Estimation of underground water recharge rate in Horonobe nderground Research Laboratory project by water balance method- From August, 2003 to July, 2004 -

Seno, Shoji; Takeuchi, Ryuji  ; Kurikami, Hiroshi  ; Hara, Minoru

Horonobe Underground Research Center of Japan Nuclear Cycle Development Institute has been investigating surface hydrogeological features in and around the Horonobe nderground Research Laboratory (URL) area as a part of Horonobe URL project. In order to calculate the recharge rate into the deep underground by the water balance method, monitoring systems of the river flux and meteorological stations have been phased in since 2002.In this report, the annual recharge rates of the P-1, P-2 and P-3 basins that are located in and around the URL area are calculated by using the data from August 2003, when the installation of the monitoring systems had been completed, to July 2004.The result shows that the recharge rates of the P-1, P-2 and P-3 basins are 230 mm/y, -20 mm/y and 340 mm/y, respectively. It means that the P-1 and P-2 basins are recharge areas and the P-3 basin is a discharge area. The average infiltration rate within the three basins is estimated to be 100 mm/y.