• The Journal of Engineering Geology
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• v.24 no.2
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• pp.237-246
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• 2014

Seasonal variations of major contaminants in groundwater around livestock burial areas in Gyeonggi province, Korea, were examined. Seven typical contamination indicators ($NO_3$-N, $NH_3$-N, chloride, pH, DO, ORP, and EC) were monitored in groundwater samples collected from 84 wells located within 60 m of livestock burial sites for the leachate plume emanating from the livestock burial sites. The monitoring results of pH, DO, ORP, and EC revealed minimal seasonal variations, providing no evidence for leachate plumes. The $NO_3$-N concentrations were below 30 mg/L and exhibited minimal seasonal fluctuations, even in the wells located close to (< 20 m) the burial sites; the $NH_3$-N and chloride concentrations also showed similar results. The contamination indicators examined in this study indicate that the observed groundwater contamination is primarily from preexisting pervasive contamination due to agricultural activities and livestock farming, not leachates derived from nearby livestock burial sites.

• Economic and Environmental Geology
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• v.51 no.1
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• pp.15-26
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• 2018

The spatio-temporal variations of nitrate concentrations in groundwater of Jeju Island were evaluated by an analysis of time series groundwater quality data (N = 21,568) that were collected from regional groundwater monitoring (number of wells = 4,835) for up to 20 years between 1993 and 2015. The median concentration of $NO_3-N$ is 2.5 mg/L, which is slightly higher than those reported from regional surveys in other countries. Nitrate concentrations of groundwater in wells tend to significantly vary according to different water usage (of the well), administrative districts, and topographic elevations: nitrate level is higher in low-lying agricultural and residential areas than those in high mountainous areas. The Mann-Kendall trend test and Sen's slope analysis show that nitrate concentration in mid-mountainous areas tends to increase, possibly due to the expansion of agricultural areas toward highland. On the other hand, nitrate concentrations in the Specially Designated Groundwater Quality Protection Zones show the temporally decreasing trend, which implies the efficiency of groundwater management actions in Jeju. Proper measures for sustainable groundwater quality management are suggested in this study.

• The Journal of Engineering Geology
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• v.28 no.2
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• pp.313-324
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• 2018

In order to study the earthquake precursor in the Korean peninsula, long-term variations of chemical composition, radon-222, and water level were measured at depths (-60 m, -100 m) in the groundwater monitoring wells of the Daejeon and the Cheongwon area. The pH and electrical conductivity of groundwater in the monitoring wells showed some relationship with the Pohang earthquake. The ${HCO_3}^-$ and $Cl^-$ concentration of groundwater in the Daejeon and $Mg^{2+}$, $Cl^-$ and ${NO_3}^-$ in the Cheongwon showed some relation with the Pohang earthquake. However, it is not distinct to find the relationship between their variation and earthquake. The radon-222 concentration in Daejeon was observed a significant increase from a minimum of 162 Bq/L prior to the earthquake to 573 Bq/L right after the earthquake, that indicating a strong correlation with earthquakes. In the case of groundwater levels, it can not find some correlation between earthquakes and continuous decreasing trend in the monitoring wells of Daejeon and Cheongwon area. However, water level of a national groundwater observation well within 10 kilometers of Pohang epicenter was recorded as an abrupt drop right before the earthquake. Conclusively, although the location of monitoring wells is more than 180 kilometers apart from the epicenter of the Pohang earthquake, the radon gas in groundwater can be considered as a reliable candidate among earthquake precursors. The pH, electrical conductivity, ${HCO_3}^-$ and $Cl^-$ among hydrochemicals showed some correlation with earthquake should be monitored during a longer term to recognize distinctly as a precursor of earthquake.

