Method for determining the position of a monitoring point in a municipal drainage system

Abstract

The present application relates to the technical field of urban drainage monitoring, and particularly relates to a method for determining the position of a monitoring point in a city drainage system. The method comprises the following steps: collating the connection topology of the drainage pipe network to obtain a directed pipe network connected by pipes and inspection wells, and dividing the pipes into pipe grades based on pipe diameter; along the water flow direction, marking the inspection wells with a higher pipe grade in the downstream than the highest grade of each upstream pipe as a confluence candidate point, marking the inspection wells with more than one outflow pipe as a split candidate point, and the confluence candidate points and the split candidate points forming structural candidate points; for each structural candidate point, tracing back to the adjacent previous structural candidate point, the source of the pipe network or the partition boundary in the reverse direction of the water flow, taking the number of pipe sections covered by the backtracking path as the upstream control number of the structural candidate point, and assigning a structural level. The present application can determine the position of the monitoring point according to the pipe network topology and the pipe diameter, and the layout density of the monitoring point changes with the pipe network structure, thereby supplementing the coverage while reducing the number of points.

Description

Technical Field

[0001] This invention relates to the field of urban drainage monitoring technology, and in particular to a method for determining the location of monitoring points in an urban drainage system. Background Technology

[0002] Urban drainage systems typically operate on a zone-by-zone basis. A single zone contains drainage facilities such as manholes, pipes, pumping stations, and sluice gates, and faces various operational challenges, including waterlogging, high water levels in pipes, low water quality concentration, and infiltration of external water. To monitor the operational status of the drainage system, monitoring equipment for water level, flow rate, and water quality needs to be deployed at key locations within the network. The accuracy of these monitoring point locations is crucial for obtaining representative operational data and also affects the investment required in the construction of monitoring facilities.

[0003] The current methods for determining the location of monitoring points in drainage networks either rely on subjective experience, actual monitoring data, or pre-established hydraulic models. Operational issues in drainage systems, such as waterlogging, high water levels, external water infiltration, and low water concentration, are typically considered as independent factors and simply superimposed in existing site selection methods. However, these operational issues are interconnected. For example, external water infiltration increases the water volume in a pipe section while diluting the sewage and lowering its concentration; the increased water volume and low concentration are actually caused by the same external water factor. Treating these interconnected operational issues as independent factors leads to the repeated accounting of the same cause, affecting the accuracy of site selection in reflecting the network's operational problems. Summary of the Invention

[0004] Therefore, the present invention needs to provide a method for determining the location of monitoring points in an urban drainage system to solve at least one of the above-mentioned technical problems.

[0005] To achieve the above objectives, a method for determining the location of monitoring points in an urban drainage system includes the following steps: Step S1: Organize the connection topology of the drainage pipe network to obtain the directed pipe network connected by pipes and inspection wells, and classify each pipe into pipe class based on pipe diameter; Step S2: Along the water flow direction, mark the manholes with downstream pipe grades higher than the highest grades of each upstream pipe as confluence candidate points, and mark the manholes with more than one outflow pipe as diversion candidate points. The confluence candidate points and diversion candidate points constitute structural candidate points. Step S3: For each structural candidate point, backtrack along the reverse direction of water flow to the adjacent prior structural candidate point, pipeline source, or zone boundary. The number of pipe segments covered by the backtracking path is used as the upstream control number of the structural candidate point, and a structural level is assigned. Step S4: Overlay the pre-acquired operational risk areas onto the directed pipeline network to obtain pre-risk candidate points, and detect the water quality and upstream responsibility section and confluence relationship of each structural candidate point to determine additional risk candidate points. Use the pre-risk candidate points and additional risk candidate points together as risk candidate points. Step S5: Merge the overlapping areas of structural candidate points and risk candidate points into monitoring candidate points. Count the number of different types of placement reasons for each monitoring candidate point as the overlap degree. Select monitoring points from high to low overlap degree. For those with the same overlap degree, select the one with the higher structural level and upstream control number in turn. Add points where the route distance between adjacent monitoring points exceeds the upper limit of the corresponding pipe segment.

[0006] This invention determines monitoring point locations based on two fundamental data points already available during the design and construction phases: the connection topology of the drainage network and the pipe diameter. This eliminates the need for measured flow rate and water quality data, as well as the need for pre-established and calibrated hydraulic models. While pipe grades are typically used only to describe pipe specifications, this method reveals that their elevation along the flow direction indicates significant water convergence, thus identifying confluence candidate points. Furthermore, the network is divided into non-overlapping upstream responsibility sections using adjacent candidate points as boundaries. The number of pipe segments within each responsibility section serves as the upstream control number, allowing the size of the upstream area represented by each candidate point to be measured solely from the topology. By comparing the upstream control number with the downstream pipe grade, locations with nominally large catchment areas but smaller actual flow volumes can be identified, enabling the discovery of some operational anomalies directly from the network data without actual measurement.

[0007] This invention categorizes the reasons for monitoring point placement into independent categories based on their causes before counting, ensuring that reasons caused by the same factor, such as confluence and diversion, external water infiltration, and low water concentration, are not counted repeatedly. Compared to simply adding up operational problems as independent factors, the overlap reflects the number of non-overlapping causes at a given location, preventing the overestimation of locations with a single cause and prioritizing locations pointed to by multiple different reasons. Therefore, the monitoring point locations determined by this invention are objective and reproducible, yielding consistent results for the same pipe network without relying on personnel experience. Furthermore, by setting upper limits for spacing based on pipe grade and prioritizing existing high-overlap candidate points when supplementing coverage, the monitoring point density adapts to changes in the pipe network structure, reducing wasted monitoring points while ensuring adequate coverage. Attached Figure Description

[0008] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 A flowchart illustrating the steps involved in determining the location of monitoring points in an urban drainage system; Figure 2 This is a schematic diagram of a drainage zoning example; Figure 3 This is a schematic diagram of the upstream control number and upstream responsible section in one embodiment. Detailed Implementation

[0009] The technical method of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0010] Furthermore, the accompanying drawings are merely illustrative of the invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor methods and / or microcontroller methods.

[0011] It should be understood that although the terms "first," "second," etc., may be used herein to describe various units, these units should not be limited by these terms. These terms are used merely to distinguish one unit from another. For example, without departing from the scope of the exemplary embodiments, a first unit may be referred to as a second unit, and similarly, a second unit may be referred to as a first unit. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0012] To achieve the above objectives, please refer to Figures 1 to 3 This invention provides a method for determining the location of monitoring points in an urban drainage system, the method comprising the following steps: Step S1: Organize the connection topology of the drainage pipe network to obtain the directed pipe network connected by pipes and inspection wells, and classify each pipe into pipe class based on pipe diameter; In one embodiment, sorting out the connection topology of the drainage pipe network refers to organizing the interconnected relationships between the manholes based on the pipeline routes, the manhole markings at both ends of each pipe, the pipe diameter and material, and the locations of facilities such as pumping stations and sluice gates, thus obtaining a pipe network formed by connecting pipes and manholes. Because the drainage system operates under gravity, sewage flows from higher to lower elevations and eventually converges at pumping stations or sewage treatment plants, the water flow in each pipe has a definite direction. Accordingly, each pipe in the network is assigned a direction from upstream manhole to downstream manhole, making the network a directed network. In this directed network, for each manhole, the pipe connected to it and into which water flows is the upstream pipe, and the pipe connected to it and into which water flows is the downstream pipe. This allows for tracing and searching the network along the direction of water flow or in the opposite direction in subsequent steps.

