Geum River Research Articles

Raineyella fluvialis sp. nov., an actinobacterium isolated from freshwater sediment.

A novel, facultatively anaerobic actinobacterium, designated strain CBA3103T, was isolated from sediment of the Geum River in South Korea. Phylogenetic analysis indicated that strain CBA3103T is most closely related to Raineyella antarctica LZ-22T (98.47 % 16S rRNA gene sequence similarity). The genome of strain CBA3103T was 3 649 865 bp with a DNA G+C content of 69.6 mol%. The average nucleotide identity value between strain CBA3103T and R. antarctica LZ-22T was 79.22 %. Cells of strain CBA3103T were Gram-positive, rod-shaped, 0.6-0.9 µm wide and 1.4-2.4 µm long. Growth occurred at 15-40 °C (optimum, 35 °C), at pH 6.0-7.0 (optimum, pH 7.0) and with 0-2 % NaCl (w/v) (optimum, 0-1 %, w/v). The major cellular fatty acids in strain CBA3103T were anteiso-C15 : 0, anteiso-C15 : 1 A and iso-C14 : 0. The major respiratory quinone was menaquinone-9(H4). The polar lipids of strain CBA3103T were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, five unidentified glycolipids and three unidentified phospholipids. Based on the genotypic, phenotypic and chemotaxonomic analyses, strain CBA3103T represents a novel species of the genus Raineyella, for which the name Raineyella fluvialis sp. nov. (type strain CBA3103T=KACC 21446T=DSM 110288T) is proposed.

Towards a soil moisture drought monitoring system for South Korea

The Korea Land Data Assimilation System (KLDAS) has been established for agricultural drought (i.e. soil moisture deficit) monitoring in South Korea, running the Noah-MP land surface model within the NASA Land Information System (LIS) framework with the added value of local precipitation forcing dataset and soil texture maps. KLDAS soil moisture is benchmarked against three global products: the Global Land Data Assimilation System (GLDAS), the Famine Early Warning Systems Network (FEWS NET) Land Data Assimilation System (FLDAS), and the European Space Agency Climate Change Initiative (ESA CCI) satellite product. The evaluation is performed using in situ measurements for 2013–2015 and one month standardized precipitation index (SPI-1) for 1982–2016, focusing on four major river basins in South Korea. The KLDAS outperforms all benchmark products in capturing soil moisture states and variability at a basin scale. Compared to GLDAS and FLDAS products, the EAS CCI product is not feasible for long term agricultural monitoring due to lower data quality for early periods (1979–1991) of soil moisture estimates. KLDAS shows that the most recent 2015 drought event leads to highest drought areas in the Han and Geum River basins in the past 35 years. This work supports KLDAS as an effective agricultural drought monitoring system to provide continuous regional high-resolution soil moisture estimates in South Korea.

Effect of Microhabitat Structure on the Distribution of an Endangered Fish, Coreoperca kawamebari (Temminck & Schlegel, 1843) in the Geum River, South Korea

Macrophytes play a major role in the structuring of aquatic environments and may influence the distribution and feeding habits of fish species. We explored the microhabitat characteristics influencing the spatial distribution of newly discovered Coreoperca kawamebari (Temminck & Schlegel, 1843) in the upstream reaches of the Geum River. Out of 21 study sites, C. kawamebari was found in 10 sites, and its abundance was strongly positively correlated with “vegetated” microhabitats, especially those covered by elodeids (e.g., Ceratophyllum demersum). The utilization of elodeids by the piscivores fish, C. kawamebari, may limit the abundance of other native fishes, and stable isotope analysis also showed that C. kawamebari is likely to consume other fish species. However, the influence of other fish species on C. kawamebari is assumed to be small, considering that C. kawamebari is a latent predator. Although the abundance of other fish was low within the preferred microhabitat of C. kawamebari, other species were abundant in each site where C. kawamebari was dominant. From this finding, we conclude that the successful settlement of C. kawamebari in the upper section of the Geum River can be attributed to their habitat preferences. Although the elodeids favored by C. kawamebari generally have difficulty developing in the upstream section, the habitat creation by humans has contributed to the stable settlement of new fish species.

