Zonal tracer assessment of direct and indirect hydrologic benefits of source LID measures

Abstract

This invention provides a zonal tracer assessment method for the direct and indirect hydrological benefits of source-tracing LID (Low Impact Damping) measures, relating to the field of urban stormwater management technology. The invention constructs a coupled model of a PCSWMM one-dimensional pipeline and river model and a two-dimensional surface runoff model, and calibrates and validates it using historical rainfall data and waterlogging monitoring data. Within the study area, drainage zones are divided, distinguishing between natural zones and LID measure zones. By configuring dedicated tracers for different zones and simulating scenarios without and with LID measures, tracer contribution matrices and contribution rate matrices are established. The surface waterlogging contribution changes are calculated by coupling with surface waterlogging data, and the direct and indirect benefits of LID measures are decomposed, achieving a refined and quantifiable assessment of the hydrological benefits of LID measures.

Description

Technical Field

[0001] This invention relates to the field of urban stormwater management technology, and in particular to a zonal tracer assessment method for the direct and indirect hydrological benefits of source tracing (LID) measures. Background Technology

[0002] Low Impact Development (LID) measures, as an important means to alleviate urban flooding, control non-point source pollution and restore the urban water cycle, have been widely used in sponge city construction and stormwater management practices.

[0003] Existing assessments typically use macro-level indicators such as regional overall runoff reduction rate and peak change to reflect the overall performance of the system. However, it is difficult to quantify the differentiated contributions of different LID units to specific drainage zones. As a result, planning and design are prone to problems such as layout based on experience or indicators, and lack of precise spatial matching for specific objectives.

[0004] The hydrological impacts of LID measures are complex. Their benefits include both the direct reduction of runoff in the catchment area and the systemic indirect effects caused by infiltration, depression filling, and changes in surface roughness. Existing technologies lack effective means to separate and quantify direct and indirect benefits, which can easily lead to an overestimation of the effects of local measures and obscure synergistic or antagonistic effects, thus hindering the optimal configuration of multiple measures. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, the purpose of this invention is to provide a zonal tracer assessment method for the direct and indirect hydrological benefits of source-tracing LID measures. A zonal tracer assessment system oriented towards drainage zones is constructed. By configuring dedicated tracers for natural zones and LID measure zones and establishing a contribution matrix, a refined quantitative analysis of the contribution amount and contribution rate of surface water accumulation from the source to the receiving zone is achieved.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] A zonal tracer assessment method for the direct and indirect hydrological benefits of source-tracing LID measures includes:

[0008] Establish a coupled model of PCSWMM one-dimensional pipeline and river model with two-dimensional surface runoff model;

[0009] The coupled model was calibrated and validated using historical rainfall data and waterlogging monitoring data to obtain a validated model.

[0010] Within the study area corresponding to the verification model, the study area is divided into multiple drainage zones according to the drainage network direction and land use type. Within each drainage zone, the natural zones of sub-catchments without LID measures and the LID measure zones of sub-catchments with planned LID measures are determined.

[0011] Configure tracers for the natural partitions and configure tracers for the LID measure partitions;

[0012] The drainage zone where the tracer was initially labeled is taken as the source zone, and the drainage zone where the tracer was finally monitored or had an impact is taken as the receiving zone. The scenarios without LID measures and the LID measures are simulated respectively to obtain the tracer contribution matrix and tracer contribution rate matrix of the two simulated scenarios, and the surface water volume of each source zone is obtained.

[0013] The surface water volume is coupled with the tracer contribution matrix, and the surface water contribution matrix and surface water contribution rate matrix for the two scenarios are calculated respectively. The surface water contribution change matrix and surface water contribution change rate matrix are obtained, and the direct and indirect benefits of LID measures are decomposed and output based on the surface water contribution change rate matrix.

[0014] Preferably, a coupled model is established between the PCSWMM one-dimensional pipeline and river model and the two-dimensional surface runoff model, including:

[0015] Elevation data, boundary conditions, and building outlines are input into the 2D module of PCSWMM to construct a two-dimensional surface runoff model based on hexagonal grids.

[0016] By setting bottom orifices to connect the one-dimensional pipe and river model with the two-dimensional surface runoff model, bidirectional exchange of water level and flow rate can be achieved.

[0017] Preferably, the coupled model is calibrated and validated using historical rainfall data and waterlogging monitoring data to obtain a validated model, including:

[0018] Multiple historical rainfall data sessions and corresponding waterlogging monitoring data were selected for calibration and verification.

[0019] For each rainfall event, the historical rainfall data is input into the coupled model and run to obtain the simulated maximum surface water depth at typical water accumulation points;

[0020] Extract the measured maximum surface water depth corresponding to the typical water accumulation point from the water accumulation monitoring data;

[0021] The relative error between the simulated maximum surface water depth and the measured maximum surface water depth is calculated to verify the accuracy of the coupled model.

[0022] Preferably, establishing a coupled model of the PCSWMM one-dimensional pipeline and river model and the two-dimensional surface runoff model further includes:

[0023] The land use type map of the study area was converted from CAD format to SHP format in layers, and divided into several sub-catchment areas based on elevation data, the land use type map, and the distribution of roads and storm drains;

[0024] Topology processing is performed on the drainage pipelines, and the sub-catchment areas and drainage pipelines are exported as SHP format. An INP file that can be recognized by SWMM is generated through the inpPINS plugin to establish the one-dimensional pipeline and river model.

[0025] Preferably, the calibration and verification steps include:

[0026] Deterministic parameters and nondeterministic parameters are set, wherein the deterministic parameters are determined based on geographic data; the deterministic parameters include the area of ​​the sub-catchment, characteristic width, permeability, pipe network diameter, burial depth, and stormwater well depth;

[0027] The values ​​of the calibration nondeterministic parameters are determined based on the SWMM manual and the empirical range of the study area, and these calibration nondeterministic parameters are used as the adjustment objects for calibration and verification; the calibration nondeterministic parameters include Manning coefficient, depression storage capacity and Horton infiltration parameter.

