| Title |
A Nonparametric Trend Tests Using TMDL Data in the Nakdong River |
| Authors |
김미아 ( Mi-ah Kim ) ; 이소영 ( Soyoung Lee ) ; 문현생 ( Hyunsaing Mun ) ; 조항수 ( Hang-soo Cho ) ; 이재관 ( Jae-kwan Lee ) ; 김경현 ( Kyunghyun Kim ) |
| DOI |
https://doi.org/10.15681/KSWE.2017.33.1.40 |
| Keywords |
Flow-adjusted Seasonal Kendall; LOWESS; Nakdong river; Seasonal and Regional Kendall |
| Abstract |
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 from the 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 sites, and decreased at two sites. Each of COD, TN increased at two, and one site. but TP decreased at two sites. |