• Title/Summary/Keyword: Nakdong watershed

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Probabilistic assessment of causal relationship between drought and water quality management in the Nakdong River basin using the Bayesian network model (베이지안 네트워크 모형을 이용한 낙동강 유역의 가뭄과 수질관리의 인과관계에 대한 확률론적 평가)

  • Yoo, Jiyoung;Ryu, Jae-Hee;Lee, Joo-Heon;Kim, Tae-Woong
    • Journal of Korea Water Resources Association
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    • v.54 no.10
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    • pp.769-777
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    • 2021
  • This study investigated the change of the achievement rate of the target water quality conditioned on the occurrence of severe drought, to assess the effects of meteorological drought on the water quality management in the Nakdong River basin. Using three drought indices with difference time scales such as 30-, 60-, 90-day, i.e., SPI30, SPI60, SPI90, and three water quality indicators such as biochemical oxygen demand (BOD), total organic carbon (TOC), and total phosphorus (T-P), we first analyzed the relationship between severe drought occurrence water quality change in mid-sized watersheds, and identified the watersheds in which water quality was highly affected by severe drought. The Bayesian network models were constructed for the watersheds to probabilistically assess the relationship between severe drought and water quality management. Among 22 mid-sized watersheds in the Nakdong River basin, four watersheds, such as #2005, #2018, #2021, and #2022, had high environmental vulnerability to severe drought. In addition, severe drought affected spring and fall water quality in the watershed #2021, summer water quality in the #2005, and winter water quality in the #2022. The causal relationship between drought and water quality management is usufaul in proactive drought management.

Hydrogeological Characteristics of Groundwater in Small Watershed of the Nakdong River Basin (낙동강 하류 소유역의 지하수와 하천수의 수리지질학적 특성)

  • Sieun Kim;SeongYeon Jung;MoonSu Kim;Youn-Tae Kim;Yong-Hoon Cha;Chung-Mo Lee
    • Journal of the Korean earth science society
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    • v.45 no.1
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    • pp.72-84
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    • 2024
  • Recently, the vulnerability of water resources has been increasing owing to climate change, highlighting the importance of groundwater. In particular, the Nakdong River Basin, located in the southern part of Korea, experiences frequent water scarcity phenomena, such as droughts. This study analyzed the hydrogeological characteristics of the study area by examining groundwater and stream water in the Gwangrye Stream, downstream of the Nakdong River Basin, in August and October 2023. Therefore, we collected samples from 54 groundwater wells and five streams for water quality analysis. The results of the field tests indicated an increasing trend in electrical conductivity from upstream to downstream in the study area. Laboratory analyses confirmed that the concentration of Na increased from upstream to downstream more than that of Ca. In conclusion, both stream water and groundwater were influenced by anthropogenic contamination. These changes were closely related to land use in the study area. The upstream areas are primarily composed of forests, whereas the downstream areas are composed of industrial complexes, wastewater treatment facilities, and agricultural areas, which are likely to affect both stream water and groundwater.

Geochemistry of Surface Sediments near the Nakdong River Estuary: Chemical Weathering and Source Rock Composition (낙동강 하구 인근 해저 표층 퇴적물의 지화학 조성: 화학적 풍화와 기원지)

  • Young Ji Joo
    • Journal of the Korean earth science society
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    • v.45 no.5
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    • pp.449-455
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    • 2024
  • Characteristics of riverine sediments entering the marine realm reflect the geology, geography, topography, and climate of the drainage basin. Chemical weathering in hinterland is known to play a significant role in regulating atmospheric CO2 levels. This study examines the intensity of chemical weathering and the composition of source rocks of surface sediments near the Nakdong River estuary on the southern coast of the Korean Peninsula. The degree of chemical weathering of the study samples is relatively low to moderate (average Chemical Index of Alteration=68), and the weathering trend inferred in the A-CN-K diagram suggests that the source rock composition is close to the average upper continental crust. It indicate that the source rock composition represents a mixture of the Mesozoic granitoids and the Gyeongsang Supergroup distributed in the Nakdong River drainage basin. The surface sediments exhibit fractionated chondrite-normalized rare eath element patterns and negative Eu anomalies, again similar to the upper continental crust. Comparison of our result with data from global estuarine sediment and large rivers in Korea allow us to parse the potential impacts of geology and topography on chemical weathering in watersheds.

Properties of Water Quality and Land Use at the Rural Area in the Nakdong River Watershed (낙동강수계 농촌유역의 토지이용 및 수질 특성)