[0028] Preferably, within the study area corresponding to the verification model, the study area is divided into multiple drainage zones according to the drainage network orientation and land use type. Within each drainage zone, natural zones of sub-catchments without LID measures and LID measure zones of sub-catchments planned to have LID measures are determined, including:

[0029] The boundaries of each drainage zone are determined based on the pipeline route and confluence path of the drainage network, and each sub-catchment area within the study area is merged into the corresponding drainage zone according to the drainage zone into which the runoff flows.

[0030] The type of LID (Land Use Implementation) measure is determined based on the land use type of the sub-catchment area;

[0031] In the coupled model, the basic parameters of the LID measures are set for the LID measure type; the basic parameters of the LID measures are the parameters required by the coupled model to perform hydrological process simulation on the LID measure zoning under the LID measure scenario, so that the coupled model can output the surface water volume of each source zoning under the LID measure scenario, as well as the tracer contribution matrix and the tracer contribution rate matrix;

[0032] Within each drainage zone, select the sub-catchment area from the sub-catchment areas to plan and deploy LID measures, and determine the deployment area.

[0033] Sub-catchment areas that were not selected for the planning and deployment of LID measures were identified as the natural zones, and sub-catchment areas that were selected for the planning and deployment of LID measures were identified as the LID measure zones.

[0034] Preferably, configuring tracers for the natural partitions and for the LID measure partitions includes configuring tracers for the LID measure partitions.

[0035] For each natural zone within the aforementioned drainage zone, a tracer for that natural zone is configured and named according to "0, zone number";

[0036] For each drainage zone, a tracer corresponding to the LID measure type is configured for the LID measure zone, and named according to "LID category number, zone number"; the number of LID measure types corresponding to the LID category number is M, so as to form tracers of N types of natural zones and tracers of N×M types of LID measure zones in the study area;

[0037] Tracer labeling is performed on each of the sub-catchments, and the labeling rules are as follows: sub-catchments of natural zones use the tracer labeling of natural zones, and sub-catchments of LID zone use the tracer labeling of LID zone.

[0038] The source concentration of tracer at the outlet of the marked sub-catchment area is set to a constant value of 1 mg / L, and the source concentration is kept consistent in both the no-LID and LID scenarios.

[0039] The attenuation coefficient is set to 0 to ensure that the tracer does not attenuate before entering the confluence node, and to maintain the attenuation coefficient consistent in both the no-LID and LID scenarios; the source concentration and the attenuation coefficient are used to ensure that tracer signals from different partitions can be used to construct the tracer contribution matrix and the tracer contribution rate matrix.

[0040] Preferably, the drainage zone where the tracer was initially labeled is designated as the source zone, and the drainage zone where the tracer was ultimately monitored or had an impact is designated as the receiving zone. Simulations are performed for both the no-LID (Low-Intensity Discharge) and LID (Low-Intensity Discharge) scenarios to obtain the tracer contribution matrix and tracer contribution rate matrix for the two simulated scenarios. The surface water accumulation in each source zone is also obtained, including:

[0041] In the coupling model, the drainage zone where the tracer is initially tagged is defined as the source zone, the drainage zone where the tracer is ultimately monitored or has an effect is defined as the receiving zone, and each drainage zone is simultaneously used as both a source zone and a receiving zone.

[0042] Run the scenarios without LID measures and with LID measures respectively, and output the tracer contribution from natural partitions to each receiving partition within each source partition, as well as the tracer contribution from each LID-measured partition to each receiving partition within each source partition.

[0043] A tracer contribution matrix for a scenario without LID measures is constructed based on the tracer contribution output in the scenario without LID measures, and a tracer contribution matrix for a scenario with LID measures is constructed based on the tracer contribution output in the scenario with LID measures; the matrix elements of the tracer contribution matrix are the tracer contribution of the natural partition within the source partition or the LID measure partition within the source partition to the receiving partition.

[0044] The tracer contribution matrix for the no-LID scenario is normalized according to the total tracer amount in the receiving zone to obtain the tracer contribution rate matrix for the no-LID scenario, and the tracer contribution matrix for the LID scenario is normalized according to the total tracer amount in the receiving zone to obtain the tracer contribution rate matrix for the LID scenario.

[0045] In the simulation outputs of both the LID (Low Identification and Discharge) scenario and the LID scenario, the surface water volume of each source zone is extracted; the surface water volume of each source zone is used to calculate the surface water contribution matrix and the surface water contribution rate matrix.

[0046] Preferably, the surface water volume is coupled with the tracer contribution matrix, and the surface water contribution matrix and surface water contribution rate matrix for the two scenarios are calculated respectively to obtain the surface water contribution change matrix and surface water contribution change rate matrix, including:

[0047] The surface water volume of each source area under the scenario without LID measures and the surface water volume of each source area under the scenario with LID measures were obtained respectively.

[0048] For the scenario without LID measures, the surface water volume of each source zone under the scenario without LID measures is coupled with the tracer contribution rate matrix of the scenario without LID measures to obtain the surface water contribution matrix of the scenario without LID measures. The matrix elements of the surface water contribution matrix are the surface water contribution of the natural zone or the LID-measure zone within the source zone to the receiving zone. The surface water contribution matrix of the scenario without LID measures is normalized according to the total surface water volume of the receiving zone to obtain the surface water contribution rate matrix of the scenario without LID measures.

[0049] For the LID (Low-Intensity Discharge) scenario, the surface water volume of each source zone under the LID scenario is coupled with the tracer contribution rate matrix of the LID scenario to obtain the surface water contribution matrix of the LID scenario.

[0050] The surface water contribution matrix of the LID measures scenario is normalized according to the total surface water volume of the receiving zone to obtain the surface water contribution rate matrix of the LID measures scenario.

[0051] The surface water contribution change matrix is ​​obtained by subtracting the surface water contribution matrix under the LID (Low Identification and Discharge) scenario from the surface water contribution matrix under the LID scenario.

[0052] Normalize the matrix of changes in the contribution of surface water volume to surface water under the scenario without LID measures to obtain the matrix of changes in the contribution rate of surface water.

[0053] When the surface water volume of the source zone is 0 in the scenario without LID measures, the change rate corresponding to the source zone in the surface water contribution change rate matrix is ​​defined as 0.

