Asian Journal of Geographical Research

Aims: This research investigates the temporal distribution of rainfall in Thanjavur district, aiming to enhance our understanding of climatic patterns prevailing in Thanjavur district. The study investigates the return period, probability of occurrence and the seasonal changes in rainfall for five decades. Employing a comprehensive analysis of historical meteorological data, the study seeks to identify trends, anomalies, and potential shifts in rainfall patterns.

Study Design: Geostatistical techniques are adopted for studying trend analysis in rainfall pattern using Annual and monthly rainfall data for 51 years from 1972 to 2022.

Place and Duration of Study: The study area, Thanjavur district is predominantly an agricultural region which lies in the Eastern part of Cauvery delta and it is called the Rice Bowl of Tamil Nadu. This study takes a period of data for 51 years from 1972 to 2022.

Methodology: The return period and probability of occurrence are calculated using MS Excel.  Linear regression model is adopted to predict the variations in rainfall depending on changing years. The trend analysis in rainfall for the years 1972 to 2022 using Mann – Kendall Test and Sen's Slope Estimator Test are performed using XLSTAT.

Results: The maximum rainfall received in the study area is 2141.760 mm and a minimum of 494.600 mm. The mean rainfall is 1144.131 and the calculated value of standard deviation reveals that deviation of rainfall is 342.168 mm over a period of 51 years. Large value of Standard deviation indicates that there is larger variation in rainfall pattern in the study area. Regarding the regression analysis, out of 51 observation years nearly 15 years (1974, 1977, 1980, 1982, 1993, 2001, 2002, 2003, 2010, 2011, 2012, 2016, 2017, 2018, 2021) have outlying residual values. The remaining years follow good fit. From the values of Kendall's Tau, it is assumed that in the 51 years of period in the months of January, May and August there is stronger positive trend. In which, January exhibits the higher value, showing a high increasing trend in rainfall.

Conclusion: Changing rainfall patterns are not just a climate concern, but are deeply interlinked with national development goals. Accurate rainfall monitoring and interpretation can help in designing the climate resilient policies, secure sustainable water use, and protect lives and livelihoods through planning. Regarding the rainfall pattern in the study area, the January, April, May, June, August and November are showing an increasing trend in which January, May and August months are showing higher values of increase. Although the study area receives its maximum rainfall in the NE monsoon season (Oct – Dec), September, October and December months are showing a decreasing trend. Only November month shows a slight increase trend. As the study area stays on agrarian economy and the agriculture pattern mostly depend on NE monsoon. The decrease trend in rainfall pattern indirectly affects the economy and further developments.