Group ecological scheduling method for maximizing the satisfaction of different fish needs

Abstract

The present invention discloses a grouped ecological scheduling method that maximally meets the needs of different fish species, which relates to the technical field of reservoir ecological scheduling. This method conducts environmental DNA surveys to clarify the existing fish species in the study river section; groups according to the spawning water temperatures and spawning types of each species to determine the overall framework and scheduling timing of reservoir ecological scheduling; improves the evaluation of the suitability of spawning habitats to define the range of discharge flows that can maximally cover the spawning of indigenous fish during each regulation period; overall considers spawning stimulation and the restoration of natural hydrological processes to optimize key indicators such as the daily variation range of discharge flows; and finally coordinates the discharge flow and water level change constraints of fish with different spawning types to form a grouped and classified ecological scheduling optimization scheme that takes into account the differentiated needs of fish at different times.

Description

Technical Field

[0001] The present invention relates to the technical field of reservoir ecological regulation, and particularly to a grouped ecological regulation method that maximally meets the needs of different fish species. Background Art

[0002] The construction of reservoirs has caused the interruption of river continuity, which has changed the upstream and downstream hydrological processes, resulting in changes in aquatic habitat conditions such as water temperature, water depth, and flow velocity, and affecting the spawning of fish living in the river. Therefore, reservoir ecological regulation is a measure to reduce the impact of reservoir construction and operation on the river ecosystem.

[0003] Currently, in the prior art, the idea of reservoir ecological regulation mainly focuses on protecting the spawning needs of key fish species such as the "four major Chinese carps", which has significantly promoted the breeding scale of some fish species. However, the ecological reservoir regulation methods adopted in the prior art have not shown obvious effects on the restoration of fish species diversity.

[0004] Therefore, the present invention aims to provide a grouped ecological regulation method that maximally meets the needs of different fish species. From the perspective of promoting the spawning of more fish species, it groups according to the spawning time and type of fish, and conducts grouped classification ecological regulation that maximally meets the spawning needs of indigenous fish species, so as to solve the problems existing in the prior art. Summary of the Invention

[0005] The object of the present invention is to solve the above problems by providing a grouped ecological regulation method that maximally meets the needs of different fish species. Based on the existing reservoir ecological regulation technology, the method of the present invention proposes an optimized idea of grouped classification ecological regulation that takes into account the different needs of fish species; through environmental DNA surveys, it clarifies the existing fish species in the study reach; groups according to the spawning water temperature and spawning type of each species, divides the ecological regulation period and the fish species covered by each regulation period; determines the regulation timing of each ecological regulation period based on the correlation analysis between spawning scale and hydrological factors; improves the evaluation of spawning habitat suitability using the weighted average method, and defines the range of discharge flow that can maximally cover the spawning of indigenous fish in each regulation period; overall considers spawning stimulation and the restoration of natural hydrological processes, and optimizes key indicators such as the daily variation range of discharge flow; finally coordinates the discharge flow and water level change constraints of fish species with different spawning types to form an ecological regulation method that meets the needs of different fish species at different times.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] The present invention provides a grouped ecological regulation method that maximally meets the needs of different fish species, and the method includes the following steps:

[0008] S1. Obtain the existing fish species in the target reach through environmental DNA surveys;

[0009] S2. Group according to the spawning time, type and water temperature requirements of fish in the study area, and determine the overall framework of reservoir ecological regulation. The spawning types are mainly divided into adhesive-settling eggs and drifting eggs. Fish of the same spawning type are divided into 2-3 groups according to the spawning water temperature;

[0010] S3. Sort out the monitoring data of fish spawning amount and hydrological data such as water temperature and flow. Use the stepwise multiple regression model to analyze the correlation between spawning scale and hydrological data, clarify the key hydrological elements and thresholds affecting fish spawning, and determine the ecological regulation timing for each group according to the thresholds;

[0011] S4. Analyze the preferences of indigenous fish spawning habitat elements (including flow velocity, water depth, substrate) during each ecological regulation period, construct a two-dimensional hydrodynamic model, and use the improved habitat simulation method to determine the range of reservoir outflow that maximally stimulates fish spawning during each regulation period;

[0012] S5. Couple the habitat simulation method with the analysis of natural hydrological regime, analyze the water level and flow fluctuations under natural conditions during each regulation period, and determine indicators such as daily water level variation range and daily average flow variation range;

[0013] S6. For each group, coordinate the constraints of outflow and water level changes for fish laying adhesive-settling eggs and drifting eggs, define key indicators such as outflow and daily flow variation range that can maximally cover the spawning needs of each group of fish, and form an ecological regulation plan that takes into account the different needs of fish at different times.

[0014] Furthermore, during the process of collecting environmental DNA samples, there are no less than 3 sampling sections in each river section, no less than 3 sampling points in each section, and no less than 4 samples are collected at each point in different seasons; during the comprehensive species identification process, the finally determined species are collected at least at one-third of the points, and are collected no less than twice at the same section.

[0015] Furthermore, in step S3, the hydrological parameters for stepwise multiple regression analysis include: water temperature, flow on the spawning day, flow on the day before spawning, flow two days before spawning, increase in flow on the spawning day, increase in flow on the day before spawning, increase in flow two days before spawning, increase in water level during spawning flow, increase in water level on the day before spawning, increase in water level two days before spawning.

[0016] Furthermore, in step S4, the improved habitat simulation method specifically includes: to maximize the satisfaction of the habitat preferences of more fish within each group, the weighted average method is used to calculate the optimal values of habitat elements that stimulate the spawning of different indigenous fish; the weighted standard deviation is used to calculate the suitable intervals of each habitat element, and the t-test is used to verify the difference between the optimal value and the average value; the calculation formulas are formula (1) and formula (2) respectively:

[0017] S W =∑ ij (ni x j / ∑n i ) (Formula 1)

[0018]

[0019] Where: S W is the optimal value of the habitat element, where S represents habitat elements such as water depth and flow velocity; x i is the suitable value of the habitat element of species i; S SD is the weighted standard deviation of the habitat element, that is, the suitable interval of the habitat element; n i is the number of individuals of species i in the environmental DNA survey.

[0020] Furthermore, in step S4, the improved habitat simulation method is used to determine the range of the discharge flow of the hydropower station during the ecological regulation of different types of fish. Taking the adhesive and sinking egg fish as an example, the calculation formula is as follows:

[0021] WUA=f[Q] (Formula 3)

[0022]

[0023]

[0024]

[0025] Where: WUA is the effective habitat area, m 2 ; Q is the discharge flow, m 3 / s; f[] is the functional relationship between WUA and the flow; is the flow corresponding to the maximum value of the effective habitat area; is the lower limit value of the discharge flow suitable for the spawning of adhesive and sinking egg fish, is the upper limit value of the discharge flow suitable for the spawning of adhesive and sinking egg fish, m 3 / s.

[0026] Furthermore, in step S5, during the ecological regulation of the drifting egg fish, focus on creating a continuous rising water process to stimulate spawning and creating a gentle falling water process to support the drifting and hatching of fish eggs. The key index analysis of the rising-falling water process specifically includes: according to the daily measured data of spawning amount and flow, screening the pulsed flow process that effectively stimulates spawning in the current situation; analyzing the rising water indexes of the pulsed flow process, and defining the total water level rise standard ΔW std and the continuous rising water time standard t std according to the 90% assurance rate requirement; based on the above rising water process standards, analyzing the long-term sequence of natural daily flow data of the cross-section of the hydrological station adjacent to the spawning ground, and screening out those that meet both ΔW std and Δt stdFor all rising water processes, according to the 75% guarantee rate requirement, the daily increase ΔQ of the outflow discharge during the ecological regulation period is finally determined 漂 , and the duration t of the rising water 漂 .

