Development of methodology for the characterisation of the long-term geosphere evolution, 2; Estimation of the long-term evolution of groundwater flow conditions in a Tono area case study

Kosaka, Hiroshi; Saegusa, Hiromitsu; Yasue, Kenichi; Kusano, Tomohiro; Onoe, Hironori 

The methodology for estimation of the long-term evolution of groundwater flow conditions are being developed using approaches on the basis of deductive and inductive methods in the case of Tono area. Based on the studies using the approach on the basis of deductive method, it has been confirmed that the method combining physical modeling of topographic change and groundwater flow simulations is useful for estimating of changes in groundwater flow conditions in the future due to topographic and climatic perturbations. Existing information for estimation of surface hydrological conditions, which are to be used for assignment of boundary conditions for the groundwater flow simulation, has been gathered from many sources and reviewed based on modern-analogue methods. In the studies using the approach on the basis of inductive method, paleo-hydrogeological studies have been carried out on several spatial and time scales. Through the study on the largest spatial scale, a methodology needed to understand changes of groundwater flow conditions due to long-term topographic change is proposed to efficiently identify the area to be carried out site characterization involving field investigations. And then, information to estimate the paleo-topography and paleo-climate has been obtained from literature surveys and field investigations. Through these studies, it has been confirmed that these two approaches are useful for estimation of the long-term evolution of deep groundwater flow conditions.