| The environmental problems caused by the frequently occurrenced algae bloom of tributaries after the completion of the Three Gorges Reservoir,has seriously affected the ecological environment of the reservoir area and the people’s water security.How to effectively prevent and control the bloom in the tributaries of the reservoir and improve the tributary water environment in the reservoir area has become the focus of the current study on the Three Gorges Reservoir.Considering the limitations of routine prevention and control of algae bloom methods: physical methods,chemical methods,and biological methods in the implementation and ecological aspects of the operations,the changes in the hydrodynamic conditions combined with the tributaries after the impoundment of the Three Gorges Reservoir are the main causes of tributary blooms.In order to prevent and control tributaries of the Three Gorges Reservoir Ecological Regulation,combined with the “tide-type” ecological operation methodology,the ecological operation schemes under different influent conditions and different high water bloom periods were proposed.Based on the special hydrodynamic conditions in the tributaries of the Three Gorges Reservoir,the main cause of tributary blooms was determined.A data-driven model was used to accurately predict the status of the tributary blooms,and the parameters that characterize the reservoir operation process were proposed: water level,the frequency of water level is variable,and the level of water level is the predictor of tributary water bloom situation.The actual monitoring data of the water bloom situation in XiangXi River from 2010 to 2012 is the training prediction sample,and the BPA neural network algorithm is used to construct the tributary water bloom forecasting model facing the reservoir operation process.The water bloom prediction model and the Three Gorges Reservoir power optimization operation model are nested to construct an ecological operation model for preventing and controlling tributary blooms,and the long-term optimal operation calculation results with monthly calculation steps are used to guide short-term optimization with daily calculation steps.The method of operation calculation uses the discrete dynamic programming method to solve the ecological operation model;the water bloom forecasting model is used as a tool,and different tidal-type ecological operation methods are used to set different “tidal” reservoir operation conditions.,Analyzed and summarized the characteristics of water level changes of the "tidal type" ecological operation in different periods.(1)Spring “tidal” ecological operation program: In the spring of the flood season,increasing the amplitude and duration of the Taisheng water level can significantly reduce the Chla concentration in the tributary water.Therefore,the spring “tidal” operation should be combined with the hydrological forecast to reduce the water level of the reservoir fluctuates to create a “tide-type” water level change process with constant duration and large amplitude.(2)Summer “tide-type” ecological operation program: The multi-frequency “tidal” water level fluctuation operation process has certain effects on the prevention and control of tributary blooms,but the effect is not obvious.Therefore,in summer,the "tidal-type" ecological operation should give priority to flood control and reduction of reservoir abandonment,and make use of the reservoir’s capacity for flood protection and the large amount of water during the summer flood season to achieve a multi-frequency,large-scale "tidal" water level fluctuation operation process as much as possible..(3)Autumn “tidal” ecological operation program: The multi-frequency “tidal” water level fluctuations have a significant inhibitory effect on the water bloom in autumn,and a small amount of precipitation,a large increase in water,has a better inhibitory effect on autumn blooms.Since the autumn bloom situation is not spring,summer blooms are serious,and the duration is short,combined with the principle of reservoir operation and operation “storing peaks and compensating dryness”,the “tidal” ecological operation in autumn should give priority to creating “small-scale precipitation” in a short period.,a substantial increase in water reservoir operation.Combined with the calculation results of reservoir ecological operation under the inflow conditions of typical hydrological years,the duration of the outbreak of water blooms in different periods,and the characteristics of “tide-type” water level fluctuations in different periods,etc.,the “tides” of different influent conditions and different periods were summarized."Eco-Operation program.(1)"Tidal-type" Ecological Operation Plan for Wet years(1)After the spring flood season,after entering March,in order to ensure the minimum flow of the downstream channel operation,when the inbound flow rate is more than 5000 m3/s,it is feasible to implement an ecological operationing program to prevent and control the spring flooding outbreak.If the start time of the ecological operation is in March or April,consider a 16-day period of “tide-type” water level fluctuations,implement the following: water level,0.09 m,6 days,elevation level 0.101 m,and 10-day reservoir operation plan;If the ecological operation starts in May,taking into account the flood control function of the Three Gorges Reservoir,it is necessary to vacate the flood control storage capacity before the flood season,and carry out a 12-day “tide-type” ecological operation,and implement: a rise in water level,0.186 m,4 Days,precipitation,0.5 m,8-day reservoir operation plan.