Proceedings of the International Conference on Industrial Engineering and Operations Management Washington DC, USA, September 27-29, 2018 © IEOM Society International An Exploratory Analysis of Rainfall: a Case Study on Western Ghats of India Pradeep Suryanarayana Barimar Rao Transportation Engineering Consultant 2500 Merchants Row Blvd, Apt 164, Tallahassee FL 32311 s.pradeep.rao@gmail.com Swathi Shetty, Pruthviraj Umesh, Amba Shetty Department of Applied Mechanics and Hydraulics NITK Surathkal, Mangaluru, Karnataka, India - 575025 meswathi18@gmail.com, pruthviu@gmail.com, amba_shetty@yahoo.co.in Abstract In this study high resolution 0.250 ×0.250 (approximately 25Km×25Km) gridded daily rainfall data is used to analyze the effect of changing climate on distribution of rainfall in different topographical zones of Western Ghats (WG) of India over the period 1901-2013. The non parametric two tailed Mann- Kendall with Hamed and Rao’s method of autocorrelation and Sen’s slope estimator for obtaining magnitude of change over time period is used. The rainfall trend in annual, monsoon and post-monsoon is increasing in state of Goa and Coastal region of Karnataka state and significantly decreasing in some part of Kerala and Maharashtra state. Winter season rainfall has seen a declined trend in southern part of the study area and in high elevated region of Kerala state. Even the mean rainfall over the study area is declining from 1951-1960 with disturbance in alternate sequence of flood and drought year from period 1990. The frequency of heavy rainfall events (65mm-124.4mm) are increasing in recent decades with 40- 50% contribution from 2000-2013 in regions of Maharashtra state. The trend of heavy rainfall events are increasing in West Coast of India at 5% significance level with no trend in very heavy to extreme rainfall events (>124.5mm). Keywords Western Ghats, Rainfall Trend, Extreme Events, Onset of Monsoon 1. Introduction Mountains are the source of high quality water, storehouses of biological diversity, hydropower, food and building materials (Ives et al 1997; Beniston 2003). They supply up to 60% of fresh water in humid region and up to maximum of 90% in arid and semi arid regions (Viviroli and Weingartner 2004). Mountains can be said as “Sentinels to climate change” as they show more dynamic changes than in plains (Du et al 2004; Yao et al 2006). The changing climate due to human anthropogenic activities have contributed to elevated atmospheric greenhouse concentration (Meehl et al. 1996; Watterson and Dix 2003), build up the irregular distribution of hydrological resources (Trenberth et al. 2003) frequencies of irregular seasons and extreme events. These interns increasing threat to mountain biodiversity and also increasing the challenges of mountain water resources. The impact of these changes is not only of direct relevance to high mountains, but they will have serious implications for downstream regions (Beniston et al. 1997). Due to the crucial impact of changing climate on natural resources, mainly on precipitation, several past studies have shed light on variation in precipitation pattern, trend of precipitation (Basistha et al. 2009; Guhathakurta and Rajeevan 2008; Joshi and Pandey 2011; Krishnakumar et al. 2009; Rajeevan et al. 2008; Singh and Mal 2014), variation in onset of South West Monsoon (Fasullo and Webster 2003; Joseph et al. 1994; Patwardhan et al. 2014; Raju et al. 2005) and the frequency of drought and extreme rainfall events in a changing climate over global and regional scales ( Bharti et al. 2016; Guhathakurta et al. 2011; Krishnamurthy et al. 2009; Nandargi and Dhar 2011; Rajeevan et al. 2008; Rakhecha and Soman 1994).Most of the studies have used limited number of stations or 1607