A thesis submitted in partial fulfillment of the requirement for the degree of Master of Engineering, school of Engineering and Technology

Thesis (M.Eng.) - Asian Institute of Technology, 1982

Three statistical distributions namely log Pearson type- 3, Johnson's Sb and transformed gamma distributions-were considered in order to investigate their applicability to hydrology with regards to their flexibility and difficulties in estimating the parameters. Log Pearson type-3 distribution was applied t o annual streamflow, annual rainfall , annual flood peaks and annual maximum rainfall its parameters were estimated using seven different methods. Johnson' s Sb and transformed gamma distributions were applied to annual streamflow and Annual rainfall, since these are bounded on both sides. Two and four methods for parameters estimation were employed to transformed gamma and SB distributions respectively. It was found that the log Pearson type- 3 distribution using method of mixed moments for its parameter estimation is superior for the application in hydrology. However, care should be taken in using the log Pearson type-3 distribution in flood analysis, as it in most of the cases tends to have an upper bound. The transformed gamma distribution was found to be better than the Sb distribution in both annual streamflow and annual rainfall .