Journal of Korea Water Resources Association (한국수자원학회논문집)

Korea Water Resources Association (한국수자원학회)
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Evaluation of stream flow and water quality behavior by weir operation in Nakdong river basin using SWAT

SWAT을 이용한 낙동강유역의 보 개방에 따른 하천유량 및 수질 거동 분석

  • Lee, Ji Wan (Graduate School of Civil, Environmental and Plant Engineering, Konkuk University) ;
  • Jung, Chung Gil (Agricultural and Water Resources Engineering, Texas A&M AgriLife Research Center at El Paso) ;
  • Woo, So Young (Graduate School of Civil, Environmental and Plant Engineering, Konkuk University) ;
  • Kim, Seong Joon (School of Civil and Environmental Engineering, Konkuk University)
  • 이지완 (건국대학교 대학원 사회환경플랜트공학과) ;
  • 정충길 ;
  • 우소영 (건국대학교 대학원 사회환경플랜트공학과) ;
  • 김성준 (건국대학교 공과대학 사회환경공학부)
  • Received : 2019.03.05
  • Accepted : 2019.04.10
  • Published : 2019.05.31
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Abstract

The purpose of this study is to evaluate the stream flow and water quality (SS, T-N, and T-P) behavior of Nakdong river basin ($23,609.3km^2$) by simulating the dam and weir operation scenarios using SWAT (Soil and Water Assessment Tool). The operation senarios are the simultaneous release for all dam and weirs (scenario 1), simultaneous release for all weirs (scenario 2), and sequential release for the weirs with one month interval from upstream weirs (scenario 3). Before evaluation, the SWAT was calibrated and validated using 11 years (2005-2015) daily multi-purpose dam inflow at 5 locations (ADD, IHD, HCD, MKD, and MYD), multi-function weir inflow at 7 locations (SHW, GMW, CGW, GJW, DSW, HCW, and HAW), and monthly water quality monitoring data at 6 locations (AD-4, SJ-2, EG, HC, MK-4, and MG). For the two dam inflow and dam storage, the Nash-Sutcliffe efficiency (NSE) was 0.56~0.79, and the coefficient of determination ($R^2$) was 0.68~0.90. For water quality, the $R^2$ of SS, T-N, and T-P was 0.64~0.79, 0.51~0.74, and 0.53~0.72 respectively. For the three scenarios of dam and weir release combination suggested by the ministry of environment, the scenario 1 and 3 operations were improved the stream water quality (for T-N and T-P) within the 3 months since the time of release, but it showed the negative effect for 3 months after compared to scenario 2.

본 연구의 목적은 낙동강유역($23,609.3km^2$) 내 댐-보 연계운영 평가를 위해 SWAT (Soil and Water Assessment Tool)을 이용하여 댐보 운영 시나리오에 따른 하천 유량 수질 거동을 평가하는 것이다. 댐-보 방류시나리오는 댐-보 동시방류(시나리오 1), 보 동시방류(시나리오 2), 상류 보에서부터 1개월 간격의 순차방류(시나리오 3)로 모의되었다. 평가에 앞서 SWAT은 11년(2005-2015) 동안 5개의 다목적댐(안동댐, 임하댐, 합천댐, 남감댐, 밀양댐)과 7개의 다기능보(상주보, 구미보, 칠곡보, 강정보, 달성보, 합천보, 함안보) 및 6개의 수질관측지점(안동4, 상주2, 왜관, 합천, 남강, 물금)에 대하여 검보정 되었다. 유입량 및 저수량 검 보정결과 $R^2$는 0.68~0.90, NSE는 0.56~0.79, RMSE는 0.94~1.74 mm/day 였으며, PBIAS는 -7.52~18.08%로 분석되었고,. 수질 $R^2$는 SS는 0.64~0.79, T-N는 0.51~0.74, T-P는 0.53~0.72의 상관성을 나타었다. 댐-보 연계운영 평가를 위해 환경부에서 제시한 연계운영 시나리오 중 3개의 시나리오를 선택하여 모의하였으며, 시나리오에 따른 수문 수질 거동을 분석하였다. 분석결과 시나리오 2 에 비해 시나리오 1과 3은 연계운영 종료 이후 3개월 이전에는 수질 (T-N, T-P)개선 효과가 나타났지만, 3개월 이후로는 시나리오 2에 비해 수질이 나빠진 것으로 나타났다.

Keywords

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Fig. 1. Study watershed and monitoring stations

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Fig. 2. GIS data of the Nakdong River Basins (a) DEM, (b) Soil properties, and (c) land cover

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Fig. 3. Flowchart of this study

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Fig. 4. The calibration and verification results for dam/weir inflow (mm) and storage (106m3)

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Fig. 5. The calibration and verification results for water quality (SS, T-N, T-P)

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Fig. 6. The streamflow and water quality behavior in 2017

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Fig. 7. Monthly change of streamflow and water quality

Table 1. A method of operation of dam-weir-reservoir system (Ministry of Environment, 2017)

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Table 2. The calibrated parameters for SWAT model

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Table 3. Calibration and validation results for dam inflow at 10 and water quality at 6 calibration point

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