Basins In Korea Research Articles

A new blind groundwater-dwelling genus of the Cladocera (Crustacea: Branchiopoda) from the Korean Peninsula.

Groundwater-dwelling Cladocera are to date known only from the caves and hyporheic zones of the rivers in Europe (Belgium, England, France, Bosnia and Herzegovina, Macedonia, Slovenia, Spain), Turkey (European part) and Arabian Peninsula (Yemen). All these animals belong to the subfamily Aloninae Dybowski & Grochowski of the family Chydoridae Dybowski & Grochowski (Cladocera: Anomopoda). Examination of some samples collected by our colleagues - experts in Copepoda, Bathynellidae and Amphipoda-in South Korea led us to discovery of a new stygobiotic alonine genus, which is also the first record of a groundwater-dwelling cladoceran in Asia. Aims of this paper are: (1) to describe Korealona gen. nov., represented by two species, Korealona karanovici gen. nov., sp. nov. found in three different localities, and K. choi sp. nov., also found in three different localities; and (2) to discuss its differences from other genera of this subfamily and possible phylogenetic position of this genus among the aloninse. Distribution ranges of two species of Korealona gen. nov. are not unequivocally associated with present-day main river basins in Korea, but more sampling efforts are needed for final conclusions on their distribution ranges in Korea and closest countries and understanding of the genus evolutionary history.

Application of real option analysis for planning under climate change uncertainty: a case study for evaluation of flood mitigation plans in Korea

With concerns regarding global climate change increasing, recent studies on adapting to nonstationary climate change recommended a different planning strategy that could spread risks. Uncertainty in global climate change should be considered in any decision-making processes for flood mitigation strategies, especially in areas within a monsoon climate regime. This study applied a novel planning method called real option analysis (ROA) to an important water resources planning practice in Korea. The proposed method can easily be applied to other watersheds that are threatened by flood risk under climate change. ROA offers flexibility for decision-makers to reflect uncertainty at every stage during the project planning period. We successfully implemented ROA using a binomial tree model, including two real options—delay and abandon—to evaluate flood mitigation alternatives for the Yeongsan River Basin in Korea. The priority ranking of the four alternatives between the traditional discount cash flow (DCF) and ROA remained the same; however, two alternatives that were assessed as economically infeasible using DCF, were economically feasible using ROA. The binomial decision trees generated in this study are expected to be informative for decision-makers to conceptualize their adaptive planning procedure.

Interrelationship between geochemical elements of sediment and groundwater at Samrak Park Delta of Nakdong River Basin in Korea: multivariate statistical analyses and artificial neural network approaches

This research was conducted at Samrak Park Delta of Nakdong River Basin in Busan Metropolitan City, Korea. The main objective of this study was to evaluate the interrelationship of geochemical elements in sediments and groundwater through multivariate statistical analyses and a multilayer perceptron artificial neural network model. The mean concentrations of chemical elements were Si (46%), Fe (16.9%), Al (15.7%), K (7.5%) and Ca (4.5%) in sediments, and Na (8650 mg/L), Mg (999 mg/L), Ca (432 mg/L), K (293 mg/L) and Cl (17,640 mg/L) in groundwater, respectively. The principal component analysis produced 3 kinds of factors with the variances of 63.37, 27.02 and 9.62%, respectively. It is suggested that the chemical components of sediments and groundwater were mainly originated from source rocks and seawater intrusion, with the minor impacts of irrigation and industry. Cluster analysis also showed that chemical elements were mainly controlled by the natural geogenic sources and seawater intrusion. Multilayer perceptron of artificial neural network (ANN) presented the good interrelationship between sediment and groundwater. The determination coefficients (R 2) between ANN predicted values and observed values in groundwater showed the high values of 0.61–0.97 except Mg, Mn and Sr. It is revealed that the chemical components of sediment and groundwater were derived from local geological origin and from the minor impact of anthropogenic sources. Multivariate analyses and ANN contributed to the identification of the mutual relationship between the geochemical elements of sediment and those of groundwater.

