Water Quality Modeling of the Lower Han River, Korea

Abstract

The Han River Basin in the Republic of Korea covers an area of about 27,000 sq km south of the Demilitarized Zone, almost one quarter of the total area of the country. The total population in the basin is of the order of 13 million, of which more than 80 percent are concentrated in the urban contrbation of Greater Seoul alongside the Lower Han River. Within the vicinity of Seoul the river is used extensively for water supply, irrigation and both contact and non-water contact recreation. Treated nightsoil, untreated sullage, partially treated sewage and industrial wastes generated in the urban areas are also discharged to the river which is heavily polluted in the downstream reaches as a result. The finite difference water quality model QUAL-II was adapted to the Lower Han River using data obtained from extensive field water quality surveys especially designed to provide the necessary calibration and verification data base. Hydraulic data for the model were obtained from operation of the U. S. Army Corps of Engineers HEC-II computer model. Model calibration and verification was confirmed by statistical comparison of model simulations with the field data. The calibrated model was used to evaluate a number of different treatment alternatives for two different future years. Extensive model sensitivity analyses were run on both the key model parameters and the treatment alternatives to quantify the reliability of the prediction.