2005 Volume 47 Issue 2 Pages 235-251
At present, the new campus of Kyushu University is under construction at the hilly area of Motooka and Kuwabara located in the western part of Fukuoka City, Japan. The land-use at the foot of the hilly area is used for private residence, greenhouses, paddy fields, and field farms. The shallow groundwater in this area is used for greenhouses, drinking, and Japanese sake brewery. Specifically, the pumping wells for the greenhouses are situated closed to the tip of the intruded fresh-saline water interface and some of the wells pump up the fresh water floating over the saline water. If there are no counteractions against the alteration of land-use, it is anticipated that excessive pumping of groundwater for greenhouses and the reduction in the groundwater recharge at the new campus may accelerate the saline water intrusion into the aquifer. In order to abate these problems, a project committee organized by the local farmers, municipalities and Kyushu University, monitors the variation of the electric conductivity (EC) at the pumping and observation wells.
In the present report, the variation of EC and the vertical change of fresh-saline water interface are studied. As a result, EC at the all pumping stations varies between 200 and 500μS/cm. This implies that the fresh water is carefully pumped up by the farmers to avoid the contamination of saline water. For some of the monitoring wells that are located close to the pumping wells during the summer season, the depth of EC level which shows about 20,000μS/cm rises and the variation of EC at some monitoring wells often corresponds with the increase of groundwater pumping for greenhouses irrigation. On the other hand, the monitoring wells operating from a distance from the pumping stations showed that the boundary of fresh-saline water is clear and its depth is stable.
