Exploring the spatiotemporal distribution and driving factors of vegetation canopy rainfall interception in the Qilian Mountains, Northwest China

Vegetation canopy interception is a key component of hydrological fluxes, and directly impacts the potential water resources available as ecosystems inputs, especially for vital water sources in arid and semiarid regions with limited water. However, determining the spatiotemporal variations in canopy interception and its driving factors in these regions remains challenging due to limited field measurements and complex natural conditions. In this study, we take the Qilian Mountains region, the water source of Hexi Corridor, as an example and employ the remoted sensing (RS)-Gash model to quantitatively explore the spatiotemporal distribution and driving factors of vegetation canopy rainfall interception during the growth seasons from 2000 to 2020. The results showed that the mean interception loss is 61.56 mm in the growth season, accounting for 14.69 % of the total rainfall. Spatially, the interception loss gradually decreased from the southeast to the northwest, and temporally, the interception loss increased from 2000 to 2020. From May to September, the interception loss first increases and then decreases, with a peak in July or August. In terms of vegetation type, the interception loss during the growth season is highest for the shrub (80.83 mm), followed by crop (66.52 mm), forest (61.27 mm), and grass (37.63 mm). The mean interception ratios of shrub, forest, crop, and grass are 17.62 %, 14.97 %, 14.04 %, and 12.14 %, respectively. The dominant factors influencing spatial variations in canopy interception are the fraction of vegetation cover, rainfall days, rainfall amount, potential evaporation, and leaf area index. These findings indicate that ongoing vegetation protection in the Qilian Mountains is vital to ensure the sustainability of water resources in the Hexi Corridor, which is crucial to maintaining water resources security in the arid and semiarid regions of northwest China.