Optimal Probability Distribution Function and Plotting Position for Annual Maximum Flood in Mahanadi River System, India

Abstract

In the present work, optimum probability distribution function and plotting position of annual maximum flood series data obtained for Mahanadi River system has been analysed. For the analysis, 25 to 45 years of data obtained from Nineteen gauging stations of Mahanadi river system have been considered. Different commonly used probability distribution functions have been tested for their applicability at all the nineteen gauging stations individually. They are Generalised Extreme Value (GEV), Generalised Pareto (GP), Log-Pearson III (LP III), Normal, Log normal (LN), Log-Logistic (LL), Log-Logistic 3P(LL-3P), Log normal 3P(LN-3P), Pareto (P) and Gumbel max method.  A comparison of the results obtained using these distributions has been done with the Weibull, Hazen & California plotting positions. From the results, the Generalised Pareto (GP) probability distribution provided best results followed by GEV and Log Pearson Type III. The goodness of fit tests namely Kolmogorov-Smirov (KS), Anderson-Darling (AD), and Chi squared (CS) tests has been done to assess the best performing probability distribution. The annual maximum flow observed are compared well with the predicted annual maximum flow for the return period of 5, 10, 20, 25, 30, 35 and 45 years. The results obtained are promising and can be used for design and development of water resources projects in Mahanadi river system.