유역관리를 통한 다목적댐 저수지의 효율적인 탁수관리방안

Abstract

Recently, turbidity problems occurring in many multipurpose dams are being regarded as a serious problem in Korea. This problem has amplified since several typhoons have seriously hit our land; Rusa in 2002, Maemi in 2003, and Dianmu in 2004. Turbidity that exceeds a certain level precipitates aesthetic problems, drops value as a water resource, and gives bad influences to the waterbodies and surrounding ecosystem. In these situations, it is very urgent to look for the fundamental causes of long term effects of turbidity in multipurpose dams, and to also get measures about for such problems. Fortunately, the Korea Water Resources Corporation has been executing a basic investigation about turbidity as a main shaft work for many years, measuring to solve the problems reviewed at governmental dimensions. These measures can be categorized into "measures in a lake", "downstream measures" and "measures through watershed management". The first and the second correspond to "measures after influx" and the last one includes "measures before influx". A preventive technique through watershed management is deemed the most effective measure when taking into consideration in both water quality and quantity management aspects as well as non-point sources. Therefore, this study focuses on "measures before influx" and tries to propose an efficient management system for turbidity control. As a model for the study, we chose Im-Ha dam, which has been the most seriously influenced by turbidity and the So-yang dam, where turbidity is increasingly becoming a problem because of its long detention time. Chapter 2 deals with governmental measures which solve the turbidity problems in multipurpose dams, focusing on the Im-ha and So-yang dam and analyzing the related causes and effects. The main causes of soil erosion arise from non-point source such as arable land, developing sites, city areas etc. As a result, it was established that unique characteristics of a watershed such as its geological feature, topography and weather are the major causes in the turbidity problem. To make matters worst, artificial characteristics like construction work and farming also contribute to the existing problems. Especially, after reviewing the existing investigation, we found that alpine areas were also serious cause of erosion. Chapter 3 describes the methods and system adopted in various countries to control turbidity. The study tries to derive implications which can be introduced into Korea. In the case of Japan, "measures before influx" cannot be brought to attention just yet; rather the "measures after influx" are mainly adopted. It was demonstrated that in the case of the United States, related regulations on soil erosion mainly examined turbidity measures of individual lakes, rather than managing erosion as a part non-point source and executing measures for each state specifically. Chapter 4 presents concrete measures to reduce turbidity. Here, we divide a measure into 3 parts - "measures through watershed management", "technical measures for soil stabilization", and "system improvement measures". Finally in chapter 5, we propose concrete policy measures for to control the turbidity problem. Once a turbidity problem occurs in a multipurpose dam, its management becomes very difficult. Therefore, turbidity management must focus on "measures before influx". For this, we must approach to the problem with both "upstream management" and "system improvement". When efficient watershed management based on improvement system is preceded, we can ultimately solve the turbidity problem without wasting unnecessary monetary measures.