• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2000.11a
• /
• pp.232-236
• /
• 2000

Multi-regression statistical analyses were applied for the water quality data of shallow alluvial ground water (n = 47) collected from the Youngdeok area, in order to quantitatively generalize the natural (non-anthropogenic) causes of regional water quality variation. Seven samples having the high contamination index ( $C_{a}$ > 3) reflect the striong effects by anthropogenic activity. Most of the alluvial groundwaters have acquired their quality primarily due to the dissolution of carbonate minerals. The results of multi-regression analysis show that chlorine is mainly derived from seawater effect. Sulfur isotopic compositions of dissolved sulfur and the S $O_4$/Cl ratio also enable us to discriminate the samples (n = 18) which are affected by atmospheric input of marine aerosol (sea-spray) and also by mixing between freshwater and seawater. Hydrogen and oxygen isotope data of the samples collected lie close to the local meteoric water line obtained from nearby Pohang city but has lower slope (5.45) on the $\delta$D-$^{18}$ O plot, indicating that alluvial groundwater was recharged from infiltrated meteoric water which has undergone some degree of kinetic evaporation. The estimated initial isotopic composition of the recharged water ($\delta$D = -74.8$^{0}$ /$_{00}$, $\delta$$^{18}$ O = -10.8$^{[-1000]}$ /$_{[-1000]}$ ) suggests that the alluvial ground water recharge largely occurs during summer storm events.s.s.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.12 no.3
• /
• pp.191-198
• /
• 2014

Using results of groundwater flow system modeling for a hypothetical deep geological repository site, a distribution of groundwater flow rates at the disposal depth was analyzed and a method of applying this distribution to a safety assessment for a disposal of radioactive wastes was suggested. The distribution of groundwater flow rates was produced by hydraulic heads simulated from regional and local scale groundwater flow models for the hypothetical disposal site. The flow rates at the locations where deposition holes would be located were estimated. These rates were normalized by the maximum of the flow rates in order to probabilistically illustrate a possibility of canister failures at the deposition holes. From the normalized distribution, probabilistic expectations for mass discharges of radionuclides released from the canisters assumed to be failed were calculated and compared with those deterministically estimated under the assumption that the canisters at the same deposition holes were definitely failed. The suggested method can be contributed to constructing a methodology for safety assessment of a geological repository by reflecting natural conditions of a disposal site in more detail.

• Economic and Environmental Geology
• /
• v.22 no.4
• /
• pp.381-393
• /
• 1989

Hydrogeological modelling was performed to evaluate groundwater flow system in Igsan Area. The study area extends over $790km^2$. The geology consists of Jurassic Daebo granite and gneissose granite and Precambrian metamorphic rocks. The capability of pumping yield is the highest in gneissose granite region among them due to comparatively thick weathered zone with thickness ranging from 10m to 25m. The Colorado State University Finite Difference Model was used for the model simulation. The model was divided into 28 rows and 31 columns with variable grid spacing. The model was calibrated under steady-state and unsteady-state conditions. In the steady-state simulation, the model results were compared with measured water table contours in September 1985 with determining hydraulic conductivities and net recharge rates during rainy season. Unsteady state simulation was done to know the aquifer response due to groundwater abstraction. The non- steady state calibration was conducted to determine the distribution and magnitudes of specific yields and discharge/recharge rates during dry season as matching water level altitudes in May 1986. The calibrated model was used to simulate water level vaiation caused by groundwater withdrawal and natural recharge from 1 October, 1985 until 30 September, 1995. The calibrated model can be used to groundwater development schemes on regional groundwater levels, but it cannot be used to simulate local groundwater level change at a specific site.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2011.05a
• /
• pp.14-14
• /
• 2011

Groundwater in the Waikatoregion is a valuable resource for agriculture, water supply, forestry and industries. The 434,000 ha study area comprises the upper Waikato River catchment from the outflow of Lake Taupo (New Zealand's largest lake) through to Lake Karapiro (a man-made hydro lake with high recreational value) (Figure 1). Water quality in the area is naturally high. However, there are indications that this quality is deteriorating as a result of land use intensification and deforestation. Compounding this concern for decision makers is the lag time between land use changes and the realisation of effects on groundwater and surface water quality. It is expected that the effects of land use changes have not yet fully manifested, and additional intensification may take decadesto fully develop, further compounding the deterioration. Consequently, Environment Waikato (EW) have proposed a programme of work to develop a groundwater model to assist managing water quality and appropriate policy development within the catchment. One of the most important and critical decisions of any modelling exercise is the choice of the modelling platform to be used. It must not inhibit future decision making and scenario exploration and needs to allow as accurate representation of reality as feasible. With this in mind, EW requested that two modelling platforms, MODFLOW/MT3DMS and FEFLOW, be assessed for their ability to deliver the long-term modelling objectives for this project. The two platforms were compared alongside various selection criteria including complexity of model set-up and development, computational burden, ease and accuracy of representing surface water-groundwater interactions, precision in predictive scenarios and ease with which the model input and output files could be interrogated. This latter criteria is essential for the thorough assessment of predictive uncertainty with third-party software, such as PEST. This paper will focus on the attributes of each modelling platform and the comparison of the two approaches against the key criteria in the selection process. Primarily due to the ease of handling and developing input files and interrogating output files, MODFLOW/MT3DMS was selected as the preferred platform. Other advantages and disadvantages of the two modelling platforms were somewhat balanced. A preliminary regional groundwater numerical model of the study area was subsequently constructed. The model simulates steady state groundwater and surface water flows using MODFLOW and transient contaminant transport with MT3DMS, focussing on nitrate nitrogen (as a conservative solute). Geological information for this project was provided by GNS Science. Professional peer review was completed by Dr. Vince Bidwell (of Lincoln Environmental).

