| Winter rime landscape is one of the important pillars to promote the development of tourism industry in Jilin City City,and the water temperature distribution characteristics of Songhua River have an important impact on the formation of rime in Jilin City City.At present,there are many factors hindering navigation in the urban section of Songhua River in Jilin City.It is urgent to improve the navigation conditions of this section by waterway regulation,which may change the water temperature distribution characteristics of this section and affect the formation of rime landscape in Jilin City.Based on the hydrological,meteorological and topographic data of the Songhua River in Jilin urban area,this thesis analyzes the hydrological characteristics,climatic characteristics and the current situation of the waterway in the studied reach;The main factors affecting the water temperature of Songhua River are analyzed through the field measurement of the water temperature in the studied reach;According to the established water temperature model of Songhua River in Jilin urban area,the water temperature distribution characteristics of the channel under waterway regulation are analyzed,and the impact of waterway regulation works on water temperature distribution and rime landscape is clarified.The main research results are as follows:(1)Based on the measured data,the variation characteristics of water level and water temperature along the Songhua River in Jilin urban area are analyzed,and it is pointed out that the complex terrain and hydraulic structures of Changbai Island reach are the important reasons for the sharp increase of water level gradient in this reach,and the cooling law of water temperature along the Songhua River in Jilin urban area is obtained: the river cooling along the natural state conforms to the linear change trend of t=-0.043x+1.59;Based on the linear trend of temperature decrease along the route,it can be inferred that without the influence of factory temperature drainage,the river water temperature will drop to 0 ℃ at the Jiuzhan Railway Bridge.(2)Based on a water temperature model,the distribution of river water temperature before and after waterway regulation under different operating conditions was simulated and analyzed.The results show that the water temperature of the river after the waterway regulation will be higher than before the regulation.According to the simulation results,the changes in water temperature distribution after the waterway regulation are mainly concentrated in the downstream of the Wusong Bridge,manifested as the water temperature of the river downstream of the Wusong Bridge being higher than before the regulation;Channel regulation mainly has a significant impact on the distribution of water temperature under low flow rates.As the flow rate increases,the impact of channel regulation on the distribution of water temperature gradually decreases.(3)The reasons for the changes in the temperature distribution of river water after channel regulation were analyzed: due to the overall flow velocity of the river after channel regulation being higher than before,and the retention time of water within the same distance being shorter than before regulation,the time for heat exchange between the water body and the outside world decreased,resulting in a higher water temperature after regulation than before,and a change in the water temperature distribution.(4)After the waterway regulation,due to the increase in river water temperature,the position of the frozen section of the river moved downwards.The heat flux required to maintain the downstream channel of Wusong Island without freezing under different temperature conditions was calculated.The heat flux required to maintain the downstream channel of Wusong Island without freezing at temperatures of-25 ℃,-15 ℃,and-5 ℃ were 6.6GJ/s,4.5GJ/s,and 2.8GJ/s,respectively.The influence of waterway regulation on the formation of rime is analyzed: due to the increase of water temperature and the distance between unsealed river sections caused by waterway regulation,the distance between the rivers of Songhua River that can transport water vapor to both banks is increased,and the air humidity is better increased.After waterway regulation,it will be more conducive to the formation of rime landscape in Jilin urban area. |
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