A tracer particle-based urban drainage partitioning method

Abstract

The application discloses a kind of urban drainage partition division methods based on tracer particle, the method includes the following steps: step 1, urban drainage model construction and rating;Step 2, batch definition tracer particle;Step 3, different magnitude rainfall analysis calculation;Step 4, discharge port tracer particle amount statistics;Step 5, drainage partition division.The method based on the particle tracking described in the application, combined with urban drainage model, accurate division of urban drainage partition is realized;Compared with the traditional way of partitioning drainage partition is more accurate, and the labor cost is lower, while improving work efficiency, provide scientific reference for urban drainage system planning, design and operation.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of urban drainage system management, and particularly relates to a method for dividing urban drainage zones based on tracer particles. BACKGROUND

[0002] Drainage zoning is a basic unit of urban drainage system planning, design and operation and management. Accurate division of urban drainage zones under different conditions and determination of the final flow direction of urban rainfall runoff are key links of fine operation, planning and design and simulation analysis of drainage. At present, drainage zoning is mainly manually divided according to the distribution of drainage pipe network and high-precision urban terrain, combined with field reconnaissance and experience judgment, or more simply divided by using Thiessen polygon and then properly adjusted. Regardless of manual or semi-manual division method, the final result has certain deviation, and there is a problem of large workload for a large drainage system: on the one hand, for a simple tree-shaped pipe network system (water flow direction gradually from upstream to downstream), the water flow judgment method is relatively clear, and the drainage zoning division is also relatively simple, but the large-scale urban drainage system more or less has various ring-shaped pipe network systems, and the flow direction of such pipes cannot be simply judged; on the other hand, with the difference of urban area rainfall level, the main flow direction of part of the drainage system may not be single, but dynamic, which may flow to one drainage outlet when the rainfall is small, and flow to another drainage outlet when the rainfall is large. Therefore, how to more accurately divide the urban drainage zones is a technical problem to be solved in the field at present. SUMMARY

[0003] The present application aims to provide a method for dividing urban drainage zones based on tracer particles to solve the above technical problems.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0005] The present application discloses a method for dividing urban drainage zones based on tracer particles, which comprises the following steps:

[0006] Step 1, construction and calibration of urban drainage model: arrange and collect the drainage pipe network data in the study area, process the drainage pipe network data, then divide the sub-catchment, i.e. runoff area, based on the drainage pipe network nodes, construct the urban drainage model, and calibrate the constructed urban drainage model by using the measured data;

[0007] Step 2, batch definition of tracer particles: in the urban drainage model, a batch of tracer particles is defined for each drainage pipe network node, the tracer particles are non-degradable and attenuated pollutants in the pipe, which can flow with water flow; and a certain amount of tracer particles are added to the corresponding drainage pipe network nodes of the drainage pipe network model;

[0008] Step 3, different magnitude rainfall analysis calculation: different rainfall scenarios are used to drive the drainage model for simulation analysis and calculation, and the runoff and tracer particle amount of each discharge port are output; the different rainfall scenarios include light rain, moderate rain, heavy rain and heavy rain scenarios;

[0009] Step 4, tracer particle amount statistics of discharge port: taking the discharge port as the unit, the tracer particle amount of each discharge port under different rainfall scenarios is counted, and the tracer particle distribution ratio and discharge ratio are calculated according to formulas (1) and (2) respectively:

[0010] (1)

[0011] (2)

[0012] In the formula: PD i,j is the tracer particle distribution ratio of the i-th tracer particle at the j-th discharge port; MO j,i is the amount of the i-th tracer particle flowing out of the j-th discharge port under a certain rainfall scenario, with the unit of mg; N out is the number of discharge ports; is the total amount of the i-th tracer particle of all discharge ports, with the unit of mg; PT i,j is the tracer particle discharge ratio of the i-th tracer particle at the j-th discharge port; MI i is the total input amount of the i-th tracer particle, with the unit of mg;

[0013] The calculated tracer particle discharge ratio value is compared with the reference value to determine whether the result meets the standard, and if not, the model is adjusted and optimized until the result meets the standard;

[0014] Step 5, drainage zoning division: the drainage network node runoff area is corresponded with the discharge port, and is divided into single discharge area and variable discharge area according to the corresponding relationship; the tracer particle distribution ratio value under the light rain scenario is taken as the static drainage zoning division basis, and the main discharge port and the secondary discharge port of each drainage network node are determined according to the tracer particle distribution ratio value from large to small; the collection of the drainage area of the drainage network node corresponding to each discharge port is the drainage area of the discharge port; after determining the drainage area corresponding to each discharge port, the discharge ports that can be combined are determined through topography and water system factors, and are combined into a drainage zone, which is a static drainage zone; similarly, the other rainfall scenarios are calculated and divided into drainage zones as dynamic drainage zoning results.

