松滋河西支分流能力变化分析

Analysis of Diversion Capacity Change of West Branch of Songzi River

摘要: 长江中游河段荆江三口分流入洞庭湖，在三峡水库蓄水后荆江三口年径流量占枝城分流比约为12%，其中，松滋口分流比为最大，占7%左右。受荆江干流水沙变化、上下游水利工程兴建等因素影响，荆江三口分流量沿时程逐渐减小，松滋口沿时程总体也呈现减小，但减小的幅度及速率为最小。松滋河经过大口之后又分为松滋河东支与西支，东支分流比衰减速度相对较大，西支分流减小的速度相对缓慢。利用荆江河段的水文及河道观测数据，分析了松滋河西支1956年来各时段分流量及分流比的变化，以枝城水文站流量为基准，分析了各流量级新江口站分流量及分流比的变化，从新江口水文断面河道形态尺度来分析过流能力变化，得出松滋河西支在枝城10,000 m³/s分流能力减弱、在枝城20,000 m³/s分流能力基本没有变化、在枝城30,000 m³/s分流能力明显增强的结论。

Abstract: Jingjiang reach in middle Yangtze River is diverted at the three outlets into the Dongting Lake. After the impoundment of the Three Gorges Reservoir, annual runoff of the three outlets accounted for the pro-portion of Zhicheng Station is about 12%, of which Songzi outlet is the highest, accounting for 7%. Due to the water and sediment changes in Jingjiang reach and water conservancy project construction, the discharge of three outlets gradually decreased, and the attenuation magnitude of Songzi outlet’s diversion discharge that gradually decreased is the minimum of three outlets. Songzi river is divided into the east branch and the west branch downstream Dakou. The flow diversion ratio of east branch is decreasing faster than the west branch. To reveal variation characteristics of discharge and flow diversion ratio in the west branch in different periods since 1956, observation data of hydrometric stations in Jingjiang reach and geomorphology of river channel were adopted. Variation of discharge and flow diversion ratio in Xinjiangkou station in different levels of discharge has been analyzed based on the discharge in the Zhicheng hydrological station. Using the geomorphological scale of Xinjiang outlet river channel, flow capacity in the west branch was analyzed. At the 10,000 m³/s, 20,000 m³/s and 30,000 m³/s in Zhicheng hydrological station, the flow capacity in the west branch weakened, unchanged and enhanced, respectively.