A method for regulating fish migration channels in cascade reservoir areas

Abstract

The present invention discloses a method for regulating fish migration channels in a cascade reservoir area, including: S1: conducting an experiment on the interactive influence mechanism of water temperature and flow velocity on fish migration; S2: combining the response of experimental fish upstream behavior and gonad development to different water temperature and flow velocity conditions, using a multiple regression analysis method to determine the quantitative relationship between fish migration quality characterization indicators and water temperature and flow velocity; S3: establishing a fish upstream trajectory prediction model under different water temperature and flow velocity combination conditions; S4: constructing and verifying a water temperature-hydrodynamic model of a target river section; S5: coupling the fish upstream trajectory prediction model with the water temperature-hydrodynamic model; S6: establishing a statistical relationship between fish upstream mode and flow change; S7: determining an ecological scheduling scheme for cascade power stations to ensure fish migration. The present invention solves the problem that the slow flow conditions in the cascade reservoir area are not conducive to fish migration and hinder the natural reproduction of fish, and ensures that spawning parent fish can smoothly pass through the slow flow river section in the reservoir area and migrate to the upstream or tributary spawning grounds.

Description

Technical Field

[0001] The invention relates to a method for regulating fish migration channels in a cascade reservoir area, and belongs to the technical field of reservoir ecological regulation. Background Art

[0002] Reproductive migration is the premise and basis for fish spawning. Unlike sedentary fish, migratory fish and semi-migratory fish often need to go through a certain distance of reproductive migration before spawning to complete the preparation of gonadal development before spawning and reach a suitable spawning ground. At present, the research on the impact of fish reproductive migration mainly focuses on the following two aspects: first, by comparing the average flow velocity of the section, it is judged whether the controlled river section of the section meets the minimum flow velocity to stimulate fish migration, and by comparing the length of the river section that meets the minimum stimulation flow velocity for fish migration under different flow rates, the ecological flow during the migration period is determined, such as the patent documents "Method and Device for Determining Ecological Flow of Fish Migration" (Publication No. CN113468825A) and "A Method and System for Determining Fish Migration Channel" (Publication No. CN114065520A). The above research on fish migration channels and flow only considers a single indicator of flow velocity, and takes the river section as the basic unit, which has a large error.

[0003] The second is to use the Euler-Lagrange algorithm to simulate the movement rules of fish schools in the flow field, obtain the parameters such as the instantaneous displacement and swimming speed of fish schools in the flow field, and then obtain the movement trajectory of fish schools. This technology regards fish as simple particles, and simulates the positions and probability distributions that fish schools can reach at different times according to the swimming ability of fish schools in the fishway. It is generally aimed at the short-distance crossing of fish dams and is not suitable for analyzing the attraction and stimulation of complex conditions of reservoir flow and temperature fields on long-distance continuous migration of fish, such as the patent document "A Simulation Method for Fish Migration Behavior" (Publication No. CN116258081A). Summary of the invention

[0004] In view of the above problems, the present invention proposes a method for regulating fish migration channels in cascade reservoirs, conducts experiments on the interactive effects of flow velocity and water temperature on fish migration, clarifies the appropriate flow velocity threshold for stimulating fish migration under different water temperatures, and establishes a prediction model for fish upstream behavior under different water temperature and flow velocity combinations; uses a water temperature-hydrodynamic model to simulate the changes in flow field and temperature field in the cascade reservoir area, and divides the flow field into a number of units, compares the average flow velocity and water temperature of each unit, and determines the migration direction and trajectory; by increasing the reservoir discharge flow and lowering the operating water level during the scheduling period, a method for continuous regulation of migration channels in the "still water" river section of the reservoir area with the least impact on other functions and the largest coverage of the migration channel is formed, aiming to solve the problem that the slow flow conditions in the cascade reservoir area are not conducive to fish migration and hinder the natural reproduction of fish, and ensure that spawning broodstock can smoothly pass through the slow-flow river section of the reservoir area and migrate to the upstream or tributary spawning grounds.

