长江宜昌河段低水位变化研究

Change in Yangtze Water Level along Yichang Stretch in Dry Season

长江宜昌站低水位的演变呈下降趋势,主要原因是河道采砂及水库拦砂引起下游河床冲刷下切,从１９７３年初至１９９８年初流量４ ０００ｍ３/ｓ时相应水位下降了１．１１ｍ。分析研究河道冲淤量、糙率、比降变化对低水位的影响,表明:三峡水库初期蓄水运用,本河段冲刷引起低水位下降的空间不大;宜昌低水位属长河槽控制,虎牙滩以下控制河段冲刷或采砂对该河段低水位下降影响较大;本河段淤积对低水位抬升影响较大。

The Yangtze water level at the Yichang stretch in dry season has been a trend of gradually decreasing, mainly due to riverbed scouring and deep cut caused by sand dredging and sediment detention of the Gezhouba reser voir. During the period from early in 1973 to early in 1998, the water level at Yichang in dry season, corresponding to the discharge of 4 000 m3/s> was generally lowered by 1. 11m. From the analysis on the impact of river channel erosion and deposition, channel roughness, and change in gradient of the water level, it has been shown that after the initial impoundment of the Three Gorges reservoir the amplitude of water level decreasing in dry season at this river section caused by riverbed scouring would not be great. The variation of water level at Yichang is actually affected by long river channel. Channel erosion or sand pumping at the river section below Huyatan will be the main factors to cause water level decreasing, while sedimentation over the section will bring about the rising of water levels in dry season.