Estimate of long-term change of groundwater flow characteristic by topography change and climate change; In Tono area

Kusano, Tomohiro; Yasue, Kenichi; Kosaka, Hiroshi; Saegusa, Hiromitsu; Takeuchi, Ryuji  ; Onoe, Hironori* ; Shiomi, Tetsuya*; Tajikara, Masayoshi*

In this study, we focused on long-term topography change due to uplift, denudation and climate change with ice age and interglacial cycles of natural phenomena, to estimate influence to groundwater flow characteristics, we estimated paleo-topography and paleo-climate and operated groundwater flow simulation in Tono area. Based on terrace area distribution scattered along river, we estimated paleo-topography in three dimensions with DEM data and GIS. we estimated climate of glacial and interglacial age by near-surface hydrological observation data, pollen fossil analysis and expenditure calculation based on them. In hydraulics geological structure model with paleo-topography, we operated groundwater flow simulation on three-dimensional saturation and unsaturation in steady state. It is thought less effect on groundwater flow characteristics change in current terrain from middle terrace area formation. It is important to evaluate influence of groundwater flow characteristics if that form mountains or hills. Change in groundwater flow characteristics with change of recharge rate is limited to high-altitude area compared to ramifications of the mountains.