[0005] The present invention is implemented as follows: a method for regulating fish migration channels in a cascade reservoir area, the method steps comprising:

[0006] S1: Conduct experiments on the interactive effects of water temperature and flow velocity on fish migration;

[0007] S2: Combined with the response of experimental fish upstream behavior and gonad development to different water temperature and flow conditions, the multiple regression analysis method was used to determine the quantitative relationship between fish migration quality characterization indicators and water temperature and flow rate, including: the relationship between fish upstream success rate and water temperature and flow rate, and the relationship between the increase in fish estradiol concentration and water temperature and flow rate response. The relationship is as follows:

[0008] MR = (-59.07543+4.36814×T+65.35111×v)×100%

[0009] E2 = (-5.22385 + 0.32565×T+ 8.16193×v)×100%

[0010] Where: MR is the success rate of fish upstreaming; E2 is the percentage increase of estradiol concentration; T is the water temperature, unit ℃; v is the flow velocity, unit m / s;

[0011] S3: Establish a fish upstream trajectory prediction model under different water temperature and flow rate combinations, introduce the upstream probability (Pm) index to characterize the attractiveness of the water temperature and flow rate combination to fish migration, and comprehensively consider the relationship between the upstream success rate and the increase in gonad development and water temperature and flow rate to form a fish upstream probability prediction model under different water temperatures and flow rates. This relationship can be used to determine the upstream probability under different flow rates and water temperature combinations:

[0012] Pm = (c1×MR+ c2×E2)×100% = (4.69×T+73.51×v-64.3)×100%

[0013] Where: Pm is the probability of upstream under different hydrological conditions; c1 and c2 are weight coefficients, both of which are 0.5 by default;

[0014] S4: Construct and verify the water temperature-hydrodynamic model of the target river section;

[0015] S5: coupling the fish upstream trajectory prediction model with the water temperature-hydrodynamic model, simulating the upstream channel range and behavior trajectory of fish under different flow rates, adding the fish upstream behavior prediction model to the hydrodynamic model through the ABM module, dividing different cells, and judging the flow direction and upstream probability of adjacent cells one by one;

[0016] S6: Establish statistical relationships between fish migration patterns and flow variations;

[0017] S7: Determine the ecological dispatching plan for cascade power stations to ensure fish migration.

[0018] Furthermore, the experiment on the interactive influence mechanism of water temperature and flow velocity on fish migration in step S1 specifically includes: using a natural river simulation experimental device to create different flow velocity and water temperature combinations; observing the sensing time of the experimental fish to the water flow and the upstream distance at different time periods under each combination condition; and determining the increase in the estradiol sex hormone concentration of the experimental fish relative to the experimental fish in the static water control group under different water temperature and flow velocity conditions.

[0019] Furthermore, the water temperature-hydrodynamic model in step S4 includes: constructing a MIKE 21 hydrodynamic model, dividing grid units, adjusting parameters such as the roughness coefficient and the eddy viscosity coefficient; simulating the change of water temperature along the way in combination with the ECO Lab environmental module; verifying the water level, water temperature, etc. according to the measured data of representative points until the simulation results are consistent with the measured data.

[0020] Furthermore, the selection criteria for determining the flow direction of adjacent cells cell by cell in step S5 are: ① the adjacent cell with a larger upstream probability Pm, ② the adjacent cell flows toward the original cell, and ③ the adjacent cell flow velocity is not greater than 1.5 m / s. The specific formula is:

[0021] def calculate_priority(T, v):

[0022] return (4.69×T+73.51×v-64.3) ×100%

[0023] valid_cells = []

[0024] for cell in neighbors:

[0025] if v[cell]<= 1.5

[0026] cell_direction = flow_direction[cell]+π /

[0027] if abs(cell_direction - current_direction) <np.pi / 4

[0028] valid_cells.append(cell)

[0029] if valid_cells:

[0030] priorities = [calculate_priority(T, v) for cell in valid_cells]

[0031] next_position = valid_cells[argmax(priorities)]

[0032] else:

[0033] next_position = current_position+π.

[0034] Furthermore, in step S6, the statistical relationship between the fish upstream movement pattern and flow rate change is a fitting relationship between the proportion of the potential migratory channel in each reservoir area to the total length of the reservoir area and the flow rate, wherein the potential migratory channel refers to the area that 50% of the fish can reach.

[0035] Furthermore, the ecological dispatching plan for the cascade power stations in S7 refers to the recommended downstream flow and process of the cascade power stations that can maintain the potential migration channels of fish in each reservoir area and have little impact on the power generation efficiency.

