Can variability in the form of the power law streamflow recession be used to predict the time-varying distribution of catchment transit times?

The streamflow recession is often well approximated by a power law functional form, dq/dt = -aqb. However, origins of the power law form of recessions, and interpretation of the observation that the parameters a and b vary on an event-by-event basis, remain open problems. We extend previous research that conceptualizes the nonlinear catchment response as a sum of responses from a heterogeneous collection of linear hillslope reservoirs. For a given power law recession form, we derive the necessary partitioning of storage amongst the collection of hillslope reservoirs. The partitioning is used to express the water exit age distribution of the catchment as a function of the power law recession parameters. Results have implications for using recession derived information as a basis for characterizing the transport behavior of catchments; or employing tracer experiments in a full characterization of state-based catchment responses.