Analysis of the effects of vegetation changes on runoff in the Huang-Huai-Hai River basin under global change

Vegetation is one of the critical environmental factors driving the hydrologic cycle. The impact of vegetation change on runoff is a hot issue. As a pronounced greening region, the Huang-Huai-Hai River basin (HHHRB) was selected as the studying area. Based on long-term (1982-2016) hydro-meteorological and Normalized Difference Vegetation Index (NDVI) datasets, the spatial and temporal change in NDVI was detected using Mann-Kendall's test methodology. The relationship between NDVI and the parameter ω of Budyko-Fu's model was analyzed using an empirical formula and an elasticity method. Taking the parameter ω as a link, the impact of NDVI change on runoff in HHHRB was investigated with the chain rule for derivatives of complex functions. Several new findings were investigated: ① There was a statistically significant increasing trend in NDVI during the last 35 years over HHHRB. ② An increase in NDVI would increase the model parameter ω, thereby leading to a decrease in the runoff. ③ There might be an average reduction of 8.3% in runoff as a 10% increase in NDVI in the HHHRB. ④ The runoff was more sensitive to NDVI change under drier climate and sparser vegetation conditions. The results could improve the understanding of the mechanism of the water cycle in a changing environment and might provide scientific and technological support for water resources planning and vegetation management.