[0036] The beneficial effects of the present invention are:

[0037] (1) Comprehensive water temperature and flow rate requirements to predict fish upstream behavior. Through mechanism experiments, the flow rate thresholds that stimulate fish migration under different water temperatures are determined, and a fish upstream prediction model under different water temperature and flow rate combinations is established. Based on existing studies that use flow rate as a single indicator to stimulate fish migration, this invention considers the interactive influence mechanism of water temperature and flow rate to predict fish upstream behavior.

[0038] (2) Couple the water temperature-hydrodynamics-fish upstream behavior model to identify the fish migration path. The present invention divides the reservoir river into several units, couples the water temperature-hydrodynamics-fish upstream prediction model, determines the maximum possible path of fish migration cell by cell, and determines the continuous channel. Based on the existing simulation research on fish migration behavior in fishways, the present invention expands the simulation of migration behavior from the fishway scale to the natural river and reservoir scale, focusing on the hydrodynamic regulation to ensure long-distance continuous migration of fish under different water temperatures.

[0039] The present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a flowchart of the steps of the method of the present invention;

[0041] Figure 2 This is a graph showing the results of an experiment on the concentration of sex hormones in fish at different water temperatures and flow rates;

[0042] Figure 3 is a distribution map of river sections that meet the migratory hydrological conditions under different discharge flows in each reservoir area in Example 2;

[0043] Figure 4 This is a fish upstream trajectory map of Baihetan and Xiluodu reservoir areas in Example 2;

[0044] Figure 5 It is the proportion of river sections that meet the migratory hydrological conditions under different downstream discharges in each reservoir area in Example 2 to the total river length of the reservoir area. DETAILED DESCRIPTION

[0045] Embodiment 1:

[0046] This embodiment is a method for regulating fish migration channels in cascade reservoirs. Figures 1 to 5 As shown, the method steps include:

[0047] S1: Conduct experiments on the interactive effects of water temperature and flow velocity on fish migration;

[0048] S2: Combined with the response of experimental fish upstream behavior and gonad development to different water temperature and flow conditions, the multiple regression analysis method was used to determine the quantitative relationship between fish migration quality characterization indicators and water temperature and flow rate, including: the relationship between fish upstream success rate and water temperature and flow rate, and the relationship between the increase in fish estradiol concentration and water temperature and flow rate response. The relationship is as follows:

[0049] MR = (-59.07543+4.36814×T+65.35111×v)×100%

[0050] E2 = (-5.22385 + 0.32565×T+ 8.16193×v)×100%

[0051] Where: MR is the success rate of fish upstreaming; E2 is the percentage increase of estradiol concentration; T is the water temperature, unit ℃; v is the flow velocity, unit m / s;

[0052] S3: Establish a fish upstream trajectory prediction model under different water temperature and flow rate combinations, introduce the upstream probability (Pm) index to characterize the attractiveness of the water temperature and flow rate combination to fish migration, and comprehensively consider the relationship between the upstream success rate and the increase in gonad development and water temperature and flow rate to form a fish upstream probability prediction model under different water temperatures and flow rates. This relationship can be used to determine the upstream probability under different flow rates and water temperature combinations:

[0053] Pm = (c1×MR+ c2×E2)×100% = (4.69×T+73.51×v-64.3)×100%

[0054] Where: Pm is the probability of upstream under different hydrological conditions; c1 and c2 are weight coefficients, both of which are 0.5 by default;

[0055] S4: Construct and verify the water temperature-hydrodynamic model of the target river section;

[0056] S5: coupling the fish upstream trajectory prediction model with the water temperature-hydrodynamic model, simulating the upstream channel range and behavior trajectory of fish under different flow rates, adding the fish upstream behavior prediction model to the hydrodynamic model through the ABM module, dividing different cells, and judging the flow direction and upstream probability of adjacent cells one by one;

[0057] S6: Establish statistical relationships between fish migration patterns and flow variations;

[0058] S7: Determine the ecological dispatching plan for cascade power stations to ensure fish migration.

[0059] Specifically, step S1 conducts an experiment on the interactive influence mechanism of water temperature and flow velocity on fish migration. This embodiment preferably uses indoor simulation experiments to reveal the response law of gonad development with changes in water temperature and flow velocity during fish reproductive migration, and clarifies the water temperature, flow velocity thresholds and suitable combination conditions that effectively promote gonad development.

