Climate Variability and Extremes in Indian River Basins: Trends, Regional Disparities, and Urban Risk Assessment

Climate change is increasing the frequency and intensity of extreme weather events, posing substantial risks to densely populated countries in the Global South, particularly India. Heatwaves, droughts, and floods threaten water resources, agriculture, ecosystems, and human livelihoods especially heightening the vulnerability of urban areas. To mitigate these impacts, it is essential to assess climate variability trends, identify regional disparities, and evaluate associated risks. Thus, this study analyzes climate extremes across 22 river basins in India from 1951 to 2023, using 20 extreme climate indices for precipitation and temperature. The spatial and temporal trends of precipitation and temperature are evaluated using the Modified Mann-Kendall (MMK) test, Sen’s slope estimator, and Innovative Trend Analysis (ITA). The vulnerability of 592 Indian cities to extreme climate events is ranked using the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). The findings reveal significant regional disparities. Half of the river basins show declining monsoon and annual precipitation, with snow-fed basins like the Indus and Ganga experiencing reduced post-monsoon rainfall. Rain-fed basins of Godavari and Narmada are facing longer dry spells, while the Indus basin is experiencing more intense, short-duration rainfall. Maximum temperatures are rising across most regions, although colder winters persist in the eastern basin of Brahmani and Baitarani. An interesting observation is the lack of significant trends in precipitation and temperature in smaller river basins. Further, the urban risk analysis highlights Ganga (largest river basin in India) as most vulnerable, inhibiting 22 out of 25 most-affected cities. In contrast, Bongaigaon town, situated in the Brahmaputra River basin, was found to be the least affected. The river basin of the East flowing river between Pennar and Kanyakumari showed the lowest risk of increasing climate extremes, with six of the top 25 least-affected cities situated in this region. This study combines diverse climatic datasets and robust methodologies to shed light on regional vulnerabilities and urban risks, offering a foundation for designing targeted adaptation strategies tailored to the needs of different regions in India.