Comprehensive Trend Analysis of Monthly and Seasonal Rainfall in the Shetrunji Basin, India Using Statistical and Innovative Techniques

ABSTRACT Understanding long‐term rainfall variability is essential for sustainable water resource planning, particularly in semiarid regions like the Shetrunji River Basin in Gujarat, India. The study adopted a hybrid approach that integrates statistical methods, namely the Mann–Kendall (MK) test, Modified Mann–Kendall (MMK) test, and Sen's Slope estimator with graphical techniques such as Innovative Trend Analysis (ITA) and Innovative Polygon Trend Analysis (IPTA) to investigate monthly and seasonal rainfall trends spanning the period from 1971 to 2023. The MMK test was applied to correct for lag‐1 autocorrelation, ensuring reliable detection of monotonic trends. Seasonal analysis revealed statistically significant increasing rainfall trends during the monsoon period, especially in July and September at stations such as Toda and Chirod, while the pre‐ and post‐monsoon periods exhibited mostly insignificant or no trends. Monthly trend results showed high spatial and temporal variability in rainfall behavior across stations. The ITA method effectively identified segment‐wise and non‐monotonic trends. At the same time, IPTA provided visual insight into intra‐monthly fluctuations and transition phases, reinforcing the value of graphical techniques for capturing subtle rainfall dynamics. The study's outcomes highlight the inadequacy of uniform water management strategies and call for localized interventions such as adaptive cropping calendars, targeted groundwater recharge, and improved flood forecasting. The integrated methodological framework proposed in this study serves as a replicable model for climate‐sensitive basins, contributing to evidence‐based water governance and resilience planning under evolving climatic conditions.