[0060] The basic steps of the experiment include:

[0061] ①Preparation before the experiment. After the experimental river was filled with water (water depth 0.5m), it was dried for 3 days and disinfected by adding copper sulfate (8mg / kg) reagent; 100 sexually mature adult fish (mixed males and females) over 3 years old from the same batch were selected as the experimental fish group, and the fish group was acclimated for 2-3 days to maintain the dissolved oxygen and pH levels, adapt to the experimental environment, maintain the activity of the fish group, and make the experimental fish group adapt to the pool environment. After the acclimation was completed, 10 fish were selected for biological measurement and dissection, and the weight, body length, degree of gonadal development and other indicators were recorded.

[0062] ② Water flow stimulation. Through the water temperature regulating device, each experimental river channel forms a different target water temperature, and the water temperature is controlled at the target temperature ±0.2℃; after turning on the water pump, adjust the opening of the rectifier grid to stabilize the flow rate of each experimental river channel at the experimental target flow rate, with an error of no more than ±0.02m / s. After stabilizing the water temperature and flow rate, the experimental fish are stimulated with intermittent water flow. Under flow rate stimulation, rest for 1 hour every 3 hours. The daily experimental time is 15 hours, and the experimental cycle lasts for 7 days. Serum sampling of the experimental fish population was carried out before the start of the experiment, on the third day of the experiment, and after the end of the experiment. The number of sample serum under each working condition was not less than 5, and the changes in blood hormone levels of the fish population under continuous stimulation of different water temperatures and flow rates were observed and statistically analyzed.

[0063] ③ Detection of gonadal development level. After completing the water flow stimulation, blood was drawn from the tail vein of the experimental fish. In order to minimize the error of the experimental operation, the experimental fish was anesthetized during the blood drawing process. Then the blood sample was refrigerated, centrifuged, and the serum was separated. Finally, the serum estradiol and testosterone concentrations were monitored using a spectrophotometer. The estradiol concentration is the main indicator of the gonadal development level. At the same time, the experimental fish were dissected and the gonadal index (GSI) and other indicators that characterize the gonadal tissue structure were measured as an auxiliary means of measuring the gonadal development level.

[0064] ⑤ In order to reduce the impact of the inconsistency of physiological activity and gonadal development of experimental fish, two parallel experiments were carried out under each hydrological combination, and each group of parallel experiments was carried out crosswise with different groups of fish from the same batch. The interval between each group of experiments was not less than two hours.

[0065] ⑥ According to the proposed hydrological element comparison plan, repeat step ② and conduct experiments on the effects of different water temperature / flow rate combinations on fish gonad development. Statistical experimental record parameters to obtain the critical water temperature, flow rate and suitable combination conditions that effectively stimulate the reproductive migration and gonad development of the four major carps.

[0066] Specifically, step S2 described in this embodiment combines the response relationship between the upstreaming behavior and gonad development of the experimental fish to different water temperatures and flow rates, and adopts a multivariate regression analysis method to determine the appropriate water temperature and flow rate conditions, including: the relationship between the upstreaming success rate of fish and water temperature and flow rate, the response relationship between the increase in fish estradiol concentration and water temperature and flow rate, and respectively establishes the fitting relationship between the upstreaming success rate (MR), the increase in sex hormone concentration (E2) and the flow rate and water temperature.

[0067] The upstream success rate refers to the ratio of the number of experimental fish that pass through the test river section within the specified time to the total number of experimental fish. According to multiple regression analysis, the relationship between the upstream success rate and water temperature and flow rate is as follows:

[0068] MR = (-59.07543+4.36814×T+65.35111×v)×100%

[0069] Where: MR is the success rate of fish upstreaming, E2 is the percentage increase of estradiol concentration, T is the water temperature, unit is ℃, v is the flow velocity, unit is m / s,

[0070] In the cloudy regression analysis, water temperature and flow velocity had significant effects on the success rate of upstream tracing (P < 0.05), and the correlation coefficient of the fitting formula R 2 =0.78.

[0071] The experimental results of fish sex hormone concentration at different water temperatures and flow rates are as follows Figure 2 As shown in Figure 2, according to multiple regression analysis, the relationship between the increase in estradiol concentration and water temperature and flow rate is as follows:

[0072] E2 = (-5.22385 + 0.32565×T+ 8.16193×v)×100%

[0073] Where: E2 is the increase in estradiol concentration, T is the water temperature, unit is ℃, v is the flow rate, unit is m / s.

[0074] In the cloudy regression analysis, water temperature and flow rate had significant effects on gonad development (P < 0.05), and the correlation coefficient of the fitting formula was R 2 =0.37.

