Quick evaluation method of reservoir ecological regulation based on drifting fish egg resuspension characteristic flow velocity

Abstract

The present application relates to the reservoir ecological regulation rapid evaluation method based on the drift fish egg resuspension characteristic flow velocity, including: obtaining the physical parameters of fish eggs; determining the safety evaluation river section and calculation parameters; establishing a one-dimensional hydrodynamic model; establishing the vertical two-dimensional hydrodynamic model of the safety evaluation river section; running the one-dimensional hydrodynamic model, obtaining the distribution of along-the-way hydraulic elements; spawning ground flow velocity constraint test, eliminating the regulation scheme that does not satisfy the flow velocity constraint; selectively calculating the fish egg resuspension characteristic flow velocity, marking the traditional safety zone and the resuspension safety zone according to two-level rules; statistical evaluation of the safety area ratio in the range; outputting the regulation scheme that meets the ecological requirements. The present application is widely applied to the rapid ecological regulation decision of single-stage or cascade reservoir group, is suitable for various scenes that the spawning ground is located below the dam, the tail of the reservoir or between the two reservoirs, can independently regulate the downstream discharge of the upstream reservoir or the storage level of the downstream reservoir, and provides an efficient, scientific and practical pre-evaluation tool for the ecological regulation of hydropower engineering.

Description

Technical Field

[0001] This invention relates to a rapid assessment method for reservoir ecological scheduling based on the characteristic flow velocity of resuspended drifting fish eggs. It is an assessment method for the ecological impact of hydropower projects and a calculation method for assessing the impact of reservoir scheduling on the ecological environment. Background Technology

[0002] The fertilized eggs of drifting fish are slightly heavier than water. After being laid, they need to be suspended in the water by the current to float and complete embryonic development. Hydropower development has reduced the flow velocity in reservoirs, increasing the risk of drifting fish eggs settling.

[0003] Currently, reservoir ecological management mainly focuses on how to stimulate fish spawning by creating floodwaters, while paying insufficient attention to the drifting and hatching process of the eggs after they are laid. In the few management methods that consider the drifting of fish eggs, a fixed flow velocity threshold (such as 0.25 m / s) is usually used as the standard for judging whether the fish eggs can drift safely. That is, it is assumed that if the flow velocity is greater than the threshold, the fish eggs can be suspended and transported, and if it is less than the threshold, the fish eggs will sink to the bottom of the riverbed and die from lack of oxygen.

[0004] However, recent field surveys and experimental studies have shown that fish eggs do not necessarily die after settling on the riverbed. Under suitable hydrodynamic conditions, deposited fish eggs may be driven by water flow (such as local eddies) to resuspend and re-enter the water, continuing to be transported with the current and completing embryonic development. Experiments have found that even if the local flow velocity is below 0.25 m / s, as long as the hydraulic conditions such as eddy current are suitable, i.e., the resuspension characteristic velocity E... c Even when the threshold is exceeded, fish eggs can still be resuspended and effectively transported. Traditional single flow velocity threshold methods ignore resuspension, a key physical process in fish egg existence, leading to severely underestimated predictions of effective drift time, drift distance, and hatching success rate, thus limiting the potential of reservoir management for early fish resource protection.

[0005] The effectiveness of early resource conservation for fish species that lay drifting eggs largely depends on the accurate assessment of the hatching environment of the eggs. However, existing methods are either too conservative due to neglecting resuspension mechanisms or impractical due to excessively high simulation costs. Finding a way to reasonably reflect the physical mechanisms of egg resuspension within acceptable computational costs, and to achieve rapid quantitative assessment of the hatching environment support capacity of different scheduling schemes, is a crucial technological direction that urgently needs breakthrough in the field of ecological scheduling. Summary of the Invention

[0006] To overcome the problems of existing technologies, this invention proposes a rapid assessment method for reservoir ecological scheduling based on the characteristic flow velocity of resuspended drifting fish eggs. The method is applicable to the context of cascade hydropower development, and rapidly calculates the spatial proportion R of the target river section that satisfies both the direct drifting (i.e., "traditional safe zone") and resuspending conditions (i.e., "resuspending safe zone") of drifting fish eggs. good This method is used to evaluate and select a reasonable reservoir scheduling scheme. For each candidate scheduling scheme, the method only needs to run the hydrodynamic model once to calculate the resuspension characteristic velocity E at each hydrodynamic grid point in the target river segment. c The percentage of spaces that meet the resuspension conditions, R good This method serves as a rapid criterion for evaluating the merits of scheduling schemes. It avoids simulating the entire process of each fish egg individually, has high computational efficiency, and comprehensively considers the coupling effect of hydraulic factors such as flow velocity and eddy current with the physical characteristics of fish eggs. It overcomes the limitations of a single flow velocity threshold and can meet the practical needs of rapidly screening and evaluating a large number of candidate schemes in ecological scheduling.

[0007] The objective of this invention is achieved as follows: a rapid assessment method for reservoir ecological management based on the characteristic flow velocity of resuspended drifting fish eggs, the steps of which are as follows:

[0008] Step 1: Obtain the physical parameters of the target fish eggs and the critical threshold E of the resuspension characteristic flow velocity. crit To identify the target fish species that need to be protected during reservoir ecological management, physical characteristic parameters of the target fish eggs are obtained through literature review, expert consultation, or egg experiments. These parameters include: egg diameter d and egg density ρ. 卵 Settlement velocity V g and fish egg mass m;

[0009] Based on flume experiments, the entire process of fish egg settling, retention, and resuspension under different hydraulic conditions was observed, and synchronous fish egg movement trajectories and flow field data were obtained. The changes in kinetic and potential energy of the fish eggs were analyzed based on the principle of energy conservation, revealing that the critical point at which the energy change ΔE of the fish eggs changes from negative to positive corresponds to the transition from a settling / retention state to a resuspension state. Key factors were screened through correlation analysis, and based on the principle of dimensional homogeneity, a characteristic resuspension velocity E was constructed. c The formula:

[0010]

[0011] In the formula, E c The characteristic velocity for resuspension is U, in m / s; the resultant velocity at the location of the fish eggs is U, in m / s; F d The drag force of the water flow on the fish eggs is N; ω is the vorticity, s. -1 V g denoted as ρ, where m / s is the settling velocity of the fish eggs; M is the mass of the fish eggs, in kg.

[0012] E was obtained under various working conditions through a water tank experiment. c The value and the corresponding energy change ΔE of the fish eggs were used to determine whether resuspension had occurred. A generalized additive model (GAM) was used to fit the E value. c The curve showing the relationship between E and resuspension rate, with E corresponding to 100% resuspension rate. c The value is used as the critical threshold E crit .

[0013] Step 2, Determine the river section for safety assessment and calculate basic parameters: Determine the specific river section within the target river section where a safety assessment needs to be conducted, and calculate the basic parameters of that river section, including: the effective drift distance L of the fish eggs. drift The starting and ending cross sections of the safety assessment river section and the actual calculated length L of the river section. eval The total area of ​​the river section under safety assessment A total ;

[0014] Sub-step 2.1: Determine the start and end sections of the river segment for safety assessment.

[0015] The starting section for the safety assessment is the downstream boundary of the spawning grounds within the river section, i.e., the lower edge of the spawning grounds. Fish eggs released from any location within the spawning grounds must pass through this section to begin their downstream drift; therefore, this section serves as the starting point for the safety assessment.

[0016] The endpoint section is taken as an effective drifting distance L extending downstream from the starting section along the river channel. drift This is the endpoint. If a downstream reservoir dam is encountered within this range, the endpoint will be cut off at the dam site.

[0017] The actual river section length between the starting and ending cross sections is denoted as L. eval (L) eval ≤L drift );

[0018] Sub-step 2.2: Estimate the effective drift distance L of the fish eggs. drift :

[0019] The average flow velocity U under the multi-year average conditions of the studied river section was used. average The time required for embryonic development of the target fish species' eggs (T) inc Estimate the effective drift distance required for fish eggs to complete embryonic development: L drift =U average ×T inc ×3.6

[0020] In the formula: L drift The effective drift distance of the fish eggs is in km; U average To study the average flow velocity (m / s) under multi-year average conditions in the river section; Tinc The time required for embryonic development of the target fish eggs is given in hours; 3.6 is a unit conversion factor.

[0021] Sub-step 2.3: Estimate the total area A of the river section to be assessed for safety. total :

[0022] The total area of ​​the river section for safety assessment is estimated using the following formula:

[0023] A total =L eval ×H avg ;

[0024] In the formula: L eval To assess the actual length of the river section for safety purposes; H avg To assess the average water depth of the river section; the area here is the longitudinal section area of ​​the 2D elevation model, which will be used as the percentage of the safe zone R in subsequent statistical analysis. good Spatial reference;

[0025] Step 3, establish a one-dimensional hydrodynamic model:

[0026] Based on the actual conditions of the river section under study, a one-dimensional hydrodynamic model is established to provide upstream flow boundary and downstream water level boundary for the elevation two-dimensional hydrodynamic model;

[0027] Sub-step 3.1: Determine the modeling scope of the one-dimensional model:

[0028] The modeling scope of the one-dimensional model should cover the entire river section from the upstream boundary section to the downstream boundary section, with the specific scope determined based on the hydropower development scenario.

