144 / 2024-02-20 15:02:05

RESERVOIR SEDIMENTATION OF THE XIAOLANGDI RESERVOIR AND ITS INFLUENCE ON CHANNEL IN THE LOWER YELLOW RIVER

reservoir sedimentation, Xiaolangdi Reservoir, channel erosion, the Lower Yellow River, the bankfull discharge, water level, efficiency of channel erosion

Based on the field data of the Xiaolangdi Reservoir and the Lower Yellow River from 1999 to 2021, this paper analyzes reservoir sedimentation and its Influence on channel erosion in the Lower Yellow River during the 22 years operation of the Xiaolangdi Reservoir. The result shows that from 1999 to 2021, the total deposition of Xiaolangdi Reservoir reached 3.347×10⁹m³，only 26.0% of the incoming sediment load could be sluiced out of the reservoir. In the post-flood season of 2021, the vertex of deposition delta of Xiaolangdi Reservoir reached 7.74 km away from the dam.

From Oct. 1999 to Oct. 2021, the Lower Yellow River unavoidably suffers erosion, the whole erosion of the river amounted to 3.08×10⁹t. The erosion in flood season is 61.1% of the annual erosion, about 84.6% of the erosion occurs in upper reach of the river covering a length of 468 km (the wandering reach and the transition reach), in which, 69.0% is in its upper part of 286 km (the wandering reach). The efficiency of channel erosion (amounts of erosion caused by unit water out of the reservoir) in 2000 and 2001 reached to 7.44 kg/m³ and 7.19 kg/m³, while in 2018 the erosion efficiency was only 1.97kg/m³. The channel erosion made the cross-section narrower and deeper, dropped the water level at the same discharge and increased the bankfull discharges from 1800 m³/s in 2002 to 4600 m³/s in 2021. The bed armoring has been apparently appeared, the surface bed materials in 2021 were nearly two times as coarse as those in 1999.

Furtherly, research shows that, the increased flow energy coursed by 1m³ sedimentation in the Xiaolangdi Reservoir are capable to scour 0.92 ton sediment in the downstream channel, therefore, the sediment detention by reservoirs are still one of the most effective measures for sedimentation reduction in the Lower Yellow River.