A method for determining a habitat suitability curve tolerance range for a lake ecological water level

Abstract

The application discloses a kind of habitat suitability curve tolerance range determination methods for lake ecological water level, the method comprises the following steps: step 1, habitat suitability curve baseline construction;Step 2, lake hydrodynamic water quality model is established;Step 3, cumulative weighted available area calculation;Step 4, lake ecological water level calculation result acquisition;Step 5, habitat suitability curve variation scheme design;Step 6, habitat suitability curve tolerance range determination.The method disclosed in the application gives consideration to the simplicity of operation and ecological correlation, is especially suitable for limited data information but needs to quickly evaluate the management practice of habitat factor sensitivity, optimizes resource allocation;The method disclosed in the application quantifies the elastic space of lake ecological water level dynamic adjustment, provides scientific basis for lake habitat protection and restoration.

Description

Technical Field

[0001] This invention belongs to the field of lake ecological water level regulation technology, and in particular relates to a method for determining the tolerance range of habitat suitability curves for lake ecological water levels. Background Technology

[0002] Lakes are the most basic geographical units of the terrestrial surface system and important carriers of surface water resources. They provide ecological services such as water supply, aquaculture, water purification, and biodiversity maintenance, playing a vital role in ensuring global water ecological security. Determining lake ecological water levels is crucial for maintaining the structure and function of lake ecosystems, promoting the efficient development and utilization of watershed water resources, and serving as an important basis for lake management. Habitat simulation is one of the important methods for determining lake ecological water levels. This method uses target species as an important indicator of aquatic ecosystem health. Based on the physical habitat conditions required by the target species, it obtains the spatiotemporal distribution of habitat factors through field monitoring or model simulation, and combines this with habitat suitability evaluation indicators to simulate the quantitative relationship between lake water level and habitat suitability distribution, thereby obtaining a suitable ecological water level for protecting aquatic organisms. The weighted usable area (WUA) calculated based on the habitat suitability curve is the core indicator for habitat suitability evaluation.

[0003] Currently, habitat suitability curves are mostly constructed using trapezoidal curves. The upper and lower edges of the trapezoid correspond to suitability indices of 1 and 0, respectively. The positions and slopes of the left and right edges are determined based on the needs of the target species. The values ​​of the apex and trough represent the optimal range and tolerance threshold of habitat factors for the target species. The values ​​of habitat suitability curve parameters directly affect the weighted available area calculation results, and thus affect the determination of lake ecological water levels. Methods for constructing habitat suitability curves mainly include literature review, expert judgment, aquatic organism capture statistics, and indoor controlled experiments. Literature review and expert judgment are currently the most commonly used methods. These methods are simple and practical, but they have a certain degree of subjectivity, and the applicability of the constructed habitat suitability curve to natural conditions cannot be guaranteed. While the suitability curve parameters obtained through field surveys and indoor experiments are more accurate, they suffer from problems such as long cycles, high costs, and susceptibility to limitations in experimental site conditions and sample size. In reality, when the parameters of the habitat suitability curve fluctuate within a certain range, the impact on the calculated ecological water level of lakes is minimal. However, there is currently no method to determine the maximum acceptable fluctuation range (i.e., tolerance range) of the habitat suitability curve. Therefore, it is urgent to construct a method for determining the tolerance range of the habitat suitability curve for lake ecological water level, to identify the sensitivity of habitat factors to the calculated results of lake ecological water level, thereby reducing unnecessary survey costs, lowering resource consumption, quantifying the elasticity of dynamic adjustment of lake ecological water level, and providing a scientific basis for lake habitat protection and restoration. Summary of the Invention

[0004] The purpose of this invention is to provide a method for determining the tolerance range of habitat suitability curves for lake ecological water levels, so as to solve the above-mentioned technical problems.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention discloses a method for determining the tolerance range of a habitat suitability curve based on lake ecological water level, characterized in that the method includes the following steps:

[0007] Step 1: Construction of habitat suitability curve baseline: For lakes with ecological water levels to be determined, conduct surveys and select target species. Select habitat factors according to the key physiological developmental needs of the target species, determine the optimal range and tolerance threshold of each habitat factor for the target species, and construct the habitat suitability curve of each habitat factor in the form of a trapezoidal curve as the habitat suitability curve baseline.

[0008] Step 2: Establishment of lake hydrodynamic and water quality model: Obtain basic lake data, divide the computational grid, establish a lake hydrodynamic and water quality model based on three types of control equations: hydrodynamic, temperature and heat transfer, and water quality, set model boundary conditions and initial conditions, calibrate and verify the model parameters, and use the verified lake hydrodynamic and water quality model to simulate and obtain the habitat factor values ​​for each computational grid.

[0009] Step 3: Calculation of Cumulative Weighted Usable Area: Based on the habitat factor values ​​for each calculation grid, the suitability index of the habitat factors is obtained by referring to the baseline of the habitat suitability curve. The weighted usable area is used to evaluate the habitat quality of each layer. The calculation formula is as follows:

[0010] (9)

[0011] In the formula: The weighted sum of the usable area of ​​the grid cells at the m-th layer for the target species, in km². 2 ; Let be the area of ​​the i-th grid cell in the m-th layer, km. 2 ; Let be the habitat suitability index of the i-th grid cell in the m-th layer; For the first The habitat suitability index is a product of several habitat factors; F is the expression form of the habitat suitability index.

[0012] The weighted usable areas of each layer within the target species' habitat are summed to obtain the cumulative weighted usable area applicable to lakes, as shown in the following formula:

[0013] (10)

[0014] In the formula: CWUA is the cumulative weighted usable area for the target species, in km². 2 M represents the number of computational grid layers within the target species' habitat.

[0015] Step 4: Obtaining the calculation results of lake ecological water level: Set up a water level gradient scheme. For each water level gradient scheme, calculate the cumulative weighted usable area at that water level based on the habitat suitability curve baseline. Then, fit the scatter points composed of different water levels and the cumulative weighted usable area at that water level using a quadratic function to obtain the lake water level-cumulative weighted usable area response curve. The water level corresponding to the extreme point of the curve is the calculation result of the lake ecological water level. The calculation result of the lake ecological water level corresponding to the habitat suitability curve baseline is the target value of the lake ecological water level.

[0016] Step 5: Habitat Suitability Curve Variation Scheme Design: Based on the baseline of the habitat suitability curve, a variation scheme is designed by changing the left and right sides of the trapezoid of the habitat suitability curve. The basic unit is set according to the range of habitat factor tolerance threshold values. According to the designed variation scheme, the left and right sides of the trapezoid of the habitat suitability curve are changed sequentially using the basic unit to form a new habitat suitability curve as the habitat suitability curve adjustment line, until the changed sides can no longer form a trapezoid shape and the bottom vertical lines are all inside the trapezoid. All variation schemes are combined into a variation scheme set.

[0017] Step 6: Determining the Tolerance Range of the Habitat Suitability Curve: Based on the adjustment line of the habitat suitability curve generated under each change scheme, the calculation results of the lake ecological water level corresponding to each change scheme are calculated similarly. The calculation results of the lake ecological water level under each change scheme are statistically analyzed and compared with the target value of the lake ecological water level. When the error between the calculated value of the lake ecological water level and the target value of the lake ecological water level meets the error threshold requirement, it is considered that the calculated value of the lake ecological water level is not sensitive to the change of the suitability curve. All change schemes that are not sensitive to the change of the suitability curve are summarized, and the area enclosed by their extreme values ​​is the tolerance range of the habitat suitability curve. The sensitivity of each habitat factor is analyzed based on the relative size of the area of ​​the tolerance range of the habitat suitability curve.

[0018] Furthermore, the investigation and selection of target species for the lake whose ecological water level is to be determined in step 1 specifically involves: investigating the national-level aquatic germplasm resource protection areas and endemic fish species involved in the lake whose ecological water level is to be determined, and selecting endemic fish species whose average catch in the past 5 years has decreased by more than 30% compared with the original catch in the natural state of the lake as target species for lake habitat protection, based on the historical changes in catch.

[0019] The habitat factors include three physicochemical indicators: water temperature, flow rate, and dissolved oxygen.

[0020] Furthermore, the basic lake data in step 2 includes meteorological data, hydrological data, water quality data, and underwater topographic data. The meteorological data includes daily precipitation, evaporation, air pressure, temperature, relative humidity, cloud cover coefficient, wind speed, and wind direction data from meteorological stations in the lake's basin. The hydrological data includes daily measured water levels in the lake area, inflow river flow, outflow river flow, and intake flow data. The water quality data includes monthly surface and deep water quality data from sampling points in the lake area, inflow river water quality, and outflow river water quality data. The underwater topographic data uses data from the 1985 National Elevation Datum survey.

