Hydrological Feasibility for Heightening Dae-ah Reservoir

대아지 숭상을 위한 수문학적 가능성 평가

The objective of this study is to evaluate the hydrological feasibility of heightening the Dae-ah reservoir in order to save instream flow at the Bong-dong station situated in the Mankyoung river. The results are summarized as follows. Firstly, from the Dong-sang and Dae-ah cascaded reservoir's water balance analysis, water supply indexes of the Dae-ah reservoir were analyzed to have the rate of water supply divided by watershed area of 1207.4 mm, the rate of water supply divided by rainfall of 95.8%, the rate of water supply divided by inflow of 153.1%, the rate of water supply divided by storage capacity of 236.1%, and the rate of inflow divided by storage capacity of 200.6%. Secondly, from the Dae-ah and Kyoung-cheon paralleled reservoir's water balance analysis, flow durations at the Bong-dong station were analyzed to have the Q95 (the 95th high flow) of $28.95m^3/s$, the Q185 (the 185th high flow) of $2.00m^3/s$, the Q275 (the 275th high flow) of $2.00m^3/s$, and the Q355 (the 355th high flow) of $0.82m^3/s$. Thirdly, in case of heightening the full water level of the Dae-ah reservoir of 10m, from the Dong-sang and Dae-ah cascaded reservoir's water balance analysis, water supply indexes of the Dae-ah reservoir were analyzed to have the rate of water supply divided by watershed area of 1220.7 mm, the rate of water supply divided by rainfall of 96.8%, the rate of water supply divided by inflow of 154.6%, the rate of water supply divided by storage capacity of 160.0%, and the rate of inflow divided by storage capacity of 137.0%. Fourthly, in case of heightening the full water level of the Dae-ah reservoir of 10m, from the Dae-ah and Kyoung-cheon paralleled reservoir's water balance analysis, flow durations at the Bong-dong station were analyzed to have the Q95 of $28.09m^3/s$, the Q185 of $1.79m^3/s$, the Q275 of $1.79m^3/s$, and the Q355 of $0.82m^3/s$. The conclusion appeared not to have the hydrological feasibility of heightening the Dae-ah reservoir from the reason that increased storage capacity does not increase water supply amount any more because of the high rate of the water supply divided by inflow.

만경강 수계의 봉동 지점에서 자연사회환경개선의 하천유지유량을 확보하기 위해 상류에 위치한 대아저수지를 높이는 방안에 대한 수문학적 타당성을 검토한 결과 다음과 같이 요약된다. 첫째, 동상-대아 직렬 연계에 의해 대아저수지로부터의 용수공급을 분석한 결과 용수공급량/유역면적은 1207.4 mm, 단위유역 용수공급량/강우량 비율은 95.8%, 용수공급량/유입량 비율은 153.1%, 용수공급량/저수량 비율은 236.1%, 유입량/저수량 비율은 200.6%였다. 둘째, 대아-경천 병렬 연계를 고려한 봉동 지점의 유량을 분석한 결과 유황은 연평균하여 풍수량 $28.95m^3/s$, 평수량 $2.00m^3/s$, 저수량 $0.95m^3/s$, 갈수량 $0.82m^3/s$로 분석되었으며, 고시유량 $1.32m^3/s$보다 $0.50m^3/s$ 적게 나타났다. 셋째, 대아저수지를 10m 높인 경우 대아저수지로부터의 용수공급을 분석한 결과 용수공급량/유역면적은 1220.7 mm, 단위유역 용수공급량/강우량 비율은 96.8%, 용수공급량/유입량 비율은 154.6%, 용수공급량/저수량 비율은 163.0%, 유입량/저수량 비율은 137.0%였다. 넷째, 대아저수지를 10m 높인 경우 대아-경천 병렬 연계를 고려한 봉동 지점의 유량을 분석한 결과 유황은 연평균하여 풍수량 $28.09m^3/s$, 평수량 $1.79m^3/s$, 저수량 $0.89m^3/s$, 갈수량 $0.82m^3/s$로 분석되어 유량증가 효과는 전혀 나타나지 않았다. 요약하면 대아저수지 용량을 증가시키더라도 용수공급의 증가효과는 전혀 나타나지 않았으며, 봉동지점의 고시유량을 확보하기 위한 대아 저수지의 숭상의 수문학적 타당성은 전혀 없는 것으로 분석되었다.