Drainage basin water environment capacity distribution method based on control unit

Abstract

The invention belongs to the technical field of water conservancy and environmental science, and discloses a drainage basin water environment capacity allocation method based on a control unit, which comprises the following steps: constructing a hydrological hydrodynamic model and a river water quality model according to hydrological information of a target drainage basin; determining hydrological conditions of each control unit in the target drainage basin according to the hydrological hydrodynamic model; determining a water environment capacity calculation standard under the hydrological condition according to the river water quality model; and constructing a multi-objective optimization model according to the water environment capacity evaluation standard and the water environment capacity calculation standard, and determining the water environment capacity distributed to each control unit under the hydrological condition according to the multi-objective optimization model. According to the drainage basin water environment capacity allocation method based on the control units, the control units are divided through the catchment range and the administrative division, the water environment capacity of each control unit is fairly allocated by adopting a multi-objective optimization algorithm, and the pollutant discharge amount of each control unit is further strictly controlled; and a fair and objective treatment basis is provided for accurate treatment of the drainage basin.

Description

Technical Field

[0001] The invention discloses a watershed water environment capacity allocation method based on a control unit, belonging to the technical field of water conservancy and environmental science. Background Art

[0002] With the acceleration of industrialization and urbanization, water environment problems in river basins have become increasingly severe, and water pollution and ecological damage have become the key bottlenecks restricting the sustainable development of the economy and society. In order to effectively manage and protect water resources in river basins, river basins are usually divided into multiple control units to achieve zoning management of water resources and ensure that water quality meets standards. However, due to technical, economic or geographical limitations, it is often impossible to conduct comprehensive monitoring of each control unit. Therefore, under the condition that it is impossible to ensure that each control unit has a corresponding control section, it is an important basis for formulating river basin water environment protection plans and pollutant emission standards to allocate water environment capacity to each control unit and then reduce pollutants according to the current pollution load of each control unit.

[0003] Traditional methods for allocating water environment capacity in a river basin mainly include the equal proportion allocation method, the pollution contribution rate method, and the analytic hierarchy process. The equal proportion allocation method allocates based on the existing pollution load conditions and determines the discharge volume of each control unit according to the equal reduction ratio. The pollution contribution rate method allocates according to the contribution of the pollution load of each control unit to the target section of the water quality in the river basin, which usually requires the construction of a complex response matrix. The analytic hierarchy process allocates based on an indicator system constructed based on expert experience, relying more on subjective judgment and experience accumulation. However, these methods often allocate based on a single water quality target or economic indicator, ignoring the fairness and sustainability of the allocation, making it difficult to balance the interests of all parties in practical applications and to achieve optimal allocation of water resources.

[0004] In addition, most of the existing allocation methods lack in-depth research on the hydrological and hydrodynamic processes of the river basin and the migration and transformation mechanisms of pollutants, resulting in allocation results that often deviate from the actual situation and are difficult to effectively guide river basin water environment management. Summary of the invention

[0005] The purpose of this application is to provide a method for allocating water environment capacity of a watershed based on a control unit, so as to solve the technical problems in the prior art that, under the condition that each control unit cannot be guaranteed to have a corresponding control section, the allocation of water environment capacity of the watershed is unfair, unsustainable, and lacks consideration of hydrological and hydrodynamic processes. To achieve the above purpose, the present invention proposes a method for allocating water environment capacity of a watershed based on a control unit, comprising the following steps:

[0006] Construct hydrological and hydrodynamic models and river water quality models based on the hydrological information of the target watershed;

[0007] Determining the hydrological conditions of each control unit in the target watershed according to the hydrological and hydrodynamic model;

[0008] Determining the calculation standard of water environment capacity under the hydrological conditions according to the river water quality model;

[0009] A multi-objective optimization model is constructed according to the water environment capacity assessment standard and the water environment capacity calculation standard, and the water environment capacity allocated to each control unit under the hydrological conditions is determined according to the multi-objective optimization model.

[0010] Preferably, the calculation standard of the water environment capacity under the hydrological conditions is determined according to the river water quality model, specifically including:

[0011] Determine the calculation criteria of water environment capacity of each control unit under the hydrological conditions according to the river water quality model;

[0012] The water environment capacity calculation standard of the target area under the hydrological conditions is constructed according to the water environment capacity calculation criteria of each control unit under the hydrological conditions.

