Hello! Talking about hydrological data (flow rates), I need to calculate the values of return periods to different flow rates and probability distributions... Does anyone know how to do it? In practice, peak flow rates of different return periods can be obtained by the equation: x=σK Where, μ and σ are the mean and standard deviation of the hydrologic observation, K is the frequency factor depending on the skew coefficient and probability distribution and the function of return period. So, I know how to calculate the peak flow rate for a specific return period, but I don't know how to do the opposite... get return period from a peak flow rate. I know it depends to the probability distribution, but talking about the most general distribution like log-normal, gumbel, etc...Any idea?? I would appreciate your help! Thanks!