• The Journal of Engineering Geology
• /
• v.13 no.4
• /
• pp.457-474
• /
• 2003

This study aims to elucidate characteristics of groundwater level fluctuation at riverbank filtration sites in Daesan-myeon, Changwon City. Groundwater level fluctuation, river water level change and stream-aquifer interaction are very important to estimate optimal discharge rate of the pumping well. Water level contours from February 2003 to October 2003 show normal decreasing trend toward the Nakdong river with the hydraulic gradient of 0.008. However, flow reversion occurs when groundwater is discharged at the pumping wells or rise of the Nakdong river by rainfall. The fluctuation of the Nakdong river ranges 0 - 10 m msl. Autocorrelation analysis was conducted to the groundwater levels measured on the six monitoring wells (DS1, DS2, DS3, DS4, DS6 and DS7). The analyzed waterlevel data can be grouped into three: group 1 (DS1 and DS3) represents strong linearity and long memory effect, group 2 (DS1 and DS6) intermediate linearity and memory, and group 3 (DS4 and DS7) weak linearity and memory. Waterlevels of group 1 wells are relatively closely related to the change of river-water level. Those of group 2 wells are largely affected by the pumping and the river-water level, and those of group 3 wells are strongly linked to pumping.

• Economic and Environmental Geology
• /
• v.29 no.6
• /
• pp.713-724
• /
• 1996

The time-series resident solute concentrations, monitored at two field plots using the automated 144-channel TDR system by Kim (this issue), are used to investigate the dominant transport mechanism at field scale. Two models, based on contradictory assumptions for describing the solute transport in the vadose zone, are fitted to the measured mean breakthrough curves (BTCs): the deterministic one-dimensional convection-dispersion model (CDE) and the stochastic-convective lognormal transfer function model (CLT). In addition, moment analysis has been performed using the probability density functions (pdfs) of the travel time of resident concentration. Results of moment analysis have shown that the first and second time moments of resident pdf are larger than those of flux pdf. Based on the time moments, expressed in function of model parameters, variance and dispersion of resident solute travel times are derived. The relationship between variance or dispersion of solute travel time and depth has been found to be identical for both the time-series flux and resident concentrations. Based on these relationships, the two models have been tested. However, due to the significant variations of transport properties across depth, the test has led to unreliable results. Consequently, the model performance has been evaluated based on predictability of the time-series resident BTCs at other depths after calibration at the first depth. The evaluation of model predictability has resulted in a clear conclusion that for both experimental sites the CLT model gives more accurate prediction than the CDE model. This suggests that solute transport at natural field soils is more likely governed by a stream tube model concept with correlated flow than a complete mixing model. Poor prediction of CDE model is attributed to the underestimation of solute spreading and thus resulting in an overprediction of peak concentration.

• Korean Journal of Ichthyology
• /
• v.33 no.3
• /
• pp.177-183
• /
• 2021

Distribution aspects and extinction threat evaluation of the endangered species, Rhynchocypris semotilus were investigated in Goseong-gun, Gangwon-do, Korea, June 2020. Among the 12 sampling sites investigated during the study period, samples of R. semotilus were collected 268 individuals at 6 sites. The streams inhabited of R. semotilus were Songhyeoncheon (3 stations), Gojindong (2 stations) and Osodong (1 station). The main habitats of R. semotilus were uppermost and upper stream (Aa type) with 3~15 m water flow width, 0.3~1.3 m depth and high ratio boulder and cobble bottoms. The estimated age of the R. semotilus (June) based on their total length distribution indicated that 0-, 1-, 2-, 3- and more than 4-year-old were 6~27 mm, 38~59 mm, 60~75 mm, 78~93 mm and 96~125 mm, respectively, and their has matured reproductive organs over two years old. R. semotilus investigation results of the threat of extinction showed no tendency to decrease in population size, but estimated to be less than 1,000 mature individuals, with a small range of extend of occurrence (39.668 km²), area of occupancy (16 km²), and number of disconnected locations (3 locations). Therefore, R. semotilus is now considered vulnerable (VU D2) based on the IUCN Red List categories and criteria.