[0015] Further, the calibration of the constructed urban drainage model in step 1 is specifically: adjusting the runoff and confluence parameters to make the model calculation results consistent with the actual situation.

[0016] Further, in step 1, when the measured data is insufficient to calibrate the urban drainage model, the rationality of the urban drainage model is analyzed, that is, the rationality of the model results is judged through the runoff coefficient, water quantity error and overflow size.

[0017] Further, in step 1, the processing of the drainage pipe network data is specifically drainage pipe network topology checking and generalization; the drainage pipe network nodes include rainwater wells, inspection wells and rainwater gratings in the drainage pipe network; and the division of the sub-catchment is specifically based on the positions of the drainage pipe network nodes, combined with the terrain, and the Thiessen polygon is used for division.

[0018] Further, in step 2, when the tracer particles are defined, the names of the tracer particles are named as the names of the drainage pipe network nodes or similar structure names.

[0019] Further, in step 2, when a certain amount of tracer particles is added to the corresponding drainage pipe network nodes of the drainage pipe network model, for the open source model or commercial model software adding mode, the drainage pipe network node inflow and the pollutant concentration are combined.

[0020] Further, in step 3, the light rain, moderate rain, heavy rain and heavy rain scenarios are respectively the design rainstorms with a return period of 0.5 years, 2 years, 10 years and 20 years.

[0021] Further, in step 4, the adjustment and optimization of the model are specifically checking and adjusting the runoff concentration parameter setting, time step and simulation method selection.

[0022] The beneficial effects of the present application are that the method disclosed in the present application realizes accurate division of urban drainage zoning based on particle tracing combined with an urban drainage model; compared with the traditional way of dividing drainage zoning, the method is more accurate, has lower labor cost and improves work efficiency, and provides scientific reference for urban drainage system planning, design and operation.

[0023] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The flowchart of the method disclosed in the present application is shown in the figure;

[0025] Figure 2 The schematic diagram of the tracer particle discharge ratio PT reference value is shown in the figure;

[0026] Figure 3 The schematic diagram of the drainage pipe network distribution in the research area in embodiment one is shown in the figure;

[0027] Figure 4 The schematic diagram of the tracer particle setting in embodiment one is shown in the figure;

[0028] Figure 5 Figure 1 is a schematic diagram of the load amount of tracer particles at the discharge port in Example 1;

[0029] Figure 6 Figure 2 is a schematic diagram of the distribution proportion and discharge proportion of tracer particles under a light rain scenario in Example 1;

[0030] Figure 7 Figure 3 is a schematic diagram of the distribution proportion and discharge proportion of tracer particles under a heavy rain scenario in Example 1;

[0031] Figure 8 Figure 4 is a schematic diagram of the single drainage zoning and variable drainage zoning in Example 1;

[0032] Figure 9 Figure 5 is a schematic diagram of the static drainage zoning result in Example 1. DETAILED DESCRIPTION

[0033] The present application discloses a tracer particle-based urban drainage zoning method, as shown in the following schematic diagram: Figure 1 The method comprises the following steps:

[0034] Step 1, urban drainage model construction and calibration: collect and arrange the drainage network data in the study area, and process the drainage network data, specifically, drainage network topology inspection and generalization. Then, divide sub-catchment (runoff area) based on the drainage network nodes, construct the urban drainage model, and use the measured rainfall runoff and water accumulation data (generally obtained from the hydro-meteorological department) to calibrate the constructed urban drainage model.

[0035] The drainage network nodes refer to the rainwater wells, inspection wells, rainwater gratings, etc. in the drainage network. Generally, the sub-catchment is divided based on the location of the drainage network nodes, combined with the terrain, and using the Thiessen polygon. The calibration of the urban drainage model is specifically adjusting the runoff parameters, such as the infiltration rate, impermeable rate, catchment width, roughness, etc., so that the model calculation results are consistent with the actual situation.

[0036] The results generated by using the calibrated model are more accurate. If there is no actual data for calibration, it is only necessary to analyze the reasonableness of the model, that is, to judge the reasonableness of the model results through the runoff coefficient, water quantity error, and overflow amount.

