Method of Annual Extreme and Peaks Over Threshold in Analysis of Maximum Discharge

The comparative results of defining high waters with a probabilistic approach are presented in the paper. High waters are defined using two most commonly used methods that are of interest for the rational dimensioning of the corresponding types of hydrotechnical objects and systems: the method of annual extremes and the method of peaks/thresholds. The method of annual extreme treats the theoretical distribution functions commonly used in hydrological practice: Normal (Gaussian), Log-Normal (Galton), Pearson 3, LogPearson 3, and Gumbel's distribution, and the final selection of the function is based on the results of the Kolmogorov test, i.e. agreement of the empirical and theoretical probability distribution functions. For the threshold method, a Poisson-Weibull model with a Poisson distribution for the peak occurrence frequencies and a two-parameter Weibull's distribution for peaks height was used, which for the maximum discharge gives a three-parametric distribution function. Comparative results of high waters according to these methods are given to 11 gauge stations in Vrbas river basin. Basin areas are from 200 up to almost 5300 km(2), and observation duration from 16 to 47 years.