• Korean Journal of Environment and Ecology
• /
• v.32 no.6
• /
• pp.591-602
• /
• 2018

Clithon retropictus has been designated as an endangered wildlife Class II due to its high value as a biological indicator species capable of judging environmental quality such as salinity, water flow, and ground conditions. However, basic research on its physiological and ecological characteristics is still lacking. As such, this study intended to examine the impact of environmental conditions such as salinity and soil particle size on the size and density of Clithon retropictus at the Yeoncho river estuary. The investigation of the salinity, which is a key variable that affects the distribution of organisms in the estuary, showed that Clithon retropictus could grow at a salinity ranging from 0#x2030; (freshwater) to 25‰ (brackish water). The coarse gravel (19-75mm) tended to increase nearer the upper stream (under the Yeoncho weir), while the proportion of particles smaller than sand (less than 19mm) increased toward the downstream. The population and the size of the individuals decreased rapidly in the downstream where water stagnated near the Yeoncho weir, and the salt water joined. The results indicated that Clithon retropictus had a high tolerance to salinity, but the adaptability was weaker toward the extremes since the population, and the size tended to decrease as the salinity increased. The correlation analysis revealed that both salinity and soil particle size affected the population and individual size. The correlation between the individual size and salinity was -0.242 (P <0.01), indicating that the size decreased with increasing salinity. The correlation between individual size and coarse gravel having a particle size of 19mm or more was 0.420 (P <0.01), indicating that the size increased with increasing the particle size.

• Clean Technology
• /
• v.25 no.1
• /
• pp.1-6
• /
• 2019

Effects of the Cu and K addition and the reduction condition of Fe-based catalysts for Fischer-Tropsch reaction are studied in a continuous flow reactor in this research. The catalysts for the reaction were prepared by homogeneous precipitation followed by incipient wetness impregnation. Physicochemical properties of the $Al_2O_3$ supported Fe-based catalysts are characterized by various methods including X-ray diffraction (XRD), temperature programmed reduction (TPR), and scanning electron microscopy (SEM). Catalytic activities and stabilities of the Fe/Cu/K catalyst are investigated in time-on-stream for an extended reaction time over 216 h. It is found that a reduction of the catalysts using a mixture of CO and $H_2$ can promote their catalytic activities, attributed to the iron carbides formed on the catalysts surface by X-ray diffraction analysis. The addition of Cu induces a fast stabilization of the reaction reducing the time to reach at the steady state by enhancement of catalytic reduction. The addition of K to the catalysts increases the CO conversion, while the physical stability of catalyst decreases with potassium loading up to 5%. The Fe/Cu (5%)/K (1%) catalyst shows an enhanced long term stability for the Fischer-Tropsch reaction under the practical reaction condition, displaying about 15% decrease in the CO conversion after 120 h of the operation.

• Ecology and Resilient Infrastructure
• /
• v.6 no.2
• /
• pp.89-100
• /
• 2019

We've reviewed existing studies on the interactions among vegetation, hydrology, and geomorphology in the stream corridors, adding one more factor of vegetation in the traditional area of hydro-geomorphology. Understanding of the interactions among those three factors is important not only academically but also practically since it is related intimately to the restoration of river corridor as well as management itself. Studies of this area started from field investigations in the latter part of the 20th century and focused on the flume experiments and then computer modelling in the 1990s and 2000s. Now, it has turned again to the field investigations of specific phenomena of the vegetative-hydrologic-geomorphologic interactions in detailed micro scales. Relevant studies in Korea, however, seem to be uncommon and far behind the international status quo in spite that practically important issues related directly to this topic have been emerged. In this study, we propose, based on the extensive literature review and authors' own knowledge and experiences, a conceptual diagram expressing the interactions among vegetation, flow (water), sediment, and geomorphology. Existing relevant studies in Korea since the 1990s are classified according to the categorization in the proposed diagrams and then briefly reviewed. Finally, considering the practical issues of riparian vegetation that have emerged recently in Korea, we propose areas of investigation needed in near future such as, among others, long-term and systematic field investigations and monitoring at multiple river corridors having different attributes on vegetative-hydrologic-geomorphologic interactions, including vegetative dynamics for succession.

