Measurements of Erosion Rate of Undisturbed Sediment under Different Hydrodynamic Conditions in Lake Taihu, China

Sediment erosion and nutrient release play a significant role on the degradation of water quality and eutrophication in large shallow lakes. Lake Taihu, the third largest freshwater lake in China, is suffering severe eutrophication and internal nutrient release. In this paper, sediment cores were sampled in different lake regions to determine sediment properties (e.g. particle size and bulk density), nutrient concentrations in the sediment, etc. Flume experiments were developed to examine the sediment erosion rate by using the undisturbed sediment cores under different hydrodynamic conditions in Lake Taihu. The results showed that the sediment properties exhibited great spatial heterogeneity. Particle sizes decreased with increasing depth of sediment thickness. Sediment bulk density increased with sediment depth. TN concentration increased with sediment depth, while TP concentration didn't show a similar trend in different sampling sites. Erosion rate is a function of particle size, bulk density, and shear stress. It decreased with increasing sediment depth and decreasing flow velocity. The erosion depth in this study was less than 1cm under the flow velocity of 5 to 30 cm/s, indicating that unidirectional flows have little impact on sediment erosion in Lake Taihu.