Effect of Climate Change on Environmental Flow Components and Physical Habitats

The quantity and timing of runoff are critical components for the water supply, water quality, and ecological interaction of river systems (Poff, et al., 1997). Five components of the flow regime (magnitude, frequency, duration, timing, and rate of change) can directly and indirectly impact an aquatic ecosystem. (Karr, 1991; Poff, et al., 1997). Due to the recent phenomenon of climate change, the timing and pattern of rainfall has changed and affected the flow regime of certain basins. Hence, in this research, the future impact of climate change on the river flow regime and aquatic ecosystem of the Mangyeong River, a medium-sized basin in Korea, has been quantified by analysis of environmental flow components and physical habitat modeling. Consequently, it is predicted that there will be crucial changes in the material conditions related to the river flow regime, and the risk of ecological environmental changes will greatly increase. KeywordsClimate Change; EFCs; CSI; Environmental Flow Components

Development of an ecological impact assessment model for dam construction

The purpose of this study was to develop a model for assessing the ecological value of a dam reservoir. Various evaluable characteristics (“elements”) that influence the ecology of the target area around the dam were grouped into three classes: (1) physical elements, such as altitude, slope, and aspect; (2) vegetation elements, such as forest physiognomy, vegetation type, age class, diameter at breast height (DBH) class, and density; and (3) habitat elements, such as ecological conditions, vegetation conservation classification, and frequency of wildlife appearances. The evaluation standard was quantified considering the ecological function of each element. The developed assessment model was applied to the Yeongju Dam in the Nakdong River basin in Korea. This study assumed that the ecological condition before the dam construction was 100 %. The results of this study showed that the physical, vegetation, and habitat elements were downgraded to 82.8, 95.5, and 90.7 %, respectively, after the construction of the dam. The overall ecological value was estimated to be 90.0 % and thus decreased by 10.0 % due to dam construction. Additionally, by combining the results for the evaluation elements, an ecologically healthy area was selected. The results of this study should prove useful for quantifying ecological impact and for establishing an ecological restoration plan for dam reservoirs.

Evaluation of Error Indices of Radar Rain Rate Targeting Rainfall-Runoff Analysis

AbstractThis study evaluates several error indices of the radar rain rate from the viewpoint of the accuracy of rainfall-runoff analysis. The error indices considered in this study are the mean error (ME), mean absolute error (MAE), normalized standard deviation (NSD), correlation coefficient (CC), bias (BS), and radar rain rate quality criterion (RRQC). These indices were analyzed using the concept of sum of squares (SS) and mean squares (MS) in the analysis of variance (ANOVA), which explains how the bias and random error of the radar rain rate are combined in an error index. Also, these error indices were linked to the errors in the runoff result, such as the total runoff volume, peak flow, and peak time. As an application, two dam basins in Korea were selected, the Chungju Dam basin and the Namgang Dam basin. The radar rain rates from Gwangdeoksan Radar and Gudeoksan Radar were used as input for the rainfall-runoff analysis. Six different rainfall events were applied to secure various rainfall types. ...

Assessment of the Impacts of Global Climate Change and Regional Water Projects on Streamflow Characteristics in the Geum River Basin in Korea

The impacts of two factors on future regional-scale runoff were assessed: the external factor of climate change and the internal factor of a recently completed large-scale water resources project. A rainfall-runoff model was built (using the Soil and Water Assessment Tool, SWAT) for the Geum River, where three weirs were recently constructed along the main stream. RCP (Representative Concentration Pathways) climate change scenarios from the HadGEM3-RA RCM model were used to generate future climate scenarios, and daily runoff series were constructed based on the SWAT model. The indicators of the hydrologic alteration (IHA) program was used to carry out a quantitative assessment on the variability of runoff during two future periods (2011–2050, 2051–2100) compared to a reference period (1981–2006). Analyses of changes in the runoff characteristics of the lower Geum River showed that climate change is likely to lead to an increase of the future runoff ratio and that weirs contributed to an increase in the minimum discharge and a decrease in the maximum discharge. The influence of the weirs on the runoff characteristics of the Geum River basin was projected to be greater than that of climate change.