• Journal of the Korean association of regional geographers
• /
• v.10 no.3
• /
• pp.568-578
• /
• 2004

This study is aimed at investigating floodgate characteristics and environmental issues in Gwangjucheon and examining possible problems of expanding river maintenance water being carried on in the context of river recovery works. In general, the obtained results show the following. The treatment water provisioned in the restoration project of the drying stream going through the water circulation device can pollute the land and groundwater in the Gwangjucheon Basin. Besides, although about $17,565m^3$/day of water is available in the upper ground, most of it go to the junction and exhausting directly to the waste water treatment or going into the groundwater. Because of the drying stream, the amount of water going to the ground is increased. Therefore, efficient land use along with regulations to protect cultivated land and ensure recovery works of city stream through the recovery of water circulation by constructing and expanding a special drainage system are of vital importance.

• Journal of Soil and Groundwater Environment
• /
• v.22 no.6
• /
• pp.29-36
• /
• 2017

Universal soil loss equation (USLE) has been frequently employed to estimate potential soil loss in land since it was developed based on the statewide data measured and collected in the United States. The equation is an empirical model mainly used for U.S. soil, thus it has been recently modified to reflect Korean soil conditions and named as Korean Soil Loss Equation (KORSLE). The modified equation was implemented in ArcGIS software, and used for estimation of potential soil loss from 2003 to 2016 in the thirty-eight Water Protection Districts. Five out of the thirty-eight districts were identified as the area of potential soil erosion most severly. In those five districts, potential soil erosion were estimated to be more than 50 Mg/ha/year that requires site investigation under supervision of the Korean Ministry of Environment. Distinctive site characteristics were found in the potential soil loss estimation such that the districts of low potential soil loss had low five factors in the aggregate. However, if one of more factors are dominantly large, the potential soil loss significantly increased. This study provides a useful tool to identify the potential areas for soil erosion and the important factors that play an important role in the estimation process.

• Journal of the Korean Society of Groundwater Environment
• /
• v.4 no.1
• /
• pp.5-13
• /
• 1997

The Island of Cheju plans massive ground water development to meet predicted water demand. Effective management of ground water resources requires impact assessment study. Due to the nature of the island, effects of sea water must be considered. In this work, salt water intrusion, due to hypothetical ground water development in Eastern and Central Cheju Watersheds, is predicted using a sharp-interface model. The model considers simultaneously hydrodynamics of both freshwater and saltwater. The hypothetical ground water development was designed such that it follows closely the regional ground water development plan. The numerical model predicted that the saltwater wedge may intude over 1km depending on the location. This observation leaves doubt on impact assement studies based on freshwater-flow only modeling.

• Journal of Soil and Groundwater Environment
• /
• v.17 no.2
• /
• pp.62-70
• /
• 2012

Rainfall, on Jeju Island varies regionally in relation to Mt. Halla with higher rainfall within southern area and lower in western area, and its variability is expected to expand according to the climate change scenario. Non-parametric trend analysis for rainfall, using both historic (1971-2010) and simulated (2011-2100) data assuming the A1B emissions scenario, shows regionally increasing trends with time. In perspective of agricultural land use, area for market garden including various crop types with high water demand is increasing over the Island, especially in the western area with lower rainfall compared to southern area. On the other hand, area for fruit including mandarin and kiwi with low water demand is widely distributed over southern and northern part having higher rainfall. These regional disparity of water demand/supply may be more affected by extreme events such as drought and heavy rainfall that has not yet been considered. Therefore, it is necessary to make policies for water resource management considering both demand and supply in different regions with climate change impacts over Jeju Island.

• Journal of Korean Society of Rural Planning
• /
• v.26 no.2
• /
• pp.51-59
• /
• 2020

In this study, we analyzed the characteristics of 511 agricultural districts through statistical data, and classify these districts as the vulnerable area to drought through correlation and cluster analysis. The criteria for classification was related to ground-water recharge, irrigation water demand, and water supply. As a result, 8 types of agricultural districts were extracted. For example, the type 1 indicated the high priority area for ground-water development, thus the districts which were classified as type 1 showed ground-water use was less than 80 % of maximum capacity, and irrigation water supply was only 37.5 % and 76.5 % of irrigation water demand in upland and paddy field, respectively. As a result, 44 of 511 districts were classified as type 1.36 districts (types 5-8) were areas where groundwater development is limited. The results of this study are expected to provide useful information for establishing the direction of the rural area development project in connection with the revitalization of policy of people return to rural area.

• Journal of Soil and Groundwater Environment
• /
• v.24 no.5
• /
• pp.31-41
• /
• 2019

In 2013, the Ministry of Environment in South Korea promulgated a new regulatory bulletin that contained revised enforcement ordinance on soil management protocols. The bulletin recommends the use of Universal Soil Loss Equation (USLE) for the soil erosion estimation, but USLE has limited applicability in prediction of soil erosion because it does not allow direct estimation of actual mass of soil erosion. Therefore, there is a great need of revising the protocol to allow direct comparison between the measured and estimated values of soil erosion. The Korean Soil Loss Equation (KORSLE) was developed recently and used to estimate soil loss in two fields as an alternative to existing USLE model. KORSLE was applied to estimate monthly rainfall erosivity indices as well as temporal variation in potential soil loss. The estimated potential soil loss by KORSLE was adjusted with correction factor for direct comparison with measured soil erosion. The result was reasonable since Nash-Stucliff efficiency were 0.8020 in calibration and 0.5089 in validation. The results suggest that KORSLE is an appropriate model as an alternative to USLE to predict soil erosion at field scale.