[0029] Scenario 3.11, Spawning grounds are located upstream of a single-stage reservoir: The modeling scope starts from the natural river channel upstream of the starting section of the spawning ground and ends at the reservoir dam site section;

[0030] Scenario 3.12, Spawning grounds are located downstream of a single-stage reservoir: The modeling scope starts from the reservoir dam site section and extends downstream to the end section of the assessment river segment determined in step 2 or a stable control section further downstream, to ensure that reliable water level values ​​at the end of the assessment river segment can be obtained.

[0031] Scenario 3.13, the spawning ground is located between two cascade reservoirs: the modeling scope starts from the cross-section of the dam site of the upper reservoir and ends at the cross-section of the dam site of the lower reservoir;

[0032] Sub-step 3.2: Establish a one-dimensional hydrodynamic model:

[0033] Based on topographic survey data and channel roughness parameters of the studied river section, a one-dimensional hydrodynamic model is established. The model can simulate the distribution of hydraulic elements such as water level and average flow velocity at each cross section along the river under different combinations of upstream flow and downstream water level.

[0034] Explanation of the spatial relationship between the one-dimensional model and the two-dimensional model:

[0035] The one-dimensional model covers the entire study river section, while the two-dimensional elevation model only covers the safety assessment river section determined in step 2. The one-dimensional model provides the two-dimensional model with: ① the flow rate at the starting section; ② the water level at the ending section. The two-dimensional model then calculates the velocity field and vorticity field within the safety assessment river section based on these parameters.

[0036] Step 4: Establish a two-dimensional hydrodynamic model of the elevation of the river section for safety assessment:

[0037] Sub-step 4.1, Model selection and modeling scope:

[0038] A two-dimensional hydrodynamic model with vertical orientation is adopted, and the modeling scope is completely consistent with the safety assessment river section determined in step 2: the x-direction is from the starting section to the ending section, and the z-direction is from the bottom of the riverbed to the free water surface;

[0039] Sub-step 4.2, Mesh generation and terrain input:

[0040] The x-direction uses a uniform or non-uniform grid, and the grid size should be determined according to the river section morphology and hydraulic gradient. The grid can be appropriately densified where the cross-section changes drastically, and appropriately widened in straight and uniform sections. The z-direction uses σ coordinates or fixed layers, with 10 to 30 vertical layers. The grid should be appropriately densified near the riverbed to accurately capture the bottom vorticity. The model's topographic data is generated based on interpolation of the measured cross-section topography.

[0041] The governing equations and boundary condition types of the model:

[0042] The model solves the Navier-Stokes equations or shallow water equations for two-dimensional incompressible fluids along the flow direction and vertically, with turbulence closed or using the k-ε model or large eddy simulation.

[0043] The input boundary condition type of the model is: given upstream boundary flow Q 2D,up The downstream boundary is given a water level H. 2D,down Specifically, it is calculated in step 5, where the water surface is a free surface and the bottom is a solid wall boundary without slippage;

[0044] After the model is established, in step 6, the corresponding boundary conditions are substituted for each candidate scheduling scheme and the process is run to output the hydraulic parameters of each grid point.

[0045] Step 5, run the one-dimensional hydrodynamic model:

[0046] Sub-step 5.1: Set the boundary conditions for the one-dimensional model according to the scenario:

[0047] Boundary condition 5.11, the spawning ground is located upstream of a single-stage reservoir (reservoir area or tail): the upstream boundary is taken as the natural inflow discharge Q above the reservoir dam site.up The water level Z in front of the downstream boundary water intake dam down ;

[0048] Boundary condition 5.12, spawning grounds are located downstream of a single-stage reservoir (downstream of the dam): upstream boundary intake reservoir discharge Q up The downstream boundary is given the corresponding water level Z based on the water level-discharge relationship curve at the downstream boundary section of the one-dimensional model. down ;

[0049] Boundary condition 5.13: The spawning grounds are located between two cascade reservoirs: the upstream boundary is taken as the discharge flow Q from the upstream reservoir. up The downstream boundary is taken as the water level Z of the next-level reservoir. down ;

[0050] After setting the boundary conditions, run the one-dimensional hydrodynamic model;

[0051] Sub-step 5.2 involves repeating the process for multiple candidate scheduling schemes:

[0052] If there are multiple candidate scheduling schemes (such as different combinations of downstream flow rates or different combinations of downstream water levels), then execute sub-step 5.1 for each scheme to obtain the one-dimensional model running results corresponding to each scheme, which can be called by subsequent steps 6 and 7 respectively.

[0053] Step 6, Verification of spawning ground velocity constraints: Extract the maximum velocity U in the spawning ground region from the one-dimensional model results in Step 5. max , will U max With the preset spawning ground protection flow velocity threshold U limit Comparison:

[0054] If U max >U limit If the candidate scheduling scheme is deemed infeasible, it will be directly eliminated and will not participate in subsequent steps.

[0055] If U max ≤U limit Then proceed to step 7;

[0056] Step 7, extract the boundary conditions of the 2D model:

[0057] For the candidate scheduling schemes that pass the flow velocity constraint test in step 6, the upstream and downstream boundary conditions required for the 2D elevation model are extracted from the 1D model running results, as follows:

[0058] Sub-step 7.1: Extract the boundary conditions of the 2D model:

[0059] After the one-dimensional model is completed, extract the following two key data points from the calculation results:

[0060] The flow rate Q calculated by the one-dimensional model at the starting section of the river segment under safety assessment 2D,up ;

[0061] The water level H calculated by the one-dimensional model at the end section of the safety assessment river segment 2D,down ;

[0062] Extraction principle: Directly read the flow rate and water level values ​​output by the one-dimensional model at the starting and ending cross-sections. If the starting cross-section coincides with the upstream boundary cross-section of the one-dimensional model, Q 2D,up It equals the upstream boundary flow; if they do not coincide, it is the actual flow calculated by the model at that cross section. In both cases, the output data of the corresponding cross section can be read directly without manual distinction.

[0063] The basis for extracting these two data is that the calculation range of the two-dimensional elevation model in the x direction is equal to the safety assessment river section. In order to solve the velocity field and vorticity field within this range, it is necessary to give the flow boundary at the starting section and the water level boundary at the ending section. The two together constitute the boundary conditions of the two-dimensional model.

[0064] Sub-step 7.2: Assign the extracted data to the 2D elevation model: assign Q... 2D,up and H 2D,down These serve as the upstream flow boundary and downstream water level boundary of the 2D elevation model, respectively, for use in step 8.

[0065] Sub-step 7.3: Repeat the above operation for multiple candidate scheduling schemes: For multiple candidate scheduling schemes with different downstream flow combinations and different downstream water level combinations, execute sub-steps 7.1 to 7.2 respectively to obtain their corresponding Q. 2D,up and H 2D,down ;

[0066] Step 8, run the 2D hydrodynamic model of the facade and calculate the hydraulic parameters: extract the Q parameters from step 7. 2D,up As the upstream flow boundary, H 2D,down Substitute the downstream water level boundary into the 2D elevation model; after running the model, output the horizontal flow velocity u at each grid point. x Vertical flow velocity u z And based on this, calculate the resultant velocity U of the grid point. Calculate the vorticity ω at this grid point. ;

[0067] In the formula: x is the horizontal coordinate along the direction of water flow, in meters; z is the vertical coordinate, in meters.

[0068] If there are multiple candidate scheduling schemes, repeat step 8 for each scheme to obtain the velocity field and vorticity field corresponding to each scheme.

[0069] Step 9, selectively calculate the characteristic flow velocity E of fish egg resuspension. c And mark the safety zone: For each grid point within the safety assessment range, first determine its resultant velocity U:

[0070] If U ≥ 0.25 m / s, it is marked as a "traditional safe zone", and E does not need to be calculated. c ;

[0071] If U < 0.25 m / s, calculate the resuspension characteristic velocity E at this grid point. c And mark them according to the following rules;

[0072] E c The calculation formula is as follows:

[0073]

[0074] in:

[0075]

[0076] The physical meaning and value determination method of each symbol in the formula: E c : Resuspension characteristic velocity; U: Resultant velocity at each grid point, calculated in step 8; F d : The drag force of the water flow on the fish eggs; V g : The settling velocity of the fish eggs, obtained from step 1; ω: vorticity, calculated from step 8; m: mass of the fish eggs, obtained from step 1; ρ 水 : Density of water; ΔV: Relative velocity between fish eggs and water flow, approximated by the resultant velocity U at the grid points in engineering calculations (i.e., ΔV≈U); A e Fish eggs face the current; fish eggs are generalized as spheres, and their face area is calculated based on the area of ​​a circle. d is the diameter of the fish egg, obtained from step 1; C D : Drag coefficient, calculated based on the Reynolds number Re of the water flow in different zones;

[0077] Drag coefficient C D Calculated based on Re partitions:

[0078] Calculation of the Reynolds number Re of water flow:

[0079] Where: ρ 水 U is the density of the water; U is the resultant velocity; R is the hydraulic radius, R=A w / χ, where A w χ is the cross-sectional area of ​​the water passage, and μ is the wetted perimeter; μ is the dynamic viscosity of water.

