Benthonic animal biological integrity index-based river suitable ecological flow calculation method

Abstract

The invention relates to the technical field of ecological management, and discloses a benthonic animal biological integrity index-based river suitable ecological flow calculation method, which comprises the following steps of: selecting a reference point based on habitat evaluation; iBI index screening is carried out based on river benthonic animal sampling data, and a benthonic animal integrity index is constructed; determining a reference value of the integrity index of the benthonic animals; constructing a habitat suitability model based on a benthonic animal integrity index; a research river reach is selected to construct a two-dimensional hydrodynamic model, values of the water depth, the flow velocity and the substrate of each grid in the research river reach under different incoming water conditions are obtained through simulation, the constructed habitat suitability model is imported, B-IBI distribution of benthonic animals of the research river reach under the corresponding scene can be obtained, and therefore the optimal river ecological flow recommended value of the B-IBI can be obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of ecological management, and in particular relates to a method for calculating a river suitable ecological flow based on a benthic animal biological integrity index. Background Art

[0002] At present, the calculation of ecological flow mainly uses the Tennant method, NGPRP method, basic flow method, minimum monthly average flow method and annual distribution method. This type of ecological flow calculation method only calculates the ecological flow through hydrological data, and does not consider the appropriate ecological flow requirements of aquatic organisms such as benthic animals. Therefore, when determining the ecological flow in the future, it is necessary to consider the appropriate flow required by aquatic organisms such as benthic animals.

[0003] In view of this, the present invention is proposed. Summary of the invention

[0004] In order to solve the above technical problems, the basic concept of the technical solution adopted by the present invention is:

[0005] A method for calculating the suitable ecological flow of a river based on the benthic animal biological integrity index comprises the following steps:

[0006] Step S1: Collect relevant data, main steps: conduct sampling survey on benthic animals in the river section and record the sampling water depth, flow velocity and median particle size of the bottom sediment;

[0007] Step S2: Selection of reference points for habitat assessment. Main steps: Comprehensively evaluate different sampling points; Score the river section for habitat based on 10 key indicators, including bottom quality, habitat complexity, V / D combination characteristics, riverbank stability, river channel changes, river water volume, vegetation diversity, water quality, human activity intensity and riverbank land use type. Each indicator is 10 points. Sampling points with a total score of more than 150 points are defined as reference points, and the remaining points are damaged points. The scores of each indicator are shown in Table 1.

[0008] Table 1 Index scoring table

[0009]

[0010]

[0011]

[0012] Step S3: Construct benthic animal biointegrity index, main steps:

[0013] a. According to the river basin conditions, multiple parameters were selected from community richness, community structure, pollution tolerance, trophic structure and species diversity as candidate parameters for the biointegrity index of river benthic animals to reflect the response of benthic animals to environmental changes;

[0014] b. Screen candidate indicators through parameter value distribution range analysis, discrimination ability analysis and redundancy analysis; after selecting candidate biological parameters, further analyze the distribution range of sampling point parameters and eliminate the following two types of parameters:

[0015] The distribution range is small, the response interval to environmental pressure is small, and the sensitivity is insufficient; in the reference point, the parameter itself varies greatly; the box plot method is used to compare the overlap of the interquartile range 25%-75% quantile box and the median of the reference point and the damaged point, and different scores are assigned according to the overlap; when the box plot score is ≥2, the parameter is considered to have the ability to distinguish environmental pressure and is used for the next step of analysis; the parameters that meet the requirements are tested for normality. If these parameters all conform to the normal distribution, the Pearson correlation analysis is used. If these parameters are not all normally distributed, the Spearman correlation analysis method is used to retain the parameters with a correlation coefficient |r|<0.75; if the correlation coefficient of two parameters |r|≥0.75, the parameter with relatively large information content and strong importance is retained as the core parameter;

[0016] c. Constructing the benthic biomass integrity index: After selecting the core parameters, the parameters need to be unified in dimension. Commonly used methods include: trisection, quartile and ratio method, and the ratio method is better than trisection and quartile methods. Therefore, it is recommended to use the ratio method to unify the dimensions of the core parameters, the core parameters that are negatively correlated with environmental pressure, and the values ​​of the reverse parameters after unification of dimensions (I S ) is calculated according to formula (1).

