Spatio-temporal Rainfall Dynamics over the Hyderabad–Karnataka Region, India: A Multi-scale Non-parametric Trend Assessment

Abstract

Rainfall variability plays a crucial role in determining water availability and agricultural sustainability, especially in semi-arid regions. This study examines spatio-temporal rainfall trends across the Hyderabad–Karnataka region using a multi-scale framework based on the Mann–Kendall test and Sen’s slope estimator. Trends are analysed at annual, monthly, and seasonal scales to characterise long-term changes and intra-annual variability. At the annual scale, Yadgir shows a statistically significant increasing trend (Sen’s slope = +6.20 mm/year, Z = 2.46, p = 0.014), while Ballari (+3.32 mm/year, Z = 1.57), Raichur (+1.19 mm/year, Z = 0.70), and Kalaburagi (+0.98 mm/year, Z = 0.29) show non-significant increases. Bidar (−2.36 mm/year, Z = −0.62) and Koppal (−0.45 mm/year, Z = −0.13) show non-significant decreases. Monthly analysis reveals stronger localised signals, including significant increases in Ballari in May and June, Kalaburagi in April, Koppal in May, and Yadgir from March to May. Seasonally, significant Kharif increases occur in Ballari and Yadgir, whereas the Rabi season shows weak negative trends across all stations. Summer rainfall increases significantly in Ballari, Raichur, and Yadgir. Overall, the findings indicate pronounced spatial heterogeneity and scale-dependent rainfall variability, with clearer changes at monthly and seasonal scales than at the annual scale.