Analysis of Changes in River Water Quality Due to Weir Installation

Abstract

There has been an increase in the amount of pollutants such as biochemical water and factory wastewater discharged from urban areas as a result of urbanization and industrialization. Therefore, research on securing water resources and improving water quality in rivers around cities is being actively conducted. This study analyzed the pattern of change of water quality due to the installation of overflow type weirs among the hand structures in the existing river. The target watershed was performed at Gilancheon, located in Andong-si, Gyeongsangbuk-do. The flow coefficient was calculated by analyzing the flow velocity and water level according to weir installation using the HEC-RAS. Afterwards, the QUALKO model was built, and the water quality analysis according to weir installation was performed by applying the flow coefficient calculated using HEC-RAS. As a result of the analysis, the flow rate was found to have decreased, and a stagnation section occurred due to the influence of weir installation, resulting in an increase in Chl-a. Due to the increase of Chl-a, BOD increased by 29%-32%, and T-N and T-P, which are nutrients for Chl-a, decreased. Therefore, an increase in Chl-a concentration due to weir installation can cause eutrophication due to the growth of green algae in the river, and it is believed that it can greatly affect the deterioration of water quality. Furthermore, it is considered that it will be able to help predict changes in water quality for the installation and operation of weirs in the future.