• Journal of Wetlands Research
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• v.19 no.3
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• pp.311-317
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• 2017

In this study, the water quality index was calculated using the water quality monitoring data in the Nakdong River water system and the water quality status was compared with the living standard. The water quality index was selected by the RWQI method CCME-WQI currently used by the Ministry of Environment. The water quality items were selected as 7 items for pH, DO, EC, water temperature, TOC, T-N and T-P. The evaluation period was selected from the last three years (2013~2015) and water quality monitoring data measured within the period were used. As a result of the evaluation, the results of the previous evaluation showed similar tendency to the index of living environment, but the monthly evaluation showed different BOD and T-P results. Therefore, it is concluded that it is more reliable that more complex evaluation than single water quality evaluation is needed for efficient river management.

• Korean Journal of Ecology and Environment
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• v.38 no.spc
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• pp.54-57
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• 2005

It is important to assess the change of water environment in the present and past. In this study, present-day water quality standards are applied to the expressions in literary works to reconstruct the historical water environment including the quality. As the result, the historical reconstruction of water quality has been made distribution of water quality from 1905 to 1935 for the Sumida River in Tokyo.

• Water Engineering Research
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• v.3 no.2
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• pp.143-153
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• 2002

As the natural flows in rivers dramatically decrease during drought season in Korea, a deterioration of river water quality is accelerated. Thus, consideration of downstream water quality responding to changes in reservoir release is essential for an integrated watershed management with regards to water quantity and quality. In this study, water quality models based on artificial neural networks (ANNs) method were developed using historical downstream water quality (rm $\NH_3$-N) data obtained from a water treatment plant in Geum river and reservoir release data from Daechung dam. A nonlinear multiple regression model was developed and compared with the ANN models. In the models, the rm NH$_3$-N concentration for next time step is dependent on dam outflow, river water quality data such as pH, alkalinity, temperature, and rm $\NH_3$-N of previous time step. The model parameters were estimated using monthly data from Jan. 1993 to Dec. 1998, then another set of monthly data between Jan. 1999 and Dec. 2000 were used for verification. The predictive performance of the models was evaluated by comparing the statistical characteristics of predicted data with those of observed data. According to the results, the ANN models showed a better performance than the regression model in the applied cases.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.11
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• pp.641-649
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• 2017

In the study, the water quality of the Imjin River basin with pollutants of changing characteristics it was determined through statistical analysis, correlation analysis, principle component and factor analysis, and cluster analysis. Among all analyzed data points, the average water quality concentration at the Sincheon 3 site shows high levels of BOD 13.4 mg/L, COD 19.9 mg/L, T-N 11.145 mg/L, T-P 0.336 mg/L, TOC 14.2 mg/L, indicating that Sincheon basin requires intersive water quality management out of the entire drainage basin. The correlational analysis of comprehensive water quality data shows statistically significant correlation between COD, TOC, BOD, T-N water quality factors, as well as finding of high correlation between organic and nutrients. The principal component analysis show that 2 main components being extracted at 81.221% from the measuring station's entire data, while seasonal data show 3 main components being extracted at 96.241%. Factor analysis of the entire data set and the seasonal data identify BOD, COD, T-N, T-P, TOC as the common factors influencing water quality. The spatial and temporal cluster analysis showed 4 groups and 3 groups, respectively, according to seasonal characteristics and land use. By analysing the water quality factors for the Imjin River basins over an 8 year period, with consideration to the spatial and temporal characteristics, this study will become the fundamental analytic data that will help understand the future changes of water quality in the Imjin River basin.

• Korean Journal of Environmental Agriculture
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• v.31 no.2
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• pp.200-204
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• 2012

BACKGROUND: Recently, the project for improvement of water quality and preservation of the Yeongsan and Seomjin river basin was actively promoted. However, the publicity for many results of the project is not actively done, thus they are rarely used. Furthermore, there are not sufficient information about the projects preformed by other research institutions. Therefore, the watershed management system for efficient water management is needed in the Yeongsan and Seomjin river basin. CONCLUSION: Firstly, establishment of the Yeongsan and Seomjin river basin management research center, Secondly, construciton of wed-based water management research network. These results will serve as a basic data for efficient water management.

