Research On The Water Temperature Simulation For Longyangxia Reservoir And Influence On Temperature Of River Downstream

The water temperature prediction for the huge and deep reservoir is one of the important contents of the environmental impact assessment on the hydropower projects. It is greatly meaningful to sustainable development of water resources. Based on the previous studies, this paper simulate for the water temperature in Longyangxia reservoir and downstream channel with the mixed k -ε/smagorinsky formulation in MIKE3, it analysis the reservoir water temperature stratification in formation, development, and changes in the law, it also summarized reservoir water temperature stratification. The Main result as follows:(1) This paper uses the mixed k-ε/smagorinsky formulation for simulation calculation. The result of the calculation is all right, and accord with the measured temperature distribution.(2) The water temperature structure of the Longyangxia Hydropower Station is stability typical delamination type. The water temperature stratification has obvious seasonal in front of the dam. The water temperature inflow is higher in May-October. The water temperature is delamination because the air temperature is high, it shows that the upper is low-temperature and the lower is high-temperature; the reservoir water temperature inflow is gradually reduce from November, the flow rate decreased rapidly, and the water is the mixed state, with the debase air temperature, the surface water temperature were lower. The runoff water temperature of the Longyangxia Reservoir is lower than natural river from April-Septembe, the maximum temperature appeared in May, as -8.09℃, and the minimum temperature appeared in September, as -0.7℃. The water temperature inflow is higher than the natural channel inflow in October-December and January-March, the maximum temperature appeared in December, as 7.71℃, and the minimum temperature appeared in March, as 0.59℃. (3) Compared with the natural channel, the outflow of Longyangxia Hydropower Station water temperature was a certain degree of change. It will cause it to excrete water temperature in the year to change the scope to have compared to the natural river course reduces after the reservoir completes. This rule conforms to the general large and middle scale reservoirs to excrete the water temperature rule. The water temperature vertical distribution appeared the obvious seasonal change in front of the Longyangxia dam: The water temperature in front of the Longyangxia dam has stable stratification in May-December, which 0-50m deepth relatively high temperature surface, decreasing temperature in May was 0.0448℃/m; 50-80m depth in the front of the dam between the more obvious thermocline, the temperature reached the maximum gradient,which August the temperature gradient as 0.313℃/m in front of the dam, as the peak value; 80m below has little change, as the stagnated temperature layer.(4) Before GuiDe station, already restored before constructing the storehouse the natural river course water temperature after the water runout of the Longyangxia The lengths of influence downstream channel in each month are: 10km,15km,20km,2km,60km,60km,30km,50km,30km,1km,15kkm,25kkm。This shows that the NiNa Hydropower which located next the Longyangxia Reservoir would be influence (41km) only in three months, May, June, August.