[0054] Preferably, the direct and indirect benefits of LID measures are output based on the decomposition of the surface water contribution change rate matrix, including:

[0055] For each source zone, the sum of the rate of change of the contribution of natural zones to the surface water of all receiving zones is calculated, and the sum of the rate of change of the contribution of natural zones to the surface water of all receiving zones is defined as the indirect benefit of the source zone.

[0056] For each source zone, the sum of the rate of change of the contribution of each LID measure zone to the surface water of all receiving zones is calculated, and the sum of the rate of change of the contribution of each LID measure zone to the surface water of all receiving zones is defined as the direct benefit of the source zone.

[0057] The direct benefits of LID measures in the study area are obtained by summing the direct benefits of each source area, and the indirect benefits of LID measures in the study area are obtained by summing the indirect benefits of each source area.

[0058] The present invention discloses the following technical effects:

[0059] (1) This invention establishes a coupled model of the PCSWMM one-dimensional pipeline and river model and the two-dimensional surface runoff model, and uses historical rainfall data and waterlogging monitoring data for calibration and verification, so that subsequent assessments are based on simulations consistent with the waterlogging process in the study area. Compared with conventional methods that only give the overall runoff reduction or single-point reduction effect, this scheme can characterize the differences in runoff and waterlogging response between drainage zones at the study area scale, providing a reliable premise for quantitative assessment at the zone level.

[0060] (2) Within the study area corresponding to the verification model, this invention divides the study area into multiple drainage zones according to the drainage network direction and land use type, and further distinguishes between natural zones without LID measures and LID measure zones with planned LID measures within each drainage zone. Thus, the evaluation object is refined from the overall region to drainage zones and their internal source units, enabling differentiated water accumulation contribution results for different drainage zones, avoiding the problem that traditional methods struggle to characterize the differences in contribution of different units to specific downstream drainage zones.

[0061] (3) This invention configures tracers with different naming rules for natural and LID (Low Identification and Discharge) zones, sets the source concentration to be constant and the attenuation coefficient to 0, and then simulates scenarios without LID measures and LID measures respectively to obtain tracer contribution matrices and tracer contribution rate matrices for the two scenarios. Through the above matrix form, the contribution relationship from the source zone to the receiving zone can be expressed in a structured and quantitative manner, realizing the distinction between natural and LID sources in terms of spatial propagation path and contribution ratio, thereby improving the interpretability and comparability of benefit attribution.

[0062] (4) This invention further couples the surface water volume and tracer contribution matrix of each source zone, calculates the surface water contribution matrix and surface water contribution rate matrix for the two scenarios, and obtains the surface water contribution change matrix and surface water contribution change rate matrix. Finally, based on the surface water contribution change rate matrix, the direct and indirect benefits of LID measures are decomposed and output. This decomposition mechanism can distinguish the reduction contribution caused by the LID measure zone itself from the contribution change caused by the change in the system hydraulic conditions of the natural zone, providing a more granular quantitative basis for the precise layout of LID measures, the determination of the priority of zoned governance, and the synergistic optimization of multiple measures. Attached Figure Description

[0063] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0064] Figure 1 A flowchart of the method provided in an embodiment of the present invention;

[0065] Figure 2 This is a schematic diagram of the technical route provided in the embodiments of the present invention;

[0066] Figure 3 A land use type map and a waterlogging monitoring distribution diagram of the main urban area of ​​a city are provided for embodiments of the present invention.

[0067] Figure 4This is a simplified schematic diagram of a one-dimensional PCSWMM model of the main urban area of ​​a city provided in an embodiment of the present invention;

[0068] Figure 5 This is a simplified schematic diagram of a two-dimensional PCSWMM model of the main urban area of ​​a city provided in an embodiment of the present invention;

[0069] Figure 6 Provided for embodiments of the present invention Figure 5 The diagram shows the PCSWMM 2D model mesh and pipe generalization of the local area indicated by the red box. Detailed Implementation

[0070] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0071] The purpose of this invention is to provide a regional tracer assessment method for the direct and indirect hydrological benefits of source-tracing LID measures. Based on a coupled hydrodynamic model and tracer contribution matrix, the method calculates the changes in surface water contribution under two scenarios and decomposes and outputs the direct and indirect benefits of LID measures accordingly, thereby improving the accuracy and spatial resolution of LID measure benefit attribution.

[0072] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0073] Figure 1 The method flowchart provided in the embodiments of the present invention is as follows: Figure 1 As shown, this invention provides a zonal tracer assessment method for the direct and indirect hydrological benefits of source tracing LID measures, comprising:

[0074] Step 100: Establish a coupled model of the PCSWMM one-dimensional pipeline and river model and the two-dimensional surface runoff model;

[0075] Step 200: Calibrate and validate the coupled model using historical rainfall data and waterlogging monitoring data to obtain the validated model;

[0076] Step 300: Within the study area corresponding to the verification model, the study area is divided into multiple drainage zones according to the drainage network direction and land use type. Within each drainage zone, the natural zones of sub-catchments without LID measures and the LID measure zones of sub-catchments with planned LID measures are determined.

[0077] Step 400: Configure tracers for natural partitions and configure tracers for LID measure partitions;

[0078] Step 500: Take the drainage zone where the tracer was initially marked as the source zone and the drainage zone where the tracer was finally monitored or had an impact as the receiving zone. Simulate the scenario without LID measures and the scenario with LID measures respectively, and obtain the tracer contribution matrix and tracer contribution rate matrix of the two scenarios after simulation, and obtain the surface water volume of each source zone.

[0079] Step 600: Couple the surface water volume and tracer contribution matrix, calculate the surface water contribution matrix and surface water contribution rate matrix for the two scenarios respectively, obtain the surface water contribution change matrix and surface water contribution change rate matrix, and output the direct and indirect benefits of LID measures based on the surface water contribution change rate matrix.

[0080] Specifically, the technical approach in this embodiment is as follows: Figure 2 As shown, it specifically includes:

[0081] Collect and organize the basic data for constructing the PCSWMM two-dimensional hydrodynamic model of the study area;

[0082] A PCSWMM model for the study area was constructed based on the required data, and historical rainfall data was used for calibration and validation to ensure the accuracy of the model simulation.

