• Economic and Environmental Geology
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• v.48 no.6
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• pp.509-523
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• 2015

This study introduces newly implemented geological well logs database for Jeju public water wells, built for a research project focusing on integrated hydrogeology database of Jeju Island. A detailed analysis of the existing 1,200 Jeju Island geological logs for the public wells developed since 1970 revealed six major indications to be improved for their use in Jeju geological logs DB construction: (1) lack of uniformity in rock name classification, (2) poor definitions of pyroclastic deposits and sand and gravel layers, (3) lack of well borehole aquifer information, (4) lack of information on well screen installation in many water wells, (5) differences by person in geological logging descriptions. A new Jeju geological logs DB enabling standardized input and output formats has been implemented to overcome the above indications by reestablishing the names of Jeju volcanic and sedimentary rocks and utilizing a commercial, database-based input structured, geological log program. The newly designed database structure in geological log program enables users to store a large number of geology, well drilling, and test data at the standardized DB input structure. Also, well borehole groundwater and aquifer test data can be easily added without modifying the existing database structure. Thus, the newly implemented geological logs DB could be a standardized DB for a large number of Jeju existing public wells and new wells to be developed in the future at Jeju Island. Also, the new geological logs DB will be a basis for ongoing project 'Developing GIS-based integrated interpretation system for Jeju Island hydrogeology'.

• Journal of Environmental Science International
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• v.22 no.5
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• pp.639-649
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• 2013

Over 96.2% of the agricultural water in Jeju Island is obtained from groundwater and there are quite distinct characteristics of agricultural water demand/supply spatially because of regional and seasonal differences in cropping system and rainfall amount. Land use for cultivating crops is expected to decrease 7.4% (4,215 ha) in 2020 compared to 2010, while market garden including various vegetable crop types having high water demand is increasing over the Island, especially western area having lower rainfall amount compared to southern area. On the other hand, land use for fruit including citrus and mandarin having low water demand is widely distributed over southern and northern part having higher rainfall amount. The agricultural water demand of $1,214{\times}10^3\;m^3/day$ in 2020 is estimated about 1.39 times compared to groundwater supply capacity of $874{\times}10^3\;m^3/day$ in 2010 with 42.4% of eastern, 103.1% of western, 61.9% of southern, and 77.0% of northern region. Moreover, net secured amount of agricultural groundwater would be expected to be much smaller due to regional disparity of water demand/supply, the lack of linkage system between the agricultural water supply facilities, and high percentage of private wells. Therefore, it is necessary to ensure the total net secured amount of agricultural groundwater to overcome the expected regional discrepancy of water demand and supply by establishing policy alternative of regional water supply plan over the Island, including linkage system between wells, water tank enlargement, private wells maintenance and public wells development, and continuous enlargement of rainwater utilization facilities.

• Journal of Environmental Science International
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• v.20 no.7
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• pp.857-872
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• 2011

The variation of groundwater level in Jeju Island is analyzed with the data of precipitation observed from 48 monitoring post and groundwater level observed from 84 monitoring wells during 2001 to 2009. The groundwater level rises in summer and falls in winter. The rise of groundwater level by precipitation is fast and small in the eastern region and slow and large in the western region. However, the speed of fall during the period of no rain is slower in the eastern region than in the western region. It tells that permeability is greater in the eastern region than in the western region. In this paper, we set up the base level of groundwater and calculate recharge volume between the base level and groundwater surface. During the period, the average recharge volume was $9.83{\times}10^9m^3$ and the maximum recharge volume was $2.667{\times}10^{10}m^3$ after the typhoon Nari. With these volume and the recharge masses obtained by applying the recharge ratio of 46.1%, estimated by Jeju Province (2003), the porous ratio over the whole Jeju Island is 16.8% in average and 4.6% in the case of maximum recharge volume just after typhoon Nari. A large difference in the two ratios is because that it takes time for groundwater permeated through the ground just after rain fall to fill up the empty porous part. Although the porous ratios over the whole Jeju Island obtained in this way has a large error, they give us the advantage to roughly estimate the amount of recharged groundwater mass directly from observing the groundwater level.

• Journal of Soil and Groundwater Environment
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• v.12 no.4
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• pp.60-71
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• 2007

Groundwater from public wells was monitored during one year with two month interval for hydrogeochemical parameters and chlorofluorocarbons (CFCs) as environmental tracers in Jeju Island. Concentrations of major cations and $SiO_2$ show variation less than 10% whereas $NO_3$ and dissolved oxygen (DO) showed larger variation though DO variation did not change oxic or suboxic condition. $NO_3$ concentration has no consistent seasonal pattern with the largest variation of 35%. Groundwater ages determined by CFCs became temporarily younger by 5 years in October for groundwater with ages of 15 to 25 years, which can be attributed to infiltrating water in rainy season. Compared to air temperature, groundwater temperature has much smaller variation with no phase difference, which can be accounted for by a two-component model consisting of infiltrating water from surface and deeper groundwater with negligible temperature variation. The relatively small variation in groundwater age and temperature indicates that groundwater recharge through fast flow-paths is much smaller compared with basal groundwater in terms of aquifer storage.