Groundwater flow system was investigated at a upland field in the central part of Ibaraki Prefecture. Underground temperature survey was conducted to locate the groundwater vein streams and to determine the place for test boring. The depth down to the top of the groundwater vein stream was estimated to be 2.5 m from the ground surface at the boring point. Groundwater flow rate was measured by means of the groundwater surveyor and tracer test. It was also calculated using the hydraulic conductivity determined by in situ permeability test or effective grain size. The flow rate was less than 10 4 cm/s down to the depth of 3 m, greater than 10 4 cm/s at the depth deeper than 3 m. The flow rate at the depth of 3.6 m outside the groundwater vein stream was one-third of that at the same depth inside it. These results show the location and the depth of the groundwater vein stream estimated by means of the underground temperature survey were correct, and groundwater flows at higher flow rate in the groundwater vein stream than another part of the ground.