  • Kim, Jin-Ho;Kim, Chan-Yong;Lee, Seong-Tae;Choi, Chul-Mann;Jung, Goo-Bok;Lee, Jong-Sik;Kim, Won-Il
    • Korean Journal of Environmental Agriculture
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    • v.26 no.2
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    • pp.99-106
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    • 2007
  • This study was focused on understanding the agricultural non-point sources pollution in 72 rural catchments of Nakdong river watershed from 2001 to 2005 every two year. Also. Pearson correlations between water quality and basin characteristic were computed. Water quality of this study watershed was better in 2003 than any other period. The water quality of upstream was recorded from 0.040 to 0.510 dS/m in EC, from 3.55 to 22.60 mg/L in DO, from 0.32 to 16.64 mg/L in T-N, from 0.00 to 12.21 mg/L in $NO_3-N$, from 0.000 to 0.860 mg/L in T-P, and from 0.000 to 0.640 mg/L in $PO_4-P$. A the downstream, EC was measured from 0.030 to 0.520 dS/m, DO from 4.13 to 18.36 mg/L, T-N from 0.38 to 26.88 mg/L, $NO_3-N$ from 0.10 to 20.12 mg/L, T-P from 0.002 to 0.820 mg/L, $PO_4-P$ from 0.002 to 0.690 mg/L. But there was no difference between upstream and downstream for the water quality. Based on the correlation analysis between water quality and land use, correlation between BOD and residential was the highest positive correlation of 0.541 (p<0.01), and correlation between $PO_4-P$ and forest was the highest negative correlation of -0.451 (p<0.01). Also, T-N, $NO_3-N$, and pH were not correlated with all basin characteristics and basin was not correlated with all water quality parameter. According to the correlation residential was causative of growing worst for water quality, and forest was causative of improving for water quality.

Estimation of Flood Risk Index for the Nakdong River Watershed (낙동강 유역의 홍수위험지수 산정)

  • Song, Jae Ha;Kim, Sangdan;Park, Moo Jong;Choi, Hyun Il
    • Journal of Korea Water Resources Association
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    • v.46 no.1
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    • pp.35-45
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    • 2013
  • The aim of study is to present how to estimate and use the FRI (Flood Risk Index) for classifying area zones based on regional flooding risk in terms of the integrated flood risk management. To estimate the FRI at a spatial resolution of city/county/town units for the Nakdong River Watershed, the 17 representative flood indexing factors are carefully selected for the three flood indexes, such as PI (Pressure Index), SI (State Index), and RI (Response Index) under the P-S-R (Pressure-State-Response) classification system. Because flood indexing factors are measured at different scales and units, they are transformed into a common domain by the T-Score normalization technique. The entropy weight coefficient method is also applied to calculate the weight of flood indexing factors in order to reduce subjective judgement on the effect of weight coefficients. The three flood indexes of PI, SI, and RI are integrated for an overall value of the FRI to evaluate the flood risk of districts. To examine the practical application of the proposed FRI, the FRI results with/without the weight coefficients are compared with flooding zones of natural disaster risk areas officially announced in 2010. It is expected that the FRI ensured by full verification can make regional protection plans against flooding disasters with respect to causes and characteristics of past floods.

Water Quality Analysis of In-stream and Reservoir Water in Erosion Control Dams in the Nakdong River Basin (낙동강유역 불투과형 사방댐의 계류수 및 저류수 수질 특성 분석)

  • Li, Qiwen;Eu, Song;Lee, Eun Jai;Lee, Ye Eun;Kim, Min Sik;Im, Sang Jun
    • Journal of Korean Society of Forest Science
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    • v.108 no.3
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    • pp.329-340
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    • 2019
  • Water pollution in erosion control dams is a major issue for forest watershed management, but the effects of erosion control dams on water quality remain poorly understood. In this study, water quality data from streams and dam reservoirs were collected over the Nakdong river basin. Monitored data were further analyzed to examine the relationship between watershed characteristics and water quality. Of the total 43 erosion control dams, less than 10% had lower water quality that was not suitable for agricultural use. TOC and oxygen demand, SS and turbidity, SS and Chl-a, and Chl-a and turbidity showed high correlations (p < 0.01) both in stream water and in detained water. BOD and SS, BOD and Chl-a, BOD and turbidity, and TOC and Chl-a showed high correlations only in stream water. Overall, the results demonstrated that for most erosion control dams the water quality was relatively good. In addition, the quality of downstream water is somewhat affected by the water detained by erosion control dams, in limited ways.

Evaluation of Non-point source Vulnerable Areas In West Nakdong River Watershed Using TOPSIS (TOPSIS를 이용한 서낙동강 유역 비점오염 취약지역 평가 연구)

  • KAL, Byung-Seok;PARK, Jae-Beom;KIM, Ye-Jin
    • Journal of the Korean Association of Geographic Information Studies
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    • v.24 no.1
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    • pp.26-39
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    • 2021
  • This study investigated the characteristics of the watershed and pollutants in the Seonakdong River basin in the lower stream of the Nakdong River Water System, and evaluated the areas vulnerable to nonpoint pollution by subwatershed according to the TOPSIS(Technique for Order of Preference by Similarity to Ideal Solution) method. The selection method consists of selection of evaluation factors, calculation of weights and selection of areas vulnerable to non-point pollution through evaluation factors and weights. The entropy method was used as the weight calculation method and TOPSIS, a multi-criteria decision making(MCDM) method was used as the evaluation method. Indicator data were collected as of 2018, and national pollution source survey data and national statistics were used. Most of the vulnerable watersheds were highly urbanized had a large number of residents and were evaluated as having a large land area among industrial facilities and site area rate. Through this study, it is necessary to approach a variety of weighting methodologies to assess the vulnerability of non-point pollution with high reliability, and scientific analysis of the factors that affect non-point pollution sources and consideration of the effects are necessary.

