Abstract:

Water quality situation  and water temperature distribution will influence not only water ecological environment structure of the front of the dam,but also water quality of the downstream of reservoir,aquatic microorganism and fish breeding growth.Water temperature is one of the important water quality parameters to assess reservoir water ecological system.For studying the water temperature condition of reservoir head of the Three Gorges Reservoir (TGR),the monitoring section was set away from the Three Gorges Dam approximately 35 km in 2011,and  water temperature of the reservoir head was monitored detailed in each operating period after the completion of the Three Gorges Project (TGP).Research found that under the established routine scheduling mode of operation of the Three Gorges Project,the bottom of the reservoir head formed obvious low temperature area from December 2011 to April 2012,water temperature difference between the surface and bottom reached to annual maximum 208℃ and maximum temperature gradient was 0156 in March 2012.The low temperature area of bottom was rapidly declined,and water temperature difference between the surface and bottom was less than 10℃ in May.From June to September,the low temperature area showed a subdued trend,water vertical mixing gradually enhanced,and water temperature vertical distribution of reservoir head was basic uniform.But in October,because of the low temperature of upstream inflow,the water of higher density dived into the bottom resulting in low temperature area  strengthened,and brought about water temperature difference of the surface and bottom reached to 146℃.In the head of the Three Gorges Reservoir,water temperature condition and structure type were different from one another in different operation period.According to the observation findings,water temperature showed no stability phenomenon at present in the head of the Three Gorges Reservoir.In addition,according to water temperature monitoring data of Maoping section from March to May 2012,water temperature of lateral section was almost uniform.The result indicated that water temperature distribution of lateral section was the same basically.Based on the measured data of Maoping section in the head of the Three Gorges Reservoir from June 2011 to May 2012,water temperature structure of the head of the Three Gorges Reservoir in different operation period was also analyzed.This paper could provide basis and references to the research on the channel water temperature changed by the completion of the Three Gorges Dam and whether the water temperature stratification exists in front the dam