[0013] Preferably, before constructing the multi-objective optimization model according to the water environment capacity assessment standard and the water environment capacity calculation standard, the method further includes:

[0014] Establish water environment capacity assessment standards that reflect the preset characteristics of water environment capacity allocation.

[0015] Preferably, the preset characteristic is a fairness characteristic, and a water environment capacity assessment standard reflecting the preset characteristic of water environment capacity allocation is established, specifically including:

[0016] Selecting an indicator system that meets the fairness characteristics;

[0017] The Gini coefficient of each indicator in the indicator system is calculated, and the comprehensive Gini coefficient of the indicator system is determined according to the weight of each indicator, and the comprehensive Gini coefficient is used as the water capacity assessment standard.

[0018] Preferably, the indicator is population, water resources, farmland area, industrial water consumption, domestic water consumption, wastewater discharge or water quality compliance rate.

[0019] Preferably, the objective function of the multi-objective optimization model is:

[0020] The sum of the water environment capacities of the control units is the largest;

[0021] The comprehensive Gini coefficient is the smallest.

[0022] Preferably, the constraints of the multi-objective optimization model are:

[0023] The pollutant concentration of any control section in the target watershed meets its corresponding preset requirements.

[0024] Preferably, determining the water environment capacity allocated to each control unit under the hydrological conditions according to the multi-objective optimization model specifically includes:

[0025] Obtaining a solution result of the multi-objective optimization model under the hydrological conditions;

[0026] The water environment capacity allocated to each control unit under the hydrological conditions is determined according to the solution result and the water environment capacity calculation standard.

[0027] Preferably, the hydrological conditions are static design hydrological conditions or dynamic design hydrological conditions.

[0028] Preferably, constructing the hydrological and hydrodynamic model further comprises:

[0029] The hydrological and hydrodynamic model is calibrated and verified based on the measured hydrological data of the target watershed.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The watershed water environment capacity allocation method based on control units of the present invention divides the control units by water catchment area and administrative divisions, and adopts a multi-objective optimization algorithm to fairly allocate the water environment capacity of each control unit, and further strictly controls the pollutant emissions of each control unit to provide a fair and objective management basis for precise watershed management. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the water environment capacity allocation process of the basin based on the control unit;

[0033] Figure 2 This is a schematic diagram of an optimal solution set obtained through multi-objective optimization in Example 2 of the present invention, taking chemical oxygen demand (COD) as an example indicator;

[0034] Figure 3 This is the optimal allocation result of the water environment capacity corresponding to each control unit after the optimal solution is selected in the second embodiment of the present invention. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Embodiment 1:

[0037] See also Figure 1 As shown, the purpose of this embodiment is to provide a method for allocating water environment capacity of a watershed based on a control unit, comprising the following steps:

[0038] S1. constructing a hydrological and hydrodynamic model and a river water quality model according to the hydrological information of the target watershed;

[0039] Water environment capacity is the maximum amount of pollutants that a water body can carry while maintaining specific water quality targets. It reflects the water body's ability to withstand pollutants and the natural laws of pollutant migration and transformation.

[0040] First, the present invention divides the target watershed into multiple control units, and specifically divides the catchment area corresponding to each control section according to the river channel and the control section; because water quality target management needs to consider administrative boundaries, the catchment area and the boundaries of administrative divisions are comprehensively considered to reasonably divide multiple control units for water environment capacity calculation.

[0041] Then, a hydrological and hydrodynamic model is constructed according to the hydrological information of the target basin, and the geospatial data and basic attribute data of the target basin, such as hydrology, meteorology, topography, land use, and social economy, are specifically sorted out to construct a basin hydrological and hydrodynamic model; wherein, in a further embodiment, constructing a hydrological and hydrodynamic model also includes: calibrating and verifying the hydrological and hydrodynamic model according to the measured hydrological data of the target basin. Specifically, the key parameters of the hydrological and hydrodynamic model are calibrated and verified using a series of hydrological monitoring data of the hydrological station in the target basin.

[0042] S2. Determine the hydrological conditions of each control unit in the target basin according to the hydrological and hydrodynamic model;

[0043] Specifically, the calibrated and verified hydrological and hydrodynamic model is used to calculate the design hydrological conditions of each control unit, and the design hydrological conditions are static design hydrological conditions or dynamic design hydrological conditions.

[0044] Among them, static design hydrological conditions refer to the hydrological conditions determined under specific environmental risk conditions. These conditions are hydrological constants derived based on a certain allowable recurrence period. The specific calculation steps are as follows:

[0045] (1) At least 10 consecutive years of meteorological data such as rainfall, temperature, wind speed, and solar radiation are used as boundary conditions and input into the hydrological and hydrodynamic model. Through the simulation operation of the model, key hydrological parameters such as the monthly average flow and average flow velocity of the river in the basin are obtained.

