Science Links Japan | Formation and Movement of Freshwater-saltwater Transition Zone through Geologic Time. (No.1). Numerical Case Studies under Static Boundary Conditions.

Formation and Movement of Freshwater-saltwater Transition Zone through Geologic Time. (No.1). Numerical Case Studies under Static Boundary Conditions.

Accession number;03A0033930

Title;Formation and Movement of Freshwater-saltwater Transition Zone through Geologic Time. (No.1). Numerical Case Studies under Static Boundary Conditions.

Author; TOSAKA HIROYUKI (Univ. Tokyo, Graduate School of Engineering, JPN)

Journal Title;Journal of the Japan Society of Engineering Geology

Journal Code:G0269B

ISSN:0286-7737

VOL.43;NO.5;PAGE.293-305(2002)

Figure&Table&Reference;FIG.9, TBL.2, REF.28

Pub. Country;Japan

Language;Japanese

Abstract;For giving basic understandings of the long-term safety of geologic isolation of high level radioactive wastes in a coastal deep subsurface region, behavior of the Freshwater-Saltwater Transition Zone(FSTZ), which might be a key fac-tor in estimating and predicting the coastal groundwater flow field, is examined through numerical case studies. The author presents, in the sequential two papers, the results of 2-D cross-sectional model studies under static/dynamic boundary conditions. In this paper, the numerical results under static boundary conditions are presented. They can be summarized as fol-lows. (a) Under the same boundary conditions, two different processes, i.e., a washing-out process starting from saltwater saturated condition and a saltwater intrusion process starting from saltwater/freshwater separated condition, produce almost the same shape of FSTZ at steady state. (b) The lower the regional permeability becomes, the longer the time required for attaining equilibrium of FSTZ be-comes. (c) Push-out of FSTZ to sea side by freshwater may occur when the rate of infiltration is high, and/or rock anisotropy is high, and/or the topographic high exists. (d) Existence of a fault with relatively lower permeability than the peripheral rock may have greater effect on the position and shape of FSTZ, than that with higher permeability. (author abst.)

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