Hydrological Analysis on Rainfall Data in Tamilnadu: An Application of Mann Kendall’s Test and Sen’s Slope Estimator

This study examines trends and variability in rainfall patterns across Tamil Nadu with the objective of informing sustainable water resource management and agricultural planning. Non-parametric statistical techniques, namely the Mann-Kendall (MK) trend test and Sen’s slope estimator, are employed to assess the direction and magnitude of changes in precipitation. The analysis is based on a 15-year time series of rainfall data, categorized into South West monsoon, North East monsoon, winter season, hot weather season and total annual rainfall. The results indicate a statistically significant upward trend in South West monsoon rainfall, with an average increase of 11.32 mm per year. In contrast, the North East monsoon exhibits a declining trend, with an average decrease of 3.18 mm per year. These findings suggest a shift in the temporal distribution of rainfall in the region. Given that agriculture in Tamil Nadu is highly dependent on North East monsoon precipitation, the observed decline has important implications for crop productivity and water security. The study highlights the need for adaptive water management strategies, including enhanced storage and conservation of surplus rainfall during the South West monsoon through infrastructure such as reservoirs, canals and rainwater harvesting systems. Such measures are essential to mitigate the impacts of seasonal variability and ensure sustainable utilization of water resources under changing climatic conditions.