Typical Physical And Ecological Characteristics Change And Its Affiliated Research In Deepwater Reservoir

Facing the current situations that deep reservoirs vertical water exchange rate slows down after Thermal Stratification formed in the summer, in the surface mixing depth Algal’s distribution, diffusion changed greatly according to the environment. Taking Xi’an Heihe reservoir as a case study, the research combined the methods of on-line water quality monitoring and laboratory settlement simulation analysis of algae. Focusing on the following three points: 1.Thermal stratification specific quantitative methods, the formation characteristics and the main influencing factors of thermal stratification. 2.Analysis of the causes of deterioration of water quality during thermal stratification. 3.Algae distribution characteristics under different environmental conditions and determine the rate range of migration. The main conclusions are as follows:(1) The current study describes the phenomenon of thermal stratification are abstract is not easy to direct analysis, Therefore, this paper analyzes all kinds of field reservoir data selected APE index as characterizing stable strength of thermal stratification. This index objective and direct express four season’s strength of thermal stratification in deep reservoir and In figure forms express the formation and attenuation of thermal stratification this can help us carry out a more detailed research on the thermal stratification.(2) The formation of thermal stratification are mainly controlled by the temperature. Formation of thermal stratification in late spring when temperatures begun to rise. Each year from June to August have the highest temperature so the thermal stratification into the most stable phase and the APE average value is the highest of all year; When entering autumn temperature decreasing thermal stratification began to attenuation and APE index from the highest value down to 0 after the "turn over" occur; Compared with the air temperature water renewal rate is the Key factor of slow down thermal stratification formation and promote its attenuation, Data Analysis that larger water renewal rate will help reduce APE index and accelerate Vertical water into the mixing stage.(3) After the formation of thermal stratification vertical water exchange less and hindered the bottom water dissolved oxygen supply lead to the bottom water after thermal stratification begin to form gradually reduced to hypoxia environment, Anaerobic environment made anaerobic microorganisms decompose the nitrogen and phosphorus pollutants in the bottom mud and released into the water aggravated the eutrophication level of the bottom water, Correlation analysis showed that DO concentration and the concentration of nitrogen and phosphorus in bottom water are closely connected.(4) Select common algae species--- Scenedesmus of Case reservoir under light, bottom discharge and rainfall carried out sedimentation experiments. The results showed that floating zone’s scenedesmus its optimal growth light intensity is 5000-7000 lx in five kinds light intensity and show strong phototaxis floatation characteristic and its floatation speed up to 68.1μm/s; While rainfall mainly inhibit the algae floating make its floating speed reduced to 24.2-42μm/s, less than the Scenedesmus floating rate in illumination experiment, The bottom of the sinking zone is less affected by the rainfall the velocity distribution in 50.3 to 71.5μm/s the results are similar to light experimental;The bottom discharge experiments significantly accelerate settling velocity of Scenedesmus in sinking zone and the highest speed reaches 215.4μm / s.