The purpose of this study Is to develop water quality management system fort a farm village stream. The framework design of the system and the ecological monitoring of a test watershed were carried out, The system consists of GIS(Geographic Information System ), database, pollution source management, water quality and hydrologic analysis. Suri watershed located on Idong, Yongin city, Kyunggi Province, was selected as the test watershed for the application of the system. The fifteen's monitoring stations were chooses at up- and down-stream of the watershed. The results of an aquatic ecological monitoring were analyzed by the GPI(Group Pollution Index) method. The GPI revealed that water quality was varied within the stream. GPI and DO map for the watershed stream were developed, These maps facilitated to analyze the spatial distribution of the water quality.

A study was carried out on the distribution of chlorophyll a and water quality in the dry season in Yosuhae bay and adjoining sea, Southern Korea, in July of 1994. Concentration of salinity and phosphate were lower in the outer bay than in the inner bay. While nitrate and silicate were higher in the former than in the latter. We were identified with coastal water of origin from China with the lower salinity in outer bay. The China coastal water was characteristic of high nutrients and phytoplankton biomass, such as chlorophyll a. The principal component analysis (PCA) on the analytical data proved that high density of phytoplankton biomass occurred under the condition of low salinity and high concentration of dissolved inorganic nutrients. It is thought that the thermoharine structure and biological produtions of Yosuhae bay were controlled by the China coastal water in the outer bay.

This research emphasizes the necessity of the understanding and cooperation among local governments to preserve the water quality of the Nak-dong river that runs through four local governments. First, this research considers the status of water-pollution in the Nakdong river, describes and finds problems within the central government`s "Clean Water Supply Plan" and local governments` water quality-related policies. Second it deals with the conflict among local governments concerning the planning and building of Wicheon Industrial Complex" in the middleupstream of the Nakdong river which has triggered the opposition movement of the local governments and residents of the river`s downstream area. With stressing the necessity of the understanding and cooperation among local governments, this research emphasizes roles of central government, of academic experts, and of local news-media in preserving the water quality.

During the last two decades, many industrial complexes for heavy and chemical industries have been established along the Korean coastline, thereby increasing the pollution materials burden on the coastal environment of seawater. Masan Bay is one of the most polluted coastal areas in Korea and the main soures of pollutants are domestic and industrial wastewater from Masan, Changwon. This study was aimed to evaluate relationships among the physicochemical parameters in the bottom water of Masan bay and to examine environmental factors affecting to pollutions of seawater by factor analysis. The factor loading, 1 is showed higher increasing inclination after 1989 year in station 1. The variance of pollutant materials is showed 43.7% in which the coastal inflow water is indicated external loadings(factor 1 : NO3- -N, TN, factor 4 : SiO2-Si) corresponded to domestic sewage, industrial wastewater, and earth-sands in the bottom water of Masan bay. And the internal loadings(factor 2 : SS, salinity, factor 3 : W.T., DO) are explained 33.8% corresponded the phenomena of sedimentary layer and oxygen concentration. Therefore, The external loadings are explained by the higher factor pollutantal variance in Masan bay.

In order to provide for the guidance on groundwater quality monitoring network design and also, to suggest the index to the solution of the contaminated groundwater remediation problems in the lake watershed, it is necessary to analyze the contaminant transport in the groundwater. The solute transport was analyzed in the lake watershed to investigate the behavior of the injected contaminant sources depend on the relationships between the point of contaminant sources and position of the lake. Three hypothetical groundwater flow systems, which is composed of a flow-through lake and two solute sources, were considered. The lakes located in the upper, middle, and lower portions of a watershed respectively. The transported contaminant was numerically simulated for five years by using MT3D contaminant transport model under the three-dimentional steady state conditions. From the above simulations, it can be concluded that the contaminant concentration was high as the contaminant source located at the upper position of a watershed, and the influence of the contaminant injection was large as the solute source located at the lower position. When the injection of contaminant was continued for one year without regard to the position of contaminant source and the lake, the influence of contaminant source was reached to bedrock.

