| Poyang Lake is the largest fresh lake in China,and has the ecological functions of regulating flood and protecting biodiversity.But in recent years,there are ecological problems in Po yang Lake such as the shortage of water ? wetlands degradation ?water degradation and so on,which has catch the immediate attention of scholars and government.The built of the proposed Lake Poyang hydraulic project(PLPHP)has again raised debate,however,the built PLPHP certainly will change the hydrology and hydrodynamic force of Po yang Lake that is in state of nature.Lake current is an important dynamic indicator.which not only determines the transportation and spread of various substances and pollutant but also affects series of human activities.Research results are as follows:(1)Through the analysis of the simulation results of the mean annual flow rate within project control or not in 2010(wet hydro-years),2000(normal years)and 2004(dry years): The influence of PLPHP on the lake flow rate is the smalest in 2010,and the influence on the waterway of Lake Poyang and the main lake area is more than two natural reserves.In normal years,the influence of PLPHP on t on the lake flow rate is stronger than the influence in 2000,especially in Three Gorges impoundment period and the bottom of the dry season.The flow velocity of the waterway decreases,and the flow velocity of the Nan Ji Shan natural reserves increases.The influence of PLPHP on the flow velocity of Poyang Lake is the biggest in 2004,The flow rate of each scheduling period is obviously different in different places.(2)In order to research the influence of PLPHP on the flow direction,this paper simulate the flow direction according to the proposed scheduling scheme within project control or not,in three typical years.Simulation results show,In each scheduling period,the flow direction change is obvious in Three Gorges impoundment period ? in Compensation period and the dry season.On the other hand,the PLPHP has the greatest impact on the flow direction is 2004,followed by the year of 2000,the minimum impact on the2010.In addition,the comparison of the beginning date of the scheduling period is carried out,and it is found that the change of the flow direction is the most obvious in the in storage period and the dry season.(3)The implementation of PLPHP will change the basic lake flow characteristics.Due to the adjustment of water level of PLPHP,the Jacking type and the Inverted type in natural state be replaced by reflux type and drainage type.Under no control,the Lake flow of Poyang lake give priority to gravity type,followed by Jacking type,inverted type is least;Under the condition of PLPHP,the gravity type and drainage type decreased,and the dry season was the most important;Jacking type and storage type increased in dry years for most;Under no control,the Jacking type was reduced from 14 d to 8D,and the other year types were not transferred,in dry year.Due to water storage,there were 11 d and 12 D reflux in 2000 and 2010,respectively.(4)The basic flow characteristics is affected by PLPHP,in the meantime,corresponding changes have taken place in the flow of local lake.Survey shows,the study selected the different type in the Poyang Lake five characteristics that exist in the local flow field were analyzed.The results show that the Han Chi lake counterclockwise half circulation field and flow field near the frequency is higher a kind of local flow field,due to Han Chi lake near the water level is relatively high,key project of the region has little effect on a local lake flow,little older but low water year influence degree.During compensation adjustment period,influenced by PLPHP scheduling level,have a hub status appeared relatively stronger than when no hub counterclockwise half circulation;Low water,hub to adjust the near Han Chi lake appeared to raise the water levels significantly back flow. |
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