• Journal of Environmental Science International
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• v.25 no.1
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• pp.135-146
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• 2016

This study analyzed fluctuations of ground water level of ground water wells developed in Seongsan watershed of Jeju Island until 2013 using MODFLOW, a numerical analysis model. Ground water level shows greater fluctuations from increase of pump capacity compared to the number of ground water wells. The development of ground water at the top of watershed was found to have direct influence on ground water level. Ground water wells developed until 2013 were used to continue pumping for 50 days, and ground water level of coastal region was reduced below 50% compared to the standard water level. In addition, the range of fluctuation of water level was large in the east coast region, which represents the direction of flow of ground water.

• The Journal of Engineering Geology
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• v.25 no.1
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• pp.45-55
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• 2015

Purifying leachate discharged from animal carcass disposal sites requires decisions regarding the locations and numbers of boreholes. An electrical resistivity survey, known to be effective for investigating leachate distribution, was performed to evaluate the range extent of contamination due to local hydrological properties, such as groundwater flow direction, and geological structure. Results of the survey at four sites at a landfill near Icheon and Anseong, Gyeonggi Province, showed low-resistivity zones (20-200 ohm-m) at a depth of 8 m from the surface. Sites 1-4, which contain 5, 2, 4, and 2 boreholes, respectively, were estimated to have a contaminated groundwater acquisition capability of 12.9 m, 13.7 m, 10.1 m, and 18.0 m, and measured pumping capacity of 2,040 m³, 479.8 m³, 1,492.3 m³, and 691.9 m³, respectively.

• Journal of Soil and Groundwater Environment
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• v.7 no.2
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• pp.23-33
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• 2002

There are two case history. One is the case of 3 wells-group well system-drilled and artificially hydrofractured for dewatering to help to excavate and treat deep building foundation. The recoveries of groundwater of 3 wells are increased 29%, 42% and 110% respectively through hydrofracturing. Simultaneous pumping test reveals that 3 wells are geohydrologically interconnected considering lowered specific capacity comprising influence of additional drawdown effect by other 2 wells compared to single well test. Response time effect during single well test shows that dorminant lineaments are more expandable to other geological structures. The other one is the case of 28% increasing of groundwater productivity for domestic use by hydrofracturing.

• The Journal of Engineering Geology
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• v.29 no.4
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• pp.417-425
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• 2019

Agricultural groundwater use accounts for 51.8% of total groundwater use, so accurate estimation of groundwater use is important for efficient groundwater management. The purpose of this study is to develop a method for estimating the groundwater use of agricultural (rice farming and dry-field farming) wells using regression tree model based on the measured data of 370 wells. Three input variables of the model were evaluated as being significant: well depth, pipe diameter, and pump capacity, and the importance of each variable was 75% for well depth, 17% for pipe diameter, and 8% for pumping capacity. The daily usage of agricultural (rice farming and dry-field farming) wells by the regression tree model was estimated to be very similar to the actual usage, compared to the previous estimation method proposed by the Ministry of Construction and Transportation. In the future, it is expected that the reliability of the usage statistics will be improved if additional observed data is secured and this classification method is modified.

• Journal of the Korean Society of Groundwater Environment
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• v.4 no.2
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• pp.95-102
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• 1997

So far, several fractal models of fluid flow in a fractured aquifer have been developed. In this study, a new fractal model is derived that considers transient flow in the dual-porosity aquifer with the fracture skin between the fissure and the block, and the storage capacity and the wellbore skin on the pumping well. Constant-head upper boundary is specified in the block. This model is a generalized one which comprises both modified Hantush equation (1960) and Boulton-Streltsova equation (1978). Type curves are plotted for different flow dimensions (0.5, 1, 1.5, 2, 2.5 and 3) with various values of the leakage factor and the fracture skin. They show dimensionless drawdown in the pumping well and observation wells located either in the fissure system or in the matrix block.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.182-182
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• 2017

Many small island nations rely on groundwater as their only other source of freshwater in addition to rainwater harvesting. The volume of groundwater resource of small island nations are further limited by their smaller surface area and specific hydrogeology. The rapid growth of population and tourism has led to increasing water demands and pollution of available groundwater resources. The predicted climate change effects pose significant threats to the already vulnerable freshwater lens of small islands in the form of rise in sea level, coastal inundation, saltwater intrusion, varied pattern of precipitation leading to droughts and storm surges. The effects of climate change are further aggravated by manmade stresses like increased pumping. Thus small island water resources are highly threatened under the effects of climate change. But due to the limited technical and financial capacity most of the small island developing states were unable to conduct detailed technical investigations on the effects of climate change on their water resources. In this study, we investigate how well small island countries are preparing for climate change. The current state of freshwater resources, impacts of predicted climate change along with adaptation and management strategies planned and implemented by small island countries are reviewed. Proper assessment and management practices can aid in sustaining the groundwater resources of small islands under climate change.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.6
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• pp.41-53
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• 2019