[0013] For example, for a pipeline that flows from manhole J1 through a pipe to manhole J2, and then from manhole J2 through a pipe to manhole J3, after sorting, we get a directed connection relationship where J1 points to J2 and J2 points to J3. For manhole J2, the pipe from J1 is its upstream pipe, and the pipe leading to J3 is its downstream pipe.

[0014] Furthermore, step S1, which classifies pipes based on pipe diameter, includes: Obtain the nominal inner diameter of each pipe and divide the pipes into main pipes, branch pipes, and collection pipes according to the preset pipe diameter range; The diameter of the main pipe is greater than the first threshold, the diameter of the branch pipe is between the second threshold and the first threshold, the diameter of the branch pipe is between the third threshold and the second threshold, and the diameter of the collection pipe is less than the third threshold. The main pipe and trunk pipe are classified as high-level sections, while the branch pipes and collection pipes are classified as low-level sections.

[0015] In one embodiment, the pipe diameter range is divided by a first threshold, a second threshold, and a third threshold, where the first threshold is greater than the second threshold, and the second threshold is greater than the third threshold. When the nominal inner diameter of a pipe is greater than the first threshold, it is classified as a main pipe; when its nominal inner diameter is between the second and first thresholds, it is classified as a branch pipe; when its nominal inner diameter is between the third and second thresholds, it is classified as a collection pipe. The four pipe grades reflect the increasing flow scale from collection to convergence to transfer in the drainage system; the larger the pipe diameter, the greater the flow scale it handles and the higher its grade in the pipe network.

[0016] For example, if the first threshold is 1500 mm, the second threshold is 1000 mm, and the third threshold is 600 mm, then pipes with a nominal inner diameter of 1800 mm are classified as main pipes, pipes with a nominal inner diameter of 1200 mm are classified as branch pipes, pipes with a nominal inner diameter of 800 mm are classified as branch pipes, and pipes with a nominal inner diameter of 400 mm are classified as collection pipes.

[0017] It should be noted that the nominal inner diameter of drainage pipes in engineering is usually a discrete series of specifications, such as 300 mm, 400 mm, 500 mm, 600 mm, 800 mm, 1000 mm, 1200 mm, 1500 mm, and 1800 mm, with intervals between adjacent specifications. The first, second, and third thresholds are values ​​falling between adjacent specifications, ensuring that the nominal inner diameter of each pipe is not exactly equal to any one of the thresholds, thus uniquely assigning each pipe to a single pipe class and preventing situations where the classification is unclear. The specific values ​​of the first, second, and third thresholds can be determined based on the specification distribution and design specifications of drainage pipes in the local area, and are not limited to the example values ​​mentioned above.

[0018] In one embodiment, the main pipeline and trunk lines primarily function to transfer sewage to pumping stations or sewage treatment plants, handling a large flow volume; therefore, the pipelines to which the main pipelines and trunk lines belong are classified as high-grade sections. Branch pipes and collection pipes primarily function to collect sewage along their routes, handling a smaller flow volume; therefore, the pipelines to which the branch pipes and collection pipes belong are classified as low-grade sections. This division into high-grade and low-grade sections allows subsequent steps, such as determining whether a location is on the backbone of the pipeline network and determining the density of monitoring points, to be based on whether the pipeline at that location belongs to a high-grade section.

[0019] For example, if the downstream pipe of a manhole is a main pipe, the downstream pipe belongs to a high-grade section; if the downstream pipe of a manhole is a branch pipe, the downstream pipe belongs to a low-grade section.

[0020] Step S2: Along the water flow direction, mark the manholes with downstream pipe grades higher than the highest grades of each upstream pipe as confluence candidate points, and mark the manholes with more than one outflow pipe as diversion candidate points. The confluence candidate points and diversion candidate points constitute structural candidate points. In one embodiment, each manhole in the directed pipe network is examined along the water flow direction to identify key locations where water flow converges or redistributes within the network. The basic rationale is that sewage in a drainage network flows from upstream to downstream, with tributaries continuously flowing in along the route, resulting in a gradual increase in cumulative flow along the flow direction. Since the pipe diameter is selected based on its designed flow rate, pipes with higher cumulative flow have larger diameters and belong to higher pipe classifications.

[0021] When water flow significantly converges at a manhole, the cumulative flow downstream of that manhole is significantly greater than that of any upstream pipe, often resulting in the downstream pipe having a higher grade than the upstream pipe. Conversely, when water flow branches into multiple downstream pipes at a manhole, that manhole represents a flow redistribution point. Convergence points are identified by whether the downstream pipe grade is higher than the upstream grade, and redistribution points are identified by whether there is more than one outflowing pipe.

[0022] Furthermore, step S2 includes the following steps: Step S21: Using each inspection well as a node, determine all upstream pipes flowing into the node and all downstream pipes flowing out of the node; In one embodiment, each manhole in the directed pipeline network is taken as a node, and all upstream pipes and all downstream pipes of the manhole are determined according to the directed connection relationship, wherein the upstream pipes are the pipes through which water flows into the manhole, and the downstream pipes are the pipes through which water flows out of the manhole.

[0023] For example, for a manhole, if water flows into the manhole from two pipes and flows out of the manhole from one pipe, then the two pipes that flow into the manhole are its upstream pipes, and the pipe that flows out of the manhole is its downstream pipe.

[0024] Step S22: Select the pipe with the highest grade among all upstream pipes as the upstream benchmark grade for the inspection well; In one embodiment, the pipe with the highest grade among the upstream pipes of the manhole is taken as the upstream benchmark grade of the manhole. The reason for taking the highest grade among the upstream pipes as the benchmark is that whether the downstream grade of the manhole is raised due to confluence should be judged relative to the largest tributary among its upstream branches. Only when the downstream grade is higher than the highest among the upstream branches does it indicate that the downstream flow scale after confluence exceeds that of any single upstream branch.

[0025] For example, if a manhole has two upstream pipes, one of which is a branch pipe and the other is a main pipe, then the grade of the main pipe shall be taken as the upstream benchmark grade of the manhole.

