Attribution of blue and green water changes in Honghe River Basin based on revised Budyko complementary relationship method

Quantifying the impacts of climate variability and land cover change on blue and green water resources is conducive to the scientific planning and management of water resources in river basins, as well as the implementation and assessment of ecological restoration projects. In the Honghe River Basin, based on hydro-meteorological data from 1961 to 2022, the changing trends of hydrological and meteorological sequences and the mutation points of blue and green water sequences were analyzed by means of statistical theories. The concept of blue and green water was introduced to modify the Budyko hydrothermal coupling equilibrium framework. The elasticity coefficients of blue and green water to environmental impact factors were calculated, and an attribution analysis was conducted using the complementary relationship method. The results show that: ① Precipitation and runoff in the Honghe River Basin show an upward trend. The year 1995 is determined as the mutation year in the study basin according to our comprehensive analysis of the changing characteristics of hydro-meteorological time series data; ② Blue water is the most sensitive to changes of precipitation, while green water is the most sensitive to changes of the underlying surface. Changes in the underlying surface are the main factors affecting the changes in blue and green water in the basin, with contribution rates of 89.27% and 112.45%, respectively. ③ Changes in the underlying surface are the dominant factor driving the variations in blue water and green water in the basin, primarily manifested as changes in land use types of the underlying surface. Additionally, the construction of water conservancy projects also has a certain impact on the changes in blue water and green water.