[0021] Furthermore, the specific steps in step 2 for dividing the computational grid are as follows: the computational grid is divided into planar rectangular grids. Considering simulation accuracy and computational efficiency, the total number of computational grids is determined. The computational grids can accurately reflect the changes in lake topography and lake shoreline. The bottom elevation of each layer of computational grid is discretized based on underwater topographic data interpolation.

[0022] Furthermore, the hydrodynamic governing equations in step 2 include the momentum equation and the continuity equation;

[0023] The momentum equation is:

[0024] (1)

[0025]

[0026]

[0027]

[0028] (2)

[0029]

[0030]

[0031]

[0032] (3)

[0033] The continuity equation is:

[0034] (4)

[0035] (5)

[0036] In the formula: The curve-orthogonal coordinates are in the horizontal direction; The vertical σ coordinate; for The horizontal velocity component in the direction, ; For the total water depth, ; This refers to the water surface elevation. ; Atmospheric pressure. ; Here are the coordinate transformation coefficients; the transformation coefficients in Cartesian coordinates are... ; for The depth-averaged velocity component in the direction, ; Reference density Additional hydrostatic pressure, ; The Coriolis force coefficient, ; The horizontal momentum diffusion coefficient is... ; The vertical turbulent viscosity coefficient, ; This is the vegetation resistance coefficient; This is the projected vegetation area; for Source and sink terms of direction These are the source and sink terms of the mass conservation equation. ;

[0037] The temperature and heat transfer control equations are:

[0038] (6)

[0039]

[0040] In the formula: and for Mass flux component in the direction. T represents temperature, in °C; I represents solar shortwave radiation intensity, in W / m². 2 A b The vertical turbulent diffusion coefficient is... S T For heat exchange source and sink terms, J / s;

[0041] Water quality control equations include mass conservation equations for water quality variables and dynamic equations for state variables;

[0042] The mass conservation equation for water quality variables is:

[0043] (7)

[0044]

[0045] In the formula: The concentration of water quality variables is expressed in mg / L. These are the horizontal and vertical coordinates, respectively. coordinates velocity components, ; They are respectively Turbulent diffusion coefficient in the direction, ; For internal / external source pools; The depth of the water column is in meters (m). This is the factor for the change in the coordinates of the horizontal curve;

[0046] The dynamic equations of the state variables are:

[0047] (8)

[0048] In the formula: The kinetic rate; Source and sink terms are caused by external loads and / or internal reactions.

[0049] Furthermore, the model boundary conditions in step 2 include hydrological boundary conditions and meteorological boundary conditions. The hydrological boundary conditions include the inflow of rivers into the lake, the outflow of rivers into the lake, the inflow of water intake, the water quality of rivers into the lake, and the water quality of rivers out of the lake. The meteorological boundary conditions include precipitation, evaporation, air pressure, air temperature, relative humidity, cloud cover coefficient, wind speed, and wind direction.

[0050] The initial conditions of the model are based on measured meteorological, hydrological, and water quality data at the beginning of the calculation period;

[0051] Model parameters include bottom roughness height, wind shielding coefficient, constant eddy viscosity, horizontal momentum diffusion coefficient, pure water extinction coefficient, surface absorbed solar radiation, initial riverbed temperature, and active bed temperature layer thickness.

[0052] The calibration and verification of the model parameters are specifically carried out as follows: the hydrodynamic and water quality model parameters are calibrated and verified using measured data from the lake surface and vertical layers. The measured values ​​and simulated values ​​of the simulated indicators are compared. Three types of error statistical indicators, namely mean absolute error (MAE), relative error (RE), and root mean square error (RMSE), are used to measure the magnitude of the error. When the error statistical indicators meet the accuracy threshold requirements, the model is considered to have passed the verification. The specific accuracy threshold requirements for the error statistical indicators are: MAE less than 30%~50% of the standard deviation of the measured data, RE less than 25%~35%, and RMSE less than 40%~60% of the standard deviation of the measured data.

[0053] Furthermore, the water level gradient scheme described in step 4 is specifically set up as follows: based on the historical water level fluctuations and the legal operating water level of the lake, a water level gradient scheme is set at intervals of 0.5m; the historical water level fluctuations of the lake are determined by taking the maximum and minimum values ​​of the historical water level measured data of the lake, and the legal operating water level is determined according to the comprehensive watershed planning, scheduling procedures or local lake protection regulations.

[0054] Furthermore, the modification scheme designed in step 5 includes the following three modification methods: 1) Modify the vertex of the fixed bottom endpoint of the edge line, including modifying the vertex of the fixed left edge line and modifying the vertex of the fixed right edge line; 2) Modify the bottom endpoint of the fixed vertex of the edge line, including modifying the bottom endpoint of the fixed left edge line and modifying the bottom endpoint of the fixed right edge line; 3) Translate the edge line, including translating the left edge line and translating the right edge line.

[0055] Furthermore, the requirement to meet the error threshold in step 6 specifically means that the error is within the range of -0.1 to 0.1m.

[0056] The beneficial effects of this invention are as follows: The method described herein balances ease of operation with ecological relevance, making it particularly suitable for management practices where data is limited but rapid assessment of habitat sensitivity is required. For low-sensitivity habitat factors, suggestions can be made to relax monitoring or management precision, reducing unnecessary survey costs and optimizing resource allocation. Based on the tolerance range of the habitat suitability curve determined using the method described herein, it is clear within which variations in the habitat suitability curve parameters have little impact on the lake's ecological water level calculation results, and beyond which ranges will significantly affect the calculation results. This allows for determining whether a resurvey of the habitat suitability curve is necessary, providing an important reference for the rationality analysis of lake ecological water level target values. The method described herein quantifies the elasticity space for dynamic adjustment of lake ecological water levels, providing a scientific basis for lake habitat protection and restoration.

[0057] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0058] Figure 1 This is a schematic diagram of the method flow described in this invention;

[0059] Figure 2 A schematic diagram of the baseline for the habitat suitability curve of Fuxian Lake;

[0060] Figure 3 A schematic diagram of the computational grid for the hydrodynamic and water quality model of Fuxian Lake;

[0061] Figure 4 A schematic diagram showing the calibration and verification results of the hydrodynamic and water quality model for Fuxian Lake.

[0062] Figure 5A schematic diagram showing the weighted usable area calculation results of each layer of the computational grid corresponding to each water level scheme below the baseline of the habitat suitability curve of Fuxian Lake;

[0063] Figure 6 A graph showing the response relationship between lake water level and cumulative weighted available area below the baseline of the habitat suitability curve of Fuxian Lake;

[0064] Figure 7 This is a graph showing the response relationship between the water level and the cumulative weighted available area of ​​Fuxian Lake under extreme scenarios of water temperature suitability curve variations.

[0065] Figure 8 A schematic diagram showing the tolerance range of the water temperature suitability curve corresponding to the target value of the ecological water level of Fuxian Lake;

[0066] Figure 9 The graph shows the response relationship between the water level and the cumulative weighted available area of ​​Fuxian Lake under the extreme scenario of the variation of the flow velocity suitability curve.

[0067] Figure 10 A schematic diagram showing the tolerance range of the flow velocity suitability curve corresponding to the target value of the ecological water level of Fuxian Lake;

[0068] Figure 11 This is a graph showing the response relationship between the water level and the cumulative weighted available area of ​​Fuxian Lake under extreme scenarios of dissolved oxygen suitability curve variations.

[0069] Figure 12 This is a schematic diagram showing the tolerance range of the dissolved oxygen suitability curve corresponding to the target value of the ecological water level of Fuxian Lake. Detailed Implementation

[0070] This invention discloses a method for determining the tolerance range of habitat suitability curves based on lake ecological water levels, such as... Figure 1 As shown, the method includes the following steps:

[0071] Step 1: Construction of Habitat Suitability Curve Baseline: Investigate the national-level aquatic germplasm resource protection areas and endemic fish species involved in the lakes whose ecological water levels are to be determined. Based on historical catch changes, select endemic fish species whose average catch over the past 5 years has decreased by more than 30% compared to the original catch under natural conditions in the lake as target species for lake habitat protection. Select habitat factors, including physicochemical indicators such as water temperature, flow velocity, and dissolved oxygen, according to the key physiological developmental needs of the target species. Use literature review and field surveys to determine the optimal range and tolerance threshold for each habitat factor for the target species. Construct a habitat suitability curve for each habitat factor using a trapezoidal curve format as the habitat suitability curve baseline.

