Detection of Groundwater Vein Streams by Underground Temperature Survey using Sparsely Arranged Measurement Points

Abstract

Groundwater flows which contribute greatly to landslide are found to concentrate in highly permeable layers and are referred to as groundwater vein streams.
The underground temperature survey method is a simple technique, which not only locates the groundwater vein streams, but also determines the radius and depth of these streams by detecting temperature anomaly at a depth of 1m from the ground surface.Conventional measurements show the representative radius and depth of groundwater vein streams are 6m and 9m respectively.It is essential for the exact estimation of the radius and depth that the distance between measurement points be about 6m or less.
When the underground temperature is measured every 20m, on the other hand, the approximate position of groundwater vein streams can be estimated.In this case, the difference between the temperature at a measurement point and the average temperature of neighboring measurement points provides an useful clue for detection of a temperature anomaly due to groundwater vein streams without considering influences of the topography and land cover.
An underground temperature survey conducted every 20m over a 8ha area resulted in the detection of three groundwater vein streams.The radius and depth of the groundwater vein streams were determined by the survey every 4m.