Assessment of hydrological drought risk in the southern region in 2022: based on bivariate regional drought frequency analysis (2022년 남부지역 수문학적 가뭄위험도 평가: 수문학적 이변량 가뭄 지역빈도해석 중심으로)

  • Kim, Yun-Sung;Jung, Min-Kyu;Kim, Tae-Woong;Jeong, Seung-Myeong;Kwon, Hyun-Han
    • Journal of Korea Water Resources Association
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    • v.56 no.2
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    • pp.151-163
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    • 2023
  • This study explored the 2022 drought over the Nakdong River watershed. Here, we developed a bivariate regional frequency analysis method to evaluate the risk of hydrological drought. Currently, natural streamflow data are generally limited to accurately estimating the drought frequency. Under this circumstance, the existing at site frequency analysis can be problematic in estimating the drought risk. On the other hand, a regional frequency analysis could provide a more reliable estimation of the joint return periods of drought variables by pooling available streamflow data over the entire watershed. More specifically, the Copula-based regional frequency analysis model was proposed to effectively take into account the tail dependencies between drought variables. The results confirmed that the regional frequency analysis model showed better performance in model fit by comparing the goodness-of-fit measures with the at-site frequency analysis model. We find that the estimated joint return period of the 2022 drought in the Nakdong River basin is about eight years. In the case of the Nam river Dam, the joint return period was approximately 20 years, which can be regarded as a relatively severe drought over the last three decades.

Assessment of the Non-point Source Pollution Control Strategies for Water Quality Improvement in the Haeban Stream of West Nakdong River Watershed (서낙동강 유역 해반천의 수질 개선을 위한 비점오염관리대책 효과 분석)

  • Yejin Kim
    • Journal of Wetlands Research
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    • v.26 no.1
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    • pp.1-9
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    • 2024
  • In this study, a HSPF model was developed to simulate runoff and water quality in the Haebancheon watershed, which has a high land area ratio and population density among the West Nakdong River watersheds. Various non-point source pollution control strategies were applied, and the reduction in pollutant loads and the exceedance rate of water quality standards were analyzed. The scenarios included basic road cleaning for reducing pollutant loads, runoff reduction measures considering extensive low-impact development techniques, and inflow reduction measures to mitigate non-point source pollution entering the river. In the first step, practical conditions such as the number of vehicles for road cleaning in Kimhae City were considered, while for the second and third steps, it was assumed that 50% of the applicable land use area was used to be applicable for the LID techniques. As a result of applying all three measures, it was analyzed that the BOD pollutant load could be reduced by 58.28%, T-N by 58.49%, and T-P by 51.56%. Furthermore, the 60th percentile of water quality measurements accumulated over 5 years was set as the target water quality, and a flow-duration curve was constructed. The exceedance rate of the flow-duration curve before and after applying non-point source pollution reduction measures was analyzed. As a result, for BOD, the exceedance rate decreased from 41.57% before applying the measures to 16.32% after, showing a 25.25% reduction in the exceedance rate. For T-N, the exceedance rate decreased significantly from 40.31% before the measures to 22.84% after, and for T-P, it decreased significantly from 62.43% to 27.22%.

Assessment of Hydrochemistry and Irrigation Water Quality of Wicheon Watershed in the Gyeongsangbuk-do (경상북도 위천수계의 수리화학적 특성 및 관개용수 수질평가)

  • Lee, Gi-Chang;Park, Moung-Sub;Kim, Jae-Sik;Jang, Tae-Kwon;Kim, Hyo-Sun;Lee, Hwa-Sung;Son, Jin-Chang
    • Korean Journal of Environmental Agriculture
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    • v.39 no.1
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    • pp.36-43
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    • 2020
  • BACKGROUND: Wicheon watershed has the largest irrigation area among the mid-watershed of Nakdong river. However, no investigation of irrigation water quality has been conducted on the Wicheon watershed, which evaluates the effects on the soil quality and crop cultivation. Therefore, this study aims to provide various assessments of water quality of Wicheon watershed as the scientific basic data for efficient agricultural activities. METHODS AND RESULTS: Water sampling was performed in five locations of the first tributaries of Wicheon. Wicheon watershed showed clean water quality with very low organic matters and safe water quality from metals at all points of investigation. It was estimated that the natural chemical components of Wicheon watershed were originated from water-rock interaction in Gibbs diagram. All samples were concentrated in the type of Ca-HCO3-Cl in the Piper diagram. The quality of irrigation water was evaluated with sodium adsorption ratio (SAR), residual sodium carbonate (RSC), permeability index (PI), and percent sodium (%Na). The values of these water quality indices were in the range of 0.37-0.67, -2.11--0.24, 41.13-84.52% and 11.28-21.84%, respectively, and were classified as good grades at all sites. CONCLUSION: The water quality of Wicheon watershed was very low in salt, indicating good irrigation water suitable for growing agricultural products. We hope that the results of this study will be used as the basic data for the cultivation of agricultural products and promotion of their excellence.