[0083] The area is divided into drainage zones, and the type of LID measures, sub-catchment areas and areas for LID measures are determined according to the land use type.

[0084] Construct a natural zoning tracing system and a LID (Light Detection and Reduction) measure zoning tracing system;

[0085] Simulate scenarios with and without LID (Low-Intensity Difference) measures, and compile tracer contribution matrices and tracer contribution rate matrices for each scenario. Couple the surface water volume generated by the source zoning, and calculate the surface water contribution matrix and surface water contribution variation matrix for each scenario.

[0086] The benefits of surface water accumulation generated by source zoning are decomposed, and the direct and indirect benefits of LID measures are output.

[0087] Specifically, the basic data for constructing the PCSWMM model of the study area includes:

[0088] Rainfall and waterlogging monitoring data, land use type, drainage network information, building distribution, elevation data, and river water level data.

[0089] Furthermore, a PCSWMM model for the study area was constructed based on the required data, and historical rainfall data was used for calibration and validation to ensure the accuracy of the model simulation, including:

[0090] The land use type map of the study area in CAD format was converted into SHP format using ArcGIS. Based on the elevation, land use type, and distribution of roads and storm drains, it was divided into several sub-catchments. Then, topology processing of drainage pipelines was performed using ArcGIS. After exporting the sub-catchments and pipelines into SHP format, INP files that can be recognized by SWMM were generated using the inpPINS plugin.

[0091] Deterministic parameters and nondeterministic parameters are set for the study area. The deterministic parameters are determined directly based on geographic data, including the area, characteristic width, permeability, pipe diameter, burial depth, and stormwater well depth of the sub-catchment. The nondeterministic parameters are selected based on the SWMM manual and the empirical range of the study area.

[0092] Using the 2D module of the PCSWMM model, elevation data, boundary conditions, and building outlines are input to construct a two-dimensional surface runoff model based on a hexagonal grid; by setting "bottom orifices" to connect the two-dimensional model, bidirectional exchange of water level and flow rate can be achieved.

[0093] The simulation was run, and the coupled model was calibrated and validated using measured water level / flow data. Calibration and validation were performed using measured historical rainfall and water accumulation data from multiple events. The relative error between the simulated maximum surface water depth and the measured water depth at flood-prone points was calculated to verify the accuracy of the PCSWMM model. The formula for the relative error is as follows:

[0094] ;

[0095] In the formula, H m H represents the measured value of water accumulation at the monitoring point. s This represents the simulated value of water accumulation at the monitoring point.

[0096] Optionally, dividing the area into drainage zones and determining LID measures includes:

[0097] The study area is divided into N drainage zones based on the drainage network route and land use type. Appropriate LID measures are selected according to the land use type, and the basic parameters of LID measures are set in the PCSWMM model. The sub-catchment areas for planning and deploying LID measures are selected and the deployment area is calculated.

[0098] Furthermore, a zoning system encompassing natural zoning and LID (Level Identification) measures zoning is constructed, including:

[0099] Drainage zones can be further divided into natural zones and LID (Light Identification and Discharge) zone zones. Sub-catchments without LID measures are defined as natural zones, while sub-catchments with planned LID measures are defined as LID zone zones.

[0100] In N drainage zones, each natural zone within a zone is assigned a specific tracer. When runoff is generated in any marked sub-catchment, the tracer concentration in its effluent remains constant at the source (1 mg / L). This concentration does not change over time and is not attenuated before entering the runoff node (attenuation coefficient = 0). The tracers are named directly as "0, zone number", such as "0,1" representing the tracer "0,1" for the natural zone in zone 1, and "0,N" representing the tracer "0,N" for the natural zone in zone N; there are a total of N tracers in the study area. This system is a natural zone tracer system, used to uniquely identify and track the water source contribution of each drainage zone's natural zone.

[0101] Each drainage zone with planned LID (Limited Identification and Discharge) measures is configured with an independent dedicated tracer system. When runoff is generated in any marked sub-catchment area, the tracer concentration in its effluent remains constant at a set value (1 mg / L) at the source. This concentration does not change over time and is not attenuated before entering the runoff node (attenuation coefficient = 0). The tracer naming rule adopts the format "LID category number, zone number", such as "1,1" representing the dedicated 1,1 tracer for the LID measure zone with the first type of LID measure in the first drainage zone; "M,N" representing the dedicated M,N tracer for the LID measure zone with the Mth type of LID measure in the Nth drainage zone, i.e., there are M types of LID measures and a total of N*M tracers. This system is the LID measure zone tracer system, used to identify and track the hydrological sources and migration paths of different LID measures in each drainage zone.

[0102] Each sub-catchment of the drainage zones within the study area is marked with a tracer. Each drainage zone has M+1 types of source tracers, meaning each drainage zone can be divided into one natural zone and M LID (Limited Indication Discharge) zone. For example, the first drainage zone can be divided into one natural zone (a sub-catchment without LID measures, represented by tracers 0 and 1) and M LID zone (sub-catchments with corresponding LID measures, represented by M specific tracers "1,1", "2,1", ..., "M,1"). The entire study area has N drainage zones and N+N*M types of tracers.

[0103] Specifically, scenarios with and without LID (Low Identification and Discharge) measures were simulated separately, and the tracer contribution matrix and tracer contribution rate matrix were compiled for each scenario. The surface water volume generated by the coupled drainage zones was then calculated, and the surface water contribution matrix and surface water contribution rate matrix for each scenario were calculated, including:

[0104] Drainage zones can serve as both source zones for tracers and water accumulation, as well as receiving zones. Source zone α is defined as the drainage zone where the tracer is initially labeled, representing the source of runoff generation; receiving zone β is defined as the drainage zone where the tracer is ultimately monitored or has an impact, representing the destination of runoff inflow.

