Rainfall variation and frequency analysis study in Dharmapuri district, India

Abstract

Thirty two years (1982-2013) daily rainfall data for Dharmapuri District was collected from the TWAD (Tamil Nadu Water Supply and Drainage Board) to analyse the nature of distribution and frequency of rainfall. Average annual rainfall for 32 years data was calculated as 938.1 mm and average annual rainy days were 45.9. Maximum monthly rainfall (197.58 mm) was received during the month of September which was mostly by southwest monsoon. Maximum rainy days were in October (8.6 days). The rainfall received during the winter, summer, southwest and northeast monsoon seasons were 10.5, 181.0, 453.5, 293.0 mm, respectively. Rainfall frequency analysis done by Weibull’s method revealed that the annual average rainfall of 938.1 mm can be expected to occur once in 2.5 years at a probability of 40 %. Monthly dependable rainfall (p>75 %) is expected to occur in every year during the months from September to October.