A method for assessing the impact of pollution on rivers entering a lake based on mathematical models

Abstract

The invention discloses a method for evaluating the impact of pollution of rivers entering a lake based on a mathematical model, including: extracting the pollutant concentration of rivers monitored on rainy days based on water quality monitoring data, and obtaining a rainfall and pollutant concentration curve using a regression analysis method; obtaining water quality monitoring data not monitored on rainy days based on the rainfall and pollutant concentration curve, and calculating the excess rate of pollutant concentration in rivers throughout the year; constructing a hydrodynamic water quality model of the target lake based on the hydrological data and meteorological data of the target lake; and calculating the impact of changes in the pollution concentration of rivers entering the lake on the pollutant concentration of the entire lake based on the hydrodynamic water quality model of the target lake. The method can make up for the lack of monitoring time and comprehensively judge the pollution impact of rivers entering the lake in different hydrological periods and geographical locations.

Description

Technical Field

[0001] The invention relates to a method for evaluating the pollution impact degree of rivers entering a lake based on a mathematical model, and belongs to the technical field of regional water environment management. Background Art

[0002] Rivers, as a special body of water, connect substances and the environment between water bodies and are very important transmission paths. Among them, rivers entering lakes have more important functions. Severe pollution in rivers can significantly deteriorate the overall ecological environment of lakes. Rainfall has two effects: erosion and dilution. Erosion can cause pollutants to leave their original locations and flow into water bodies with runoff, while dilution can reduce the concentration of pollutants in water bodies. The different magnitudes of these two forces can cause the concentration of pollutants in water bodies to increase or decrease.

[0003] However, field monitoring has its time limitations, and the peak concentration of pollutants caused by rainfall may not be monitored, resulting in certain limitations in river pollution assessment. Secondly, for lakes with large areas and complex river networks, the weight of the impact of rivers entering the lake in different hydrological periods and geographical locations on the lake water quality varies. It is necessary to comprehensively evaluate the rivers entering the lake and the degree of impact based on the above two points. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for evaluating the impact of rivers entering the lake based on a mathematical model, which can make up for the lack of monitoring time and comprehensively judge the pollution impact of rivers entering the lake in different hydrological periods and geographical locations. To achieve the above purpose, the present invention is implemented by the following technical solutions:

[0005] The present invention provides a method for evaluating the impact of rivers entering a lake based on a mathematical model, comprising:

[0006] Obtain hydrological data of the target lake, meteorological data of the target lake location, and water quality monitoring data of the river;

[0007] Based on the water quality monitoring data, the pollutant concentrations of rivers monitored on rainy days were extracted, and the rainfall and pollutant concentration curves were obtained using regression analysis.

[0008] Based on the rainfall and pollutant concentration curves, the water quality monitoring data not monitored on rainy days are obtained, and the excess rate of river pollutant concentration throughout the year is calculated;

[0009] Based on the hydrological and meteorological data of the target lake, a hydrodynamic and water quality model of the target lake is constructed;

[0010] Based on the hydrodynamic water quality model of the target lake, the impact of changes in pollution concentrations in rivers entering the lake on the pollutant concentrations in the entire lake is calculated.

[0011] Preferably, the pollutants include at least: permanganate index, COD, ammonia nitrogen, total nitrogen, and total phosphorus.

[0012] Further, obtaining the rainfall and pollutant concentration curves includes:

[0013] Determine the rainfall level based on the rainfall amount.

[0014] Filter the function used in the regression analysis for each rainfall class;

[0015] The regression analysis results R 2 Based on the maximum, determine the type and coefficient of the function used in regression analysis;

[0016] Based on the function of the fitting curve, the rainfall and pollutant concentration curves are obtained.

[0017] Furthermore, the functions used in the regression analysis method include: y=A×exp(B×x) function, y=Ax 2 +Bx+C or y=A×lnx+B function.

[0018] Preferably, the rainfall level is:

[0019] Level 1: 24-hour rainfall is less than 10 mm,

[0020] Level 2: 24-hour rainfall 10-25 mm,

[0021] Level 3: 24-hour rainfall 25-50 mm,

[0022] Level 4: 24-hour rainfall 50-100 mm,

[0023] Level 5: 24-hour rainfall 100-250 mm,

[0024] Level 6: 24-hour rainfall is greater than 250 mm.