Novel apparatus to measure the low-permeability and porosity in tight gas reservoir

This study proposes a new apparatus which can simultaneously measure the physical properties such as low-permeability and porosity in a tight gas reservoir. The apparatus can also measure bi-directional permeability efficiently. The measurement of bi-directional permeability is designed in consideration of flow direction which can cause different results by heterogeneity. Using the apparatus, the experiments have been carried out to measure the low-permeability and porosity of three tight sand core samples which are from Gyeongsang sedimentary basin in Korea. As the results, the porosity ranges from 5.63% to 11% and the permeability measured in forward and reverse direction is 0.0004 md and 0.0005 md for TS-1, 0.0007 md and 0.0011 md for TS-2, and 0.0062 md and 0.007 md for TS-3, respectively. To investigate the effect of geological characteristics inside core sample on rock properties, X-ray scan of the core samples was taken by Microfocus X-ray CT. Obviously, the value of permeability and porosity are subject to geological features such as micro-crack. This means that the micro-crack plays an important factor in terms of permeability variation by its direction and length in a tight gas reservoir. For verification of measurement accuracy, regression analysis was carried out using the dimensionless pseudo-pressure between the measured data and analytical model. As the results, it is shown that both are approximately equal in terms of permeability and porosity.

Assessment of Meteorological Drought in Korea under Climate Change

Drought has become one of the most important elements for water resources planning and management in Korea. The objective of this study is to estimate the spatial distribution of drought and change in the drought characteristics over time due to climate change. For the spatial characterization of drought, the standardized precipitation index (SPI) is calculated from the 45 observatories in Korea and the spatial distribution is also estimated based on the joint probability analysis using the copula method. To analyze the effect of climate change, spatial distribution of drought in the future is analyzed using the SPI time series calculated from Representative Concentration Pathways (RCPs) scenarios and HADGEM3-RA regional climate model. The results show that the Youngsan River and the northwest of Nakdong River basins in Korea have nearly doubled drought amount compared to the present and are most vulnerable to drought in near future (2016 to 2039 years).

Evaluation of physico-chemical parameters in water and total heavy metals in sediments at Nakdong River Basin, Korea

Fourteen water and sediment samples were collected from the Nakdong River Basin in Korea to evaluate the physico-chemical parameters (pH, dissolved oxygen, chemical oxygen demand, biological oxygen demand, total organic carbon) in water and total heavy metals (Cu, Zn, Pb, Cd, As) in surface sediments. The assessment of physico-chemical parameters indicates that river water and sediments in the study area were strongly impacted by industrial wastewater, irrigational effluents and domestic sewage. The overall average concentrations of metals in sediments were Cu (6.41 mg/kg), Cd (0.11 mg/kg), Pb (4.72 mg/kg), Zn (16.8 mg/kg), As (0.19 mg/kg), and the order of the concentrations was Zn > Cu > Pb > As > Cd. Geo-accumulation index (Igeo) indicates that most of samples fall at unpolluted to medium category, while contamination factor values fall at the medium to very high pollution zone. Pollution load index also suggests that all samples fall at progressive pollution sector. Multivariate statistical analysis and pollution index methods were helpful for the classification on the basis of the contamination sources and origin of heavy metals. In conclusion, this study clearly infers the fact that the cause of metal pollution in this region is mainly due to the effluents discharged from factories, agricultural fields and sewers.

부하지속곡선(Load Duration Curve; LDC)을 이용한 한강수계 오염총량관리 목표수질 평가방법 적용 방안

Water quality in four major river basin in Korea was managed with Total Maximum Daily Load (TMDL) System. The unit watershed in TMDL system has been evaluated with Target Water Quality (TWQ) assessment using average water quality, without considering its volume of water quantity. As results, although unit watershed are obtained its TWQ, its allocated loads were not satisfied and vice versa. To solve these problems, a number of TWQ assessments with using Load Duration Curve (LDC) have been studied at other watersheds. The purpose of this study was to evaluate achievement of TWQ with Flow Duration Curve (FDC) and Load Duration Curve(LDC) at 26 unit watersheds in Han river basin. The results showed that achievement rates in TWQ assessment with current method and with LDC were 50~56 % and 69~73%, respectively. Because of increasing about 20% of achievement rates with using LDC, the number of exceeded unit watershed at Han river Basin was decreased about 4~6 unit watersheds.

