Effect of Artificial Recharge Using Abandoned Rice Paddies for Sustainable Groundwater Management in Kumamoto, Japan

The city of Kumamoto and their surrounding area are unique in that city water is 100% supported only by their abundant groundwater. Recent expansion of the urban land-use area in and around city induces the decrease of the regional groundwater resources in spite of economical water-use efforts. The local governments try to take measures to maintain stable groundwater resources for their sustainable use, new groundwater management system is proposed and regulated by the city government and the large groundwater users in the city areas support the funding system. As the most effective recharge area is to utilize abandoned paddies exists in neighboring towns outside of the city boundary depend on the local hydro-geological setting, this management system can be a typical `trans-boundary groundwater management'. This management system was introduced in 2004 and we have experienced the effect of this system during past six years through monitoring well/lake discharge data and the precise 3D groundwater flow simulation.