[0075] S3: Establish a fish upstream trajectory prediction model under different water temperature and flow rate combinations, introduce the "upstream probability" (Pm) indicator to characterize the attractiveness of water temperature and flow rate combinations to fish migration. Comprehensively consider the relationship between upstream success rate and gonad development increase and water temperature and flow rate, and form the fish upstream probability formula under different water temperatures and flow rates, as shown below:

[0076] Pm = (c1×MR+ c2×E2)×100%

[0077] Where: Pm is the probability of upstream migration under different hydrological conditions, MR is the success rate of fish upstream migration, E2 is the increase in estradiol concentration, c1 and c2 are weight coefficients, both of which are 0.5 by default.

[0078] Substitute the relationship between MR, E2, water temperature and flow rate into the upward relationship:

[0079] Pm = (4.69×T+73.51×v-64.3)×100%

[0080] In S4, a two-dimensional water temperature-hydrodynamic model of the reservoir area is constructed, and the MIKE 21 model is used to divide the grid units. The roughness coefficient, eddy viscosity coefficient and other parameters are adjusted to simulate the flow velocity and water depth distribution of each grid unit. The ECOLab environmental module is used to simulate the change of water temperature along the way. The changes in water temperature and flow velocity in the reservoir area under different preset flow rates are analyzed, and the water level, water temperature, etc. are verified according to the measured data of representative points until the simulation results are consistent with the measured data.

[0081] Furthermore, the fish upstream trajectory prediction model described in S3 is coupled with the two-dimensional water temperature-hydrodynamic model of the reservoir area through the biological behavior simulation module. The basis for selecting the upstream path of fish in the model is: ① the adjacent cell with a larger upstream probability Pm; ② the flow direction of the adjacent cell is toward the original cell; ③ the flow velocity of the adjacent cell is not greater than 1.5m / s. The judgment statement is as follows:

[0082] # Define the relationship formula between flow rate and priority

[0083] def calculate_priority(T, v):

[0084] return (4.69×T+73.51×v-64.3) ×100%

[0085] # Select cells that meet the criteria

[0086] valid_cells = []

[0087] for cell in neighbors:

[0088] if v[cell]<= 1.5: # flow rate does not exceed 1.5m / s

[0089] cell_direction = flow_direction[cell]+π

[0090] if abs(cell_direction - current_direction) <np.pi / 4:

[0091] valid_cells.append(cell) : # The flow direction must be towards the current position

[0092] # Choose swimming direction based on priority

[0093] if valid_cells:

[0094] priorities = [calculate_priority(T, v) for cell in valid_cells]

[0095] next_position = valid_cells[argmax(priorities)]

[0096] else:

[0097] next_position = current_position+π.

[0098] Furthermore, the fish upstream trajectory prediction model and the water temperature-hydrodynamic coupling model are used to divide different cells, release model fish at the starting position of the downstream of the simulated river section, judge the flow direction and upstream probability of adjacent cells cell by cell, and simulate the upstream channel range and behavior trajectory of fish under different flow scenarios. The starting position is determined according to the flow velocity simulation results, and the area with a flow velocity greater than the critical flow velocity of 0.2m / s is selected for release.

[0099] Furthermore, based on the simulation results of the migration trajectory, the distance that 50% of the model fish can reach under each flow rate is taken as the length of the suitable migration channel, and a statistical relationship between the length of the suitable migration channel and the flow rate change is established. According to the inflection point of the statistical relationship, the suitable flow rate and effective migration area for maintaining the fish migration channel are determined.

[0100] Embodiment 2:

[0101] A preferred embodiment of the present invention is to use the Wudongde-Xiangjiaba cascade reservoirs in the lower reaches of the Jinsha River as the study area, and to construct a hydrodynamic model. The modeling range is from the Panzhihua hydrological station to Xiangjiaba, covering the Wudongde, Baihetan, Xiluodu, and Xiangjiaba reservoir areas, with a total length of about 721km. Based on the measured cross-sectional terrain data, a triangular grid is used to divide the calculation area into grids with a grid spacing of 30m-50m. Considering that the terrain changes in the riverbank zone are relatively steep, the size of the unstructured grid is appropriately adjusted according to the actual situation to more accurately describe the boundary conditions. The total number of model division units is 214,837, of which the Wudongde reservoir area is 208km long and has 61,258 divided grid units, the Baihetan reservoir area is 175km long and has 51,876 divided grid units, the Xiluodu reservoir area is 193km long and has 58,637 divided grid units, and the Xiangjiaba reservoir area is 145km long and has 43,066 divided grid units.