[0025] Furthermore, the calculation formula of the excess rate is:

[0026]

[0027] In formula (1), X i represents the number of days when the pollutant concentration of the ith river exceeds the standard, and D represents the total number of days in a year.

[0028] Furthermore, constructing a hydrodynamic water quality model of the target lake includes:

[0029] Based on the water depth of the target lake, a coordinate system is selected and the target lake is divided into n layers vertically;

[0030] Based on the hydrological and meteorological data of the target lake, the initial conditions and boundary conditions of the hydrodynamic and water quality model are set to construct the initial hydrodynamic and water quality model;

[0031] The parameters of the initial hydrodynamic and water quality model are calibrated and verified to obtain the hydrodynamic and water quality model of the target lake.

[0032] Preferably, the method further includes dividing the target lake into grids to obtain a plurality of computational grids; dividing the target lake into n layers vertically in each computational grid and constructing a hydrodynamic and water quality model.

[0033] Further, the selected coordinate system is SIG coordinates or SGZ coordinates;

[0034] When selecting SGZ coordinates, the minimum number of layers n0 in the target lake layer is ≥ 1, and satisfies:

[0035]

[0036] In formula (2), H0 represents the minimum water depth of the target lake; H1 represents the maximum water depth of the target lake; n represents the number of layers; m represents the recommended range for achieving the calculation effect, where the calculation effect is the relative error between the calculation result of the hydrodynamic water quality model and the true value, and the recommended range represents the range in which the calculation time and relative error are balanced.

[0037] Preferably, as the minimum number of layers n0 increases, the relative error decreases and the calculation time increases.

[0038] Preferably, when the SIG coordinates are selected, the number of layers of each computational grid division in the hydrodynamic and water quality model is consistent.

[0039] Furthermore, the initial conditions of the hydrodynamic water quality model include: underwater topography, water depth, water surface elevation, atmospheric pressure, humidity, wind speed, wind direction, water surface shortwave radiation, precipitation and cloud layer.

[0040] Furthermore, the boundary conditions of the hydrodynamic water quality model include: inflow and outflow of the lake, water level, water temperature of each of the n layers, and pollutant concentration.

[0041] Furthermore, the calculation formula for the degree of influence is:

[0042]

[0043] In formula (3), θ i represents the disturbed input river pollutant concentration; y j represents the output variable after the boundary condition perturbation; y0 represents the output obtained by the reference boundary condition; δθ i represents the change of the i-th boundary condition; E[|y j -y0|] represents the average of the total deviations.

[0044] Furthermore, the disturbance of the boundary condition is an increase or decrease of 10% to 40% in the pollution load of the rivers entering the lake.

[0045] Compared with the prior art, the method for evaluating the impact of rivers entering a lake based on a mathematical model provided by the embodiment of the present invention has the following beneficial effects:

[0046] The present invention extracts the pollutant concentration of the river monitored on rainy days based on the water quality monitoring data, and obtains the rainfall and pollutant concentration curve by using the regression analysis method; according to the rainfall and pollutant concentration curve, the water quality monitoring data not monitored on rainy days is obtained, and the excess rate of pollutant concentration in the river throughout the year is calculated; the present invention can make up for the shortage of monitoring time;

[0047] The present invention constructs a hydrodynamic water quality model of the target lake based on the hydrological data and meteorological data of the target lake; based on the hydrodynamic water quality model of the target lake, calculates the degree of influence of changes in the pollution concentration of rivers entering the lake on the pollutant concentration of the entire lake; the present invention can comprehensively judge the degree of pollution influence of rivers entering the lake in different hydrological periods and geographical locations

[0048] The invention is easy to operate and apply, is beneficial to the ecological environment protection of rivers and lakes, and has significant economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 is a flow chart of a method for evaluating the impact of rivers entering a lake based on a mathematical model provided in Example 1 of the present invention;

[0050] Figure 2 This is the pollutant concentration distribution diagram of river X1 throughout the year in Example 2 of the present invention;

[0051] Figure 3 This is a result diagram of the impact degree of pollution of rivers entering the lake in Example 2 of the present invention. DETAILED DESCRIPTION

[0052] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0053] Embodiment 1:

[0054] like Figure 1 As shown in the figure, a method for assessing the impact of pollution of rivers entering a lake based on a mathematical model includes the following specific steps:

[0055] Step 1: Obtain the hydrological data of the target lake, the meteorological data of the target lake location, and the water quality monitoring data of the river.

