The Influence Mechanism Research of Inflow Water Temperature on the Water Temperature Structure in a Large Reservoir

It would change the distribution of water temperature after the reservoir’s building, which would make an important affect on the water quality and the water environment downstream. The more detailed the inflow temperature data is, the more accurate the prediction of simulation results on the water temperature distribution in a reservoir is. While, the original data collection would cost a lot of time and effort, therefore, to solve the incompatible problems, in present study, a 3-dimensional hydraulic-thermodynamic numerical model is established to predict the temporal and spatial distribution of water temperature in the two different time scale inflow water temperature condition in the same reservoir. It is found that the heat transfer way is different in the different period, for the large reservoir located in cold plateau, the heat convection always appear between the lower and the upper when the reservoir storage continues to reduce and when the temperature and radiation increases in the next year, the heat storage increases, the local convection would occur in the upper layer of the reservoir and the temperature of the upper water is between 0 and 4 ℃ at the time; when the whole water temperature in the reservoir is more than 4 ℃, the heat conduction is mainly the heat transfer way in the reservoir. The stratification phenomenon appears in most time of a year in a lager reservoir, the water in the upper of the reservoir is higher when the temperature is higher in a year; while it is lower in the upper when the temperature is lower; and the non-stratified phenomenon appears in a short period when the two stratified phenomenon above converts form one to the other. The results also shows there is a close relationship between the water temperature structure and the inflow water temperature in a large reservoir, and to some degree, the vertical distribution difference of water temperature in large reservoirs in different scales could be reflected by the numerical differences of inflow water temperature, comparing the two simulation results on the water temperature distribution, there is the area of a great impact on the inflow temperature, outside the area, there is small difference between the two results, which can be used as a basis for the selection of inflow water temperature when the water temperature in some local regions need to be predicted accurately for some reason.