[0046] (2) Sort the simulated monthly average flows from largest to smallest. On this basis, calculate the lowest monthly average flow for each control unit at a 90% guarantee rate. This flow value is considered as the static design hydrological condition for calculating the water environment capacity.

[0047] Dynamic design hydrological conditions refer to continuous flow sequences, which are not explicitly expressed as specific return periods. The specific calculation steps are as follows:

[0048] (1) Select meteorological data such as rainfall, temperature, wind speed, and solar radiation in a typical year (or consecutive years) as boundary conditions and input them into the hydrological and hydrodynamic model. Through the simulation operation of the model, key hydrological parameters such as the monthly average flow and average flow velocity of the river in the basin in a typical year (or consecutive years) are obtained.

[0049] (2) The obtained monthly average flow and average velocity data are directly used as the dynamic design hydrological conditions for water environment capacity.

[0050] Static design hydrological conditions are suitable for areas where hydrological data are lacking. Dynamic design hydrological conditions fully consider the complexity and variability of hydrological conditions, which helps to more accurately assess water environment capacity and formulate corresponding management strategies.

[0051] It also includes building a river water quality model based on the hydrological information of the target basin. The river water quality model describes the attenuation process of pollutants in the river channel within the target basin through the following formula:

[0052]

[0053] Where:

[0054] C x is the pollutant concentration after the pollutant flows along the river longitudinally for a distance x, mg / L;

[0055] C0 is the pollutant concentration at the previous control section, mg / L;

[0056] K is the comprehensive attenuation coefficient of pollutants, 1 / s, which is used to reflect the natural degradation rate of pollutants in the river;

[0057] x is the longitudinal distance along the river channel, m;

[0058] u is the average flow velocity, m / s.

[0059] S3. Determine the calculation standard of water environment capacity under the hydrological conditions according to the river water quality model;

[0060] In a further embodiment, the water environment capacity calculation standard under the hydrological conditions is determined according to the river water quality model, specifically including: determining the water environment capacity calculation criteria for each control unit under the hydrological conditions according to the river water quality model; and constructing the water environment capacity calculation standard for the target area under the hydrological conditions according to the water environment capacity calculation criteria for each control unit under the hydrological conditions.

[0061] Specifically, the water environment capacity calculation criteria for each control unit under static or dynamic design hydrological conditions, the specific calculation formula of this criterion is as follows:

[0062]

[0063] Where:

[0064] 86.4 represents the unit conversion factor;

[0065] M i It represents the water environment capacity of river section i in the target basin, kg / d;

[0066] Q i-1 represents the flow from the previous river section into river section i, m 3 / s;

[0067] q i represents the flow rate of the interval into the river section i, m 3 / s;

[0068] C i-1 and C i Respectively represent the pollutant concentrations at the beginning and end of river section i, mg / L;

[0069] x i represents the length of river section i, m;

[0070] u i Represents the average flow velocity of river section i, m / s.

[0071] Specifically, the water environment capacity calculation standard of the target area is constructed according to the water environment capacity calculation criteria of each control unit. Specifically, the water environment capacity calculation criteria of each control unit are first added.

[0072] The water environment capacity calculation formulas of multiple control units are added together to obtain the water environment capacity calculation standard for the entire river. The calculation formula for this standard is as follows:

[0073]

[0074] Where:

[0075] M represents the water environment capacity of all river sections in the entire target basin, kg / d;

[0076] C s Indicates the water quality target at the outlet of the last river section, mg / L.

[0077] S4. Construct a multi-objective optimization model according to the water environment capacity assessment standard and the water environment capacity calculation standard, and determine the water environment capacity allocated to each control unit under the hydrological conditions according to the multi-objective optimization model.

[0078] In a further embodiment, before constructing the multi-objective optimization model according to the water environment capacity assessment standard and the water environment capacity calculation standard, it also includes: establishing a water environment capacity assessment standard reflecting the preset characteristics of water environment capacity allocation. The preset characteristics are used to reflect the allocation benchmark of water environment capacity, generally including fairness characteristics, efficiency characteristics, etc.

