Analysis of the Water Quality Characteristics of Urban Streams Using the Flow–Pollutant Loading Relationship and a Load Duration Curve (LDC)

Ji-Yun Jang,Dae-Woong Kim,Dong-Woo Jang,Ye-Ji Choi

doi:10.3390/app11209694

Abstract

For urban streams, wastewater inflow makes water quality management difficult. This study attempted to analyze the water quality characteristics and pollution sources for the efficient management of water quality in the upper, middle, and lower Gul-po stream reaches. The water quality and flow characteristics for each point were analyzed using five-year water quality and flow discharge data at Gul-po stream from 2016 to 2020. The results showed that the flow increased and the water quality improved in the upper part of the stream, under the influence of a treated water discharge. The flow–pollutant loading equation revealed that the flow coefficient (slope of the regression equation) values of the water quality characteristics, except T-N, were lower than 1 in the upper part, indicating that the water quality decreased as the flow increased. In the middle and lower parts, the flow index values of the water quality characteristics, except T-N, were greater than 1, indicating that the water quality increased with the flow. For the middle and lower parts, the overage rate of target water quality by the Ministry of Environment was high for high-flow discharge sections, indicating the significant influence of nonpoint pollution sources. These results show that it is necessary to consider different pollution sources at each point for urban stream quality management.

Highlights

Since the 1960s, the amount of pollutants introduced to streams has increased due to the increase in wastewater discharge caused by rapid urbanization and industrialization
When the average flow and the concentrations of six water quality factors in the upper, middle, and lower parts of the Gul-po stream were measured through the total maximum daily load (TMDL) monitoring network and analyzed, it was found that the discharge in the upper and middle parts increased after 2018
Water quality and flow status were identified for the Gul-po stream, a stream subjected to the total maximum daily load (TMDL) program in the Han River system, using water quality concentrations and daily flow data as measured by the TMDL

Summary

Introduction

Since the 1960s, the amount of pollutants introduced to streams has increased due to the increase in wastewater discharge caused by rapid urbanization and industrialization. Nonpoint pollution sources are difficult to quantify because their discharge is different depending on topographical conditions, the characteristics of the watershed, land use type, and hydrological conditions [1,2,3,4,5,6]. To address this problem, the Ministry of Environment (ME; Rep. of Korea) implemented the total maximum daily load (TMDL) program on the Nakdong River in 2004. The TMDL program of South Korea is managing to achieve the target water quality at the reference flow, which involves specific flow conditions averaged over the past decade. There is a limitation for managing the water quality using TMDL for the various flow conditions [7]

Methods

Results

Conclusion