Study on the effects of long-term evolution of geological environment on groundwater flow (Contract research)

Evaluation of long-term geological evolution and its impact on groundwater flow is one of the critical issues in order to enhance credibility of long-term behavior estimation of geological disposal system. For the purpose of development of a groundwater flow modeling methodology considering the effects of long-term geological evolution, following three items were studied: a) Upgrade of SMS (Sequential Modeling System of geo-environmental evolution impact on groundwater flow) which was developed in 2006 FY; b) Groundwater flow simulation under more realistic conditions of geological structures and hydrogeological conditions; and c) Sensitivity study of geo-environmental evolution impacts on groundwater flow. The studies showed following suggestive results. a) Development of a precise time step setting enabled to narrow the gaps in simulated head between time steps in which the model configuration used to deformed. b) Several aspects have been found from studies on impact factors such as deposition on pore pressure, recharge rate and difference in density of saline groundwater. For evaluation of pore pressure induced by deposition, it is necessary to model the porosity and permeability variation considered the excess pore pressure change. The set of recharge rate during the glacial age impacts the characteristics of groundwater flow in coastal and hilly areas. The density of groundwater is not so influential as topological potential factors, however it is effective for the characteristics of groundwater flow in coastal area and prevents intrusion of recharge from ground surface. c) The sensitivity study on faulting characteristics indicated that the two types of fault configuration and the hydraulic conductivity setting considered are not influential on the nature of groundwater flow above the depth of 500m. (author)