개별배출시설 삭감잠재량 분석을 통한 수질오염총량제의 민간참여 활성화 방안 연구

AbstractFour major river basin in Korea has been managed with Total Maximum Daily Load(TMDL) System. Water quality indicators as targeted pollutants for TMDL were BOD and TP. In order to satisfy water quality criteria, government allocation using public treatment facilities and its action plan has been used. However, the role to improve water quality were recently faced to its limitation. It is time to require the role of non-government allocation in private discharge facilities to control good water quality. This study investigated three different scenarios in reduction demands of non-government allocations about industry and private sewages. The three different scenarios were discharge under 1) legal water quality standard, 2) water quality level in 2011 and 3) current water quality level with maximum value in group. The results showed that reduction potential in water discharge for TP indicator was 1,118kg/day, under second scenario with 20% of deduction. This results arrived at 42% of whole reduction potential costs and 0.012mg/L improvement in water quality. In conclusion, to intrigue voluntary participation in non-government allocation, various benefits such as tax reduction, tax exemption, and water quality trading should be provided.Key words: Non-government allocation, Private discharge facilities, Reduction potential, Total Maximum Daily Load (TMDL)

Application of the Entropy Method to Select Calibration Sites for Hydrological Modeling

Selecting an optimum number of calibration sites for hydrological modeling is challenging. Modelers often spend a lot of time and effort on trial and error because there is no guide. We propose a novel entropy method to automate the selection of the optimum combination of calibration sites. To illustrate, the proposed entropy method is applied using discharge data from one river basin in Korea. First, different combinations of discharge-gauging sites were grouped based on the maximum information estimated by the entropy method. Then, a hydrological model was set up for the study basin and was calibrated by estimating optimal parameters using a genetic algorithm at the discharge-gauging sites. The calibration result confirmed that the model’s performance was best when it was calibrated using the site number and combination suggested by the entropy method. In addition, the entropy method was useful in reducing the time and effort of model calibration. Therefore, we suggest and confirm the applicability of the entropy method in selecting calibration sites for hydrological modeling.

Three-dimensional geologic modeling of the Pohang Basin in Korea for geologic storage of carbon dioxide

Three-dimensional geologic modeling of the Pohang Basin in Korea for geologic storage of carbon dioxide

Development and implementation of river‐routing process module in a regional climate model and its evaluation in Korean river basins

AbstractThis study assessed the potential for river discharge simulation by implementing an online river‐routing scheme into the regional climate model (RCM) framework as a unified subroutine module and investigated the sensitivity of simulated river flows in response to changes in spatial resolutions in RCM and river‐routing scheme. The river‐routing scheme gathers runoff from the RCM and advects them horizontally along the river drainage network. The dynamical downscaling simulations were driven by reanalysis at the boundaries for the period of 2000–2010, using different grid sizes for RCM (50 and 12.5 km) and for river‐routing scheme (0.5°, 0.25°, and 0.125°). Simulated river discharge was evaluated throughout the three largest river basins in Korea. The simulation results showed potential for river discharge modeling in the RCM framework. The model generally captured the seasonal and monthly variabilities, and the daily scale peaks. From the resolution sensitivity experiments, it was confirmed that high‐resolution RCM enhances the reproducibility of river discharge; however, the lack of sophistication of the current river‐routing scheme, which was originally developed for continental and macroscale application, mitigates taking advantage of enhanced resolution in river model. On the basis of our findings and experiences in this study, we revealed several considerable issues for future developments of river simulation in the RCM framework.

Experimental apparatus and method to investigate permeability and porosity of shale matrix from Haenam Basin in Korea

This study presents a new apparatus, which can simultaneously measure petrophysical properties such as low-permeability and porosity in a shale gas reservoir. Using the apparatus, the experiments have been performed to measure the low-permeability and porosity of three shale core samples, which are from Haenam Basin in Korea. As for the experimental results, porosity ranges from 4.65 to 11.6 % and the permeability measured in forward and reverse direction is 1.27E−16 and 1.32E−16 m2 for HS-1, 1.65E−17 and 1.77E−17 m2 for HS-2, and 6.91E−18 and 7.90E−18 m2 for HS-3, respectively. As a validation of measurement, regression analysis was carried out using the dimensionless pseudo-pressure between the measured data and analytical solution. The results showed that correlation coefficient of dimensionless pseudo-pressure increased to 0.95 in upstream and downstream reservoirs. From the positive results, it is found that both are approximately equal in terms of permeability and porosity. To represent the effect of geological features inside core sample on permeability and porosity, X-ray scan of the shale core samples was taken by Microfocus X-ray CT. Clearly, the value of permeability is subject to geological features such as micro-crack. This means that the micro-crack acts as an important factor in terms of permeability variation by its direction and length in a shale gas reservoir.

