三峡水库香溪河库湾沉积物粒度空间分布特征

SPATIAL DISTRIBUTION CHARACTERISTICS OF SEDIMENT GRAIN SIZE IN XIANGXI BAY OF THE THREE GORGES RESERVOIR

三峡水库蓄水以来,库区支流水动力条件改变,库湾泥沙来源及沉积规律发生变化。以三峡库区典型支流香溪河为例,开展了三峡水库香溪河库湾上覆水环境条件和沉积物理化性质野外监测和室内分析,分析了库湾分层异重流的特殊水动力背景下表层沉积物粒度空间分布特征。结果表明:香溪河库湾沉积物优势粒级为砂粒和粉砂,不同水位运行期沉积物粒度组分空间变化明显。消落期黏土组分由库湾下游向上游呈逐渐减小的趋势;汛期黏土呈中游高,上、下游低的趋势。表层沉积物粒度空间分布受水动力影响,沉积环境受到长江干流、上游来流、水温和地质等条件的共同影响。

Since the impoundment of the Three Gorges Reservoir(TGR),the dynamic condition of the branch flow in the reservoir has changed,and the sediment source and deposition law do.In this research,the Xiangxi Bay(XXB),a typical tributary of the TGR is the key object,the field monitoring and indoor analyzing,overlying water environmental conditions and physicochemical properties of sediments were carried out,besides,characteristics of surface sediment grain size under the special hydrodynamic background and stratified density flow of XXB were analyzed.The results showed that the dominant sediment size were sand and silty sand,and the spatial variation of sediment size composition was obvious in different water level operating periods.The clay composition gradually decreased from the lower reaches to the upper of XXB during the water-leveling period.In flood season,the clay was high in the middle reaches and low in the upper and lower reaches.The spatial distribution of grain size of surface sediments indicated that the migration and distribution of sediments were roughly consistent with hydrodynamic conditions in XXB,and the depositional environment was jointly affected by the main stream of the Yangtze River,the upper stream inflow,water temperature and geological conditions.