Modelling water and land resources synergy and trade-off in a major grain-producing area, China

How to coordinate and trade-off limited water and land resources to improve water resource utilization efficiency, increase food production capacity, protect ecosystems and enhance carbon sequestration remains a complex scientific issue. Taking the Sanjiang Plain as a case study area, water resources, crop planting structure and ecosystem distribution under conventional irrigation and water-saving irrigation scenarios are spatially coordinated and optimized through a distributed hydrological model (CWatM) and an improved a multi-objective optimization model with GridLandOpt method. The results showed that: (1) Water resources in the Sanjiang Plain fluctuated between 15.67 and 47.92 billion m 3 during the 2000–2019. (2) Compared with that before optimization, under the conventional irrigation mode, irrigation water use was reduced by 2.3 billion m 3 , total carbon sequestration increased by about 12.53 %, economic benefits decreased by 3.22 %. The planting structure of rice, corn and soybeans needs to be adjusted from the original 3:2:1–2.2:2.4:1.4. Wetland area increased by 2.34 %, ecological benefits increased by 12.53 %, and ecological connectivity improved by 2.79 %. (3) Compared with that before optimization, under the water-saving irrigation mode, irrigation water was reduced by 4.5 billion m 3 , total carbon sequestration increased by about 11.21 %. The planting structure of rice, corn and soybeans needs to be adjusted to 2.3:2.4:1.3. Wetland area increased by 0.81 %, ecological benefits increased by 0.80 %, and ecological connectivity improved by 2.30 %. The research results can provide technical support for the sustainable use of water resources, stable grain production and improvement of ecosystem service functions in China's major grain-producing areas. • Land use and irrigation issues threaten regional water resources and ecosystems, urging a balance between food production and ecology. • The available water resources cannot support the irrigation needs of 40 million acres of rice in the Sanjiang Plain. • An improved water-carbon-food-ecology model combined with GridLandOpt method was proposed. • Optimization cuts irrigation water use, boosts carbon sequestration and ecological benefits.