Abstract

India as a tropical country, depends solely on south west Monsoon. Southwest monsoon spans between June and September. The present study is aimed to carry out the probable trend of rainfall and to evaluate its implications on the tanks in Hunsur taluk of Mysore district, Karnataka, India. These tanks were the livelihood sources of water for the farmers in the command area. The lakes considered under this case study have been completely dried up in the recent past. Inconsistency of rainfall is one of the factors which govern the degradation of Lakes. Trend analysis is carried on 40 years daily rainfall data (1975-2014) for monthly, seasonal and annual average values using Mann-Kendall test and Sen’s slope estimation. The analysis shows ‘no trend’ for the months of January, February, March and June. There is an ‘increasing trend’ for the months of August, October and December. However, there is a ‘decreasing trend’ for the months of April, May, July, September and November. The decadal variation indicates a very significant decrease of rainfall for the months of June and July; particularly in the recent decade (2005-2014) and hence a ‘negative trend’ in the South-West monsoon. This may be one of the reasons for the deterioration of tanks in the study area.

Highlights

  • Hunsur is a town and a taluk headquarter in Mysore district of southern India

  • Analysis of four-decade (40) years (1975-2014) data reveals that the average annual rainfall (a.a.r) of Hunsur taluk was 802.37mm which is slightly higher than the mean rainfall of the Mysore district (770mm)

  • It is observed that Pre-Monsoon and Southwest monsoon rainfall are in declining trend and North-East monsoon and annual rainfall trend is on the rising trend

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Summary

Introduction

Hunsur is a town and a taluk headquarter in Mysore district of southern India. It is situated on the western side of Mysore. Various studies have been undertaken to evaluate the effect of climatic changes on water resources, farming and crop production at a global, regional and local levels. Studies conducted from 1902-1980 (Jain and Kumar 2012), for Cauvery basin, shows an ‘increasing trend’ for annual rainfall, ‘decreasing trend’ for pre-monsoon, insignificant ‘positive trend’ for monsoon and very significant ‘increasing trend’ for post-monsoon using Sen’s slope estimator. Some of the investigations outside India are carried in Bangladesh (Rahman and Begum 2013), in Serbia (Gavrilov 2016), in Tasmania, Australia (Laz and Rahman 2014) The objective of this analysis is to find the ‘trend’ of rainfall, to correlate the results with the morphological investigation, to find the surface runoff characteristics and to establish the methods to be adopted in restoring and rejuvenating the degrading lakes/tanks

Study Area
Data and Methodology
Mann-Kendall Test
Sen’s Slope Estimator
Trend of Annual Rainfall
Trend of Decadal Rainfall
Conclusions

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