Revegetation impacts on the flow characteristics in the Loess Plateau

Loess Plateau, China. Revegetation has been one of the most effective nature-based solution for carbon sequestration. However, its impacts on local water resources vary across places, and is especially controversial in arid/semi-arid regions. This study analyzed spatial and temporal variability of flow characteristics, including baseflow index (BFI), flow duration curves (TFDC, FFDC, SFDC), and recession curves, from 85 catchments in the Loess Plateau (LP), an arid/semi-arid region with substantial revegetation activities for over 20 years. Our results suggested that while the baseflow index (BFI) had strong correlations with the shape parameter and scale parameter of total flow duration curves (TFDC), fast flow duration curves (FFDC), and slow flow duration curves (SFDC) before revegetation, its influence on fast flow disappeared afterwards, indicating substantial change in fast flow events. Event scale analysis of the recession curves suggested more stable recharge after revegetation, but the influences on the nonlinearity were complicated. Besides the impacts of climate, the elevated vertical heterogeneity in soil hydraulic property due to revegetation is likely to contribute to the change in nonlinearity of recessions. The contrasting profile of hydraulic property could enhance infiltration and generate shallow storage during rainfall event, resulting in a new runoff generation mechanism, the saturation excess runoff. This potential emergence of saturation excess runoff could be one of the explanations of the change in recession nonlinearity. More comprehensive field measurements are needed to evaluate the vegetation impacts to examine the hypothesis of the shift in runoff generation mechanism. Our findings could provide more comprehensive understandings for the revegetation impacts on local water cycles in arid/semi-arid regions for sustainable water resource management. • flow characteristics in 88 Loess Plateau catchments was investigated. • Baseflow impacts was significant before revegetation, weakened afterwards. • The elevated vertical heterogeneity in soil hydraulic property may contribute to the change in nonlinearity of recessions.