[0079] In a further embodiment, the preset characteristic is a fairness characteristic, and a water environment capacity assessment standard reflecting the preset characteristic of water environment capacity allocation is established, specifically including:

[0080] An indicator system that meets the fairness characteristics is selected; the Gini coefficient of each indicator in the indicator system is calculated, and the comprehensive Gini coefficient of the indicator system is determined according to the weight of each indicator, and the comprehensive Gini coefficient is used as the water capacity assessment standard.

[0081] Furthermore, the indicators are population, water resources, farmland area, industrial water consumption, domestic water consumption, wastewater discharge or water quality compliance rate.

[0082] Specifically, the Gini coefficient of each indicator is calculated as follows:

[0083]

[0084] Where:

[0085] i is the partition number of each control unit;

[0086] j is the number of the evaluation index;

[0087] G j is the Gini coefficient of indicator j;

[0088] X i,j is the cumulative proportion of index j of the i-th control unit;

[0089] Y i The cumulative proportion of water environment capacity allocated to the ith control unit;

[0090] When i=1, X (i-1),j =0, Y i-1 =0.

[0091] Specifically, the weight of each indicator is calculated and the comprehensive Gini coefficient G is obtained by weighting.

[0092]

[0093] Where:

[0094] G represents the comprehensive Gini coefficient;

[0095] m represents the number of indicators;

[0096] α j represents the weight of indicator j.

[0097] Furthermore, a multi-objective optimization model is constructed according to the water environment capacity assessment standard and the water environment capacity calculation standard, and the objective function of the multi-objective optimization model is:

[0098] The sum of the water environment capacities of the control units is the largest;

[0099] The comprehensive Gini coefficient is the smallest.

[0100] Specifically, the objective function is as follows:

[0101]

[0102] Furthermore, the constraints of the multi-objective optimization model are:

[0103] The pollutant concentration of any control section in the target watershed meets its corresponding preset requirements.

[0104] Specifically, the constraints are determined according to the river assessment targets. For river sections with assessment targets in the control sections, the pollutant concentration at the end should not be higher than the assessment target concentration:

[0105] C j ≤C s,j

[0106] Where:

[0107] C j It represents the pollutant concentration at the end of the river section i with the assessment target in the control section, mg / L;

[0108] C s,j It is the assessment target concentration of the corresponding control section, mg / L.

[0109] Further determining the water environment capacity allocated to each control unit under the hydrological conditions according to the multi-objective optimization model specifically includes:

[0110] Obtaining a solution result of the multi-objective optimization model under the hydrological conditions;

[0111] The water environment capacity allocated to each control unit under the hydrological conditions is determined according to the solution result and the water environment capacity calculation standard.

[0112] Specifically, the pollutant concentration C at the end of river section i i is the decision variable, and the multi-objective optimization algorithm is used to solve the optimal solution set;

[0113] According to the optimal solution set obtained, decision makers can select the appropriate optimal solution and use the formula corresponding to the water environment capacity calculation criterion to calculate the water environment capacity of each control unit.

[0114] The method for allocating water environment capacity of a watershed based on a control unit provided by the present invention has significant beneficial effects, which are specifically reflected in the following aspects:

[0115] Scientific division of control units: This invention realizes the reasonable division of watershed control units by comprehensively considering the catchment area and administrative divisions. This division method is not only convenient for management and implementation, but also can more accurately reflect the water environment characteristics and pollution conditions of different areas in the watershed, providing a solid foundation for the subsequent calculation and allocation of water environment capacity.

[0116] Accurate calculation and fair distribution: Using advanced multi-objective optimization algorithms, the present invention can comprehensively consider multiple environmental, economic and social factors, calculate the water environment capacity of each control unit, and achieve fair and reasonable distribution. This ensures that the responsibilities and obligations of different regions in the basin in terms of environmental protection are balanced, and promotes the overall improvement of the basin's water environment.

[0117] Strictly control pollutant emissions: By strictly controlling the pollutant emissions of each control unit, the present invention effectively limits the pollution sources in the basin and improves the pertinence and effectiveness of pollution control. This not only helps to reduce the total amount of pollutant emissions, but also significantly improves the self-purification capacity and ecological health level of the basin water body.

[0118] Providing a basis for precise pollution control: The water environment capacity calculation and allocation method provided by the present invention provides a fair and objective basis for precise pollution control in the river basin. It enables river basin management departments to formulate more reasonable and effective pollution prevention and control measures and governance plans based on scientific data and analysis results, thereby promoting the continuous improvement and enhancement of the water environment quality in the river basin.

