By Binita Pathak, Aniket Chakraborty, Shukla Acharjee, Niki Gogoi, Anindita Borah, Bikash Deka, Palash Dutta, Rizwan Rahman, Barsha Dutta, Jiban Saikia, Surajit Konwar, and Kalyan Bhuyan, Dibrugarh University, Assam, India

This study examines climate-driven dynamics of dry and wet spells across five Upper Assam districts — Dhemaji, Majuli, Lakhimpur, Sibsagar, and Dibrugarh —spanning 1950 to 2024, using ERA5-Land daily precipitation data. Dry and wet spells are defined based on consecutive days’ rainfall characteristics. A dry spell is considered a continuous period of at least five days during which daily precipitation remains below 1 mm, indicating sustained dry conditions. Conversely, an extreme wet spell consists of at least five consecutive days in which rainfall exceeds the 90^th percentile for wet days (≥ 1 mm), representing prolonged, intense rainfall events.

The livelihoods in these districts depend heavily on agriculture, pisciculture, and poultry, which are highly vulnerable to rainfall variability driven by climate change. Dry spell analysis reveals considerable interannual and spatial variability across the districts. The number of dry spell events ranges from 4 to 21 in Lakhimpur, with the highest in 2007, and from 5 to 17 in Majuli and Dibrugarh. Notably, Majuli and Dhemaji record the highest total dry spell days annually, with 142 and 135 days, respectively, highlighting prolonged drought-like periods even in riverine floodplain areas. Lakhimpur and Sibsagar generally experience shorter cumulative dry durations. These extended dry spells impose severe stress on crop production, water availability, and livestock health, intensifying the rural communities’ economic vulnerabilities. The variations in the frequency and duration of dry spells indicate increasing challenges in water resource reliability across Upper Assam’s rural landscapes.

In contrast, extreme wet spells —periods of rainfall above the 90^th percentile threshold for at least 5 consecutive days —occur less frequently but have significant localised impacts. Dibrugarh and Sibsagar recorded many years (42 and 48 years, respectively) without any extreme wet spell events, underscoring their episodic and irregular nature. Districts like Dhemaji and Sibsagar experience intense rainfall events with up to 14 consecutive days during extreme wet spells, potentially causing flooding and damage to croplands and infrastructure. The maximum annual 90^th percentile precipitation values reached above 32 mm in Dhemaji and Sibsagar, signalling intense rainfall bursts that contribute to flood risks. These events exacerbate land degradation and income instability for farmers, particularly affecting those whose livelihoods depend directly on agricultural output. This is reflected in the village survey conducted across 30 villages in these districts.The dual pressure from prolonged dry spells and episodic extreme wet spells not only disrupts agricultural calendars but also deteriorates soil health and water management capabilities, forcing many households to diversify livelihoods, migrate seasonally, or adopt indigenous coping mechanisms like the construction of elevated ‘Chang Ghar’ houses and food preservation technologies. Such strategies represent initial steps towards climate resilience but are insufficient without broader adaptive planning. The observations from this detailed dry and wet spell analysis strongly indicate that climate change is increasingly influencing precipitation variability and extremes in these Upper Assam districts. Prolonged dry spells are becoming increasingly prevalent, particularly in low-lying floodplain areas, escalating water scarcity and agricultural stress. Simultaneously, intense, sometimes prolonged, extreme wet spells contribute to flooding and related socioeconomic disruption. Effective adaptation requires focusing on district-specific vulnerabilities and enhancing water resource management, climate-resilient agricultural practices, early warning systems, and community-led adaptation initiatives to safeguard rural livelihoods in Dhemaji, Majuli, Lakhimpur, Sibsagar, and Dibrugarh. Hence, this assessment provides a critical scientific basis for policymakers and local stakeholders to prioritise interventions that mitigate the impact of shifting dry and wet spells on the socio-economic fabric of Upper Assam’s rural population.

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