[0017]

[0018] Where: I S The core parameter I has the value after unification of dimensions; I O The measured value of the core parameter I; I T The critical value of core parameter I is the 5% quantile of core parameter I; E The expected value of the core parameter I is taken as the 95% quantile of the core parameter; 10 is a constant set to convert the basic distribution range of the value of I to between 0 and 10; the value of the core parameter (positive parameter) that is positively correlated with the environmental pressure after unification (I S ) is calculated according to formula (2).

[0019]

[0020] Where: IS The value of the core parameter I after unification of dimensions; I T The critical value of core parameter I is the 95% quantile of core parameter I; O Measured value of core parameter I; I E The expected value of the core parameter I is taken as the 5% quantile of the core parameter I; 10 is the value that makes I S The basic distribution range of the value is converted to a constant between 0 and 10; if I S >10, count as 10; if I S <0, counted as 0; the ratio of the sum of the core parameter scores after unification to the number of core parameters is the benthic biological integrity index B-IBI;

[0021] Step S4: Constructing a habitat suitability model based on the benthic biological integrity index B-IBI. The habitat suitability model is constructed based on the generalized additive model. The generalized additive model is a non-parametric regression model driven by data rather than a statistical distribution model. It can perform linear fitting on some explanatory variables. Its expression is:

[0022] g(μ(Y))=β0+f i (x i )+…f m (x m ) (3)

[0023] In the formula, g(μ(Y)) is the link function, μ(Y) is the expectation of Y, β0 is the intercept, and f i (x i ) is a non-parametric smooth function;

[0024] Based on the GAM model, the habitat suitability model was constructed with water depth H, flow velocity V and median sediment particle size as explanatory variables and B-IBI as the response variable.

[0025] Step S5: Select the study river section to construct a two-dimensional hydrodynamic model. The main steps are:

[0026] a. Terrain data preprocessing, mainly including removing terrain data noise points;

[0027] b. Calibration and verification of hydrodynamic model;

[0028] c. Simulate different flow levels and output the water depth H and flow velocity V of all river sections.

[0029] Step S6: Use the habitat suitability model to obtain the recommended value of river ecological flow. The main steps are: input H and V simulated by the hydrodynamic model and the median particle size obtained from the survey into the habitat suitability model that has been built in step S4 to obtain the highest habitat suitability value under different flow levels, thereby obtaining the optimal river ecological flow recommendation value of B-IBI.

[0030] As a preferred embodiment of the present invention, in step S4, based on the generalized additive model, the water depth H, flow velocity V and median particle size of the bottom sediment where benthic animals live are used as explanatory variables, and the benthic animal biological integrity index B-IBI is used as the response variable to build a habitat suitability model.

[0031] As a preferred embodiment of the present invention, in step S6, the hydrodynamic model constructed in step S5 is simulated at different flow rates, and the water depth H and flow velocity V at different flow rates are output, and the water depth H and flow velocity V at different flow rates are input together with the median particle size of the bottom sediment obtained by the survey into the habitat suitability model constructed in step S4. The predicted B-IBI distribution is obtained through the habitat suitability model. Different B-IBI distributions are obtained at different flow rates, and the flow with the highest B-IBI is determined as the ecological flow suitable for the growth of benthic animals in the area.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention constructs the B-IBI core parameters of the river section suitable for the study, and determines the baseline value of B-IBI by comparing the reference point and the damaged point; based on the generalized additive model (GAM), the quantitative relationship between B-IBI and water depth, flow velocity, and bottom quality is obtained, thereby constructing a habitat suitability model based on the benthic animal integrity index; and then combines the hydrodynamic model to simulate the water depth, flow velocity, and bottom quality distribution of the study area under different flow rates, thereby calculating the B-IBI distribution of each grid in the study area, and taking the maximum B-IBI of all grids as the optimal solution, thereby deducing the recommended ecological flow value most suitable for the growth of benthic animals. The physical process and biological response mechanism of this method are clear, and the evaluation calculation method is simple and easy to operate, providing reliable theoretical and technical support for guiding the formulation of ecological flow targets and realizing river ecological protection and restoration.

