Long-term Rainfall Trend Analysis in Ambedkar Nagar, Uttar Pradesh, India

Abstract

Rainfall variability is an important concern for agricultural planning and water-resource management in Ambedkar Nagar district, Uttar Pradesh, where crop production depends largely on monsoon rainfall. This study analysed long-term rainfall trends using 40 years of daily rainfall data from 1980 to 2019 obtained from the NASA Prediction of Worldwide Energy Resources (POWER) database. Monthly, seasonal and annual rainfall series were examined using the Mann-Kendall test and Sen's slope estimator after applying pre-whitening to reduce the effect of serial autocorrelation. The results indicate a statistically significant decline in annual rainfall, with a Sen's slope value of approximately -12.50 mm year-1. The monthly analysis showed no significant increasing trend in any month, while declining tendencies were observed mainly during June, July, August and September, which are the principal monsoon months. Seasonal analysis showed an increasing pre-monsoon Z statistic (Z = 3.09), whereas the monsoon season showed no significant change (Z = -0.43), and post-monsoon and winter rainfall showed declining tendencies (Z = -1.36 and Z = -1.38, respectively). Decadal analysis further indicated that rainfall reductions were more evident during the second and third decades of the study period, particularly in the monsoon and annual series. The overall pattern suggests weakening annual rainfall and notable intra-seasonal variability in the district. As the district is largely agricultural, these changes are directly relevant to crop planning and local water-use decisions. These findings highlight the relevance of district-level rainfall assessment for improving irrigation planning, groundwater management, rainwater harvesting and climate-resilient agricultural practices in monsoon-dependent regions.