[0056] Step 2: Extract the pollutant concentrations of rivers monitored on rainy days based on water quality monitoring data, and use regression analysis to obtain the rainfall and pollutant concentration curves.

[0057] Pollutants include at least: permanganate index, COD, ammonia nitrogen, total nitrogen, and total phosphorus.

[0058] The obtained rainfall and pollutant concentration curves include:

[0059] Determine the rainfall level based on the rainfall amount.

[0060] Filter the function used in the regression analysis for each rainfall class;

[0061] The regression analysis results R 2 Based on the maximum, determine the type and coefficient of the function used in regression analysis;

[0062] Based on the function of the fitting curve, the rainfall and pollutant concentration curves are obtained.

[0063] The functions used in regression analysis include: y = A × exp (B × x) function, y = Ax 2 +Bx+C or y=A×lnx+B function.

[0064] Specifically, the rainfall levels are:

[0065] Level 1: 24-hour rainfall is less than 10 mm,

[0066] Level 2: 24-hour rainfall 10-25 mm,

[0067] Level 3: 24-hour rainfall 25-50 mm,

[0068] Level 4: 24-hour rainfall 50-100 mm,

[0069] Level 5: 24-hour rainfall 100-250 mm,

[0070] Level 6: 24-hour rainfall is greater than 250 mm.

[0071] Step 3: Based on the rainfall and pollutant concentration curves, obtain the water quality monitoring data that is not monitored on rainy days and calculate the excess rate of river pollutant concentration throughout the year.

[0072] Specifically, the calculation formula for the excess rate is:

[0073]

[0074] In formula (1), X i represents the number of days when the pollutant concentration of the ith river exceeds the standard, and D represents the total number of days in a year.

[0075] Step 4: Construct a hydrodynamic and water quality model of the target lake based on the hydrological and meteorological data of the target lake.

[0076] The specific construction steps are:

[0077] Grid the target lake to obtain multiple computational grids;

[0078] Based on the water depth of the target lake, a coordinate system is selected to divide the target lake into n layers vertically in each calculation grid;

[0079] Based on the hydrological and meteorological data of the target lake, the initial conditions and boundary conditions of the hydrodynamic and water quality model are set to construct the initial hydrodynamic and water quality model;

[0080] The parameters of the initial hydrodynamic and water quality model are calibrated and verified to obtain the hydrodynamic and water quality model of the target lake.

[0081] Specifically, the coordinate system is selected as SIG coordinates or SGZ coordinates;

[0082] When selecting SGZ coordinates, the minimum number of layers n0 in the target lake layer is ≥ 1, and satisfies:

[0083]

[0084] In formula (2), H0 represents the minimum water depth of the target lake; H1 represents the maximum water depth of the target lake; n represents the number of layers; m represents the recommended range for achieving the calculation effect, where the calculation effect is the relative error between the calculation result of the hydrodynamic water quality model and the true value, and the recommended range represents the range in which the calculation time and relative error are balanced. Specifically, as the minimum number of layers n0 increases, the relative error decreases, and the calculation time increases.

[0085] When SIG coordinates are selected, the number of layers of each computational grid in the hydrodynamic and water quality model is consistent.

[0086] The hydrodynamic and water quality model includes a hydrodynamic module, a temperature module and a water quality module. Parameter calibration and verification is to calibrate and verify the parameters of the water quality module.

[0087] The initial conditions of the hydrodynamic water quality model include: underwater topography, water depth, water surface elevation, atmospheric pressure, humidity, wind speed, wind direction, surface shortwave radiation, precipitation and cloud layer. The boundary conditions of the hydrodynamic water quality model include: inflow and outflow of the lake, water level, water temperature of each layer in the n layers and pollutant concentration.

[0088] Step 5: Based on the hydrodynamic water quality model of the target lake, calculate the impact of changes in pollution concentrations in rivers entering the lake on the pollutant concentrations in the entire lake.

[0089] The disturbance of boundary conditions is an increase or decrease of 10% to 40% in the pollution load of rivers entering the lake. The calculation formula for the degree of impact is:

[0090]

[0091] In formula (3), θ j represents the disturbed input river pollutant concentration; y j represents the output variable after the boundary condition perturbation; y0 represents the output obtained by the reference boundary condition; δθ i represents the change of the i-th boundary condition; E[|y j -y0|] represents the average of the total deviations.

