Supply of water use as the agriculture water was formed mainly in the Koyoshi River. The Honjo plain field was known as production area creationg high quality rice. In addition, there were fewer rations than agriculture, but is used as water service and water for industrial use elsewhere. However, salinity intrusion was occurred by drought in the Koyoshi River. Distanve of salinity intrusion was from the river mouth to nearly 10 km. It cannot pump up water at Yurihonjo City Koyoshi distinct by salinity intrusion. Therefore, it was grasping to the situation about going up of the salt water and it is very important to examine a condition of the going up.