[0105] Calculate the tracer contribution matrix for the scenario without LID measures:

[0106] ;

[0107] Where C represents the tracer contribution matrix in the scenario without LID measures. ; represents the tracer contribution (mg) of the natural partitions within the source partition α to the receiving partition β in the absence of LID measures; Let be the tracer contribution (mg) to the receiving partition β from the source partition α, where the i-th type of LID measure will be deployed in the future but has not yet been deployed. α = {1, 2, ..., N}; i = {1, 2, ..., M}; β = {1, 2, ..., N}.

[0108] Tracer contribution rate matrix converted to a scenario without LID measures:

[0109] ;

[0110] Wherein, Cr represents the tracer contribution rate matrix under the scenario without LID measures; This represents the tracer contribution rate of the natural partitions within the source partition α to the receiving partition β in the scenario without LID measures. Let α represent the tracer contribution rate of the source partition α, which is the partition where LID I will be deployed in the future but has not yet been deployed, to the receiving partition β in the scenario without LID measures; where α={1,2,……,N}; i={1,2,……,M}; β={1,2,……,N}.

[0111] Calculate the tracer contribution matrix for the LID (Low Identification and Influence) scenario:

[0112] ;

[0113] Wherein, CL represents the tracer contribution matrix under the LID (Low Identification and Influence) scenario; The value in mg represents the tracer contribution of the un-LID-implemented area (natural area) within the source partition α to the receiver partition β under the LID implementation scenario. Let represent the tracer contribution (mg) of the region (LID measure region) within the source region α where the i-th type of LID measure is deployed to the receiving region β under the LID measure scenario. α = {1, 2, ..., N}; i = {1, 2, ..., M}; β = {1, 2, ..., N}.

[0114] Calculate the tracer contribution rate matrix for the LID (Low Identification and Influence) scenario:

[0115] ;

[0116] in, This represents the tracer contribution rate matrix under the LID (Low Identification and Reduction) scenario. This represents the tracer contribution rate of the natural partitions within the source partition α to the receiving partition β under the LID (Learning Indication Discharge) scenario. Let represent the tracer contribution rate of the region (LID measure region) within the source region α where the i-th type of LID measure is deployed to the receiving region β under the LID measure scenario. Where α={1,2,……,N}; i={1,2,……,M}; β={1,2,……,N}.

[0117] Couple the surface water volume generated by each drainage zone to calculate the surface water contribution matrix in the scenario without LID measures:

[0118] ;

[0119] Among them, F r f represents the water accumulation contribution matrix under the scenario without LID measures; α This represents the surface water volume of source zone α under the scenario without LID measures, in m. 3 ; This represents the surface water volume (m) of the natural sub-regions in source sub-region α relative to the receiving sub-region β in the scenario without LID measures. 3 ; This represents the surface water volume of the i-th LID-measure zone in the source zone α to the receiving zone β under the scenario without LID measures, m. 3 . α = {1, 2, ..., N}, i = {1, 2, ..., M}, β = {1, 2, ..., N}.

[0120] Couple the surface water volume generated by each drainage zone to calculate the surface water contribution matrix under the LID (Low Impact Development) scenario:

[0121] ;

[0122] in, This represents the surface water contribution matrix under LID (Low Impact Development) measures scenario; f α LThis represents the surface water volume in the source zone α after the implementation of LID measures, in meters. 3 ; This represents the surface water volume (m) of the natural sub-regions in source sub-region α relative to the receiving sub-region β under the LID (Low Impact Development) scenario. 3 ; Let m represent the surface water volume of the i-th LID-measure zone in the source zone α for the receiving zone β under the LID-measure scenario. 3 . α={1,2,…,N}, i={1,2,…,M}, β={1,2,…,N}.

[0123] Calculate the matrix of changes in surface water contribution after setting up the LID scenario:

[0124] ;

[0125] Wherein, ΔF represents the matrix of changes in the contribution of surface water accumulation.

[0126] Optionally, the benefits of surface water accumulation generated by the source zone can be decomposed to output the direct and indirect benefits of LID measures, including:

[0127] Calculate the surface water contribution rate of change matrix after setting up LID scenario:

[0128] ;

[0129] Where diag(f) is an N×N diagonal matrix with diagonal elements f α △F(α, β) is the surface water contribution change matrix, representing the change in the contribution of source region α to receiving region β before and after the deployment of LID measures, m 3 ;F v (α, β) represents the change in the contribution of source region α to receiving region β before and after the deployment of LID measures, and is an element of the Fv matrix; Fv represents the surface water contribution change rate matrix; where fα represents the surface water volume of source region α in the scenario without LID measures, m 3 ; α = {1, 2, ..., N}; When fα equals 0, Define it directly as 0.

[0130] The indirect benefits of source partition α under LID measures are defined as the sum of the efficiencies of the natural partitions in source partition α to all receiving partitions β:

[0131] ;

[0132] Among them, D 0,αLet α represent the indirect benefit rate of the source region α; α = {1, 2, ..., N}, i = {1, 2, ..., M}, β = {1, 2, ..., N}.

[0133] The direct benefit of source partition α under LID measures is defined as the sum of the efficiencies of the LID-measured partitions in source partition α to all receiving partitions β:

[0134] ;

[0135] Among them, D i,α Let α represent the direct benefit rate of the i-th LID measure in the source region α; α = {1, 2, ..., N}, i = {1, 2, ..., M}, β = {1, 2, ..., N}.

[0136] As an optional implementation method, the optimized method of this embodiment is applied to the main urban area of ​​a city, and the technical process includes:

[0137] The process includes: collecting and organizing basic data for the PCSWMM model in the study area; constructing the regional PCSWMM model and performing calibration and validation; dividing drainage zones and determining LID measures; constructing the zoning tracer system; quantifying the contribution matrix; and decomposing the benefits. The specific workflow is as follows:

[0138] (1) Collection and organization of basic data for the PCSWMM model in the study area. This includes land use type, 20-year return period 2h design rainfall, etc. The study area is 14.27 km². 2 There are currently 5.76 km 2 Residential area, 3.8 km 2 Commercial land, 0.49 km² 2 Industrial land, 1.95 km² 2 Road land, 0.32 km 2 River system, 1.95 km 2 Green space. The average water depth of the main river channel is approximately 3.2 m. Other specific data sources and accuracy are shown in Table 1. The distribution of land use types and water levels at water accumulation monitoring points in the study area are shown in Table 1. Figure 3 As shown.

