Groundwater velocity determination by single-borehole dilution test

Abstract

The single-borehole dilution test involves the injection of a tracer into a borehole following by repeated water column profiling to monitor groundwater velocity within the vicinity of the borehole. Based on the concept that a tracer's concentration decreases as a consequence of the groundwater dilution, the groundwater velocity can be determined by analysing the measured tracer concentration curves over time. The borehole dilution test allows the determination of both horizontal and vertical velocities in a single well. The presence of vertical flow in a borehole may greatly affect the evaluation of horizontal velocity since the decline of tracer concentration is caused by both horizontal and vertical flow simultaneously. Two approaches presented provide the estimation method of horizontal velocity without using packers to prevent vertical flow.