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A study on determining threshold level of precipitation for drought management in the dam basin

댐 유역 가뭄 관리를 위한 강수량 임계수준 결정에 관한 연구

  • 이경도 (주식회사 헥코리아) ;
  • 손경환 (환경부 한강홍수통제소 수자원정보센터) ;
  • 이병주 (주식회사 헥코리아)
  • Received : 2020.03.05
  • Accepted : 2020.03.23
  • Published : 2020.04.30

Abstract

This study determined appropriate threshold level (cumulative period and percentage) of precipitation for drought management in dam basin. The 5 dam basins were selected, the daily dam storage level and daily precipitation data were collected. MAP (Mean Areal Precipitation was calculated by using Thiessen polygon method, and MAP were converted to accumulated values for 6 cumulative periods (30-, 60-, 90-, 180-, 270-, and 360-day). The correlation coefficient and ratio of variation coefficient between storage level and MAP for 6 cumulative periods were used to determine the appropriate cumulative period. Correlation of cumulative precipitation below 90-day was low, and that of 270-day was high. Correlation was high when the past precipitation during the flood period was included within the cumulative period. The ratio of variation coefficient was higher for the shorter cumulative period and lower for the longer in all dam, and that of 270-day precipitation was closed to 1.0 in every month. ROC (Receiver Operating Characteristics) analysis with TLWSA (Threshold Line of Water Supply Adjustment) was used to determine the percentage of precipitation shortages. It is showed that the percentage of 270-day cumulative precipitation on Boryung dam and other 4-dam were less than 90% and 80% as threshold level respectively, when the storage was below the attention level. The relationship between storage and percentage of dam outflow and precipitation were analyzed to evaluate the impact of artificial dam operations on drought analysis, and the magnitude of dam outflow caused uncertainty in the analysis between precipitation and storage data. It is concluded that threshold level should be considered for dam drought analysis using based on precipitation.

본 연구에서는 댐 유역의 가뭄 관리를 위한 강수량의 적정 임계수준을 결정하였다. 5개 댐 유역(보령댐, 부안댐, 대청댐, 합천댐 및 용담댐)을 대상으로 일단위 저수량 및 강수량 자료를 수집하였고, 유역평균강수량을 계산하였다. 6개 누적기간(30, 60, 90, 180, 270 및 360일)의 값으로 변환하였고, 일 단위 저수량 및 누적강수량의 예년대비 백분율을 계산하였다. 강수량의 적정 누적기간 결정을 위해 상관성 및 변동성을 분석하였다. 모든 댐에서 90일 이하의 누적 강수량은 댐 홍수기를 제외하고는 상관성이 낮았고, 270일 누적 강수량의 상관성은 높았다. 누적기간 중에 댐 홍수기 강수량 값의 포함여부가 상관성에 큰 영향을 미친 것으로 확인되었다. 변동계수 비율은 누적기간이 짧을수록 비율이 크고 길수록 적었으며, 270일이 모든 월에서 1에 근접하였다. 댐 용수공급 조정기준을 이용한 ROC 분석을 통해 보령댐은 저수량이 관심단계 이하일 때 강수량의 임계수준6은 270일 누적강수량의 백분율이 90% 이하, 4개 댐은 80% 이하로 나타났다. 인위적인 댐 운영이 가뭄분석에 미치는 영향을 분석하고자 강수량 백분율, 저수량 및 방류량 백분율의 거동을 분석하였다. 댐 방류량 조건은 강수량 및 저수량간의 연계분석에 불확실성을 야기하였다. 따라서 강수량을 활용한 댐 가뭄 분석을 위해서는 대상 댐유역에 대한 적정 임계수준 및 방류량 조건이 검토되어야 할 것이다.

Keywords

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