[0080] Drag coefficient C D The partition calculation formula is as follows:

[0081] Stokes District :

[0082]

[0083] transition zone :

[0084]

[0085] Newton District The drag coefficient tends to a constant:

[0086] ;

[0087] E c With critical threshold E crit Comparison and labeling:

[0088] E was calculated c Then, compared with the critical threshold E obtained in step 1 crit Comparison:

[0089] If E c ≥E crit Marked as "Re-suspended Safe Zone";

[0090] If E c <E crit Marked as "unsafe zone";

[0091] Step 10: Calculate the percentage of safe areas (R) within the assessment scope. good : Calculate the total area A of the two types of safety grids: the traditional safety zone and the re-suspended safety zone. safe That is, summing all grid points marked as "traditional safety zone" and "re-suspended safety zone", the total area of ​​the safety zone is calculated using the following formula:

[0092]

[0093] Where: n safe Grid points marked as safe zones; Δx i Let Δz be the horizontal dimension of the i-th safety grid. i Let be the vertical dimension of the i-th safety grid; summation is performed only on grid points marked as "traditional safety zone" or "re-suspended safety zone";

[0094] Safety assessment scope: total area A total This has already been determined in sub-step 2.3;

[0095] Calculate the percentage of the safe zone:

[0096]

[0097] The indicator R good The overall assessment reflects the proportion of environments suitable for fish egg migration within the assessment area;

[0098] Step 11, determine whether the scheduling scheme meets the ecological requirements: For candidate scheduling schemes that pass the flow velocity constraint test, set R... good Compared with the preset target value R target Compare, if R good ≥R target If the ecological requirements are met, the scheduling scheme is deemed to meet the ecological requirements and can be used as a recommended scheme; otherwise, the scheme does not meet the ecological requirements.

[0099] R target The values ​​are determined based on the following:

[0100] Through steps 2-10, R target The safe zone R of the target river section under its natural state was calculated based on the natural hydrological data of the target river section before dam construction. good,natural Taking this as the restoration target, and based on the endangered status of the target fish species and the ecological restoration goals, different guarantee rates (R) are set at different levels. target A high guarantee rate can be achieved by taking R. target =R good,natural The guarantee rate is taken as R. target = 0.7×R good,natural ; Low guarantee rate takes R target = 0.5×R good,natural ;

[0101] Step 12, Multi-scheme comparison: Calculate the R0 for each of the multiple candidate scheduling schemes. good Choose R good The largest solution is considered the optimal solution, or all R solutions are selected. good ≥R target The options are provided for decision-makers to choose from;

[0102] Step 13, Output a scheduling scheme that meets ecological requirements: Output a scheduling scheme that meets ecological requirements, with parameters including: the upstream reservoir discharge flow or the downstream reservoir water level corresponding to the scheduling scheme, or the upstream reservoir discharge flow and the downstream reservoir water level and the corresponding R. good index.

[0103] The advantages and beneficial effects of this invention are: This invention is the first to demonstrate the characteristic flow rate E of fish egg resuspension. c The spatial distribution of water resources is incorporated into the rapid assessment of reservoir ecological management, with the proportion of safe areas R... goodUsing this as the core indicator, this invention can quickly determine the effectiveness of a scheduling scheme in protecting the resuspension environment of fish eggs without simulating individual fish egg transport, filling the technical gap in traditional methods where it is difficult to balance assessment accuracy and computational efficiency. This invention overcomes the limitations of traditional single velocity thresholds by further identifying "resuspension safety zones" with low velocity but suitable vorticity, while retaining the traditional safety zone. This re-includes areas mistakenly judged as unsafe by traditional methods within the safe range, making the assessment results more consistent with the actual resuspension capacity of fish eggs and avoiding the waste of ecological scheduling potential due to conservative assessments. This invention also considers the protection of the physical integrity of spawning grounds by introducing a maximum velocity constraint in the spawning grounds, avoiding the pursuit of excessively high R... good By employing excessive flow rates that cause sediment erosion and damage to spawning grounds, a synergistic assessment of the fish egg transport environment and spawning ground habitat protection was achieved. This invention is widely applicable to rapid ecological scheduling decisions in cascade reservoir groups, suitable for various scenarios where spawning grounds are located downstream of the dam, at the reservoir tail, or between two reservoirs. It can independently regulate upstream discharge flow or downstream water level, or jointly regulate them, providing an efficient, scientific, and practical pre-assessment tool for the ecological scheduling of hydropower projects. Attached Figure Description

[0104] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0105] Figure 1 This is a flowchart of the method described in an embodiment of the present invention. Detailed Implementation

[0106] Example:

[0107] This embodiment uses a rapid assessment method for reservoir ecological management based on the characteristic flow velocity of resuspended drifting fish eggs. It calculates the resultant velocity U and the resuspended characteristic flow velocity E of each grid in the target river segment using a hydrodynamic model. c Safety is determined using a two-tiered rule: for grids where U ≥ the critical velocity threshold for safe egg drift, the eggs are directly included in the "traditional safety zone"; for grids where U < the critical velocity threshold for safe egg drift but E c ≥E crit The grid is included in the "re-suspended safety zone". The proportion R of the total area of ​​the two types of safety zones to the assessment area is calculated. good This serves as a rapid criterion for judging the merits of scheduling schemes, avoiding time-consuming simulations of the entire fish egg process, and enabling rapid screening and optimization of scheduling schemes.

[0108] The method specifically includes the following steps, the process of which is as follows: Figure 1 As shown:

[0109] Step 1: Obtain the physical parameters of the target fish eggs and the critical threshold E of the resuspension characteristic flow velocity. crit: Identify the target fish species to be protected during reservoir ecological management (the target fish species should be fish that lay drifting eggs). Obtain the physical characteristic parameters of the target fish eggs by consulting literature, experts, or conducting fish egg experiments, including: egg diameter d, egg density ρ of the target fish species. 卵 Settlement velocity V g And the mass m of the fish eggs. (The fish eggs are generalized to be spheres.) )

[0110] Fish egg experiments were conducted. The egg diameter d of the target fish species was obtained through indoor measurements, and the density ρ of the target fish species eggs was obtained through salt selection. 卵 The settling velocity V of the target fish eggs was determined by indoor still water settling experiments. g Based on the experimental results, regression analysis was performed to summarize V. g The calculation formula, such as Alternatively, consult existing literature to obtain the above parameters.

[0111] The mass m of fish eggs can be obtained directly by weighing using a precision balance, or it can be generalized to a sphere for calculation: .

[0112] Based on flume experiments, physical analysis, and the principle of dimensional homogeneity, the resuspension characteristic velocity E is derived. c The formula. E was obtained under various operating conditions through a water tank experiment. c Whether the value and resuspension occur is determined by fitting E using a generalized additive model (GAM). c The relationship with resuspension rate was used to determine the critical threshold E of the characteristic flow velocity for fish egg resuspension. crit The method for determining this was as follows: fish egg resuspension experiments were conducted under different hydrodynamic conditions, and the E values ​​of each group of experiments were recorded. c The value and whether the corresponding resuspension occurs are fitted using a generalized additive model. c The curve showing the relationship between E and resuspension rate, with E corresponding to 100% resuspension rate. c The value is used as the critical threshold E crit .

[0113] Steps 2-10 are for a specific candidate scheduling scheme R good The calculation process:

[0114] Step 2, Determine the river section for safety assessment and calculate basic parameters: Determine the specific river section within the target river section where a safety assessment needs to be conducted, and calculate the basic parameters of that river section, including: the effective drift distance L of the fish eggs. drift The starting and ending cross sections of the safety assessment river section and the actual calculated length L of the river section. eval The total area of ​​the river section under safety assessment A total ;

[0115] Sub-step 2.1: Determine the start and end sections of the river segment for safety assessment.

[0116] The starting section for the safety assessment is the downstream boundary of the spawning grounds within the river section, i.e., the lower edge of the spawning grounds. Fish eggs released from any location within the spawning grounds must pass through this section to begin their downstream drift; therefore, this section serves as the starting point for the safety assessment.

[0117] The endpoint section is taken as an effective drifting distance L extending downstream from the starting section along the river channel. drift (L) drift The calculation method is shown in sub-step 2.2), which is the endpoint section. If a downstream reservoir dam is encountered within this range, the endpoint section is cut off to the dam site (fish eggs cannot safely pass through the dam to continue drifting downstream, and the assessment range should not exceed the dam site).

[0118] The actual river section length between the starting and ending cross sections is denoted as L. eval (L) eval ≤L drift );

[0119] Sub-step 2.2: Estimate the effective drift distance L of the fish eggs. drift :

[0120] The average flow velocity U under the multi-year average conditions of the studied river section was used. average (m / s, the average cross-sectional velocity under the multi-year average flow rate during the fish breeding season) and the embryonic development time T of the target fish fry eggs. inc (Hours, determined through literature review or experimental measurement), estimate the effective drift distance required for fish eggs to complete embryonic development: L drift =U average ×T inc ×3.6

[0121] In the formula: L drift The effective drift distance of the fish eggs is in km; U average To study the average flow velocity (m / s) under multi-year average conditions in the river section; T inc The time required for embryonic development of the target fish eggs is given in hours; 3.6 is a unit conversion factor.

[0122] Sub-step 2.3: Estimate the total area A of the river section to be assessed for safety. total :

[0123] The total area of ​​the river section for safety assessment is estimated using the following formula:

[0124] A total =L eval ×H avg ;

[0125] In the formula: L eval For safety assessment of the actual length of the river section, km; Havg To assess the average water depth of the river section, in meters; the area here is the longitudinal section area of ​​the 2D elevation model (measured as length × water depth), which will be used as the percentage of the safe zone R in subsequent statistical analysis. good The spatial reference. All candidate scheduling schemes adopt a unified Attotal value to ensure that R under different schemes good They are comparable.

