INVESTIGATION OF GROUND WATER RADIAL FLOW USING RADIOACTIVE TRACERS

Abstract

Field experiments had been made to study the effective porosity of the ground water aquifer, injecting I¹³¹ simultaneously with H³, as a reference, at different depths, in the aim of examining the influence of the depth of injection of the radioisotopes on the values obtained for the effective porosity of the aquifer under pumping conditions.

A pumped well, fully penetrating a homogeneous sandy aquifer, was chosen. Three runs were undertaken injecting the radioisotopes in a 10 metres distant observation well at three different levels. An additional run was made injecting I¹³¹ at the three depths simultaneously. In each run, the activity of the outflowing water was followed till it reached the background level.

The results indicate that the values obtained for the effective porosity of ground water aquifer using tracers are not dependent on the depth of injection of the tracer. This conclusion holds for radial flow, in homogeneous aquifers, between the observation well and the pumped well.

The percentage recovery of the injected activity was calculated.

The experiments were undertaken in Wadi El-Natrun area in the western desert of the U.A.R. The value of the effective porosity for the investigated locality was found to be 0.09.