Single-Storm Runoff Analysis Using Z-Transform

At present, various methods are available to analyze storm runoff data. Among these, application of the Z-transform is comparatively new, and the technique has been used to identify rainfall from analysis of a single-storm runoff. The technique works under the premise that the rainfall-runoff process behaves as a linear system for which the Z-transform of the direct runoff equals the product of the Z-transforms of the transfer function and the rainfall. In the hydrologic literature, application aspects of this method to the rainfall-runoff process are lacking. As a result, some of the conclusions reported in the literature are questionable. The present study provides a rational basis for the application of the Z-transform technique to the analysis of storm-runoff data. Using data from a previously reported study, the study also explains the selection aspects of the unit hydrograph and the rainfall and lays the necessary background for the correct use of this method by hydrologists.