[0126] Application instructions for three typical hydropower development scenarios:

[0127] This invention is applicable to the following three typical hydropower development scenarios. The boundary conditions of the hydrodynamic model are set differently in different scenarios, as detailed in step 5. The starting and ending sections of the river segment being evaluated in each scenario are determined according to the unified rules in sub-step 2.1, and are not affected by the scenario type.

[0128] (1) The spawning ground is located upstream of a single-stage reservoir (reservoir area or reservoir tail).

[0129] (2) The spawning grounds are located downstream of a single-stage reservoir (the section of the river below the dam);

[0130] (3) The spawning grounds are located between the two levels of the cascade reservoir.

[0131] Step 3, establish a one-dimensional hydrodynamic model:

[0132] Steps 3 and 4 establish one-dimensional and two-dimensional elevation hydrodynamic models respectively (only need to be established once, serving as the basic platform for subsequent multi-scheme calculations). Steps 5-7 then repeatedly call these two models for calculations for each candidate scheduling scheme. Separating the establishment from the execution is one of the key design features of this invention for achieving rapid multi-scheme comparison.

[0133] Based on the actual conditions of the studied river section, a one-dimensional hydrodynamic model is established to provide upstream flow boundaries and downstream water level boundaries for the elevation two-dimensional hydrodynamic model.

[0134] Sub-step 3.1: Determine the modeling scope of the one-dimensional model:

[0135] The modeling scope of the one-dimensional model should cover the entire river section from the upstream boundary section to the downstream boundary section, with the specific scope determined based on the hydropower development scenario.

[0136] Scenario 3.11, Spawning grounds are located upstream of a single-stage reservoir (reservoir area or tail of reservoir): The modeling scope starts from the natural river channel section upstream of the starting section of the spawning ground (the section not affected by the reservoir backwater) and ends at the reservoir dam site section.

[0137] Scenario 3.12, Spawning grounds are located downstream of a single-stage reservoir (downstream of the dam): The modeling scope starts from the dam site section and extends downstream to the end section of the assessment section determined in step 2 (or a more downstream stable control section) to ensure that reliable water level values ​​at the end of the assessment section can be obtained.

[0138] Scenario 3.13, the spawning ground is located between two cascade reservoirs: the modeling scope starts from the cross-section of the dam site of the upper reservoir and ends at the cross-section of the dam site of the lower reservoir.

[0139] The upstream and downstream boundaries of the one-dimensional model are located at the two ends of the modeling range, and their range is usually greater than or equal to the range of the safety assessment river section determined in step 2, so as to ensure that the upstream and downstream boundary conditions of the assessment river section are calculated by the model itself.

[0140] Sub-step 3.2: Establish a one-dimensional hydrodynamic model:

[0141] Based on topographic survey data of the studied river section (including at least the elevation and spacing information of each typical cross-section within the modeling scope) and channel roughness parameters, a one-dimensional hydrodynamic model is established (commercial software such as HEC-RAS and MIKE 11 can be used, or a self-written program can be used to solve the Saint-Venant equations). The model can simulate the distribution of hydraulic elements such as water level and average flow velocity at each cross-section along the river under different combinations of upstream flow and downstream water level.

[0142] This one-dimensional model will be invoked in subsequent step 5 to calculate the distribution of hydraulic elements along the route under the candidate scheduling scheme.

[0143] Explanation of the spatial relationship between the one-dimensional model and the two-dimensional model:

[0144] The one-dimensional model covers the entire study river section (a relatively large area), while the two-dimensional elevation model only covers the safety assessment river section determined in step 2 (a relatively small area). The one-dimensional model provides the two-dimensional model with: ① the flow rate at the starting section; ② the water level at the ending section. Based on this, the two-dimensional model calculates the velocity field and vorticity field within the safety assessment river section.

[0145] Step 4: Establish a two-dimensional hydrodynamic model of the safety assessment river section: For the safety assessment river section determined in Step 2, establish its two-dimensional hydrodynamic model (a two-dimensional profile model along the flow direction x and vertical z) to solve the velocity field and vorticity field within the assessment range in Step 8.

[0146] Sub-step 4.1, Model selection and modeling scope:

[0147] The two-dimensional hydrodynamic model is adopted for the following reasons: ① The distribution difference of fish eggs in the cross section has little impact on resuspension and the lateral change can be ignored; ② The computational efficiency of the two-dimensional model is much higher than that of the three-dimensional model, which meets the needs of rapid evaluation of scheduling schemes; ③ It can retain the vertical velocity gradient, a key element in vorticity calculation.

[0148] The modeling scope is completely consistent with the safety assessment river section determined in step 2: the x-direction extends from the starting section (the downstream boundary of the spawning grounds) to the ending section (extending downstream from the starting section by L). eval (location), z direction from the bottom of the riverbed to the free water surface.

[0149] Sub-step 4.2, Mesh generation and terrain input:

[0150] The x-direction (flow direction) uses a uniform or non-uniform grid. The grid size should be determined based on the river morphology and hydraulic gradient. Grids can be finer in areas with drastic cross-sectional changes and wider in straight, uniform sections. Generally, the horizontal grid size is 10–100 m. The z-direction (vertical direction) uses σ-coordinates or fixed layers. The number of vertical layers is generally 10–30, and can be finer near the riverbed to accurately capture bottom vorticity. The model's topographic data is generated based on interpolated measured cross-sectional topography.

[0151] The governing equations and boundary condition types of the model:

[0152] The model solves the Navier-Stokes equations or shallow water equations for two-dimensional incompressible fluids along the flow direction (x) and vertical direction (z). Turbulence closure can be achieved using appropriate methods such as the k-ε model or large eddy simulation (LES).

[0153] The input boundary condition type of the model is: given upstream boundary flow Q 2D,up (Provided by step 7), downstream boundary given water level H 2D,down (Provided by step 7), the water surface is a free surface, and the bottom is a non-slip solid wall boundary.

[0154] After the model is established, in step 8, the corresponding boundary conditions are substituted for the scheduling scheme and the process is run to output the hydraulic parameters of each grid point.

[0155] Step 5: Run the one-dimensional hydrodynamic model: For each candidate scheduling scheme, run the one-dimensional hydrodynamic model of the target river section established in Step 3 to obtain the water level, flow rate, and velocity distribution at each cross-section along the river. The specific process is as follows:

[0156] Sub-step 5.1: Set the boundary conditions for the one-dimensional model according to the scenario:

[0157] Boundary condition 5.11, the spawning ground is located upstream of a single-stage reservoir (reservoir area or tail): the upstream boundary is taken as the natural inflow discharge Q above the reservoir dam site. up(Given by hydrological data or scheduling rules), the downstream boundary water level in front of the reservoir dam, Z. down (Given by the scheduling scheme).

[0158] Boundary condition 5.12, spawning grounds are located downstream of a single-stage reservoir (downstream of the dam): upstream boundary intake reservoir discharge Q up (Given by the scheduling scheme), the downstream boundary is given the corresponding water level Z based on the water level-discharge relationship curve at the downstream boundary section of the one-dimensional model. down .

[0159] Methods for obtaining the water level-discharge relationship curve: ① Establish a regression relationship using multiple sets of historically measured water level and discharge data for the cross-section; ② Calculate using the Manning formula based on the cross-sectional topography and roughness parameters; ③ Extract the water level-discharge correspondence using the calculation results of the established one-dimensional hydrodynamic model under multiple discharge conditions. Method ① should be preferred when available.

[0160] Boundary condition 5.13: The spawning grounds are located between two cascade reservoirs: the upstream boundary is taken as the discharge flow Q from the upstream reservoir. up (Given by the scheduling plan), the downstream boundary is taken as the water level Z of the next-level reservoir. down (Given by the scheduling scheme). If there are tributary inflows or diversions between the upstream dam site and the starting section of the assessed river segment, the one-dimensional model will automatically reflect its cumulative impact. Therefore, Q extracted in sub-step (II) 2D,up Possibly different from Q up This is a normal phenomenon.

[0161] After setting the boundary conditions, run the one-dimensional hydrodynamic model.

[0162] Sub-step 5.2: Repeatedly run multiple candidate scheduling schemes: If there are multiple candidate scheduling schemes (such as different combinations of downstream flow rates or different combinations of downstream water levels), then execute sub-step 5.1 for each scheme to obtain the one-dimensional model running results corresponding to each scheme, which can be called by subsequent steps 6 and 7 respectively.

[0163] Step 6, Verification of flow velocity constraints in spawning grounds:

[0164] From the results of the one-dimensional model run in step 5, the cross-sectional flow velocity of each section in the spawning site area is extracted, and the maximum value is taken as U. max . Will U max With the preset spawning ground protection flow velocity threshold U limit Comparison:

[0165] If U max > U limit If the candidate scheduling scheme is deemed infeasible, it will be directly eliminated and no further calculations will be performed.

[0166] If U max ≤ U limit Then proceed to step 7.

[0167] Among them, U limit The value is determined based on the characteristics of the spawning ground substrate and the spawning habits of fish. It can be estimated by the substrate initiation flow velocity formula (such as the Shields formula) or determined by referring to the relationship between the measured flow velocity and the spawning intensity on site.

