장·단기 유출 모형을 이용한 대청댐 유역의 수문특성 분석

Abstract

An accurate and efficient hydrologic forecasting is needed for water resources development and optimum water resources management. The long-and short-term runoff data is very important to determine the storage capacity of hydrologic structures and for efficient management of water use. Generally a daily long-term rainfall model for irrigation and an hourly short-term rainfall model for flood control are used separately. There it is needed to use a combined model for rainfall-runoff analysis The purpose of this study was to evaluate the changes of long-term and short-term runoff characteristics of a large river basin due to construction of a large multipurpose dam using NWS-PC Model, which was simulated with rainfall data, evapotranspiration data and phisiographic data. The phisiographic parameters of the model are obtained from the established GIS database and some parameters to account for the hydrologic variation are quantified from remote sensing film taken before and after reservoir construction. Rain and observed runoff data of the year, 1975, were used to calibrate the model. After having calibrated the model by trial and error method, runoff characteristics of 10 years before and after dam construction were simulated. The sensitive analysis of major parameters used in the model is conducted and from the result of this analysis, LZTWM is the most sensitive to total runoff in long-term rainfall-runoff simulation and LZFSM is the most sensitive to peak runoff in short-term rainfall-runoff simulation. From the simulation results, the relative error of calculated discharge to observed discharge was found to be within approximately 10%. Therefore, the model was considered to be adaptable in this study, and the changes in long-term runoff characteristics were evaluated based on the runoff computations. Based on the analysis of before and after the construction of the dam, peak flow in Gongju has been found to decrease 772cms in 1984, and 4,166cms in 1995, and in Gyuam 477cms in 1984, and 3,442cms. In addition, analysis results for estimation probability flood have shown that the amount of flood has decreased by 11∼15% in Gongju, and 10% in Gyuam. In conclusion, it was found that runoff ratio of watershed upstream of the reservoir is slightly increasing due to the hydrologic variation, and the flood peak flows decrease due to storage effect of the reservoir, whereas, low flows are, on the average, increased due to regulated outflow releases from the reservoir.