[0034] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 It is a flow chart of the method for calculating the suitable ecological flow of a river based on the Benthic Biological Integrity Index (B-IBI) of the present invention;

[0037] Figure 2This is a schematic diagram of the Chishui River Basin and the distribution map of sampling points;

[0038] Figure 3 Satellite image and hydrodynamic grid map of Chishui River in Chishui City;

[0039] Figure 4 construct parameter maps for habitat suitability models;

[0040] Figure 5 This is the distribution diagram of water depth, flow velocity and B-IBI value in Chishui City under different flow levels. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention.

[0042] Embodiment 1:

[0043] like Figures 1 to 3 As shown in FIG. 1 , a method for calculating the suitable ecological flow of a river based on the benthic animal biological integrity index includes the following steps:

[0044] Step S1: Collect relevant data, main steps: conduct sampling survey on benthic animals in the river section and record the sampling water depth, flow velocity and median particle size of the bottom sediment;

[0045] Step S2: Selection of reference points for habitat assessment. Main steps: Comprehensively evaluate different sampling points; Score the river section for habitat based on 10 key indicators, including bottom quality, habitat complexity, V / D combination characteristics, river bank stability, river channel changes, river water volume, vegetation diversity, water quality, human activity intensity and river bank land use type. Each indicator is 10 points. Sampling points with a total score of more than 150 points are defined as reference points, and the remaining points are damaged points. The scores of each indicator are shown in Table 1.

[0046] Table 1 Index scoring table

[0047]

[0048]

[0049] Step S3: Construct benthic animal biointegrity index, main steps:

[0050] a. According to the river basin conditions, multiple parameters were selected from community richness, community structure, pollution tolerance, trophic structure and species diversity as candidate parameters for the biointegrity index of river benthic animals to reflect the response of benthic animals to environmental changes;

[0051] b. Screen candidate indicators through parameter value distribution range analysis, discrimination ability analysis and redundancy analysis; after selecting candidate biological parameters, further analyze the distribution range of sampling point parameters and eliminate the following two types of parameters:

[0052] The distribution range is small, the response interval to environmental pressure is small, and the sensitivity is insufficient; in the reference point, the parameter itself varies greatly; the box plot method is used to compare the overlap of the interquartile range 25%-75% quantile box and the median of the reference point and the damaged point, and different scores are assigned according to the overlap; when the box plot score is ≥2, the parameter is considered to have the ability to distinguish environmental pressure and is used for the next step of analysis; the parameters that meet the requirements are tested for normality. If these parameters all conform to the normal distribution, the Pearson correlation analysis is used. If these parameters are not all normally distributed, the Spearman correlation analysis method is used to retain the parameters with a correlation coefficient |r|<0.75; if the correlation coefficient of two parameters |r|≥0.75, the parameter with relatively large information content and strong importance is retained as the core parameter;

[0053] c. Constructing the benthic biomass integrity index: After selecting the core parameters, the parameters need to be unified in dimension. Commonly used methods include: trisection, quartile and ratio method, and the ratio method is better than trisection and quartile methods. Therefore, it is recommended to use the ratio method to unify the dimensions of the core parameters, the core parameters that are negatively correlated with environmental pressure, and the values ​​of the reverse parameters after unification of dimensions (I S ) is calculated according to formula (1).

[0054]

[0055] Where: I S The core parameter I has the value after unification of dimensions; I O The measured value of the core parameter I; I T The critical value of core parameter I is the 5% quantile of core parameter I; E The expected value of the core parameter I is taken as the 95% quantile of the core parameter; 10 is a constant set to convert the basic distribution range of the value of I to between 0 and 10; the value of the core parameter (positive parameter) that is positively correlated with the environmental pressure after unification (I S ) is calculated according to formula (2).