[0168] Step 7, extract the boundary conditions of the 2D model:

[0169] For the candidate scheduling schemes that pass the flow velocity constraint test in step 6, the upstream and downstream boundary conditions required for the 2D elevation model are extracted from the 1D model running results, as follows:

[0170] Sub-step 7.1: Extract the boundary conditions of the 2D model:

[0171] After the one-dimensional model is completed, extract the following two key data points from the calculation results:

[0172] The flow rate Q calculated by the one-dimensional model at the starting section of the river segment under safety assessment 2D,up ;

[0173] The water level H calculated by the one-dimensional model at the end section of the safety assessment river segment 2D,down ;

[0174] Extraction principle: Directly read the flow rate and water level values ​​output by the one-dimensional model at the starting and ending cross-sections. If the starting cross-section coincides with the upstream boundary cross-section of the one-dimensional model, Q 2D,up It equals the upstream boundary flow; if they do not coincide, it is the actual flow calculated by the model at that cross section. In both cases, the output data of the corresponding cross section can be read directly without manual distinction.

[0175] The basis for extracting these two data is that the calculation range of the two-dimensional elevation model in the x direction is equal to the safety assessment river section. In order to solve the velocity field and vorticity field within this range, it is necessary to give the flow boundary at the starting section and the water level boundary at the ending section. The two together constitute the boundary conditions of the two-dimensional model.

[0176] Sub-step 7.2: Assign the extracted data to the 2D elevation model: assign Q... 2D,up and H 2D,down These serve as the upstream flow boundary and downstream water level boundary of the 2D elevation model, respectively, for use in step 8.

[0177] Sub-step 7.3: Repeat the above operation for multiple candidate scheduling schemes: For multiple candidate scheduling schemes with different downstream flow combinations and different downstream water level combinations, execute sub-steps 7.1 to 7.2 respectively to obtain their corresponding Q.2D,up and H 2D,down ;

[0178] Step 8: Run the 2D hydrodynamic model of the elevation and calculate hydraulic parameters such as vorticity: extract Q from step 5. 2D,up As the upstream flow boundary, H 2D,down Substitute the downstream water level boundary into the 2D elevation model. After running the model, output the horizontal flow velocity u at each grid point. x (m / s, along the direction of water flow x), vertical velocity u z (m / s, along the vertical z direction), and calculate the resultant velocity U at this grid point based on this. , m / s; calculate the vorticity ω at this grid point, s -1 The above parameters will be used for the resuspension characteristic flow rate E in step 9. c The calculation.

[0179] If there are multiple candidate scheduling schemes, repeat step 8 above for each scheme to obtain the velocity field and vorticity field corresponding to each scheme.

[0180] Step 9, selectively calculate the characteristic flow velocity E of fish egg resuspension. c And mark the safe zone:

[0181] For each grid point within the safety assessment area, first determine its merging velocity U:

[0182] If U ≥ 0.25 m / s, it is marked as a "traditional safe zone", and E does not need to be calculated. c ;

[0183] If U < 0.25 m / s, calculate the resuspension characteristic velocity E at this grid point. c The formula is as follows:

[0184]

[0185] in:

[0186]

[0187] The physical meaning and value determination method of each symbol in the formula: E c : Resuspension characteristic velocity, m / s; U: Resultant velocity at each grid point, m / s, calculated in step 8; F d ω: Dragging force of the water flow on the fish eggs, N; vorticity, s -1 V is calculated from step 8; g : Settling velocity of fish eggs, m / s, obtained from step 1; m: Mass of fish eggs, kg, obtained from step 1; ρ 水: Density of water, kg / m³, usually taken as 1000 kg / m³; ΔV: Relative velocity between fish eggs and water flow, m / s, approximated as the combined velocity U in engineering calculations (i.e., ΔV≈U); A e Fish egg surface area facing the current, m². Fish eggs are generalized as spheres, and their surface area facing the current is calculated based on the area of ​​a circle. d is the diameter of the fish egg, in meters, obtained from step 1; C D : Drag force coefficient, calculated based on the Reynolds number Re of the water flow.

[0188] E c Physical meaning of E: c The ratio of the work done by the drag force of the water flow on the fish eggs to the energy dissipated by the gravity settling of the fish eggs comprehensively reflects the coupling effect of flow velocity and eddy current on the resuspension of the fish eggs. E c The higher the value, the easier it is for fish eggs to be carried and resuspended by the water flow; when E c Exceeding the critical threshold E crit Resuspension can occur effectively at that time.

[0189] Drag coefficient C D The calculation is performed in partitions according to the Reynolds number Re of the water flow, where

[0190] Reynolds number Re:

[0191] Where: ρ 水 The density of water is kg / m³. 3 U is the resultant velocity, m / s; R is the hydraulic radius, R=A w / χ, where A w χ is the cross-sectional area of ​​the water passage, denoted as wetted perimeter, in meters; μ is the dynamic viscosity of water, in Pa·s, taken as 1.003 × 10⁻⁶. −3 Pa·s.

[0192] C D The partition calculation formula is as follows:

[0193] Stokes district ):

[0194]

[0195] Transition zone ( ):

[0196]

[0197] Newton District ( (The drag coefficient tends to be constant).

[0198]

[0199] The Stokes zone is characterized by the complete dominance of viscous forces in the water flow around the fish eggs. The viscous force is much greater than the inertial force, resulting in extremely smooth flow with no vortex shedding. The resistance to the fish eggs' movement mainly comes from the friction of the viscous force on the egg surface. The transition zone is characterized by the gradual increase in inertial forces as the water flows around the fish eggs. Under the combined action of viscous and inertial forces, vortices begin to appear behind the fish eggs in the direction of movement. The resistance to the fish eggs' movement is composed of frictional resistance and pressure drag. The Newtonian zone is characterized by the complete dominance of inertial forces as the water flow around the fish eggs. The flow has fully developed into turbulence, and a distinct vortex shedding zone forms behind the fish eggs in the direction of movement. The resistance to the fish eggs' movement is mainly pressure drag, i.e., the resistance caused by the pressure difference before and after the direction of movement. D It tends to a constant.

[0200] E c With critical threshold E crit Comparison and labeling:

[0201] E was calculated c Then, compared with the critical threshold E obtained in step 1 crit Comparison:

[0202] If Ec≥E crit Marked as "Re-suspended Safe Zone";

[0203] If Ec < E crit Marked as "unsafe zone";

[0204] Note: If U ≥ 0.25 m / s at a certain grid point, it is already considered safe according to traditional standards, and there is no need to calculate E again. c This is to retain the effectiveness of traditional methods while reducing unnecessary computation; for regions where U < 0.25 m / s, traditional methods deem it unsafe, but this invention uses E... c Further identify areas that actually possess resuspension capability due to suitable vortex volume and reclassify them into the safe range.

[0205] Step 10: Calculate the percentage of safe areas (R) within the assessment scope. good :

[0206] As mentioned above, the safe zone includes two types of grids:

[0207] Traditional safety zone: grid with U≥0.25m / s;

[0208] Resuspension safety zone: U < 0.25 m / s and Ec ≥ E crit The grid;

[0209] Calculate the total area A of the two types of security zones above. safeThat is, summing all grid points marked as "traditional safety zone" and "re-suspended safety zone", the total area of ​​the safety zone is calculated using the following formula:

[0210]

[0211] Where: n safe Grid points marked as safe zones (traditional safe zones or re-suspended safe zones); Δx i Let Δz be the horizontal dimension of the i-th safety grid, m; i Let m be the vertical dimension of the i-th safety grid; the summation is performed only on grid points marked as "traditional safety zone" or "re-suspended safety zone" (non-safe zone grids are not included in the summation).

[0212] and the total area A of the safety assessment scope determined in sub-step 2.3 total Calculate the percentage of the safe zone:

[0213]

[0214] The indicator R good It can comprehensively reflect the proportion of the environment suitable for fish egg transport (traditional high flow rate or resuspension effective zone) within the assessment range.

[0215] Step 11, determine whether the scheduling scheme meets the ecological requirements: for those that pass the flow velocity constraint test in Step 6 and complete R... good The calculated candidate scheduling schemes will be compared with R. good Compared with the preset target value R target Compare, if R good ≥R target If the ecological requirements are met, the scheduling scheme is deemed to meet the ecological requirements and can be used as a recommended scheme; otherwise, the scheme does not meet the ecological requirements.

[0216] R target The percentage R of the safe area during the fish breeding season in the target river section under natural (undammed) conditions can be used as a basis. good,natural Configure it as the recovery target.

[0217] R good,natural The value can be calculated using the natural hydrological data (natural water level, flow rate) before the dam is built, through steps 2 to 10.

[0218] Alternatively, different guarantee rates (R) can be set at different levels based on the endangered status of the target fish species and ecological restoration goals. target For example, high guarantee rate (strict protection): R target That is, R good,natural (Close to natural state); Medium guarantee rate (conventional protection) can be taken as R. target =0.7×R good,naturalLow guarantee rate (emergency dispatch): R can be taken. target =0.5×R good,natural .

[0219] Step 12, Multi-scheme comparison: Calculate the R0 for each of the multiple candidate scheduling schemes. good Choose R good The largest solution is considered the optimal solution, or all R solutions are selected. good ≥R target The options are provided for decision-makers to choose from. In R good Under similar or identical conditions, the option with a smaller discharge flow should be given priority (as it is more beneficial for reservoir storage and power generation).