<p><strong>Morphology and molecular description of <em>Wilmottia koreana</em> <em>sp. nov.</em> (Oscillatoriales, Cyanobacteria) isolated from the Republic of Korea</strong></p>

Two types of Wilmottia (Cyanobacteria) were collected from the tree-bark of a tree on Mt. Gwanggyo in Suwon City, Gyeonggi-do and a rock wall of Haje Port, Geum River in Jeollabuk-do, Republic of Korea. Morphological observations using light microscopy (LM) and transmission electron microscopy (TEM) revealed that one species was Wilmottia murrayi (Coleofasciculaceae, Oscillatoriales) and the other had similar morphology to W. murrayi, with considerable genetic variations, and thus, it was described as a new species named Wilmottia koreana. Phylogenetic analyses of the 16S rRNA revealed that the family Coleofasciculaceae was clearly separated into taxonomic groups of each genus, and in them, Wilmottia forms a monophyletic lineage. W. koreana diverged the earliest, forming a unique clade separate from the others. Statistical analyses showed that the inter-species genetic distances of Wilmottia were significantly different from the intra-species distances (t-test, P < 0.001). Additionally, the secondary structures of D1–D1’, Box-B, and the V3 helices were different among the Wilmottia species. These results demonstrated that the proposed new Wilmottia species was unique in molecular traits. Therefore, we propose this to be a new species belonging to the genus Wilmottia with the name Wilmottia koreana sp. nov.

Effects of Inter-Basin Water Transfer Project Operation for Emergency Water Supply

In South Korea, rainfall deficits lasting for three years (2014–2017), have decreased the reservoir storage level. The Boryeong reservoir, located in the Geum River western sea basin, recorded the lowest reservoir storage. The Boryeong water transfer project has supplied water resources to the east side of the basin. This is an emergency water supply project operated when there is a water supply shortage in the reservoir. It is essential to use appropriate settings for the operation scheme. In this study, a reservoir simulation model was built by applying a water supply adjustment standard, which reduces the water supply when reservoir storage is decreased to a specific level. Four operation cases (no operation, continuous operation, and two temporary operations) were used to analyze the effects of the project. The temporary operations activate when the reservoir storage decreases. The volumetric reliability of the water supply is enhanced by 1.8–2.2% in the temporary operation cases. This study used cost-benefit analysis to analyze the two temporary operation cases. Operating the transfer project when reservoir storage goes below a certain level is more efficient than other cases.

Large weir construction causes the loss of seasonal habitat in riverine wetlands: a case study of the Four Large River Projects in South Korea

From 2009 to 2012, South Korea carried out national-wide construction projects in four rivers; sixteen large-weirs were constructed to control flood risk and to secure water resources. Environmental impact assessment of the weir construction evaluated conditional changes by comparing post-survey records with pre-construction periods. However, the ecological assessment for the weir construction in a long-term perspective has been still limited. In this study, we compared the long-term dynamics of riverine habitat in two construction sites (Nakdong River and Geum River), and one reference site (Seomjin River) in South Korea using 33-years database of satellite imagery. We classified 30 m-grid riverine habitats into three temporal types (i.e., permanent water, seasonal water, and non-flooded habitat) based on annual flooding frequency and its temporal trend was compared. After weirs construction, the area of permanent water was increased (Nakdong R.: +36.0%, Geum R.: +10.9%); seasonal habitat and non-flooded habitat were decreased (Nakdong R: −36.5% and −37.4%; Geum R: −22.9% and −28.2%, respectively). And annual flux of habitat transitions into different habitat types has been decreased only in weir construction sites. Among different habitat transition categories, habitat change into permanent water was the highest during the weir construction periods. Our long-term analysis of riverine habitat can be used to understand temporal changes and recovery after weir construction and channel dredging.