[0026] Step S23: Compare the pipe grade of each downstream pipe flowing out of the manhole with the upstream benchmark grade. When there is a downstream pipe with a higher pipe grade than the upstream benchmark grade, mark the manhole as a candidate confluence point. In one embodiment, the pipe grade of each downstream pipe flowing out of the manhole is compared with the upstream benchmark grade of the manhole. If any downstream pipe has a higher pipe grade than the upstream benchmark grade, it indicates that the downstream flow volume after confluence through the manhole is significantly larger than any upstream tributary, and the manhole is marked as a candidate confluence point. Comparing each downstream pipe separately ensures that, when the manhole has multiple downstream pipes, the confluence can be identified as long as the grade of any one of the downstream pipes is higher than that of the upstream pipe.

[0027] For example, if the upstream baseline grade of a manhole is a branch pipe and its downstream pipeline is a main pipe, and the grade of the main pipe is higher than that of the branch pipe, then the manhole is marked as a confluence candidate point.

[0028] Step S24: When the pipeline grade of all downstream pipelines is not higher than the upstream benchmark grade, they are not marked as confluence candidate points.

[0029] In one embodiment, the manhole is not marked as a confluence candidate if the pipe class of all downstream pipes is not higher than the upstream baseline class. This situation indicates that although there may be branch pipes flowing into the manhole, the downstream pipe class does not increase after the confluence, and the water flow at this location is insufficient to cause the flow volume to exceed the pipe class, thus it is not considered a confluence candidate.

[0030] For example, if the upstream baseline level of a manhole is a main pipe, and a branch pipe merges into it, and its downstream pipe is still a main pipe, and the downstream level is not higher than the upstream baseline level, then the manhole will not be marked as a confluence candidate point.

[0031] Furthermore, step S2 also includes the following steps: Step S25: Count the number of downstream pipes flowing out of the inspection well. When the number is more than one, mark the inspection well as a diversion candidate point. The diversion candidate point corresponds to the flow redistribution location of the interception well, diversion well or overflow well. In one embodiment, the number of downstream pipes flowing out of the manhole is counted. When there is more than one downstream pipe, it indicates that the water flow has split into multiple destinations at the manhole, resulting in a redistribution of flow. The manhole is then marked as a candidate diversion point. In engineering, these candidate diversion points typically correspond to the locations of facilities such as intercepting wells, diversion wells, or overflow wells. These locations are crucial for the operation scheduling and overflow control of the drainage system, as they distribute incoming water to different downstream pipes during dry and rainy seasons or under different operating conditions.

[0032] For example, if a manhole has one upstream pipe flowing into it and two downstream pipes that direct the water flow to a cutoff pipe and an overflow pipe respectively, and two outlet pipes, then the manhole is marked as a candidate diversion point.

[0033] Step S26: When a manhole is simultaneously marked as a confluence candidate point and a diversion candidate point, it is marked as a confluence-diversion composite point; In one embodiment, when a manhole simultaneously meets the marking conditions for both a confluence candidate point and a diversion candidate point, the manhole is marked as a confluence-diversion composite point. This type of manhole is characterized by both the downstream grade increasing due to water convergence at this point and the redistribution of water due to the branching of multiple downstream pipes; it is a location where water first converges and then redistributes.

[0034] For example, if a manhole has multiple upstream pipelines converging and the downstream grade increases after convergence, and at the same time branches out into two downstream pipelines for transfer and overflow, then the manhole is both a candidate point for convergence and a candidate point for diversion, and is marked as a convergence and diversion composite point.

[0035] Step S27: Combine the confluence candidate points, the branching candidate points, and the confluence-branching composite points to form the structural candidate points.

[0036] In one embodiment, confluence candidate points, branch candidate points, and confluence-branch composite points are collectively constituted as structural candidate points. These serve as a set of key locations where water flow converges or redistributes, identified based on the network topology and pipeline grade. This set is used in subsequent steps to determine upstream control numbers, assign structural levels, and calculate overlap.

[0037] For example, for a drainage zone, the several confluence candidate points, diversion candidate points, and confluence-diversion composite points obtained after processing together constitute the structural candidate points of the drainage zone.

[0038] It should be noted that confluence candidate points reflect the convergence of water flow and the increase in flow scale at that point, while diversion candidate points reflect the divergence of water flow into multiple destinations and redistribution at that point. The two are identified separately based on different topological features. A manhole can be only a confluence candidate point, only a diversion candidate point, or both and thus become a confluence-diversion composite point.

[0039] Step S3: For each structural candidate point, backtrack along the reverse direction of water flow to the adjacent prior structural candidate point, pipeline source, or zone boundary. The number of pipe segments covered by the backtracking path is used as the upstream control number of the structural candidate point, and a structural level is assigned. In one embodiment, two attributes are determined for each candidate structural point: the upstream control number and the structural level. The upstream control number measures the size of the upstream pipeline range represented by the candidate structural point alone, while the structural level measures the importance of the candidate structural point's position within the pipeline network. A segment of the pipeline between two adjacent candidate structural points is represented solely by the downstream candidate structural point, as the incoming water ultimately converges at that downstream candidate structural point. The larger the pipeline range represented by the candidate structural point, the wider the upstream area affected by any anomaly, and the higher its monitoring value. By tracing back along the reverse direction of water flow, the upstream range represented by each candidate structural point is determined, and the number of pipe segments contained within that range is used as the upstream control number.

[0040] Furthermore, step S3 includes: For each candidate structural point, backtrack along the reverse direction of water flow until one of the following is encountered: an adjacent prior candidate structural point, a pipeline source, or a zone boundary. The first one encountered is taken as the upper limit of the upstream responsibility section of the candidate structural point, forming a backtracking path. The pipeline source is the initial inspection well with no upstream pipeline inflow, and the zone boundary is the outer edge of the drainage zone's catchment area. In one embodiment, for each structural candidate point, the process proceeds upstream segment by segment along the opposite direction of the water flow from the structural candidate point until one of the following is encountered: an adjacent prior structural candidate point, the source of the pipeline network, or the boundary of the zone. The first one encountered is taken as the upper limit of the upstream responsibility segment of the structural candidate point, and the pipeline segment traversed from the structural candidate point to the upper limit constitutes the backtracking path of the structural candidate point.

[0041] Among them, the source of the pipeline network is the initial inspection well in the directed pipeline network where there is no upstream pipeline flowing in, that is, there is no more upstream water inflow node at this point; the zone boundary is the outer edge of the catchment area of ​​the drainage zone, and tracing back to this point means reaching the end of the traceable range of this drainage zone, and no further tracing back to the adjacent drainage zone is allowed beyond the boundary.

[0042] For example, starting from a certain confluence candidate point, the pipes are traced back in the opposite direction. After passing through several pipe segments, another adjacent upstream structural candidate point is encountered, and the process stops at that adjacent structural candidate point. The pipe segments traversed from the confluence candidate point to the adjacent structural candidate point constitute the backtracking path.

