Non-point source pollutant river entry coefficient solving method and system based on distance correction coefficient

Abstract

The invention discloses a distance correction coefficient-based non-point source pollutant river-entering coefficient solving method and system, and the key points of the technical scheme are that the method comprises the steps: determining a non-point source pollutant river-entering distance correction coefficient based on the length of a branch flow and a main flow which are converged into a grid point where a pollution source is located, and calculating the river-entering coefficient of the non-point source pollutant in combination with a terrain correction coefficient; the method specifically comprises the following steps of S1, S2, S3 and S4. According to the distance correction coefficient-based non-point source pollutant river entry coefficient solving method provided by the invention, the river entry coefficient is calculated and valued according to the length from the position of the grid point to the downstream of the main stream, so that the method has certain superiority in space; the slope difference of the terrain, pollutant degradation of the spatial distance and other aspects are combined for quantitative consideration, and the value of the in-river coefficient is more accurate.

Description

Technical Field

[0001] The present invention relates to the field of environmental protection technology, and in particular to a method and system for obtaining a coefficient of non-point source pollutants entering a river based on a distance correction coefficient. Background Art

[0002] Non-point source pollution is an important environmental problem facing my country. As one of the main sources of river basin pollution, it has a wide impact range and is difficult to control. Therefore, it has attracted increasing attention from researchers and managers. The non-point source pollution inflow coefficient is directly related to the route distance of the pollution source into the polluted river.

[0003] Among them, non-point source pollution mainly includes agricultural source pollution (farmland, livestock and poultry, aquaculture), life source pollution (rural life source, urban life source) and urban surface runoff source pollution. Non-point source pollutants are affected by multiple factors from generation to entering the river, such as rainfall, surface runoff, underlying surface characteristics and human activities. They are closely related to the runoff and biochemical processes related to the production, migration and transformation of nutrients in the water body. Rainfall produces runoff under different underlying surfaces and erodes the soil. Under the action of rainfall-runoff driving factors, a large amount of sediment and attached and soluble pollutants enter the water body. At the same time, pollutants in the soil migrate vertically with precipitation infiltration. Adsorbed and dissolved pollutants in the water undergo adsorption-desorption, plant interception, microbial degradation, etc., and eventually enter the water body and affect the water environment. Therefore, the accurate measurement of the pollutant inflow coefficient is of great practical significance for evaluating the water environment quality and the amount of pollutants entering the river.

[0004] At present, there are many methods and models for simulating and estimating non-point source pollution in watersheds. Among them, lumped and distributed non-point source pollution models are widely used. Lumped models include pollution partitioning method, average concentration method, output coefficient method and rainfall difference method, which are widely used. Distributed hydrological models mainly focus on the hydrological cycle process. Since the 1990s, due to the urgent need for global climate change and sustainable development of water resources cycle, distributed hydrological models have gradually attracted the interest of scientific researchers and have made significant progress in theory, technology and modeling ideas. As a result, some well-known distributed hydrological models have emerged, such as ANSWERS, BASINS, SWAT, GLEAMS, AnnAGNPS, etc. These models have been widely used in practical problems. However, these methods often have insufficient accuracy in calculating the coefficient of non-point source pollutants entering the river, and cannot fully consider the spatial differences in pollutants generated in different sub-basins and the influence of factors such as terrain, vegetation, and soil on the coefficient of entering the river.

[0005] Therefore, a method and system for calculating the coefficient of non-point source pollutants entering the river based on the distance correction coefficient is proposed. Summary of the invention

[0006] In response to the problems mentioned in the background technology, the purpose of the present invention is to provide a method for calculating the non-point source pollutant entry coefficient based on a distance correction coefficient, which is used to accurately evaluate the amount and impact range of non-point source pollutants entering the river, and provide a scientific basis for river basin water environment management and pollution control, so as to solve the problem that the existing technology often has insufficient accuracy in the calculation of non-point source pollutant entry coefficients, and cannot fully consider the spatial differences in pollutants generated by different sub-basins and the impact of factors such as terrain, vegetation, and soil on the river entry coefficient.