Identification and enumeration of cyanobacteria species using a deep neural network

Cell classification and cell counting are essential for the detection, monitoring, forecasting, and management of harmful algae populations. Conventional methods of algae classification and cell counting are known to be time-consuming, labor-intensive, and subjective, depending on the expertise of the observers. The objectives of this study were to classify and quantify five cyanobacteria using the deep learning techniques of a fast regional convolutional neural network (R-CNN) and convolutional neural network (CNN). Water samples taken from the Haman weir of Nakdong River and Baekje weir of the Geum River were observed under the optical microscope. The images captured by the microscope were used to classify cyanobacteria species using the fast R-CNN model. Post-processing of the classified images generated by the model reduced the noises of the cell features, thereby improving the accuracy of the CNN model in quantifying cyanobacteria cells. The distinctive morphological features of the five species were extracted by the fast R-CNN model. This model was able to achieve a reasonable agreement with the manual classification results, yielding average precision (AP) values of 0.929, 0.973, 0.829, 0.890, and 0.890 for Microcystis aeruginosa, Microcystis wesenbergii, Dolichospermum, Oscillatoria, and Aphanizomenon, respectively. The CNN model for the Microcystis species obtained an R2 value of 0.775 and RMSE value of 26 cells for training, and an R2 of 0.854 and RMSE of 23 cells for validation. A minor underestimation and overestimation for a population with <50 cells and >250 cells were observed, respectively, which are due to the overlapping of cells and the presence of blurry regions in the input images. In conclusion, this study was able to demonstrate the reliable performance of cyanobacteria classification and cell counting using deep learning approaches.

금강 하구역의 춘계와 하계에 어류플랑크톤 종조성과 출현량

Ichthyol-plankton and the environment data were collected in Geum River Estuary in spring and summer of 2016~2018. These data were collected though “National Survey of Marine Ecosystem” project. Geum River Estuary is one of the main estuaries in the West Sea of Korea. A total of 18 taxa of fish larvae were collected. Eight taxa were collected in spring, and the mean abundance was 242 ind./1,000m3. Thirteen taxa were collected during the summer, and the mean abundances was 109 ind./1,000m3. During this study, most dominant species was Gobiidae spp. (49.4%), which was followed by whiting, Sillago japonica (37.3%). Yearly species composition showed Gobiidae spp. was most dominant specie except in 2018. In 2018, Sillago japonica was dominant in spring and anchovy (Engraulis japonicus) was dominant in summer. When abnormal high water temperature period (>28℃) occurred, Gobiidae spp. was not dominant.

Uncertainty decomposition in climate-change impact assessments: a Bayesian perspective

A climate-impact projection usually consists of several stages, and the uncertainty of the projection is known to be quite large. It is necessary to assess how much each stage contributed to the uncertainty. We call an uncertainty quantification method in which relative contribution of each stage can be evaluated as uncertainty decomposition. We propose a new Bayesian model for uncertainty decomposition in climate change impact assessments. The proposed Bayesian model can incorporate uncertainty of natural variability and utilize data in control period. We provide a simple and efficient Gibbs sampling algorithm using the auxiliary variable technique. We compare the proposed method with other existing uncertainty decomposition methods by analyzing streamflow data for Yongdam Dam basin located at Geum River in South Korea.

Dynamical analysis of the mud-belt formation in the Bohai, Yellow and East China seas

