• Environmental Engineering Research
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• v.19 no.3
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• pp.197-203
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• 2014

This study estimated spatial and seasonal variation of water quality to understand characteristics of Nakdong river basin, Korea. All together 11 parameters (discharge, water temperature, dissolved oxygen, 5-day biochemical oxygen demand, chemical oxygen demand, pH, suspended solids, electrical conductivity, total nitrogen, total phosphorus, and total organic carbon) at 22 different sites for the period of 2003-2011 were analyzed using multivariate statistical techniques (cluster analysis, principal component analysis and factor analysis). Hierarchical cluster analysis grouped whole river basin into three zones, i.e., relatively less polluted (LP), medium polluted (MP) and highly polluted (HP) based on similarity of water quality characteristics. The results of factor analysis/principal component analysis explained up to 83.0%, 81.7% and 82.7% of total variance in water quality data of LP, MP, and HP zones, respectively. The rotated components of PCA obtained from factor analysis indicate that the parameters responsible for water quality variations were mainly related to discharge and total pollution loads (non-point pollution source) in LP, MP and HP areas; organic and nutrient pollution in LP and HP zones; and temperature, DO and TN in LP zone. This study demonstrates the usefulness of multivariate statistical techniques for analysis and interpretation of multi-parameter, multi-location and multi-year data sets.

• Journal of Environmental Impact Assessment
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• v.20 no.5
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• pp.705-716
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• 2011

For the efficient discovery of knowledge and information from the observed systems, data mining techniques can be an useful tool for the prediction of water quality at intake station in rivers. Deterioration of water quality can be caused at intake station in dry season due to insufficient flow. This demands additional outflow from dam since some extent of deterioration can be attenuated by dam reservoir operation to control outflow considering predicted water quality. A seasonal occurrence of high ammonia nitrogen ($NH_3$-N) concentrations has hampered chemical treatment processes of a water plant in Geum river. Monthly flow allocation from upstream dam is important for downstream $NH_3$-N control. In this study, prediction models of water quality based on multiple regression (MR), artificial neural network and data mining methods were developed to understand water quality variation and to support dam operations through providing predicted $NH_3$-N concentrations at intake station. The models were calibrated with eight years of monthly data and verified with another two years of independent data. In those models, the $NH_3$-N concentration for next time step is dependent on dam outflow, river water quality such as alkalinity, temperature, and $NH_3$-N of previous time step. The model performances are compared and evaluated by error analysis and statistical characteristics like correlation and determination coefficients between the observed and the predicted water quality. It is expected that these data mining techniques can present more efficient data-driven tools in modelling stage and it is found that those models can be applied well to predict water quality in stream river systems.

• Journal of Korean Society on Water Environment
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• v.28 no.4
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• pp.551-560
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• 2012

The objectives of this study were to elucidate spatio-temporal heterogeneity of water chemistry and develop empirical models using trophic variables in Daechung Reservoir during 2005-2010 along with in situ tests of nutrient enrichment bioassays (NEB). The relations of water quality parameters in regard to precipitation showed that seasonal and interannual fluctuations of biological oxygen demand (BOD), total nitrogen (TN) and pH were minor, whereas conductivity, suspended solids (SS), and total phosphorus (TP) were largely varied in response to the magnitude of rainfall. The CHL maxima occurred immediately after the spate of TP during the high flow, indicating that phytoplankton growth was directly controlled by phosphorus. Empirical linear models of CHL-TP indicated that the variation of CHL in premonsoon was accounted 60% ($R^2$ = 0.60, p < 0.05, n = 54) by TP. In the mean time, empirical models of annual CHL-TN showed that the variation of CHL was weakly accounted ($R^2$ = 0.16, p < 0.001) by TN and more strongly ($R^2$ = 0.44, p < 0.001) by TP. Thus, the variation of CHL was more explained by the variation of TP than TN. In situ tests of Nutrient Enrichment Bioassays (NEBs) showed that the growth of CHL was greater in the P-treatments (as $PO_4-P$) than the control and N-treatment (as $NO_3-P$). Overall, our results suggest that phosphorus was aprimary limiting nutrient controlling the seasonal phytoplankton growth, based on the in situ experiments of NEBs.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.9
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• pp.648-658
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• 2014

We examined the effects of pollutants into sub-basin on the water quality and loading based on data surveyed during January-December 2013 from 13 sites of 5 streams in the Jinwi watershed. We used the contour plot and Kruskal-Wallis rank sum test to analyze seasonal variation of water quality and loading and Pearson correlation analysis to assess the relationships between pollutants and loadings. The significantly higher seasonal variation were SS, TN and TOC as compared to other water quality constituents (P < 0.001). A significant interaction existed between the effects of human population and the effects of discharge of Sewage Treatment Plant (STP) on water quality and loading, especially for the spring and winter seasons. It is necessary to control discharge water of sewage and wastewater from industrial facilities and to make full use of the watershed management system such as TMDLs in operation since 2012 for improvement in stream water quality.

• Korean Journal of Ecology and Environment
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• v.52 no.2
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• pp.94-104
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• 2019

In this study, we investigated the spatial variation in land use and topographic effects on water quality at the Geum river watershed in South Korea, using the ordinary least squares(OLS) and geographically weighted regression (GWR) models. Understanding the complex interactions between land use, slope, elevation, and water quality is essential for water pollution control and watershed management. We monitored four water quality indicators -total phosphorus, total nitrogen, biochemical oxygen demand, and dissolved oxygen levels - across three land use types (urban, agricultural, and forested) and two topographic features (elevation and mean slope). Results from GWR modeling revealed that land use and topography did not affect water quality consistently through space, but instead exhibited substantial spatial non-stationarity. The GWR model performed better than the OLS model as it produced a higher adjusted $R^2$ value. Spatial variation in interactions among variables could be visualized by mapping $R^2$ values from the GWR model at fine spatial resolution. Using the GWR model, we were able to identify local pollution sources, determine habitat status, and recommend appropriate land-use planning policies for watershed management.

