• Journal of Soil and Groundwater Environment
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• v.25 no.4
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• pp.35-47
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• 2020

Step-drawdown test is one of the widely-used aquifer test methods to evaluate aquifer and well losses. Various approaches have been suggested to estimate well losses using the step-drawdown test data but the uncertainties associated with data interpretation and analysis still exist. In this study, we applied three different step-drawdown test analysis methods -Jacob (1947), Labadie and Helweg (1975), Gupta (1989)- to the step-drawdown test data in Seobu-myeon, Hongseong-gun, South Korea and estimated aquifer and well losses. Comparisons of different step-drawdown test analysis methods revealed that the estimated well losses showed different values depending on the applied methods and these variations are likely to be related to the limitation of the assumptions for each analysis method. Based on the detailed analysis of time-drawdown data, we performed step-drawdown test analysis after removing outlier data during the initial stage of step drawdown test. The results showed that the application of the revised time-drawdown data could substantially decrease the error of the analysis as well as the variations in the estimated well losses from different analysis methods.

• Geomechanics and Engineering
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• v.33 no.2
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• pp.195-202
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• 2023

In this study, the ground settlement in backside of retaining wall and the behavior of the retaining wall were analyzed according to the method of groundwater drawdown due to excavation by using two-dimensional(2D) finite element analysis. Numerical analysis was performed by applying 1) fixed groundwater level, 2) constant groundwater drawdown, and 3) transient groundwater drawdown. In addition, the behavior of the retaining wall according to the initial groundwater level, ground conditions, and surcharge pressure in backside of retaining wall was evaluated. Based on the numerical analysis results, it was confirmed that when the groundwater level is at 0.1H from the ground surface (H: Excavation soil height), the wall displacement and ground settlement are not affected by the method of groundwater drawdown, regardless of soil conditions (dense or loose) and surcharge pressure. On the other hand, when the groundwater level is at 0.5H from the ground surface, the method of groundwater drawdown was found to have a significant effect on wall displacement and ground settlement. In this case, the difference in ground settlement presents by up to 4 times depending on the method of groundwater drawdown, and the surcharge load could increase the ground settlement by up to 1.5 times.

• Economic and Environmental Geology
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• v.26 no.4
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• pp.541-549
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• 1993

The main goal of this paper is to determine hydraulic properties and to predict drawdown for the efficient and stable development of groundwater in the Daejong-Chun area, North of Kyungsang-Do. Based on geological survey and analysis of well logging data conducted in 1991, it is found that the type of aquifer of this area is considered to be an anisotropic unconfined aquifer with saturated thickness of 19.8 m. In order to characterize this aquifer pumping test was conducted, and the resulting drawdown data were utilized for the analysis by applying both type curve matching technique and semi-log straight line method. As a result, the average specific yield of this aquifer is estimated as 32.3%, and the average ratio of $K_H$ to $K_V$ is only 2.7, which means that gravitational effect is not significant factor for this type of aquifer. For the validation of the estimated hydraulic properties, the analytical model which was developed with Newton-Raphson iteration procedure in this study, was employed to generate the drawdown. And, the resulting drawdown was compared against actual drawdown data and it shows the excellent matches. The actual drawdown data for 9 hours of pumping were used for history matching purposes and relatively satisfactory matches were achieved in this match. Then, the model was run by using the tuned parameters that are obtained during history matching stage, and the drawdown was predicted for the next 30 years of pumping with $3,000m^3/day$ of constant pumping rate. Its result indicates that the drawdown was stabilized as 1.41 m from 20 days with $3,000m^3/day$ of constant pumping rate, which is the required amount of water to be safely supplied to this area.

• Journal of Ecology and Environment
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• v.43 no.2
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• pp.271-281
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• 2019

Background: The plant communities within reservoir drawdown zones are ecologically important as they provide a range of ecosystem services such as stabilizing the shoreline, improving water quality, enhancing biodiversity, and mitigating climate change. The aim of the study was therefore to identify the major environmental factors affecting these plant communities within the drawdown zone of the Soyangho Reservoir in South Korea, which experiences a monsoonal climate, and thereafter to (1) elucidate the plant species responses and (2) compare the soil seedbank composition along main environmental gradients. Results: Two main environmental gradients affecting the plant community structure were identified within the drawdown zone; these were a vertical and longitudinal gradient. On the vertical dimension, a hydrological gradient of flood/exposure, the annual-dominated plant community near the water edge changed to a perennial-dominated community at the highest elevation. On the longitudinal dimension from the dam to the upstream, plant species composition changed from an upland forest-edge community to a lowland riverine community, and this was correlated with slope degree, soil particle size, and soil moisture content. Simultaneously, the composition of the soil seedbank was separated along the vertical gradient of the drawdown zone, with mainly annuals near the water edge and some perennials at higher elevations. The species composition similarity between the seedbank and extant vegetation was greater in the annual communities at low elevation than in the perennial communities at higher elevation. Conclusions: The structures of plant community and soil seedbank in the drawdown zone of a monsoonal riverine reservoir were changed first along the vertical and secondly along the longitudinal gradients. The soil seedbank could play an important role on the vegetation regeneration after the disturbances of flood/exposure in the drawdown zone. These results indicate that it is important to understand the vertical and longitudinal environmental gradients affecting shoreline plant community structure and the role of soil seedbanks on the rapid vegetation regeneration for conserving and restoring the drawdown zone of a monsoonal reservoir.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.9
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• pp.205-213
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• 2003