Mud belts commonly occur on the coast and shelf environments worldwide. It requires a point source (river) and a residual current, all together constituting a tripartite configuration of the mud-belt system. This mud-belt system is analyzed for its basic sedimentological and hydrodynamical parameters to be interrelated under the steady-state conditions. The parameters include the length (L) and sedimentation rate (A) of a mud belt, water depth (h), residual current velocity (ur), and settling velocity of suspended particles (ws). The analysis shows that L is proportional to h, ur and ln A but inversely proportional tows. In addition, the mean sedimentation rate of a mud belt (A¯) is a function of only the sedimentation rates at its head and toe.To test the analytical relationships, three mud belts studied extensively are chosen from the Bohai, Yellow and East China seas. Each of these mud belts follows the ideal tripartite configuration. For all the mud belts, residual currents have been reported to be the strongest during winter seasons. The calculated A¯ gives a constraint to the otherwise wide range of the previously estimated riverine contributions to each mud belt. The two mud belts in the East China Sea and the Bohai Sea are analyzed to receive 30 and 7% of riverine sediment discharges from the Yangtze and Yellow rivers, respectively. In comparison, the Huksan Mud Belt in the southeastern Yellow Sea, on debate concerning its origin, analytically proves to be in a source-sink relationship with the Geum River. The calculated ws suggests that suspended particles are composed dominantly of fine-silt-sized single grains or micro-flocs for the three mud belts. As a result, the derived relationships may be a useful tool to understand dynamical processes of the mud belt. They also may be instrumental in anticipating the possible changes in the mud-belt evolution with A and ur that are likely to vary with the globally warming climate.

Landscapes shared by visibility: a case study on the settlement relationships of the Songgukri culture, Korea

The Songgukri culture (c. 2900–2400 cal. BP) in the Geum River basin is often regarded as one of the earliest complex societies in the Korean peninsula, based on some evidence for an intensified agrarian economy and social differentiation. This study focuses on landscape visibility as a method of detecting settlement relationships of the Songgukri culture. Two measures of landscape visibility, viewshed size and shared-ness of viewshed (SoV), are examined in this study. Our results indicate that while Songgukri centers tend to have larger visibility of landscape than non-centers, both centers and non-centers share their visible landscape with other settlements at a remarkably high rate. We argue that landscape visibility at Songgukri settlements reflects a shared sense of cultural belonging among settlers, rather than sociopolitical inequality between the elites in centers and the non-elites in other settlements. This study highlights a long-term process, in which bottom-up cultural interactions of Songgukri residents may have contributed to the development of settlement organization and regional communal identities over time.

Evaluation of physico-chemical parameters regulating zooplankton community structure in the Geum River, Korea

The aim of the present study was to examine the dynamics of zooplankton community structure in the midstream of the Geum River, South Korea. The sampling was performed bi-monthly at five stations. During the study period, the most dominant taxa was Rotifera, comprising 73.3% of the total abundance, followed by Protozoa (17.3%), Cladocera (5.4%), and Copepoda (4.0%). The correlation coefficients between selected physico-chemical parameters and zooplankton abundance showed that the generation of zooplankton in the study area was highly correlated with water temperature (WT), chlorophyll a concentration, and pH values. As the river flows downstream (from GC and MC stations to SW, GW, and BW stations), zooplankton abundance was augmented, influenced by the levels of total phosphorus (TP), and total nitrogen (TN), while total organic carbon (TOC) decreased, and pH values increased. Furthermore, the values of WT, TN, TP, and TOC were higher and zooplankton abundance was lower at the GC station than at other stations. The results suggested that the dynamics of zooplankton community in the midstream of the Geum River was influenced not only by physico-chemical factors but also by the inflow from the upper streams.

Stream health assessment using chemical and biological multi-metric models and their relationships with fish trophic and tolerance indicators

Abstract Nonsan Stream is a tributary of the Geum River that is strongly affected by urbanization and agricultural activities in the watershed. The present study was performed to diagnose the chemical and biological health of the stream from 2010 to 2016 using the multi-metric water pollution index (WPI) and index of biotic integrity (IBI) models. Monthly and annual variations in stream water chemistry were directly influenced by the monsoon season. Inputs of total phosphorus, suspended solids, and ionic substances, as well as dilution of total nitrogen, occurred during July and August. Chlorophyll increase was largely influenced by total phosphorus (R2 = 0.43, p

Bayesian uncertainty decomposition for hydrological projections

There is a considerable uncertainty in a hydrological projection, which arisen from the multiple stages composing the hydrological projection. Uncertainty decomposition analysis evaluates contribution of each stage to the total uncertainty in the hydrological projection. Some uncertainty decomposition methods have been proposed, but they still have some limitations: (1) they do not consider nonstationarity in data and (2) they only use summary statistics of the projected data instead of the full time-series and lack a principled way to choose the summary statistic. We propose a novel Bayesian uncertainty decomposition method which can alleviate such problems. In addition, the proposed method provides probabilistic statements about the uncertainties. We apply the proposed method to the streamflow projection data for Yongdam Dam basin located at Geum River in South Korea.

