Separating the impact of check dams on runoff from climate and vegetation changes

• Check dam is the largest contributor to runoff reduction. • Runoff reduction is piecewise linearly correlated to the increase in storage capacity. • Cumulative runoff reduction increased rapidly before around year 2000. • Cumulative runoff reduction increased slowly as sediment trapping capability faded. Check dam is an important soil and water conservation engineering measure for the prevention and control of soil erosion on the Loess Plateau in China. However, how the check dams influence runoff at different catchments remains unclear. This study uses a modified hydrological model (SWAT-PML) to quantitatively distinguish the impact of check dams on the runoff from climate and vegetation changes and to identify the relationship between runoff reduction and check dam storage capacity for six check dam influenced catchments on the Loess Plateau. Results show that compared to the slow increase before 1997, leaf area index (LAI) significantly ( p < 0.01) increased in these six catchments after 1997. The construction of check dams started before 1997 in five catchments, and reached a peak between 2005 and 2010 for all six catchments. Check dam construction and vegetation greening reduced runoff in all catchments, while climate change reduced runoff in three catchments but increased runoff in the remaining three. Among the impact factors, the check dams contributed the most to runoff change. Furthermore, the cumulative reduction amount of runoff grew rapidly with the development of check dam storage capacity before the turning point (around the year 2000), while it turned to a slow increase after the turning point. This research provides reference and guidance for the construction and management of soil and water conservation measures, as well as the planning and sustainable utilization of water resources on the Loess Plateau.