[0007] The above technical objectives of the present invention are achieved through the following technical solutions:

[0008] A method for calculating the coefficient of non-point source pollutants entering a river based on a distance correction coefficient. The method determines the distance correction coefficient of non-point source pollutants entering a river based on the length of the grid point where the pollution source is located into the tributary and the main stream, and combines the terrain correction coefficient to achieve the calculation of the coefficient of pollutants entering a river. The method specifically includes the following steps:

[0009] S1. Watershed division and coding:

[0010] Divide the study area where the non-point source pollution is to be calculated into watersheds and encode the watersheds where each non-point source is located;

[0011] The coordinates of each area source grid point in the study area were extracted using ArcGIS geographic information system software;

[0012] S2. Distance calculation:

[0013] Select the pollutant inlet of the polluted river and the coordinates of each grid point on each level of tributaries for calculating the amount of pollutants entering the river;

[0014] Calculate the distance from the grid points in each watershed area source to the grid points of each level of tributaries, and the distance from the grid points of each level of tributaries to the grid points of the previous level of tributaries, until they converge into the confluence of the polluted river;

[0015] Add up the above distances to get the total distance that the surface source grid points flow into the polluted river.

[0016] S3. Calculation of terrain correction coefficient:

[0017] The terrain slope of each divided watershed is calculated and extracted through ArcGIS geographic information system software;

[0018] Determine the terrain correction coefficient according to the terrain slope at the location of the area source grid point;

[0019] S4. Calculation of river entry coefficient:

[0020] The river entry coefficient of non-point source pollutants is calculated based on the distance correction coefficient, terrain correction coefficient and other relevant parameters determined by the total distance that the non-point source grid points flow into the polluted river.

[0021] The above-mentioned method for obtaining the coefficient of non-point source pollutants entering a river based on the distance correction coefficient, wherein: the other relevant parameters in step S4 at least include the comprehensive attenuation coefficient of non-point source pollutants and the average flow velocity of non-point sources entering the polluted river.

[0022] The above method for obtaining the coefficient of non-point source pollutants entering the river based on the distance correction coefficient, wherein: the specific scheme of step S2 is as follows:

[0023] The tributaries at each level in step S2 are numbered sequentially as the first-level tributary, the second-level tributary, and so on to the n-th-level tributary, where n is an integer greater than or equal to 1;

[0024] Calculate the distance Ln from each basin surface source grid point to the nth level tributary grid point, and the distance Ln from the nth level tributary grid point to the n-1th level tributary grid point. n-1 , the distance L from the grid point of the n-1th level tributary to the grid point of the n-2th level tributary n-2 , ..., the distance L1 from the grid point of the second-level tributary to the grid point of the first-level tributary, and the distance L0 from the grid point of the first-level tributary to the confluence of the river to be calculated;

[0025] Cumulative distance L n + L n-1 + L n-2 + … + L1+ L0 = L, where L is the total distance that the surface source grid points flow into the polluted river for calculation.

[0026] The above method for obtaining the coefficient of non-point source pollutants entering the river based on the distance correction coefficient, wherein: the specific scheme of step S3 is as follows:

[0027] ArcGIS geographic information system software is used to calculate and extract the terrain slope i of each divided basin, and determine the terrain correction coefficient of the surface source grid point entering the polluted river , revised L.

[0028] The above method for calculating the coefficient of non-point source pollutants entering the river based on the distance correction coefficient, where the calculation formula of the coefficient of non-point source pollutants entering the river is as follows:

[0029] Where: ——The amount of all pollutants entering the river (t / a); ——Amount of various pollutants generated; ——Correction factor for distance into river; ——River inlet terrain correction coefficient, the value is 1 / cosi; ——The distance (m) that the surface source grid points flow through when calculating the polluted river, L= L n +L n-1 +…+ L1+ L0, where L n is the distance from each watershed surface source grid point to the nth-level tributary grid point, L n-1 is the distance from the grid point of the n-th tributary to the grid point of the n-1-th tributary, ..., L1 is the distance from the grid point of the second-level tributary to the grid point of the first-level tributary, and L0 is the distance from the grid point of the first-level tributary to the confluence of the river to be calculated; , ——respectively represent the minimum distance (m) and maximum inflow coefficient (dimensionless) of all surface source grid points to be calculated, where = , k is the comprehensive attenuation coefficient of non-point source pollutants (s -1 ), u is the average flow velocity of the non-point source into the polluted river (m / s), no data for the area The value is 0.8~1.0; , ——respectively represent the maximum distance (m) and minimum inflow coefficient (dimensionless) of all surface source grid points to be calculated, where = , No data area The value is 0~0.2. >L0 Take 0; L0 is the distance from a certain non-point source grid point pollutant to the polluted river where the pollutant inflow is to be calculated through one-dimensional steady-state calculation when the increment is degraded to 0; ——is the slope of the watershed where the surface source grid point is located.