[0119] Embodiment 2

[0120] Taking a river in a certain area as an example, the water environment capacity calculation and allocation based on the control unit are as follows:

[0121] (1) Divide the control unit for water environment capacity calculation;

[0122] The main stream of the river is 30.2 kilometers long, and the basin covers an area of ​​92.7 square kilometers. The basin involves 2 townships and 17 administrative villages. There is a control section at the outlet of the basin, and its water quality target is set as the surface water Class III standard. According to the basin water system and digital elevation model, the basin is divided into 125 sub-basins using GIS hydrological analysis tools. Based on the sub-basin boundaries and administrative division boundaries, the basin is finally integrated and divided into 12 control units for water environment capacity calculation. According to the basin area, control sections and management needs, the number of control units should be kept between 10 and 30.

[0123] (2) Construct a hydrological and hydrodynamic model to calculate the design hydrological conditions of each control unit;

[0124] 1) Collect the geographic spatial data and basic attribute data of the basin, among which the spatial data include ground elevation data, basin water system, land cover data, and soil data; the attribute data include meteorological data, hydrological data, pollution source distribution data, agricultural management data, water quality monitoring data, etc., to construct a basin hydrological and hydrodynamic model; 2) Use the average monthly flow at the basin outlet from 2008 to 2020 to calibrate the model parameters, and use the average monthly flow data from 2015 to 2016 to verify the model; 3) Input meteorological data such as rainfall, temperature, wind speed, and solar radiation from 1979 to 2020 as boundary conditions into the hydrological and hydrodynamic model to simulate the average monthly flow and average flow velocity of the river; 4) Sort the monthly average flow from large to small, and calculate the average flow of the driest month with a 90% guarantee rate for each control unit as the static design hydrological condition for calculating the water environment capacity.

[0125] (3) Construct a river water quality model, list the water environment capacity calculation formula for each control unit and sum them up.

[0126] 1) Construct a river water quality model. The method for constructing the river water quality model includes:

[0127]

[0128] In the formula, C x is the pollutant concentration after flowing through distance x, mg / L;

[0129] C0 is the pollutant concentration at the previous control section, mg / L;

[0130] K is the comprehensive attenuation coefficient of pollutants, 1 / s;

[0131] x is the longitudinal distance along the river section, m;

[0132] u is the average flow velocity, m / s.

[0133] 2) List the calculation formula of water environment capacity of each control unit:

[0134]

[0135] Where M i represents the water environment capacity of river section i, kg / d;

[0136] Q i-1 represents the flow from the previous river section into river section i, m 3 / s;

[0137] q i represents the flow rate of the interval into the river section i, m 3 / s;

[0138] C i-1 and C i Respectively represent the pollutant concentrations at the beginning and end of river section i, mg / L;

[0139] x i represents the length of river section i, m;

[0140] u i Represents the average flow velocity of river section i, m / s.

[0141] 3) Add up the water environment capacity of all control units to obtain the water environment capacity M of the entire river:

[0142]

[0143] In the formula, C s Indicates the water quality target at the outlet of the last river section, mg / L.

[0144] (4) Establish an indicator system that can reflect the fairness of water environment capacity allocation in the control unit and calculate the Gini coefficient;

[0145] 1) Population and farmland area are selected as indicators to reflect the fairness of water environment capacity allocation in control units.

[0146] Table 1 Gini coefficient evaluation index of each control unit in the basin

[0147]

[0148]

[0149] 2) Calculate the Gini coefficient of each indicator as follows:

[0150]

[0151] In the formula, i is the partition number of each control unit;

[0152] j is the number of the evaluation index;

[0153] Gj is the Gini coefficient of indicator j;

[0154] X i,j is the cumulative proportion of index j of the i-th control unit;

[0155] Y i The cumulative proportion of water environment capacity allocated to the ith control unit;

[0156] When i=1, X (i-1),j =0, Y i-1 =0.

[0157] 3) Calculate the weight of each indicator and add them together to get the comprehensive Gini coefficient G.

[0158]

[0159] In the formula, G represents the comprehensive Gini coefficient, α j represents the weight of indicator j.

[0160] (5) A multi-objective optimization model is constructed, with the maximum sum of the water environment capacity of each control unit and the minimum Gini coefficient as the optimization objectives, to obtain the final allocated water environment capacity of each control unit.