[0072] Step 2: Establishment of the Lake Hydrodynamic and Water Quality Model: Acquire basic lake data, divide the computational grid based on measured underwater topographic data, and establish a three-dimensional lake hydrodynamic and water quality model based on the governing equations for hydrodynamics, temperature and heat transfer, and water quality. Set the model boundary conditions and initial conditions, and calibrate and verify the main parameters of the model based on measured data. When the error statistics meet the simulation accuracy threshold requirements, the model is considered to have passed verification, meaning it can accurately reflect the spatiotemporal distribution of habitat factors. Then, the verified lake hydrodynamic and water quality model is used to simulate and obtain the habitat factor values ​​for each computational grid.

[0073] The basic data for the lake includes meteorological data, hydrological data, water quality data, and underwater topographic data. Meteorological data includes daily precipitation, evaporation, air pressure, temperature, relative humidity, cloud cover coefficient, wind speed, and wind direction from meteorological stations in the lake's basin. Hydrological data includes daily measured water levels in the lake area, inflow river flow, outflow river flow, and intake flow. Water quality data includes monthly surface and deep water quality data from sampling points in the lake area, inflow river water quality, and outflow river water quality. Underwater topographic data uses data from the 1985 National Height Datum Survey.

[0074] The computational grid is divided as follows: a planar rectangular grid is used to divide the computational grid. Considering simulation accuracy and computational efficiency, the total number of computational grids is determined. The computational grid should accurately reflect the changes in lake topography and shoreline. The bottom elevation of each layer of computational grid is discretized based on underwater topographic data interpolation.

[0075] The hydrodynamic governing equations include the momentum equation and the continuity equation;

[0076] The momentum equation is:

[0077] (1)

[0078]

[0079]

[0080]

[0081] (2)

[0082]

[0083]

[0084]

[0085] (3)

[0086] The continuity equation is:

[0087] (4)

[0088] (5)

[0089] In the formula: The curve-orthogonal coordinates are in the horizontal direction; The vertical σ coordinate; for The horizontal velocity component in the direction, ; For the total water depth, ; This refers to the water surface elevation. ; Atmospheric pressure. ; Here are the coordinate transformation coefficients; the transformation coefficients in Cartesian coordinates are... ; for The depth-averaged velocity component in the direction, ; Reference density Additional hydrostatic pressure, ; The Coriolis force coefficient, ; The horizontal momentum diffusion coefficient is... ; The vertical turbulent viscosity coefficient, ; This is the vegetation resistance coefficient; This is the projected vegetation area; for Source and sink terms of direction These are the source and sink terms of the mass conservation equation. .

[0090] The temperature and heat transfer control equations are:

[0091] (6)

[0092]

[0093] In the formula: and for Mass flux component in the direction. T represents temperature, in °C; I represents solar shortwave radiation intensity, in W / m². 2 A b The vertical turbulent diffusion coefficient is... S T For heat exchange source and sink terms, J / s.

[0094] Water quality control equations include mass conservation equations for water quality variables and dynamic equations for state variables;

[0095] The mass conservation equation for water quality variables is:

[0096] (7)

[0097]

[0098] In the formula: The concentration of water quality variables is expressed in mg / L. These are the horizontal and vertical coordinates, respectively. coordinates velocity components, ; They are respectively Turbulent diffusion coefficient in the direction, ; For internal / external source pools; The depth of the water column is in meters (m). This is the factor for the change in the coordinates of the horizontal curve.

[0099] The dynamic equations (first-order form) of the state variables are as follows:

[0100] (8)

[0101] In the formula: The kinetic rate; Source and sink terms are caused by external loads and / or internal reactions.

[0102] The model boundary conditions include hydrological boundary conditions (including inflow of rivers into the lake, outflow of rivers into the lake, water intake flow, water quality of rivers into the lake, and water quality of rivers outflow) and meteorological boundary conditions (including precipitation, evaporation, air pressure, air temperature, relative humidity, cloud cover coefficient, wind speed, and wind direction).

[0103] The initial conditions of the model are based on measured meteorological, hydrological, and water quality data at the beginning of the calculation period;

[0104] The main parameters of the model include bottom roughness height, wind shielding coefficient, constant eddy viscosity, horizontal momentum diffusion coefficient, pure water extinction coefficient, surface absorption of solar radiation, initial riverbed temperature, and active bed temperature layer thickness.

[0105] The calibration and validation process refers to calibrating and validating the main parameters of the hydrodynamic and water quality model using measured surface and vertical data from the lake. The measured and simulated values ​​of the simulated indicators are compared, and error statistics such as mean absolute error (MAE), relative error (RE), and root mean square error (RMSE) are used to measure the magnitude of the error. Generally, for the main hydrodynamic and water quality indicators, the model is considered validated when MAE is less than 30%–50% of the standard deviation of the measured data, RE is less than 25%–35%, and RMSE is less than 40%–60% of the standard deviation of the measured data; that is, the model has a good ability to simulate the spatiotemporal distribution of habitat factors.

[0106] Step 3: Cumulative Weighted Usable Area Calculation: Based on the habitat factor values ​​for each calculation grid, the suitability index of the habitat factors is obtained by referring to the baseline of the habitat suitability curve. The weighted usable area (WUA) is used to evaluate the habitat quality of each layer. The calculation formula is as follows:

[0107] (9)

[0108] In the formula: The weighted sum of the usable area of ​​the grid cells at the m-th layer for the target species, in km². 2 ; Let be the area of ​​the i-th grid cell in the m-th layer, km. 2 ; Let be the habitat suitability index of the i-th grid cell in the m-th layer; For the first The habitat suitability index is a product of several habitat factors; F is the expression of the habitat suitability index.

[0109] The weighted usable areas of each layer within the target species' habitat are summed to obtain the Cumulative Weighted Useable Area (CWUA) applicable to lakes, as shown in the following formula:

[0110] (10)

[0111] In the formula: CWUA is the cumulative weighted usable area for the target species, in km². 2 M represents the number of computational grid layers within the target species' habitat.

[0112] Step 4: Obtaining the Calculation Results of Lake Ecological Water Level: Based on the historical water level fluctuations and the legally mandated operating water level, water level gradient schemes are set at 0.5m intervals. The historical water level fluctuations are determined by taking the maximum and minimum values ​​from the measured historical water level data, while the legally mandated operating water level is determined according to the comprehensive watershed planning, scheduling regulations, or local lake protection regulations. For each water level scheme, based on the habitat suitability curve baseline, the cumulative weighted usable area at that water level is calculated using the cumulative weighted usable area calculation method proposed in Step 3. The scatter plots composed of different water levels (x-axis) and the cumulative weighted usable area at that water level (y-axis) are fitted using a quadratic function to obtain the lake water level-cumulative weighted usable area response curve. The water level corresponding to the extreme point of the curve is the calculated result of the lake ecological water level. The calculated result of the lake ecological water level corresponding to the habitat suitability curve baseline is the target value of the lake ecological water level.

[0113] Step 5: Habitat Suitability Curve Variation Scheme Design: Based on the baseline of the habitat suitability curve, variation schemes are designed by changing the left and right sides of the trapezoidal habitat suitability curve. This includes three variation methods: ① Fixing the bottom endpoint of the sideline and changing the vertex, including fixing the bottom endpoint of the left sideline and changing the vertex; ② Fixing the vertex of the sideline and changing the bottom endpoint, including fixing the bottom endpoint of the left sideline and changing the bottom endpoint of the right sideline; ③ Shifting the sideline, including shifting the left sideline and shifting the right sideline. Basic units are set according to the range of habitat factor tolerance thresholds. Following the three variation methods above, the left and right sides of the trapezoidal habitat suitability curve are sequentially varied using these basic units to form a new habitat suitability curve as the adjustment line. This continues until the changed sidelines can no longer form a trapezoidal shape and all the vertical lines of the base are inside the trapezoid. All variation schemes constitute a variation scheme set.