A report of 37 unrecorded anaerobic bacterial species isolated from the Geum River in South Korea

A report of 37 unrecorded anaerobic bacterial species isolated from the Geum River in South Korea

Predicting the effect of impervious area change on water circulation rate in the Geum River watershed using HSPF modeling

Predicting the effect of impervious area change on water circulation rate in the Geum River watershed using HSPF modeling

Coupled annual and daily multivariate and multisite stochastic weather generator to preserve low- and high-frequency variability to assess climate vulnerability

Multivariate and multisite stochastic weather generators have been proposed to produce an ensemble of climate time series but are often limited to preserving low-frequency variability of climate variables as well as producing extreme rainfall events. This study presents a new, two-stage, multivariate, multisite weather generator by coupling annual and daily weather generators. A daily weather generator is first developed using heavy tailed distribution, spatial tail dependence, and multivariate autoregressive models. For the second stage, annual climate variables over the region are modeled using a wavelet decomposition approach coupled with a multivariate autoregressive model. The generated annual time series are used to reconstruct daily simulations to embed multiple low-frequency oscillations in a daily time series. The proposed weather generator is applied to the Geum River Basin in South Korea, and its performance is compared to that of a nested simplified model. Results show that the proposed model performs well with respect to reproducing marginal distributional attributes, multisite dependencies, and climate variability at the daily and annual scales. Lastly, the weather generator adopts a quantile mapping procedure to incorporate long-term distributional changes into generated climate sequences for use in climate change assessments. Results show that inter-annual variability is also well preserved while climate sequences are adjusted by various alterations.

Evaluation of Habitat Range and Physical Habitat of Black Shinner (Pseudopungtungia nigra) from Yongdam to Daecheong Dam in Geum River

Evaluation of Habitat Range and Physical Habitat of Black Shinner (Pseudopungtungia nigra) from Yongdam to Daecheong Dam in Geum River

Temporal Adjustment of Channel Geometry and Spatial Changes in Riverbed Materials along the Downstream Channels of Large Dams in the Geum River basin

Temporal Adjustment of Channel Geometry and Spatial Changes in Riverbed Materials along the Downstream Channels of Large Dams in the Geum River basin

Population response modeling and habitat suitability of Cobitis choii fish species in South Korea for climate change adaptation

Endangered species ecosystems require appropriate monitoring for assessing population growth related to the emerging pollutants in their habitat conditions. The response of population growth of Cobitis choii, an endangered fish species, under the exposure to emerging pollutants present in the Geum River Basin of South Korea was studied. Toxicity models of concentration addition (CA), independent action (IA), and concentration addition-independent action (CAIA) were implemented utilizing the concentration of a set of 25 chemicals recorded in the study area. Thus, a population-level response analysis was developed based on the abundance of Cobitis choii for period 2011-2015. The results were compared showing that the CA and IA models were the most conservative approaches for the prediction of growth rate. Further, a standard abnormality index (SAI) and habitat suitability (HS) indicators based on the climate, habitat, and abundance data were presented to completely analyze the population growth of the species. Suitability of the species growth was most probable for year 2015 for the variables of air temperature and land surface temperature. A spatial analysis was complementarily presented to visualize the correlation of variables for the best suitability of the species growth. This study presents a methodology for the analysis of the ecosystem's suitability for Cobitis choii growth and its assessment of the chemicals present in Geum River stream.