基于CE-QUAL-W2模型的三峡水库神农溪库湾水流水温特性分析

三峡水库蓄水以来,库区干、支流水文水动力变化显著。通过现场观测和构建三峡水库神农溪支流库湾立面二维水动力模型(CE-QUAL- W2),对比研究了三峡水库不同时期水流、水温时空分布特征。研究结果表明:神农溪库湾水体整体流速缓慢,不同时期均存在不同强度的异重流现象,包括干流倒灌异重流和上游入流底部顺坡异重流;枯水运行期和汛前消落期干流水体从表层潜入库湾,强度较弱;汛期和汛末蓄水期存在中层倒灌并且强度较大,影响整个库湾;上游入流处由于来流水温一般低于库湾,存在入流底部顺坡异重流现象。库湾水温呈春夏升温、秋冬降温的变化趋势,一年四季均存在水温分层现象;但冬季分层相对较弱,其它季节水温分层明显;水温分层模式因异重流的存在,明显不同于一般水库的水温分层。对比分析表明,CE-QUAL-W2模型可较为准确地反映神农溪库湾水流及水温时空分布特性。研究可为更细化分析三峡水库神农溪库湾水流水温特性、开展水华预报提供技术支撑。

Characteristics of Flow Velocity and Water Temperature in Shennong Bay Using CE-QUAL-W2 Model

The hydrodynamic characteristics have changed greatly in the mainstream and its tributaries since the impoundment of Three Gorges Reservoir (TGR).Through field observation and a two-dimensional, laterally averaged, hydrodynamic model simulation by CE-QUAL-W2, we compared and analyzed the spatial and temporal distributions of the water temperature and the hydrodynamics of Shennong River bay in the TGR in different running periods. The comparative analysis results reveal that water flow has become quite slow in Shennong Bay, and density currents of different strengths exist in different running periods, including reverse density currents from mainstream to bay and the accordant bottom density current from the Shennong River to bay. In dry season and the drawdown period before flood season, the water of the mainstream of TGR flows into the Shennong Bay in surface density current with low strength; while in wet season and impoundment period in the end of flood season, mid-layer density current of high strength affects the whole bay. Downward bottom density current exists at the upstream inflow because the temperature of incoming flow is usually lower than that in the bay. Furthermore, the water temperature in the bay increases in spring and summer and decreases in autumn and winter. The stratification of water temperature is obvious in the bay in all seasons, but was weak in winter and strong in other seasons. The model of stratification is quite different from that of general reservoirs due to density currents. The simulation results indicate that CE-QUAL-W2 model performs well in simulating the density current and water temperature stratification characteristics. This research offers technical support for detailed analysis on the hydrodynamics in Shennong River of TGR.