Surface and borehole geophysical methods to detect hydraulic pathways in fractured granitic rock masses and its weathered surface are summarized in this paper, and some newly developed and emerging geophysical methods are explained in detail, i.e. 1) precise gravity sur vey (sur vey points inter val = 1m) and precise fanshooting seismic sur vey (receiving points inter val = 0.5m) at the weathered surfaces of the Abukuma granites can detect a hydraulic pathway of the shallow groundwater system with the width of a few meters, which could not be detected by pre-conducted two-dimensional resistivity survey (electrodes interval = 5m). 2) precise vertical seismic profile survey (hydrophones interval = 0.5m) of a test well in the Abukuma granites can detect open fractures (ie. candidate hydraulic pathways) with the opening width of about 0.1mm, which cannot be accounted as a hydraulic pathway by borehole camera images and fracture properties, but be proved as a hydraulic pathway by water sampling tests. To detect a small hydraulic pathway in granitic rocks needs surface and borehole geophysical methods with high spatial resolution, but few methods can satisfy the required spatial resolution. So it is important to consider the width and length of the target structures, estimate the spatial resolution to detect the structures, and adopt appropriate methods.
The quality of groundwater changes depending on such factors as the source of groundwater, the path of flow, and the residence time. Because of this, one can use such water quality data to classify flow systems and predict paths of groundwater flow. This report will describe case studies regarding groundwater sources, paths of groundwater flow, and residence times, that used groundwater quality and were conducted in three engineering fields: dams, tunnels, and underground research of radioactive waste disposal. Furthermore, upon consideration of the current status of and problems in studies of groundwater flow in these engineering fields, the report will describe what is expected for future hydrological and groundwater studies in the fields of science.