Aspects of the subject technology relate to systems, methods, and computer readable media for determining a parameter of a formation based on withdrawal of an injected tracer solution. A changing concentration profile of a volume of tracer solution that is withdrawn from a formation is measured. A varying simulated concentration profile associated with the tracer solution in a simulated formation is generated by modifying simulated formation parameters of the simulated formation. The varying simulated concentration profile is compared to the changing concentration profile of the volume of tracer solution that is withdrawn from the formation. A parameter of the formation is identified based on a comparison of the varying simulated concentration profile to the changing concentration profile of the volume of tracer solution withdrawn from the formation.