• Journal of Korean Society of Environmental Engineers
• /
• v.30 no.12
• /
• pp.1225-1230
• /
• 2008

A new approach based on the Seasonal Mann-Kendall Trend Analysis, was presented in this paper, in order to estimate effect of water quality management policy in Kyoungan Stream which is one of major tributaries into the Lake Paldang. The estimation was undertaken by comparing water quality trend slopes before and after implementation of the policy. The monthly water quality data of Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Nitrogen (TN) and Total Phosphorus (TP) measured from 1992 to 2005, were analyzed to determine the Kendall slopes before and after the Han River special policy implemented at 1998. The results indicated that the 1998 special policy would be effective in water quality improvement not at upstream but at downstream. This result agrees well with the previous water quality studies at Kyoungan stream. It was suggested that the presented approach could be an useful tool to estimate effect of a water quality management policy.

• Journal of Wetlands Research
• /
• v.20 no.3
• /
• pp.201-209
• /
• 2018

In this study, the water quality index was calculated using the water quality monitoring data of the major tributaries of the Nakdong River and long-term trend analysis was performed to identify the tributaries requiring priority management. We used a Real-Time Water Quality Index method implemented by the Ministry of Environment. Linear regression as a parametric method and Mann-Kendall Test and Sen Slope Test as a nonparametric method were applied for the trend analysis. The water quality index of major tributaries except for Migeon2 and Seokyo2 was in the range below Fair grade and there were no significant trends for the rest of the sites except Bukan, Chennae, Hogye, Yongdeok. Therefore, in order to improve the water quality of the main stream, management of the tributaries should be preceded.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.66 no.2
• /
• pp.25-34
• /
• 2024

The long-term monitoring of the Soyang Lake's water quality, covering 25% of the North Han River watershed, is crucial for effective management of both lake water quality and pollution sources in the broader region. This study utilized continuous monitoring data from the front of the Soyang Dam spanning 2003 to 2022, aiming to analyze trends and provide foundational insights for water quality management. Results revealed a slightly poor grade (IV) for total nitrogen (T-N) in both surface and mid-depth layers, indicating a need for concentrated T-N management. Trend analyses using the Mann-Kendall test and Sen's Slope depicted a decreasing trend in total phosphorus (T-P) for both layers, attributed to non-point source pollution reduction projects initiated after the Soyang Lake's designation as a pollution control area in 2007. The LOWESS analysis showed a T-P increase until 2006, followed by a decrease, influenced by the impact of Typhoon Ewiniar in that year. This 20-year overview establishes a comprehensive understanding of the Soyang Lake's water quality and trends, allowing for a seasonal and periodical analysis of water quality changes. The findings underscore the importance of continued monitoring and management strategies to address evolving water quality issues in the Soyang Lake over time.

• Journal of Korean Society of Rural Planning
• /
• v.26 no.4
• /
• pp.53-65
• /
• 2020

This study aimed to provide a basic information for managing the water quality of national and regional 1st rivers in Gyeongnam by analyzing the emerging hot spot patterns in BOD, T-P, and TOC, and by grouping the changing trends into clusters. The emerging hot spot analysis for each water quality item was implemented in ArcGIS Desktop with monthly water quality data from 96 water environmental monitoring stations in Gyeongnam, and then four patterns of water quality change were classified by the K-mean cluster analysis. As for BOD, persistent cold spot pattern covered about 42.9% of target rivers, and T-P concentration tended to be low or be getting lower at over 70% of target rivers. While, for TOC, about 70% of target rivers resulted in oscillating hot spots. In addition, the cluster analysis showed that the downstream of Nakdong river had the top priority in terms of water quality management because of the increasing concentration for all the three water quality.

• Journal of Wetlands Research
• /
• v.24 no.4
• /
• pp.256-267
• /
• 2022

This study analyzed the current status and trend of water quality using long-term water quality monitoring data measured over the past 5 years in the Seohwacheon Basin, located upstream of Daecheong Lake. In the Seohwacheon Basin, a project is underway to reduce the occurrence of algal blooms in the Daecheong Lake and to improve water quality, and continuous management is required for water quality management. The current water quality evaluation aims to identify the water quality management point, and the good water grade and the integrated water quality index (WQI) were used. For trend evaluation, the effect of the water quality improvement project was evaluated using the Mann-Kendall test and Sen's Slope. As a result of the evaluation, the current water quality index was used to identify the watersheds and when to manage water quality, and the effect of the improvement project was confirmed through trend analysis. Through this study, it is possible to review the water quality status and improvement effect using long-term water quality monitoring data, so it is expected to be applicable to similar types of watersheds in the future.

• Journal of Korean Society on Water Environment
• /
• v.39 no.5
• /
• pp.377-389
• /
• 2023

Chungcheongnam-do has been measuring the flow rate and water quality of streams in the province once a month since 2011 in order to water environment policies. Based on the results, after evaluating the coefficient of variation and the tendency of the water quality trend by using the Mann-Kendall test and Sen's Slope for each stream, the streams subject to priority introduction of Total Pollution Load Management at Tributaries were selected through the Stream Grouping Method. The water quality trend analysis results for 125 streams using the Mann-Kendall test and Sen's Slope were evaluated as streams showing a tendency of deteriorating water quality Biochemical oxygen demand (BOD): 13 streams, Total Phosphorus (T-P): 16 streams). Streams with deteriorating water quality were classified into A-D groups using the Stream Grouping Method. Group A, which has a high flow rate and high water quality, is a stream that requires priority management, and was selected as a stream for introduction of Total Pollution Load Management at Tributaries. There are 7 streams that need to be introduced into the BOD category, and there are 7 streams that need to be introduced into the T-P category. In this study, based on flow and water quality monitoring data accumulated over a long period of time (2011-2022), statistical techniques are used to select watersheds in which water quality is deteriorating. Accordingly, it is expected that it will be useful in establishing a water quality improvement plan in the future.