[0030] The above-mentioned method for calculating the river entry coefficient of non-point source pollutants based on the distance correction coefficient, wherein: the method is used to calculate the river entry coefficients of various non-point source pollution types such as agricultural source pollution, domestic source pollution and urban surface runoff source pollution.

[0031] The above-mentioned method for calculating the coefficient of non-point source pollutants entering the river based on the distance correction coefficient, wherein: the sub-basin division is performed by ArcSWAT software.

[0032] The present invention also provides a system for implementing the method for obtaining the coefficient of non-point source pollutants entering a river based on the distance correction coefficient, comprising:

[0033] The watershed division module is used to divide the study area into sub-watersheds;

[0034] The coding and coordinate extraction module is used to encode the watershed where the area source is located and extract the coordinates of the area source grid points;

[0035] The distance calculation module is used to calculate the distance from the surface source grid point to the grid points of tributaries at all levels and accumulate the total distance;

[0036] A terrain correction coefficient calculation module is used to calculate the terrain correction coefficient;

[0037] The river entry coefficient calculation module is used to calculate the river entry coefficient of non-point source pollutants by combining the distance correction coefficient and the terrain correction coefficient obtained based on the total distance.

[0038] The above system, among others, also includes a one-dimensional steady-state river calculation module, which is used to determine the distance L0 from a certain surface source grid point pollutant to the polluted river where the pollutant inflow to be calculated is degraded to 0.

[0039] In summary, the present invention mainly has the following beneficial effects:

[0040] 1. Spatial superiority: The traditional river inflow coefficient is generally the average value of the river inflow coefficient of the basin or the ratio between the pollutant flux and the pollutant generation of the receiving water body of the basin, which cannot reflect the spatial differences in pollutant generation in different sub-basins. The present invention calculates and values ​​the river inflow coefficient based on the distance from the grid point to the downstream of the mainstream, which has certain spatial superiority.

[0041] 2. Accuracy: The river entry coefficient is correlated with topography, vegetation, soil and distance. The present invention takes into quantitative consideration various aspects such as the slope difference of the terrain and the degradation of pollutants at spatial distance, so that the river entry coefficient is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic diagram of watershed coding in the method for obtaining the coefficient of non-point source pollutants entering a river based on the distance correction coefficient of the present invention;

[0043] Figure 2 It is a schematic diagram of a watershed calculation method in a method for obtaining a non-point source pollutant entering a river based on a distance correction coefficient according to the present invention. DETAILED DESCRIPTION

[0044] 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.

[0045] refer to Figure 1-Figure 2This embodiment provides a method for calculating the coefficient of non-point source pollutants entering a river based on a distance correction coefficient. The method determines the distance correction coefficient of non-point source pollutants entering a river based on the length of the grid point where the pollution source is located and the length of the tributary and main stream, and combines the terrain correction coefficient to achieve the calculation of the coefficient of pollutants entering a river. The method specifically includes the following steps:

[0046] S1. Watershed division and coding:

[0047] Divide the study area where the non-point source pollution is to be calculated into watersheds and encode the watersheds where each non-point source is located;

[0048] The coordinates of each area source grid point in the study area were extracted using ArcGIS geographic information system software;

[0049] S2. Distance calculation:

[0050] Select the pollutant inlet of the polluted river and the coordinates of each grid point on each level of tributaries for calculating the amount of pollutants entering the river;

[0051] Calculate the distance from each watershed surface source grid point to each level of tributary grid points, and the distance from each level of tributary grid points to the previous level of tributary grid points, until they converge into the confluence of the polluted river;

[0052] Add up the above distances to get the total distance that the surface source grid points flow into the polluted river.

[0053] S3. Calculation of terrain correction coefficient:

[0054] The terrain slope of each divided watershed is calculated and extracted through ArcGIS geographic information system software;

[0055] Determine the terrain correction coefficient according to the terrain slope at the location of the area source grid point;

[0056] S4. Calculation of river entry coefficient:

[0057] The river entry coefficient of non-point source pollutants is calculated based on the total distance that the non-point source grid points flow into the polluted river, the terrain correction coefficient and other relevant parameters.

