中文摘要：

利用HEC-RAS水动力模型，对三峡水库运行初期（2007-2008年）澎溪河流域回水区段的一维水动力特征进行了模拟研究。在其库湾、河汉、大面积淹没区或消落带等水域，通过建立虚拟堤坝、划分成水体主要输送干道和储水区域的方式对河道进行概化；经参数率定与模型验证，确定糙率取值范围为0．27-0．35，所建立的模型具有较好的模拟精度。采用准非恒定流的方式对研究期间水动力过程进行模拟演算发现，低水位状态下澎溪河回水区上游河段断面平均流速将超过0．5m／s，接近天然河道；而在高阳平湖处形成独立且相对封闭的大面积浅层淹没区；高阳大桥以下河段随断面积的加大而流速放缓；高水位状态下，不同河段间流速无显著差异，深水河道型水库特征显著。研究期间，建模区域总库容、水体滞留时间变化范围分别为8．26×10^8-2．51×10^8m^3，157．0-3．8d。库容变化主要受河口水位的影响，水体滞留时间则在径流和水位的双重影响下波动明显。研究期间，17．8％的水体滞留时间数据样本显示澎溪河回水区呈过流型水库特征，主要集中于夏季汛期；82．2％的水体滞留时间数据样本显示其呈过渡型水库特征。

英文摘要：

A 1D hydrodynamic model on Pengxi Backwater Area （PBA） in the Three Gorges Reservoir during its preliminary operation period （2007-2008） is set up based on HEC-RAS. In the large submerged area or water fluctuation zone, virtual levee is set up in the model between the conveyance channel and the storage area. The Manning＇s n in PBA is calibrated and selected in the range of 0.27 - 0.35. Calibrated model has good modeling results. Quasi-Steady simulation approach is applied to calculate 1D hydrodynamic condition in the PBA during the study period. Analysis on the hydrodynamic condition in the PBA show that in the low-water-level operation stage, average velocity of upper reach in PBA will exceed O. 5 m/s, which is close to natural river. The Gaoyang Lake is formed as a relative independent and semiclosure dam-lake in the middle reach of PBA. Due to the enlarged cross section, the velocity at downstream of PBA is significantly decreased. In the high-water-level operation stage, no remarkable difference ofvelocity among cross sections in the PBA, indicating a significant hydrological characteristic of deep river- based reservoir. The variation of reservoir capacity and hydraulic retention time in the PBA is 8.26 ×10^8 - 2.51 × 10^8m^3 and 157.0- 3.8 d respectively. The variation of reservoir capacity in PBA is impacted by the water level fluctuation more significantly. The hydraulic retention time in the PBA is impacted by both and river discharge dually. Frequency analysis show that 17.8% of hydraulic retention time data in the PBA is showed to be overflow reservoir type and 82.2 ~ of that data showed to be transition type.