The Influence Of Reservoir Operation To Water Temperature Structure Of Tributaries Bays In Three Gorges Reservoir

Water temperature changes in lakes and reservoirs have significant influence on the regional and even the aquatic environment. To achieve the ecological improvement of Three Gorges Reservoir, study on how Reservoir Operation affects Tributary Bay’s temperature, and analyzing the thermodynamic conditions’ effects are necessary. In this thesis, inspired by the literature review on the temperature stratification, we built the monitoring database of water temperature and meteorological index in the three tributaries of Three Gorges Reservoir, Caotang River, Meixi River and Zhuyi River. Based on the monitoring data, this thesis analyzed the variation of the spatial and temporal distribution as well as the water temperature stratification intensity, computed the inner-year change of net surface heat flux, heat convective transport flux and heat content of tributary bay, and quantitatively calculated the required energy(necessary heat) for the complete collapse of the stratification status of the water body by conducting Schmitt thermal stability method.. The research presented that:(1) Affected by the different main-tributary water exchange rate, along with the different intersectional angles, the water tongue coverage of the three tributaries were different. The water tongue extending area were 3/4, 3/4 and 1/2 for Caotang, Meixi and Zhuyi River separately. As for the water temperature stratification, the worst stratified status appeared in Caotang River, where the other two rivers showed the same status.(2) The net surface heat flux decreased along the upstream direction. In spring and summer, the water temperature structure varied apparently. The prominent variation of net surface heat flux caused by the significant changes of heat budget,including longwave radiation flux, sensible heat flux, and latent heat flux that were sensible to the meteorological conditions. In autumn and winter, the temperature structure variation was unapparent. Convective transfer heat and water elevation changes showed significant correlation.(3) Convective transfer heat might be the dominant factor affecting the heat content changing progress. Between the major two affecting factors, convective transfer heat and net surface heat flux, to the heat content change, convective transferheat contributed more than 50% of the monthly heat content variation. Thus it can be regarded as the dominant factor.(4) Tributaries exhibited spatial and temporal distribution pattern of thermal stability. In space, the maximum thermal stability appeared alternatively between the intersection of the main stream and tributaries and the middle of the tributaries. In time, the thermal stability appeared double peaks in early spring and early autumn,and double troughs in summer and winter.(5) The thermal stability of different tributaries is not consistent with the response of reservoir operation. Comparing different Reservoir operating phases, the thermal stability of Meixi River was the most sensible branch to the reservoir operation, and Zhuyi River was the worst sensible one. Influenced by the intersectional angles, the thermal stability appeared descending order among Meixi,Zhuyi and Caotang River at the estuaries and the middle part. The maximum thermal stability appeared alternatively among the three at the upstream part.