• Journal of Korean Society on Water Environment
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• v.28 no.4
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• pp.561-573
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• 2012

The object of this study was to analyze long-term water quality gradients during 1992-2008 at six sites of Geumho River and near-by two sites of Nakdong River and their influences on fish trophic guilds and tolerance guilds along with ecological health. Water quality including biological oxygen demand (BOD), chemical oxygen demand (COD), conductivity, total phosphorus (TP), total nitrogen (TN), and total suspended solids (TSS) varied largely depending on the sampling locations and seasons. Values of ambient BOD, COD, TP, and TN were greater in the downstream than in the upstream reach, and seasonal and interannual variabilities were also higher in the downstreams. This phenomenon was evident due to a dilution by the Asian monsoon rainfall during the monsoon. These outcomes indicate that point sources near the downstream are important for the chemical conditions, but also seasonal stream runoff was considered as an important factor regulating the chemical conditions. Conductivity decreased rapidly during the summer due to ionic dilution, and nutrients (N, P), BOD, COD had an inverse function of seasonal precipitation. Based on the water quality, we selected two sites (control site = $C_s$ vs. impacted site = $I_s$) for impact analysis of water chemistry on fish community and trophic/tolerant guilds. Fish guild analysis showed that species diversity was higher in the headwater stream ($C_s$) than the impacted downstream ($I_s$), and that the proportion of tolerant and omnivore species were greater in the impacted site of downstream. Comparisons of water quality between Geumho River and Nakdong River indicated that Geumho River was considered as a point source which degradated water quality to the Nakdong River. Overall, chemical water quality and fish guild analysis suggest that even if current chemical quality got better after 1996 due to continuous constructions of wastewater disposal plants near the downstreams, fish compositions of tolerant and omnivores were still dominated the community. Thus, biological restoration based on ecological health is required for the ecosystem conservation.

• Journal of Korean Society on Water Environment
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• v.24 no.5
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• pp.581-591
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• 2008

Most of our rivers are fragmented by the presence of at least one large dam. Dams are often the most substantial controller of the flow regimes and aquatic environments of natural river system. The quality of downstream water released from a stratified reservoir is highly dependent on upstream reservoir water quality. Thus, an integrated modeling approach is more efficient, compared to fragmented modeling approach, and necessary to better interpret the impact of dam operation on the down stream water quality. The objectives of this study were to develop an integrated reservoir-river modeling system for Daecheong Reservoir and its downstream using a two-dimensional laterally averaged hydrodynamic and water quality model, and evaluate the model's performance against field measurement data. The integrated model was calibrated and verified using filed data obtained in 2004 and 2006. The model showed satisfactory performance in predicting temporal variations of water stage, temperature, and suspended solid concentration. In addition, the reservoir-river model showed efficient computation time as it took only 3 hours for one year simulation using personal computer (1.88 Ghz, 1.00 GB RAM). The suggested modeling system can be effectively used for assisting integrated management of reservoir and river water quality.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.1
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• pp.49-57
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• 2014

The survey of nitrosamine occurrence at Nakdong river is conducted in this study. According to the study results, six nitrosamine compounds (NDEA as N-nitrosodiethylamine, NDPA as N-Nitrosodi-n-propylamine, NDMA as N-nitrosodimethylamine, NMEA as N-nitrosomethylethylamine, NDBA as N-nitrosodi-n-butylamine, and NDPHA as N-Nitrosodiphenylamine) were detected at the Nakdong river. Among these, NDEA and NDPA are the most important compounds in terms of the nitrosamine contamination of Nakdong river. The detected concentration of NDEA exceeded the CDHCS (California Department of Health Care Services) response level of 100 ng/L at several sites. The detected concentration of NDPA approached the response level (500 ng/L) at few sites. When all nitrosamine concentrations were summed up, the maximum concentration of 735.7 ng/L was detected at the Nakdong river.

• Journal of Korean Society of Water and Wastewater
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• v.14 no.2
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• pp.181-195
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• 2000

The effect of the intercepting ratios on the water quality improvement was simulated by using Finite Segment Method in a urban river where intercepting sewer under the ground and constructing sewage treatment plant are now being proceeded. To simulate variations of the water quality caused by river flows, rating curve at each gaging station was derived from measurements. Water quality data were from the exiting observations at each key stations from 1990 to 1998, for 1999 and 2000 data we measured in creek and drainage ditch in addition to observation stations. It revealed that increasing the intercepting ratios improved the water quality.

• Journal of Korean Society on Water Environment
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• v.33 no.1
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• pp.78-89
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• 2017

Water quality monitoring network data is being affected continuously due to non-point source pollution arising from agricultural land located on the Gwangsancheon outlet in the Nakdong River basin. In this study, we have performed analysis of water quality monitoring system, water quality pattern using SOM and water quality in the Gwangsancheon for sub-basin located at Gisan-myeon in the Nakdong River basin. We have developed and applied the model to estimate the runoff and non-point source loading. As a result of SOM pattern, the effect of non-point source pollution was the largest in the paddy fields and fields. As a result of the developed model, we found contribution rate and reduction rate for non-point source loading according to change of landuse because the reduction effect of nonpoint pollutants was 20.9% of SS, 9.9% of TN, 21.2% of TP and 8.9% of TOC depending on the landuse change.