[0027] Furthermore, in step S5, during the ecological regulation period for sticky and sedimentary egg fish, the daily variations of the reservoir outflow discharge and water level are mainly controlled to stimulate fish spawning and ensure that fish eggs are not exposed and die due to a sudden drop in the water level; among them, the daily water level variation ΔW 粘 is determined according to the maximum water level difference within consecutive N days during the spawning period (April - July) under natural flow field conditions, where N is the fish egg hatching time. The principle is to assume that the water level fluctuations within consecutive N days, which exceed half of the days, under natural conditions will not affect the development of sticky and sedimentary eggs; furthermore, the daily variation ΔQ of the outflow discharge of the hydropower station is determined according to the water level - discharge relationship 粘 ;

[0028]

[0029] ΔW 粘 =QUARTLLE(ΔW j , 3) (Formula 8)

[0030] ΔQ 粘 =g[ΔW 粘 (Formula 9)

[0031] In the formula: W i is the daily average water level on the i - th day, m; ΔW j is the maximum water level difference within consecutive N days during the spawning period under natural conditions, m; j takes values from 1 to the maximum number of days in the spawning period, and the value of N is determined according to the fish egg hatching time; ΔW 粘 is the maximum daily water level variation during the ecological regulation period for sticky and sedimentary egg fish, m; ΔQ 粘 is the maximum daily flow variation during the ecological regulation period for sticky and sedimentary egg fish, m 3 / s; g[] is the water level - discharge relationship curve of the control section

[0032] Furthermore, in step S6, the ecological regulation scheme that takes into account the different needs of fish specifically includes: the outflow discharge takes the union of the suitable flow ranges of different spawning types of fish, and a rising water process is created to stimulate the spawning of drifting egg fish, but the rising - falling water process considers the constraint of the maximum daily water level variation to meet the spawning habitat of sticky and sedimentary egg fish; the key control indicators of the regulation scheme include the initial outflow discharge Q 初 , the daily average flow increase ΔQ 涨 , the duration t of the rising water 涨 , the daily average flow decrease ΔQ 退 , the duration t of the falling water 退 , and the maximum daily water level variation ΔW max; The calculation process of each index is as follows:

[0033] Initial value of the discharge flow rate Q 初 Not less than the lower limit value of the suitable flow rate Q for sticky and settling eggs 粘 And the lower limit value of the suitable flow rate Q for drifting eggs 漂 ; Peak value of the discharge flow rate Q 峰 Determined by the initial value and the total increase in the flow rate; the formula is as follows:

[0034]

[0035] Q 峰 ≥Q 初 +ΔQ 漂 ×t 漂 (Formula 11)

[0036] In the formula: Q 初 Is the starting value of the discharge flow rate for ecological regulation considering both sticky and settling eggs and drifting eggs, m 3 / s; Q 峰 Is the maximum value of the discharge flow rate, m 3 / s;

[0037] During the rising water process, giving priority to the water level stability of sticky and settling egg fish, it is required that the maximum daily variation range of the discharge flow rate ΔQ 涨 In principle, does not exceed ΔQ 粘 , then the formula for the daily increase in the discharge flow rate considering both sticky and settling eggs and drifting eggs is:

[0038]

[0039] When the rising water level requirement for drifting eggs exceeds the water level variation requirement for sticky and settling eggs, in order to ensure both the total increase in the water level and the daily water level variation, it is necessary to increase the continuous rising water time, and the continuous rising water time is

[0040] t 涨 ≥ROUNDUP[(Q 峰 -Q 初 ) / ΔQ 涨 , 0] (Formula 13)

[0041] During the falling water process, the daily decrease in the discharge flow rate is controlled according to the water level stability index of sticky egg fish, that is, ΔQ 退 =ΔQ 粘 , then the continuous rising water time is

[0042] t 退 ≥ROUNDUP[(Q 峰 -Q 初 ) / ΔQ 退 , 0] (Formula 14).

[0043] The difficulty and significance of the present invention in solving technical problems lie in:

[0044] Currently, in the prior art, the idea of ecological regulation is mainly to protect the spawning needs of key fish species such as the "Four Major Chinese Carps". Although it has significantly promoted the reproduction scale of some fish species, the effect on the restoration of fish species diversity is not obvious. Therefore, the solution of the present invention is from the perspective of promoting the spawning of more fish species, and groups are made according to the spawning time and type of fish, maximizing the grouped and classified ecological regulation that meets the spawning needs of indigenous fish. By using the solution of the present invention, the coverage rate of indigenous fish in the upper reaches of the Yangtze River reaches more than 90% through 4 times of grouped regulation.

[0045] In summary, compared with the prior art, the solution of the present invention has the following beneficial effects:

[0046] 1. In the prior art, the ecological regulation of fish with pelagic eggs focuses on the habitat needs of the "Four Major Chinese Carps". During the regulation period, the number of fish species stimulated to spawn is less than half of the existing species. In particular, the spawning effect of rare and endemic fish species such as Coreius guichenoti and Leptobotia elongata is not good. The solution of the present invention adopts a grouped and classified regulation method, where the grouping is based on spawning water temperature and the classification is based on spawning type, and accordingly improves the habitat suitability evaluation method, maximizing the coordination of the different spawning needs of different fish species. Through 4 times of grouped regulation, the coverage rate of indigenous fish in the upper reaches of the Yangtze River reaches more than 90%.

[0047] 2. In the prior art, the "base load power generation regulation" for fish with adhesive and sinking eggs and the "artificial flood peak regulation" for fish with pelagic eggs are carried out separately. However, the fish egg monitoring results show that the "base load power generation regulation" can also promote the spawning of fish with pelagic eggs during the period, and vice versa. The solution of the present invention combines the ecological regulation of the two spawning types in some periods, provided that the water temperature can stimulate some fish with adhesive and sinking eggs and fish with pelagic eggs at the same time. The main method is to create a rising water process to stimulate the spawning of fish eggs of fish with pelagic eggs, but the outflow and the daily water level variation during the rising - falling water process both consider the constraints of fish with adhesive and sinking eggs. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 shows the positions of environmental DNA sampling points in the lower reaches of the Jinsha River in the embodiment of the present invention;

[0049] Figure 2 shows the fish species composition in the lower reaches of the Jinsha River in the embodiment of the present invention;

[0050] Figure 3 shows the monitoring results of fish egg runoff and actual water temperature during the regulation period from 2020 to 2023 in the embodiment of the present invention;

[0051] Figure 4 shows the contribution rate of hydrological factors to spawning amount;

[0052] Figure 5 is the habitat suitability curve of fish species with adhesive and sinking eggs in the embodiments of the present invention;

[0053] Figure 6 is the habitat suitability curve of fish species with drifting eggs spawning from March to April in the embodiments of the present invention;

[0054] Figure 7 is the habitat suitability curve of fish species with drifting eggs spawning from May to June in the embodiments of the present invention;

[0055] Figure 8 is the variation of suitable habitats for fish in the lower reaches of the Jinsha River with the change of discharged flow in the embodiments of the present invention;

[0056] Figure 9 is the analysis of natural rising water process in the lower reaches of the Jinsha River in the embodiments of the present invention;

[0057] Figure 10 is the main fish egg hatching time in the lower reaches of the Jinsha River in the embodiments of the present invention;

[0058] Figure 11 is the method flow chart in the embodiments of the present invention. Detailed implementation manners

[0059] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solution of the present invention will be further described in detail below in conjunction with the embodiments and drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0060] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0061] Embodiment:

[0062] The embodiment of the present invention provides a grouped ecological regulation method that maximally meets the needs of different fish species. The method includes the following steps:

[0063] S1. Obtain the existing fish species in the target river section through environmental DNA surveys;

[0064] S2. Group according to the spawning time, type and water temperature requirements of fish in the study area, and determine the overall framework of reservoir ecological regulation. Among them, the spawning types are mainly divided into adhesive and sinking eggs and drifting eggs. Fish of the same spawning type are divided into 2-3 groups according to the spawning water temperature;

[0065] S3. Organize the monitoring data of fish spawning volume and hydrological data such as water temperature and flow rate. Use the stepwise multiple regression model to analyze the correlation between the spawning scale and hydrological data, clarify the key hydrological elements and thresholds affecting fish spawning, and determine the ecological regulation timing for each group according to the thresholds.

