Long-term Analysis of Rainfall Variability and Drought Characteristics for Climate-resilient Agricultural Planning in Ballari District, Karnataka, India

Abstract

Rainfall variability and drought occurrence are major challenges affecting agricultural productivity and water resource management in the semi-arid regions of India. The present study was undertaken to analyse long-term rainfall variability, rainfall anomalies, drought characteristics and rainfall trends in Ballari district of Karnataka and to assess their implications for agricultural sustainability. Daily rainfall data from the Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS) dataset for the period 1981–2025 were used for the analysis. Annual rainfall variability was evaluated using descriptive statistical measures, while rainfall anomalies were assessed using the Rainfall Anomaly Index (RAI). Drought characteristics were examined using the Standardized Precipitation Index (SPI-12), and long-term rainfall trends were analysed using the Mann–Kendall test and Sen’s slope estimator. The results indicated that the long-term mean annual rainfall of Ballari district was 511.25 mm, with substantial interannual variability. The coefficient of variation was 24.07%, reflecting considerable year-to-year fluctuations in rainfall. Rainfall classification revealed that, out of 45 years analysed, 12 years were classified as deficit rainfall years, 21 years as normal rainfall years, and 12 years as excess rainfall years. RAI analysis demonstrated the recurrent occurrence of both wet and dry anomalies, highlighting the highly variable nature of rainfall in the district. SPI analysis further indicated the occurrence of recurring drought conditions, with several years experiencing moderate to severe moisture deficits. Trend analysis using the Mann–Kendall test and Sen’s slope estimator showed no statistically significant long-term trend in annual rainfall, suggesting that climatic risks in the district are primarily associated with rainfall variability and extreme events rather than systematic changes in mean rainfall. The study concludes that agriculture in Ballari district remains highly vulnerable to rainfall variability, drought recurrence and extreme rainfall events. Strengthening climate-resilient agricultural practices, improving soil and water conservation measures, promoting rainwater harvesting and enhancing weather-based agro-advisory services are essential for improving agricultural sustainability and resilience under changing climatic conditions.