• Membrane and Water Treatment
• /
• v.10 no.5
• /
• pp.339-352
• /
• 2019

Long term water quality change was analyzed to evaluate the effect of the Total Maximum Daily Load (TMDL) policy. A trend analysis was performed for biochemical oxygen demand (BOD) and total phosphorus (TP) concentrations data monitored at the outlets of the total 41 TMDL unit watersheds of the Nakdong River in the Republic of Korea. Because water quality data do not usually follow a normal distribution, a nonparametric statistical trend analysis method was used. The monthly mean values of BOD and TP for the period between 2004 and 2015 were analyzed by the seasonal Mann-Kendall test and the locally weighted scatterplot smoother (LOWESS). The TMDL policy effect on the water quality change of each unit watershed was analyzed together with the results of the trend analysis. From the seasonal Mann-Kendall test results, it was found that for BOD, 7.8 % of the 41 points showed downward trends, 26.8 % and the rest 65.9% showed upward and no trends. For TP, 51.2% showed no trends and the rest 48.8% showed downward trends. From the LOWESS analysis results, TP began to decrease in most of the unit watersheds from mid-2010s when intensive chemical treatment processes were introduced to existing wastewater treatment plants. Overall, for BOD, relatively more points were improved in the main stream compared to the points of the tributaries although overall trends were mostly no trend or upward. For TP, about half of the points were improved and the rest showed no trends.

• Journal of Environmental Health Sciences
• /
• v.42 no.4
• /
• pp.280-292
• /
• 2016

Objectives: The objective of this study was to build COD regression models for the Han River and evaluate water quality. Methods: Water quality data sets for the dry season (as of January) during a four-year period (2012-2015) were collected from the database of the Han River automatic water quality monitoring stations. Statistical techniques, including combined genetic algorithm-multiple linear regression (GA-MLR) were used to build five-descriptor COD models. Multivariate statistical techniques such as principal component analysis (PCA) and cluster analysis (CA) are useful tools for extracting meaningful information. Results: The $r^2$ of the best COD models provided significant high values (> 0.8) between 2012 and 2015. Total organic carbon (TOC) was a surrogate indicator for COD (as COD/TOC) with high reliability ($r^2=0.63$ in 2012, $r^2=0.75$ for 2013, $r^2=0.79$ for 2014 and $r^2=0.85$ for 2015). The ratios of COD/TOC were calculated as 2.08 in 2012, 1.79 in 2013, 1.52 and 1.45 in 2015, indicating that biodegradability in the water body of the Han River was being sustained, thereby further improving water quality. The BOD/COD ratio supported these findings. The cluster analysis revealed higher annual levels of microorganisms and phosphorous at stations along the Hangang-Seoul and Hantangang areas. Nevertheless, the overall water quality over the last four years showed an observable trend toward continuous improvement. These findings also suggest that non-point pollution control strategies should consider the influence of upstreams and downstreams to protect water quality in the Han River. Conclusion: This data analysis procedure provided an efficient and comprehensive tool to interpret complex water quality data matrices. Results from a trend analysis provided much important information about sources and parameters for Han River water quality management.

• Korean Journal of Ecology and Environment
• /
• v.42 no.1
• /
• pp.39-47
• /
• 2009

Spatial and temporal analysis of water quality was performed for eleven monitoring stations in Dongjin River watershed in order to determine the trends of monthly water quality. The monthly water quality data of biochemical oxygen demand (BOD), total nitrogen (TN) and total phosphorus (TP) during $1995{\sim}2004$, were analyzed utilizing Seasonal Mann-Kendall test, LOWESS and three-dimensional graphic approaches. The results indicated that BOD and TN concentrations had the downward trend, but TP showed the upward trend, especially in Gobucheon. This numerical and graphic analysis is the useful tool to analyze the long-term trend of water quality in a large river system.

• Journal of Korean Society on Water Environment
• /
• v.33 no.1
• /
• pp.40-50
• /
• 2017

We were interested in the long-term temporal and spatial variability trends of water quality. Trend tests such as the Seasonal and Regional Kendall tests and LOWESS (LOcally WEighted Scatter plot Smoother) have been recommended as outstanding tools for trend detection. In this study, we conducted four types of nonparametric trend tests (Seasonal and Regional Kendall tests, LOWESS, and flow-adjusted Seasonal Kendall). We aimed to identify water quality trends using the monthly data for five variables (BOD, COD, TN, TP, and flow) collected from 24 sites in the Nakdong River from August 2004 to December 2013. According to the Regional Kendall test, BOD, COD, and TN increased but TP decreased trend. The Seasonal Kendall test showed that BOD, TN, and TP remained constant at 62.5-83.3% of the sites. COD remained constant at 58.3% of the sites. LOWESS showed that TP gradually increased between 2007 and 2008, then decreased slowly at the Gumi, Geumhogang6, Daeam-1 and Milyanggang3 sites. BOD increased slightly between 2008 and 2009, and then decreased slowly at the Namgang4-1 site. Lastly, a flow-adjusted Seasonal Kendall test was conducted. There were different results between Seasonal Kendall and flow-adjusted Seasonal Kendall tests at 11 of the 24 sites. According to the results from six of the eleven sites, BOD increased at one site, showed no trends at three sited, and decreased at two sites. Each of COD, TN increased at two, one site. but TP decreased at two sites.