[0058] Among them: the other relevant parameters in step S4 at least include the comprehensive attenuation coefficient of non-point source pollutants and the average flow velocity of non-point sources entering the polluted river.

[0059] Wherein: the specific scheme of step S2 is as follows:

[0060] The tributaries at each level in step S2 are numbered sequentially as the first-level tributary, the second-level tributary, and so on to the n-th-level tributary, where n is an integer greater than or equal to 1;

[0061] Calculate the distance Ln from each basin surface source grid point to the nth level tributary grid point, and the distance Ln from the nth level tributary grid point to the n-1th level tributary grid point. n-1 , the distance L from the grid point of the n-1th level tributary to the grid point of the n-2th level tributary n-2 , ..., the distance L1 from the grid point of the second-level tributary to the grid point of the first-level tributary, and the distance L0 from the grid point of the first-level tributary to the confluence of the river to be calculated;

[0062] Cumulative distance L n + L n-1 + L n-2 + … + L1+ L0 = L, where L is the total distance that the surface source grid points flow into the polluted river for calculation.

[0063] Wherein: the specific scheme of step S3 is as follows:

[0064] ArcGIS geographic information system software is used to calculate and extract the terrain slope i of each divided basin, and determine the terrain correction coefficient of the surface source grid point entering the polluted river , revised L.

[0065] Among them: the method is used to calculate the river entry coefficients of various non-point source pollution types, including agricultural source pollution, domestic source pollution, and urban surface runoff source pollution.

[0066] Among them: the watershed division is carried out through ArcSWAT software.

[0067] The present invention also provides a system for implementing the above-mentioned method for obtaining the non-point source pollutant entering the river coefficient based on the distance correction coefficient, comprising a watershed division module, a coding and coordinate extraction module, a distance calculation module, a terrain correction coefficient calculation module, a river entering coefficient calculation module and a river one-dimensional steady-state calculation module, wherein:

[0068] The watershed division module is used to divide the study area into sub-watersheds;

[0069] The encoding and coordinate extraction module is used to encode the watershed where the area source is located and extract the coordinates of the area source grid points;

[0070] The distance calculation module is used to calculate the distance from the surface source grid point to the grid points of each level of tributaries and accumulate the total distance;

[0071] The terrain correction coefficient calculation module is used to calculate the terrain correction coefficient;

[0072] The river entry coefficient calculation module is used to calculate the river entry coefficient of non-point source pollutants by combining the total distance and terrain correction coefficient.

[0073] The one-dimensional steady-state calculation module of the river is used to determine the distance L0 from a certain surface source grid point pollutant to the polluted river where the pollutant inflow to be calculated is degraded to 0.

[0074] Specifically, in this embodiment, a method for calculating the coefficient of non-point source pollutants entering the river based on the distance correction coefficient is applied by taking a certain river as an example: after dividing the river into basins through ArcSWAT, encode each sub-basin, and number the basins in sequence from the upstream of the river mainstream to the downstream estuary. The codes of all basins in the mainstream are 001, 002, ..., xyz from top to bottom, and the uppermost first-level sub-basin is coded as 001 001, 001 002, ..., 001 xyz. The uppermost second-level sub-basin of the first-level sub-basin is coded as 001 001 001, 001 001 002, ..., 001 001 xyz, where x, y, z = 1, 2, .... For example, the mainstream is the polluted river for which the amount of non-point source pollutants entering the river is to be calculated. The watershed number of the third inflow point on the first-level tributary corresponding to the third inflow point of the mainstream is 003 003, and the watershed numbers of its second-level tributaries are 003 003 001 and 003 003 002 respectively.

[0075] by Figure 2 Taking the example of the method, the X, Y coordinates of each non-point source grid point in the study area where non-point source pollution is to be calculated are extracted through ArcGIS (the extraction format is WGS-1984-UTM coordinates), and the coordinates of the non-point source grid point where any point (point B) of the secondary tributary converges to the first-level tributary (point C) and the pollutant inlet (point D) of the polluted river where the amount of pollutants entering the river is to be calculated are selected. The distance from the non-point source grid point A to the pollutant inlet (point D) of the polluted river is calculated, which is recorded as:

[0076] Through the one-dimensional steady-state calculation of the river, the distance at which the pollutant at the surface source grid point A enters the polluted river where the pollutant inflow is to be calculated is degraded to 0, which is recorded as L0. Then the correction coefficient of the inflow distance is calculated. .

