Assessment of Long Term Impact of Gandak Canal Irrigation Project on Cropping Pattern and Development in North Bihar, India

India hosts one of the largest canal irrigation networks in the world, influencing not only the agrarian economy but also the broader trajectory of rural development. Canal irrigation provides water security to more than 200 million people and has significantly reshaped India's economic geography by inducing substantial agricultural and structural transformations both within and beyond irrigated zones. The study aims to provide comprehensive insights for improving resilience and sustainability in the canal-command agricultural regions of the Gopalganj district of Bihar. This qualitative field-based study explores the socio-economic and agronomic impacts of the Gandak Canal Irrigation Project in Gopalganj district, Bihar, India, within the broader contexts of climate change and rural development. Employing a purposive sampling approach, the study engaged 360 diverse farmers, labourers, Panchayat members, and through semi-structured interviews and group discussions conducted during the 2024–25 agricultural year. Data collection and analysis focused on understanding local perceptions of irrigation-driven changes in agriculture, livelihood patterns, and environmental dynamics. Findings reveal a significant transformation in land use and cropping patterns since the canal's implementation. The assured availability of surface water has led to a 50% increase in paddy area and an 83.3% rise in wheat cultivation, driven by the adoption of high-yielding varieties. Vegetable farming also expanded by 260% and sugarcane by 150% facilitated by improved irrigation and demand. Fodder crop area increased by 50%, supporting livestock-based mixed farming systems. Conversely, pulses and oilseeds saw a 40% decline each, largely due to market neglect, input limitations, and displacement by more remunerative crops While the project has substantially boosted productivity and economic opportunities, it raises critical concerns regarding sustainability, ecological balance, and nutritional security. The shift toward water-intensive and input-responsive crops, combined with growing climate risks such as erratic rainfall, rising temperatures, and soil degradation, necessitates a more integrated and adaptive approach. To ensure long-term sustainability, the study recommends promoting crop diversification, integrated water and nutrient management, and institutional support for underrepresented crops like pulses and oilseeds.