Spatial and temporal variability of blue/green water flows in typical meteorological years in an inland river basin in China

Blue/green water closely links the water cycle and ecological processes. On the watershed scale, how blue/green water flows vary among different typical meteorological years (dry years, wet years, and normal years) remains poorly reported. To analyze the spatial and temporal variability of blue/green water in typical years in the Heihe River Basin, typical meteorological years were obtained by using the standardized precipitation index (SPI) and the precipitation anomaly index (H) and simulated blue/green water flows using the Soil and Water Assessment Tool (SWAT). The typical meteorological years are often not consistent from upstream to downstream in the Heihe River Basin, except in 1978 and 1998. Furthermore, the blue/green water quantities in wet years (1998, 27.93 billion m³) are higher than in dry years (1978, 16.80 billion m³). The green water coefficient (GWC) is more than 87.5% in the entire river basin. There was a negative correlation between the GWC and the degree of dry and wet in the typical meteorological years, as the drier the climate, the higher the GWC. This study provided an understanding of green/blue flows in different reference years to inland river green and blue water resource management.