Meteoric Water Trend Analysis using Statistics and GIS for Drought Condition Assessment on Climate Change Aspects in Thoothukudi District, Tamil Nadu, India

Abstract

Precipitation is the most important variable for climate change studies, and also mostly determines the drought conditions on the Earth’s surface. The present study assessed rainfall variation and monitored drought conditions in the Thoothukudi district of Tamil Nadu, India. In this study, various statistical methods are employed to determine the annual average rainfall and seasonal rainfall over 30 years. The monthly rainfall variation was computed using Standard Deviation (SD) and Coefficient of Variation (CV), and trends in monthly rainfall were estimated using the Mann-Kendall and Sen’s Slope test for three decades from 1990 to 2019. The drought condition in the study area was also monitored. The study’s findings indicate that the annual average rainfall has varied to some extent from year to year. Its variation has increased since 2008. Seasonally, NE monsoons have had a high amount of rainfall inall four seasons over the last 30 years. Other seasons have less rainfall variability during the years 1999 to 2011. The rainfall variation has increased to be more extreme than the state’s seasonal average, except in summer. In the SW monsoon, rainfall has increased slightly, but it’s also below the state’s seasonal average due to the dynamic changes in monthly rainfall. The monthly rainfall variation over three decades, significantly consistent in April, May, August, September, October, and November, and January, February, March, and June, shows dispersion, with CV mostly below 100% and above 100% respectively during the I and II decades.In the III decade, all the month’s rainfall variation is dispersed except Nov. Whereas, in July and Dec, the rainfall variation has been changing every decade, with its dispersion or consistent variation. The Mann-Kendall and Sen’s Slope test indicates that the trend is decreasing or increasing witha 95% confidence level of significance. Generally, excessive rainfall is recorded during the NE monsoon season in Tamil Nadu. During the first three decades, excess rainfall has been reported in Kayalpattinam, Tiruchendur, Kulasekarapattinam, and Santhankulam, whereas scanty to deficient rainfall has been reported in the other two decades.