Journal of the Korean Association of Geographic Information Studies (한국지리정보학회지)

The Korean Association of Geographic Information Studies (한국지리정보학회)
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Analysis of National Stream Drying Phenomena using DrySAT-WFT Model: Focusing on Inflow of Dam and Weir Watersheds in 5 River Basins

DrySAT-WFT 모형을 활용한 전국 하천건천화 분석: 전국 5대강 댐·보 유역의 유입량을 중심으로

  • LEE, Yong-Gwan (Dept. of Civil, Environmental and Plant Engineering, Graduate School, Konkuk University) ;
  • JUNG, Chung-Gil (Forcast and Control Division, Yeongsan River Flood Control Office) ;
  • KIM, Won-Jin (Dept. of Civil, Environmental and Plant Engineering, Graduate School, Konkuk University) ;
  • KIM, Seong-Joon (School of Civil and Environmental Engineering, Konkuk University)
  • 이용관 (건국대학교 대학원 사회환경플랜트공학과) ;
  • 정충길 (영산강홍수통제소 예보통제과) ;
  • 김원진 (건국대학교 대학원 사회환경플랜트공학과) ;
  • 김성준 (건국대학교 사회환경공학부)
  • Received : 2020.04.25
  • Accepted : 2020.06.02
  • Published : 2020.06.30
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Abstract

The increase of the impermeable area due to industrialization and urban development distorts the hydrological circulation system and cause serious stream drying phenomena. In order to manage this, it is necessary to develop a technology for impact assessment of stream drying phenomena, which enables quantitative evaluation and prediction. In this study, the cause of streamflow reduction was assessed for dam and weir watersheds in the five major river basins of South Korea by using distributed hydrological model DrySAT-WFT (Drying Stream Assessment Tool and Water Flow Tracking) and GIS time series data. For the modeling, the 5 influencing factors of stream drying phenomena (soil erosion, forest growth, road-river disconnection, groundwater use, urban development) were selected and prepared as GIS-based time series spatial data from 1976 to 2015. The DrySAT-WFT was calibrated and validated from 2005 to 2015 at 8 multipurpose dam watershed (Chungju, Soyang, Andong, Imha, Hapcheon, Seomjin river, Juam, and Yongdam) and 4 gauging stations (Osucheon, Mihocheon, Maruek, and Chogang) respectively. The calibration results showed that the coefficient of determination (R2) was 0.76 in average (0.66 to 0.84) and the Nash-Sutcliffe model efficiency was 0.62 in average (0.52 to 0.72). Based on the 2010s (2006~2015) weather condition for the whole period, the streamflow impact was estimated by applying GIS data for each decade (1980s: 1976~1985, 1990s: 1986~1995, 2000s: 1996~2005, 2010s: 2006~2015). The results showed that the 2010s averaged-wet streamflow (Q95) showed decrease of 4.1~6.3%, the 2010s averaged-normal streamflow (Q185) showed decreased of 6.7~9.1% and the 2010s averaged-drought streamflow (Q355) showed decrease of 8.4~10.4% compared to 1980s streamflows respectively on the whole. During 1975~2015, the increase of groundwater use covered 40.5% contribution and the next was forest growth with 29.0% contribution among the 5 influencing factors.

산업화와 도시개발로 인한 불투수층 면적의 증가는 수문순환 체계를 왜곡시켜 심각한 건천화를 야기한다. 이를 관리하기 위해 건천화의 정량적인 평가 및 예측이 가능한 하천건천화 영향평가 기술이 필요하다. 본 연구에서는 분포형 수문모형(Drying Stream Assessment Tool and Water Flow Tracking, DrySAT-WFT)과 시계열 GIS자료를 활용하여 전국 5대강 유역의 댐·보 유역을 대상으로 하천유입량 감소원인 평가를 실시하였다. 이를 위해 5개 하천건천화 영향요소(토양침식, 산림성장, 도로-하천 단절, 지하수이용, 도시개발)를 선정하여 1976년부터 2015년까지 GIS 기반의 시계열 공간자료를 연대별로 구축하였다. DrySAT-WFT는 2005~2015년까지 8개의 다목적댐(충주댐, 소양강댐, 안동댐, 임하댐, 합천댐, 섬진강댐, 주암댐, 용담댐) 및 4개의 유량 관측지점(오수천, 미호천, 마륵, 초강)에 대해 하천유량 검보정을 실시하였고, 검보정 결과 결정계수(R2)는 평균 0.76(0.66~0.84), Nash-Sutcliffe 모형효율은 평균 0.62(0.52~0.72)의 값을 보였다. 이를 토대로 2010년대(2006~2015)의 기상조건을 기준으로 연대별(1980년대: 1976~1985, 1990년대: 1986~1995, 2000년대: 1996~2005, 2010년대: 2006~2015) GIS자료를 이용하여 댐·보 유역의 하천유입량 변화를 계산하므로서 각 영향요소별 하천유입량 감소 기여비율을 산정하였다. 모의결과, 1980년대를 기준으로 5대강 유역평균 2010년대 풍수량(Q95)은 4.1~6.3%의 감소율을 보였고, 평수량(Q185)은 6.7~9.1%의 감소율을 보였으며, 갈수량(Q355)은 8.4~10.4%의 감소율을 보였다. 하천건천화 영향요소 중에서 지하수 이용량의 증가로 인한 기저유량 감소(하천건천화 기여율: 40.5%)가 가장 큰 영향을 주었으며, 다음으로는 산림성장에 의한 증발산량 증가(하천건천화 기여율: 29.0%)로 나타났다.

Keywords

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