Focus on Downstream: A Sociohydrological Approach to Improve Policy Adaptation for Farmers

Farmers in South Asia, home to a significant portion of the global population, rely heavily on agriculture for their livelihoods, with water resources playing a crucial role in sustaining this sector. Canal irrigation systems are integral to agricultural productivity in these regions, yet disparities in water distribution between upstream and downstream areas present significant farmer-level challenges for policy adaptation to achieve sustainable agricultural water management. This study assesses the socio-hydrological and agronomic dynamics of canal irrigation in a South Indian region, focusing on supply-demand interactions and their impact on crop choice.

We developed a coupled crop-hydraulic modeling framework that simulated crop water demands using AquaCrop and canal discharge using PCSWMM for two seasons—Kharif and Rabi—covering high-demand crops like paddy and low-demand crops like cotton. Crop water demand was calculated by integrating AquaCrop-derived requirements with geospatially mapped cultivated areas. Canal discharge volumes were monitored using 70 water level sensors, with data assimilated into the hydraulic model for calibration. Subsequently, the supply and demand volumes for both regions were compared, and the following results were derived.

Results revealed that upstream farmers receive approximately 70% more supply than their estimated demand. Therefore, they predominantly cultivate water-intensive crops like paddy and are reluctant to adapt to new methodologies. Conversely, downstream farmers, who receive 80% less water supply when compared to their demand, were willing to adapt to new agricultural methods. This could be attributed to the observation that downstream farmers prioritize risk mitigation over yield maximization. Overall, integrating socio-hydrological and agricultural approaches reveals downstream farmers as ideal candidates for initial policy implementation due to their readiness to adapt. Policies focusing on equitable water distribution, financial incentives for adaptive practices, and investments in water management infrastructure can enhance resilience and promote long-term overall regional agricultural sustainability.