• Journal of Korean Society of Water and Wastewater
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• v.14 no.1
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• pp.108-116
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• 2000

Chlorine is widely used as a disinfectant in drinking-water systems throughout the world. Chlorine residual was used as an indicator for prediction of water quality in water distribution systems. The variation of chlorine residual in drinking water distribution systems of Suwon city was simulated using EPANET. EPANET is a computerized simulation model which predicts the dynamic hydraulic and water quality behavior within a water distribution system operating over an extended time period. Sampling and analysis were performed to calibrated the computer model in 1999 (Aug. Summer). Water quality variables used in simulations are temperature, roughness coefficient, pipe diameter, pipe length, water demand, velocity and so on. Extended water residence time affected water quality due to the extended reaction time in some areas. All area showed the higher concentration of chlorine residual than 0.2mg/l(standard). So it can be concluded that any area in Suwon city is not in biological regrowth problem. Rechlorination turned out to be an useful method for uniform concentration of free chlorine residual in distribution system. The cost of disinfectant could be saved remarkably by cutting down the initial chlorine concentration to the level which guarantees minimum concentration (0.2mg/l) throughout the distribution system.

• Journal of Environmental Science International
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• v.6 no.6
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• pp.679-688
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• 1997

In order to analyze the water quality variation of surface water around the Sudokwon landfill site, seasonal variations of water temperature, pH, DO. HOD, COD, SS, NH3-N, NO2-N, and NO3-N were examined at 10 sites from January to December, 1996. It was found that the estimates of COD, DO. SS, and $NH_3-N$ were Increased compared with the results of environmental Impact assessment carried out In 1988. Higher estimates of COD, DO, and SS were due to Industrial and agricultural wastewater, and the Increase of NH3-N at Jangdo reservoir strate was due to the leachate from the landfill. In particular, the estimate of 55 was found to be increased by the soil wash from the landfill during the heavy rainy days.

• Ocean and Polar Research
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• v.31 no.1
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• pp.63-70
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• 2009

Eutrophicated water fed through Mankyeong River and Dongjin River into the new Saemankeum Lakemight seriously affect the water quality and phytoplankton community in the lake. To obtain control reference data for the later studies on environmental changes due to the construction of the Saemankeum Sea Wall, we performed a monthly investigation on the physico-chemical properties of the water and phytoplankton community at 3 stations in the Mankyeong River Estuary over 14 months starting from September 1999. Water temperature ranged from $0.3{\sim}32.9^{\circ}C$ due to the typical seasonal variations in temperate on the coasts and salinity exhibited a wide annual range of $0.2{\sim}33.7$ psu along with regular and huge hourly variations according to tidal cycles. Inorganic nutrients were supplied from rivers to the monitoring station and the whole lake. The average concentration of total-N, $6.99\;mg{\cdot}l^{-1}$, was higher than the water quality for agricultural use with peak values occurring in winter. Species composition showed a seasonal succession pattern, where a high diversity was observedin summer and autumn and vice versa in winter. Hourly variations of water properties in the "Mankyeong bridge" Station were quite regular and well in accordance with the daily tidal cycles. The different degree of sea water intrusion during the flood tide at each of the 3 stations exhibited a different range and variation pattern of water temperature and salinity throughout a day. Hourly changes in species composition were in harmony with the daily tidal cycles, resulting in extremely variable spatio-temporal variation.

• Journal of Korean Society of Rural Planning
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• v.7 no.1 s.13
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• pp.89-98
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• 2001

This study was carried out to provide the basic informations for the water quality management in Boryung fresh water reservoir watershed. Four agricultural reservoirs were selected and the water qualify of the reservoirs were investigated from November 1998 to December 2000, periodically. Including storage rate, temporal variation of water quality constituents such as water temperature, pH, EC, total nitrogen, total phosphorus were analysed. The result showed that pH ranged $6.7{\sim}10.4$, EC $56.1{\sim}1079{\mu}S/cm$, COD $0.75{\sim}8.0mg/L$, respectively. And, total-N concentration affected by the livestock wastes and agricultural activity ranged from 0.21 to 4.66mg/L and which was almost over the agricultural water quality standard(1.0mg/L). Total-P ranged from 0.001 to 0.080mg/L as lower than the agricultural water quality standard(0.1mg/L).

• Journal of Environmental Impact Assessment
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• v.14 no.1
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• pp.37-46
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• 2005

In this study, field surveys were performed for 12 stations in main stream of Hongjechun and 3 stations in 2 tributaries, respectively, in order to find out dried reaches of the stream, and to examine the water quality of the stream, and to suggest methods to improve the stream concerned into eco-stream. In the results of water quality in stream, however distinct difference for seasonal variation of the water quality was not found, the water quality of winter was relatively better than that of other seasons. Annual mean concentration of BOD was 6.5mg/L in the upper reach, 11.8mg/L in the middle reach, 15.3mg/L in the lower reach of main stream, and total mean was 12.5mg/L, while the BOD concentration was 3.6mg/L in the upper reach, and was 9.6mg/L in the low reach of Gukichun, the tributary. Based on flow examination, the level of water depth was so low and the flow can not be traveled downstream in the reach between ST-9 and ST-10 for low water season, whereas it was observed that the flow was traveling except the dry season even the water level was lower than that of adjacent stations.