Uncertainty Quantification of groundwater budget estimated by surface-subsurface hydrologic model for advanced groundwater management in Kumamoto Area, southern Japan

For sustainable use of groundwater, it is important to know the current water balance and the impact of changes in land and water use for working with stakeholder collectively.

In order to understand these issues, a distributed hydrological model that includes the key processes of the regional hydrological system is considered to be a powerful tool, as it enables us to understand the impact of human activities at any given site.

In the Kumamoto region, which is almost 100% dependent on groundwater for drinking water, there have been attempts to understand groundwater flow and water balance qualitatively and quantitatively (Ministry of Land, Infrastructure, Transport and Tourism (2011), CREST model (2015), Kumamoto earthquake PJ (2021)), but parameters such as hydraulic conductivity have been determined empirically from pumping tests and other data.

However, considering the heterogeneity of the subsurface and other factors, these parameters contain uncertainties, and it is necessary to quantify groundwater balance based on the understandings of these uncertainties.

In this study, we conducted sensitivity analysis to identify important parameters, focusing on the Togawa lava, which is a particularly important aquifer in the Kumamoto area.

And then, uncertainty quantification of these important parameters was conducted and quantified the groundwater balance of the Togawa lava based on the uncertainty of each parameter.