A study on Regional Frequency Analysis of Annual Total Rainfall in Pakistan Using method of linear moments

Ishfaq Ahmad, Aamar Abbas, Muhammad Fawad


This study involves the estimation of regional rainfall quantiles of 30 sites with the help of L-moments based on index flood regional frequency analysis. Discordancy measure based on L-moments is used to screen the data of these 30 sites. Highly elevated areas of Pakistan receive more rainfall on the basis of this characteristic. The study area is divided into four different regions and L-moment based heterogeneity measure ( ) was calculated for each region using four parameter Kappa distribution. The regional quantile estimates are obtained from person type III (PE3), generalized normal (GNO), generalized extreme value (GEV) and generalized logistic (GLO) distributions which are found to be suitable for all four regions based on Z-statistic and L-moment ratio diagram. Accuracy measures for the estimated regional growth curves and quantiles have been calculated for the four candidate distributions, using Monte Carlo simulations. On the basis of this simulation study, it was found that PE3 is most suitable choice for large return period for first three regions and for small return period GNO and GEV are most robust. Similarly for region IV GEV is best for period of 1, 2, 5, and 10 and 20 years return period and for period of 50, 100, 500 and 1000 GNO gives most robust estimates.


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