基于EFDC的二滩水库水温模拟及水温分层影响研究

采用EFDC模型模拟二滩水库2006年3～7月的水温变化过程。通过分析与热交换和热传递相关的模型参数，发现太阳短波辐射中快速波所占的比例和太阳短波辐射在水体中的慢速衰减系数这两个参数值的增大均会引起表层水温升高、底层水温降低，而太阳短波辐射在水体中的快速衰减系数对水温的影响并不明显。将不同时期坝前水温和不同断面水温的模拟值和观测值进行比较，以率定模型参数。结果显示EFDC模型能较好地模拟出大型深水库不同时期水温分层结构及沿程发展变化过程。在此基础上，分析该水库的水温分层规律，并结合水库取水规则对比分析建库前后下游河道水温的差别，以期为水库取水设计和运行管理提供科学参考，以此来减缓水库水温分层带来的影响，保护下游河道生态环境和水生生物的多样性

WATER TEMPERATURE MODELING AND INFLUENCES OF WATER TEMPERATURE STRATIFICATION OF ERTAN RESERVOIR BASED ON EFDC

EFDC model was used to simulate water temperature of the Ertan reservoir from February 28th to July 31th,2006.Traverse direction of the reservoir was generalized into a grid and the average width was 400m;longitudinal direction of the reservoir was divided into 139 sections and the grid spacing ranged from about 500 m to 1200 m;vertical direction of the reservoir was divided into 40 layers.Thus， the total number of the research domain grids was 5 560.In order to improve simulation ability of the EFDC model,a preliminary exploration of the uncertainties related to model parameters was made.By analyzing parameters related to heat exchange and transfer,we have found that, surface water temperature would increase and bottom water temperature would decrease,when the value of proportion of fast wave in shortwave radiation (FF) or coefficient of shortwave radiation slowly attenuated in water (SS) increased.On the other hand, the coefficient of shortwave radiation rapidly attenuated in water (SF) had no significant influence on water temperature.Then,parameters were calibrated by comparing the simulated and observed water temperature at different reservoir sections in different time period.The modeling results indicated that the EFDC model could well reveal water temperature stratification structure and their development processes of large deep reservoir.On this basis,the law of water temperature stratification was analyzed.Water temperature stratification phenomenon could be observed in all the months during the simulation period.Stratification structure was simple and a single thermocline was appeared in March.And temperature gradient of the single thermocline gradually became larger from April to June and finally a double thermocline was formed in July.Surface water temperature significantly increased from March to July due to the influences caused by shortwave radiation and air temperature (from about 14℃ to 25℃).Meanwhile,bottom water temperature changed little during this period because the heat was difficult to transfer from surface to bottom (around 11℃).It also could be seen that,temperature of discharged water after the construction of dam was different from the natural river water temperature at the same place.Temperature of discharged water was higher than natural river water temperature in March,June and July;and lower than natural river water temperature in April and May.Therefore,the reasons and influences of water temperature difference due to the construction of dam were analyzed.By doing this,we attempt to provide some scientific basis for water intake design and operation management of reservoir in order to reduce the influences of water temperature stratification and protect the ecological environment and aquatic biodiversity of the downstream river