• Journal of Korea Water Resources Association
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• v.56 no.11
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• pp.823-835
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• 2023

Recently, due to the increase in abnormal climate, rainfall intensity is increasing and drought periods are continuing. These environmental changes lead to prolonged drought conditions and difficulties in real-time recognition. In general, drought can be judged by the amount of precipitation and the number of days without rainfall. In determining the impact of drought, it is divided into meteorological drought, agricultural drought, and hydrological drought and evaluation is made using the drought index, but environmental drought evaluation is insufficient. The river water quality managed through the total water pollution cap system is vulnerable to the effects of such drought. In this study, we aim to determine the drought impact on river water quality and quantify the impact of prolonged drought on water quality. The impact of rain-free days and accumulated precipitation on river water quality was quantitatively evaluated. The Load Duration Curve (LDC), which is used to evaluate the water quality of rivers, was used to evaluate water pollution occurring at specific times. It has been observed that when the number of consecutive rainless days exceeds 14 days, the target water quality in the mid-basin is exceeded in over 60% of cases. The cumulative rainfall is set at 28 days as the criteria, with an annual average rainfall of 3%, which is 32.1 mm or less. It has been noted that changes in water quality in rivers occur when there are 14 or more rainless days and the cumulative rainfall over 28 days is 32.1 mm or less in the Gamcheon Mid-basin. Based on the results of this study, it aims to quantify the drought impact and contribute to the development of a drought water quality index for future environmental droughts.

• Journal of Korean Society of Rural Planning
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• v.2 no.2
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• pp.109-117
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• 1996

The purpose of this study Is to develop water quality management system fort a farm village stream. The framework design of the system and the ecological monitoring of a test watershed were carried out, The system consists of GIS(Geographic Information System ), database, pollution source management, water quality and hydrologic analysis. Suri watershed located on Idong, Yongin city, Kyunggi Province, was selected as the test watershed for the application of the system. The fifteen's monitoring stations were chooses at up- and down-stream of the watershed. The results of an aquatic ecological monitoring were analyzed by the GPI(Group Pollution Index) method. The GPI revealed that water quality was varied within the stream. GPI and DO map for the watershed stream were developed, These maps facilitated to analyze the spatial distribution of the water quality.

• Korean Journal of Ecology and Environment
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• v.52 no.1
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• pp.1-8
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• 2019

River water quality and organisms have a very close relationship with the human living environment and health, so it is very important to ensure and maintain the ecological integrity of the aquatic ecosystem. In that sense, benthic diatoms have relatively little mobility, can explain the effects of long-term exposed pollution sources, and are very suitable indicator organisms for river ecosystem evaluation. Diatom ecologists have been developed various diatom indices to assess water quality and stream ecosystem over the world. However, they so far have insufficient identification of taxa, are strongly regional, and are difficult to apply as they are domestically. Unfortunately, there has not been developed an independent diatom index suitable for the Korean stream. Therefore, management of water quality and aquatic ecosystem suitable for domestic rivers can be made, and development or improvement of comprehensive multivariate diatom index for the integrated assessment of water quality and aquatic ecosystem is urgently needed.

• Journal of Korean Society on Water Environment
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• v.35 no.4
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• pp.340-351
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• 2019

In this study, the relationship between trophic state indices was analyzed based on the monthly or weekly water quality data of 81 lakes (mostly man-made) in Korea between 2013-2017. Carlson's $TSI_C$ and Aizaki's $TSI_m$ were calculated using the summer (Jun.-Sep.) average data at the upper water layer. The previous Korean trophic state index ($TSI_{KO}$) and the newly suggested index ($TSI_{KON}$) was calculated using the annual average data at the whole layer and at the upper layer, respectively. While previous trophic state index (TSI) such as Carlson's TSI included logarithmic function, we devised newly Monod-type $TSI_{KON}$(Chl) that is 50 when half-saturation concentration of chlorophyll ${\alpha}$ ($Chl.{\alpha}$) measured by UNESCO-method is $10{\mu}gL^{-1}$. MMF-type $TSI_{KON}$(TP) was derived based on the relationship between TP and $Chl.{\alpha}$. A comprehensive $TSI_{KON}$ was decided as the larger one of the two $TSI_{KON}$ values. The range of previous TSI was usually 40-50 for the mesotrophic state, which seemed narrow to discriminate trophic characteristics of the class. The upper limits of $TSI_{KON}$ for oligotrophic, mesotrophic, and eutrophic state were set to 23, 50 and 75, respectively. Classification by $TSI_C$ and $TSI_m$ showed higher frequency of eutrophic class compared to $TSI_{KO}$ and $TSI_{KON}$. This means that the estimation by TSIs developed in foreign natural lakes can lead to distorted results in the classification of the trophic state of Korean lakes. This is due to the decrease of transparency by non-algal material and the reduction in phosphorus availability to algal growth, particularly in Monsoon period.