[0043] The pipeline network is divided into upstream responsibility segments, each uniquely belonging to a single candidate structural point, by using the candidate structural point as the boundary between adjacent candidate structural points. The backtracking paths of adjacent candidate structural points do not overlap. In one embodiment, since the backtracking of each structural candidate point stops at its upstream adjacent prior structural candidate point, the backtracking paths of two adjacent structural candidate points are connected and do not overlap. Thus, the entire pipeline network is divided into several segments by the structural candidate points, and each segment uniquely belongs to one downstream structural candidate point, referred to as the upstream responsibility segment of that structural candidate point. This division ensures that each upstream pipeline segment is counted by only one structural candidate point, avoiding the same pipeline segment being represented repeatedly by multiple structural candidate points.

[0044] For example, if there are structural candidate points P1, P2, and P3 along a pipeline from upstream to downstream, then the pipe segment between P1 and P2 belongs to P2, and the pipe segment between P2 and P3 belongs to P3, and the segments do not overlap.

[0045] The number of pipe segments covered by the backtracking path to which the candidate structure point belongs is used as the upstream control number of the candidate structure point.

[0046] In one embodiment, the number of pipe segments covered by the backtracking path to which the candidate structure belongs is used as the upstream control number of the candidate structure. The larger the upstream control number, the more pipe segments the candidate structure alone represents and the larger the range of the upstream pipeline network it represents.

[0047] For example, if the backtracking path of a candidate structure point passes through five pipe segments between itself and its upstream neighboring candidate structure point, then the upstream control number of the candidate structure point is five.

[0048] Furthermore, step S3 also includes: When the backtracking path passes through a diversion candidate point or a confluence-diversion composite point and bifurcation occurs, backtracking is continued only along the branch with the higher pipeline grade, so that the upstream responsibility segment at the bifurcation point is uniquely assigned to the structural candidate point downstream along the main transfer path, thus avoiding the same upstream pipe segment being repeatedly counted in the upstream control number of different structural candidate points. In one embodiment, when the tracing path bifurcates at a branching candidate point or a confluence-branching junction, indicating multiple upstream routes, the tracing continues only along the branch with the higher pipeline priority, excluding the others. The reason for tracing along the higher pipeline priority is that it represents the main transfer path after the confluence, carrying the representative flow from that point. This ensures that the upstream section of responsibility at the bifurcation point is uniquely assigned to a structural candidate point downstream along that main transfer path, thus preventing the same segment of the pipeline upstream of the bifurcation point from being assigned to multiple structural candidate points and thus being repeatedly counted in the upstream control number.

[0049] For example, if a candidate diversion point has two upstream routes, one is a main pipe and the other is a branch pipe, then the backtracking continues along the main pipe branch, and the branch pipe branch is no longer included in the backtracking path of the candidate structural point downstream along the main transfer path.

[0050] When the downstream pipeline of a confluence candidate point belongs to a high-level section, it is assigned a high-level grade; otherwise, it is assigned a low-level grade. For diversion candidate points, a high-level grade is assigned. In one embodiment, structural candidate points are assigned structural levels. For confluence candidate points, a high-level level is assigned if the downstream pipeline belongs to a high-level section, otherwise a low-level level is assigned. That is, confluence points that occur on the main pipeline or the transfer backbone to which the main pipeline belongs are assigned a high-level level, while those that occur on the branch pipeline or the collection pipeline section to which the collection pipeline belongs are assigned a low-level level. For diversion candidate points, a high-level level is uniformly assigned because they correspond to key locations for flow redistribution such as interception, diversion, or overflow.

[0051] For example, if the downstream pipeline of a candidate confluence point is a main pipe and the main pipe belongs to a high-level section, then the candidate confluence point is assigned a high-level status; if the downstream pipeline of a candidate confluence point is a branch pipe and the branch pipe belongs to a low-level section, then the candidate confluence point is assigned a low-level status.

[0052] The higher of the levels obtained by taking the confluence and branching points as confluence candidate points and the levels obtained as branching candidate points is taken as the structural level.

[0053] In one embodiment, a convergence and divergence point has both a hierarchy obtained as a convergence candidate point and a hierarchy obtained as a divergence candidate point. The higher of the two is taken as the structural hierarchy of the convergence and divergence point to avoid underestimating the key position that has both convergence and redistribution functions due to identity selection.

[0054] For example, if a certain confluence and branching point is a candidate point for confluence and thus a low-level point because its downstream pipeline is a branch pipe, and a candidate point for branching and thus a high-level point, then the high-level point is taken as the structural level of the confluence and branching point.

[0055] Step S4: Overlay the pre-acquired operational risk areas onto the directed pipeline network to obtain pre-risk candidate points, and detect the water quality and upstream responsibility section and confluence relationship of each structural candidate point to determine additional risk candidate points. Use the pre-risk candidate points and additional risk candidate points together as risk candidate points. In one embodiment, in addition to the structural candidate points obtained based on the pipeline network topology and pipeline grade, water quality is further detected at the structural candidate points, and additional risk candidate points are determined based on the operational anomalies reflected by the water quality. The risk candidate points include two sources: one part is pre-risk candidate points obtained based on pre-acquired operational risk areas, and the other part is additional risk candidate points discovered based on water quality detection.

[0056] Furthermore, step S4 includes the following steps: Step S41: Overlay the pre-acquired operational risk areas of waterlogging, high water level, external water infiltration, and low water quality concentration onto the directed pipe network, and mark the inspection wells that fall into the operational risk areas as pre-risk candidate points. In one embodiment, pre-identified operational risk areas, including those related to waterlogging, high water levels, external water infiltration, and low water quality concentration, are superimposed onto the directed pipe network, and manholes falling within these operational risk areas are marked as pre-risk candidate points. These operational risk areas can be pre-determined based on historical operational data of the drainage system.

[0057] For example, if a manhole falls into a high-water-level operating area, it will be marked as a pre-risk candidate point.

[0058] Step S42: Install water quality testing devices at the inspection wells corresponding to each candidate structural point to test the conductivity, total dissolved solids, characteristic pollutants, and turbidity of the wastewater at the candidate structural point. The conductivity and total dissolved solids represent the mixing of clean water from outside the water source, the characteristic pollutants represent the access of a specific discharge source, and the turbidity represents the scouring and suspension of sediments in the pipeline. In one embodiment, a water quality testing device is installed at the inspection well corresponding to each candidate structural point to detect the conductivity, total dissolved solids, characteristic pollutants, and turbidity of the wastewater at that candidate structural point. The above water quality indicators are chosen because each indicator represents a different abnormal operating mechanism: when external water infiltrates, the infiltrated groundwater or clean water has a low concentration and low salinity, which will cause a decrease in the conductivity and total dissolved solids of the wastewater; therefore, conductivity and total dissolved solids are used to characterize the mixing of clean water from external sources. When unconventional discharges are connected, industrial wastewater or specific discharge sources bring in specific pollutants; therefore, characteristic pollutants are used to characterize the connection of specific discharge sources. When sediments in the pipeline are suspended under the scouring of water flow, the turbidity of the water increases; therefore, turbidity is used to characterize the scouring and suspension of sediments in the pipeline.