[0220] Step 13, Output a scheduling scheme that meets ecological requirements: Output a scheduling scheme that meets ecological requirements, with parameters including: the upstream reservoir discharge flow or the downstream reservoir water level corresponding to the scheduling scheme, or the upstream reservoir discharge flow and the downstream reservoir water level and the corresponding R. good index.

[0221] Application examples:

[0222] Taking the Panzhihua section of the lower reaches of the Jinsha River as an example, we can quickly assess the dispatching schemes under different discharge flows.

[0223] This embodiment focuses on the section of the Jinsha River between the Guanyinyan Hydropower Station and the Wudongde Hydropower Station. This section contains abundant fish spawning grounds, the condition of which is influenced by both the upstream Guanyinyan Hydropower Station and the downstream Wudongde Hydropower Station. The target fish species, the round-mouthed copper fish (Coreius guichenoti), is endemic to the upper Yangtze River and a national second-class protected animal. Its reproduction has become a key focus of the power station's ecological operation. Its historical spawning grounds are located approximately 12 km downstream of the Sanduizi hydrological station. During the round-mouthed copper fish spawning season (May-July), the Wudongde Reservoir operates at a dead water level of 945m from mid-April to late July to prepare for the flood season.

[0224] Five downstream discharge flows from the upstream Guanyinyan Reservoir were selected as candidate scheduling schemes:

[0225] Option 1: The outflow rate from Guanyinyan Reservoir is Q = 3000 m³ / h 3 / s

[0226] Option 2: Q=2500m 3 / s

[0227] Option 3: Q = 2000 m 3 / s

[0228] Option 4: Q = 1450 m 3 / s

[0229] Option 5: Q=1000m 3 / s

[0230] This invention enables rapid evaluation and comparison of various solutions.

[0231] Step 1: Obtain the physical parameters of the target fish eggs and the critical threshold E of the resuspension characteristic flow velocity. crit :

[0232] The target fish species to be prioritized for protection in the hydropower scheduling of the lower reaches of the Jinsha River is the round-mouthed copper fish. Its average settling velocity was obtained through still water settling experiments, its density was obtained through salt selection, and its egg diameter was obtained through measurement. The specific physical characteristics are as follows:

[0233] Average density: ρ 卵 =1.008×10 3 kg / m 3

[0234] Average egg diameter: d = 0.005 m

[0235] Average settling velocity: V g =0.010m / s

[0236] Average fish egg weight:

[0237] E was obtained under various working conditions through a water tank experiment. c Whether the value and resuspension occur is determined by fitting E using a generalized additive model (GAM). c The relationship with resuspension rate was used to determine the critical threshold E of the characteristic flow velocity for fish egg resuspension. crit This involves conducting fish egg resuspension experiments under different hydrodynamic conditions and recording the E values ​​of each group of experiments. c The value and whether the corresponding resuspension occurs are fitted using a generalized additive model. c The curve showing the relationship between E and resuspension rate, with E corresponding to 100% resuspension rate. c The value is used as the critical threshold E crit =0.00244m / s.

[0238] Step 2, determine the river section for safety assessment and calculate basic parameters:

[0239] The average flow velocity U under multi-year average conditions of the river section was studied. average =0.5m / s (take the average flow rate during the breeding season as 1800m) 3 (Cross-sectional average velocity meter / s). Hatching time T for round-mouthed copper fish eggs. inc =32 hours (reference value). Estimate the effective drift distance L required for fish eggs to complete hatching. drift :

[0240] L drift =U average ×T inc ×3.6=57.6 km

[0241] According to historical data, the downstream boundary section of the spawning grounds of the round-mouthed copper fish is located at the Sanduizi hydrological station. Therefore, the starting section of the safety assessment section is taken at the location of the Sanduizi hydrological station.

[0242] The river extends 57.6 km downstream from the initial cross-section, and the final cross-section is located 57.6 km downstream. Investigations have revealed no large dams obstructing this area, thus no damming is necessary. Therefore, the actual length L of the safety assessment section is [determined]. eval =57.6km.

[0243] Safety assessment of the total area of ​​river section A total Estimate by multiplying the river section length by the average water depth. The average water depth of this river section is approximately 20m (based on the multi-year average flow), therefore:

[0244] A total =Length × Average water depth = 57.6km × 20m = 1.15km 2 .

[0245] The evaluation scope remains consistent across all candidate scheduling schemes to ensure that Ro is optimized under different schemes. good They are comparable.

[0246] Step 3: Establish a one-dimensional hydrodynamic model of the target river section:

[0247] This embodiment is a cascade hydropower station (Guanyinyan-Wudongde), with the spawning ground located between the two reservoirs. A one-dimensional hydrodynamic model (using HEC-RAS) was established from the Guanyinyan dam site to the Wudongde dam site (approximately 204 km in length).

[0248] A one-dimensional hydrodynamic model was established based on 100 measured topographic cross-sections of the studied river section. The river roughness parameter was set to 0.012~0.02. The model can simulate the water level, average flow velocity, etc. of each cross-section along the river under different combinations of upstream discharge and downstream constant water level.

[0249] Step 4: Establish a two-dimensional hydrodynamic model of the elevation of the river section for safety assessment:

[0250] For the 57.6km river section identified in step 2 for safety assessment, a two-dimensional hydrodynamic model (using CE-QUAL-W2) was established. The model has 20 vertical layers and a horizontal grid size of 100m. The model can solve for the velocity field along the flow direction (x) and vertical direction (z), outputting the horizontal velocity u at each grid point. x (m / s), vertical velocity u z (m / s), and based on this, calculate the resultant velocity U (m / s) and vorticity ω ( ) and other parameters.

[0251] Step 5: For a given candidate scheduling scheme, run a one-dimensional hydrodynamic model of the target river segment:

[0252] Scheme 3 (Q=2000m) 3 Let's take / s as an example.

[0253] The scheduling scheme provides the upstream Guanyinyan discharge flow rate Q. up =2000m 3 / s、Downstream Wudongde Dam upstream water level Z down =945.0m. Set the upstream boundary flow of the one-dimensional model to 2000m³. 3 / s, downstream water level boundary is 945.0m. Run a one-dimensional model.

[0254] Step 6, Verification of flow velocity constraints in spawning grounds:

[0255] Extract the maximum flow velocity U in the spawning site area from the results of the one-dimensional model. max Option 3 U max = 0.95m / s. Based on the substrate (pebbles) of the spawning grounds of the round-mouthed copper fish and the fish's reproductive habits, U is set... limit = 1.2 m / s. U in Scheme 3 max = 0.95 m / s ≤ 1.2 m / s, the flow velocity constraint test is passed, proceed to step 7.

[0256] Repeat steps 5 and 6 for the other candidate solutions to calculate U for solution 1. max =1.35 m / s. Based on the substrate (pebbles) of the spawning grounds of the round-mouthed copper fish and the fish's reproductive habits, U is set... limit = 1.2 m / s. U in Scheme 1 max = 1.35 m / s > 1.2 m / s, the flow velocity constraint test is not passed, and further steps will not be taken. Scheme 2 (U max =1.15m / s), Scheme 4 (U max =0.78 m / s), Scheme 5 (U max Both (=0.62m / s) passed the velocity constraint test, proceed to step 7.

[0257] Step 7, extract the boundary conditions of the 2D model:

[0258] The flow rate Q at the upstream boundary section (the starting section of the spawning ground, i.e., the section of the San Dui Zi hydrological station) of the safety assessment river segment is extracted from the one-dimensional model calculation results. 2D，up ; and the water level H at the downstream boundary section (the end section of the assessed river segment). 2D，down .

[0259] Since there are no tributaries flowing into Q between the Guanyinyan Dam site and the starting section of the spawning grounds. 2D，up =2000m 3 / s; H is calculated using a one-dimensional model. 2D，down =973.6m. Q 2D，up =2000m 3 / s and H 2D，down =973.6m serves as the upstream flow boundary and downstream water level boundary for the two-dimensional elevation model.

[0260] For schemes 2 to 5 that pass the flow velocity constraint test in step 6, their respective boundary conditions are extracted from the corresponding one-dimensional models.

[0261]

[0262] Step 8: Run the 2D hydrodynamic model of the facade and calculate the hydraulic parameters:

[0263] Substitute the boundary conditions obtained in step 7 into the 2D elevation model, run the model, and obtain the horizontal flow velocity u at each grid point within the safety assessment river section. x Vertical flow velocity u z And calculate the resultant velocity U and vorticity ω.

[0264] Step 9, selectively calculate the characteristic flow velocity E of fish egg resuspension. c And mark the safe zone.

[0265] Taking Scheme 3, which passed the test, as an example, for each grid point within the safety assessment scope:

[0266] If U ≥ 0.25 m / s, it is marked as a "traditional safe zone", and E does not need to be calculated. c .

[0267] If U < 0.25 m / s, calculate the resuspension characteristic velocity E at this grid point. c .

[0268]

[0269] in:

[0270]

[0271] Pick =1000kg / m 3 , ≈U, =1.96×10 -5 m 2 .

[0272] Based on Re selection The partitioning calculation formula, and then the calculation of F.d Substituting into the equation, we get E. c .

[0273] Reynolds number of water flow Dynamic viscosity .

[0274] Compare E c With critical threshold E crit =0.00244m / s: If E c If the speed is ≥0.00244 m / s, mark it as a "safe re-suspending zone"; otherwise, mark it as a "non-safe zone". Classify and mark all grid points under this scheme.

