Single-Well Technique using 32P for Determining Direction and Velocity of Groundwater Flow

A radiographic method for determining the direction, ∅, and the velocity, v, of groundwater flow has been developed. The radioisotope 32P is injected, as a point or a thin-column source, at the centre of the well by means of a simple device. The injection is performed at the desired depth without disturbing the water. The radioisotope is left to follow the horizontal flow of water. Some of the 32P is adsorbed onto the walls of two parallel detecting screens which are separated by a few centimetres and fitted inside the well. Both the inner and outer screens are radiographed; the darkest parts of the emulsions and the north direction marked on another film give the value of ∅. The blackening of each film in the screens is measured. Velocities are determined either by the displacement method or from the calibration curve of the velocity versus relative blackening. (author)