[0059] For example, the water quality testing device can be an online water quality monitoring device for the pipeline network to test the above-mentioned water quality indicators.

[0060] Step S43: When conductivity and total dissolved solids decrease together while turbidity remains unchanged, it is determined to be external water infiltration; when only characteristic pollutants increase, it is determined to be unconventional discharge access; when only turbidity increases while conductivity and total dissolved solids remain unchanged, it is determined to be pipeline sedimentation and scouring or cross-connection; thus determining the type of water quality anomaly. In one embodiment, the water quality anomaly type of the candidate structural point is determined based on the coordinated change patterns of various water quality indicators. Different operational anomalies can cause multiple water quality indicators to change in different combinations, exhibiting their own unique change patterns.

[0061] In one embodiment, infiltration is defined as the infiltration of external water when the conductivity and total dissolved solids decrease together while the turbidity remains unchanged. This is based on the fact that the groundwater or clean water brought in by external water infiltration has low salt content and few dissolved substances. When mixed in, it will simultaneously lower the conductivity and total dissolved solids of the wastewater, causing both to decrease together. In contrast, the infiltration brings in clean water with low dissolved solids and does not bring in suspended particles, so the turbidity does not increase accordingly.

[0062] For example, if the electrical conductivity and total dissolved solids at a candidate point of a structure decrease together with their normal levels, while the turbidity does not change significantly, then it is determined to be an infiltration of external water.

[0063] In one embodiment, an unconventional discharge is identified when only the characteristic pollutant increases while other indicators remain unchanged. This is based on the fact that unconventional discharge introduces wastewater from a specific source, characterized by a significant increase in the characteristic pollutants from that source. However, indicators that characterize the overall properties of wastewater, such as conductivity, total dissolved solids, and turbidity, do not necessarily change in the same direction. Therefore, an increase in the characteristic pollutant alone, rather than a change in all indicators simultaneously, is used as the criterion for unconventional discharge.

[0064] For example, if a certain characteristic pollutant at a candidate structural point is significantly higher than its normal level, while conductivity, total dissolved solids, and turbidity do not change significantly, it is identified as an unconventional emission.

[0065] In one embodiment, when only turbidity increases while conductivity and total dissolved solids remain unchanged, it is determined to be pipe sedimentation scouring or cross-contamination. This is based on the fact that when sediments in the pipe are suspended under the influence of water flow, they introduce suspended particulate matter, causing an increase in turbidity. Since suspended particulate matter is insoluble, it does not change the content of dissolved substances in the water; therefore, conductivity and total dissolved solids do not change accordingly. The fact that turbidity increases while solubility remains unchanged distinguishes pipe sedimentation scouring or cross-contamination from external water infiltration or unconventional discharge connections.

[0066] For example, if the turbidity at a candidate structural point is higher than its normal level, while the conductivity and total dissolved solids do not change significantly, it is determined to be pipe deposition erosion or cross-linking.

[0067] Step S44: Based on the water quality anomaly type and the upstream responsibility segment and inflow relationship of the structural candidate points, determine the location of additional risk candidate points; Furthermore, the specific steps in step S44 for determining the location of additional risk candidate points are as follows: When the structural candidate point is a confluence candidate point or a confluence-diversion composite point, the water quality of its upstream inflow pipe is detected, and the upstream inflow pipe that shows the same water quality abnormality as the structural candidate point is designated as the target pipe. In one embodiment, utilizing the unique pipe connection relationships of this type, water quality anomalies detected at the candidate structural point are attributed to specific pipes or facilities, and the location of additional risk candidate points is determined based on the type of water quality anomaly. Water quality anomalies detected at a candidate structural point only indicate an abnormality in the water flow at that point. Since the candidate structural point connects to multiple pipes, the anomaly may be introduced by one of these pipes or originate from the facilities at the candidate structural point. Therefore, further testing of the water quality in the pipes connected to the candidate structural point is conducted, and pipes exhibiting the same water quality anomalies as those at the candidate structural point are identified as the pipes that introduced the anomaly.

[0068] It should be noted that "showing the same water quality anomaly" means that the water quality indicators detected at the pipeline show the same anomalies as those at the candidate point of the structure. For example, when the candidate point of the structure is external water infiltration, the corresponding pipeline will also show low conductivity and total dissolved solids.

[0069] When external water infiltrates, the corresponding location of the responsible section between the target pipeline and its upstream adjacent candidate structure is taken; when unconventional discharges are connected, the connection point of the target pipeline is taken as the additional risk candidate point. In one embodiment, the confluence candidate point is formed by the convergence of upstream inflow pipes, and the confluence-divergence composite point also converges multiple upstream inflow pipes on its upstream side. Since both are points where multiple upstream water flows converge on their upstream sides, they are treated in the same way. For the confluence candidate point or the confluence-divergence composite point, the water quality of each of its upstream inflow pipes is detected. The upstream inflow pipe that exhibits the same water quality anomaly as the candidate point is identified as the target pipe, i.e., the pipe that introduces the anomaly.

[0070] After identifying the target pipeline, the location of additional risk candidate points is determined according to the type of water quality anomaly: when external water infiltrates, the external water infiltrates along the pipe section where the target pipeline is located, and the corresponding position of the responsible section between the target pipeline and its upstream adjacent structural candidate point is taken as the additional risk candidate point; when unconventional discharge is connected, the discharge source is connected through the target pipeline, and the connection point of the target pipeline is taken as the additional risk candidate point.

[0071] For example, if external water infiltration is detected at a certain confluence candidate point, and three upstream confluence pipes are detected, one of which shows low conductivity and total dissolved solids, then this upstream confluence pipe is designated as the target pipe, and the corresponding position of the responsibility section between it and the upstream adjacent structural candidate point is taken as the additional risk candidate point.

[0072] When all upstream inflowing pipelines are normal, but the candidate point of the structure shows an anomaly, the location corresponding to the candidate point of the structure is taken as the additional risk candidate point. In one embodiment, when there are no abnormalities in the upstream inflow pipes of the confluence candidate point or the confluence-diversion composite point, but the structural candidate point itself is abnormal, it indicates that the abnormality is not brought in by a certain upstream inflow pipe, but originates from local factors such as pipe intersection and flow cross-section changes at the structural candidate point, such as the sludge sediment being washed away and suspended. Therefore, the location corresponding to the structural candidate point itself is taken as the additional risk candidate point.

[0073] When a structural candidate point is a diversion candidate point, the water quality of its upstream inlet pipe is tested. If the upstream inlet pipe shows the same water quality anomaly, the corresponding position of the responsible section between it and the adjacent upstream structural candidate point is taken as an additional risk candidate point. If the upstream inlet pipe is normal but the diversion candidate point shows anomaly, the corresponding position of the diversion candidate point is taken as an additional risk candidate point.