[0077] The slope i of the study area is calculated and extracted, and then the terrain correction coefficient is taken according to the location of the non-point source grid point, so as to realize the calculation of the non-point source pollutant entering the river coefficient based on the distance correction coefficient.

[0078] The calculation formula for the pollutant inflow coefficient is as follows:

[0079] Where: ——The amount of all pollutants entering the river (t / a); ——Amount of various pollutants generated; ——Correction factor for distance into river; ——River inlet terrain correction coefficient, the value is 1 / cosi; ——The distance (m) that the surface source grid points flow through when calculating the polluted river, L= L n +L n-1 +…+ L1+ L0, where L n is the distance from each watershed surface source grid point to the nth-level tributary grid point, L n-1 is the distance from the grid point of the n-th tributary to the grid point of the n-1-th tributary, ..., L1 is the distance from the grid point of the second-level tributary to the grid point of the first-level tributary, and L0 is the distance from the grid point of the first-level tributary to the confluence of the river to be calculated; , ——respectively represent the minimum distance (m) and maximum inflow coefficient (dimensionless) of all surface source grid points to be calculated, where = , k is the comprehensive attenuation coefficient of non-point source pollutants (s -1 ), u is the average flow velocity of the non-point source into the polluted river (m / s), no data for the area The value is 0.8~1.0; , ——respectively represent the maximum distance (m) and minimum inflow coefficient (dimensionless) of all surface source grid points to be calculated, where = , No data area The value is 0~0.2. >L0 Take 0; L0 is the distance from a certain non-point source grid point pollutant to the polluted river where the pollutant inflow is to be calculated through one-dimensional steady-state calculation when the increment is degraded to 0; ——is the slope of the watershed where the surface source grid point is located.

[0080] In summary:

[0081] (1) The traditional river inflow coefficient is generally the average value of the river inflow coefficient of the basin or the ratio between the pollutant flux and the pollutant generation in the receiving water body of the basin, which cannot reflect the spatial differences in pollutant generation in different sub-basins. The method for calculating the river inflow coefficient of non-point source pollutants based on the distance correction coefficient provided in this application calculates and determines the river inflow coefficient based on the distance from the grid point to the downstream of the mainstream, which has certain advantages in space.

[0082] (2) The river entry coefficient is related to topography, vegetation, soil and distance. The river entry coefficient of non-point source pollutants in this application is quantitatively considered in combination with various aspects such as the slope difference of the terrain and the degradation of pollutants over spatial distance. The river entry coefficient is more accurate.

[0083] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for calculating the coefficient of non-point source pollutants entering a river based on a distance correction coefficient, characterized in that: The method determines the correction coefficient of the distance of non-point source pollutants entering the river based on the length of the grid point where the pollution source is located and the tributary and main stream, and combines the terrain correction coefficient to calculate the coefficient of pollutants entering the river. The method specifically includes the following steps: S1. Watershed division and coding: Divide the study area where the nonpoint source pollution is to be calculated into sub-basins and code the basins where each nonpoint source is located; The coordinates of each area source grid point in the study area were extracted using ArcGIS geographic information system software; S2. Distance calculation: Select the pollutant inlet of the polluted river and the coordinates of each grid point on each level of tributaries for calculating the amount of pollutants entering the river; Calculate the distance from the grid points of the surface source to the grid points of each level of tributaries in each watershed, and the distance from the grid points of each level of tributaries to the grid points of the previous level of tributaries, until they converge into the confluence of the polluted river; Add up the above distances to get the total distance that the surface source grid points flow into the polluted river. S3. Calculation of terrain correction coefficient: The terrain slope of each divided watershed is calculated and extracted through ArcGIS geographic information system software; Determine the terrain correction coefficient according to the terrain slope at the location of the area source grid point; S4. Calculation of river entry coefficient: The river entry coefficient of non-point source pollutants is calculated based on the total distance that the non-point source grid points flow into the polluted river, the terrain correction coefficient and other relevant parameters.

2. The method for obtaining the coefficient of non-point source pollutants entering a river based on a distance correction coefficient according to claim 1, characterized in that: Other relevant parameters in step S4 include at least the comprehensive attenuation coefficient of non-point source pollutants and the average flow velocity of non-point sources entering the polluted river.

