This paper reports on a routing method to estimate values of four parameters of a transient storage (TS) model that represent solute transport in natural streams with transient storage zones. In this approach a functional relationship between the TS model parameters and an analytical solution of the TS model equation is constructed. Results from a robust constrained nonlinear equation solver are used to obtain an explicit relationship between the mixing data and the terms in the functional relationship. The new method and several existing methods are compared with independently observed values of the TS model parameters. Laboratory flume experiments show that the parameters estimated by the new method are in better agreement with observations than are earlier methods. TS model parameters of 58 mixing data sets obtained from 33 natural streams are estimated. Dispersion data show that the concentration curves from analytical solutions using parameters estimated by the new method provide a good match to the observed concentration curves.