[0037] Step 2, Batch definition of tracer particles: In the urban drainage model, a batch is defined for each drainage network node, and a tracer particle is a non-degradable and decaying pollutant in the pipeline that can flow with the water flow. Assuming that the names of the drainage network nodes are NODE-1, NODE-2,..., NODE-N, in order to establish a mapping relationship faster, the names of the tracer particles can be directly named as the drainage network node names or similar structure names (such as PT-NODE-1, PT-NODE-2,..., PT-NODE-N). A certain amount (assuming MI i , unit: mg) of tracer particles PT-NODE-i (i is the tracer particle number, i = 1, 2,..., N) is added to the corresponding drainage network node NODE-i of the drainage network model. For open source models or commercial model software (such as SWMM, InfoWorks ICM), the addition method can be in the form of combined inflow and pollutant concentration of the drainage network node.

[0038] Step 3, Different magnitude rainfall analysis and calculation: Different magnitude of measured rainfall or designed storm is used to drive the drainage model, such as the design storm with return period of 0.5 years, 2 years, 10 years and 20 years is used to simulate and calculate the four rainfall scenarios (light rain, moderate rain, heavy rain and heavy rain) respectively, and the results such as the discharge flow and the amount of tracer particles of each discharge port are output.

[0039] In this step, the node inflow corresponding to the different return period storm magnitude can also be directly defined in the drainage network node.

[0040] Step 4, Tracer particle amount statistics of discharge port: The rainfall runoff flowing into the urban drainage pipeline will eventually flow to the discharge port of the drainage system and further flow into the river. Taking the discharge port as the unit, the amount of tracer particles flowing out of each discharge port under different rainfall scenarios is calculated, and the tracer particle distribution ratio and discharge ratio are calculated according to formulas (1) and (2) respectively:

[0041] (1)

[0042] (2)

[0043] In the formula: PD i,j is the distribution ratio of tracer particle No. i at discharge port No. j; MO j,i is the amount of tracer particle No. i flowing out of discharge port No. j under a certain rainfall scenario, unit: mg; N out is the number of discharge ports; is the total amount of tracer particle No. i of all discharge ports, unit: mg; PT i,jThe proportion of tracer particles emitted from emission port j, designated as i; MI i This represents the total input quantity of the tracer particle numbered i, in mg.

[0044] The total number of tracer particles in formula (1) is the sum of tracer particles from all discharge outlets, rather than the total number of tracer particles at the input node at the start of the calculation. This is because: firstly, due to numerical errors in the drainage model, the total number of a certain type of tracer particles used may be slightly reduced or increased; secondly, some nodes may overflow during heavy rain, causing tracer particles to be out of the drainage system; and thirdly, some tracer particles may remain in the pipes and not be discharged to the drainage outlet in time (to avoid this situation, the simulation should be performed for as long as possible until the confluence is basically over).

[0045] Based on practical experience, the reference values ​​for tracer particle emission ratio (PT) under different rainfall scenarios are as follows: Figure 2 As shown, adjustments can be made as needed based on the actual situation. When the tracer particle emission ratio PT value is less than the corresponding ratio in the figure, the result is considered unsatisfactory, and the model should be adjusted and optimized, including checking and adjusting the generation and confluence parameter settings, time step, and simulation method (dynamic wave, motion wave, etc.) selection, until the result meets the requirements.

[0046] Step 5: Drainage Zone Division: Once the tracer particle discharge ratio meets the standard, the runoff generation zones of drainage network nodes are mapped to their discharge outlets. If all tracer particles from a drainage network node flow to a single discharge outlet, the runoff generation zone of that node is considered to have a one-to-many correspondence with its discharge outlet, i.e., a single discharge zone. If tracer particles from a drainage network node are present at two or more discharge outlets, the runoff generation zone of that node is considered to have a one-to-many correspondence with its discharge outlet, i.e., a variable discharge zone. It is important to note that determining variable discharge zones is crucial for drainage facility management agencies to more accurately understand the current state of regional drainage.

[0047] Drainage zoning may change with increasing rainfall and intensity, but for management purposes, a static drainage zoning plan, while having some margin of error, is often necessary and generally reasonable. After the PT value meets the standard, the tracer particle distribution ratio (PD value) under a light rain scenario (a design storm with a return period of 0.5 years) is used as the basis for static drainage zoning. The main and secondary discharge outlets of each drainage network node are determined according to their PD values, from largest to smallest. The set of catchment areas corresponding to each discharge outlet is the catchment area for that discharge outlet. After determining the catchment area for each discharge outlet, factors such as topography and water systems are used to determine which discharge outlets can be merged into a single drainage zone. The set of catchment areas corresponding to these discharge outlets constitutes a defined static drainage zone.