[0074] In one embodiment, the diversion candidate point is equipped with multiple outflow pipes, corresponding interception wells, diversion wells, or overflow wells, with the same inflow side. Since the diversion candidate point distributes the same inflow to multiple downstream pipes, the water quality of each downstream diversion pipe comes from the same inflow and is difficult to distinguish. Therefore, the downstream diversion pipes of the diversion candidate point are not inspected, but the upstream inflow pipes are inspected to determine whether the anomaly is brought in by the upstream inflow or originates from the diversion, interception, or overflow facilities at the diversion candidate point.

[0075] Specifically, when the upstream inlet pipe exhibits the same water quality anomaly as the diversion candidate point, the anomaly is determined to be brought in from the upstream, and the corresponding position of the responsible section between the upstream inlet pipe and its adjacent upstream structural candidate point is taken as the additional risk candidate point; when the upstream inlet pipe is not abnormal but the diversion candidate point exhibits anomaly, the anomaly is determined to originate from the diversion, interception, or overflow facilities at the diversion candidate point, such as sediment deposition in front of the interception weir or backflow and mixing of river water at the overflow outlet, and the corresponding position of the diversion candidate point is taken as the additional risk candidate point.

[0076] For example, if a diversion candidate point is found to have high turbidity, while the turbidity of its upstream inlet pipe is normal, then the anomaly is determined to originate from the interception facility at the diversion candidate point, and the corresponding location of the diversion candidate point is taken as an additional risk candidate point.

[0077] It should be noted that the upstream inlet pipe is tested instead of the downstream diversion pipe for diversion candidate points because the diversion candidate point distributes the same inlet water to each downstream pipe, and the water quality of each downstream diversion pipe is the same, so it is impossible to attribute the cause based on whether a certain downstream diversion pipe is abnormal. By testing the upstream inlet pipe, it is possible to distinguish whether the abnormality comes from the upstream inlet water or originates from the facilities at the diversion candidate point, thereby determining the location of additional risk candidate points.

[0078] Step S45: Combine the additional risk candidate points with the pre-risk candidate points as risk candidate points.

[0079] In one embodiment, the determined additional risk candidate points and pre-risk candidate points are used together as risk candidate points for subsequent steps to merge with structural candidate points and to calculate the degree of overlap.

[0080] For example, several pre-risk candidate points that fall into the operational risk area in a certain drainage zone, and several additional risk candidate points discovered by water quality testing, together constitute the risk candidate points of the drainage zone.

[0081] See Figure 3 There are three candidate structural points P1, P2, and P3 arranged sequentially from top to bottom along a main line, with ordinary inspection wells between each candidate point. For candidate structural point P2, tracing back from P2 to the adjacent prior candidate structural point P1 in the opposite direction of water flow, the tracing path covers two pipe segments between P1 and P2, so the upstream control number of P2 is two. For candidate structural point P3, tracing back from P3 to the adjacent prior candidate structural point P2, the tracing path covers three pipe segments between P2 and P3, so the upstream control number of P3 is three. Each included pipe segment is marked with a short horizontal line in the figure. The upstream responsibility segments of P2 and P3 are connected but do not overlap, with adjacent candidate structural points as the boundary. Each upstream responsibility segment is uniquely assigned to one downstream candidate structural point. At structural candidate point P2, there is a fork upstream. Of the two branches, the branch with the higher pipe grade continues to backtrack (marked as higher grade in the figure). The branch with the lower pipe grade is not included in the backtracking.

[0082] Step S5: Merge the overlapping areas of structural candidate points and risk candidate points into monitoring candidate points. Count the number of different types of placement reasons for each monitoring candidate point as the overlap degree. Select monitoring points from high to low overlap degree. For those with the same overlap degree, select the one with the higher structural level and upstream control number in turn. Add points where the route distance between adjacent monitoring points exceeds the upper limit of the corresponding pipe segment.

[0083] In one embodiment, structural candidate points obtained based on pipeline topology and pipeline grade are combined with risk candidate points obtained based on operational risk factors. The number of mutually exclusive reasons for setting up a monitoring point at each location is counted, and monitoring points are selected accordingly. Finally, the coverage spacing of the monitoring points is checked and supplemented. A location may be worth setting up a monitoring point for multiple different reasons. Locations with more mutually exclusive reasons should be prioritized for monitoring point placement. The number of mutually independent reasons for setting up a location is used as the overlap degree of that location, and monitoring points are selected based on the degree of overlap.

[0084] Furthermore, step S5 includes the following steps: Step S51: Merge structural candidate points and risk candidate points whose locations overlap into the same monitoring candidate point; In one embodiment, overlapping structural candidate points and risk candidate points are merged into a single monitoring candidate point. Since structural candidate points are identified based on pipeline topology and pipeline grade, while risk candidate points are identified based on operational risk factors, they may both fall at the same manhole location in the pipeline network. Merging overlapping locations into a single monitoring candidate point allows multiple factors related to the structural and operational risks corresponding to that location to be statistically analyzed together at the same monitoring candidate point.

[0085] For example, if a manhole is marked as both a confluence candidate point and a risk candidate point because it falls into a high-water-level operating area, then they are merged into the same monitoring candidate point, which simultaneously possesses the characteristics of both a confluence candidate point and a high-water-level area.

[0086] Step S52: Calculate the reasons for the placement of each monitoring candidate point, including the reasons for the placement of the monitoring candidate point as a confluence candidate point, as a diversion candidate point, falling into an area of ​​waterlogging, falling into a high water level area, and falling into an area of ​​external water infiltration or low water quality concentration. In one embodiment, for each candidate monitoring point, the rationale for its placement is statistically analyzed. These rationale include whether the candidate monitoring point is a confluence point, a diversion point, located in an area prone to flooding, located in a high-water-level area, or located in an area with external water infiltration or low water quality concentration. Each rationale corresponds to one aspect of why a monitoring point is worth placing at that location. Structural rationale is derived from structural candidate point markers, and operational risk rationale is derived from risk candidate point markers.

[0087] For example, a certain monitoring candidate point is statistically characterized by three aspects: it is a candidate point for confluence, it falls into a high water level area, and it falls into an area where external water infiltration occurs.

[0088] Step S53: Group the reasons for the placement into independent categories based on their causes. Each category is counted as one item. Multiple tags under the same category are not counted repeatedly, thereby calculating the overlap.

[0089] In one embodiment, the reasons for each monitoring candidate point are grouped into independent categories based on their causes. Each category is counted as one item, and multiple markers under the same category are not counted repeatedly. The total number of independent categories after merging is used as the overlap degree of the monitoring candidate point. Although some reasons for point placement may appear as different markers, they are actually caused by the same cause. If they are counted separately, the same cause will be counted repeatedly, thus artificially inflating the overlap degree of that location. After grouping into independent categories based on causes, the overlap degree reflects the number of non-repeating reasons at that location.