[0066] S4. Analyze the preferences of indigenous fish spawning habitat elements (including flow velocity, water depth, and substrate) during each ecological regulation period. Construct a two-dimensional hydrodynamic model and use the improved habitat simulation method to determine the range of reservoir discharge flows that maximize the stimulation of fish spawning during each regulation period.

[0067] S5. Coupling the habitat simulation method with the analysis of natural hydrological regimes, analyze the fluctuations of water level and flow rate under natural conditions during each regulation period, and determine indicators such as the daily water level variation range and the daily average flow rate variation range.

[0068] S6. For each group, coordinate the constraints on the discharge flow and water level changes of fish producing adhesive demersal eggs and pelagic eggs, define key indicators such as the discharge flow and the daily flow rate variation range that can maximize the coverage of the spawning requirements of each group of fish, and form an ecological regulation plan that takes into account the different needs of fish at different times.

[0069] Among them, during the process of collecting environmental DNA samples, there are no less than 3 sampling sections in each river section, no less than 3 sampling points in each section, and no less than 4 samples are collected at each point in different seasons; during the process of comprehensive species identification, the finally determined species are collected at least at one-third of the points, and are collected no less than twice at the same section.

[0070] In this embodiment, in step S3, the hydrological parameters for stepwise multiple regression analysis include: water temperature, the flow rate on the spawning day, the flow rate on the day before spawning, the flow rate two days before spawning, the increase in flow rate on the spawning day, the increase in flow rate on the day before spawning, the increase in flow rate two days before spawning, the increase in water level during spawning flow, the increase in water level on the day before spawning, and the increase in water level two days before spawning.

[0071] In this embodiment, in step S4, the improved habitat simulation method specifically includes: to maximize the satisfaction of the habitat preferences of more fish within each group, the weighted average method is used to calculate the optimal values of habitat elements that stimulate the spawning of different indigenous fish; the weighted standard deviation is used to calculate the suitable intervals of each habitat element, and the t-test is used to verify the difference between the optimal value and the average value; the calculation formulas are respectively the following formulas (1) and (2):

[0072] S W =∑ ij (n i x j / ∑ni) (Formula 1)

[0073]

[0074] Where: S W is the optimal value of the habitat element, where S represents habitat elements such as water depth and flow velocity; x i is the suitable value of the habitat element for species i; S SD is the weighted standard deviation of the habitat element, that is, the suitable interval of the habitat element; n i is the number of individuals of species i in the environmental DNA survey.

[0075] In this embodiment, in step S4, the improved habitat simulation method is used to determine the range of the outflow discharge of the hydropower station during the ecological regulation of different types of fish. Taking the adhesive and sinking egg fish as an example, the calculation formula is as follows:

[0076] WUA=f[Q] (Formula 3)

[0077]

[0078]

[0079]

[0080] Where: WUA is the effective habitat area, m 2 ; Q is the outflow discharge, m 3 / s; f[] is the functional relationship between WUA and the discharge; is the discharge corresponding to the maximum value of the effective habitat area; is the lower limit value of the outflow discharge suitable for the spawning of adhesive and sinking egg fish, is the upper limit value of the outflow discharge suitable for the spawning of adhesive and sinking egg fish, m 3 / s.

[0081] In this embodiment, in step S5, during the ecological regulation of the drifting egg fish, focus on creating a continuous rising water process to stimulate spawning and creating a gentle falling water process to support the drifting and hatching of fish eggs. The key index analysis of the rising-falling water process specifically includes: according to the daily measured data of the spawning amount and the discharge, screening the pulse discharge process that effectively stimulates spawning in the current situation; analyzing the rising water indexes of the pulse discharge process, and defining the total water level rise standard ΔW std and the continuous rising water time standard t std that can stimulate spawning according to the 90% assurance rate requirement; based on the above rising water process standards, analyzing the long-term sequence of natural daily discharge data of the cross-section of the hydrological station adjacent to the spawning ground, screening out all rising water processes that simultaneously meet ΔW std and Δt std , and finally determining the daily increase in the outflow discharge ΔQ 漂 and the rising water duration t 漂 during the ecological regulation according to the 75% assurance rate requirement.

[0082] In this embodiment, in step S5, during the ecological regulation of adhesive and sinking egg fish, the focus is on controlling the daily variation range of the reservoir discharge flow and water level, stimulating fish spawning, and ensuring that fish eggs are not exposed and die due to a sudden drop in water level; among them, the daily variation range of water level ΔW 粘 is determined according to the maximum water level difference within consecutive N days during the spawning period (April - July) under natural flow field conditions, where N is the fish egg hatching time. The principle is to assume that the water level fluctuations within consecutive N days with more than half of the days under natural conditions will not affect the development of adhesive and sinking eggs; furthermore, the daily variation range of the hydropower station discharge flow ΔQ is determined according to the water level - flow relationship 粘 ;

[0083]

[0084] ΔW 粘 =QUARTLLE(ΔW j , 3) (Formula 8)

[0085] ΔQ 粘 =g[ΔW 粘 (Formula 9)

[0086] In the formula: W i is the daily average water level on the i - th day, m; ΔW j is the maximum water level difference within consecutive N days during the spawning period under natural conditions, m; j takes values from 1 to the maximum number of days in the spawning period, and the value of N is determined according to the fish egg hatching time; ΔW 粘 is the maximum daily water level variation range during the ecological regulation period of adhesive and sinking egg fish, m; ΔQ 粘 is the maximum daily flow variation range during the ecological regulation period of adhesive and sinking egg fish, m 3 / s; g[] is the water level - flow relationship curve of the control section

[0087] In this embodiment, in step S6, the ecological regulation scheme that takes into account the differential needs of fish specifically includes: the discharge flow takes the union of the suitable flow ranges of different spawning types of fish, and creates a rising water process to stimulate the spawning of drift - egg fish eggs, but the rising - falling water process considers the constraint of the maximum daily water level variation range to meet the spawning habitat of adhesive and sinking egg fish; the key control indicators of the regulation scheme include the initial discharge flow Q 初 , the daily average flow increase ΔQ 涨 , the rising water duration t 涨 , the daily average flow decrease ΔQ 退 , the falling water duration t 退 , the maximum daily water level variation range ΔW max ; the calculation process of each indicator is as follows

[0088] The initial value of the discharge flow Q 初 is not less than the lower limit value of the suitable flow for adhesive and sinking eggs Q 粘 and the lower limit value of the suitable flow for drift eggs Q漂 ; The peak discharge Q during out - storage 峰 is determined by the initial value and the total discharge increase; the formula is as follows:

