5:15 PM - 6:45 PM
[HCG20-P05] Regional groundwater flow in the Kamikita Plain evaluated by GIS-based analysis of hydrogeological and geochemical data
Keywords:GIS, hydrogeological data, groundwater, water quality, isotope, Kamikita Plain
For intermediate-depth disposal of radioactive waste, it is essential to assess the regional groundwater flow including the potential repository site. In this study, we analyze hydrogeological data from existing reports and groundwater chemistry and isotope data obtained from groundwater surveys on a GIS platform to investigate the regional groundwater flow in the Kamikita Plain, Aomori Prefecture.
The Kamikita Plain is a relatively low-lying coastal plain with marine terraces widely distributed throughout the region. It includes a large brackish coastal lagoon, Lake Ogawara, in the northeastern part. Drilling surveys were conducted at three locations to obtain detailed geologic columns, groundwater chemistry, isotopes, and hydraulic data. Groundwater sampling was also carried out at over 30 pumping wells and boreholes currently in operation. Hydrogeological information from more than 500 wells in the Kamikita region has been compiled in a GIS, based on existing reports published by local governments.
From geologic columns from the existing reports, we extracted data that allowed identification of well location and elevation, determined formation boundaries, and created a 3D geologic model based on this data (Gresse et al., 2023). The vertical and horizontal hydraulic conductivities for each formation were calculated using the geologic columns and representative hydraulic conductivity values for each lithology. Based on this, the lateral groundwater flow characteristics were estimated for each formation. Hydrogeological data, such as the proportion of clay/silt layers in thickness and hydraulic head, were mapped for each formation. The hydraulic head distribution was used to trace potential groundwater flow paths through each borehole and estimate recharge areas in GIS. The apparent 14C ages of the groundwater samples collected during the borehole investigations range from 16,000 to 19,000 years at the maximum, corresponding to the last glacial period. In this presentation, we report on the characteristics of groundwater flow in the Kamikita Plain by analyzing the relationship between the distribution of water chemistry and isotope data and that of the hydrogeological data.
Acknowledgement
The main part of this research project has been conducted as the regulatory supporting research funded by the Secretariat of Nuclear Regulation Authority (NRA), Japan.
Reference
Gresse, M. et al. (2023) Preliminary 3D groundwater flow modelling of Kamikita plain (Japan): long-term simulation of seawater intrusion. Japan Geoscience Union Meeting 2023, AHW21-P06.
The Kamikita Plain is a relatively low-lying coastal plain with marine terraces widely distributed throughout the region. It includes a large brackish coastal lagoon, Lake Ogawara, in the northeastern part. Drilling surveys were conducted at three locations to obtain detailed geologic columns, groundwater chemistry, isotopes, and hydraulic data. Groundwater sampling was also carried out at over 30 pumping wells and boreholes currently in operation. Hydrogeological information from more than 500 wells in the Kamikita region has been compiled in a GIS, based on existing reports published by local governments.
From geologic columns from the existing reports, we extracted data that allowed identification of well location and elevation, determined formation boundaries, and created a 3D geologic model based on this data (Gresse et al., 2023). The vertical and horizontal hydraulic conductivities for each formation were calculated using the geologic columns and representative hydraulic conductivity values for each lithology. Based on this, the lateral groundwater flow characteristics were estimated for each formation. Hydrogeological data, such as the proportion of clay/silt layers in thickness and hydraulic head, were mapped for each formation. The hydraulic head distribution was used to trace potential groundwater flow paths through each borehole and estimate recharge areas in GIS. The apparent 14C ages of the groundwater samples collected during the borehole investigations range from 16,000 to 19,000 years at the maximum, corresponding to the last glacial period. In this presentation, we report on the characteristics of groundwater flow in the Kamikita Plain by analyzing the relationship between the distribution of water chemistry and isotope data and that of the hydrogeological data.
Acknowledgement
The main part of this research project has been conducted as the regulatory supporting research funded by the Secretariat of Nuclear Regulation Authority (NRA), Japan.
Reference
Gresse, M. et al. (2023) Preliminary 3D groundwater flow modelling of Kamikita plain (Japan): long-term simulation of seawater intrusion. Japan Geoscience Union Meeting 2023, AHW21-P06.