• Geomechanics and Engineering
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• v.30 no.6
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• pp.503-515
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• 2022

The permeability coefficient is an essential parameter for the study of seepage flow in fractured rock mass. This paper discusses the feasibility and application value of using readily available RQD (rock quality index) data to estimate mine water inflow and grouting quantity. Firstly, the influence of different fracture frequencies on permeability in a unit area was explored by combining numerical simulation and experiment, and the relationship between fracture frequencies and pressure and flow velocity at the monitoring point in fractured rock mass was obtained. Then, the stochastic function generation program was used to establish the flow analysis model in fractured rock mass to explore the relationship between flow velocity, pressure and analyze the universal law between fracture frequency and permeability. The concepts of fracture width and connectivity are introduced to modify the permeability calculation formula and grouting formula. Finally, based on the on-site grouting water control example, the rock mass quality index is used to estimate the mine water inflow and the grouting quantity. The results show that it is feasible to estimate the fracture frequency and then calculate the permeability coefficient by RQD. The relationship between fracture frequency and RQD is in accordance with exponential function, and the relationship between structure surface frequency and permeability is also in accordance with exponential function. The calculation results are in good agreement with the field monitoring results, which verifies the rationality of the calculation method. The relationship between the rock mass RQD index and the rock mass permeability established in this paper can be used to invert the mechanical parameters of the rock mass or to judge the permeability and safety of the rock mass by using the mechanical parameters of the rock mass, which is of great significance to the prediction of mine water inflow and the safety evaluation of water inrush disaster management.

• Journal of environmental and Sanitary engineering
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• v.19 no.2
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• pp.45-50
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• 2004

To investigate the epilithic diatom community and water quality of the Osan stream, water samples were collected from the eight stations from April to September 2003. Sampling was two times before and after heavy rain. Total 52 diatom were identified and divided into 12 saproxenosus taxa, 6 saprophilous taxa and 34 indifferent taxa, respectively. The DAIpo values higher after heavy rain than before that. According to tolerance degree to the organic water pollution, all sampling stations ranged from $\alpha$-oligosaprobic to $\alpha$-mesosaprobic. Thus, the result indicates that the water quality of Osan stream is gradually improved by heavy rain.

• Korean Journal of Ecology and Environment
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• v.42 no.3
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• pp.303-316
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• 2009

Benthic macroinvertebrate communities collected from eight different streams in South Korea were analyzed to compare community and biological indices across different levels of water pollution. The Self-Organizing Map (SOM) was utilized to provide overview on association of the proposed indices. The sample sites were accordingly clustered according to the gradient of pollution on the SOM. While the general trends of the indices were commonly observable according to different levels of pollution, the detailed differences among the indices were also illustrated on the SOM. The conventional diversity and evenness indices tended to be high even though the water quality state was poor representing relatively weak gradient at polluted sites, while the index presenting the saprobic degree such as family biotic index showed the stronger gradient at the polluted area and was robust to present the gradient. Our results also confirmed the general characterization of two indices: The Shannon index is more strengthened by the number of species occurring at the sample sites, while the Simpson index is more influenced by the degree of evenness among the species. The patterning based on the SOM was efficient in comparatively characterizing the proposed indices to present ecological states and water quality.

• Journal of Environmental Impact Assessment
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• v.30 no.6
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• pp.355-360
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• 2021

As the domestic water management policy shifted from concentration-oriented water management to load management-centered Total Maximum Daily Load (TMDL), water quality and aquatic ecosystems brought changed. However, it was difficult to determine whether the water quality and the health of the aquatic ecosystem improved after the implementation of the TMDL due to changes in pollutant sources and discharge fluctuations ect, so the effect was analyzed using a log-linear model and biological indicators (Benthic Macroinvertebrates). As a result, BOD and T-P concentrations in the Jinwi River Watershed were reduced by 30% and 35%, showed the effect of improving water quality, however the benthic macroinvertebrates index (BMI) downgraded from grade D to grade E. Therefore, efforts to cultivate ecologicalrivers are necessary to upgrade the health of the aquatic ecosystem in the river watershed.

• Journal of Environmental Health Sciences
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• v.33 no.6
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• pp.517-521
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• 2007

To assess possible risks from the consumption of drinking water from various sources, a survey of the microbiological quality of tap water, commercial bottled drinking water which is exploited from natural mineral water, and natural spring water was conducted. A total of 4 different brands of commercial bottled drinking water, and 4 types of spring water from different sources, and tap water from 4 private houses were tested for four index microorganisms, and the microbial quality changes of the water during the storage at room temperature or refrigerated temperature for 7 days. Aerobic plate counts of all of the initial water samples were still within 100 CFU/ml (drinking water standard of Korea). Total coliforms, fecal coliforms, and E. coli were not detected in all of the water samples at initial. However, aerobic plate counts of three types of spring water and three types of bottled drinking water stored at room temperature showed higher levels than the standards in 5 days. Total coliforms were detected in three types of spring water after one day's storage at room temperature, and in one type of bottled drinking water after 5 days' storage. These results indicate that some of the spring water surveyed are not safe to drink, and the spring water and bottled drinking water after opening the lid should not be stored at room temperature, if they are used for drinking.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.6
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• pp.839-846
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• 2011

To investigate corrosivity characteristics of raw water in Korea, Langelier index (LI) of 30 multi-regional water treatment plants (WTPs) were evaluated. Annual average values of LI at 30 WTPs were all negative, which means raw water in Korea is very corrosive. LI results for 4 major rivers showed that raw water from Han and Nakdong had relatively high values compared to those of Sumjin and Keum. On the other hand, LI values of raw water from the tributaries of four major rivers were relatively low presumably due to geological characteristics, and in some cases the values were less than -4.0 which means increase of LI is urgently needed to minimize red water problem. Based on the correlation results among LI and water quality parameters, pH, water temperature, calcium concentration were confirmed as major components for LI. Therefore, pH and calcium concentration control is an effective method for the improvement of LI in water treatment processes.