[0102] In the ABM module, the number of released particles is directly related to the simulation calculation time. In order to control the simulation calculation time, the simulation adopts the method of releasing 100 particles (model fish) at a time. At the beginning of the simulation, the reservoir area sets the release position according to the distribution of different flow channels with flow rates greater than 0.2m / s. The lower section of the dam is released in the downstream Luzhou section, and the release is all on the water surface. When the particles (model fish) move, only horizontal movement is considered, and the direction in the horizontal movement state is determined according to the simulated flow rate and water temperature.

[0103] The discharge flow scenario of the cascade power station is set to 1000-6000 m 3 / s, flow gradient interval is 500 m 3 / s, where the maximum flow rate is set to 6000 m 3 / s is based on the consideration that the full flow of the Jinxia cascade power station units is 6500-7500 m 3 / s. Excessive flow will seriously affect the power generation efficiency. The minimum flow is set to 1000 m 3 / s is based on the minimum measured flow in April in the downstream reservoir section of the Jinsha River in the past two years. The water levels of each reservoir area are set according to the normal water storage level. The hydrodynamic model is used to analyze the flow velocity distribution of the reservoir area under various scenarios. The flow velocity distribution under some scenarios is as follows: Figure 3 The distribution map of river sections that meet the hydrological conditions for migration under different downstream discharges in each reservoir area is shown in the figure. Based on the above model, the fish upstream trajectory is simulated. The schematic diagram of the fish upstream trajectory is shown in Figure 4 The upstream trajectories of fish in Baihetan and Xiluodu Reservoir are shown in the map.

[0104] Furthermore, the discharge scheme of cascade hydropower stations for maintaining fish migration channels is based on the restriction that 50% of the model fish can migrate upstream and the channel is continuous. The length and proportion of river sections that can meet the needs of fish migration in each reservoir area under different discharge scenarios are calculated, such as Figure 5 The proportion of river sections that meet the hydrological conditions for migration in the total length of the reservoir area at different discharge rates is shown in the figure. In general, as the discharge rate increases, the proportion of suitable migration channels in the reservoir area increases in a step-like manner. 3 / sThe first mutation point appears, and the proportion of suitable migratory sections reaches about 40%, 3500-4000 m 3 / sThe second mutation point appears, and the proportion of river sections suitable for migration exceeds 50%.

[0105] Among the above four reservoir areas, the proportion of suitable migratory channels in the Xiangjiaba Reservoir is most sensitive to flow changes. The difference in the proportion of suitable migratory channels between the highest and lowest flows is about 40%; the proportion of suitable migratory channels in the Wudongde Reservoir changes the least with the increase in flow. The difference in the proportion of suitable migratory channels between the highest and lowest flows is only 20%.

[0106] Combined with the growth rate of the length of the suitable migration channel in each reservoir area with the flow rate, the recommended discharge flow for maintaining the fish migration channel in each reservoir area is determined, as shown in Table 1. Among them, the average flow rate in the reservoir area from March to April is only 2000m 3 / s, while the average flow in the reservoir area from May to June is 3500-4000m 3 / s. Therefore, in March and April, with the goal of reaching the first inflection point and the basic requirement of 40% of the river section suitable for migration (except the Baihetan reservoir area), the discharge flow of Wudongde, Baihetan, Xiluodu and Xiangjiaba was set at 2500-3000 m 3 / s. In May and June, the flow of tributaries in the reservoir area increased. Considering the influx of tributaries from the Baihetan and Xiluodu reservoirs, the basic requirement was that the proportion of suitable migratory river sections should reach 50% (except the Baihetan reservoir area). At the same time, combined with the dispatching regulations of the hydropower station, the discharge flow should not be higher than the full-power flow of the unit. The discharge flow of Wudongde, Baihetan, Xiluodu and Xiangjiaba was set at 4500 m 3 / s, 5000 m 3 / s、4000 m 3 / s, 4000 m 3 / s. In May and June, due to the large target flow, the reservoir capacity was emptied before the flood season to stimulate fish migration. In addition, according to the swimming ability of fish during migration, the duration of ecological discharge in each reservoir area was set to 5 days.

