GEV-PWM Model for Distribution of Minimum Flows

Abstract

Equations for the probability weighted moments (PWMs) of the generalized extreme value (GEV) distribution for minima are derived. The GEV-PWM model and five other models are fitted to the low flow data of 16 streams. The suitability of the models is checked by the probability plot correlation coefficient test. Weibull distribution fits the data better than lognormal. GEV-PWM has the best performance among the three-parameter models, but it frequently leads to infeasible lower bounds. The 10-year minimum flow estimates based on various models are determined. In the majority of cases (11 stations), differences between the largest and the smallest estimates are <20%. However, in a few cases, rather large differences (71%) are found. The estimates from the GEV-PWM and W3-MSO models are usually either the largest or smallest at a station.