Recently, the damage caused by climate change has been distinguished in the world. The Korean Peninsula is also suffering from drought, so it is necessary to study the vulnerability assessment to identify and predict the state of the irrigation facility, which is a irrigation facility. As the damage caused by drought is occurring in the Korean peninsula, it is necessary to study the vulnerability assessment to know the condition of the irrigation facility, and to predict it. The target areas were Yeongdong-gun, Cheonan-si, Mungyeong-si, Geochang-gun, Muju-gun, and Yeonggwang-gun. The survey items were selected as positive impacts survey items, including precipitation, groundwater level, and pumping capacity per groundwater well. The negative impacts were selected as the cultivation acreage, Number of days without rain, and the ratio of private underground wells. The survey method was investigated by various methods such as "weather data portal", "groundwater level status information", "agricultural drought management system", "groundwater survey yearbook". The results of vulnerability assessment were expressed by the score by conducting survey and standardization. As a result, Yeonggwang-gun showed normal vulnerability, and other areas showed "vulnerable" or "very vulnerable".

• Journal of Soil and Groundwater Environment
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• v.23 no.6
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• pp.28-36
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• 2018

This study was conducted to estimate groundwater reserves within a designated depth. Three methods were applied to one representative county in southern Gyeongsang province, South Korea, to estimate the groundwater reserves in the aquifers. Estimated amounts of groundwater reserves in the region ranged from $20.2{\times}10^9m^3$ to $68.7{\times}10^9m^3$ (average $37.9{\times}10^9m^3$). Groundwater recharge obtained with a recharge ratio of 16.6% was $1.1{\times}10^9m^3/year$. Exploitable groundwater with an assumption of decadal-cycle minimal rainfall of 977.0 mm/year was approximated as 72% ($0.8{\times}10^9m^3/year$) of the total replenished water by recharge. The volume of recharge and exploitable water accounted for only 1.1% and 0.8% of groundwater reserves, respectively, which indicates substantial capacity of the reservoir to supply groundwater in an event of unexpected droughts. Nonetheless, each groundwater well should strictly comply with its allocated pumping rate to avoid alluvial groundwater depletion.

• Journal of Environmental Science International
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• v.29 no.11
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• pp.1099-1108
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• 2020

In this study, the capacity of supplying agricultural water to 13 districts was analyzed by calculating the necessary water supply for the arable land of Gunwi-gun and examining the capacity of supplying water to reservoirs, streams, pumping stations, collection sites, and groundwater wells in Gunwi-gun. As a result, among the 13 districts the second district was found to be short of water by 1.2×10⁶ tons/year. In general, local governments establish drought measures by selecting drought disaster risk zones. While selecting drought-risk areas, some water-poor areas that do not have water sources should be selected, even if the entire area has a sufficient water supply. The water-supply evaluation at the regional level was insufficient for locating areas without water sources, but most areas with water sources, such as streams, reservoirs, and pumping stations, were found to have no shortage of water. To locate water shortage areas without water sources, GIS analysis conducted a field survey of areas with a distance of 4 or less than that of water sources analyzed by GIS analysis. Sixty-nine sites in 13 districts were selected for the on-site survey and six areas of water shortage were identified in areas other than the second district.

• Journal of Soil and Groundwater Environment
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• v.8 no.3
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• pp.74-85
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• 2003

To increase the yield from groundwater wells in various rock types by hydrofracturing, tests of 12 wells were carried out as a part of sustainable groundwater development and artificial recharge project. Test wells are selected 5 wells in Jurassic granites, 2 wells in Cretaceous volcanics, 4 wells in Cretaceous sedimentary rocks and one well in Pre-Cambrian gneiss. The results show that specific capacity of II wells increased about 7% to 366%, while a well in Cretaceous sedimentary rock decreased about 43.4% owing to plugging of fault clay. Meanwhile, impact distances influenced due to hydrofracturing ranged from 5.4 m to 82.7 m from the test wells, actual drawdown data measured during the pumping test after hydrofracturing are more or less decreased and reveals balanced drawdown.