[0275] Step 10: Calculate the percentage of safe areas (R) within the assessment scope. good .

[0276] The safe zone includes two types of grids:

[0277] ① Traditional safety zone: grid with U ≥ 0.25 m / s; ② Resuspension safety zone: grid with U < 0.25 m / s and E c Grid with a speed of ≥0.00244 m / s.

[0278] The total area A of the statistical security grid safe The total area A of the assessment scope total =1.15km 2 Calculate the percentage of the safe zone:

[0279] R is calculated for scheme 3. good =84%.

[0280] Compare with other schemes, repeat steps 8-10, and obtain the R of each scheme. good as follows:

[0281]

[0282] Step 11: Determine whether the scheduling scheme meets the ecological requirements:

[0283] Using steps 2-10, the safe zone percentage R of the target river section under natural conditions was calculated using natural hydrological data (natural flow and water level) prior to dam construction in 2014. good,natural =80%, set different guarantee rate targets:

[0284] High guarantee rate (strict protection): R target =80% (close to natural state);

[0285] Medium guarantee rate (conventional protection): R target =0.7 × 80% = 56%;

[0286] Low guarantee rate (emergency dispatch): R target =0.5 × 80% = 40%;

[0287] With a high guarantee rate R target Taking 80% as an example, Schemes 2 and 3 are satisfied; Schemes 4 and 5 are not satisfied.

[0288] Step 12, Comparison of multiple options:

[0289] In satisfying R good Among feasible solutions with a success rate of ≥80% (high guarantee rate) and passing the flow constraint, solutions 2 and 3 have the highest R... good Both are 84%. Given that the flow rate of Scheme 3 is less than that of Scheme 2, which is beneficial to reservoir water storage and power generation, Scheme 3 is recommended as the optimal scheduling scheme.

[0290] Step 13: Output a scheduling scheme that meets ecological requirements.

[0291] Under the requirement of high guarantee rate, the recommended scheme is: upstream Guanyin Rock discharge flow rate Q = 2000 m³ / h 3 / s, downstream Wudongde Reservoir water level Z=945.0m, corresponding to R good =84%.

[0292] Under the requirement of a medium guarantee rate, if power generation benefits are also taken into account, Scheme 5 can be recommended: upstream Guanyin Rock discharge flow rate Q=1000m³ 3 / s, downstream Wudongde Reservoir water level Z=945.0m, corresponding to R good =70%, still meets the requirements.

[0293] To verify the accuracy of the hydrodynamic model used in this invention, the water level and flow velocity calculated by the model under each scheme were compared with the measured data from the Sanduizi hydrological station. Taking Scheme 3 (Q=2000 m³ / s) as an example, the model calculated the water level at the Sanduizi hydrological station to be 974.2 m, with an error of 0.2 m compared to the measured water level of 974.0 m at the same time; the calculated average flow velocity at the cross-section was 1.85 m / s, with an error of 3.9% compared to the measured value of 1.78 m / s. Both are within the acceptable range for engineering (water level error <0.5 m, flow velocity error <10%), indicating that the model can reasonably reflect the hydraulic characteristics of the target river section and meet the accuracy requirements of this invention.

[0294] Meanwhile, the one-dimensional hydrodynamic model used in this invention ( ) and the two-dimensional hydrodynamic model of the facade ( These are all standard models widely used both domestically and internationally, and their core solvers have been validated in numerous engineering practices. In this study, key settings such as mesh resolution, roughness parameters, and turbulence models were configured according to recommended values ​​in the literature (e.g., roughness of 0.012–0.02, 20 vertical layers) and with reference to modeling experience in similar river sections. The model boundary conditions were provided by the one-dimensional model, and the upstream and downstream water levels and flow data underwent consistency checks, meeting the requirements for stable model operation. The model setup method adopted has been applied and validated in ecological scheduling studies of multiple cascade reservoirs in the upper reaches of the Yangtze River, and the calculation results have reliable accuracy.