[0107] Table 1 Recommended discharge flows of cascade reservoirs for maintaining migratory channels in the reservoir area

[0108] Reservoir name Wudongde Baihetan Xiluodu Xiangjiaba Suitable discharge flow (m³ / s) 4500 5000 4000-4500 4000 Length of suitable migratory channel (km) 122 76 104 83

[0109] Finally, it should be noted that the above is only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solution and implementation methods of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for regulating fish migration channels in cascade reservoirs, characterized in that: The method steps include: S1: Conduct experiments on the interactive effects of water temperature and flow velocity on fish migration; S2: Combined with the response of experimental fish upstream behavior and gonad development to different water temperature and flow conditions, the multiple regression analysis method was used to determine the quantitative relationship between fish migration quality characterization indicators and water temperature and flow rate, including: the quantitative relationship between fish upstream success rate and water temperature and flow rate, and the quantitative relationship between fish estradiol concentration increase and water temperature and flow rate. The relationship is as follows: MR = (-59.07543+4.36814×T+65.35111×v)×100% E2 = (-5.22385 + 0.32565×T+ 8.16193×v)×100% Where: MR is the success rate of fish upstreaming; E2 is the percentage increase of estradiol concentration; T is the water temperature, unit ℃; v is the flow velocity, unit m / s; S3: Establish a fish upstream trajectory prediction model under different water temperature and flow rate combinations, introduce the upstream probability Pm index to characterize the attractiveness of the water temperature and flow rate combination conditions to fish migration, and comprehensively consider the relationship between the upstream success rate and the increase in gonad development and water temperature and flow rate to form a fish upstream probability prediction model under different water temperatures and flow rates. This relationship can be used to determine the upstream probability under different flow rates and water temperature combinations: Pm = (c1×MR+ c2×E2)×100% = (4.69×T+73.51×v-64.3)×100% Where: Pm is the probability of upstream under different hydrological conditions; c1 and c2 are weight coefficients, both of which are 0.5 by default; S4: Construct and verify the water temperature-hydrodynamic model of the target river section; S5: coupling the fish upstream trajectory prediction model with the water temperature-hydrodynamic model, simulating the upstream channel range and behavior trajectory of fish under different flow rates, adding the fish upstream behavior prediction model to the hydrodynamic model through the ABM module, dividing different cells, and judging the flow direction and upstream probability of adjacent cells one by one; S6: Establish statistical relationships between fish migration patterns and flow variations; S7: Determine the ecological dispatching plan for cascade power stations to ensure fish migration.

2. The method for regulating fish migration channels in cascade reservoirs according to claim 1, characterized in that: The experiment on the interactive influence mechanism of water temperature and flow velocity on fish migration in step S1 specifically includes: using a natural river simulation experimental device to create different flow velocity and water temperature combinations; observing the induction time of the experimental fish to the water flow and the upstream distance at different time periods under each combination condition; and determining the increase in the estradiol sex hormone concentration of the experimental fish relative to the experimental fish in the static water control group under different water temperature and flow velocity conditions.

3. The method for regulating fish migration channels in cascade reservoirs according to claim 1, characterized in that: The water temperature-hydrodynamic model in step S4 includes: constructing a MIKE 21 hydrodynamic model, dividing grid units, adjusting roughness coefficient and eddy viscosity coefficient parameters; simulating the change of water temperature along the process in combination with the ECO Lab environment module; and verifying the water level and water temperature according to the measured data of representative points until the simulation results are consistent with the measured data.

4. The method for regulating fish migration channels in cascade reservoirs according to claim 1, characterized in that: The selection criteria for judging the flow direction of adjacent cells cell by cell in step S5 are: ① the adjacent cell with a larger upstream probability Pm, ② the adjacent cell flows toward the original cell, and ③ the adjacent cell flow velocity is not greater than 1.5 m / s.

5. The method for regulating fish migration channels in cascade reservoirs according to claim 1, characterized in that: In step S6, the statistical relationship between the fish upstream migration pattern and flow rate change is the fitting relationship between the proportion of the potential migratory channel in each reservoir area to the total length of the reservoir area and the flow rate, wherein the potential migratory channel refers to the area that 50% of the fish can reach.

6. The method according to claim 1, characterized in that: The ecological dispatching scheme of the cascade power stations in S7 refers to the recommended downstream flow and process of the cascade power stations that can maintain the potential migration channels of fish in each reservoir area and have little impact on the power generation efficiency.

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