해안지역 지하수 수자원 통합관리방안 연구 Ⅱ

Abstract

Abstract An Integrated Management Plan for Groundwater Resources in the Coastal areas in Korea (II) Groundwater has not been appreciated as a major water resource during the last a few decades in Korea, as the government has afforded most of the public water supply from surface water resources such as rivers and reservoirs. However, a great percentage of the population have depended on ground water for their drinking water in costal areas, as the public water supply rate is only half of what it is in the metropolitan areas. Their water supply wells have been threatened by water level declines and saltwater intrusion. Sea level rise due to climate change also aggravates saltwater intrusion, which results in water shortages. Consequently public concern has been arisen and its specialized management system is required. Performed for two years(2007-2008), this study aims to provide policymakers, researchers, and stakeholders with a comprehensive and systematic management plan for groundwater resources in coastal areas and islands. The previous study described theory of saltwater intrusion, its modeling case studies, national groundwater monitoring networks, and groundwater management systems in developed countries. It also examined the confronting issues and suggested the policy recommendations. This report includes (1) influence of saltwater intrusion, (2) theory of submarine groundwater discharge(SGD) and its influence, (3) analysis of groundwater use, (4) estimation of available groundwater exploitation, (5) investigation of groundwater quality, (6) groundwater management in Korea and other countries, (7) techniques to prevent saltwater intrusion, and (8) an integrated groundwater management system. If the extent of saltwater intrusion would be increased by groundwater overexploitation, it might result in closing wells as well as increasing the chloride concentration of groundwater. It could also convert the freshwater ecosystem into saltwater ecosystem. The standard of chloride concentration is assigned by water supply regulations, in order to provide the appropriate water quality to the public. Its pressure on the plants and animals was also investigated, which has been employed as the criteria to preserve ecosystem. On the other hand, groundwater also flows from freshwater aquifer to the sea by hydraulic gradient, which is referred to as submarine groundwater discharge(SGD). Although several studies have reported that it could be one of major causes on marine pollution, its further investigation should be performed. Groundwater use and its determinants were analyzed for the southwestern area of Korea, however it could not be completed by discontinuity of data and information. While available groundwater resource in coastal areas was assessed in previous report, that of islands was done by pilot study in this report. Island in pilot study was designed with unfavorable conditions for groundwater development, based on the characteristics of fourteen islands in the southwestern coastal area. Nevertheless, its result showed that the amount of available groundwater resource is much greater than that produced by desalination system. If artificial recharge would be applied, the availability of groundwater resource could be increased with preventing its groundwater level declines. National groundwater monitoring networks have indicated that groundwater deterioration in agricultural area was more severe than others. According to the investigation of groundwater quality and contamination in Sumjin River Basin, chloride was derived from saltwater intrusion, while other pollutants such as nitrate and sulfur oxide were originated from human behavior. Groundwater managements in coastal areas and islands were compared. In Korea, if water supply and ecosystem would be threatened with saltwater intrusion, the Groundwater Act designated that groundwater exploitation should be prohibited, which has not been applied yet. The Ministry of Environment has performed the "Drinking Water Development Project for Residents in Islands", however its alternative measure is still requested by its expensive cost. In developed countries, a variety of technical methods have been employed to control saltwater intrusion under the governmental control and responsibility, such as proper allocation for supply well, artificial recharge, and groundwater dam. This study scrutinized the problems of the groundwater management and suggested their corresponding measures: organizing the essential elements of groundwater management and their relationships as well as designating the bounds of specialized groundwater management in coastal area based on the groundwater quality data, administrative district, and watershed. It also encouraged the cooperation between policymakers, scientists, and engineers, and emphasized the research of potential issues like sea level rise by climate change. These could be the main tasks to accomplish the integrated management plan for groundwater resources in coastal areas, which should contribute to provide proper water supply and to preserve ecosystem.