A categorical quantification of the effects of vegetation restorations on streamflow variations in the Loess Plateau, China

Abstract

The Loess Plateau is the world’s largest and most typical loess accumulation area, and its recent change in vegetation cover has had significant hydrological effects. Understanding the impact of vegetation restorations in this region is essential for local water security and the sustainable development of Loess regions. This investigation concentrates on the upper basin of the Beiluo River, a representative watershed on the Loess Plateau. Using the coupled application of the hydrological model and the DFI baseflow segmentation method, as well as the analysis of extreme land cover transfer scenarios, the impact of typical land cover transition categories on the watershed runoff process on the Loess Plateau is systematically evaluated. Depending on the change in runoff introduced by the unit transfer area, a rapid estimation method for river runoff in the Loess Plateau is proposed. The results show that base flow contributes considerably to river runoff on the Loess Plateau, and the SWAT-DFI coupling has substantially improved the hydrological model’s simulation accuracy during the dry season. From 1985 to 2020, the primary land cover transfer categories in the upper basin of the Beiluo River were agricultural land to the forest (AL2F), agricultural land to pasture (AL2P), pasture to agricultural land (P2AL), and pasture to the forest (P2F), of which P2AL is the only form of transfer that increases discharge. From a spatial perspective, the intensity of the impact of AL2F and AL2P on runoff is greater in the upstream region than in the downstream region. From the standpoint of land cover transfer type, the intensity of runoff depth change caused by transfer per unit area varied, which was primarily manifested by the fact that the impact of AL2F was greater than that of AL2P, both of which were greater than that of P2AL and significantly higher than that of P2F. The proposed rapid estimation method based on land cover transfer equivalents can rapidly estimate river runoff changes and spatial distribution under various land cover change conditions, which is critical for understanding the hydrological effects of vegetation restoration on the Loess Plateau. The quantified effect of land cover change on runoff and the proposed quick estimation approach can serve as benchmarks for water security and ecological restoration on the Loess Plateau and other loess accumulation areas around the globe.