| The water impoundment operation of the Three Gorges Reservoir has affected the hydrological situation of the rivers and lakes in the middle and lower reaches of the Yangtze River,and the confluence area of the Yangtze River and Dongting Lake is the most sensitive area to the change of water situation.So,what impact will the water impoundment of the Three Gorges Reservoir have on the hydrological characteristics and the ecosystem of the confluence area? In view of this,this paper takes the confluence area of the Yangtze River and Dongting Lake as the research object,and analyzes the hydrological change and ecological effect of the confluence area of the Yangtze River and Dongting Lake according to relevant methods such as trend test,abrupt test,coefficient of variation of discharge and coefficient of uneven distribution within a year,hydrological change index method and variation range method.The main research results are as follows:Firstly,in terms of the change of hydrological time series in the confluence area of the Three Gorges Reservoir:(1)Interannual variation characteristics of discharge: after the impoundment of the Three Gorges Reservoir,the variation coefficients of runoff at Jianli Station,Chenglingji Station and Luoshan Station were 0.092,0.176 and0.113,respectively,and the extreme value ratios were 1.523,2.085 and 1.491,respectively,which were all higher than those before impoundment(coefficient of variation: 0.083,0.159,0.101;Extreme value ratio: 1.354,1.718,1.416).The seasonal changes of the multi-year flow of the three stations showed similar trends in spring,autumn and winter,respectively,showing a unified trend of rise,decline and rise.The multi-year summer flow of Chenglingji and Luoshan stations showed a significant upward trend,while the multi-year summer flow of Jianli station showed a slight downward trend.(2)Annual flow distribution characteristics: the seasonal flow distribution of Jianli Station and Luoshan Station was summer > autumn > spring > winter,and the seasonal flow distribution of Chenglingji Station was summer > spring >autum > winter Monitoring station,city ling angeles flow years,screw mountain stand distribution non-uniform coefficient were 0.484,0.569,0.493,than before the water less(0.587,0.611,0.561),the relative change in three site were 4.097,7.344,4.431,absolute variation were 17247.599,14080.860,28728.369,below before filling(relative variation: 6.083,10.659,6.568;Absolute range of change:22359.123,17670.662,37734.493).(3)Trend of traffic: the average annual flow of the three stations was lower than before impoundments,and the flow trend showed an upward trend.In terms of the increase range,Luoshan Station > Chenglingji Station > janli Station.Secondly,in terms of hydrological change degree in the confluence area of the Three Gorges Reservoir:(1)Among the 32 IHA hydrological indexes of each station,the average monthly discharge in February,the average annual minimum discharge on 1,3,7,30 and 90 days,the base flow index,the average annual daytime water fall rate,and the average annual daytime water rise rate at Luoshan Station were the most affected,all of which showed a height(H)change.(2)The overall hydrological change degree of Jianli Station,Chenglingji Station and Luoshan Station is 44.89%,31.11% and 34.38%,respectively,and the change degree is moderate(M),low(L)and moderate(M)change,respectively.The overall hydrological change degree in the confluence area of rivers and lakes was 36.79%,showing moderate(M)change.(3)The contribution rates of climate fluctuations(precipitation,evapotranspiration)to the eco-hydrology of Jianli,Chenglingji and Luoshan stations were 6.74%,44.09% and 54.65%,respectively,and the contribution rates of water conservancy projects to the three hydrological stations were93.26%,55.91% and 45.35%,respectively.Thirdly,the ecological effects under the hydrological change scenario in the confluence area of the Three Gorges Reservoir:(1)Water environmental effect: the flow of each station in the confluence area decreases compared with that before impoundment,among which the monthly average flow decreases most significantly from June to November,and the water flow process is further flattened,which is easy to cause the accumulation of pollutants.(2)Plant ecological effect: the change of monthly discharge in the confluence area had different effects on the aquatic and marsh plant communities,and the community succession pattern was as follows: submerged plants ? floating plants ? emergent plants ? carex ? reed ?shelterbelt.(3)Fish ecological effect: the spawning and breeding intensive period of the four species and the Chinese sturgeon were all delayed compared with before impoundment,the monthly average flow,the number and duration of high flow peak and the number of persistent fluctuation water in the confluence area during the spawning period were relatively reduced,and some sensitive hydrological indexes showed moderate(M)or above changes during the spawning period. |
PDF Full Text Request