[0092] Embodiment 2:

[0093] The method provided in Example 1 is used to calculate the impact of the pollution of the river X1 entering the lake on Lake A.

[0094] According to steps 1-3, we get Figure 2 The pollutant concentration distribution map of river X1 throughout the year is shown.

[0095] According to step 4, a hydrodynamic water quality model of Lake A is established. Using the established hydrodynamic water quality model, the pollutant concentration of the river monitored on rainy days is calculated to obtain the model mean. The measured mean value of rainy day monitoring is compared with the model mean value, as shown in Table 1:

[0096] Table 1: Model validation results for Lake A

[0097]

[0098] According to step 5, under the condition that the boundary disturbance is a 30% increase or decrease in the pollution load of the rivers entering the lake, the impact degree is calculated and the following is obtained: Figure 3 Results of the pollution impact of rivers entering the lake are shown.

[0099] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for assessing the impact of pollution on rivers entering a lake based on a mathematical model, characterized in that: include: Obtain hydrological data of the target lake, meteorological data of the target lake location, and water quality monitoring data of the river; Based on the water quality monitoring data, the pollutant concentrations of rivers monitored on rainy days were extracted, and the rainfall and pollutant concentration curves were obtained using regression analysis. The obtaining of the rainfall and pollutant concentration curves comprises: Determine the rainfall level based on the rainfall amount. Filter the function used in the regression analysis for each rainfall class; The regression analysis results R 2 The maximum is used as the basis to determine the type and coefficient of the function used in the regression analysis method; wherein the functions used in the regression analysis method include: y = A × exp (B × x) function, y = Ax 2 +Bx+C or y=A×lnx+B function; Based on the function of the fitting curve, the rainfall and pollutant concentration curves are obtained; Based on the rainfall and pollutant concentration curves, the water quality monitoring data not monitored on rainy days are obtained, and the excess rate of river pollutant concentration throughout the year is calculated; Based on the hydrological and meteorological data of the target lake, a hydrodynamic and water quality model of the target lake is constructed; The construction of the hydrodynamic water quality model of the target lake includes: Based on the water depth of the target lake, a coordinate system is selected and the target lake is divided into n layers vertically; wherein the selected coordinate system is a SIG coordinate or a SGZ coordinate; Among them, when the SGZ coordinates are selected, the minimum number of layers in the target lake is n0≥1, and it satisfies: In formula (2), H0 represents the minimum water depth of the target lake; H1 represents the maximum water depth of the target lake; n represents the number of layers; m represents the recommended range for achieving the calculation effect, the calculation effect is the relative error between the calculation result of the hydrodynamic water quality model and the true value, and the recommended range represents the range in which the calculation time and relative error are balanced; Based on the hydrological data and meteorological data of the target lake, the initial conditions and boundary conditions of the hydrodynamic water quality model are set to construct an initial hydrodynamic water quality model; wherein the initial conditions of the hydrodynamic water quality model include: underwater topography, water depth, water surface elevation, atmospheric pressure, humidity, wind speed, wind direction, water surface shortwave radiation, precipitation and cloud layer; the boundary conditions of the hydrodynamic water quality model include: inflow and outflow of the lake, water level, water temperature of each layer in the n layers and pollutant concentration; Calibrate and verify the parameters of the initial hydrodynamic and water quality model to obtain the hydrodynamic and water quality model of the target lake; Based on the hydrodynamic water quality model of the target lake, calculate the impact of changes in pollution concentrations in rivers entering the lake on the pollutant concentrations in the entire lake.

2. The method for evaluating the impact of pollution on rivers entering a lake based on a mathematical model according to claim 1 is characterized in that: The calculation formula of the excess rate is: In formula (1), X i represents the number of days when the pollutant concentration of the ith river exceeds the standard, and D represents the total number of days in a year.

3. The method for evaluating the impact of pollution of rivers entering a lake based on a mathematical model according to claim 1 is characterized in that: The calculation formula for the impact degree is: In formula (3), θ i represents the disturbed input river pollutant concentration; y j represents the output variable after the boundary condition perturbation; y0 represents the output obtained by the reference boundary condition; δθ i represents the change of the i-th boundary condition; E[|y j -y0|] represents the average of the total deviations.

4. The method for evaluating the impact of pollution of rivers entering a lake based on a mathematical model according to claim 3 is characterized in that: The disturbance of the boundary condition is that the pollution load of the rivers entering the lake increases or decreases by 10% to 40%.

Images