Determination of design hydrological characteristics with consideration of historical maxima

Application of information about the historical maxima in hydrological computations allows one to improve design hydrological performances and to pass in some cases from extrapolation to interpolation as a more reliable solution. In this paper, an analytical solution is given for a task of determination of empirical probabilities and parameters of distribution function taking into account any historical maxima, which are located inside as well as outside the time series of observations and for their mixed location. For particular case studies, an advantage of consideration of the historical maxima is shown in comparison with computations without these maxima. It has also been shown that the exponential function between maximum discharges in order of their reduction and ordinates of standard normal distribution are effective enough for fitting the upper part of empirical distribution function.