Abstract
Assessing the spatiotemporal variability of meteorological parameters provides critical insights into identifying emerging environmental risks posed by climate change. Such an evaluation can help obtain strong evidence to explain the effects of climate change on crop yields and water resource management. Recent rainfall–drought studies in Bihar have advanced our understanding of seasonal variability; however, several clear research gaps remain. Most analyses still rely heavily on the Standardized Precipitation Index, overlooking complementary water balance, soil moisture, and vegetation indicators needed to capture agricultural and hydrological droughts. Therefore, this study examined rainfall and drought characteristics in the semi-arid climatic region of Bihar. The dataset was acquired from the India Meteorological Department (IMD) for the period between 1970 and 2020 at a spatial scale of 0.25° × 0.25°. Based on the change point tests, the time series was divided into two periods: 1970–1990 and 1991–2020, with 1990 as the change point year. The nonparametric Mann-Kendall test and Sen’s slope were used to identify trends and estimate their magnitude at a 5% significance level. The results showed that the northwestern, southwestern, and central districts of Bihar exhibited negative trends, particularly in June, August, and September. The magnitude of the decline ranged from -1 to -2 mm.y-1. The analysis showed an increasing trend in the total annual rainfall observed between 1970 and 2020. This pattern suggests that the methodological framework employed in this study can be effectively applied across different spatial scales and diverse geographic settings. This study provides a foundation for improved water resource management, climate adaptation planning, and strategies aimed at mitigating the potential impacts of extreme hydrological events.