Abstract
The utilization of groundwater resources becomes important in recent years. In addition, not only the quantity but also balance of groundwater is important for disaster prevention and river management. However, groundwater recharge volume is not clear and especially during flood it was difficult to measure it due to the transmission of flood wave. Recharge volume under flood condition can be estimated correctly by using ADCP and unsteady flow analysis. In the Nagara River, It clarified that about 20 % of river discharge decreases as groundwater recharge. The recharge rate is proportional to difference between river and groundwater level. Therefore, monitored river water level is able to derive recharge volume by estimated groundwater level.
