三峡水库蓄水后荆江三口分流量计算方法

An Empirical Method of Diversion Discharge Calculation of the Three Major Outlets of Jingjiang River After the Impoundment of Three Gorges Reservoir

荆江三口河道(藕池河、虎渡河、松滋河)的水沙变化是江湖关系演变的重要内容,其分水分沙变化驱动江湖关系的调整,而且三峡水库蓄水后加剧了三口分流显著减少。通过三口河道的5个水文站2003~2018年水位与流量实测数据分析,考虑口门区水位下降等因素,得到三口河道分流量的经验公式,并量化荆江枯水位下降对三口河道分流量的影响。结果表明:三口分流量是口门区水位的函数,口门区水位下降引起三口河道分流量的同向减少。根据水位与流量关系得到三口五站简化分流量计算公式,进一步考虑口门区水位下降、河道宽度等因素,得到经验分流量与修正分流量的计算公式。采用2017~2018年实测日平均水位值与流量值,验证藕池河管家铺站与康家岗站的分流量经验公式,得到相对误差分别为4.5%与13.7%,验证虎渡河弥陀寺站的相对误差为11.5%,松滋河新江口与沙道观的相对误差值分别为4.5%与7.3%。可知荆江三口分流量的经验公式与实测值符合良好,可作为评估未来受荆江干流水位下降对荆江三口河道分流量的影响。

Water and sediment change of the Three Major Outlets River(Ouchi, Hudu, Songzi rivers) to the Dongting Lake from the Jingjiang River in the middle Yangtze River is an important part of the Jingjiang River-Dongting Lake relation which is adjusted by the water-sediment change. The Three Gorges Reservoir has resulted in the significant reduction of diversion discharge in the Three Major Outlets River. Hydrological data(water level and discharge) were collected in five stations(Xinjiangkou and Shadaoguan stations at the Songzi inlet, Mituosi station at the Taipingkou inlet, Guanjiapu and Kangjiagang stations at the Ouchikou inlet) in 2003-2018, to fit five groups of empirical formulae for the diversion discharge calculation incorporating the effect of water level reduction at the inlet. Result shows that the diversion discharge of the Three Major Outlets is mainly a function of the water level in the inlet area. The simplified formulae of diversion discharge obtained are further modified using the channel gradient and water level drop at the inlet area, and channel width. In 2017-2018, the measured data in Guanjiapu and Kangjiagang stations of Ouchi River were used to verify the predicted values, 4.5% and 13.7% of relative error, respectively, 11.5% in the Mituoshi station of Hudu River, and 4.5% and 7.3% in Xinjiangkou and Shadaoguan stations of Songzi River, respectively. In summary, five modified empirical formulae are in good agreement with the measured data, which can be used to estimate the change of diversion discharge of the Three Major Outlets River affected by future water level dropping of the Jingjiang River.