Suspended Sediment Rating Curves for Heterogeneous Karst Watersheds

Abstract

Water-sediment relationships are complicated in karst areas of southwest China due to regional extreme climate, special geological conditions, shallow soil layer, heterogeneous geomorphology and landscape. However, the relative influence of climate, lithology, soil, topography and landscape on sediment-water relationships in heterogeneous karst watersheds is still unclear. In this paper, sediment rating curves (SRCs) of 40 heterogeneous karst watersheds in southwest China during 2009–2012 were calculated to explore the spatio-temporal variation of *coefficient a* and *index b* of SRC. The partial least squares structural equation model (PLS-SEM) was used to decouple the effects of climate, lithology, soil, topography and landscape on *coefficient a* and *index b* of SRC. Results showed that *coefficient a* and *index b* of SRC exhibited no significant temporal variations during 2009–2012 while varying substantially among different watersheds. The comprehensive effect of the five factors explained 51% and 49% of the variations in *coefficient a* and *index b*, respectively. Climate, soil and topography were the first-order variables influencing *coefficient a*, with a corresponding direct positive effect of 0.37, 0.46 and 0.60, respectively. They showed no significant effects on *index b*. In contrast, lithology and landscape exhibited significant direct effects on *index b*, that is, −0.42 and −0.54, respectively. This study can facilitate a better understanding of sediment transport mechanisms and guide integrated watershed management and soil erosion control in karst landscapes.