| As the largest river in Jiangxi Province,Ganjiang River is rich in fish resources,but in recent years,due to the dual impact of climate change and human activities,the spatial and temporal distribution of natural runoff and hydrological situation have been changed,and the degradation of water ecosystem is obvious.Therefore,the study on the ecological flow of Ganjiang River can provide scientific basis for the optimal allocation of water resources,sustainable development and utilization,and the restoration of water ecosystem in Ganjiang River Basin.The main contents of this paper are as follows:(1)Taking the Ganjiang River as the research reach,based on the daily flow series of four hydrometric stations of Dongbei,Ji’an,Xiajiang and Waizhou,the trend analysis of daily flow data is carried out based on the linear tendency estimation method,sliding average method and man Kendall method,and the mutation analysis of data is carried out by man Kendall method.The results show that the average annual discharge of each hydrological station in the main stream of Ganjiang River shows an increasing trend,but the increasing trend is not obvious,and the discharge in spawning period shows an insignificant decreasing trend.(2)Through IHA(Indicators of Hydrologic Alteration)analysis and calculation of three hydrological stations,Dongbei,Ji’an and Xiajiang,each group of hydrological change index(IHA),its hydrological change degree and the overall hydrological change degree of the river.The results show that under the influence of human activities,the overall change degree of the three hydrological stations are 46.93%(moderate change),49.60%(moderate change)and 75.41%(high change),and the change degree of the three stations are relatively obvious,which shows that the hydrological situation of the Ganjiang River main stream is quite different from the natural situation under the influence of human activities.(3)coupling MIKE11 one-dimensional hydrodynamic model and PHABSIM to simulate the suitable ecological flow of the physical habitat of Ganjiang River main stream,combining with the flow rate,water depth and water temperature suitability curve of the target species,the weighted suitable area(WUA)of the four great fishes in each river reach is also increased with the increase of the flow at low flow,but the range is also increased with the increase of the flow.After reaching a certain discharge,it decreases and tends to be stable with the increase of discharge,among which the suitable ecological discharge of reach 1~4 is 725 m~3/s,1225 m~3/s,1500 m~3/s and 2115m~3/s respectively.(4)According to the historical flow data of more than 50 years of Dongbei,Ji’an,Xiajiang and Waizhou hydrological stations,the suitable monthly ecological flow process of the representative hydrological stations in the middle and lower reaches of the Ganjiang River main stream is calculated by using a variety of hydrological methods.(5)Combining the flow of spawning period simulated by the physical habitat model with the ecological flow obtained by the hydrological method,the monthly ecological flow value of the main stream of Ganjiang River is obtained.According to the suitable ecological flow of each station,the comprehensive index of ecological flow is obtained by analyzing the deviation rate,satisfaction degree and suitability degree of monthly flow.The results show that the comprehensive indicators of ecological flow of the four stations are all above 0.6,which are all at the"good"health level,and will not cause damage to the healthy ecosystem of the river. |
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