Reducing Hydrologic Parameter Uncertainty

A methodology is introduced that can be used in hydrologic frequency analysis to reduce the parameter uncertainty. The methodology consists of developing generalized values of the parameters (mean, standard deviation, and skewness) through the use of a weighting procedure between sample and regionalized statistics. Weights are defined as a function of the variances of the sample parameters and regionalized parameters. The variances of the sample parameters are determined using two nonparametric statistical methods, the jackknife and the bootstrap. The variances of the regionalized parameters are determined through regression analysis. The ability of this methodology is illustrated using flood flow frequency data for the Southwestern United States.