High Impact Factor : 4.396 icon | Submit Manuscript Online icon |

Probability Analysis of Rainfall in Dhemaji Region, Assam, India


Nandana Pegu , AMITY UNIVERSITY HARYANA INDIA; Prof. R.K. Malik, Amity School of Engineering and Technology, Amity University Haryana, Gurgaon, India


Monthly, Seasonal, Annual Rainfall, Return Period, Frequency, Probability Distribution


The monthly rainfall data of Dhemaji region, Assam, India for the period of 35 years (1980-2014) had been analyzed using probability distribution methods viz Normal, Log normal, Log Pearson-III and Gumbel distribution. These probability distribution methods were applied to estimate the expected monthly, seasonal and annual rainfall for the period of 1980-2014. Weibull`s plotting position was used for computation of observed monthly, seasonal and annual rainfall separately in 1.03, 1.05, 1.11, 1.25, 1.33, 2, 4, 5, 10, 20 and 25 years return periods. The Observed and expected values were compared using Chi Square Test (ℵ^22) test. The result indicated that Gumbel distribution method was the best fit to predict annual rainfall for different return periods. In case of seasonal analysis, Log-Pearson-III was found to be the best fit. However, the best fit probability distribution of monthly data was found to be different for different months. Log-Pearson-III was determined as the best fit probability distribution for the months of June and July. In case of the month of August, the lowest Chi square value (10.24) obtained by Log normal distribution and for the month of September; the best probability distribution selected by Chi square test was Normal distribution. As per Gumbel distribution, annual rainfall of 2437.76mm can be expected with 90% probability in 1.11 year return period while annual rainfall of 4796.47mm can be expected with 1% probability in return period of 100 years. The magnitude of 2960.18 mm annual rainfall with 50% probability can be expected in every 2 years which is approaching to mean annual of 3050mm. Again the seasonal rainfall of 2121.82 can be expected with 50% probability in same return periods as estimated by Log Pearson-III. In monsoon season, the expected rainfall during July is higher as compared to other monsoon months. On this month, precipitation of 295.22mm is expected with 90% probability in 1.11 years. In every 2 years return period, July month is expected more shower of 741.92mm with 50% probability as compared to other monsoon months June (508.9mm), August (533.18 mm) and September (449.19 mm). The highest average rainfall observed in July was 636.81mm .The developed regression model also indicated the best fitted curve of each monsoon months, seasonal and annual scattered observed rainfalls with R^2value more than 0.90, except in case of July, it was 0.78.

Other Details

Paper ID: IJSRDV3I40970
Published in: Volume : 3, Issue : 4
Publication Date: 01/07/2015
Page(s): 3387-3394

Article Preview

Download Article