[0089]

[0090] Q 峰 ≥Q 初 +ΔQ 漂 ×t 漂 (Formula 11)

[0091] In the formula: Q 初 is the starting value of the out - storage discharge for ecological regulation considering both sticky - sediment eggs and drifting eggs, m 3 / s; Q 峰 is the maximum value of the out - storage discharge, m 3 / s;

[0092] During the rising - water process, giving priority to the water - level stability of fish with sticky - sediment eggs, it is required that the maximum daily variation ΔQ of the out - storage discharge 涨 in principle does not exceed ΔQ 粘 , then the formula for the daily increase of the out - storage discharge considering both sticky - sediment eggs and drifting eggs is:

[0093]

[0094] When the required rising - water amplitude of drifting eggs exceeds the water - level variation requirement of sticky - sediment eggs, to ensure both the total water - level increase and the daily water - level variation, the duration of continuous rising water needs to be increased, and the duration of rising water is

[0095] t 涨 ≥ROUNDUP[(Q 峰 -Q 初 ) / ΔQ 涨 , 0] (Formula 13)

[0096] During the falling - water process, the daily decrease of the out - storage discharge is controlled according to the water - level stability index of fish with sticky eggs, that is, ΔQ 退 =ΔQ 粘 , then the duration of rising water is

[0097] t 退 ≥ROUNDUP[(Q 峰 -Q 初 ) / ΔQ 退 , 0] (Formula 14).

[0098] The following are application examples of the embodiment scheme of the present invention:

[0099] 1. Sampling survey of fish in the lower reaches of the Jinsha River

[0100] To clarify the fish species composition in the lower reaches of the Jinsha River, 12 river sections of the main stream and major tributaries in the lower reaches of the Jinsha River were selected for on-site sampling (see Figure 1 ). Using environmental DNA detection technology, four samplings were carried out in June and October 2021, and January and April 2022 respectively. During the sampling process, to ensure the reliability of species information, there were no less than 3 sampling sections in each river section, no less than 3 sampling points in each section, and no less than four samples were collected at each point in different seasons. The finally determined species were collected at least at one-third of the points, and were collected no less than twice at the same section.

[0101] According to the sampling results, a total of 86 species of main fish are currently existing within the scheduling area, including 46 species of fish with adhesive and sinking eggs, 35 species of fish with drifting eggs, and 5 species of fish with floating eggs. Representative fish include rare and endemic fish in the upper reaches of the Yangtze River such as Coreius guichenoti, Leptobotia elongata, Rhinogobio ventralis, Rhinogobio cylindricus, schizothoracids, etc.

[0102] 2. Grouping of fish in the lower reaches of the Jinsha River and division of ecological scheduling periods

[0103] Analyze the suitable water temperature requirements for the spawning of main fish in the lower reaches of the Jinsha River. As shown in Table 1 below, the critical spawning water temperature of 11 species of fish is lower than 15 °C, accounting for 16% of the total, and at the same time, the critical spawning water temperature of about 40% of the fish is lower than 18 °C. According to the daily measured water temperature data of Xiangjiaba Hydrological Station and Yibin Hydrological Station, the peak spawning period of representative fish in the lower reaches of the Jinsha River is concentrated in April - June, and the spawning period of some fish is from March to April.

[0104] According to the monitoring results of the fish egg runoff and the actual water temperature during the scheduling periods from 2020 to 2023, it is recommended to further divide the critical regulation water temperature of fish with adhesive eggs from "15 °C" into 13 °C and 16 °C; divide the critical regulation water temperature of fish with drifting eggs from "18 °C" into 16 °C, 20 °C, and 22 °C, further expanding the coverage of the scheduling period to stimulate the spawning of fish with different spawning water temperature requirements. According to the suitable spawning water temperature of different fish, four batches of ecological scheduling experiments are carried out throughout the year. The first time is mainly for fish with adhesive and sinking eggs, the second time takes into account both fish with adhesive and sinking eggs and fish with drifting eggs, and the third and fourth times are mainly for fish with drifting eggs. The starting critical water temperatures are 13 °C, 16 °C, 20 °C, and 22 °C respectively. Through 4 schedulings, the spawning and breeding needs of 144 out of 158 species of fish in the scheduling area can be covered, accounting for 91%.

[0105] Table 1 Grouping of main fish in the lower reaches of the Jinsha River and suitable spawning water temperature range

[0106]

[0107]

[0108] 3. Determine the scheduling timing

[0109] Using statistical methods, analyze the daily egg production and the measured flow at the downstream section of Wudongde Dam, the downstream section of Baihetan Dam, and the Yibin section during the ecological regulation period of the cascade power stations in the lower reaches of the Jinsha River from 2022 to 2023 for fish species that produce drifting eggs, and clarify the key hydrological factors affecting the egg-laying of fish species that produce drifting eggs.

[0110] According to the monitoring egg-laying data and the corresponding changing trends of the flow and water level data, ten related hydrological factor indicators are formulated, and the indicators are set as shown in Table 2 below.

[0111] Table 2 Hydrological Factor Indicators

[0112]

[0113] Using the single-factor linear regression method, perform regression analysis on the ten hydrological factors at the three sections respectively with the egg production. At the same time, taking the absolute flow as a constraint condition, set the flow threshold, where the flow thresholds at the downstream of Wudongde and Baihetan Dams are 2050 m 3 / s, and the flow threshold of the Yibin section of the river is 4250 m 3 / s, and perform regression analysis on the egg production data exceeding the flow threshold. The significance P-values of the results are shown in Table 3.

[0114] Table 3 Single-factor Linear Regression Results and Significance before and after Setting the Flow Threshold

[0115]

[0116]

[0117] Note: When the P-value is less than 0.1, it passes the 90% significance test, and the influence is weakly significant; when the P-value is less than 0.05, it passes the 95% significance test, and the influence is significant.

[0118] From the results of single-factor linear regression, when the flow threshold is not set, none of the single factors below the Wudongde Dam show a significant impact on the spawning quantity; for the Baihetan Dam, the flow 2 days before spawning, the increase rate of the flow 2 days before spawning, and the increase rate of the water level 1 day before spawning show strong significance, the flow 1 day before spawning and the increase rate of the water level 2 days before spawning show weak significance; for the Yibin section, the increase rate of the daily flow and the increase rate of the daily water level show weak significance. After setting the flow threshold, the P-values of the single-factor regression tests for each factor generally show a downward trend, and the significance of the impact is enhanced. For example, the daily average flow, the flow 1 day before spawning, and the flow 2 days before spawning below the Wudongde Dam show strong significance on the spawning quantity; the daily average flow of the Baihetan Dam shows weak significance, and the flow 1 day before spawning changes from weak significance to strong significance; the impact of the increase rate of the water level of the Yibin section on the spawning quantity changes from weak significance to strong significance. Generally speaking, above the absolute flow threshold, the impact of the flow and water level (increase rate) on the spawning of fish with drifting eggs is relatively more significant.

[0119] Based on the spawning monitoring data of the 3 sections, using the set hydrological indicators as the dependent variables, through stepwise multiple regression analysis to eliminate collinear factors and screen significantly relevant environmental factors, the results are shown in Tables 4 and 5.