[0090] For example, a monitoring candidate point has two labels: falling into an area of ​​external water infiltration and falling into an area of ​​low water quality concentration. If the two are caused by the same external water and belong to the same category, they are counted as one item. The overlap of this monitoring candidate point, together with its item as a confluence candidate point, is counted as two.

[0091] Furthermore, step S5 also includes the following steps: Step S54: Select monitoring points from high to low based on the degree of overlap; when the degree of overlap is the same, first select the one with a higher structural level; when the structural levels are also the same, then select the one with a larger upstream control number. In one embodiment, monitoring points are selected from high to low overlap, prioritizing locations indicated by the most unique reasons. When several candidate monitoring points have the same overlap, the one with the higher structural level is selected first. If the structural levels are also the same, the one with the larger upstream control number is selected. Thus, when the overlap is the same, further distinctions are made based on structural level and upstream control number, prioritizing locations located in key positions of pipeline transmission backbone or flow redistribution, and representing a larger upstream range.

[0092] For example, if two monitoring candidate points have the same degree of overlap, and one has a high structural level and the other has a low structural level, then the one with the high structural level is selected first; if both have a high structural level, then the upstream control numbers of the two are compared, and the one with the larger upstream control number is selected first.

[0093] Step S55: For two adjacent monitoring points, calculate the distance between them along the pipeline route. When the distance exceeds the upper limit of the distance preset by the pipeline grade of the pipeline segment between them, select the monitoring candidate point with the highest overlap between the two adjacent monitoring points and add it as a monitoring point. In one embodiment, for two adjacent monitoring points selected based on overlap, the distance between them along the pipeline route is calculated. When the distance exceeds the upper limit of the distance preset by the pipeline grade of the pipe segment between them, it indicates that there is a pipe segment with insufficient coverage between the two adjacent monitoring points, and a monitoring point needs to be added between them. In this case, the monitoring point with the highest overlap among the unselected monitoring candidate points between the two adjacent monitoring points is selected first to be added as a monitoring point. Prioritizing the selection of the existing unselected monitoring candidate point with the highest overlap ensures that the added monitoring point is also located in a position with multiple placement reasons, thereby supplementing coverage while making the monitoring point as useful as possible.

[0094] For example, if the distance between two adjacent monitoring points along the pipeline route exceeds the corresponding upper limit of the distance, and there are two unselected monitoring candidate points with an overlap of 2 and 1 respectively, then the two with the overlap of 1 will be selected as monitoring points.

[0095] Step S56: When there are no unselected candidate monitoring points between two adjacent monitoring points, add a monitoring point at the midpoint of the pipeline route between them.

[0096] In one embodiment, when there are no unselected candidate monitoring points between two adjacent monitoring points, a monitoring point is added at the midpoint of the pipeline route between them. This situation indicates that there are no existing candidate locations available for activation between the two adjacent monitoring points, and a monitoring point is added at the midpoint of the pipeline route between them to supplement coverage.

[0097] For example, if the distance between two adjacent monitoring points exceeds the corresponding upper limit of the distance and there are no unselected monitoring candidate points in between, then a monitoring point is added at the midpoint of the pipeline route between the two monitoring points.

[0098] It should be noted that the upper limit of the spacing is preset according to the pipeline grade of the pipe section, so that the upper limit of the spacing corresponding to the higher grade section is greater than the upper limit of the spacing corresponding to the lower grade section. That is, in the main pipeline and trunk section mainly for transmission, the spacing between adjacent monitoring points is allowed to be larger, while in the branch pipe and collection section mainly for collection, the spacing between adjacent monitoring points is required to be smaller, so that the layout density of monitoring points varies with the pipeline grade.

[0099] The specific value of the upper limit of the spacing can be determined in combination with the scale of the pipeline network and the monitoring requirements. When there are multiple pipe sections of different pipeline grades between two adjacent monitoring points, the minimum value of the upper limit of the spacing corresponding to each pipe section can be taken as the upper limit of the spacing between the two adjacent monitoring points to avoid insufficient coverage.

[0100] Of particular importance is that step S53 specifically includes: The reasons for site selection are grouped into independent categories based on their causes, with each category counted as one item. Multiple tags under the same category are not counted repeatedly. Among them, the confluence and diversion are caused by the same water flow. For inspection wells that are both confluence and diversion candidate points, the reasons for confluence and diversion are classified into the same structural category and counted as one item. If the infiltration of external water and the low water quality concentration are caused by the same external water source, locations that have both external water infiltration and low water quality concentration are classified as the same external water category and counted as one item. The total number of mutually independent categories after merging is used as the overlap of the monitoring candidate point.

[0101] In one embodiment, when calculating the overlap of monitoring candidate points, the various reasons for the placement of the monitoring candidate points are first grouped into mutually independent categories according to their causes. Each category is counted as one item, and multiple tags under the same category are not counted repeatedly. Then, the total number of mutually independent categories after merging is used as the overlap.

[0102] Among them, the reasons for a confluence and diversion point being considered a confluence candidate and a diversion candidate, both caused by the convergence of water flows at the same location, are classified into the same structural category and counted as one item; the reasons for falling into an external water infiltration area and a low water quality concentration area, both caused by the same external water infiltration cause (infiltration increases the water volume in the pipe section while diluting the sewage with clean water, thus reducing its concentration), are classified into the same external water category and counted as one item; reasons for location caused by different causes, such as waterlogging, high water level, and being a structural candidate point, are counted into their respective categories. This treatment is to avoid counting multiple markers caused by the same cause separately, which would artificially inflate the overlap, and to ensure that the overlap reflects the number of non-overlapping causes at that location.

[0103] For example, if a monitoring candidate point is a confluence and diversion point, falls within an area of ​​external water infiltration, and falls within an area of ​​low water quality concentration, then its confluence and diversion are counted as one item, and its external water infiltration and low water quality concentration are counted as another item, with an overlap of two. On the other hand, if a monitoring candidate point is a confluence candidate point, falls within an area of ​​waterlogging, and falls within an area of ​​high water level, the causes of these three factors are different, with an overlap of three.

[0104] Of particular importance is that step S55 involves adding monitoring points between two adjacent monitoring points, specifically including: Step S551: Determine the unselected monitoring candidate points between two adjacent monitoring points, and the distance between each monitoring candidate point along the pipeline route to the selected monitoring points at both ends; Step S552: Among the unselected monitoring candidate points, select the one with the highest overlap to add as a monitoring point; when the overlap is the same, select the one that makes the spacing between the two sides more balanced after the addition. Step S553: ​​After the supplement is added, the distance between the supplemented point and the adjacent monitoring point is recalculated. If there are still sections where the distance exceeds the upper limit of the corresponding distance, steps S551 to S552 are repeated for the section until the distance between each section does not exceed the upper limit of the corresponding distance.

