제주도 중산간지대의 지표수 이용시설에 대한 수문지형학적 접근

Abstract

Before supplying underground water through a tubular well, irrigation facilities for surface water were used in the transition zone to mountain area of Jeju Island. This paper has examined the hydrogeomorphologic characteristics of irrigation facilities in Dongbaekdongsan such as distribution, structure, water source and water balance. There are ten facilities including two wells and eight reservoirs. The well was constructed in a collapsed hollow of lava flow and has a stair to scoop up water which originates from boundaries between lava flow units below two or three meters deep. By contrast, the reservoir was constructed on a lava flow abundant in a micro-relief by building a stone wall with a sluice to have surface water easily introduced into the reservoir. Since a lava flow, particularly pahoephoe, often produces an impermeable layer, depressions and collapsed hollows developed in the lava flow could become small wetlands largely maintained by rainfall and provide a base for constructing irrigation facilities. Surface water flows into four reservoirs through temporary channels in addition to direct rainfall. Water storage of Meonmulggak consists of direct rainfall of 60.8% and water flow of 39.2%. Heavy rainfall produces overflow and subsequent surface runoff from Meonmulggak which contains an annual water volume of 1,860 m3. The water balance of catchment area including Meonmulggak demonstrates that rainfall is partitioned into evapotranspiration of 31.4%, deep percolation of 67.8% and surface water runoff of 0.8%, respectively.