[0120] Table 4 Results of stepwise multiple regression models

[0121]

[0122] Table 5 Significance results of hydrological factors

[0123]

[0124] Based on the above results, the flow 1 day before spawning, the flow 2 days before spawning, the increase rate of the flow 2 days before spawning, the water level, the increase rate of the water level 1 day before spawning, and the increase rate of the water level 2 days before spawning have a linear impact on the spawning quantity. Especially for the factors of the flow 1 day before spawning and the flow 2 days before spawning, they show extremely significant impacts. Further, relative importance analysis is used to quantitatively explore the contribution rates of the above environmental factors to the spawning quantity, and the results are as Figure 4 shown. The results show that the flow 1 day before spawning and the flow 2 days before spawning have the greatest impact on the spawning quantity of fish eggs, with contribution rates of 40.6% and 33.5% respectively. Secondly, it is the increase rate of the flow 2 days before spawning, indicating that the spawning process mostly occurs 2 days after the flood.

[0125] Strengthen the monitoring of early fish resources throughout the spawning period, pay attention to the time interval between the scheduling period and the previous spawning concentration period, and use the combined water temperature when fish start spawning as the starting condition for scheduling. It is recommended that the starting time of ecological scheduling should comprehensively consider the water temperature and the natural law of fish spawning, and pay attention to the time interval between the scheduling period and the previous spawning peak period. According to the early fish resource monitoring data from 2020 to 2023, the scheduling experiment has the best effect when carried out about 5 days after the previous spawning peak period. At the same time, further strengthen the continuous monitoring of early fish resources, observe the law of fish spawning, and clarify the time interval between two spawning peak periods.

[0126] In addition to water temperature, it is recommended to carry out ecological scheduling during the natural flood period, and synergistically stimulate the artificial flood peak and natural flood, which is more conducive to fish spawning. According to the changes in fish egg runoff and flow at important monitoring sections from 2022 to 2023, a total of 10 ecological scheduling experiments for fish producing drifting eggs were carried out in Jinxia and the Three Gorges Reservoir, among which 4 were in the natural flood state. The daily maximum spawning volume during the scheduling period was significantly higher than that of the ecological scheduling during the non-natural flood period, and the peak spawning volume increased by more than 20%.

[0127] To sum up, it is recommended that in addition to the requirement that the water temperature meets the standard, the scheduling time should pay attention to an interval of more than 5 days from the previous spawning peak period, or after the first detection of fish spawning. For the "artificial flood peak" scheduling experiment, the scheduling period should be as close as possible 2 days after the occurrence of natural flood.

[0128] 4. Fish spawning flow velocity and water depth preferences during each scheduling period

[0129] The recommended value of the outflow discharge of the hydropower station is obtained by simulating the suitable habitats of representative fish. Through the analysis of the spawning habitat requirements of 68 representative fish species, the habitat suitability curves of fish in different stages and of different types are constructed. As Figures 5 to 7 shown, the habitat preferences of fish producing sticky and sinking eggs in different periods are basically similar, while the habitat preferences of fish producing drifting eggs in different periods vary greatly.

[0130] 5. Outflow discharge range during each scheduling period

[0131] Construct a two-dimensional hydrodynamic model of Mike 21 for each river section, and use the habitat simulation method to analyze the changes in the suitability of spawning habitats under different reservoir outflow discharges. The suitable habitat areas of fish under different outflow discharges are as Figure 8 shown. According to the habitat simulation method, calculate the suitable habitat area under different discharges, and determine the suitable discharge range for the spawning needs of fish producing drifting eggs. Take the discharge corresponding to 80% of the maximum habitat area as the starting discharge during the flood process. Then, from March to April, the starting outflow discharge of Wudongde and Baihetan hydropower stations should not be less than 1800 m 3 / s, and the starting outflow discharge of Xiangjiaba Hydropower Station should not be less than 2400 m 3 / s; From May to June, the initial discharge of Wudongde and Baihetan Hydropower Stations shall not be less than 2,400 m 3 / s, and the initial discharge of Xiangjiaba Hydropower Station shall not be less than 3,400 m 3 / s.

[0132] 6. Intra-day Variation of Outflow Discharge in Each Scheduling Period

[0133] The threshold parameters for ecological regulation should take the natural hydrological process as an important reference. Although it is impossible to completely restore the natural flow process, the formulation of parameters such as the rising water amplitude, the duration of rising water, and the intra-day variation amplitude can refer to the natural hydrological process.

[0134] Analyze the natural rising water process in the periods with less human activity interference at key sections of the main stream of the Yangtze River to determine the rising water amplitude and the duration of continuous rising water. According to the test results, the spawning process mostly occurs 2 days after the start of the rising water of the river. By statistically analyzing the rising water processes with a duration of (T≥2) days, the rising water process standard is set as "the daily increase is at least 5% of the multi-year average flow and lasts for 3 days", or "the number of days with a daily increase lower than 5% of the multi-year average flow is no more than 1 day and lasts for 4 days". Respectively, based on the measured daily flows of Huatan Station, Pingshan Station, Lizhuang Station, and Zhutuo Station from 1956 to 2000, analyze the average daily increase in flow, the average daily increase in water level, and the total increase in flow during each rising water process from March to June. According to Figure 9 the results shown, the duration of continuous rising water is not less than 4 days, the total increase in flow is not less than 60% of the multi-year average flow, the average daily increase in flow is not less than 12% of the multi-year average, and the average daily increase in water level is not less than 0.8 m. Then, based on the comprehensive habitat evaluation and the natural rising water process, determine the ecological regulation target plan. During the scheduling period, the total increase in the discharge of Wudongde and Baihetan is not less than 2,200 m 3 / s, and the average daily increase is about 450 m 3 / s. The total increase in the discharge of Xiangjiaba is not less than 2,800 m 3 / s, and the average daily increase is about 550 m 3 / s.

[0135] In addition, it is recommended to include the recession period in the ecological regulation period and put forward relevant control requirements. Take the fish egg hatching time as an important basis for determining the ecological regulation recession process. Analyze the fish egg hatching time and the spawning water temperature requirements of each species, construct the fitting relationship between the fish egg hatching time and the lowest spawning water temperature. According to the centroid and the confidence ellipse, the fish egg hatching time in the study area is about 60 h as a whole. Further analyze the fish egg hatching time of fish with different spawning periods and different spawning types, such as Figure 10 shown, the fish egg hatching time of fish that produce drifting eggs is mostly about 40 - 70 h, and the fish egg hatching time in each period is relatively consistent, while the hatching time of adhesive eggs varies greatly. Therefore, it is recommended that the recession process is generally not less than 3 days.

[0136] 7. Ecological regulation proposed plan

[0137] On the basis of the current ecological regulation test plan, further expand the regulation coverage area to stimulate the spawning of fish with different habitat requirements. According to the suitable spawning water temperatures of different fish species, it is recommended to carry out four batches of ecological regulation tests throughout the year. Among them, the first batch is mainly for fish species that produce sticky and sinking eggs, the second batch takes into account both fish species that produce sticky and sinking eggs and those that produce drifting eggs, and the third and fourth batches are mainly for fish species that produce drifting eggs. According to the suitable water temperatures during the peak spawning periods of representative fish species, the critical water temperatures for starting the ecological regulation tests are set at 13.5°C, 16°C, 20°C, and 22°C respectively. Through the four regulations, the spawning and breeding requirements of 144 out of 158 fish species in the regulated area can be covered, accounting for 91%.

