2009 Volume 22 Issue 4 Pages 286-293
Around the new campus of Kyushu University, located in western Fukuoka city, groundwater is a major source for drinking water and industrial greenhouse water supplies. Construction of the new campus started in June 2000 and decrease of groundwater discharge due to reduction of forest area may have caused a significant alteration in the surrounding groundwater and spring water environment. For a better management of available water resources in this area, a combined study of a field tracer test and numerical simulations was made to investigate the interaction between groundwater and surface water in the Obaru river basin, where the river has its source/origin within the campus.
The tracer test using 222Rn (Radon) revealed an active exchange between groundwater and surface water especially in the reach between S3 and Okona-weir. On the other hand, based on the temporal velocity fields during 25 years in the domain obtained using a groundwater flow model, the catchment zones along the left and right banks of the Obaru river were also numerically estimated using Lagrangian particle tracking method.
The results suggested that; 1) the tracer test using Radon can be used to identify locations where an active exchange between groundwater and surface water is present, and that; 2) Lagrangian particle tracking method can be used to determine catchments along the river banks. Combined use of these two methods is considered as an effective tool for estimating exchange between groundwater and surface water along stream banks.
