Study On Water Temperature Prediction Of Cascade Reservoirs In The Upstream Of Tuoshengan River

River cascsde development improves the water resources utilization ratio and promotes social and economic progress,but which has a great influence on the regional ecological environment system.The water temperature prediction is one of the important contents of environmental impact assessment on the hydroelectric project,which is also of great significance to the water resources utilization and sustainable development.Water temperature is one of the important factors in water environment.It is very sensitive to water temperature for physical and chemical characteristics of water,marine organisms, crops,water ecology.The change of water temperature could take series of impact on water quality,growth of marine organisms and production of industry and agriculture in reservoir district and its lower rivers.Thus it is significant to improve environment to simulate and forecast correctly the rules about the distributions of water temperature in reservoir,so as to control water temperature.Based on the previous studies,the paper applies MIKE3 mathematic model to predict the water temperature change after the implementation of planning of cascade reservoirs and downstream channel in the upstream of Tuoshengan river of Akesu river basin in Xinjiang. MIKE3 mathematic model is used to calculate three-dimensional water temperature in Qiqiaer reservoir region(α=2.54,stratified)and Kekekaer reservoir region(α=2.57,stratified)in the scheme 3rd(recommended scheme)and three alternative schemes.According to the date in the normal flow year(P=50%,in 1991),the monthly water temperature which is in front of the dam and reservoir outlet is calculated.One-dimensional water temperature model of the natural river will be used to calculate water temperature of river channel and the diversion type hydropower station.According to the simulation result,the influence of water temperature is analyzed and predicted in the different cascade development scheme in the upstream of Tuoshengan River.The main research results is as follows: 1..The general change tendency of Qiqiaer water temperature distribution is uniform in four schemes.Stratification of the water temperature in the front of the dam and reservoir region has a strong seasonal property.Comparison of the water temperature between before the construction of the reservoir and discharged water,which showes some variation. Discnarged water temperature is lower than the temperature of the natural river from May to September,and the maximum of temperature difference appears in July.Discharged water temperature is higher than the natural fiver from October to April,and the maximum of temperature difference appears in November.The annual variety curve of water temperature shows the planarization trend.2.Stratification of Kekekaer water temperature in the front of the dam and reservoir region has a strong seasonal property in the scheme 1st,2nd and 3rd.Discharged water temperature after founding of reservior is lower than temperature of the natural river.Discharged water temperature is lower than temperature of the natural fiver and Qiqiaer dischargerde water from May to September,and the maximum of the temperature difference appears in July. Discharged water temperature is higher than temperature of the natural river and.Qiqiaer dischargerde water from October to April,and the maximum of temperature difference appears in November.Because incoming water is from Qiqiaer power station dischargerde water and the water temperature distribution is flatter than the natural fiver,Discharged water temperature distribution is flatter than outlet of Qiqiaer power station.3.Kekekaer power station is mixed reservoir in May,August and September in the scheme 4th. The trend of discharged water temperature distribution in the scheme 4th and in other scheme is same.But water temperature varied amplitude is larger,discharged water temperature is lower than temperature of the other scheme in winner and higher in summer.4.By comparing the result of calculation of the four schemes,the discharged water temperature of reservoir has the smallest influence at temperature of the natural river.To decrease influence of the water temperature of the dowmstream channel,the scheme 4th is recommended.