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2026 Vol.31, Issue 5 Preview Page

Research Paper

Model Fit Does Not Ensure Recharge Identifiability: Watershed and Coastal-Boundary Diagnostics with Methodological Implications for High-Level Radioactive Waste Disposal Safety Assessment

지하수 함양량 추정에서 모델 적합도와 식별성의 불일치: 유역∙해안 경계 수치진단과 고준위방사성폐기물 처분 안전성평가에 대한 방법론적 시사점

Eungyu Park12
,
Byung-Gon Chae3
,
Jangwon Park12
,
Taeyu Kim12
,
Heejun Suk4*
박 은규12
,
채 병곤3
,
박 장원12
,
김 태유12
,
석 희준4*
1Department of Geology, Kyungpook National University, 80 Daehak-ro, Buk-gu, Daegu 41566, Republic of Korea
2GeoAI Alignment, Inc., Rm. 101-1, 58 Daehyeon-ro 9, Buk-gu, Daegu 41566, Republic of Korea
3Deep Geological Disposal and Energy Storage Research Center, Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon 34132, Republic of Korea
4Groundwater Resources Research Center, Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon 34132, Republic of Korea
1경북대학교 지질학과
2(주)지오에이아이얼라인먼트
3한국지질자원연구원 방폐물심층처분연구센터
4한국지질자원연구원 지하수자원연구센터
*Corresponding Author
31 October 2026. pp. 43-62
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Abstract

Groundwater recharge sets the upper boundary flux that controls hydraulic heads, flow paths, travel times, and geochemical conditions in safety assessment of high-level radioactive waste disposal. Whether a calibrated model identifies that flux is a different question from how well it reproduces its calibration target. We examined this separation in three controlled numerical diagnostics rather than at a disposal site. Across nine SWAT+ parameterizations of a diagnostic test-bed watershed, mean annual basin soil-profile percolation ranged from 58.2 to 390.0 mm/yr while mean flow at the analysed channel stayed within 15.626–16.275 m3/s; four low- and intermediate-percolation cases retained Kling-Gupta efficiency 0.969–0.978 and Nash-Sutcliffe efficiency 0.992–0.996 against a synthetic baseline hydrograph. In an idealized one-layer coastal model, three combinations of hydraulic conductivity (7.5–14 m/day), general-head-boundary conductance (5–80 m2/day), and net distributed source-sink budget (363–2,798 m3/day) reproduced one prescribed head field within a root-mean-square error of 2.6 × 10-7 m. Adding 29 or 87 m3/day of coastal discharge with equal co-located supply left the simulated heads unchanged. Fit therefore constrains the calibration target, not the internal flux. Recharge entering a safety assessment should be constrained by an independent process observation that resolves the specific non-uniqueness, and propagated as a bounded range.

Keywords
Coastal boundary
Groundwater recharge
Model identifiability
Non-uniqueness
Radioactive waste disposal
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Information
  • Publisher :The Korean Society of Soil and Groundwater Environment
  • Publisher(Ko) :한국지하수토양환경학회
  • Journal Title :Journal of Soil and Groundwater Environment
  • Journal Title(Ko) :지하수토양환경
  • Volume : 31
  • No :5
  • Pages :43-62
  • Received Date : 2026-07-27
  • Revised Date : 2026-09-17
  • Accepted Date : 2026-10-07
  • DOI :https://doi.org/10.7857/JSGE.2026.31.5.043
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