This study was designed to find the best-fit probability distribution of annual rainfall based on 50 years sample (1966-2015) in the Karkheh river basin at Iran using six probability distributions: Normal, 2-Parameter Log Normal, 3-Parameter Log Normal, Pearson Type 3, Log Pearson Type 3 and Gumbel distribution. The best fit probability distribution was selected using Stormwater Management and Design Aid (SMADA) software and based on the Residual Sum of Squares (R.S.S) between observed and estimated values Based on the R.S.S values of fit tests, the Log Pearson Type 3 and then Pearson Type 3 distributions were found to be the best-fit probability distribution at the Jelogir Majin and Pole Zal rainfall gauging station. The annual values of expected rainfall were calculated using the best fit probability distributions and can be used by hydrologists and design engineers in future research at studied region and other region in the world.<\/p>\r\n","references":"[1]\tAlahmadi, F., Abd Rahman, N., Abdulrazzak, M. \u201cEvaluation of the best fit distribution for partial duration series of daily rainfall in Madinah, western Saudi Arabia\u201d, Evolving water resources system: understanding, predicting and managing watersociety interactions proceedings of ICWRS2014, Bologna, Italy, 2014.\r\n[2]\tAlghazali, N. O., Alawadi, D. A. \u201cFitting statistical distributions of monthly rainfall for some Iraq stations\u201d, Civil and Environmental Research, 2014, 6(6): 40-46.\r\n[3]\tAbdullah, M. A., AL-Mazroui, M. A. \u201cClimatological study of the southwestern region of Saudi Arabia, I. Rainfall analysis\u201d, Climate Research, 1998, 9: 213-223.\r\n[4]\tAmin, M. T., Rizwan, M., Alazba, A. A. \u201cA best-fit probability distribution for the estimation of rainfall in northern regions of Pakistan\u201d, Open Life Sciences, 2016, 11(1): 432\u2013440.\r\n[5]\tBhakar S. R., Iqbal M., Devanda M., Chhajed N., Bansal A. K. \u201cProbability analysis of rainfall at Kota, Indian\u201d, J. Agri. Res, 2008, 42: 201-206\r\n[6]\tHann, C. T. \u201cStatistical methods in hydrology\u201d, The Iowa State University Press, 1977.\r\n[7]\tMohamed, T. M., Ibrahim, A. A. A. \u201cFitting Probability Distributions of Annual Rainfall in Sudan\u201d, SUST Journal of Engineering and Computer Sciences (JECS), 2016, 17(2): 34-39.\r\n[8]\tOsati, K., Mohammed, M., Karimi, B, Naghi, S, Mobaraki, J. \u201cdetermining suitable probability distribution models for annual precipitation data (A case study of Mazandaran and Golestan provinces)\u201d, Journal of Sustainable Development, 2010, 3(1): 159-168.\r\n[9]\tSheng Y., Michio H. \u201cprobability distribution of annual, seasonal and monthly precipitation in Japan\u201d, Hydrological Sciences Journal, 2007, 52(5): 863-877.\r\n[10]\tTao D. Q., Nguyen V. T., Bourque A. \u201cOn selection of probability distributions for representing extreme precipitations in Southern Quebec\u201d, Annual Conference of the Canadian Society for Civil Engineering, 5th-8th June 2002, 1-8.\r\n[11]\tWaylen, P. R., Qusesada, M. E. and Caviedes, C. N. \u201cTemporal and spatial variability of annual precipitation in Costa Rica and southern oscillation\u201d, Int J Climatol, 1996, 14: 173-193.","publisher":"World Academy of Science, Engineering and Technology","index":"Open Science Index 146, 2019"}