[0114] Step 6: Determining the Tolerance Range of the Habitat Suitability Curve: Based on the adjusted line of the habitat suitability curve generated under each change scheme, the calculation results of the lake ecological water level corresponding to each change scheme are obtained by following the calculation process in Steps 3 and 4. The calculation results of the lake ecological water level under each change scheme are statistically analyzed and compared with the target value of the lake ecological water level. When the error between the calculated lake ecological water level and the target value meets the error threshold requirement, i.e., the error is within the range of -0.1 to 0.1 m, the calculated lake ecological water level is considered insensitive to the change in the suitability curve. All change schemes that are insensitive to the change in the suitability curve are summarized, and the area enclosed by their extreme values ​​is the tolerance range of the habitat suitability curve. Based on this, a schematic diagram of the tolerance range of the habitat suitability curve corresponding to the target value of the lake ecological water level is drawn.

[0115] Based on the relative size of the tolerance range area of ​​the habitat suitability curve, the sensitivity of habitat factors is analyzed. Habitat factors with relatively large tolerance ranges are identified as low-sensitivity habitat factors, while habitat factors with relatively small tolerance ranges are identified as high-sensitivity habitat factors.

[0116] Example 1

[0117] This embodiment is a specific application example of the above method.

[0118] Fuxian Lake in Yunnan Province was selected as the research object. Located in Yuxi City, Yunnan Province, in the center of the Dianzhong Basin, Fuxian Lake spans Chengjiang City, Jiangchuan District, and Huaning County, and belongs to the Xijiang River system of the Nanpan River basin. Fuxian Lake has a maximum depth of 158.9 m, an average depth of 95.2 m, and a total water storage capacity of approximately 20.62 billion cubic meters. 3 It accounts for 71.8% of the total water storage of the nine plateau lakes in Yunnan Province. It is the deep-water freshwater lake with the largest water storage in my country. It is an important strategic reserve of freshwater resources and an important carrier and lifeline for the sustainable socio-economic development of central Yunnan.

[0119] This embodiment discloses a method for determining the tolerance range of a habitat suitability curve for lake ecological water levels, including the following steps:

[0120] Step 1: Construction of the habitat suitability curve baseline: According to the survey, the Fuxian Lake Endemic Fish National Aquatic Germplasm Resources Reserve is located in Fuxian Lake. It was included in the third batch of national aquatic germplasm resources reserves in 2010. The main protected species is the whitefish, and other protected species include the Yunnan barbel, the Fuxian golden-line barbel, the freshwater shrimp, the grass carp, the crucian carp, the common carp, and the silver carp. The whitefish is not only an endemic and rare fish species of Fuxian Lake, but also a major economic fish species. According to the literature (Current Status and Changes of Fish Resources in Fuxian Lake, Yunnan [J]. Lake Science, 2006, 18(03): 305-311), the yield of whitefish has dropped from 300-400 tons in the 1980s to less than 1 ton in the early 21st century. It has been listed in the Red Book of China's Species Red List and classified as endangered. Therefore, the whitefish was selected as the target species for habitat protection in Fuxian Lake. The whitefish is an open-water fish. Adults feed and live in the upper and middle layers of open water areas of lakes, and are concentrated in water layers with a depth of 0-20m. Water temperature and dissolved oxygen are two key factors for the survival of fish. According to the habit survey of whitefish, whitefish have a significant tendency to follow currents. Their growth and reproduction require an environment with a certain flow rate. Therefore, water temperature, flow rate and dissolved oxygen were selected as three physicochemical indicators as habitat factors.

[0121] According to the reference (DB5304 / T 005-2019. Technical Specifications for Adult Aquaculture of Anti-Wave Fish [S]. Yuxi: Yuxi Municipal Market Supervision Administration, 2019), the optimal water temperature range for *Culter alburnus* is 18~24℃, and the tolerance threshold is 10~29℃; according to the reference (The Influence of Different Flow Velocities on the Swimming Behavior of *Culter alburnus* [J]. Journal of Ecology, 2013, 32(3): 655-660), the optimal flow velocity range for *Culter alburnus* is 0.1~0.25m / s, and the tolerance threshold is 0~0.55m / s; according to the reference (Analysis of the Biology of *Culter alburnus* and the Causes of Population Decline [J]. Freshwater Fisheries, 2003, (01): 26-27), the optimal dissolved oxygen range for *Culter alburnus* is 6~8mg / L, and the tolerance threshold is 5~10mg / L. Trapezoidal curves were used to construct baselines for the suitability curves of three habitat factors: water temperature, flow velocity, and dissolved oxygen. Figure 2 As shown.

[0122] Step 2: Establishment of the lake's hydrodynamic and water quality model: The basic data obtained for Fuxian Lake includes: meteorological data such as daily precipitation, evaporation, air pressure, temperature, relative humidity, cloud cover coefficient, wind speed, and wind direction from meteorological stations in the Fuxian Lake basin (Chengjiang Meteorological Station, Jiangchuan Meteorological Station, and Huaning Meteorological Station); and hydrological data such as daily measured water levels at the Haikou Hydrological Station in the Fuxian Lake area, and the inflow rivers (Shanchong River, Liangwang River, Fucheng River, Dongda River, Daicun River, Yidu River, Wuche River, and Jule River). Daily flow rates of rivers including Dahe, Dajiyuhe, Yudaihe, and Niumohe; daily flow rates of water intakes (generalized into 7 intakes based on townships); water quality data including monthly water quality monitoring data of lake area water quality stations (Haikou, Gushan Lake Center) and rivers flowing into the lake (Shanchonghe, Liangwanghe, Fuchenghe, Dongdahe, Daicunhe, Yiduhe, Wuchehe, Julehe, Dajiyuhe, Yudaihe, and Niumohe); underwater topographic data using data from the 1985 National Elevation Datum Survey.

[0123] Based on the 2004 1:2000 measured underwater topographic data of Fuxian Lake (1985 National Elevation Datum), considering simulation accuracy and computational efficiency, a rectangular grid of 300m × 300m was adopted in the planar plane, generating a total of 2368 grids. This grid accurately reflects the topography and shoreline changes of Fuxian Lake. Vertically, the SGZ coordinate system was used, divided into 21 layers with interlayer intervals ranging from 1 to 20m. Specifically, the interlayer intervals were 1m for layers 1-5 below the water surface, 2.5m for layers 6-7, 5m for layers 8-13, 10m for layers 14-16, 15m for layers 17-18, and 20m for layers 19-21. The bottom elevation of each layer was discretized based on interpolation using the measured topographic data. The computational grid for the Fuxian Lake hydrodynamic and water quality model is shown below. Figure 3 As shown.

[0124] The main parameters of the hydrodynamic and water quality model were calibrated and validated using measured data of Fuxian Lake from January 1, 2020 to December 31, 2020. The values ​​of the main parameters of the Fuxian Lake hydrodynamic and water quality model are shown in Table 1. The calibration and validation results of the Fuxian Lake hydrodynamic and water quality model are as follows: Figure 4 As shown, the simulated water level results agree well with the measured water level process, with a mean absolute error (MAE) of 0.013 m, a relative error (RE) of 0.1%, and a root mean square error (RMSE) of 0.018 m. The simulated water temperature results also agree well with the measured water temperature process, with an MAE of 1.242℃, a RE of 6.732%, and an RMSE of 1.477℃. The simulated dissolved oxygen results have an MAE of 0.96 mg / L, a RE of 11.61%, and an RMSE of 1.37 mg / L. The MAE is less than 30%–50% of the standard deviation of the measured data, the RE is less than 25%–35%, and the RMSE is less than 40%–60% of the standard deviation of the measured data. The error statistics meet the simulation accuracy requirements, indicating that the established Fuxian Lake hydrodynamic and water quality model has good simulation capabilities for the spatiotemporal distribution of habitat factors. The established Fuxian Lake hydrodynamic and water quality model was used to simulate the habitat factor values ​​for each computational grid.

[0125] Table 1. Values ​​of main parameters in the hydrodynamic and water quality model of Fuxian Lake.

