground water is discharged from the belt of water springs situated on the toe.
