西江长洲枢纽下游近坝段水位下降特征及调控措施

受清水下泄、河道采砂、航道疏浚等因素影响,长洲枢纽坝下河床冲刷下切,枯水期水位下降明显。依据梧州水文站水位、流量资料,对长洲枢纽下游近坝段水位下降特征及影响因素进行分析,并对减缓坝下水位下降的调控措施进行了模型试验研究。研究结果表明:2012年梧州水文站设计水位较原设计值下降1.30 m左右;2000—2006年水位下降主要受自然演变和采砂等影响;2007—2012年水位下降的主要影响因素包括枢纽运行、航道整治、采砂等,其中枢纽运行带来的影响随着时间的推移将逐渐减小。经资料分析与模型试验研究发现:深槽回填、修筑壅水丁坝对减缓坝下水位下降的作用有限,而枢纽调节(提高下泄流量、增加外江分流比)对延缓坝下水位下降则效果相对明显。

Water level drop characteristics and its control measures for lower Near-dam reaches of Changzhou hydro-junction on the Xijiang River

Riverbed degradation and considerable falling of water level along the downstream channel of the Changzhou hydro-junction are due to the factors of released clear water， sand mining and waterway dredging, etc. According to the measured water level and flow discharge data from Wuzhou hydrometric station， the characteristics of the water level drop and its influencing factors on the lower near-dam reaches of the Changzhou hydro-junction are analyzed. In addition，the control measures to slow down the water level drop have been investigated in the physical model tests. The design water level given by the Wuzhou hydrometric station in 2012 was approximate 1.30 m lower than the initial design value. The water level drop is mainly due to the natural evolution and sand mining during the period of 2000 to 2006. Reservior operation， waterway regulation and sand mining were the main influence factors from 2007 to 2012, however, the impact on the reservoir operation will gradually decrease. Analysis of data and model test studies show that the deep pool backfilling and construction of the spur dikes play a limited role in slowing down the water level drop; by contrast, the regulation of the hydro-junction (including raising the discharge, and increasing the diversion ratio of the outside river channel) can considerably slow down the water level drop along the lower near-dam reaches.