A Natural Hybrid of Intergeneric Mating between a Female Pungtungia herzi and a Male Pseudorasbora parva (Cypriniformes: Cyprinidae)

A natural hybrid of a probable intergeneric mating between the striped shiner Pungtungia herzi and the stone morocco Pseudorasbora parva (Cypriniformes: Cyprinidae) was captured in the Geumho River, a tributary of the Nakdong River basin in Korea. Morphological characters and DNA sequences were analyzed to verify its hybrid state and identify the parentage of its parent species. The hybrid exhibited a phenotypic intermediacy between the two parent species in the number of vertebrae and the mouth shape. Out of 1,488 base pair (bp) positions of the nuclear recombination activating gene 1 gene (rag1), which has a biparental mode of inheritance, 41-bp substitutions were detected between the two parent species, whereas an electropherogram of the hybrid displayed polymorphic double peaks at all of the base positions, along with one additional one, strongly indicating its hybrid state. Meanwhile, sequence comparison of the mitochondrial cytochrome b gene (mt-cyb) (1,140 bp), which has a maternal mode of inheritance, showed only 5–22-bp differences (97.6–99.5% identities) between the hybrid and Pu. herzi, but as many as 158–168-bp differences (85.2–86.1% identities) between the hybrid and Ps. parva, clearly indicating Pu. herzi as the maternal species. Thus, combined analyses of independent data sets (i.e., morphology and nuclear and mitochondrial DNA sequences) offered convincing evidence for the hybrid state of a naturally occurring hybrid resulting from intergeneric mating between a female Pu. herzi and a male Ps. parva.

Interannual variability of regional evapotranspiration under precipitation extremes: A case study of the Youngsan River basin in Korea

Understanding basin-scale evapotranspiration (ET) is an important issue for the management of regional water resources, especially with the recent trend of intensified precipitation (P). This study assessed the spatial and temporal variations of regional ET in response to P extremes, for various types of land-cover across the Youngsan River basin in Korea.

Assessing optimal set of implemented physical parameterization schemes in a multi-physics land surface model using genetic algorithm

Abstract. Optimization of land surface models has been challenging due to the model complexity and uncertainty. In this study, we performed scheme-based model optimizations by designing a framework for coupling "the micro-genetic algorithm" (micro-GA) and "the Noah land surface model with multiple physics options" (Noah-MP). Micro-GA controls the scheme selections among eight different land surface parameterization categories, each containing 2–4 schemes, in Noah-MP in order to extract the optimal scheme combination that achieves the best skill score. This coupling framework was successfully applied to the optimizations of evapotranspiration and runoff simulations in terms of surface water balance over the Han River basin in Korea, showing outstanding speeds in searching for the optimal scheme combination. Taking advantage of the natural selection mechanism in micro-GA, we explored the model sensitivity to scheme selections and the scheme interrelationship during the micro-GA evolution process. This information is helpful for better understanding physical parameterizations and hence it is expected to be effectively used for further optimizations with uncertain parameters in a specific set of schemes.

Multi‐site calibration using a grid‐based event rainfall–runoff model: a case study of the upstream areas of the Nakdong River basin in Korea

AbstractMost runoff analyses using a grid‐based distributed model use one parameter group calibrated at the outlet of a watershed, instead of dividing the watershed into subwatersheds. Significant differences between the observed value and the simulation result of the subwatersheds can occur if just one parameter group is used in all subwatersheds that have different hydrological characteristics from each other. Therefore, to improve the simulation results of the subwatersheds within a watershed, a model calibrated at every subwatershed needs to be used to reflect the characteristics of each subwatershed. In this study, different parameter groups were set up for one or two sites using a distributed model, the GRM (Grid based Rainfall‐runoff Model), and the evaluations were based on the results of rainfall–runoff analysis, which uses a multi‐site calibration (MSC) technique to calibrate the model at the outlet of each site. The Hyangseok watershed in Naeseong River, which is a tributary of Nakdong River in Korea, was chosen as the study area. The watershed was divided into five subwatersheds each with a subwatershed outlet that was applied to the calibration sites. The MSC was applied for five cases. When a site was added for calibration in a watershed, the runoff simulation showed better results than the calibration of only one site at the most downstream area of the watershed. The MSC approach could improve the simulation results on the calibrated sites and even on the non‐calibrated sites, and the effect of MSC was improved when the calibrated site was closer to the runoff site. Copyright © 2014 John Wiley & Sons, Ltd.