Transformation Characteristics and Mechanism of Blue and Green Water flows at Watershed and Typical Ecosystem Scale in China

The transformation of blue and green water is an important hydrological process at the watershed, which is an important supplement to the study of hydrological processes. The Soil and Water Assessment Tool (SWAT) was used to investigate the evolution characteristics of hydrological processes and the transformation mechanism at the watershed and ecosystem scales in the Dongjiang River. The results show that: (1) the annual average total water flows in the Dongjiang River Basin are 37.80 and 22.287 billion m³, respectively. The blue and green water flows during the wet season account for more than 75% of the total year. The blue and green flows of the grassland ecosystem increased significantly, with the most significant change in the downstream ecosystem. (2) From 1980 to 1990 and from 2010 to 2020, the Dongjiang River Basin experienced a transition from blue to green water flow. Blue water flow accounts for the majority of total water flow in the paddy field and dry cropland ecosystems, and green water flow changed to blue water flow from 1980 to 2010. (3) The correlation between blue and green flow and land use was weak throughout the year and during the wet season, but it was significant during the dry season. This study can serve as a model for the integrated management of water resources and ecosystems in the Dongjiang River Basin.