303 / 2024-02-29 12:45:19

Assessment of effective green water resources in the Yangtze River Basin based on dynamic crop coefficient

effective green water; water resources assessment; crop coefficient; SWAT model; Yangtze River Basin

The traditional water resources assessment mostly focused on the blue water that can meet the consumption of social and economic systems, ignoring the green water that can be used by plants. This traditional approach cannot fully reflect the full connotation of water resources, resulting in the lack of hierarchy in the caliber of the water resources assessment and directly leading to a large error in the division of effective green water. In this work, we presented an effective green water resource assessment method based on dynamic crop coefficient. The dynamic crop coefficient was introduced into the SWAT model to improve the accuracy of green water simulation and crop growth process simulation in the Yangtze River Basin. We validated the simulations against observed leaf area index, runoff, and evapotranspiration in sequence, and then the dynamic calculation of vegetation coverage was carried out to realize the division of effective green water resources in the Yangtze River Basin based on dynamic coverage calculation. The results showed that: (a) the SWAT model is an ideal tool to simulate crop development and runoff under given climate conditions; (b) green water was the main water resource in the Yangtze River Basin. From 2000 to 2019, the average amount of green water resources was 1,236.51 billion m³, accounting for 68.59% of the total water resources in the whole basin and about 1.62 times of blue water. Among them, vegetation transpiration accounted for the highest proportion (938.51 billion m³), accounting for 75.9% of the total green water resources in the whole basin; (c) according to the division method of effective green water resources and the distribution of green water resources in different land use types, the effective green water resources in the Yangtze River basin were calculated to be 1,114.1 billion m³, accounting for 90.1% of the total green water resources in the basin, and the ineffective green water resources were 122.41 billion m³; (d) the evaluation method proposed in this study improved the accuracy of effective green water resources assessment, broadened the caliber of water resources assessment, and can provide more effective guidance for more effective utilization and scientific management of water resources.