On the interpretation of tracer data in variable flow systems

Abstract A general formula for the interpretation of tracer experiments in variable flow has been derived, based on generalization of the transit (exit) time distribution of the tracer mass flux resulting from an instantaneous injection. Systems with a constant volume or a constant turnover time of the dynamic part of the system are considered. A possible difference between the turnover time and the mean transit time of tracer is allowed for in the final formulae, for cases as in groundwater in which the tracer is delayed due to molecular diffusion into stagnant water.