[0138] Table 6 Division of ecological regulation periods and covered fish species of the Three Gorges and Jinxia cascade power stations

[0139]

[0140]

[0141] (1) The first ecological regulation

[0142] The first ecological regulation focuses on fish species that produce sticky eggs, targeting fish species such as schizothoracids that prefer low temperatures for spawning. The regulation timing is determined according to the water temperature range during the peak spawning period of schizothoracids, and it is required that the water temperature during the regulation period is not lower than 13.5°C. In addition, besides the requirement of reaching the standard water temperature for the regulation timing, it is necessary to note that the interval from the previous spawning peak is more than 5 days, or after the first detection of fish spawning.

[0143] During the regulation process, to create suitable habitat conditions for fish species that produce sticky eggs, focus on controlling the variation range of the downstream discharge of cascade reservoirs and reducing the daily water level decline in the river section downstream of the dam. The important parameters during the first ecological regulation period are shown in Table 7. Among them, the daily variation range of the discharge from the reservoir is obtained by converting the natural water level variation range in the river section downstream of the dam, and the control target of the water level variation range is determined based on the natural flow conditions; the duration is determined according to the hatching time of the fish eggs of representative fish species.

[0144] Table 7 Key points and main control parameters during the first ecological regulation period

[0145]

[0146] * Besides the requirement of reaching the standard water temperature for the regulation timing, it is necessary to note that the interval from the previous spawning peak is more than 5 days, or after the first detection of fish spawning

[0147] Key points for the regulation of Wudongde Hydropower Station during the first ecological regulation period: From March to April, when the water temperature in the river section downstream of Wudongde Dam reaches 13.5°C, carry out an ecological regulation test targeting fish species that produce sticky eggs at an appropriate time, ensure that the daily variation range of the water level in the spawning water area downstream of the dam does not exceed 1.0 m, and control the maximum daily flow variation range not to exceed 750 m3 / s, and the maximum downstream discharge should not exceed 2,600 m 3 / s for about 10 days. The specific implementation time and flow control process shall be dynamically adjusted in combination with real-time hydrological forecasts, early fish resource monitoring, and the operating conditions of the hydropower station. Note that the interval between the scheduling period and the previous spawning peak should be more than 5 days, or after the first detection of fish spawning.

[0148] Key points for the ecological regulation of Baihetan Hydropower Station during the first ecological regulation period: From March to April, when the water temperature in the river section downstream of Baihetan Dam reaches 13.5°C, conduct an ecological regulation experiment for fish spawning adhesive eggs at an appropriate time. Ensure that the daily water level variation amplitude in the spawning area downstream of the dam does not exceed 1.0 m, and control the daily maximum flow variation amplitude not to exceed 750 m 3 / s, and the maximum downstream discharge should not exceed 2,600 m 3 / s for about 10 days. The specific implementation time and flow control process shall be dynamically adjusted in combination with real-time hydrological forecasts, early fish resource monitoring, and the operating conditions of the hydropower station. Note that the interval between the scheduling period and the previous spawning peak should be more than 5 days, or after the first detection of fish spawning.

[0149] Key points for the ecological regulation of Xiangjiaba Hydropower Station during the first ecological regulation period: From March to April, when the water temperature in the Yibin river section reaches 13.5°C, conduct an ecological regulation experiment for fish spawning adhesive eggs at an appropriate time. Ensure that the daily water level variation amplitude in the Yibin river section does not exceed 1.5 m, and control the daily maximum flow variation amplitude not to exceed 1,000 m 3 / s, and the maximum downstream discharge should not exceed 3,400 m 3 / s for about 10 days. The specific implementation time and flow control process shall be dynamically adjusted in combination with real-time hydrological forecasts, early fish resource monitoring, and the operating conditions of the hydropower station. Note that the interval between the scheduling period and the previous spawning peak should be more than 5 days, or after the first detection of fish spawning.

[0150] Key points for the ecological regulation of the Three Gorges Hydropower Station during the first ecological regulation period: From April to June, in combination with the water level drawdown of the Three Gorges Reservoir, when the water temperature in the Three Gorges Reservoir area exceeds 17°C, conduct 1 - 2 ecological regulation experiments for fish spawning adhesive eggs in the reservoir area at an appropriate time. During the regulation period, control the daily water level drop in the reservoir area not to exceed 0.2 m, and the duration is not less than 4 days. The specific implementation time and flow control process shall be dynamically adjusted in combination with real-time hydrological forecasts, early fish resource monitoring, and the operating conditions of the hydropower station.

[0151] (2) The second ecological regulation

[0152] The second ecological operation focuses on the cascade hydropower stations in the lower reaches of the Jinsha River, taking into account fish species that lay adhesive eggs and drifting eggs. Among them, the key protected targets of fish species that lay drifting eggs are those that prefer low water temperature for spawning, such as Rhinogobio ventralis and Gobiobotia boulengeri. The operation timing is determined based on the water temperature range during the peak spawning period of fish spawning from April to May, and it is required that the water temperature during the operation is not lower than 16°C. In addition to the requirement of reaching the standard water temperature for the operation timing, it is noted that the interval from the previous spawning peak is more than 5 days. Moreover, according to the correlation analysis between the amount of fish eggs and the flow process in the early stage, the operation period should be as close as possible to 2 days after the occurrence of natural rising water.

[0153] During the operation process, in order to meet the requirements of the spawning grounds for fish species that lay adhesive and sinking eggs, it is necessary to control the daily stability of the water level, while taking into account the need for rising water stimulation for fish species that lay drifting eggs. It is required to gradually increase the downstream discharge of the reservoir and create a rising water process, and finally achieve a slow recession of the water level. During the recession process, it is necessary to avoid a rapid decline in the water level. Therefore, during the second ecological operation period, it is necessary to focus on controlling the initial discharge, the daily water level variation range, the daily average discharge increase rate, the duration of rising water, the recession time, and the daily discharge decline rate. The important parameters during the second ecological operation period are shown in Table 8. Among them, the starting rising discharge is determined by the habitat simulation method through analyzing the suitable discharge range for fish species that lay drifting eggs; the daily water level control target is determined based on the natural discharge conditions; the daily discharge increase rate and the duration are determined according to the natural rising water process, while paying attention to the constraint of the daily water level variation range; in addition, combining the monitoring data of fish early resources in the past 4 years, the spawning peak appears 3 - 6 days after the start of rising water. Therefore, the duration of rising water is set to be not less than 5 - 6 days, and the total duration is not less than 10 days; the daily discharge decline rate during the recession period is set according to the daily discharge variation during the first ecological operation period, and the recession duration is not less than 4 days.

[0154] Table 8 Key points and main control parameters during the second ecological operation period

[0155]

[0156] *In addition to the requirement of reaching the standard water temperature for the operation timing, it is noted that the interval from the previous spawning peak is more than 5 days and it is 2 days after the occurrence of natural rising water

[0157] Key points of the Wudongde Hydropower Station during the second ecological operation period: From April to May, when the water temperature in the river section downstream of the Wudongde Dam reaches 16°C, an ecological operation test will be carried out taking into account fish species that lay adhesive eggs and drifting eggs. During the rising water process, control the initial downstream discharge of the reservoir to be not less than 1800 m 3 / s, with a daily average increase rate of 300 - 450 m 3 / s, while ensuring that the daily water level variation range of the spawning water area in the river section downstream of the dam does not exceed 1.0 m; during the recession process, the daily average discharge decline rate does not exceed 750 m 3 / s, and ensure that the daily water level variation amplitude of the spawning waters downstream of the dam does not exceed 1.0 m; the total duration is about 10 days, including 5 - 6 days of rising water and 4 - 5 days of falling water. The specific implementation time and flow control process are dynamically adjusted in combination with real-time hydrological forecasts, early fish resource monitoring, and the operation conditions of the hydropower station. Note that the interval between the scheduling period and the previous spawning peak is more than 5 days, and 2 days after natural rising water occurs.

