Revisiting the Probability Distribution of Low Streamflow Series in the United States

Droughts result in billions of dollars in annual losses, loss of life, and the displacement of people. The characterization of hydrologic drought enhances the prediction of streamflow statistics that are important for various water resource applications. L-moments were used to examine the goodness of fit of selected 3-parameter probability distributions to the low streamflow series at 704 unregulated gaged rivers in the contiguous United States. Stream gages with and without zero flows were identified, and the use of the inverse transformation of nonzero low flows and censoring of both tails of the distribution were explored. Overall, the log-Pearson type III (LP3), 3-parameter lognormal (LN3), and Pearson type III (PE3) all appear to be acceptable distributions for describing the low streamflow series in the United States at sites with no zero low flows. For the inverse flows, the Generalized Extreme Value (GEV) distribution also performed well, while censoring did not improve the ability to distinguish between distributions.