[0126] Parameter name Value unit Bottom roughness height 0.01 m Wind shielding coefficient 1.0 Dimensionless constant eddy viscosity 3.0 <![CDATA[m 2 s -1 ]]> Horizontal momentum diffusion coefficient 0.1 Dimensionless Extinction coefficient of pure water 0.45 <![CDATA[m -1 ]]> Surface absorbs solar radiation 1 Dimensionless Initial riverbed temperature 14.6 ℃ active bed temperature layer thickness 40 m Reoxygenation rate constant 5.32 Dimensionless Reoxygenation rate temperature regulation constant 1.03 Dimensionless

[0127] Step 3: Calculation of Cumulative Weighted Usable Area: Based on the habitat factor values ​​for each calculation grid, the suitability index of the habitat factors is obtained by referring to the baseline of the habitat suitability curve. The weighted usable area is used to evaluate the habitat quality of each layer. The calculation formula is as follows:

[0128] (9)

[0129] In the formula: The weighted sum of the usable area of ​​the grid cells at the m-th layer for the target species, in km². 2 ; Let be the area of ​​the i-th grid cell in the m-th layer, km. 2 ; Let be the habitat suitability index of the i-th grid cell in the m-th layer; For the first The habitat suitability index is a product of several habitat factors; F is the expression of the habitat suitability index.

[0130] The weighted usable areas of each layer within the target species' habitat are summed to obtain the cumulative weighted usable area applicable to lakes, as shown in the following formula:

[0131] (10)

[0132] In the formula: CWUA is the cumulative weighted usable area for the target species, in km². 2 M represents the number of computational grid layers within the target species' habitat.

[0133] Step 4: Obtaining the calculation results of the lake's ecological water level: Based on the long-term measured water level data of Fuxian Lake from 1953 to 2020, the historical water level range of Fuxian Lake is 1720.78m~1723.05m. According to the "Regulations on the Protection of Fuxian Lake in Yunnan Province", the legal operating water level of Fuxian Lake is 1721.65m~1723.35m. After combining the two, the water level range is 1720.78m~1723.35m. Considering that the characteristic water level may rise further after the implementation of water replenishment projects in Fuxian Lake in the future, a water level gradient scheme is set with an interval of 0.5m: 1721.0m, 1721.5m, 1722.0m, 1722.5m, 1723.0m, 1723.5m, 1724.0m. For each water level scheme, based on the habitat suitability curve baseline, the cumulative weighted usable area at that water level is calculated using the cumulative weighted usable area calculation method. The calculated results of the weighted usable area for each layer of the computational grid corresponding to each water level scheme below the Fuxian Lake habitat suitability curve baseline are as follows: Figure 5 As shown, the scatter plots consisting of different water levels (x-axis) and the cumulative weighted usable area at those water levels (y-axis) are fitted using a quadratic function to obtain the Fuxian Lake habitat suitability curve baseline, representing the response curve of Fuxian Lake water level versus cumulative weighted usable area. Figure 6 As shown, the relationship between the water level of Fuxian Lake and the cumulative weighted usable area is expressed by the formula y = -4.4226x. 2 +15234x-10 7 The maximum cumulative weighted usable area corresponding to the extreme point of the curve is 452.98 km². 2 The corresponding water level is 1722.29m, which is the target value for the ecological water level of Fuxian Lake.

[0134] Step 5: Design of Habitat Suitability Curve Variation Scheme: The water temperature tolerance threshold for Fuxian Lake whitefish is 10~29℃, and the optimal range is 18~24℃. The basic unit is set to 1℃, and the water temperature suitability curve is varied in the following three ways:

[0135] 1) Fixed bottom endpoint and variable vertex: First, fix the variable vertex of the bottom endpoint of the left sideline, setting the value of the bottom endpoint of the left sideline to 10°C. Then, using 18°C ​​as the base and 1°C as the basic unit, move the vertex to the left sequentially until a trapezoidal shape can no longer be formed and the vertical lines of the base are all inside the trapezoid. That is, the vertex values ​​are 17°C, 16°C, 15°C, 14°C, 13°C, 12°C, 11°C, and 10°C respectively. Next, move the vertex to the right until a trapezoidal shape can no longer be formed and the vertical lines of the base are all inside the trapezoid. That is, the vertex values ​​are 19°C, 20°C, 21°C, 22°C, and 23°C respectively, forming a total of 13 sets of fixed left sideline values. The first step involves changing the vertex of the fixed right-side edge line. The second step involves fixing the right-side edge line's bottom endpoint and changing the vertex. The vertex is then moved to the left in increments of 1°C, starting at 24°C, until a trapezoidal shape can no longer be formed and all the vertical lines of the base are inside the trapezoid. The vertex values ​​are 23°C, 22°C, 21°C, 20°C, and 19°C. This is repeated until a trapezoidal shape can no longer be formed and all the vertical lines of the base are inside the trapezoid. The vertex values ​​are 25°C, 26°C, 27°C, 28°C, and 29°C. This results in 10 sets of fixed right-side edge line bottom endpoint and vertex changing schemes. Therefore, there are a total of 23 fixed edge line bottom endpoint and vertex changing schemes.

[0136] 2) Fixed vertex and variable bottom endpoint: First, fix the vertex of the left sideline and vary the bottom endpoint. Set the vertex value of the left sideline to 18°C. Move the bottom endpoint sequentially to the left, using 1°C as the base and 1°C as the basic unit, until a trapezoidal shape can no longer be formed and the vertical lines of the base are all inside the trapezoid. That is, the bottom endpoint values ​​are 9°C, 8°C, 7°C, 6°C, 5°C, 4°C, 3°C, 2°C, 1°C, and 0°C. Then move it to the right until a trapezoidal shape can no longer be formed and the vertical lines of the base are all inside the trapezoid. That is, the bottom endpoint values ​​are 11°C, 12°C, 13°C, 14°C, 15°C, 16°C, 17°C, and 18°C, forming a total of 18 fixed... First, determine the left sideline's vertex and bottom endpoint variation scheme. Second, fix the right sideline's vertex and bottom endpoint variation scheme, setting the right sideline vertex value to 24°C. The bottom endpoint is then moved to the left in increments of 1°C, starting at 29°C, until a trapezoidal shape can no longer be formed and all vertical lines of the base are inside the trapezoid. The vertex values ​​are 28°C, 27°C, 26°C, 25°C, and 24°C. This is then moved to the right until a trapezoidal shape can no longer be formed and all vertical lines of the base are inside the trapezoid. The bottom endpoint values ​​are 30°C, 31°C, 32°C, 33°C, 34°C, and 35°C. This results in 11 sets of fixed right sideline vertex and bottom endpoint variation schemes. Therefore, there are a total of 29 fixed sideline vertex and bottom endpoint variation schemes.

[0137] 3) Translation of the sideline: First, translate the left sideline. Using the vertex (18°C) and base (10°C) of the left sideline as a reference, maintain the same slope and move leftward in 1°C increments until a trapezoidal shape can no longer be formed and the vertical lines of the base are all inside the trapezoid. That is, the vertex-base value combinations are 17°C-9°C, 16°C-8°C, 15°C-7°C, 14°C-6°C, 13°C-5°C, 12°C-4°C, 11°C-3°C, 10°C-2°C, 9°C-1°C, and 8°C-0°C. Then move rightward until a trapezoidal shape can no longer be formed and the vertical lines of the base are all inside the trapezoid. That is, the vertex-base value combinations are 19°C-11°C, 20°C-12°C, 21°C-13°C, 22°C-14°C, and 23°C-15°C. The total value forms... Fifteen translation schemes were developed for the left sideline. Next, the right sideline was translated, using the right sideline's vertex (24°C) and bottom point (29°C) as a baseline, maintaining the same slope and moving sequentially to the left in 1°C increments until a trapezoidal shape could no longer be formed and the bottom perpendicular line remained inside the trapezoid. The vertex-bottom point combinations were 23°C-28°C, 22°C-27°C, 21°C-26°C, 20°C-25°C, and 19°C-24°C. This was followed by further movement to the right until a trapezoidal shape could no longer be formed and the bottom perpendicular line remained inside the trapezoid. The vertex-bottom point combinations were 25°C-30°C, 26°C-31°C, 27°C-32°C, 28°C-33°C, 29°C-34°C, and 30°C-35°C. This resulted in 11 translation schemes for the left sideline. Therefore, a total of 26 translation schemes were developed for the sideline.

