The groundwater resources and sustainable yield of Cheju volcanic island, Korea |
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Authors: | J Hahn Y Lee N Kim C Hahn S Lee |
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Institution: | (1) Dept. of geology, Yonsei Uiversity, 134 Shinchon-dong, Sudaemoon-ku, Seoul, Korea, KR;(2) Korea Water Resources Corporation, 462-1 Jonmin-Dong, Yusung-Gu, Taejon, Korea, KR;(3) Korea Environmental Development Research Institute, Seoul, Korea, KR |
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Abstract: | Hydrogeologic data of 455 water wells comprising geologic logs, water qualities, and aquifer test results are analyzed to
determine hydrogeological characteristics, water quality, and sustainable yield of the groundwater resources of Cheju volcanic
island. The groundwater of the island occurs in unconsolidated pyroclastic deposits and clinkers interbedded in highly jointed
basaltic and andesitic rocks as high-level, basal, and parabasal groundwater under unconfined conditions. The total storage
of groundwater is estimated at about 44 billion m3. The average transmissivity and specific yield of the aquifer are at about 0.34 m2 s–1(29300 m2 day–1) and 0.12, respectively. The average annual precipitation is about 3.39 billion m3, of which 1.49 billion m3– equivalent to 44.0% of the total annual precipitation – is recharged into aquifers, with 0.638 billion m3 year–1 of runoff and 1.26 billion m3 year–1 of evapotranspiration. Based on a groundwater budget analysis, the sustainable yield is estimated at about 0.62 billion m3 year–1, equivalent to 41.6% of annual recharge. A low-permeability marine sedimentary formation (Sehwari formation), composed of
loosely cemented sandy silt, was recently found to be situated at 120±68 m below mean sea level. If the said marine sediment
is distributed as a basal formation of the freshwater zone of the island, most of its groundwater will be of parabasal type.
So the marine sediment is one of the most important hydrogeological boundaries and groundwater occurrences in the area.
Received: 16 January 1997 / Accepted: 16 June 1997 |
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Keywords: | Seogipo formation Sehwari formation Parabasal groundwater FOB FAOB Sustainable yield |
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