Numerical Simulation On Temperature Of Water Released From Multi-level Intake Of Nuozhadu Hydropower Station

A large area of backwater field is formed after a reservoir is built. Because of theradiation of the sunlight and physical chemistry characteristics of water, anenvironment which totally different from original river is formed, the character of thetemperature in reservoir is obviously distributed of seasonal stratification. Thetraditional bottom withdrawal makes the temperature of downstream lower thanoriginal water temperature, and the low water temperature will lead to negative effecton ecological environment of downstream. So, it has a great significance to theecological environmental of downstream by studying the new method of withdrawal.Multi-level intake structure with stoplog gate is adopted in Nuozhadu hydropowerstation. This paper takes Nuozhadu hydropower station as an example, simulates thetemperature of water released from it, and discusses the relationship between thewater temperature distribution, the height of the stoplog gate and the temperature ofwater released. The main conclusions are summarized as follows:1．The3D numerical model simulating the temperature of water released fromthe multi-level intake of Nuozhadu hydropower station is established based on EFDC,and the numerical results are tested validly by the physical model experiment results.2.According to different operating rules of the stoplog gate scheme, simulates thetwelve months’ velocity field of each typical year, the results indicate that, under thefour operating rules for stoplog gate, the velocity field of the surface are the same;the velocity field of the withdrawal level in reservoir are the same, and different nearthe intake. The higher of the stoplog gate is, the higher of the discharge watertemperature enhanced.3．Compared the released water temperature between stoplog gate scheme andtraditional bottom withdrawal scheme, the temperature of water released from thestoplog gate scheme is higher than that from the bottom withdrawal scheme. It is validto enhance the temperature of discharge water that the multi-level intake structurewith stoplog gate is adopted.4．The temperature of water released with different height of stoplog gate issimulated in three typical years. The rate of enhancing discharge water temperaturedepends not only on the height of the stoplog gate, but also the vertical distribution ofwater temperature in reservoir. The larger of the temperature difference betweenepilimnion and hypolimnion, the higher of discharge water temperature enhanced, contrarily, the rate of enhancing discharge water temperature is small. Therelationship among water temperature distribution, height of the stoplog gate andtemperature of water released is investigated, and the results can offer a scientificreference to predict the discharge water temperature.