[0158] Key points for the ecological regulation of Baihetan Hydropower Station during the second ecological regulation period: From April to May, the water temperature in the river section downstream of Baihetan Dam reaches 16°C. Select an appropriate time to carry out ecological regulation tests that take into account both fish species laying adhesive eggs and fish species laying drifting eggs. During the rising water process, control the initial discharge of the reservoir not to be lower than 1800 m 3 / s, with a daily average increase of 300 - 450 m 3 / s, and at the same time ensure that the daily water level variation amplitude of the spawning waters downstream of Baihetan Dam does not exceed 1.0 m; during the falling water process, the daily average flow reduction does not exceed 750 m 3 / s, and ensure that the daily water level variation amplitude of the spawning waters downstream of Baihetan Dam does not exceed 1.0 m; the total duration is about 10 days, including 5 - 6 days of rising water and 4 - 5 days of falling water. The specific implementation time and flow control process are dynamically adjusted in combination with real-time hydrological forecasts, early fish resource monitoring, and the operation conditions of the hydropower station. Note that the interval between the scheduling period and the previous spawning peak is more than 5 days, and 2 days after natural rising water occurs.

[0159] Key points for the ecological regulation of Xiangjiaba Hydropower Station during the second ecological regulation period: From April to May, the water temperature in the Yibin river section reaches 16°C. Select an appropriate time to carry out ecological regulation tests that take into account both fish species laying adhesive eggs and fish species laying drifting eggs. During the rising water process, control the initial discharge of the reservoir not to be lower than 2400 m 3 / s, with a daily average increase of 400 - 550 m 3 / s, and at the same time ensure that the daily water level variation amplitude of the spawning waters in the Yibin river section does not exceed 1.5 m; during the falling water process, the daily average flow reduction does not exceed 1000 m 3 / s, and ensure that the daily water level variation amplitude of the spawning waters in the Yibin river section does not exceed 1.5 m; the total duration is about 10 days, including 5 - 6 days of rising water and 4 - 5 days of falling water. The specific implementation time and flow control process are dynamically adjusted in combination with real-time hydrological forecasts, early fish resource monitoring, and the operation conditions of the hydropower station. Note that the interval between the scheduling period and the previous spawning peak is more than 5 days, and 2 days after natural rising water occurs.

[0160] (3) The third and fourth ecological regulations

[0161] Third and fourth ecological regulation targeted fish species that like to spawn at high temperatures and lay drifting eggs, such as the "Four Major Chinese Carps" and loaches, and carried out joint regulation experiments of Wudongde-Baihetan and Xiluodu-Xiangjiaba-Three Gorges respectively. The timing of regulation was determined by comprehensively considering the water temperature range during the peak spawning period of spawning fish from May to June. It was required that the water temperature during the third regulation was not lower than 20 °C, and the water temperature during the fourth regulation was not lower than 23 °C. In addition to the requirement of reaching the standard water temperature, the timing of regulation should pay attention to an interval of more than 5 days from the previous spawning peak, and at the same time, the regulation period should be as close as possible 2 days after the occurrence of natural rising water.

[0162] During the regulation period, efforts were focused on creating a continuous rising water process. Compared with the second regulation, due to changes in the background flow conditions and different requirements of key protected fish for rising water stimulation, the rising water amplitude and absolute flow were larger, and the duration was shorter during the third and fourth ecological regulations. The important control parameters during the third and fourth ecological regulation periods are shown in Table 9. According to the spawning requirements of fish laying drifting eggs, key control parameters included the starting flow, daily flow increase, duration, and the decline rate of flow during the water recession process.

[0163] Table 9 Key points and main control parameters during the third and fourth ecological regulation periods

[0164]

[0165] *In addition to the requirement of reaching the standard water temperature, the timing of regulation should pay attention to an interval of more than 5 days from the previous spawning peak and 2 days after the occurrence of natural rising water

[0166] Key points of the joint regulation of Wudongde-Baihetan Hydropower Stations during the third and fourth ecological regulation periods: From May to June, when the water temperature in the river section downstream of Wudongde reaches 20 °C and 23 °C, a joint ecological regulation experiment of "artificial flood peak" for fish laying drifting eggs will be carried out at an appropriate time for each, creating a natural-like rising water - falling water process suitable for fish spawning and reproduction. During the regulation period, the initial discharge of Wudongde and Baihetan Hydropower Stations is not less than 2400 m 3 / s, the daily flow increase is not less than 570 m 3 / s / d, the duration of rising water is not less than 4 days, the daily flow decrease during the water recession stage is not higher than 750 m 3 / s / d, and the duration of water recession is about 3 - 4 days. The specific implementation time and flow control process will be dynamically adjusted in combination with real-time hydrological forecasts, early fish resource monitoring, and the operating conditions of hydropower stations. Pay attention to an interval of more than 5 days from the previous spawning peak and 2 days after the occurrence of natural rising water.

[0167] Key points of the joint operation of Wudongde - Baihetan Hydropower Stations during the third and fourth ecological operation periods: From May to July, when the water temperature in the Yibin section of the Yangtze River reaches 20°C and 23°C respectively, carry out a "man - made flood peak" joint ecological operation test for fish species that produce drifting eggs at an appropriate time, creating a natural - like rising - falling water process suitable for fish spawning and reproduction. During the operation period, the initial discharge of the Xiangjiaba Hydropower Station shall not be less than 3400 m 3 / s, and the daily increase in discharge shall not be less than 680 m 3 / s / d. The initial discharge of the Three Gorges Hydropower Station shall not be less than 10000 m 3 / s, and the daily increase in discharge shall be between 1000 - 2000 m 3 / s / d. The duration of the rising - water period shall not be less than 4 days. During the falling - water period, the daily decrease in discharge of the Xiangjiaba Hydropower Station shall not be higher than 750 m 3 / s / d, and the daily decrease in discharge of the Three Gorges Hydropower Station shall not be higher than 2000 m 3 / s / d. The duration of the falling - water period shall not be less than 3 - 4 days. The specific implementation time and discharge control process shall be dynamically adjusted in combination with real - time hydrological forecasts, early fish resource monitoring, and the operating conditions of hydropower stations. Note that the interval between the operation period and the previous spawning peak shall be more than 5 days, and there should be a natural rising water 2 days before.

[0168] The above specific embodiments are only explanations of the present invention and are not limitations thereof. After reading this specification, those skilled in the art can make modifications to these embodiments without creative contributions as needed, but as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A grouped ecological scheduling method that maximally meets the needs of different fish species, characterized in that: The method includes the following steps: S1. Obtain the existing fish species in the target river section through environmental DNA surveys. S2. Group according to the fish spawning time, type, and water temperature requirements in the study area, and determine the overall framework of reservoir ecological regulation. Among them, the spawning types are divided into adhesive-settling eggs and drifting eggs, and the fish of the same spawning type are divided into 2-3 groups according to the spawning water temperature. S3. Organize the monitoring data of fish spawning volume and the hydrological data of water temperature and flow, use the stepwise multiple regression model to analyze the correlation between the spawning scale and hydrological data, clarify the key hydrological elements and thresholds affecting fish spawning, and determine the ecological regulation timing for each group according to the thresholds. S4. Analyze the preferences of indigenous fish spawning habitat elements during each ecological regulation period, construct a two-dimensional hydrodynamic model, and use the improved habitat simulation method to determine the range of reservoir discharge flow that maximally stimulates fish spawning during each regulation period. S5. Couple the habitat simulation method with the analysis of natural hydrological regime, analyze the fluctuations of water level and flow under natural conditions during each regulation period, and determine the indicators of daily water level variation range and daily average flow variation range. S6. For each group, coordinate the constraints of the discharge flow and water level changes of fish laying adhesive-settling eggs and drifting eggs, define the key indicators of the discharge flow and daily flow variation range that can maximally cover the spawning needs of each group of fish, and form an ecological regulation plan that takes into account the different needs of fish at different times. The environmental DNA survey in step S1 is as follows: Collect at least 3 cross-sections in each river section, with at least 3 sampling points at each cross-section, and collect at least four samples at each point in different seasons; during the comprehensive species identification process, the finally determined species are collected at least at one-third of the points, and are collected at least twice at the same cross-section.

