2D WATER QUALITY ANALYSIS SYSTEM IN HAN RIVER

Kun-Yeun Han

Professor of Civil Engineering, Kyungpook National University

1370, Sankyuk-dong, Puk-gu, Taegu, 702-701, South Korea

Tel : 82-53-950-5612, Fax : 82-53-950-6564, kshanj@knu.ac.kr

Eul-Rae Lee

Lecturer of Civil Engineering, Kyungpook National University

1370, Sankyuk-dong, Puk-gu, Taegu, 702-701, South Korea

Sang-Ho Kim

Senior Researcher, Korea Institute of Construction Technology

2311, Daehwa-dong, Ilsan-gu, Koyang, Kyonggi-do, 411-712, South Korea

Abstract: Current industrial development and population growth have been caused a rapid increase of wastewater discharge. Also, frequently occurring drought has increased the necessity of an effective water quality control and management of river flows for reserving instream flows. This study attempted to develop a hydrodynamic numerical system composed of a two-dimensional flow prediction model and a contaminant transport model, and to apply the developed system for the scientific water quality control and management in the Han River. This study was to construct a GIS-based river flow system, and it is useful for supporting user's decision making for the on-line status through various analysis.

Keywords: water quality, hydrodynamic numerical system, control and management, GIS

1 INTRODUCTION

The aggravation of water quality at locations where intake plants and contaminated inflow sources coexist causes serious water quality problems during low flow periods. A typical example of such an area is the downstream reach of the main Han River passing through the Seoul metropolitan area with a population of 10 million.

The purpose of this study is to develop a hydrodynamic numerical system composed of a two-dimensional flow prediction model and a contaminant transport model, and to apply the system for the scientific water quality control and management in the Han River. The consistent two-dimensional finite element model for both accurate river flow prediction and advection-diffusion analysis of contaminant transport was developed by Petrov-Galerkin's finite element method. The developed model system was tested for water quality analysis when contaminants from tributaries and sewage treatment plants flow into the main river. The main features of this study are to provide the two-dimensional response characteristics of velocity distribution and contaminant transport.

This study also attempted to design water quantity and quality database related to GIS, and to provide analyzing techniques for the data. It also provided the scientific water quantity and quality management techniques based on GUI(Graphical User Interface) environment. The results from this study will be strongly contributed to the systematic water quantity and quality management on any other river basins in addition to the Han River.

Prior studies on finite element method for a hydrodynamic flow analysis in a river are conducted by Lee and Froehlich(1986), King and Norton(1978), Walters and Cheng(1978, 1980), Norton(1980), and Gee and MacArthur(1981). Lee and Froehlich applied the interpolation function of the same order for velocity and depth term when they analyze two dimensional shallow water equation by finite element method. Others applied the quadratic interpolation function for velocity term, and the linear interpolation function for the depth term. In addition, Katopodes(1984) applied the dissipative finite element method for surge analysis in open channels. Kinnmark and Gray(1982), and Hughes and Brooks(982) conducted the error analysis by using the modified form of Galerkin technique for the convection-diffusion analysis. Gray and van Genuchten(1978), and Pinder and Shapiro(1979) researched the finite element method for the convecton-diffusion analysis of pollutant in a river.

2 FINITE ELEMENT MODEL

Two dimensional shallow water wave equation and convection-diffusion equation are used to describe contaminant transport analysis in a river, as shown in Eqn. (1)∼(4).

(1)

(2)

(3)

(4)

Governing equations are solved by applying Petrov-Galerkin finite element method. The model developed in this study can handle the following situations.

- Metric and FSS unit

- Steady and unsteady state

- Point sources and nonpoint sources

3 2D WATER QUALITY ANALYSIS

The proposed model was applied to Han River basin in Korea. The Han River is the largest river in Korea and is located near the center of the Korean peninsula. The selected study area is the lower part of the main Han River from the Paldang dam to the Hangang bridge passing through the Seoul metropolitan area. This area contains three main contaminated tributaries, the Wangsook-chun, Tan-chun, and Joonglang-chun and includes several intake plants upstream of the Jamsil weir. The length of this section of the river is 34.5 km and the width ranges from 750 m to 1,200 m. The water depths are dependent on the upstream flow conditions, however, the minimum water depth is about 2.5 m. The survey locations for the measurement stations for the various water quality data officially operated by the Korean Ministry of Environment (MOE). Fig. 1 shows the simulation results of flow velocity. The collected data consist of water temperature, pH, DO, BOD, COD, SS, coliforms, T-N, and T-P on a daily basis. The computed results agreed with measured in terms of velocity, water depth and water quality concentrations. Fig. 2. shows the concentration distribution of BOD and DO in the Han River. Figs 3 and 4. show the verification results of flow velocity and pollutant concentrations, respectively.

4 GIS APPLICATION

An ideal water quantity and quality management system requires a reasonable matching between a good model and an accurate data system. The reasonable data sets required in the numerical model for water quality prediction does not often exist. Even though the need for the efficient database systems is evident in the area of water quality control, because of the complicated process of tremendous input and output data in modeling study and the visualization of spatial variation of contaminant transport, the tabular output or a station-oriented simple graphic representation of the results has been maintained widely in Korea so far.

GIS, which has already been widely used in many different areas such as water resources planning and urban planning, is a tool to overcome this limitation. In this sense, the use of GIS system on water resources and water quality management system will be very useful.

According to rules of making the digital maps, the transformation of the vectors of the base map was enforced, and 3D topographic data was developed. The base data used to create the geometrical form of the basin consisted of detailed field survey maps, a existing 1/5,000 topographic map, and a longitudinal and horizontal map of the River Management Plan of the Han River. This study was to construct a GIS-based river flow and quality management system. It is useful for supporting user's decision making for the on-line status through various analysis, editing, and merging of many different data sets.

5 CONCLUSIONS

This study was to establish a scientific water quality prediction and management system if there are multiple contaminant inflows in a river. The study attempted develop a two-dimensional model system and to apply the system in the Han River for the hydrodynamic advection-diffusion analysis of contaminant transport, and to design a GIS-based water quality management system for the scientific water quality control and management on the issued area. he proposed water quantity and quality management system had capability for the on-line data processing including water quality simulation, and had a postprocessor for the reasonable visualization of the various outputs. This study will be an efficient application of NGIS(National Geographic Information System), which is under developing by a government agency, for planning of water quantity and quality control and conservation.

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