• Journal of Korean Society on Water Environment
• /
• v.34 no.6
• /
• pp.632-641
• /
• 2018

Algal dynamics is controlled by multiple environmental factors such as flow dynamics, water temperature, trophic level, and irradiance. Underwater irradiance penetrating from the atmosphere is exponentially decreased in water column due to absorption and scattering by water molecule and suspended particles including phytoplankton. As the exponential decrease in underwater irradiance affects algal photosynthesis, regulating their spatial distribution, it is critical to understand the light extinction characteristics to find out the mechanisms of algal dynamics more systematically. Despite the significance, the recent data have been rarely reported in the main stream areas of large rivers, Korea. In this study, the euphotic depths and light extinction coefficients were determined by monitoring the vertical variation of underwater irradiance and water quality in the main channel of Nakdong River near Dodong Seowon once a week during summer of 2016. The average values of euphotic depth and light extinction coefficient were 4.0 m and $1.3m^{-1}$, respectively. The degree of light extinction increased in turbid water due to flooding, causing an approximate 50 % decrease in euphotic depth. Also, the impact was greater than the self-shading effect during the periods of cyanobacterial bloom. The individual light extinction coefficients for background, total suspended solid and algal levels, frequently used in surface water quality modeling, were determined as $0.305m^{-1}$, $0.090m^{-1}/mg{\cdot}L^{-1}$, $0.013m^{-1}/{\mu}g{\cdot}L^{-1}$, respectively. The values estimated in this study were within or close to the ranges reported in literatures.

• Journal of Korea Water Resources Association
• /
• v.55 no.1
• /
• pp.99-109
• /
• 2022

This study was intended to suggest the applicability of stepped boulder fishway using the concept of traditional boulder weir, focusing on the problems of existing concrete pool-and-weir fishways installed in mountain streams. To achieve this purpose, a stepped boulder fishway was designed and constructed as a pilot project in consideration of ascending capacity of the selected target fishes. Under the given discharge conditions, the hydraulic characteristics of the fishway were investigated in the field, and the characteristics and ascending capacity of the fishes were compared and analyzed. The fishway had a short length and steep slope, but the mean drops between each baffle were the range of 0.15 to 0.29 m, and this range satisfied the limit condition of about 0.40 m, which was in the limit of the drop that target fishes can ascend. The mean velocities of each baffle and pool were 0.82 to 0.87 m/sec and 0.13 to 0.24 m/sec. This result satisfied the conditions of burst speed (10 to 30 times of body length) and mean velocity of the resting pool (7 to 25% of burst speed) for target fishes. Since the bottom surface of the pool formed of boulders had a gentle reverse slope and rotational flow did not occur, the efficiency of fishway can be increased, and it will also be possible to solve the maintenance problem by flushing bed materials.

• Journal of Korea Water Resources Association
• /
• v.55 no.12
• /
• pp.991-998
• /
• 2022

The purpose of this study is to develop GPU (Graphics Processing Unit) acceleration technique for 2-dimensional model and to assess the effectiveness for high resolution flood simulation in wide area In this study, GPU acceleration technique was implemented in the G2D (Grid based 2-Dimensional land surface flood model) model, using implicit scheme and uniform square grid, by using CUDA. The technique was applied to flood simulation in Jinju-si. The spatial resolution of the simulation domain is 10 m × 10 m, and the number of cells to calculate is 5,090,611. Flood period by typhoon Mitag, December 2019, was simulated. Rainfall radar data was applied to source term and measured discharge of Namgang-Dam (Ilryu-moon) and measured stream flow of Jinju-si (Oksan-gyo) were applied to boundary conditions. From this study, 2-dimensional flood model could be implemented to reproduce the measured water level in Nam-gang (Riv.). The results of GPU acceleration technique showed more faster flood simulation than the serial and parallel simulation using CPU (Central Processing Unit). This study can contribute to the study of developing GPU acceleration technique for 2-dimensional flood model using implicit scheme and simulating land surface flood in wide area.

• Journal of Korean Society of Disaster and Security
• /
• v.15 no.3
• /
• pp.41-46
• /
• 2022

Recently, the scale of flood damage occurring in urban areas is increasing due to climate change and urbanization, so various flooding analysis techniques are needed. In the Sadangcheon Stream basin, which has been continuously flooded since 2010, a basic plan for improving drainage was established using XP-SWMM and measures to prevent flooding were proposed. However, in the process of inundation analysis, the analysis considering the city's buildings was not conducted, resulting in a problem that the degree of flooding damage tends to be overestimated. Therefore, in this study, XP-SWMM was used to compare and analyze cases where buildings were not considered and designated as inactive areas. As a result of the study, it was analyzed if the building was not considered, the flood damaged area was 271,100 m² and the depth of submersion was 0.15 m, and if the building was considered inactive area, the flood damaged area was 172,900 m² and the depth of submersion was 0.32 m that it is under-estimated about 36% and an flow velocity around the building increased from 1.62 m/s to 1.83 m/s about 1.12 times.