SHORT NOTE
Tsunami impacts on groundwater quality and its usage in Asahi-city, Chiba Prefecture Japan
Seven years follow-up investigation after the 2011 Tsunami
2019 Volume 61 Issue 1 Pages 55-63
Details
2019 Volume 61 Issue 1 Pages 55-63
The follow-up investigation of impacts of Tsunami caused by 2011off the Pacific coast of Tohoku Earthquake on groundwater and its usage in Asahi-city, Chiba, Japan has been conducted.
High electric conductivities (Max. 16,008μS/cm) found in well waters 2 month after the Tsunami have decreased below 1000 μS/cm in all wells in the research area by February 2018. The groundwater turn over times estimated based on the EC decrease curves obtained from wells in the area were ranged between 2.4 to 4.6 years. Yellow coloured groundwater has started to show after 2 years of Tsunami, which prevents residents from drinking well waters. 32 out of 37 residents who started to drink well water after the Tsunami ceased to drink well water again due to the colour. Based on resident hearing survey, people strongly wish to use well water for drinking again and they feel lack of information on groundwater chemistry and its perspectives. In order to prevent/decrease damage of well water from future Tsunami, perfect water proof sealing of well rids, removal of sea water/evaporation residue on the ground surface after the Tsunami, and continuing pumping up of well water were recommended.
