The Study On The Slowing Effects Of The Retaining Wall Towards The Low Temperature Discharge Water In The Reservior Of Jiudianxia

Water temperature is one of the important physical factors of river ecosystems and Damming rivers will cause changes in the water temperature of downstream channels to varying degrees,especially the changes brought by high damreservoirs.Carrying out the research on the orderliness of water temperature change caused by high dam reservoirs and the regulation effects of the water temperature can provide a significant reference for river environmental protection.Taking Jiudianxia Reservoir of Tao River in Gansu Province as the research object,based on the prototype observation and numerical model method,The water temperature model of the whole reservoir area was constructed,and the parameters were calibrated and verified.the relationship between the vertical water temperature distribution inside the reservoir and the drain water temperature was studied;The extent of the impact of the discharge water on the downstream channel temperature under the different operating modes of the reservoir was discussed;A detailed model of the front section of the dam was constructed,and the mitigation effects of the Retaining Wall on the low temperature water discharged of the reservoir under different operating water level conditions were simulated.The main research results are as follows:(1)The water temperature distribution of Jiudianxia Reservoir presents typical characteristics of water temperature stratification.The stratification period is from April to July.Under high water level conditions,the stratification is obvious.The monthly average temperature difference of the surface water temperature above the diversion outlet in the reservoir is 2?5? Water causes the temperature of the downstream river to decrease,and the impact of the low-temperature water caused by the discharge of the reservoir in April is more significant.(2)A three-dimensional water temperature model of the entire reservoir area of Jiudianxia was constructed,and the model parameters were calibrated and verified.The simulation results of the vertical water temperature in front of the dam are in good agreement with the measured values.Aiming at different operating water levels and discharge outlet heights,the simulation of the discharge temperature and the distribution of water temperature in the reservoir is provided to provide basic data for the later simulation of the effect the Retaining Wall on the reduction of the discharge temperature.(3)Carrying out research on the mitigation effect of the Retaining Wall on the discharge of low-temperature water,using the refined model of the front of the dam to simulate the high and low operating water level conditions,with or without the Retaining Wall,the water temperature distribution in the reservoir is simulated,which is significant.During the stratification period,from the end of April to the middle of June,the result of the discharge temperature was higher than that of the Retaining Wall.Under high water level operation,the average value of the discharge temperature increased by 1.1?,and the daily maximum temperature increased by 2.7?.Under low water level operation,the average temperature rise is only 0.5?,and the maximum daily temperature rise is increased by 1.8?.Under the two water levels,the effect of high water level on the discharge of low-temperature water is more obvious.