[0138] The current velocity tolerance threshold for the Fuxian Lake whitefish is 0~0.55 m / s, with an optimal range of 0.1~0.25 m / s. Using a basic unit of 0.02 m / s, the current velocity suitability curve was varied in the following three ways:

[0139] 1) Fixed bottom endpoint and variable vertex: First, fix the variable vertex of the left sideline bottom endpoint, setting the value of the left sideline bottom endpoint to 0 m / s. Move the vertex sequentially to the left, using 0.1 m / s as the base and 0.02 m / s as the basic unit, until a trapezoidal shape can no longer be formed and the vertical lines of the base are all inside the trapezoid. That is, the vertex values ​​are 0.08 m / s, 0.06 m / s, 0.04 m / s, 0.02 m / s, and 0 m / s. Then move it to the right until a trapezoidal shape can no longer be formed and the vertical lines of the base are all inside the trapezoid. That is, the vertex values ​​are 0.12 m / s, 0.14 m / s, 0.16 m / s, 0.18 m / s, 0.20 m / s, 0.22 m / s, and 0.24 m / s, resulting in 12 sets of fixed left sideline bottom endpoint variable vertex variations. Second, fix the variable vertex of the right sideline bottom endpoint... The value is fixed at 0.55 m / s. The vertex moves sequentially to the left, using 0.25 m / s as the baseline and 0.02 m / s as the basic unit, until a trapezoidal shape can no longer be formed and the perpendicular lines of the base are all inside the trapezoid. That is, the vertex values ​​are successively 0.27 m / s, 0.29 m / s, 0.31 m / s, 0.33 m / s, 0.35 m / s, 0.37 m / s, 0.39 m / s, 0.41 m / s, 0.43 m / s, 0.45 m / s, 0.47 m / s, 0.49 m / s, 0.51 m / s, 0.53 m / s, and 0.55 m / s. Then it moves to the right until a trapezoidal shape can no longer be formed and the perpendicular lines of the base are all inside the trapezoid. That is, the vertex values ​​are successively 0.23 m / s. The following values ​​are given: 0.21 m / s, 0.19 m / s, 0.17 m / s, 0.15 m / s, 0.13 m / s, and 0.11 m / s, resulting in 22 sets of fixed right sideline bottom endpoint variation vertex variation schemes. Therefore, there are a total of 34 fixed sideline bottom endpoint variation vertex variation schemes.

[0140] 2) Fixed Vertex and Variable Bottom Endpoint: First, fix the left side vertex and change the bottom endpoint. Set the left side vertex value to 0.1 m / s. Using 0 m / s as the base and 0.02 m / s as the basic unit, move the bottom endpoint sequentially to the left until a trapezoidal shape can no longer be formed and all the vertical lines of the base are inside the trapezoid. Since the bottom endpoint base is 0 m / s, it cannot move to the left and therefore has no corresponding value. Then move it to the right until a trapezoidal shape can no longer be formed and all the vertical lines of the base are inside the trapezoid. That is, the bottom endpoint values ​​are successively 0.02 m / s, 0.04 m / s, 0.06 m / s, 0.08 m / s, and 0.1 m / s, forming a total of 5 sets of fixed left side vertex and variable bottom endpoint changes. Second, fix the right side vertex and change the bottom endpoint. Set the right side vertex value to 0.25 m / s. The bottom endpoint is moved to the left in increments of 0.02 m / s, based on a base of 0.55 m / s, until a trapezoidal shape can no longer be formed and all the vertical lines of the base are inside the trapezoid. That is, the vertex values ​​are 0.53 m / s, 0.51 m / s, 0.49 m / s, 0.47 m / s, 0.45 m / s, 0.43 m / s, 0.41 m / s, 0.39 m / s, 0.37 m / s, 0.35 m / s, 0.33 m / s, 0.31 m / s, 0.29 m / s, 0.27 m / s, and 0.25 m / s. Then it is moved to the right until a trapezoidal shape can no longer be formed and all the vertical lines of the base are inside the trapezoid. That is, the bottom endpoint values ​​are 0.57 m / s and 0.59 m / s. A total of 17 sets of fixed right side edge bottom endpoint and vertex change schemes are formed. Therefore, there are a total of 22 schemes for changing the bottom endpoint of the fixed edge line.

[0141] 3) Translation of the sideline: First, translate the left sideline, using the vertex (0.1 m / s) and bottom endpoint (0 m / s) as a reference, maintaining the same slope and moving to the left in units of 0.02 m / s until a trapezoidal shape can no longer be formed and the vertical lines of the bottom edge are all inside the trapezoid. Since the bottom endpoint reference is 0 m / s, it cannot move to the left and therefore has no corresponding value. Then move to the right until a trapezoidal shape can no longer be formed and the vertical lines of the bottom edge are all inside the trapezoid. That is, the vertex-bottom endpoint value combinations are 0.12 m / s-0.02 m / s, 0.14 m / s-0.04 m / s, 0.16 m / s-0.06 m / s, 0.18 m / s-0.08 m / s, 0.20 m / s-0.10 m / s, and 0.22 m / s-0.12 m / s respectively. The following are seven possible translation schemes for the left side line, using speeds of 0.24 m / s and 0.14 m / s: Next, the right side line is translated, using the right side line's vertex (0.25 m / s) and bottom endpoint (0.55 m / s) as a baseline, maintaining the same slope and moving sequentially to the left in units of 0.02 m / s until a trapezoidal shape can no longer be formed and the vertical lines of the bottom edge are all inside the trapezoid. That is, the vertex-bottom endpoint combinations are 0.23 m / s-0.53 m / s, 0.21 m / s-0.51 m / s, and so on. The following speeds are used: 0.19m / s-0.49m / s, 0.17m / s-0.47m / s, 0.15m / s-0.45m / s, 0.13m / s-0.43m / s, and 0.11m / s-0.41m / s. The speeds are then moved to the right until a trapezoidal shape can no longer be formed and the vertical lines of the base are all inside the trapezoid. This results in 9 possible combinations of vertex-base point values: 0.27m / s-0.57m / s and 0.29m / s-0.59m / s. Therefore, there are a total of 16 possible translation schemes for the left side line.

[0142] The dissolved oxygen tolerance threshold for Fuxian Lake whitefish is 5-10 mg / L, with an optimal range of 6-8 mg / L. Using a base unit of 0.5 mg / L, the dissolved oxygen suitability curve was adjusted in the following three ways:

[0143] 1) Fixed bottom endpoint with variable vertex: First, fix the variable vertex of the left sideline bottom endpoint, setting the value of the left sideline bottom endpoint to 5 mg / L. Then, using 6 mg / L as the base and 0.5 mg / L as the basic unit, move the vertex to the left sequentially until a trapezoidal shape can no longer be formed and the vertical lines of the base are all inside the trapezoid. That is, the vertex values ​​are successively 5.5 mg / L and 5 mg / L. Next, move it to the right until a trapezoidal shape can no longer be formed and the vertical lines of the base are all inside the trapezoid. That is, the vertex values ​​are successively 6.5 mg / L, 7 mg / L, and 7.5 mg / L. This results in a total of 5 sets of fixed left sideline bottom endpoint variable vertex variation schemes. Next, the bottom endpoint of the right sideline is fixed at 10 mg / L. The endpoint is then moved to the left in increments of 0.5 mg / L, starting from 8 mg / L, until a trapezoidal shape can no longer be formed and the vertical lines of the base are all inside the trapezoid. This results in endpoint values ​​of 7.5 mg / L, 7 mg / L, and 6.5 mg / L. The position is then moved to the right until a trapezoidal shape can no longer be formed and the vertical lines of the base are all inside the trapezoid. This results in endpoint values ​​of 8.5 mg / L, 9 mg / L, 9.5 mg / L, and 10 mg / L. This creates a total of 7 sets of fixed bottom endpoint endpoint variation schemes. Therefore, there are a total of 12 fixed bottom endpoint endpoint variation schemes.

[0144] 2) Fixed vertex, variable base: First, fix the vertex of the left side line and change the base. Set the vertex value of the left side line to 6 mg / L. Move the base value to the left in increments of 0.5 mg / L, starting at 5 mg / L, until a trapezoidal shape can no longer be formed and the vertical lines of the base are all inside the trapezoid. That is, the vertex values ​​are 4.5 mg / L, 4 mg / L, 3.5 mg / L, 3 mg / L, 2.5 mg / L, 2 mg / L, 1.5 mg / L, 1 mg / L, 0.5 mg / L, and 0 mg / L. Then move the base value to the right until a trapezoidal shape can no longer be formed and the vertical lines of the base are all inside the trapezoid. That is, the base value is 5.5 mg / L and 6 mg / L, resulting in a total of 12... First, the left sideline vertex is fixed while the bottom endpoint is varied. Second, the right sideline vertex is fixed while the bottom endpoint is varied. The right sideline vertex value is fixed at 8 mg / L, and the bottom endpoint is moved to the left in increments of 0.5 mg / L, starting at 10 mg / L, until a trapezoidal shape can no longer be formed and the vertical line of the base is inside the trapezoid. That is, the vertex values ​​are 9.5 mg / L, 9 mg / L, 8.5 mg / L, and 8 mg / L. Then, it is moved to the right until a trapezoidal shape can no longer be formed and the vertical line of the base is inside the trapezoid. That is, the bottom endpoint values ​​are 10.5 mg / L, 11 mg / L, 11.5 mg / L, and 12 mg / L. This results in 8 sets of fixed right sideline vertex and vertex variation schemes. Therefore, there are a total of 20 fixed sideline vertex and bottom endpoint variation schemes.

