- This data was created based on the "Measurement Results of the Radiation Monitoring Targeting the Former Evacuation-Prepared Area in case of Emergency and Area to which Evacuation Orders Are Ready to be Lifted (Rivers)" released to the public in the Monitoring Information of Environmental Radioactivity Level portal site by the Secretariat of the Nuclear Regulation Authority.
- For the measurements, the water samples were collected at the rivers in the "Former Evacuation-Prepared Area in case of Emergency" (Minamisoma city, Tamura city, Kawauchi village, Hirono town, and Naraha town) and the "Area to which Evacuation Orders Are Ready to be Lifted" (Minamisoma city, Tamura city, Kawauchi village) and the upstream of these rivers from May 2012 to June 2012.