This study describes the mathematical equation of drawdown test model and introduces the experimental test apparatus and procedure to estimate the desorption rate ratio of a filter. The characteristics of a hydraulic filtration system of drawdown test were demonstrated by numerical simulation for various properties of filters and operation conditions. Experiments for three kinds of fuel filters were conducted according to the proposed test method. And the test results of desorption rate ratio were compared with those values anticipated in precedent multipass filtration tests. Experimental results revealed the validation of drawdown test method proposed in this study. Domestic fuel filter yielded high desorption rate ratio comparing with other foreign products, which means that the Beta ratio decreases a lot during the test. The results also showed that filtration system model could be developed including desorption rate ratio to estimate the variable Beta ratio in service life.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.438-441
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• 2006

The groundwater level was originally above the surface at the Onyang spa area. However, it is now 98-138m depth below the surface deu to the artificial pumping from boreholes. The fluctuations of the piezometric head were observed in 4 boreholes. Transmissivity estimated from the pumping rate and the drawdown is about $577.51 m^2/day$ The transmissivity of Onyang spa area is much larger than common values of fractured aqui for the drawdown of the piezometric head by artificial pumping is widely spreaded out in that area. The drawdown related to each pumping rate was analyzed and the formula between drawdown and pumping rate was made by a regression analysis. The formula can be applied for the condition of enough groundwater flowing into the Onyang spa area

• Journal of Ecology and Environment
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• v.43 no.2
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• pp.219-225
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• 2019

In order to assess the impacts of drawdown for land-use change on a Sphagnum-marsh, we compared the vegetation and flora of the wetland before and after the drawdown with focusing on the population of Sphagnum palustre L. Remarkable changes in the coverage of S. palustre and the major vegetational components of the wetland were observed. The coverage of S. palustre markedly decreased by about 75% (from approx. 247 ㎥ in 2011 to approx. 62 ㎥ in 2015) after the drawdown. Tree species such as Salix spp. extended (from about 70% to about 83% in the total coverage of the wetland), whereas herbaceous species shrunk after the drawdown. Upland-inhabiting species such as obligate plants for uplands (OBU) increased, whereas wetland-inhabiting species such as facultative plants for wetlands (FACW) and OBW decreased in terms of vegetational coverage. The total number of plant species decreased from 70 species to 62 species after the drawdown, including the disappearance of some wetland-inhabiting species from the wetland. We suggest that the attention for further studies on the abandoned paddy terraces (APTs) and effort for the management and conservation of APTs and APT-inhabiting species that are vulnerable to human-induced disturbances have to be paid more.

• Nuclear Engineering and Technology
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• v.44 no.7
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• pp.767-772
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• 2012

In support of optimizing electrorefining technology for treating spent nuclear fuel, lithium drawdown has been investigated for separating actinides from molten salt electrolyte. Drawdown reaction selectivity is a major issue that requires investigation, since the goal is to remove actinides while leaving the fission products and other components in the salt. A series of lithium drawdown tests with surrogate fission product chlorides was run to obtain selectivity data with non-radioactive salts, develop a predictive model, and draw conclusions about the viability of using this process with actinide-loaded salt. Results of tests with CsCl, $LaCl_3$, $CeCl_3$, and $NdCl_3$ are reported here. Equilibrium was typically achieved in less than 10 hours of contact between lithium metal and molten salt under well-stirred conditions. Maintaining low oxygen and water impurity concentrations (<10 ppm) in the atmosphere was observed to be critical to minimize side reactions and maintain stable salt compositions. An equilibrium model has been formulated and fit to the experimental data. Good fits to the data were achieved. Based on analysis and results obtained to date, it is concluded that clean separation between minor actinides and lanthanides will be difficult to achieve using lithium drawdown.

• Journal of Soil and Groundwater Environment
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• v.10 no.2
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• pp.59-65
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• 2005

Step-drawdown test has been generally conducted to evaluate productivity or efficiency of both aquifer and well. In general step-drawdown test, pumping with a low constant discharge rate is conducted in the first stage until the drawdown within the well stabilizes. And then the groundwater is pumped with a higher rate in the next step until the drawdown stabilizes once more. This process is repeated at least three times (steps), with the equal duration. In this paper we tried to review some critical problems related to the step-drawdown test, which were revealed in the process of field practices and analyses. The problems, referred in this paper are mainly associated with the incorrect conceptual approach for analysis and incomplete data collection in the field test.

• Ecology and Resilient Infrastructure
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• v.5 no.2
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• pp.94-104
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• 2018

The Soyangho Reservoir in Korea has a large drawdown zone, with an annual maximum water level fluctuation of 37 m due to dam operations to maintain a stable water supply and control flooding, especially during the monsoon period. The floristic composition, distribution and biomass of the major plant communities in the drawdown zone of the Soyangho Reservoir were assessed in order to understand their responses to the wide water level fluctuation. Species richness of vascular plants was low, and species composition was dominated by herbaceous annuals. Principal coordinates analysis using both flora and environmental data identified slope angle and the distance from the dam as important factors determining floristic composition. The species richness was low in the steep drawdown zone close to the dam, where much of the soil surface was almost devoid of vegetation. In shallower slopes, distant from the dam plant communities composed of mainly annuals were found. The large fluctuation in water level exposed soil where these annuals could establish. An overall biomass of 122 t (metric tons) Dry Matter was estimated for the reservoir, containing ca 3.6 t N (nitrogen) and ca 0.3 t P (phosphorus); the role of the vegetation of the drawdown zone in carbon sequestration and water pollution were briefly discussed.