Rainfall trend analysis in the Lower Gangetic Plain: a study on selected rainfall stations of Maldah district, West Bengal, India

Changes in rainfall pattern are of significance in terms of water resource management, hydrological modelling, environmental hazard management and agricultural planning. In the present study I assess the annual and seasonal rainfall trend, including concentration in eight rainfall stations in Maldah district, located in the lower Gangetic plain of West Bengal, India during 1985-2015. Besides the Mann-Kendall test and Theil-Sen's estimator for assessing the trend of rainfall, precipitation concentration index (PCI) has been used to examine intra-annual rainfall variability. The study reveals decreasing trend of annual and monsoon rainfall in seven rainfall stations. Among them, significant trend is found in five and four rainfall stations respectively. This is followed by pre-monsoon and post-monsoon rainfall characterized with decreasing trend in five and eight rainfall stations respectively. The results of PCI show fluctuation of rainfall distribution in the district from moderate to strong irregular during the study period. However, decreasing trend of annual PCI values in the seven rainfall stations, with significant value in one of them, implies a tendency towards moderate rainfall distribution in the respective stations. Nevertheless, ChanchalI rainfall station solely showed increasing annual PCI value and thereby an affinity towards strong irregular distribution of rainfall. Despite decrease in annual and seasonal rainfall, increase of pre-June (May) and post-September (October) rainfall prolonged the rainy season, which is responsible for drainage congestion as well as seasonal inundation in low-lying areas of the district.