[0056]

[0057] Where: I S The value of the core parameter I after unification of dimensions; I T The critical value of core parameter I is the 95% quantile of core parameter I; O Measured value of core parameter I; I EThe expected value of the core parameter I is taken as the 5% quantile of the core parameter I; 10 is the value that makes I S The basic distribution range of the value is converted to a constant between 0 and 10; if I S >10, count as 10; if I S <0, counted as 0; the ratio of the sum of the core parameter scores after unification to the number of core parameters is the benthic biological integrity index B-IBI;

[0058] Step S4: Constructing a habitat suitability model based on the benthic biological integrity index B-IBI. The habitat suitability model is constructed based on the generalized additive model. The generalized additive model is a non-parametric regression model driven by data rather than a statistical distribution model. It can perform linear fitting on some explanatory variables. Its expression is:

[0059] g(μ(Y))=β0+f i (x i )+…f m (x m ) (3)

[0060] In the formula, g(μ(Y)) is the link function, μ(Y) is the expectation of Y, β0 is the intercept, and f i (x i ) is a non-parametric smooth function;

[0061] Based on the GAM model, the habitat suitability model was constructed with water depth H, flow velocity V and median sediment particle size as explanatory variables and B-IBI as the response variable.

[0062] Step S5: Select the study river section to construct a two-dimensional hydrodynamic model. The main steps are:

[0063] a. Terrain data preprocessing, mainly including removing terrain data noise points;

[0064] b. Calibration and verification of hydrodynamic model;

[0065] c. Simulate different flow levels and output the water depth H and flow velocity V of all river sections.

[0066] Step S6: Use the habitat suitability model to obtain the recommended value of river ecological flow. The main steps are: input H and V simulated by the hydrodynamic model and the median particle size obtained from the survey into the habitat suitability model that has been built in step S4 to obtain the highest habitat suitability value under different flow levels, thereby obtaining the optimal river ecological flow recommendation value of B-IBI.

[0067] Furthermore, in step S4, based on the generalized additive model, a habitat suitability model is constructed with the water depth H, flow velocity V and median particle size of the bottom sediments where benthic animals live as explanatory variables and the benthic animal biological integrity index B-IBI as the response variable.

[0068] Furthermore, in step S6, the hydrodynamic model constructed in step S5 is simulated at different flow rates, and the water depth H and flow velocity V at different flow rates are output, and are input together with the median particle size of the bottom sediment obtained from the survey into the habitat suitability model constructed in step S4. The predicted B-IBI distribution is obtained through the habitat suitability model. Different B-IBI distributions are obtained under different flow rates, and the flow with the highest B-IBI is determined as the ecological flow suitable for the growth of benthic animals in the area.

[0069] This study took Chishui River as the research object, and conducted a benthic sampling survey on the Chishui River. More than 200 sets of data were collected, and the water depth (H), flow velocity (V) and median sediment particle size (D50) were recorded. The total number of taxonomic units of benthic animals in Chishui River, the number of EPT taxonomic units, the relative abundance of predators and the Pielou evenness index were used as core parameters to construct the biotic integrity index (B-IBI). The generalized additive model was used to construct the habitat suitability model with water depth (H), flow velocity (V) and median sediment particle size (D50) as explanatory variables and the biotic integrity index as the response variable. The hydrodynamic model of the Chishui section of Chishui River was constructed by MIKE21, and the water depth (H) and flow velocity (V) of the Chishui section of Chishui River under different flow rates were simulated. The habitat suitability under different flow levels was simulated by the constructed habitat suitability model, and the flow with the highest habitat suitability was selected and determined as the ecological flow.

[0070] According to the geographical location, water ecology and land use pattern of the Chishui River, 26 sampling points were set up in the main stream of the Chishui River. Field survey data were collected in March, July and November 2023. The habitat scores were given to the 26 sampling points through the habitat evaluation scoring mentioned in step 2. Points with scores above 150 were considered to be relatively ideal ecological environment points, totaling 11. Among them, there were 7 points in the upstream, namely 2 Baotou (88), 3 Yanjiao (92), 4 Banjiujing (84), 6 Shuilaopu (79), 7 Xujiahe (93), 9 Wantan Bridge (78) and 12 Wumahekou (90); there were four points in the middle and lower reaches, namely 14 Hema (78), 15 Erlangtan (77), 16 Qianjiangsi (76) and 25 Mixi Township (76), and the rest were damaged points.

