임진강 유역의 저수지 지리정보 구축과 수질평가 기초연구 = A Preliminary Study on Developing Geographic Information and Evaluating Water Quality of Reservoirs in Imjin River Watershed, South and North Korea

다국어 초록 (Multilingual Abstract)

The upper region of transboundary rivers is located in North Korea, and the construction and usage of the reservoirs from the north could have either a positive or negative impact on the South Korean reservoirs` water quantity, water quality, and ecological quality. Therefore, it is necessary for South Korea to grasp North Korea`s current status of water resources management and utilization to ensure its national water security. In this study, we sought to lay the groundwork for a reservoir management plan to prepare for potential inter-Korean economic cooperation and/or unification by establishing geographic information on small-and-medium sized reservoirs, which the country presently lacks, and estimating the water quality of the Iimjin watershed, which is the transboundary watershed between North and South Korea. Results of this study are as below; During the 1990s, North Korea expanded its agricultural lands by 12.6%, when compared to 1980s, by instituting nature-reorganization policies whose purpose was to increase grain outputs. In response to the enlargement of farmlands and completion of both the Seohae lock gate and Taecheon power plant, North Korea aggressively pursued the designation and expansion of irrigation facilities as national projects. As a result, large sized reservoirs, as well as small-and-medium sized reservoirs to facilitate irrigation in mountainous regions, were built. The number of reservoirs in North Korea is around 1,890, and their total volume stands at 3 billion ㎥. The total irrigation area of the reservoirs are approximately 4 billions ㎡. and over 66.5% of all reservoirs are located on the western coast of North Korea, including Cheongchun, Daedong, Yesung, Imjin river watersheds. It was found that more than over 60% of the pondage in Pyeongan-do and Hwanghaebuk-do are provided by high-capacity reservoirs. On the contrary, around 90% of the pondage which the inhabitants of Hamgyung-do and Kwangwon-do rely on are supplied by medium-and-small capacity reservoirs. The water resource potential of the Imjin watershed is abundant, but available precipitation considered as effective water resource is below 60% due to its topographic and geographic conditions. Therefore, it is presumed that small-sized reservoirs were built to compensate for the loss. Reservoir DB was built using satellite images, and in 2010, it estimated around 134 reservoirs sites around Gomitancheon(G.) watershed, which equated to approximately 31.5㎢ in total area and 1.2㎦ in total volume. Compared to the 1980s, 55 old reservoir sites are still in operation, 80 new reservoir sites have been built, and 2 reservoir sites have lost their utility. Around 83.7% of the pondage from new reservoirs are diverted to agricultural lands, 12.5% to forests, and 3.8% to grass lands. The two reservoirs which have lost their utility are presently used as agricultural land or bare ground. It is estimated that around G. watershed, 2 high-capacity reservoir sites (over 10㎥) constitute 1.5% of the total distribution rate, 59 medium-capacity reservoir sites (over 10㎥) constitute 44.0%, and 73 small-capacity reservoir sites (below 10㎥) constitute 54.5%. Small-capacity reservoirs are presumed to be the basic water supply of the Imjin watershed, and many small reservoir sites were built to meet the demand for water supply within the watershed. Using remote sensing, the surface temperature of Imjin watershed`s main reservoirs were estimated to be 22℃, which is suitable for algae growth and eutrophication. In lights of these findings, appropriate responses are required to manage the reservoirs. In particular, the surface temperature of Hwang River`s dam reservoir was estimated to 21.9℃ on 4th June 2010. As such, South Korea must prepare for the opening of the Hwagang dam by sanctioning additional investigations and continuous management efforts. To establish a water security system for the Korean Peninsula, information database should first be established before institutional strategies are planned. Due to the political and institutional situation in North Korea, access and sharing of information is limited. Nonetheless, South Korea should periodically obtain information and establish an information database on small and medium-sized reservoirs, as well as main water resources in transboundary watersheds, with continued interest, as they are highly vulnerable to water management. For the long-term, South Korea must maintain mutual confidence and cooperation with North Korea based on academic exchange. Furthermore, South Korea needs to identify North Korea`s present water resources management and utilization conditions through joint investigations and realtime/automatic monitoring. These measures could promote sustainable and stable usage of transboundary rivers.