Projected changes in water demand and potential water savings for US grown rice under alternate wetting and drying practice

Abstract

In the United States (US), rice production accounts for roughly 10% of global rice trade and contributes more than $34 billion annually to the national economy. Although rice is a critical staple crop for global food security, it has traditionally been cultivated under continuous flood irrigation. Farming practices that more effectively use water resources while maximizing yield can help buffer impacts of extreme weather events and accommodate increased consumer demand. Accurately quantifying the water and irrigation requirements of US rice systems is therefore essential for improving on-farm water-use efficiency and advancing agricultural sustainability. This study evaluates the water-use implications of alternate wetting and drying (AWD) irrigation compared with conventional continuous flooding by applying a modified version of the ORYZA crop model for US conditions. Using a broad range of weather datasets, we assess both short-term and long-term changes in simulated crop water demand, irrigation requirements, and water-use efficiencies. Results showed that adoption of AWD has the potential to reduce water use while sustaining high yields, although the effectiveness of this practice varies significantly across the production areas. Under baseline conditions, AWD reduced irrigation demand by an average of 142.2 ± 18.2 mm in the Mississippi Delta and Gulf Coast regions. Projections indicate that AWD could provide additional water savings, reaching up to 84.9 ± 6.7 mm under the SSP5–8.5 scenario by the end of the century. These findings, presented with their associated uncertainty ranges (± SD) across multiple Earth System Models, provide new insight into blue-water use in US rice production. This study highlights the importance of utilizing data-driven methodologies to identify irrigation management strategies for maximizing productivity and resilience.