[0139] Table 1. Basic data required to build the PCSWMM model

[0140] ;

[0141] (2) Constructing and calibrating the regional PCSWMM model. Using ArcGIS, the land use type map of the study area in CAD format was converted to SHP format and divided into several sub-catchments based on elevation, land use type, road and storm drain distribution. Then, ArcGIS was used to perform topology processing on the drainage pipelines. After exporting the sub-catchments and pipelines into SHP format, the INP file that can be recognized by SWMM was generated through the inpPINS plugin.

[0142] Deterministic parameters and nondeterministic parameters were set for the study area. The deterministic parameters were determined directly based on geographic data, including the area, characteristic width, permeability, pipe diameter, burial depth, and stormwater well depth of the sub-catchment. The nondeterministic parameters were selected based on the SWMM manual and the empirical range of the study area. The results are shown in Table 2.

[0143] Table 2 Values ​​of nondeterministic parameters in the SWMM model

[0144] ;

[0145] Using the 2D module of the PCSWMM model, elevation data, boundary conditions, and building outlines are input to construct a two-dimensional surface runoff model based on a hexagonal grid; by setting a "bottom orifice" to connect the one-dimensional and two-dimensional models, bidirectional exchange of water level and flow rate can be achieved.

[0146] Based on the above steps, a one-dimensional pipeline and river model of the PC SWMM for the study area was first established. According to the study area planning map, it was divided into 1073 sub-catchments, 252 main pipelines, and 19 drainage outlets. The drainage outlets, as rainwater outlets, all flow into the Fuyang River and Qin River, and are generalized as open channels, such as... Figure 2 As shown. The PC SWMM two-dimensional surface inundation model for the study area needs to consider the obstruction of buildings, generating 16278 two-dimensional nodes, 44485 two-dimensional pipes and channels, and 16026 2D meshes. The coupling of the one-dimensional and two-dimensional models is achieved by connecting the two-dimensional nodes to the orifices, as shown. Figure 4 , Figure 5 and Figure 6 As shown.

[0147] This study validated the data based on historical flood distribution and the maximum water depth at typical waterlogging points. Calibration was performed using rainfall events on July 29, 2023, July 24, 2024, and June 26, 2022, while validation was conducted on July 31, 2023, August 6, 2024, and July 5, 2022. Running the SWMM model showed that the flood distribution largely matched the actual flood risk map (provided by the city's meteorological bureau), and the absolute error of the maximum water depth at typical waterlogging points was within 25% (see Table 3).

[0148] Table 3 Simulated and measured values ​​and errors of 8 waterlogging points under historical rainfall events.

[0149] ;

[0150] (3) Division of drainage zones and determination of LID measures. The study area was divided into 9 drainage zones according to the direction of the drainage network. Considering the limited land use in the study area, the space for LID measures was limited. Green roofs were installed on the roofs of buildings in residential and commercial areas, and permeable pavement was installed on the main roads. To compare the benefits of LID measures to different drainage zones, the total area of ​​both measures was 1 km2, and they were evenly distributed in the sub-catchments of each drainage zone according to the area proportion of the drainage zone. Only one LID measure was installed in each sub-catchment. The specific parameters of the LID measures were obtained from the SWMM model manual and relevant literature, as shown in Tables 4 and 5.

[0151] Table 4. LID Parameter Settings for Permeable Pavement

[0152]

[0153] Table 5 LID parameter settings for green roofs

[0154] ;

[0155] 4) Construct a zoning tracer system for natural zones and LID measures. The study area consists of 9 drainage zones (N=9), with 2 types of LID measures deployed (M=2). The 9 drainage zones are further divided into natural zones and LID measure zones. Each natural zone was assigned a unique tracer, resulting in nine natural zones: “0,1”, “0,2”, “0,3”, “0,4”, “0,5”, “0,6”, “0,7”, “0,8”, and “0,9”, forming a natural zone tracer system. Similarly, each sub-catchment area within a green roof measure zone was assigned a unique tracer, resulting in nine green roof measure zones: “1,1”, “1,2”, “1,3”, “1,4”, “1,5”, “1,6”, “1,7”, “1,8”, and “1,9”, forming a green roof measure zone tracer system. Likewise, each sub-catchment area within a permeable pavement measure zone was assigned a unique tracer, resulting in nine permeable pavement measure zones: “2,1”, “2,2”, “2,3”, “2,4”, “2,5”, “2,6”, “2,7”, “2,8”, and “2,9”, forming a permeable pavement measure zone tracer system.

[0156] (5) Quantification of contribution matrix. Based on the PCSWMM simulation results, the tracer contribution matrix and tracer contribution rate matrix were statistically analyzed and organized for the two scenarios with and without LID measures. The surface water volume generated by each drainage zone was coupled to calculate the surface water contribution matrix and surface water contribution change matrix for the two scenarios with and without LID measures.

[0157] (6) Benefit decomposition. The change rate matrix of surface water contribution before and after the implementation of LID measures was calculated using the formula. The sum of the efficiencies of the natural zones in each source zone to the receiving zones was calculated as the indirect benefits, and the sum of the efficiencies of the LID measure zones in each source zone to the receiving zones was calculated as the direct benefits. After statistical analysis and organization, the final results are shown in Tables 6 to 9.

[0158] Table 6 Natural Partition Tracing System

[0159]

[0160] Table 7 Green Roofing Measures Zoning Tracing System

[0161]

[0162] Table 8 Zoning Tracing System for Permeable Pavement Measures

[0163]

[0164] Table 9. Efficiency of each drainage zone

[0165]

[0166] The beneficial effects of this invention are as follows:

[0167] (1) This invention establishes a hydrological benefit assessment system for LID measures oriented towards drainage zones, enabling refined and quantifiable analysis of direct and indirect benefits. Existing assessments mostly focus on overall runoff reduction, making it difficult to distinguish the differences in contribution of different LID units to specific downstream drainage zones, and also making it difficult to separate the effects of LID facilities themselves from the impacts of changes in system hydraulic conditions.

