Author(s): Keiichi Yamada; Daizo Ueda
Keywords: Measurement of groundwater flow; CCD Camera; Vertical distributionvelocity; Point dilution method
Abstract: To make sure heterogeneity ground on unconfined groundwater flow, measurements of groundwater flow velocity by CCD camera in 15 observation wells were carried out with coefficient of variation smaller than 20% at each 5 repeated runs. In each of 15wells at 1m depth, totally at 5 to 8 point measured velocity were varied widely from0. 07*10**-3m/s to 3. 14 mm/s. These ranges were similar to the results from other report. High speed zone with velocity over 10**-3m/s was found at 4 wells and in every measurement at different month high speed zone could be confirmed at the same depth. Although flow direction at low speed zone with velocity smaller than1mm/s scattered widely, at high speed zone that was within a range of 30 degree during the period. V by CCD camera were compared to Vp by point dilution method. Both vertical profiles were similar each other and V is larger 100 times than Vp. The velocity in high speed zone increased linearly with the elevation of groundwater table, however that in low speed zone decreased a little. High speed zone in 4 wells are located almost at the same depth from 10m to 12m under the ground level where is just lower position of boundary of gravel by the lower terrace (new deposition, 50, 000years ago) and gravel by the upper terrace (old deposition, 100, 00 years ago).