In a highly dispersive groundwater flow system (D/ux≫1), application of piston flow model leads to considerable overestimation of flow velocity. In the case of semiconfined aquifers, the flow velocity is further overestimated due to addition of relatively young water through leakage from overlying shallow aquifers. In this paper we discuss how, based on simultaneous measurements of two radiotracers of widely differing half lives, one can obtain meaningful estimates of the aquifier parameters, namely, the flow velocity, dispersion coefficient, and the leakance. We have studied the behavior of a radiotracer by using the diffusion-advection equation for the steady groundwater movement through porous media and analyzed the propagation of the radiotracer along the direction of flow in the aquifer for different aquifer parameters and tracer half-lives. Uncertainties arising due to nonradioactive loss of radiotracers are discussed in detail. The errors in the estimation of the mean dispersion time (D/u2) arising from (1) finite errors in the measurement of radiotracer concentrations and (2) finite nonradioactive loss of the tracers in the aquifer have been evaluated. These calculations allow one to select a suitable 'pair' of radiotracers for a given field situation.