[0048] Suppose that 100 kinds of particles such as PT-NODE-1, PT-NODE-2,..., PT-NODE-100 are simulated at the outfall OUTFALL-1, which indicates that the inflows of the corresponding NODE-1, NODE-2,..., NODE-100 of the drainage network nodes all flow to this outfall, and further analysis and calculation of the main outfall of these drainage network nodes are performed, and if they are all OUTFALL-1, it is considered that the catchment area corresponding to these nodes is a relatively independent drainage subarea, and all flows to OUTFALL-1.

[0049] Similarly, other magnitudes of design rainstorms such as 2-year, 10-year and 20-year rainstorms are calculated and the drainage subareas are divided in the above manner, and the results are used as the dynamic drainage subarea results.

[0050] Embodiment One

[0051] The embodiment is an application example of the above method.

[0052] The embodiment discloses a city drainage subarea division method based on tracer particles, comprising the following steps:

[0053] Step 1, city drainage model construction and calibration: collate and collect the drainage network data in the study area, and process the drainage network data, specifically drainage network topology checking and generalization. Then, the city drainage model is constructed based on the drainage network nodes, and the measured rainfall runoff and water accumulation data are used to calibrate the constructed city drainage model. As shown in Figure 3 , the drainage network data of the study area in the embodiment is processed, and finally 61 inspection wells, 67 drainage pipes and 5 outfalls are obtained.

[0054] Step 2, batch definition of tracer particles: as shown in Figure 4 , in the city drainage model, a batch of tracer particles is defined for each drainage network node, the names of the current drainage network nodes are 1, 2,..., 61, and the names of the tracer particles are directly named as P1, P2,..., P61. A certain amount (assuming MI i , unit: mg) of particles Pi is added to the corresponding drainage network node i of the drainage network model, and the open source model SWMM is used, and the addition mode is the combination of node inflow and pollutant concentration.

[0055] Step 3, analysis and calculation of different magnitude rainfalls: the node inflow corresponding to the small rain scenario (0.5-year) and the large rain scenario (20-year) is used to drive the city drainage model, and simulation analysis and calculation are performed, and the results such as the outfall runoff and the amount of tracer particles are output.

[0056] Step 4, outlet tracer particle amount statistics: the rainfall runoff flowing into the urban drainage pipe will eventually flow to the outlet of the drainage system and further flow into the river. Taking the outlet as the unit, the amount of particles flowing out of each outlet under different rainfall scenarios is counted, and the tracer particle distribution ratio and discharge ratio are calculated. The load amount of some tracer particles at the outlet is shown in Figure 5 , and the calculation results of the tracer particle distribution ratio and discharge ratio are shown in Figure 6 , Figure 7 In this embodiment, the PT value is greater than 95%, which meets the requirements.

[0057] Step 5, drainage partition division: if the tracer particle discharge ratio meets the requirements, the drainage pipe network node runoff area is corresponded to the outlet. If the tracer particles of a certain drainage pipe network node flow to one outlet, it is considered that the runoff area of the drainage pipe network node has a single corresponding relationship with the outlet, that is, a single discharge area. If the tracer particles of a certain drainage pipe network node exist in two or more outlets, it is considered that the runoff area of the drainage pipe network node has a one-to-many corresponding relationship with the outlet, that is, a variable discharge area. The discharge area distribution of this embodiment is shown in Figure 8 .

[0058] The PD value under the light rain scenario (0.5-year design rainstorm) is used as the basis for static drainage partition division, and the main outlet and the secondary outlet of each drainage node are determined according to the PD value from large to small. The collection of the catchment area of the nodes corresponding to each outlet is the catchment area of the outlet. After determining the catchment area corresponding to each outlet, it is determined which outlets can be combined into one drainage partition through topography and water system factors. The collection of the catchment areas corresponding to these outlets is a well-divided static drainage partition. The static drainage partition division results of this embodiment are shown in Figure 9 .

[0059] Similarly, the 20-year design rainstorm is used to calculate and divide the drainage partition in the above-mentioned manner, and the result is used as the dynamic drainage partition result.