2. The grouped ecological scheduling method for maximizing the satisfaction of the needs of different fish species according to claim 1, characterized in that: In step S3, the hydrological parameters for stepwise multiple regression analysis include: water temperature, flow on the spawning day, flow on the day before spawning, flow on the two days before spawning, increase in flow on the spawning day, increase in flow on the day before spawning, increase in flow on the two days before spawning, increase in water level of spawning flow, increase in water level on the day before spawning, and increase in water level on the two days before spawning.

3. The grouped ecological operation method for maximizing the satisfaction of different fish requirements according to claim 1, characterized in that: Step S4 Specifically includes: To maximize the satisfaction of the habitat preferences of more fish within each group, the weighted average method is used to calculate the optimal values of habitat elements that stimulate the spawning of different indigenous fish; the weighted standard deviation is used to calculate the suitable intervals of each habitat element, and the t-test is used to verify the difference between the optimal value and the average value; the calculation formulas are formula 1 and formula 2 respectively: (Formula 1) (Formula 2) In the formula: represents the optimal value of the habitat element for water depth or flow velocity; i represents the fish species number; x i is the suitable value of the habitat element for species ; n i is the number of individuals of species in the environmental DNA survey; S SD is the weighted standard deviation of the habitat element, that is, the suitable interval of the habitat element.

4. The grouped ecological scheduling method for maximizing the satisfaction of different fish needs according to claim 1, characterized in that: In step S4, the improved habitat simulation method is used to determine the range of hydropower station discharge flow during the ecological regulation period of different types of fish. Taking the fish with adhesive-settling eggs as an example, the calculation formula is as follows: (Formula 3) (Formula 4) (Formula 5) (Formula 6) Wherein: WUA is the effective habitat area, with the unit of: m 2 ; Q is the discharge flow, with the unit of: m 3 / s; f [] is WUA the functional relationship varying with the flow rate; the flow rate corresponding to the maximum value of the effective habitat area; the lower limit value of the discharge flow suitable for the spawning of fish with sticky sediment eggs, the upper limit value of the discharge flow suitable for the spawning of fish with sticky sediment eggs, with the unit of: m 3 / s.

5. The grouped ecological scheduling method for maximizing the satisfaction of the needs of different fish species as described in claim 1, characterized in that: In step S5, during the ecological regulation for pelagic-egg fish, it is crucial to create a continuous rising water process to stimulate spawning and a gentle falling water process to support the drifting and hatching of fish eggs. The key index analysis of the rising-falling water process specifically includes: based on the daily measured data of spawning amount and flow rate, screening the pulsed flow processes that effectively stimulate spawning under the current situation; analyzing the rising water indexes of the pulsed flow processes, and defining the total water level rise standard that can stimulate spawning according to the 90% guarantee rate requirement and the continuous rising water time standard ; based on the above rising water process standards, analyzing the long-term sequence of natural daily flow data at the cross-section of the hydrological station adjacent to the spawning ground, and screening out all rising water processes that meet both and . According to the 75% guarantee rate requirement, finally determine the daily increase in the discharge from the reservoir during the ecological regulation and the duration of the rising water .

6. The grouped ecological scheduling method for maximizing the satisfaction of the needs of different fish species according to claim 1, characterized in that: In step S5, during the ecological regulation of adhesive and sinking egg fish, the daily variation ranges of the reservoir discharge flow and water level are mainly controlled to stimulate fish spawning and ensure that fish eggs are not exposed and die due to a sharp drop in water level. Among them, the daily variation range of the water level is determined according to the maximum water level difference within consecutive N days during the spawning period under natural flow field conditions, where N is the fish egg hatching time. The principle is that it is assumed that the water level fluctuations within consecutive N days with more than half of the days under natural conditions will not affect the development of adhesive and sinking eggs. Furthermore, the daily variation range of the hydropower station discharge flow is determined according to the water level-discharge relationship ; (Formula 7) (Formula 8) (Formula 9) Wherein: is the daily average water level on the x-th day, with the unit of: m; is the maximum water level difference in N consecutive days during the spawning period under natural conditions, with the unit of: m; j The value ranges from 1 to the maximum number of days in the spawning period, and the value of N is determined according to the hatching time of fish eggs; is the maximum water level variation within a day during the ecological regulation period for fish with adhesive and sinking eggs, with the unit of: m; is the maximum flow variation within a day during the ecological regulation period for fish with adhesive and sinking eggs, with the unit of m 3 / s; g[ ] is the water level - flow relationship curve of the control section.

7. The grouped ecological scheduling method for maximizing the satisfaction of different fish species' needs according to claim 1, characterized in that: step S6 Among them, the ecological operation plan that takes into account the differentiated needs of fish species specifically includes: the discharge flow rate is the union of the suitable flow rate ranges of different spawning types of fish, and a rising water process is created to stimulate the spawning of fish eggs with drifting eggs. However, the rising-falling water process takes into account the constraint of the maximum daily water level change to meet the spawning habitat of fish with adhesive and sinking eggs; the key control indicators of the operation plan include the initial discharge flow rate , the daily average flow rate increase , the duration of rising water , the daily average flow rate decrease , the duration of falling water , and the maximum daily water level change ; the calculation process of each indicator is as follows: Initial value of the discharge flow Not less than the lower limit value of the suitable flow for sticky and sinking eggs And the lower limit value of the suitable flow for drifting eggs ; Peak value of the discharge flow Determined by the initial value and the total flow increase; The formula is as follows: (Formula 10) (Formula 11) In the formula: is the starting value of the discharge flow for the ecological regulation that takes into account both adhesive-settling eggs and drifting eggs, with the unit of: m 3 / s; is the maximum value of the discharge flow, with the unit of: m 3 / s; is the lower limit of the suitable flow for the spawning of adhesive-settling egg fish, is the lower limit of the suitable flow for the spawning of drifting egg fish; During the rising flood process, the water level stability of adhesive and sinking-egg fish species is given priority, and the maximum daily variation of the discharge from the reservoir is required to be not exceeding . Then, the formula for the daily increase in the discharge from the reservoir that takes into account both adhesive and sinking eggs and drifting eggs is: (Formula 12) When the required rising amplitude of the water level for drifting eggs exceeds the water level variation range requirement for adhesive-settling eggs, in order to ensure both the total water level rise and the daily water level variation range, the duration of continuous rising water needs to be increased, and the duration of rising water is: (Formula 13) During the water recession process, the daily decline rate of the discharge from the reservoir is based on the water level stability control index for sticky-egg fish, that is , then the duration of the rising water is: (Formula 14).

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