Earthquake effects on artificial groundwater recharge efforts in south Japan

The Kumamoto area includes 11 municipalities and a population of about one million. The area represents the largest total use of groundwater in Japan. The main recharging area for this groundwater used to be paddy fields for rice production located along the mid-stream section of the Shirakawa River. In the past few decades, the area of paddy fields has rapidly decreased due to the Japanese government's rice production adjustment policy and urbanization. In consequence, the groundwater recharge decreased from 656.2 million m³ in 1992 to 606.9 million m³ in 2006. Thus, groundwater recharge from paddy fields only might not be sufficient for groundwater demand in the future. For this reason, an artificial recharge system was established to increase groundwater recharge. In this study, we review the history of groundwater management and results of 14 years' operation of a large-scale artificial groundwater recharge project in the Kumamoto area. We visualize the resilience of the groundwater management and recharge project by influence of the 2016 Kumamoto Earthquake. It is shown that through an integrated approach of all societal groundwater stakeholders, a sustainable groundwater management can be achieved. The hydrological methods in this integrated approach quantify recharging groundwater volumes for different types of recharge fields by use of 170 local experimental observations. Results and experiences outlined in this paper can be used by planners and managers of dwindling groundwater resources to build resilient systems for groundwater recharge by involving all societal stakeholders through an integrated approach.