(2)In the summer flood season,combined with the characteristics of changes in the water level of the flood season and the tributary water bloom early warning system,an ecological operation with a period of 7 days was carried out,and the ecological operation started when the concentration of Chla in the tributary water exceeded 20 mg/m3..If the initial water level at the beginning of the ecological operation exceeds 150 m,implement the following: a rainfall level of 1.35 m for 5 days,a rise in water level of 1.07 m,and a 4-day operation plan;if the initial water level is less than 150,implement a water level of 1.35 m.5 days,precipitation,1.07 m,4 days of ecological operation program.(3)In the autumn flood season,when the reservoir operation is scheduled to enter the water storage period in autumn,a 10-day “tide-type” ecological operation will be carried out.The actual implementation will be: rainfall level,0.28 m,3 days,elevation level,0.44 m,7 days.(2)The "tide type" ecological operationing plan for the flat water year(1)In spring water bloom period,the principles for formulating the "tidal-type" ecological operation plan in the spring are the same as those in Fengshui.If the ecological operationing starts in March and April,consider a 16-day “tide-type” water level fluctuation cycle to implement: a rainfall level of 0.09 m for 6 days,a water level of 0.487 m,and a 10-day reservoir operation plan;If the start of ecological operation takes place in May,taking into account the flood control function of the Three Gorges Reservoir,that is,it is necessary to vacate the flood storage capacity before the flood season,it is recommended to adopt a 12-day "tide-type" ecological operation for the implementation of the water level: 0.33 m,4 days,precipitation level,0.93 m,8-day reservoir operation program.(2)In the summer flood season,combined with the characteristics of water level changes in the flood season and the tributary water bloom situation early warning system,the ecological operation is carried out for a period of 7 days,and when the concentration of Chla in the tributary water exceeds 20 mg/m3,the ecology starts to start.Operation.If the initial water level at the beginning of the ecological operation exceeds 150 m,perform the following: 1.2.1 m,1.16 m,4 days,water level,1.08 m,and 5 days of the operationing plan;if the initial water level is less than 150 m,implement: 1.12 m.,5 days,precipitation,1.21 m,4 days of ecological operation program.(3)In the autumn flood season,when the reservoir operation is scheduled to enter the autumn impoundment period,a “tidal” ecological schedule will be implemented for a period of 10 days in the fall,with specific implementation: precipitation level,0.23 m,3 days,elevation level,0.41 m,7 days.(3)“tide-type” ecological operationing plan for dry years(1)In the spring period of water bloom,if the start time of ecological operation is in March and April,consider taking 16 days as a period of “tide-type” water level fluctuations,implementing: precipitation level,0.047 m,6 days;elevation level 0.12 m The 10-day reservoir operationing plan;if the ecological operation starts in May,taking into account the flood control function of the Three Gorges Reservoir,that is,the flood storage capacity needs to be vacated before the flood season arrives,it is recommended to adopt a 12-day “tide-type” ecological operationing cycle.Implementation of the water level: 0.046 m,4 days,precipitation level,1.07 m,8 days reservoir operation plan.(2)During the flood season in summer,the ecological operation was carried out for a period of 7 days,and ecological operation began when the concentration of Chla in the tributary water exceeded 20 mg/m3.If the initial water level at the beginning of the ecological operation exceeds 150 m,perform the following: 1.2.1 m for precipitation,1.22 m for 4 days,and 0.97 m for 5 days;if the initial water level is less than 150 m,perform the following: water level 1.11 m,5 days,precipitation,1.40 m,4 days of ecological operation program.(3)In the autumn flood season,when the reservoir operation is scheduled to enter the autumn water storage period,an autumn “tidal” ecological schedule with a period of 10 days will be implemented.The specific implementation will be: rainfall level,0.65 m,3 days,elevation level,0.64 m,7 days.In combination with the “tide-type” ecological operation method,we have studied the ecological operation to prevent and control of the tributaries algae blooms of the Three Gorges Reservoir.The "tide-type" ecological operation plans for different typical years and different inflow conditions obtained through this study can not only be The quantification of the tidal-type ecological operation method provides a certain reference,and it can also scientifically and reasonably guide the Three Gorges Reservoir to carry out the ecological operation practice of preventing and controlling tributary blooms. |
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