• Journal of The Korean Society of Agricultural Engineers
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• v.65 no.2
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• pp.1-11
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• 2023

This study analyzed the impact of greenhouse cultivation area and groundwater level changes due to the water curtain cultivation in the greenhouse complexes. The groundwater observation data in the Miryang study area were used and classified into greenhouse and field cultivation areas to compare the groundwater impact of water curtain cultivation in the greenhouse complex. We identified the characteristics of the groundwater time series data by the terrain of the study area and selected the optimal model through time series analysis. We analyzed the time series data for each terrain's two representative groundwater observation wells. The Seasonal ARIMA model was chosen as the optimal model for riverside well, and for plain and mountain well, the ARIMA model and Seasonal ARIMA model were selected as the optimal model. A suitable prediction model is not limited to one model due to a change in a groundwater level fluctuation pattern caused by a surrounding environment change but may change over time. Therefore, it is necessary to periodically check and revise the optimal model rather than continuously applying one selected ARIMA model. Groundwater forecasting results through time series analysis can be used for sustainable groundwater resource management.

• Water for future
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• v.28 no.3
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• pp.175-186
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• 1995

Characteristics of runoff and groundwater qualities from a pasture and field were investigated. Flumes and monitoring wells were installed and water qualities of $NO_3$-N, TP and TKN were monitored from Aug. 1993 to Aug. 1994. Runoff from the pasture which was a sandy soil with cobbles mostly formed with seeping water at the bottom of it. But once overland flow occurred because of heavy rainfall, runoff increased sharply. $NO_3$-N concentration in pasture runoff was relatively stable ranging between 0.241-3.962mg/l. TP and TKN concentrations were stable but sharply increased once overland flow occurred. $NO_3$-N concentration in pasture groundwater was relatively stable regardless of depth of monitoring wells but TP and TKN concentrations were smaller in deeper wells. Runoff from the field which was flat and covered well with Sudan grass and surface residue was relatively small and $NO_3$-N, TP and TKN concentrations in runoff were stable and seemed unaffected by flow rate. $NO_3$-N concentration in field groundwater increased at the rate of 2.2mg/l per 100 m during a growing season as groundwater flows through the field. No significant differences in TP and TKN concentrations between the upper and lower areas in field groundwater were detected.

• Journal of the Korean Association of Geographic Information Studies
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• v.9 no.3
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• pp.107-122
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• 2006

The main objective of this study is to develop a web-based Geographic Information System (GIS) application, IGIS(Integrated Groundwater Information Service System), for efficient management of groundwater data. This integrated system includes various groundwater measurements, monitoring data, well data, hydrogeochemical data, hydrogeological maps and diversely analyzed results including time series analysis data for water levels and quality. It will be used efficiently for local government officers to manage groundwater within their districts and also for drillers and investigators to develop wells and assess groundwater conditions. This web-based GIS system was implemented firstly for Cheonan and Daegu city. As a result, the system makes the efficient management, distribution and utilization of groundwater data possible by web-based GIS technology.

• Journal of Soil and Groundwater Environment
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• v.10 no.6
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• pp.32-44
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• 2005

314 pumping test data of the National Groundwater Monitoring Wells (NGMWs) are analyzed to present statistical properties of fractured-rock and alluvial aquifers of Korea such as distribution of hydraulic conductivity, empirical relations between transmissivity and specific capacity, and time-drawdown patterns of pumping and recovery test. The mean hydraulic conductivity of alluvial aquifers (1.26 m/day) is 17 times greater than that of fractured-rock aquifers (0.076 m/day). Hydraulic conductivity of fracture-rock aquifers ranges in value over 4 orders of magnitude which coincide with representative values of fractured crystalline rocks and shows distinctive differences among rock types with the lowest values for metamorphic rocks and the highest values for sedimentary rocks. In consideration of the estimated transmissivity with some simplifying assumptions, it Is likely that $32\%$ of groundwater flow for NGMWs would occur through fractured-rock aquifers and $68\%$ through alluvial aquifers. Based on 314 pairs of data, empirical relations between transmissivity and specific capacity are presented for both fractured-rock and alluvial aquifers. Depending on time-drawdown patterns during pumping and recovery test, NGMWs are classified into $4\~5$ types. Most of NCMWs $(83.7\%)$ exhibit the recharge boundary type, which call be attributed to sources of water supply such as streams adjacent to the pumping well, the vertical groundwater flux between fractured-rock and the alluvial aquifers, and the delayed yield associated with gravity drainage occurring in unconfined aquifers.

