Tree planting and soil conservation measures have strongly attenuated storm runoff responses on the Chinese Loess Plateau
Shaozhen Liu, Hansjörg Seybold, Ilja van Meerveld, Yunqiang Wang, James W. Kirchner
Abstract
Land restoration often consists of tree planting and soil conservation measures to improve infiltration and reduce erosion. Tree planting has been shown to reduce annual water yields, but its effects on peak runoff during intense storms have been difficult to determine, particularly in large basins. Soil conservation measures, such as check dams, terraces, and runoff-trapping soil contours, are expected to reduce peak flows but their effects likely depend on precipitation intensity and antecedent moisture conditions. Here we use Ensemble Rainfall-Runoff Analysis to test how tree planting and soil conservation measures have affected storm runoff responses in five large-scale basins (774–17,180 km 2 ) on the Chinese Loess Plateau. We find that peak runoff responses decreased (by up to 86 %) following tree planting and associated soil conservation measures, and that this decrease was proportional to the percentage increase in the Leaf Area Index. The attenuation of peak runoff was much larger than the decrease in average runoff or median runoff, and was largest for high-intensity rainfall events. This implies that the decrease in peak runoff response was not primarily caused by increased canopy interception or drier soils, because these would be expected to have a larger effect on lower-intensity events. Instead, we hypothesize that the main mechanisms are likely to be reductions in runoff-generating areas and increases in infiltration.