扇状地自由地下水の平面的挙動について ―明きょ排水の水理について(4)―

Abstract

The problems of unconfined groundwater flow from rivers to drainage channels inthe K~fu alluvial fan are solved with the aid of a numerical analysis based on the Laplaceequation. The two-dimensional region for the flow is bounded by four borded boundarieswhich are the Kamanashi, the Fuefuki and the Ara rivers on three sides and the moun-tain area on the fourth side. Sixteen channels which have drainage and irrigation actionare scattered in the downstream part of this region. Some or all of them are taken intoaccount as the internal boundary condations in the region.The calculations of this numerical analysis are carried out by means of the SuccesiveOver-Relaxation method. The results obtained in this analysis have been tested againstthe observed values with close agreement.On the other hand, the relations between the changes of the boundary conditionsmade by the river improvements and the groundwater behaviors induced by the changesin the region are discussed by using the above mentioned numerical analysis.In coclusion, it has been made clear that the effects of changes in the internal bound-aries induced by drainage channel improvements have contributed more to the groundwaterlowering in the downstream region than the effects of the changes in the river boundaries.