Spatio-Temporal Distribution of Rainfall in Bihar Using Precipitation Concentration Index

Abstract

Rainfall is a very significant meteorological variable influencing the hydrological cycle (through evaporation, surface runoff, river discharge, and groundwater levels). Its intensity can lead to extreme hydrological events such as floods and droughts in a region. Rainfall has a major impact on agriculture, the economy, food security, tourism, and other socio-economic aspects of a country. With evidence of climate change worldwide, rainfall variability has become increasingly prominent. These fluctuations are also visible in India and Bihar. As the majority of the rural population in Bihar is dependent on rainfed agricultural activities, insight into the spatial and temporal distribution of rainfall is very important. In this context, the paper examines inter-annual, seasonal, and decadal variations in rainfall distribution during 2010-2020 using the Precipitation Concentration Index (PCI). Rainfall data were collected from the Directorate of Economics and Statistics, Government of Bihar. Thereafter, PCI was calculated using the formula of Oliver (1980). The annual distribution of rainfall over the study period shows considerable inconsistency. Likewise, the seasonal PCI exhibits irregular to highly irregular rainfall distribution. However, rainfall distribution during the south-west monsoon season is almost uniform. The decadal PCI for the study period indicates irregular rainfall distribution over the region. The study utilises rainfall data for 2010-2020 from the Bihar Statistical Handbook of the Directorate of Economics and Statistics, Government of Bihar. District-wise monthly rainfall data for 2016 and 2021-2025 could not be retrieved because they were unavailable in the cited source, which constitutes a limitation of the study. The study focuses on the need to conserve water to maintain the hydrological cycle and environmental balance. The findings have important implications for drought and flood risk management and irrigation scheduling for improved agricultural planning and production.