[0145] 3) Translation of the sideline: First, translate the left sideline, using the vertex (6mg / L) and base (5mg / L) as a reference, maintaining the same slope and moving to the left in units of 0.5mg / L until a trapezoidal shape can no longer be formed and the perpendicular lines to the base are all inside the trapezoid. That is, the vertex-base value combinations are successively 5.5mg / L-4.5mg / L, 5mg / L-4mg / L, 4.5mg / L-3.5mg / L, 4mg / L-5mg / L-6mg / L, 4 ... L-3mg / L, 3.5mg / L-2.5mg / L, 3mg / L-2mg / L, 2.5mg / L-1.5mg / L, 2mg / L-1mg / L, 1.5mg / L-0.5mg / L, 1mg / L-0mg / L, and so on, moving to the right until a trapezoidal shape cannot be formed and all the perpendicular lines to the base are inside the trapezoid. That is, the combinations of vertex-base point values ​​are 6.5mg / L-5.5mg / L, 7mg / L, and so on. The following 13 schemes were created to shift the left sideline using concentrations of 8 mg / L (vertex) and 10 mg / L (base), maintaining the same slope and shifting in 0.5 mg / L increments until a trapezoidal shape could no longer be formed and the vertical lines of the base were all inside the trapezoid. The vertex-base point combinations were 7.5 mg / L - 9.5 mg / L. The concentrations are calculated as follows: mg / L, 7mg / L-9mg / L, 6.5mg / L-8.5mg / L. The concentrations are then moved to the right until a trapezoidal shape cannot be formed and the vertical lines of the base are all inside the trapezoid. This results in 7 possible combinations of vertex-base point values: 8.5mg / L-10.5mg / L, 9mg / L-11mg / L, 9.5mg / L-11.5mg / L, and 10mg / L-12mg / L. Therefore, there are a total of 20 possible translation schemes for the left sideline.

[0146] Step 6: Determining the Tolerance Range of Habitat Suitability Curve: Based on the aforementioned designed habitat suitability curve variation schemes for the Fuxian Lake whitefish, adjustment lines for the habitat suitability curves under each variation scheme are obtained. The response curve of Fuxian Lake water level-cumulative weighted available area under each variation scheme is constructed, yielding the calculated ecological water level of Fuxian Lake for each variation scheme. Compared with the target value of 1722.29m for the ecological water level of Fuxian Lake, when the error range between the calculated ecological water level and the target value is within ±0.1m, the calculated ecological water level is considered insensitive to this variation of the suitability curve. The response curve of Fuxian Lake water level-cumulative weighted available area under the extreme value of the water temperature suitability curve variation is shown below. Figure 7As shown, a summary of all variation schemes for the water temperature suitability curve that are insensitive to changes is presented. The area enclosed by the extreme values ​​of these variations represents the tolerance range of the water temperature suitability curve. Based on this, a schematic diagram of the tolerance range of the water temperature suitability curve under the target ecological water level of Fuxian Lake (1722.29m) is drawn, as shown below. Figure 8 As shown. Figure 7 , Figure 8 In diagrams ① and ②, the extreme values ​​of change are shown under the scheme of changing the bottom endpoint and changing the top endpoint with a fixed edge line; ③ and ④, the extreme values ​​of change are shown under the scheme of changing the bottom endpoint and changing the top endpoint with a fixed edge line; and ⑤ and ⑥, the extreme values ​​of change are shown under the scheme of changing the translated edge line. The response curve of Fuxian Lake water level-cumulative weighted usable area under the extreme values ​​of flow velocity suitability is shown below. Figure 9 As shown, a summary of all variation schemes for the flow velocity suitability curve that are insensitive to changes is presented. The area enclosed by the extreme values ​​of these variations represents the tolerance range of the flow velocity suitability curve. Based on this, a schematic diagram of the tolerance range of the flow velocity suitability curve under the target ecological water level of Fuxian Lake (1722.29m) is drawn, as shown below. Figure 10 As shown. Figure 9 , Figure 10 In diagrams ① and ②, the extreme values ​​of variation are shown under the scheme of changing the bottom endpoint and changing the top endpoint with a fixed edge; ③, the extreme value of variation is shown under the scheme of changing the top endpoint and changing the bottom endpoint with a fixed edge; and ④, the extreme value of variation is shown under the scheme of changing the edge by translation. The response curve of Fuxian Lake water level-cumulative weighted usable area under the extreme values ​​of dissolved oxygen suitability curve variation is shown below. Figure 11 As shown, a summary of all variation schemes for the water temperature suitability curve that are insensitive to changes is presented. The area enclosed by the extreme values ​​of these variations represents the tolerance range of the water temperature suitability curve. Based on this, a schematic diagram of the tolerance range of the dissolved oxygen suitability curve under the target ecological water level (1722.29m) of Fuxian Lake is drawn, as shown below. Figure 12 As shown. Figure 11 , Figure 12 In the diagram, ① and ③ represent the extreme values ​​of variation under the scheme of changing the bottom endpoint and changing the vertex of the fixed edge line, while ② and ④ represent the extreme values ​​of variation under the scheme of changing the bottom endpoint and changing the vertex of the fixed edge line.

[0147] from Figure 8 , 10 As can be seen from Figure 12, the area of ​​the dissolved oxygen suitability curve tolerance range (i.e., the gray shaded area in the figure) is significantly larger than that of the water temperature suitability curve and the flow velocity suitability curve tolerance range. Therefore, for the target value of the ecological water level of Fuxian Lake, water temperature and flow velocity are low-sensitivity habitat factors, while dissolved oxygen is a high-sensitivity habitat factor. Based on this, the following suggestions are made for the management of the ecological water level of Fuxian Lake: the survey accuracy of the water temperature and flow velocity suitability curves can be relaxed, while the survey accuracy of the dissolved oxygen suitability curve should be improved, and the parameter values ​​of the dissolved oxygen suitability curve should be revised in a timely manner and the target value of the ecological water level of Fuxian Lake should be recalculated.

