Identification of homogeneous rainfall regions and long-term trends in Bankura and Purulia districts, West Bengal

Abstract

The study examines the seasonal and annual rainfall patterns and variability of 20 Indian Meteorological Department (IMD) stations in the Bankura and Purulia districts using seasonal precipitation data compiled by the Indian Meteorological Department spanning 43 years (1980–2022) at a grid size of 0.25 latitude × 0.25 longitude. The southwest monsoon is the main source of seasonal rainfall, accounting for most of the rainfall each year. The winter and post-monsoon seasons bring only a little rain. There is significant seasonal variation in rainfall across the study area, with substantial differences from place to place. This is because of monsoonal patterns and the land’s topography. K-means and Fuzzy C-means clustering methods were employed to identify homogeneous rainfall regions. K-means clustering identified five distinct rainfall regions with varying characteristics, while Fuzzy C-means clustering provided a nuanced view of overlapping rainfall patterns. Annual rainfall trend analysis using the Innovative Trend Analysis (ITA) and Mann–Kendall tests indicates a predominantly decreasing trend across most stations, suggesting a long-term decline in rainfall. However, a few stations (G1, G7, G18, and G19) exhibit weak increasing trends in annual rainfall, highlighting localized variability within the region. These findings underscore a general decline in rainfall across the study area, with implications for water resource management and agricultural practices. The results highlight the need for adaptive strategies to manage the impacts of declining rainfall and inform future research and climate adaptation efforts.