[0071] Twenty-two parameters (see Table 1) were selected from five aspects, including community richness, community structure composition, pollution tolerance, trophic structure and species diversity, as candidate parameters for the biointegrity index of benthic animals in the Chishui River Basin, in order to reflect the response of benthic animals to environmental changes as comprehensively as possible.

[0072] Table 1 Candidate indicators and their response to interference

[0073]

[0074]

[0075] The candidate indicators were screened through parameter value distribution range analysis, discriminant ability analysis and redundancy analysis. The core parameters finally retained were the total number of taxa, the number of EPT taxa, the relative abundance of predators and the Pielou evenness index. The retained core parameters were used to construct the biotic integrity index. The biotic integrity index and its corresponding water depth, velocity and bottom quality are shown in Table 2.

[0076] Table 2 Biological integrity index in relation to water depth, flow velocity and bottom quality

[0077]

[0078]

[0079]

[0080]

[0081] A habitat suitability model was constructed using the generalized additive model (GAM) with water depth (H), flow velocity (V) and median sediment particle size (D50) as explanatory variables and the biotic integrity index as the response variable. The model parameters are as follows.

[0082] MIKE21 was used to construct a two-dimensional hydrodynamic model for the Chishui section of the Chishui River. The grid of the Chishui section is shown in the figure. The hydrodynamic model was calibrated and verified, and the Nash coefficient was calculated to be 99.78%, indicating that the simulation results of the hydrodynamic model are reliable. The simulation was carried out at six flow levels of 65.4, 142, 147, 158, 164 and 325 m3 / s. The distribution of the biological integrity index in the river section is shown in the figure. The area summary and proportion within the IBI score range of different flow levels are shown in Table 3.

[0083] Table 3 Different IBI range areas and score proportions at different flow levels

[0084]

[0085]

[0086] Calculated by the habitat suitability model, it was found that at flow rates of 65.4, 142, 147, 158, 164 and 325 m3 / s, the B-IBI value of the Chishui River in Chishui City was the highest when the flow rate was 325 m3 / s, so 325 m3 / s was positioned as the ecological flow suitable for benthic animals.

