2015 Volume 28 Issue 3 Pages 109-123
This study was conducted to reproduce long-term groundwater flow in Musashino Terrace using a numerical model and to clarify the relation between long-term groundwater flow change and land use change. The model used for this study is MODFLOW developed by the United States Geological Survey (USGS), which is the threedimensional groundwater flow model that uses the finite difference method. The simulation was conducted for 1976-2012 when land use data were available. We computed daily groundwater level for the period. Moreover, we analyzed the projected groundwater flow during 2013-2050, with meteorological data calculated using global climate models of four types. Groundwater variation and seasonal change that were caused mainly by rainfall were reproduced. We also calculated the decrease of the groundwater level and recharge area around some observation wells.
The Mann-Kendall rank statistic was used for detecting groundwater flow trends. Results clarified the relation between the decrease of recharge area and groundwater level. That relation was affected by the decrease of permeable areas such as paddy fields, agricultural areas, and woodlands, and by the increase of impermeable areas such as building sites during 1977-2012. Future groundwater flow was also estimated, which clarified that the groundwater level can be expected to rise by the increase of moderately intense precipitation in the future if land use remains as it is.