In order to study on the long-term change of water quality, water analysis was conducted at 16 sites surrounding the Kumho river system for 11 times from September 1990 to August 1993. Analytical items for the study of water quality are as follows; water temperature, pH, COD, BOD, DO, SS, electrical conductivity, NH_3-N, NO_2^- -N, NO_3^- -N, PO_4^3- -P, total-P, hardness, oil and grease, ABS, phenol, zinc, chromium, cadmium, manganese, iron, lead and color. The long-term change of water quality in the Kumho river for the period studied was found that the values of water temperature, electrical conductivity, phenol, NO_2^- -N and NH_3-N were increasing and those of COD, BOD, SS, oil and grease, ABS, NO_3 -N, PO_4^3- -P, copper, zinc, chromium, cadmium, manganese and lead were decreasing, while those of pH, hardness, iron and manganese were steady.

In order to provide the basic information for the water quality modeling, the water pollution indicators of Sin stream and Keumho river flowing through Taegu city were measured, and the periodical variations of these indicators were studied under the condition of stagnating for 19 days. For this experiment, three sampling sites(Sungpook bridge, Mutae bridge and Gangchang bridge) were selected. Sungpook bridge is located most down the Sin stream, Mutae bridge and Gangchang bridge are located on the lower Keumho river. The results were as follows. 1. The values of water pollution indicators measured at Mutae bridge were pH 8.7, TSS 51㎎/ℓ, TS 383㎎/ℓ, Cl^- 60.68㎎/ℓ, turbidity 32FTU, DO 8.58㎎/ℓ, oxygen deficit 2.02㎎/ℓ, COD 16.32㎎/ℓ, organic carbon 13.60㎎/ℓ. 2. At Gangchang bridge located down more than Mutae bridge, the values of these indicators were pH 8.0, TSS 26㎎/ℓ, TS 737㎎/ℓ, Cl^- 90.59㎎/ℓ, turbidity 37FTU,DO 3.49㎎/ℓ, oxygen deficit 7.11㎎/ℓ, COD 28.02㎎/ℓ, organic carbon 14.28㎎/ℓ. 3. At Sungpook bridge, the values of these indicators were pH 8.3, TSS 145㎎/ℓ, TS 344㎎/ℓ, Cl^- 32.51㎎/ℓ, turbidity 60FTU, DO 6.53㎎/ℓ, oxygen deficit 4.07㎎/ℓ, COD 43.79㎎/ℓ, organic carbon 11.03㎎/ℓ. 4. At Mutae bridge and Sungpook bridge of which initial DOs were high, DOs have decreased under the condition of stagnating for 7 days and increased after that time. On the contrary, at Gangchang bridge of which oxygen deficit was very high(7.11mg/l), DO have increased under the condition of stagnating for 13 days and decreased after that time. 5. All the samples showed the quick decrease of CODs and organic carbons under the condition of stagnating for 19 days. Nevertheless, at Sungpook bridge of which initial COD was very high (43.79㎎/ℓ), the value of COD measured at the last day of experiment was still high(21.35㎎/ℓ), because of a large quantity of reducing inorganic matters. 6. All the samples didn`t show the distinct decrease of turbidities because of a large quantity of nonbiodegradable inorganic solids.

A discrete state space model for a multiple-reach river system is formulated using the dynamics of biochemical oxygen demand(BOD) and dissolved oxygen(DO). A hierarchical optimization technique, which is applicable to large-scale systems with time-delays in states, is also described to control stream quality in a river as an optimal manner based on the interaction prediction method. The steady state tracking error of the proposed method is determined analytically and a necessary and sufficient condition on which a constant target tracking problem has zero steady-state error is derived. Computer simulations for the river pollution model illustrate the algorithm.

The COD values and chloride ion concentrations of the Taewha river flowing through Ulsan area were determined along the main stream and the relationships between CODs and chloride ion concentrations were described. The results showed that the middle-upper stream and downstream of the Taewha river were polluted deeply with municipal sewage and self-purification occured in the middle-downstream of the river. When domestic sewage is a main source of pollutants, and is especially the only source of chloride in the stream water, the ratio of COD/[Cl^-] will be utilizable as a measure of self-purification of the stream.