Analysis of extreme rainfall events over Nethravathi basin

Abstract

India gets three fourths of its annual rainfall during the south-west monsoon season (June–September). The study of extreme events is significant in the stochastic behaviour of rainfall pattern. The aim of the present work is to compare different methods; and find a suitable method to study extreme rainfall trend analysis. In this study, frequency distribution method, generalized extreme value (GEV) distribution, Mann–Kendall and Sen’s slope estimator are used for rainfall trend analysis over the Nethravathi basin located in the southern part of India. The rainfall data during the monsoon months (June–September) were analysed for a period of 1971–2010. The comparison of all the methods had been carried out and it has been observed that there is an increasing trend of frequency in class-1 and decreasing trend in class-2 and class-3, respectively. The interpretation of the results is carried by using the GEV distribution and non-parametric trend analysis (Mann–Kendall and Sen’s slope estimator test). It turns out the best results to identify the extreme rainfall trend are obtained by the statistical techniques – Block Maxima (GEV) distribution, Mann–Kendall and Sen’s slope estimator test as compared to frequency-based method. The above results which help to study climate change will contribute towards sustainable development of the Nethravathi River basin.

Keywords:

• extreme rainfall events
• GEV distribution
• Mann–Kendall test
• Nethravathi basin
• Sen’s slope estimator

Acknowledgement

This article belongs to the papers presented at the Hydro-2012 conference held at I I T Bombay on December 7–8, 2012 that were short-listed by the Editor for publication in this Journal after re-review and revisions where necessary.