[0295] Finally, it should be noted that the above is only used to illustrate the technical solution of the present invention and not to limit it. Although the present invention has been described in detail with reference to the preferred arrangement, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solution of the present invention (such as the form of the reservoir, the scheduling scheme, the application of various formulas, the order of steps, etc.) without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A rapid assessment method for reservoir ecological regulation based on the characteristic flow velocity of resuspended drifting fish eggs, the steps of which are as follows: Step 1: Obtain the physical parameters of the target fish eggs and the critical threshold E of the resuspension characteristic flow velocity. crit To identify the target fish species that need to be protected during reservoir ecological management, physical characteristic parameters of the target fish eggs are obtained through literature review, expert consultation, or fish egg experiments, including: The egg diameter d and egg density ρ of the target fish species 卵 Settlement velocity V g and fish egg mass m; Based on the flume experiment, the entire process of "sinking-retention-re-suspension" of fish eggs was observed under different hydraulic conditions, and synchronous fish egg movement trajectory and flow field data were obtained. Based on the principle of energy conservation, the changes in kinetic and potential energy of fish eggs were analyzed, and a method for calculating the energy change ΔE of fish eggs was established. ΔE > 0 was used to determine resuspension. Key factors were screened through correlation analysis, and a characteristic resuspension velocity E was constructed based on the principle of dimensional homogeneity. c The formula; E is obtained under various working conditions through water tank experiments. c The value and the corresponding ΔE value are used to determine whether resuspension has occurred if ΔE > 0. A generalized additive model is used to fit E. c The curve showing the relationship between resuspension rate and E, with E corresponding to a resuspension rate of 100% as the metric. c The value is used as the critical threshold E crit ; Step 2, Determine the river section for safety assessment and calculate basic parameters: Determine the specific river section within the target river section where a safety assessment needs to be conducted, and calculate the basic parameters of that river section, including: the effective drift distance L of the fish eggs. drift The starting and ending cross sections of the safety assessment river section and the actual calculated length L of the river section. eval The total area of ​​the river section under safety assessment A total ; Sub-step 2.1, determine the starting and ending sections of the safety assessment river section: the starting section of the safety assessment river section is the downstream boundary section of the spawning grounds within the river section, i.e., the lower edge of the spawning grounds; after fish eggs are released from any location within the spawning grounds, they must pass through this section to begin drifting downstream, so this section is used as the starting point of the safety assessment. The endpoint section is taken as an effective drifting distance L extending downstream from the starting section along the river channel. drift This is the endpoint section. If a downstream reservoir dam is encountered within this range, the endpoint section will be cut off at the dam site. The actual river section length between the starting and ending cross sections is denoted as L. eval ; Sub-step 2.2: Estimate the effective drift distance L of the fish eggs. drift : The average flow velocity U under the multi-year average conditions of the studied river section was used. average The time required for embryonic development of the target fish species' eggs (T) inc Estimate the effective drift distance required for fish eggs to complete embryonic development: L drift =U average ×T inc ×3.6 In the formula: L drift The effective drift distance of fish eggs; U average To study the average flow velocity under multi-year average conditions in the river section; T inc The embryonic development time required for the target fish fry eggs; 3.6 is the unit conversion factor; Sub-step 2.3: Estimate the total area A of the river section to be assessed for safety. total : The total area of ​​the river section for safety assessment is estimated using the following formula: A total =L eval ×H avg ; In the formula: L eval To assess the actual length of the river section for safety purposes; H avg To assess the average water depth of the river section; the area here is the longitudinal section area of ​​the 2D elevation model, which will be used as the percentage of the safe zone R in subsequent statistical analysis. good Spatial reference; Step 3, establish a one-dimensional hydrodynamic model: Based on the actual conditions of the river section under study, a one-dimensional hydrodynamic model is established to provide upstream flow boundary and downstream water level boundary for the elevation two-dimensional hydrodynamic model; Sub-step 3.1: Determine the modeling scope of the one-dimensional model: The modeling scope of the one-dimensional model should cover the entire river section from the upstream boundary section to the downstream boundary section, with the specific scope determined based on the hydropower development scenario. Scenario 3.11, Spawning grounds are located upstream of a single-stage reservoir: The modeling scope starts from the natural river channel upstream of the starting section of the spawning ground and ends at the reservoir dam site section; Scenario 3.12, Spawning grounds are located downstream of a single-stage reservoir: The modeling scope starts from the reservoir dam site section and extends downstream to the end section of the assessment river segment determined in step 2 or a stable control section further downstream, to ensure that reliable water level values ​​at the end of the assessment river segment can be obtained. Scenario 3.13, the spawning ground is located between two cascade reservoirs: the modeling scope starts from the cross-section of the dam site of the upper reservoir and ends at the cross-section of the dam site of the lower reservoir; Sub-step 3.2: Establish a one-dimensional hydrodynamic model: Based on topographic survey data and channel roughness parameters of the studied river section, a one-dimensional hydrodynamic model is established. The model can simulate the distribution of hydraulic elements such as water level and average flow velocity at each cross section along the river under different combinations of upstream flow and downstream water level. Explanation of the spatial relationship between the one-dimensional model and the two-dimensional model: The one-dimensional model covers the entire study river section, while the two-dimensional elevation model only covers the safety assessment river section determined in step 2. The one-dimensional model provides the two-dimensional model with: ① the flow rate at the starting section; ② the water level at the ending section. The two-dimensional model then calculates the velocity field and vorticity field within the safety assessment river section based on these parameters. Step 4: Establish a two-dimensional hydrodynamic model of the elevation of the river section for safety assessment: Sub-step 4.1, Model selection and modeling scope: A two-dimensional hydrodynamic model with vertical orientation is adopted, and the modeling scope is completely consistent with the safety assessment river section determined in step 2: the x-direction is from the starting section to the ending section, and the z-direction is from the bottom of the riverbed to the free water surface; Sub-step 4.2, Mesh generation and terrain input: The x-direction uses a uniform or non-uniform grid, and the grid size should be determined according to the river section morphology and hydraulic gradient. The grid should be appropriately densified where the cross-section changes drastically, and appropriately widened in straight and uniform sections. The z-direction uses σ coordinates or fixed layers, with 10 to 30 vertical layers. The grid should be appropriately densified near the riverbed to accurately capture the bottom vorticity. The model's topographic data is generated based on interpolation of the measured cross-section topography. The governing equations and boundary condition types of the model: The model solves the Navier-Stokes equations or shallow water equations for two-dimensional incompressible fluids along the flow direction and vertically, with turbulence closed or using the k-ε model or large eddy simulation. The input boundary condition type of the model is: given upstream boundary flow Q 2D,up The downstream boundary is given a water level H. 2D,down Specifically, it is calculated in step 5, where the water surface is a free surface and the bottom is a solid wall boundary without slippage; After the model is established, in step 6, the corresponding boundary conditions are substituted for each candidate scheduling scheme and the process is run to output the hydraulic parameters of each grid point. Step 5, run the one-dimensional hydrodynamic model: For each candidate scheduling scheme, a one-dimensional model with boundary conditions is set and run to obtain the water level, flow rate, and velocity distribution at each cross-section along the route; the specific process is as follows: Sub-step 5.1: Set the boundary conditions for the one-dimensional model according to the scenario: Boundary condition 5.11, the spawning ground is located upstream of a single-stage reservoir: the upstream boundary is taken as the natural inflow discharge Q above the reservoir dam site. up The water level Z in front of the downstream boundary water intake dam down ; Boundary condition 5.12, spawning grounds are located downstream of a single-stage reservoir: upstream boundary intake reservoir discharge Q up The downstream boundary is given the corresponding water level Z based on the water level-discharge relationship curve at the downstream boundary section of the one-dimensional model. down ; Boundary condition 5.13: The spawning grounds are located between two cascade reservoirs: the upstream boundary is taken as the discharge flow Q from the upstream reservoir. up The downstream boundary is taken as the water level Z of the next-level reservoir. down ; After setting the boundary conditions, run the one-dimensional hydrodynamic model; Sub-step 5.2 involves repeating the process for multiple candidate scheduling schemes: If there are multiple candidate scheduling schemes, then execute sub-step 5.1 for each scheme to obtain the one-dimensional model running results corresponding to each scheme; Step 6, Verification of spawning ground velocity constraints: Extract the maximum velocity U in the spawning ground region from the results of the one-dimensional model run in Step 5. max , will U max With the preset spawning ground protection flow velocity threshold U limit Comparison: If U max >U limit If the candidate scheduling scheme is deemed infeasible, it will be directly eliminated and will not participate in subsequent steps. If U max ≤U limit Then proceed to step 7; Step 7, extract the boundary conditions of the 2D model: For the candidate scheduling schemes that pass the flow velocity constraint test in step 6, the upstream and downstream boundary conditions required for the 2D elevation model are extracted from the 1D model running results, as follows: Sub-step 7.1: Extract the boundary conditions of the 2D model: After the one-dimensional model is completed, extract the following two key data points from the calculation results: The flow rate Q at the starting section of the river section under safety assessment 2D,up ; Water level H at the end section of the safety assessment river segment 2D,down ; Extraction principle: Directly read the flow rate and water level values ​​output by the one-dimensional model at the starting and ending cross sections. If the starting cross section coincides with the upstream boundary cross section of the one-dimensional model, Q... 2D,up It equals the upstream boundary flow; if they do not coincide, it is the actual flow calculated by the model at that cross section. In both cases, the output data of the corresponding cross section can be read directly without manual distinction. The basis for extracting these two data is that the calculation range of the two-dimensional elevation model in the x direction is equal to the safety assessment river section. In order to solve the velocity field and vorticity field within this range, it is necessary to give the flow boundary at the starting section and the water level boundary at the ending section. The two together constitute the boundary conditions of the two-dimensional model. Sub-step 7.2: Assign the extracted data to the 2D elevation model: assign Q... 2D,up and H 2D,down These serve as the upstream flow boundary and downstream water level boundary of the 2D elevation model, respectively, for use in step 8. Sub-step 7.3: Repeat the above operation for multiple candidate scheduling schemes: For multiple candidate scheduling schemes with different downstream flow combinations and different downstream water level combinations, execute sub-steps 7.1 to 7.2 respectively to obtain their corresponding Q. 2D,up and H 2D,down ; Step 8, run the 2D hydrodynamic model of the facade and calculate the hydraulic parameters: extract the Q parameters from step 7. 2D,up As the upstream flow boundary, H 2D,down Substitute the downstream water level boundary into the 2D elevation model; after running the model, output the horizontal flow velocity u at each grid point. x Vertical flow velocity u z And based on this, calculate the resultant velocity U of the grid point. Calculate the vorticity ω at this grid point. ; Step 9, selectively calculate the characteristic flow velocity E of fish egg resuspension. c And mark the safety zone: For each grid point within the safety assessment range, first determine its resultant velocity U: If U ≥ 0.25 m / s, it is marked as "traditional safe zone", and E does not need to be calculated. c ; If U < 0.25 m / s, calculate the resuspension characteristic velocity E at this grid point. c And mark them according to the following rules; E c The calculation formula is as follows: in: The physical meaning and value determination method of each symbol in the formula: E c : Resuspension characteristic velocity; U: Resultant velocity at each grid point, calculated in step 8; F d : The drag force of the water flow on the fish eggs; V g : The settling velocity of the fish eggs, obtained from step 1; ω: vorticity, calculated from step 8; m: mass of the fish eggs, obtained from step 1; ρ 水 : Density of water; ΔV: Relative velocity between fish eggs and water flow, approximated as the resultant velocity U of grid points in engineering calculations; A e Fish eggs face the current; fish eggs are generalized as spheres, and their face area is calculated based on the area of ​​a circle. d is the diameter of the fish egg, obtained from step 1; C D : Drag force coefficient, calculated based on the Reynolds number Re of the water flow in different zones; Drag coefficient C D Calculated based on Re partitions: Calculation of the Reynolds number Re of water flow: Where: ρ 水 U is the density of the water; U is the resultant velocity; R is the hydraulic radius, R=A w / χ, where A w χ is the cross-sectional area of ​​the water passage, and μ is the wetted perimeter; μ is the dynamic viscosity of water. Drag coefficient C D The partition calculation formula is as follows: Stokes District : transition zone : Newton District The drag coefficient tends to a constant: ； E c With critical threshold E crit Comparison and labeling: E was calculated c Then, compared with the critical threshold E obtained in step 1 crit Comparison: If E c ≥E crit Marked as "Re-suspended safe zone"; If E c <E crit Marked as "unsafe zone"; Step 10: Calculate the percentage of safe areas (R) within the assessment scope. good : Calculate the total area A of the two types of safety grids: traditional safety zone and re-suspended safety zone. safe That is, summing all grid points marked as "traditional safety zone" and "re-suspended safety zone", the total area of ​​the safety zone is calculated using the following formula: Where: n safe Grid points marked as safe zones; Δx i Let Δz be the horizontal dimension of the i-th safety grid. i Let be the vertical dimension of the i-th safety grid; summation is performed only on grid points marked as "traditional safety zone" or "re-suspended safety zone"; Safety assessment scope: total area A total This has already been determined in sub-step 2.3; Calculate the percentage of the safe zone: The indicator R good The overall assessment reflects the proportion of environments suitable for fish egg migration within the assessment area; Step 11, determine whether the scheduling scheme meets the ecological requirements: For candidate scheduling schemes that pass the flow velocity constraint test, set R... good Compared with the preset target value R target Compare, if R good ≥R target If the ecological requirements are met, the scheduling scheme is deemed to meet the ecological requirements and can be used as a recommended scheme; otherwise, the scheme does not meet the ecological requirements. R target The values ​​are determined based on the following: Through steps 2-10, R target The safe zone R of the target river section under its natural state was calculated based on the natural hydrological data of the target river section before dam construction. good,natural Taking this as the restoration target, and based on the endangered status of the target fish species and the ecological restoration goals, different guarantee rates (R) are set at different levels. target A high guarantee rate can be achieved by taking R. target =R good,natural The guarantee rate is taken as R. target = 0.7×R good,natural ; Low guarantee rate takes R target = 0.5×R good,natural ; Step 12, Multi-scheme comparison: Calculate the R0 for each of the multiple candidate scheduling schemes. good Choose R good The largest solution is considered the optimal solution, or all R solutions are selected. good ≥R target The options are provided for decision-makers to choose from; Step 13, Output a scheduling scheme that meets ecological requirements: Output a scheduling scheme that meets ecological requirements, with parameters including: the upstream reservoir discharge flow or the downstream reservoir water level corresponding to the scheduling scheme, or the upstream reservoir discharge flow and the downstream reservoir water level and the corresponding R. good index.

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