Numerical approach for the evaluation of Weibull distribution parameters for hydrologic purposes

In hydrology, the statistical description of low flow phenomena is very important in order to evaluate the available water resource especially in a river and the related values can be obviously considered as random variables, therefore probability distributions dealing with extreme values (maximum and/or minimum) of the variable play a fundamental role. Computational procedures for the estimation of the parameters featuring these distributions are actually very useful especially when embedded into analysis software [1][2] or as standalone applications. In this paper a computational procedure for the evaluation of the Weibull[3] distribution is presented focusing on the case when the lower limit of the distribution is not known or not set to a specific value a priori. The procedure takes advantage of the Gumbel[4] moment approach to the problem.