Chonan and Asan city have been a focal point due to rapid development as the first station for Express Railroad and key cities West Coast Development Region. Gokgyo stream adjacent to the cities plays an important role as a drainage channel for an agriculture and a discharger of urban storm water. Water quality of the stream has been deteriorating caused by pollution sources such as a untreated wastewater discharge and runoff from the watershed. In this study, we conducted 4 surveys in April, May, July, and September to understand the current state of water quality for the stream and to make it possibe to predict future water-quality variation for future development. The system runs on a personal computer under the windows enviroment and provides extensive graphics using graphic user interface(GUI) for user-friendly assessment. Using the pull-down menus provided by the GUI panel, the user is able to operate the system by pointing and clicking the icon to identify the state of water-quality at locations concerned. Furthermore, we developed an integrated watershed management system. The constructed system could be a useful tool as a decesion maker for pollution source control strategy.

In order to manage the water quality from the flowing streams in Cheju Island, the characteristics of water quality was investigated from August, 1996 to May, 1997 and the pollutant loadings for future were estimated from the watershed at each stream. Comparing the mean concentrations of each water quality with the criterion of water quality in river, it was under I class except for Changgo Stream, for DO, under I class at the whole station for SS and under Ⅱ class for BOD. As the pollutant loadings at each stream in 2020 is compared with those in 1996, the estimated results are as follows : 1) for BOD, 59% at Donghong Stream, 24% at Yeonoe Stream, 44% at Ohngpo Stream and 57% at Changgo Stream. 2) for T-N, 91% at Donghong Stream, 76% at Yeonoe Stream, 63% at Ohngpo Stream and 89% at Changgo Stream. 3) for T-P, 69% at Donghong Stream, 42% at Yeonoe Stream, 45% at Ohngpo Stream and 73% at Changgo Stream The point source loadings discharged through combined sewer could be treated at sewage treatment plant. However, the expected slow decreasing rate of BOD, T-N, and T-P loadings is due to the part of untreated nonpoint source loadings. Nonpoint source loading overflow typically occurs when the flow of stormwater combined with sewage exceeds the capacity of the interceptor sewers. Since most of the sewers used in Cheju Island are the combined sewers, the combined overflow sewage is bypassed into the receiving water area after a rainstorm. Therefore, a means to control nonpoint source loadings should be considered for the river and marine water quality management.

Environmental problems caused by certain geologic conditions include pollution of soil by heavy metal, acidization of soils, acid mine drainage, ground-water pollution, and natural radioactivity, as well as geological hazards such as landslide and subsidence. The acid mine drainage contains large amount of heavy metals and, therefore, cause serious pollution onto the nearby drainage systems and soils. In spite of this prospective environmental danger, few studies have been done on the acid mine drainage derived from non-metallic ore deposits such as pyrophyllite(Napseok) deposits. The sulfide-bearing pyrophyllite ores, alteration zones, and mine tailings of pyrophyllite deposits produce acid mine drainage by the oxidation of weathering. Compared to the fresh host rocks, the ores and altered rocks of pyrophyllite deposits produce acidic solution which contain higher amount of heavy metals because of their lower buffering capacity to acid solution. The pHs of mine water and nearby stream water of pyrophyllite deposits are 2.1∼3.7, which are strongly acidic and much lower than that (6.2∼7.2) of upstream water and than that (6.8∼7.6) of the stream water derived from the non-mineralized area. This study reveals that this acid mine drainage can affect the downstream area which is 8km far from the pyrophyllite deposits, even though the drainage is diluted with abundant non-contaminated river water. This suggests that not only acid mine drainage but also the sulfide-bearing sediments originated from the pyrophyllite deposits move downstream and form acidic water through continuous oxidation reaction. The heavy metals such as Pb, Zn, Cu, Cd, Ni, Mn and Fe are enriched in the mine water of low pH, and their contents decrease as the pH of mine water increases because of the influx of fresh stream water. Soils of the pyrophyllite deposits are characterized by high contents of heavy metals. The stream sediments containing the yellowish brown precipitates formed by neutralization of acid mine drainage occur in all parts of the stream derived from the pyrophyllite deposits, and the sediments also contain high amounts of heavy metals. In summary, the acid mine drainage of the pyrophyllite deposits is located in the upstream part of Hoidong water reservoir in Pusan contains large amounts of heavy metals and flows into the Hoidong water reservoir without any purification process. To protect the water of Hoidong reservoir, the acid mine drainage should be treated with a proper purification process.

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.

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.

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.