• Journal of Soil and Groundwater Environment
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• v.13 no.1
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• pp.67-76
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• 2008

In this study, a combined model of a water-table fluctuation and a soil moisture content model is proposed for the estimation of groundwater recharge rate at a given location. To evaluate the model, groundwater level data from 4 monitoring wells (Pohang Yeonil, Pohang Kibuk, Suncheon Oeseo, Hongcheon Hongcheon) of National Groundwater Monitoring Network from 1996 to 2005 and precipitation data of corresponding years are used. From the proposed methodology, the groundwater recharge rates are estimated to be from 0.5 to 61.4% for Hongcheon Hongcheon, from 1.1 to 27.4% for Pohang Yeonil, from 5.1 to 41.4% for Pohang Kibuk, and from 1.1 to 8.3% for Suncheon Oeseo. The magnitude of variation of the estimated recharge rate depends on the soil type observed near the stations. The groundwater fluctuation model used in this study includes precipitation as a unique source of water-table perturbation and there may exist corollary limitations. To improve the applicability of the proposed method, a capillary-water content constitutive model for unsaturated fractured rock media may be considered. The proposed recharge rate delineation method is physically based and uses minimum numbers of assumptions. The method may be used as a better substitute for the previous tools for delineating recharge rate of a location using water-table fluctuation method and contribute to national groundwater management plan. Further research on the spatial interpolation of the method is under progress.

• Journal of the Korean earth science society
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• v.28 no.7
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• pp.925-935
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• 2007

Water sources in volcanic Jeju Island are almost entirely dependent on groundwater because there are actually no perennial streams or rivers due to the permeable nature of surface soils derived from basaltic or trachytic rocks. Uncontrolled development of groundwater resulted in substantial water-level decline, groundwater pollution, and seawater intrusion in several places of the island. To maintain its sustainable groundwater, the provincial government has declared some parts of the island as the Special Groundwater Conservation/Management Area since 1994. Hence, all the activities for the groundwater development in the area should obtain official permit from relevant authorities. Furthermore, to acquire information on groundwater status, a network of groundwater monitoring was established to cover most of the low land and coastal areas with the installation of automatic monitoring systems since 2001. The analysis of the groundwater monitoring data indicated that the water levels had decreased at coastal area, especially in northern part of the island. Moreover, very high electrical conductivity (EC) levels and their increasing trends were observed in the eastern part, which was ascribable to seawater intrusion by intensive pumping in recent years. Water level decline and EC rise in the coastal area are expected to continue despite the present strict control on additional groundwater development.

• Journal of the Korean earth science society
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• v.29 no.5
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• pp.396-407
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• 2008

Hydrogeologic properties of a well field around middle mountainous areas in Pyosun, Jeju volcanic island were examined based on water level monitoring, geologic logging and pumping test data. Due to the alternating basaltic layers with varying permeability in the subsurface, it is difficult to analyze the hydraulic responses to artificial pumping and/or natural precipitation. The least permeable layer, detrital materials with clay, is found at a depth of 200 m below surface, but it is not an upper confining bed for lower main aquifer. Nevertheless, this layer may serve as a natural barrier to vertical percolation and to contaminant migration. Water levels of the production wells are dominantly affected by pumping frequently, while those of the remote observation wells are controlled by ambient precipitation. Results of pumping tests revealed a possible existence of horizontal anisotropy of transmissivity. However, some results of this study include inherent limitations enforced by field conditions such as the consistent of groundwater production and the set of time periods for the cessation of the pumping prior to pumping tests.