[0161] 1) Taking the maximum sum of the water environment capacity of each control unit in the step and the minimum Gini coefficient as the optimization goal, the objective function is established:

[0162]

[0163] 2) Determine the constraints based on the river assessment target. The water quality assessment target at the end of the river is surface water Class III, and the pollutant concentration at the end should not be higher than the assessment target concentration:

[0164] C 12 ≤C s

[0165] Where:

[0166] C 12 It represents the pollutant concentration at the end of the river section, mg / L;

[0167] C s It is the assessment target concentration of the corresponding control section, mg / L.

[0168] 3) The pollutant concentration C at the end of river section i i As decision variables, a multi-objective optimization algorithm is used to solve the optimal solution set. This implementation example takes chemical oxygen demand (COD) as an example. Figure 2As shown in the figure, the optimal solution set of COD is obtained by multi-objective optimization. In this figure, each point represents a possible solution, and the scattered distribution in the figure reflects the trade-off between the comprehensive Gini coefficient and the water environment capacity.

[0169] 4) According to the optimal solution set required, the decision maker can select a suitable optimal solution. In this embodiment, the decision maker selects Figure 2 The middle inflection point is taken as the optimal solution, that is, the comprehensive Gini coefficient at this point is 0.2, and the sum of the water environment capacity is 680. According to the above optimal solution, the water environment capacity of each control unit can be calculated. The distribution results of the water environment capacity of each control unit are as follows: Figure 2 shown.

[0170] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for allocating water environment capacity of a watershed based on a control unit, characterized in that: The following steps are involved: Construct hydrological and hydrodynamic models and river water quality models based on the hydrological information of the target watershed; Determining the hydrological conditions of each control unit in the target watershed according to the hydrological and hydrodynamic model; Determining the calculation standard of water environment capacity under the hydrological conditions according to the river water quality model; A multi-objective optimization model is constructed according to the water environment capacity assessment standard and the water environment capacity calculation standard, and the water environment capacity allocated to each control unit under the hydrological conditions is determined according to the multi-objective optimization model.

2. The method for allocating water environment capacity of a watershed according to claim 1, characterized in that: The calculation standard of water environment capacity under the hydrological conditions is determined according to the river water quality model, specifically including: Determine the calculation criteria of water environment capacity of each control unit under the hydrological conditions according to the river water quality model; The water environment capacity calculation standard of the target area under the hydrological conditions is constructed according to the water environment capacity calculation criteria of each control unit under the hydrological conditions.

3. The method for allocating water environment capacity of a watershed according to claim 1, characterized in that: Before constructing the multi-objective optimization model according to the water environment capacity assessment standard and the water environment capacity calculation standard, it also includes: Establish water environment capacity assessment standards that reflect the preset characteristics of water environment capacity allocation.

4. The method for allocating water environment capacity of a watershed according to claim 3 is characterized in that: The preset characteristics are fair characteristics. The water environment capacity assessment standard reflecting the preset characteristics of water environment capacity allocation is established, including: Selecting an indicator system that meets the fairness characteristics; The Gini coefficient of each indicator in the indicator system is calculated, and the comprehensive Gini coefficient of the indicator system is determined according to the weight of each indicator, and the comprehensive Gini coefficient is used as the water capacity assessment standard.

5. The method for allocating water environment capacity of a watershed according to claim 4 is characterized in that: The indicators are population, water resources, farmland area, industrial water consumption, domestic water consumption, wastewater discharge or water quality compliance rate.

6. The method for allocating water environment capacity of a river basin according to claim 4 is characterized in that: The objective function of the multi-objective optimization model is: The sum of the water environment capacities of the control units is the largest; The comprehensive Gini coefficient is the smallest.

7. The method for allocating water environment capacity of a watershed according to claim 1, characterized in that: The constraints of the multi-objective optimization model are: The pollutant concentration of any control section in the target watershed meets its corresponding preset requirements.

8. The method for allocating water environment capacity of a watershed according to claim 7 is characterized in that: Determining the water environment capacity allocated to each control unit under the hydrological conditions according to the multi-objective optimization model specifically includes: Obtaining a solution result of the multi-objective optimization model under the hydrological conditions; The water environment capacity allocated to each control unit under the hydrological conditions is determined according to the solution result and the water environment capacity calculation standard.

9. The method for allocating water environment capacity of a watershed according to claim 1, characterized in that: The hydrological conditions are static design hydrological conditions or dynamic design hydrological conditions.

10. The method for allocating water environment capacity of a river basin according to claim 1, characterized in that: Building a hydrological and hydrodynamic model also includes: The hydrological and hydrodynamic model is calibrated and verified based on the measured hydrological data of the target watershed.

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