3. The method for obtaining the coefficient of non-point source pollutants entering a river based on a distance correction coefficient according to claim 1, characterized in that: The specific scheme of step S2 is as follows: The tributaries at each level in step S2 are numbered sequentially as the first-level tributary, the second-level tributary, and so on to the n-th-level tributary, where n is an integer greater than or equal to 1; Calculate the distance L between each watershed surface source grid point and the nth-level tributary grid point n , the distance L from the nth level tributary grid point to the n-1th level tributary grid point n-1 , the distance L from the grid point of the n-1th level tributary to the grid point of the n-2th level tributary n-2 , ..., the distance L1 from the grid point of the second-level tributary to the grid point of the first-level tributary, and the distance L0 from the grid point of the first-level tributary to the confluence of the river to be calculated; Cumulative distance L n + L n-1 + L n-2 + … + L1+ L0 = L, where L is the total distance that the surface source grid points flow into the polluted river for calculation.

4. The method for obtaining the coefficient of non-point source pollutants entering a river based on a distance correction coefficient according to claim 3, characterized in that: The specific scheme of step S3 is as follows: ArcGIS geographic information system software is used to calculate and extract the terrain slope i of each divided basin, and determine the terrain correction coefficient of the surface source grid point entering the polluted river , revised L.

5. The method for obtaining the coefficient of non-point source pollutants entering a river based on a distance correction coefficient according to claim 4, characterized in that: The calculation formula for the coefficient of non-point source pollutants entering the river is as follows: Where: ——The amount of all pollutants entering the river (t / a); ——Amount of various pollutants generated; ——Correction factor for distance into river; ——River inlet terrain correction coefficient, the value is 1 / cosi; ——The distance (m) that the surface source grid points flow through when calculating the polluted river, L= L n +L n-1 +…+ L1+ L0, where L n is the distance from each watershed surface source grid point to the nth-level tributary grid point, L n-1 is the distance from the grid point of the n-th tributary to the grid point of the n-1-th tributary, ..., L1 is the distance from the grid point of the second-level tributary to the grid point of the first-level tributary, and L0 is the distance from the grid point of the first-level tributary to the confluence of the river to be calculated; , ——respectively represent the minimum distance (m) and maximum inflow coefficient (dimensionless) of all surface source grid points to be calculated, where = , k is the comprehensive attenuation coefficient of non-point source pollutants (s -1 ), u is the average flow velocity of the non-point source into the polluted river (m / s), no data for the area The value is 0.8~1.0; , ——respectively represent the maximum distance (m) and minimum inflow coefficient (dimensionless) of all surface source grid points to be calculated, where = , No data area According to the value of 0~0.2, if >L0 Take 0; L0 is the distance from a certain non-point source grid point to the polluted river where the pollutant inflow is to be calculated through one-dimensional steady-state calculation, when the increment is reduced to 0; ——is the slope of the watershed where the surface source grid point is located.

6. The method for obtaining the coefficient of non-point source pollutants entering a river based on a distance correction coefficient according to claim 5, characterized in that: The method is used to obtain river entry coefficients of various non-point source pollution types, including agricultural source pollution, domestic source pollution and urban surface runoff source pollution.

7. The method for obtaining the coefficient of non-point source pollutants entering a river based on a distance correction coefficient according to claim 6, characterized in that: The sub-basin division is performed by ArcSWAT software.

8. A system for implementing the method for obtaining the coefficient of non-point source pollutants entering a river based on the distance correction coefficient as described in claim 1, characterized in that: include: The watershed division module is used to divide the study area into sub-watersheds; The coding and coordinate extraction module is used to encode the watershed where the area source is located and extract the coordinates of the area source grid points; The distance calculation module is used to calculate the distance from the surface source grid point to the grid points of each level of tributaries and accumulate the total distance; A terrain correction coefficient calculation module is used to calculate the terrain correction coefficient; The river entry coefficient calculation module is used to calculate the river entry coefficient of non-point source pollutants by combining the distance correction coefficient and the terrain correction coefficient obtained based on the total distance.

9. The system according to claim 8, characterized in that: It also includes a one-dimensional steady-state river calculation module for determining the distance L0 from a certain surface source grid point pollutant to the polluted river where the pollutant inflow to the river is to be calculated and then degraded to 0.

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