Estimation of groundwater recharge rate and spatial distribution of hydrological quantities in surface hydrogeological investigation basin of Horonobe URL Project; From December 2004 to November 2009

Yamamoto, Yoichi; Maekawa, Keisuke  ; Yokota, Hideharu; Yamazaki, Masanori

The surface hydrogeological investigation has been carried out in and around the Horonobe Underground Research Laboratory area as a part of Horonobe URL project. Observations of meteorological, river flux, water quality, soil moisture and groundwater level have been continued in order to understand the groundwater recharge rate and groundwater flow in the shallow part, which are required for the setting of boundary and initial condition of the groundwater flow analysis. This report shows the summary of the surface hydrogeological investigation and results of recharge rates of investigation basins from December 2004 to November 2009 are calculated by using the water budget method. Spatial estimation of hydrological quantities for the groundwater recharge rate is demonstrated by the runoff analysis. As a result, average of the groundwater recharge rate of whole basins is estimated to 131mm/yr. Suggestive observations related to hydraulic properties of the geology and faults are obtained from consideration to the groundwater recharge rate for each basin.