[0087] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for calculating the suitable ecological flow of a river based on the benthic animal biological integrity index, characterized in that: The steps include: Step S1: Collect relevant data, main steps: conduct sampling survey on benthic animals in the river section and record the sampling water depth, flow velocity and median particle size of the bottom sediment; Step S2: Selection of reference points for habitat assessment. Main steps: Comprehensively evaluate different sampling points; Score the habitat of the river section based on 10 key indicators, including bottom quality, habitat complexity, V / D combination characteristics, river bank stability, river channel changes, river water volume, vegetation diversity, water quality, human activity intensity and river bank land use type. Each indicator is 10 points. The sampling points with a total score of more than 150 points are defined as reference points, and the remaining points are damaged points and scored for each indicator. Step S3: Construct benthic animal biointegrity index, main steps: a. According to the river basin conditions, multiple parameters were selected from community richness, community structure, pollution tolerance, trophic structure and species diversity as candidate parameters for the biointegrity index of river benthic animals to reflect the response of benthic animals to environmental changes; b. Screen candidate indicators through parameter value distribution range analysis, discrimination ability analysis and redundancy analysis; after selecting candidate biological parameters, further analyze the distribution range of sampling point parameters and eliminate the following two types of parameters: The distribution range is small, the response interval to environmental pressure is small, and the sensitivity is insufficient; in the reference point, the parameter itself varies greatly; the box plot method is used to compare the overlap of the interquartile range 25%-75% quantile box and the median of the reference point and the damaged point, and different scores are assigned according to the overlap; when the box plot score is ≥2, the parameter is considered to have the ability to distinguish environmental pressure and is used for the next step of analysis; the parameters that meet the requirements are tested for normality. If these parameters all conform to the normal distribution, the Pearson correlation analysis is used. If these parameters are not all normally distributed, the Spearman correlation analysis method is used to retain the parameters with a correlation coefficient |r|<0.75; if the correlation coefficient of two parameters |r|≥0.75, the parameter with relatively large information content and strong importance is retained as the core parameter; c. Constructing the benthic biomass integrity index: After selecting the core parameters, the parameters need to be unified in dimension. Commonly used methods include: trisection, quartile and ratio method, and the ratio method is better than trisection and quartile methods. Therefore, it is recommended to use the ratio method to unify the dimensions of the core parameters, the core parameters that are negatively correlated with environmental pressure, and the values ​​of the reverse parameters after unification (I S ) is calculated according to formula (1). Where: I S The core parameter I has the value after unification of dimensions; I O The measured value of the core parameter I; I T The critical value of core parameter I is the 5% quantile of core parameter I; E The expected value of the core parameter I is taken as the 95% quantile of the core parameter; 10 is a constant set to convert the basic distribution range of the value of I to between 0 and 10; the value of the core parameter positive parameter that is positively correlated with the environmental pressure after the unified amount is I S Calculate according to formula 2. Where: I S The value of the core parameter I after unification of dimensions; I T The critical value of core parameter I is the 95% quantile of core parameter I; O Measured value of core parameter I; I E The expected value of the core parameter I is taken as the 5% quantile of the core parameter I; 10 is the value that makes I S The basic distribution range of the value is converted to a constant between 0 and 10; if I S >10, count as 10; if I S <0, counted as 0; the ratio of the sum of the core parameter scores after unification to the number of core parameters is the benthic biological integrity index B-IBI; Step S4: Constructing a habitat suitability model based on the benthic biological integrity index B-IBI. The habitat suitability model is constructed based on the generalized additive model. The generalized additive model is a non-parametric regression model driven by data rather than a statistical distribution model. It can perform linear fitting on some explanatory variables. Its expression is: g(μ(Y))=β0+f i ( x i )+…f m ( x m ) (3) In the formula, g(μ(Y)) is the link function, μ(Y) is the expectation of Y, β0 is the intercept, and f i (x i ) is a non-parametric smooth function; Based on the GAM model, the habitat suitability model was constructed with water depth H, flow velocity V and median sediment particle size as explanatory variables and B-IBI as the response variable. Step S5: Select the study river section to construct a two-dimensional hydrodynamic model. The main steps are: a. Terrain data preprocessing, mainly including removing terrain data noise points; b. Calibration and verification of hydrodynamic model; c. Simulate different flow levels and output the water depth H and flow velocity V of all river sections. Step S6: Use the habitat suitability model to obtain the recommended value of river ecological flow. The main steps are: input H and V simulated by the hydrodynamic model and the median particle size obtained from the survey into the habitat suitability model that has been built in step S4 to obtain the highest habitat suitability value under different flow levels, thereby obtaining the optimal river ecological flow recommendation value of B-IBI.

2. The method for calculating the suitable ecological flow of a river based on the benthic animal biological integrity index according to claim 1 is characterized in that: In step S4, based on the generalized additive model, the water depth H, flow velocity V and median particle size of the bottom sediment where benthic animals live are used as explanatory variables, and the benthic animal biological integrity index B-IBI is used as the response variable to build a habitat suitability model.

3. The method for calculating the suitable ecological flow of a river based on the benthic animal biological integrity index according to claim 1 is characterized in that: In step S6, the hydrodynamic model constructed in step S5 is simulated at different flow rates, and the water depth H and flow velocity V at different flow rates are output. The water depth H and flow velocity V at different flow rates are input together with the median particle size of the bottom sediment obtained from the survey into the habitat suitability model constructed in step S4. The predicted B-IBI distribution is obtained through the habitat suitability model. Different B-IBI distributions are obtained under different flow rates. The flow with the highest B-IBI is determined as the ecological flow suitable for the growth of benthic animals in the area.

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