Routine measurements of ground-water velocity using S35.

A method is described for the measurement of the effective velocity of ground-water movement using S35 as a tracer. The method uses modified porous bronze piezometers both for injection of the tracer and sampling of the ground water. S35 was used routinely at Chalk River with good results, and a comparison of S35 with tritium and fluorescein dye is given. Among the advantages of S35 as a tracer is its detectability by simple chemical and counting methods at concentrations well below the maximum permissible values for drinking water. The application of the technique to other problems involving ground water is also mentioned.