Elevation of Tongguan,Sedimentation of the Lower Weihe River and the Sanmenxia Project

The Sanmenxia project has been founded for 40 years.The elevation at Tongguan,a datum point of the Lower Weihe River with a distance of 113km from the Sanmenxia dam,was raised by 5.2m in the first 4 years because of tremendous deposition. The serious deposition also occurred correspondingly on the Lower Weihe River.The project was forced to complete two reconstructions and change the operation mode of the reservoir.Up to now,the deposition on the Lower Weihe River has reached to 13.19×10 8m 3,which severely threatens the safety of the ancient capital Xian and the wide area along the Lower Weihe River.This paper points out that main reasons affecting the raising of Tongguan elevation. This paper also submits the proposals of the measures to lower the elevation of Tongguan and alleviate the deposition on the Lower Weihe River.