[0148] Finally, it should be noted that the above description is only used to illustrate the technical solution of the present invention and not to limit it. Although the present invention has been described in detail with reference to the preferred arrangement, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for determining the tolerance range of habitat suitability curves for lake ecological water levels, characterized in that, The method includes the following steps: Step 1: Construction of habitat suitability curve baseline: For lakes with ecological water levels to be determined, conduct surveys and select target species. Select habitat factors according to the key physiological developmental needs of the target species, determine the optimal range and tolerance threshold of each habitat factor for the target species, and construct the habitat suitability curve of each habitat factor in the form of a trapezoidal curve as the habitat suitability curve baseline. Step 2: Establishment of lake hydrodynamic and water quality model: Obtain basic lake data, divide the computational grid, establish a lake hydrodynamic and water quality model based on three types of control equations: hydrodynamic, temperature and heat transfer, and water quality, set model boundary conditions and initial conditions, calibrate and verify the model parameters, and use the verified lake hydrodynamic and water quality model to simulate and obtain the habitat factor values ​​for each computational grid. Step 3: Calculation of Cumulative Weighted Usable Area: Based on the habitat factor values ​​for each calculation grid, the suitability index of the habitat factors is obtained by referring to the baseline of the habitat suitability curve. The weighted usable area is used to evaluate the habitat quality of each layer. The calculation formula is as follows: In the formula: The weighted sum of the usable area of ​​the m-th grid cells for the target species is expressed in km². 2 ; This represents the area of ​​the i-th grid cell in the m-th layer, in km². 2 ; Let be the habitat suitability index of the i-th grid cell in the m-th layer; For the first The habitat suitability index is a product of several habitat factors; F is the expression form of the habitat suitability index. The weighted usable areas of each layer within the target species' habitat are summed to obtain the cumulative weighted usable area applicable to lakes, as shown in the following formula: In the formula: CWUA is the cumulative weighted usable area of ​​the target species, in km². 2 M represents the number of computational grid layers within the target species' habitat. Step 4: Obtaining the calculation results of lake ecological water level: Set up a water level gradient scheme. For each water level gradient scheme, calculate the cumulative weighted usable area at that water level based on the habitat suitability curve baseline. Then, fit the scatter points composed of different water levels and the cumulative weighted usable area at that water level using a quadratic function to obtain the lake water level-cumulative weighted usable area response curve. The water level corresponding to the extreme point of the curve is the calculation result of the lake ecological water level. The calculation result of the lake ecological water level corresponding to the habitat suitability curve baseline is the target value of the lake ecological water level. Step 5: Habitat Suitability Curve Variation Scheme Design: Based on the baseline of the habitat suitability curve, a variation scheme is designed by changing the left and right sides of the trapezoid of the habitat suitability curve. The basic unit is set according to the range of habitat factor tolerance threshold values. According to the designed variation scheme, the left and right sides of the trapezoid of the habitat suitability curve are changed sequentially using the basic unit to form a new habitat suitability curve as the habitat suitability curve adjustment line, until the changed sides can no longer form a trapezoid shape and the bottom vertical lines are all inside the trapezoid. All variation schemes are combined into a variation scheme set. Step 6: Determining the Tolerance Range of the Habitat Suitability Curve: Based on the adjustment line of the habitat suitability curve generated under each change scheme, the calculation results of the lake ecological water level corresponding to each change scheme are calculated similarly. The calculation results of the lake ecological water level under each change scheme are statistically analyzed and compared with the target value of the lake ecological water level. When the error between the calculated value of the lake ecological water level and the target value of the lake ecological water level meets the error threshold requirement, it is considered that the calculated value of the lake ecological water level is not sensitive to the change of the suitability curve. All change schemes that are not sensitive to the change of the suitability curve are summarized, and the area enclosed by their extreme values ​​is the tolerance range of the habitat suitability curve. The sensitivity of each habitat factor is analyzed based on the relative size of the area of ​​the tolerance range of the habitat suitability curve.

2. The method for determining the tolerance range of a habitat suitability curve based on lake ecological water level according to claim 1, characterized in that, The specific steps for investigating and selecting target species for lakes with undetermined ecological water levels in step 1 are as follows: investigate the national-level aquatic germplasm resource protection areas and endemic fish species involved in the lakes with undetermined ecological water levels, and select endemic fish species whose average catch over the past 5 years has decreased by more than 30% compared to the original catch under the natural state of the lake as target species for lake habitat protection, based on historical changes in catch. The habitat factors include three physicochemical indicators: water temperature, flow rate, and dissolved oxygen.

3. The method for determining the tolerance range of a habitat suitability curve for lake ecological water levels according to claim 1, characterized in that, The basic lake data in step 2 includes meteorological data, hydrological data, water quality data, and underwater topographic data. The meteorological data includes daily precipitation, evaporation, air pressure, temperature, relative humidity, cloud cover coefficient, wind speed, and wind direction data from meteorological stations in the lake's basin. The hydrological data includes daily measured water levels in the lake area, inflow river flow, outflow river flow, and intake flow data. The water quality data includes monthly surface and deep water quality data from sampling points in the lake area, inflow river water quality, and outflow river water quality data. The underwater topographic data uses data from the 1985 National Elevation Datum survey.

4. The method for determining the tolerance range of a habitat suitability curve for lake ecological water levels according to claim 3, characterized in that, The specific steps in step 2 for dividing the computational grid are as follows: the computational grid is divided into planar rectangular grids. Considering simulation accuracy and computational efficiency, the total number of computational grids is determined. The computational grid can accurately reflect the changes in lake topography and shoreline. The bottom elevation of each layer of computational grid is discretized based on underwater topographic data interpolation.

5. The method for determining the tolerance range of a habitat suitability curve oriented towards lake ecological water level according to claim 4, characterized in that, The hydrodynamic governing equations in step 2 include the momentum equation and the continuity equation; The momentum equation is: The continuity equation is: In the formula: The curve-orthogonal coordinates are in the horizontal direction; The vertical σ coordinate; for The horizontal velocity component in the direction, in units of ; Total water depth, in units of ; This refers to water surface elevation, in units of... ; Atmospheric pressure, unit: ; Here are the coordinate transformation coefficients; the transformation coefficients in Cartesian coordinates are... ; for The depth-averaged velocity component in the direction, in units of ; Reference density Additional hydrostatic pressure, in units of ; The Coriolis force coefficient, in units of ; is the horizontal momentum diffusion coefficient, in units of ; The vertical turbulent viscosity coefficient is expressed in units of 1000 ppm. ; This is the vegetation resistance coefficient; This is the projected vegetation area; for Source and sink terms in terms of direction, in units of These are the source and sink terms of the mass conservation equation, in units of... ; The temperature and heat transfer control equations are: In the formula: and for Mass flux component in the direction, unit: T represents temperature, in °C. I represents the intensity of solar shortwave radiation, measured in W / m². 2 ; A b The vertical turbulent diffusion coefficient is expressed in units of 1000 ppm. S T Source and sink terms for heat exchange, expressed in J / s; Water quality control equations include mass conservation equations for water quality variables and dynamic equations for state variables; The mass conservation equation for water quality variables is: In the formula: This refers to the concentration of water quality variables, expressed in mg / L. These are the horizontal and vertical coordinates, respectively. coordinates velocity components, in units of ; They are respectively Turbulent diffusion coefficient in the direction of motion, in units of ; For internal / external source pools; The depth of the water column is expressed in meters (m). This is the factor for the change in the coordinates of the horizontal curve; The dynamic equations of the state variables are: In the formula: The kinetic rate; Source and sink terms are caused by external loads and / or internal reactions.

6. The method for determining the tolerance range of a habitat suitability curve for lake ecological water levels according to claim 5, characterized in that, The model boundary conditions in step 2 include hydrological boundary conditions and meteorological boundary conditions. The hydrological boundary conditions include the inflow of rivers into the lake, the outflow of rivers into the lake, the inflow of water intake, the water quality of rivers into the lake, and the water quality of rivers out of the lake. The meteorological boundary conditions include precipitation, evaporation, air pressure, air temperature, relative humidity, cloud cover coefficient, wind speed, and wind direction. The initial conditions of the model are based on measured meteorological, hydrological, and water quality data at the beginning of the calculation period; Model parameters include bottom roughness height, wind shielding coefficient, constant eddy viscosity, horizontal momentum diffusion coefficient, pure water extinction coefficient, surface absorbed solar radiation, initial riverbed temperature, and active bed temperature layer thickness. The calibration and verification of the model parameters are specifically carried out as follows: the hydrodynamic and water quality model parameters are calibrated and verified using measured data from the lake surface and vertical layers. The measured values ​​and simulated values ​​of the simulated indicators are compared. Three types of error statistical indicators, namely mean absolute error (MAE), relative error (RE), and root mean square error (RMSE), are used to measure the magnitude of the error. When the error statistical indicators meet the accuracy threshold requirements, the model is considered to have passed the verification. The specific accuracy threshold requirements for the error statistical indicators are: MAE less than 30%~50% of the standard deviation of the measured data, RE less than 25%~35%, and RMSE less than 40%~60% of the standard deviation of the measured data.

7. The method for determining the tolerance range of a habitat suitability curve oriented towards lake ecological water level according to claim 1, characterized in that, The water level gradient scheme described in step 4 is as follows: a water level gradient scheme is set at intervals of 0.5m based on the historical water level fluctuations and the legal operating water level of the lake; the historical water level fluctuations are determined by taking the maximum and minimum values ​​of the historical water level data of the lake, and the legal operating water level is determined according to the comprehensive watershed planning, scheduling procedures or local lake protection regulations.

8. The method for determining the tolerance range of a habitat suitability curve oriented towards lake ecological water level according to claim 1, characterized in that, The modification scheme designed in step 5 includes the following three modification methods: 1) Fixed bottom endpoint of the edge line and modified vertex, including fixed bottom endpoint of the left edge line and modified vertex of the right edge line; 2) Fixed vertex of the edge line and modified bottom endpoint, including fixed bottom endpoint of the left edge line and modified bottom endpoint of the right edge line; 3) Translate the edge line, including translating the left edge line and translating the right edge line.

9. The method for determining the tolerance range of a habitat suitability curve for lake ecological water level according to claim 1, characterized in that, The requirement to meet the error threshold in step 6 specifically means that the error is within the range of -0.1 to 0.1m.

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