Figure 10 Typical cross-sectional profiles of the LYR at (a) Weicheng section and (b) Yangxiaozhai section.
During the period 1986-1999, the river channel seriously shrank and deposited sediment; the width of the main channel was obviously reduced with decreases ranging from 300 to 2000 m, and the capacity of flood discharge also decreased (Shen et al., 2000). During the operation of the XLD reservoir and the implementation of the WSRS, low-sediment concentration flows were released from the reservoir, which continuously scoured the riverbed and gradually widened and deepened the main channel. The width of the main channel increased by 2600 m at the WC section and 780 m at the YXZ section from 2000 to 2017.
We measured the changes in the widths of the main channel and the floodplains during 2000-2017, as shown in Figure 11. Width changes in the main channel vary greatly from HYK to GC; taking the DBT section as the boundary, the widths of the main channel from HYK to DBT are between 400-2300 m, and the widths of the main channel are concentrated the range from 500-1000 m in the DBT - GC reach. Width changes in the floodplain can be divided into three parts: i) the width of the HYK - WC reach increases gradually downstream, ii) the width of the WC - DBT reach is relatively stable and shows little change along the river, and iii) the width of the DBT - GC reach decreases gradually along the river.