[0060] Finally, it should be noted that the above description is only used to illustrate the technical solutions of the present application and is not limited. Although the present application has been described in detail with reference to the preferred arrangement, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A tracer particle-based urban drainage zoning method, characterized by, The method comprises the following steps: Step 1, urban drainage model construction and calibration: collect and arrange the drainage pipe network data in the study area, process the drainage pipe network data, then divide the sub-catchment, i.e. runoff area, based on the drainage pipe network nodes, construct the urban drainage model, and calibrate the constructed urban drainage model by using the measured data; Step 2, batch definition of tracer particles: in the urban drainage model, a batch of tracer particles is defined for each drainage pipe network node, the tracer particles are non-degradable and attenuated pollutants in the pipeline, which can flow with the water flow; and a certain amount of tracer particles are added to the corresponding drainage pipe network nodes of the drainage pipe network model; Step 3, analysis and calculation of different magnitude rainfall: different rainfall scenarios are used to drive the drainage model for simulation analysis and calculation, and the runoff and tracer particle amount of each discharge port are output; the different rainfall scenarios include light rain, moderate rain, heavy rain and heavy rain scenarios; Step 4, tracer particle amount statistics of discharge port: the amount of tracer particles flowing out of each discharge port under different rainfall scenarios is counted, and the tracer particle distribution ratio and discharge ratio are calculated according to formulas (1) and (2) respectively: （1） （2） wherein: PD i,j is the proportion of the tracer particles numbered i at the discharge numbered j; MO j,i is the amount of the tracer particles numbered i discharged by the discharge numbered j under a certain rainfall scenario, in mg; N out is the number of discharges; is the total amount of the tracer particles numbered i of all discharges, in mg; PT i,j is the proportion of the tracer particles numbered i at the discharge numbered j; MI i is the total input amount of the tracer particles numbered i, in mg; The calculated tracer particle discharge ratio value is compared with the reference value to determine whether the result meets the standard, if not, the model is adjusted and optimized until the result meets the standard; Step 5, drainage partition division: the drainage pipe network node runoff area is corresponded with the discharge port, and according to the corresponding relationship, it is divided into single discharge area and variable discharge area; the tracer particle distribution ratio value under the light rain scenario is taken as the basis for static drainage partition division, and the main discharge port and the secondary discharge port of each drainage pipe network node are determined according to the tracer particle distribution ratio value from large to small; the collection of the drainage pipe network nodes of the catchment area corresponding to each discharge port is the catchment area of the discharge port; after determining the catchment area corresponding to each discharge port, the discharge ports that can be combined are determined through topography and water system factors, and they are combined into a drainage partition, which is a static drainage partition; similarly, the other rainfall scenarios are calculated and divided into drainage partitions as dynamic drainage partition results.

2. The tracer particle-based urban drainage zoning method according to claim 1, wherein, The calibration of the constructed urban drainage model in step 1 is specifically: adjusting the runoff and confluence parameters to make the model calculation results consistent with the actual situation.

3. The tracer particle-based urban drainage zoning method according to claim 1, wherein, When there is a lack of measured data to calibrate the urban drainage model in step 1, a reasonable analysis of the urban drainage model is performed, i.e. judging the reasonableness of the model results through runoff coefficient, water quantity error and overflow amount.

4. The tracer particle-based urban drainage zoning method according to claim 1, wherein, The processing of the drainage pipe network data in step 1 is specifically drainage pipe network topology checking and generalization; the drainage pipe network nodes include the rainwater well, inspection well and rainwater grate in the drainage pipe network; the division of the sub-catchment is specifically based on the position of the drainage pipe network nodes, combined with the terrain, and using the Thiessen polygon to divide.

5. The tracer particle-based urban drainage zoning method according to claim 1, wherein, When defining the tracer particles in step 2, the name of the tracer particles is named as the name of the drainage pipe network node or similar structure name.

6. The tracer particle-based urban drainage zoning method of claim 1, wherein, The tracer particles are added to the corresponding sewer nodes in the sewer network model in step 2, and the open source model or commercial model software is used to add the inflow and pollutant concentration of the sewer nodes in combination.

7. The tracer particle-based urban drainage zoning method of claim 1, wherein, The light rain, moderate rain, heavy rain and heavy storm scenarios in step 3 are design rainstorms with return periods of 0.5 years, 2 years, 10 years and 20 years, respectively.

8. The tracer particle-based urban drainage zoning method of claim 1, wherein, The adjustment and optimization of the model in step 4 specifically includes checking and adjusting the runoff concentration parameter settings, time step and simulation method selection.

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