[0168] (2) This invention proposes a technical approach that combines zonal tracing, contribution matrix and benefit decomposition, and configures corresponding numerical tracers for each drainage zone and different LID facilities within it, thereby realizing path tracing and contribution identification from source to sink. On this basis, a contribution matrix that simultaneously covers the natural zonal source and the zonal source of LID measures is constructed, which can quantitatively give the relationship between the contribution amount and contribution rate of any LID measure to the surface water accumulation in any drainage zone.

[0169] (3) Furthermore, this invention decomposes the total benefits into direct and indirect benefits. The direct benefits reflect the reduction effect of the LID measures on the surface water contribution of the zoning itself, while the indirect benefits reflect the changes in the contribution of natural zoning due to the adjustment of hydraulic processes. This method makes up for the shortcomings of traditional assessments in terms of spatial resolution and benefit attribution, and can provide more targeted quantitative basis for the optimization of LID measures, zoning governance decisions, and the coordinated configuration of multiple measures, thereby improving the refinement and scientific level of urban stormwater management.

[0170] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0171] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A zonal tracer assessment method for the direct and indirect hydrological benefits of source tracing LID measures, characterized in that, include: Establish a coupled model of PCSWMM one-dimensional pipeline and river model with two-dimensional surface runoff model; The coupled model was calibrated and validated using historical rainfall data and waterlogging monitoring data to obtain a validated model. Within the study area corresponding to the verification model, the study area is divided into multiple drainage zones according to the drainage network direction and land use type. Within each drainage zone, the natural zones of sub-catchments without LID measures and the LID measure zones of sub-catchments with planned LID measures are determined. Configure tracers for the natural partitions and configure tracers for the LID measure partitions; The drainage zone where the tracer was initially marked is taken as the source zone, and the drainage zone where the tracer was finally monitored or had an impact is taken as the receiving zone. The scenarios without LID measures and the LID measures are simulated respectively to obtain the tracer contribution matrix and tracer contribution rate matrix of the two simulated scenarios, and the surface water volume of each source zone is obtained. The surface water volume is coupled with the tracer contribution matrix, and the surface water contribution matrix and surface water contribution rate matrix for the two scenarios are calculated respectively. The surface water contribution change matrix and surface water contribution change rate matrix are obtained, and the direct and indirect benefits of LID measures are decomposed and output based on the surface water contribution change rate matrix.

2. The method for zonal tracing assessment of the direct and indirect hydrological benefits of source tracing LID measures according to claim 1, characterized in that, Establish a coupled model between the PCSWMM one-dimensional pipeline and river model and the two-dimensional surface runoff model, including: Elevation data, boundary conditions, and building outlines are input into the 2D module of PCSWMM to construct a two-dimensional surface runoff model based on hexagonal grids. By setting bottom orifices to connect the one-dimensional pipe and river model with the two-dimensional surface runoff model, bidirectional exchange of water level and flow rate can be achieved.

3. The method for zonal tracing and evaluation of the direct and indirect hydrological benefits of source tracing LID measures according to claim 1, characterized in that, The coupled model was calibrated and validated using historical rainfall data and waterlogging monitoring data to obtain a validated model, including: Multiple historical rainfall data sessions and corresponding waterlogging monitoring data were selected for calibration and verification. For each rainfall event, the historical rainfall data is input into the coupled model and run to obtain the simulated maximum surface water depth at typical water accumulation points; Extract the measured maximum surface water depth corresponding to the typical water accumulation point from the water accumulation monitoring data; The relative error between the simulated maximum surface water depth and the measured maximum surface water depth is calculated to verify the accuracy of the coupled model.

4. The method for zonal tracing and evaluation of the direct and indirect hydrological benefits of source tracing LID measures according to claim 1, characterized in that, Establishing a coupled model of the PCSWMM one-dimensional pipeline and river model with the two-dimensional surface runoff model also includes: The land use type map of the study area was converted from CAD format to SHP format in layers, and divided into several sub-catchment areas based on elevation data, the land use type map, and the distribution of roads and storm drains; Topology processing is performed on the drainage pipelines, and the sub-catchment areas and drainage pipelines are exported as SHP format. An INP file that can be recognized by SWMM is generated through the inpPINS plugin to establish the one-dimensional pipeline and river model.

5. The method for zonal tracing assessment of the direct and indirect hydrological benefits of source tracing LID measures according to claim 1, characterized in that, The steps for calibration and verification include: Deterministic parameters and nondeterministic parameters are set, wherein the deterministic parameters are determined based on geographic data; the deterministic parameters include the area of ​​the sub-catchment, characteristic width, permeability, pipe network diameter, burial depth, and stormwater well depth; The values ​​of the calibration nondeterministic parameters are determined based on the SWMM manual and the empirical range of the study area, and these calibration nondeterministic parameters are used as the adjustment objects for calibration and verification; the calibration nondeterministic parameters include Manning coefficient, depression storage capacity and Horton infiltration parameter.

6. The method for zonal tracing and evaluation of the direct and indirect hydrological benefits of source tracing LID measures according to claim 1, characterized in that, Within the study area corresponding to the verification model, the study area is divided into multiple drainage zones according to the drainage network orientation and land use type. Within each drainage zone, natural zones of sub-catchments without LID (Light Identification and Discharge) measures and LID measure zones of sub-catchments planned to have LID measures are determined, including: The boundaries of each drainage zone are determined based on the pipeline route and confluence path of the drainage network, and each sub-catchment area within the study area is merged into the corresponding drainage zone according to the drainage zone into which the runoff flows. The type of LID (Land Use Implementation) measure is determined based on the land use type of the sub-catchment area; In the coupled model, the basic parameters of the LID measures are set for the LID measure type; the basic parameters of the LID measures are the parameters required by the coupled model to perform hydrological process simulation on the LID measure zoning under the LID measure scenario, so that the coupled model can output the surface water volume of each source zoning under the LID measure scenario, as well as the tracer contribution matrix and the tracer contribution rate matrix; Within each drainage zone, select the sub-catchment area from the sub-catchment areas to plan and deploy LID measures, and determine the deployment area. Sub-catchment areas that were not selected for the planning and deployment of LID measures were identified as the natural zones, and sub-catchment areas that were selected for the planning and deployment of LID measures were identified as the LID measure zones.

7. The method for zonal tracing and evaluation of the direct and indirect hydrological benefits of source tracing LID measures according to claim 1, characterized in that, Configuring tracers for the natural partitions and for the LID measure partitions, including: For each natural zone within the aforementioned drainage zone, a tracer for that natural zone is configured and named according to "0, zone number"; For each drainage zone, a tracer corresponding to the LID measure type is configured for the LID measure zone, and named according to "LID category number, zone number"; the number of LID measure types corresponding to the LID category number is M, so as to form tracers of N types of natural zones and tracers of N×M types of LID measure zones in the study area; Tracer labeling is performed on each of the sub-catchments, and the labeling rules are as follows: sub-catchments of natural zones are labeled with tracer labels of natural zones, and sub-catchments of LID zone are labeled with tracer labels of LID zone. The source concentration of tracer at the outlet of the marked sub-catchment area is set to a constant value of 1 mg / L, and the source concentration is kept consistent in both the no-LID and LID scenarios. The attenuation coefficient is set to 0 to ensure that the tracer does not attenuate before entering the confluence node, and to maintain the attenuation coefficient consistent in both the no-LID and LID scenarios; the source concentration and the attenuation coefficient are used to ensure that tracer signals from different partitions can be used to construct the tracer contribution matrix and the tracer contribution rate matrix.

8. The method for zonal tracing and evaluation of the direct and indirect hydrological benefits of source tracing LID measures according to claim 1, characterized in that, The drainage zone where the tracer was initially labeled is designated as the source zone, and the drainage zone where the tracer was ultimately monitored or had an impact is designated as the receiving zone. Simulations were performed for both the no-LID (Low-Intensity Discharge) and LID (Low-Intensity Discharge) scenarios to obtain the tracer contribution matrix and tracer contribution rate matrix for both scenarios. The surface water accumulation in each source zone was also obtained, including: In the coupling model, the drainage zone where the tracer is initially tagged is defined as the source zone, the drainage zone where the tracer is ultimately monitored or has an effect is defined as the receiving zone, and each drainage zone is simultaneously used as both a source zone and a receiving zone. Run the scenarios without LID measures and with LID measures respectively, and output the tracer contribution from natural partitions to each receiving partition within each source partition, as well as the tracer contribution from each LID-measured partition to each receiving partition within each source partition. A tracer contribution matrix for a scenario without LID measures is constructed based on the tracer contribution output in the scenario without LID measures, and a tracer contribution matrix for a scenario with LID measures is constructed based on the tracer contribution output in the scenario with LID measures; the matrix elements of the tracer contribution matrix are the tracer contribution of the natural partition within the source partition or the LID measure partition within the source partition to the receiving partition. The tracer contribution matrix for the no-LID scenario is normalized according to the total tracer amount in the receiving zone to obtain the tracer contribution rate matrix for the no-LID scenario, and the tracer contribution matrix for the LID scenario is normalized according to the total tracer amount in the receiving zone to obtain the tracer contribution rate matrix for the LID scenario. In the simulation outputs of both the LID (Low Identification and Discharge) scenario and the LID scenario, the surface water volume of each source zone is extracted; the surface water volume of each source zone is used to calculate the surface water contribution matrix and the surface water contribution rate matrix.

9. The method for zonal tracing and evaluation of the direct and indirect hydrological benefits of source tracing LID measures according to claim 1, characterized in that, Couple the surface water volume with the tracer contribution matrix, calculate the surface water contribution matrix and surface water contribution rate matrix for both scenarios, and obtain the surface water contribution change matrix and surface water contribution change rate matrix, including: The surface water volume of each source area under the scenario without LID measures and the surface water volume of each source area under the scenario with LID measures were obtained respectively. For the scenario without LID measures, the surface water volume of each source zone under the scenario without LID measures is coupled with the tracer contribution rate matrix of the scenario without LID measures to obtain the surface water contribution matrix of the scenario without LID measures. The matrix elements of the surface water contribution matrix are the surface water contribution of the natural zone or the LID-measure zone within the source zone to the receiving zone. The surface water contribution matrix of the scenario without LID measures is normalized according to the total surface water volume of the receiving zone to obtain the surface water contribution rate matrix of the scenario without LID measures. For the LID (Low-Intensity Discharge) scenario, the surface water volume of each source zone under the LID scenario is coupled with the tracer contribution rate matrix of the LID scenario to obtain the surface water contribution matrix of the LID scenario. The surface water contribution matrix of the LID measures scenario is normalized according to the total surface water volume of the receiving zone to obtain the surface water contribution rate matrix of the LID measures scenario. The surface water contribution change matrix is ​​obtained by subtracting the surface water contribution matrix under the LID (Low Identification and Discharge) scenario from the surface water contribution matrix under the LID scenario. Normalize the matrix of changes in the contribution of surface water volume to surface water under the scenario without LID measures to obtain the matrix of changes in the contribution rate of surface water. When the surface water volume of the source zone is 0 in the scenario without LID measures, the change rate corresponding to the source zone in the surface water contribution change rate matrix is ​​defined as 0.

10. The method for zonal tracing assessment of the direct and indirect hydrological benefits of source tracing LID measures according to claim 1, characterized in that, Based on the decomposition of the surface water contribution change rate matrix, the direct and indirect benefits of LID measures are output, including: For each source zone, the sum of the rate of change of the contribution of natural zones to the surface water of all receiving zones is calculated, and the sum of the rate of change of the contribution of natural zones to the surface water of all receiving zones is defined as the indirect benefit of the source zone. For each source zone, the sum of the rate of change of the contribution of each LID measure zone to the surface water of all receiving zones is calculated, and the sum of the rate of change of the contribution of each LID measure zone to the surface water of all receiving zones is defined as the direct benefit of the source zone. The direct benefits of LID measures in the study area are obtained by summing the direct benefits of each source area, and the indirect benefits of LID measures in the study area are obtained by summing the indirect benefits of each source area.

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