[0105] In one embodiment, when adding a monitoring point between two adjacent monitoring points, the location of the addition is determined as follows: First, all unselected candidate monitoring points between the two adjacent monitoring points are identified, and the distance between each unselected candidate monitoring point and the selected monitoring points at both ends along the pipeline route is calculated. Then, the monitoring point with the highest overlap among these unselected candidate monitoring points is added as a monitoring point. When there are multiple unselected candidate monitoring points with the same overlap, the one that makes the distance between the two sides more balanced after addition is selected, so that the added monitoring points have more reasons for placement and are distributed as evenly as possible. After addition, the distance between the added point and its adjacent monitoring points is recalculated. If there are still sections where the distance exceeds the corresponding upper limit, the addition of monitoring points in the above manner continues until the distance between all adjacent monitoring points does not exceed the corresponding upper limit.

[0106] For example, if the distance between two adjacent monitoring points along the pipeline route exceeds the corresponding distance limit, and there are three unselected monitoring candidate points with overlap of 2, 1, and 1 respectively, first add the candidate point with overlap of 2. If the positions of the two candidate points with overlap of 1 make the distance on both sides similar after addition, then add the one closer to the middle of the distance on the side that still exceeds the limit. After addition, recalculate the distance of each segment until each segment does not exceed the corresponding distance limit.

[0107] It should be noted that this step prioritizes adding unselected monitoring candidate points with high overlap. Only when the overlap is the same will the balance of the distance between the two sides be used as a further selection criterion. Therefore, the addition of points prioritizes multiple uses of a single point while also ensuring uniform coverage. When the section is long and the distance requirement is still not met after adding a monitoring point, the distance requirement is gradually met by repeatedly adding points, thereby ensuring that there are no coverage blind spots between adjacent monitoring points that exceed the distance limit.

[0108] See Figure 2 For a drainage zone, the water flows from top to bottom and eventually converges at the bottom outlet and pumping station or sewage treatment plant. In this drainage zone, the two collection pipes on the upper left merge into a manhole, and their downstream pipes are upgraded to branch pipes. This manhole is marked as a confluence candidate point because the downstream pipe is of a higher grade than the upstream pipe, and is labeled as "upgraded" in the figure. The two branch pipes on the upper right merge into another manhole, and their downstream pipes remain branch pipes and are not upgraded. This manhole is not marked as a confluence candidate point, and is labeled as "not upgraded" in the figure. The two serve as a contrast.

[0109] Downstream along the water flow direction, a manhole connects to multiple pipes, causing the downstream section to rise to become a main pipe. Simultaneously, two downstream pipes branch off—one for transfer and one for overflow—marking this as a confluence and branching point. Because it falls within a high-water-level operating area, it was a potential risk point and was ultimately selected as a monitoring point. Downstream, another manhole branches off into a main pipe and a diversion pipe, also marked as a branching point. Further downstream, a branch pipe joins from the right, causing this point to rise to become a main pipe and a confluence point. This point falls within an area of ​​external water infiltration and low water quality concentration, and was selected as a monitoring point. Between two adjacent monitoring points before the outlet, because the distance along the pipeline route exceeds the corresponding upper limit, and there are no unselected monitoring candidates in between, a new monitoring point is added between these two adjacent points, marked as a supplementary point in the figure. An upstream responsibility section is marked with a dashed box on the left side of the figure.

[0110] Therefore, the embodiments should be considered as exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of the equivalents of the application are intended to be included within the invention.

[0111] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features of the invention herein.

Claims

1. A method for determining the location of monitoring points in an urban drainage system, characterized in that, Includes the following steps: Step S1: Organize the connection topology of the drainage pipe network to obtain the directed pipe network connected by pipes and inspection wells, and classify each pipe into pipe class based on pipe diameter; Step S2: Along the water flow direction, mark the manholes with downstream pipe grades higher than the highest grades of each upstream pipe as confluence candidate points, and mark the manholes with more than one outflow pipe as diversion candidate points. The confluence candidate points and diversion candidate points constitute structural candidate points. Step S3: For each structural candidate point, backtrack along the reverse direction of water flow to the adjacent prior structural candidate point, pipeline source, or zone boundary. The number of pipe segments covered by the backtracking path is used as the upstream control number of the structural candidate point, and a structural level is assigned. Step S4: Overlay the pre-acquired operational risk areas onto the directed pipeline network to obtain pre-risk candidate points, and detect the water quality and upstream responsibility section and confluence relationship of each structural candidate point to determine additional risk candidate points. Use the pre-risk candidate points and additional risk candidate points together as risk candidate points. Step S5: Merge the overlapping areas of structural candidate points and risk candidate points into monitoring candidate points. Count the number of different types of placement reasons for each monitoring candidate point as the overlap degree. Select monitoring points from high to low overlap degree. For those with the same overlap degree, select the one with the higher structural level and upstream control number in turn. Add points where the route distance between adjacent monitoring points exceeds the upper limit of the corresponding pipe segment.

2. The method for determining the location of monitoring points in an urban drainage system according to claim 1, characterized in that, Step S1, which classifies pipes based on pipe diameter, includes: Obtain the nominal inner diameter of each pipe and divide the pipes into main pipes, branch pipes, and collection pipes according to the preset pipe diameter range; The diameter of the main pipe is greater than the first threshold, the diameter of the branch pipe is between the second threshold and the first threshold, the diameter of the branch pipe is between the third threshold and the second threshold, and the diameter of the collection pipe is less than the third threshold; wherein the first threshold is greater than the second threshold, and the second threshold is greater than the third threshold. The main pipe and trunk pipe are classified as high-level sections, while the branch pipes and collection pipes are classified as low-level sections.

3. The method for determining the location of monitoring points in an urban drainage system according to claim 2, characterized in that, Step S2 includes the following steps: Step S21: Using each inspection well as a node, determine all upstream pipes flowing into the node and all downstream pipes flowing out of the node; Step S22: Select the pipe with the highest grade among all upstream pipes as the upstream benchmark grade for the inspection well; Step S23: Compare the pipe grade of each downstream pipe flowing out of the manhole with the upstream benchmark grade. When there is a downstream pipe with a higher pipe grade than the upstream benchmark grade, mark the manhole as a candidate confluence point. Step S24: When the pipeline grade of all downstream pipelines is not higher than the upstream benchmark grade, they are not marked as confluence candidate points.

4. The method for determining the location of monitoring points in an urban drainage system according to claim 3, characterized in that, Step S2 also includes the following steps: Step S25: Count the number of downstream pipes flowing out of the inspection well. When the number is more than one, mark the inspection well as a diversion candidate point. The diversion candidate point corresponds to the flow redistribution location of the interception well, diversion well or overflow well. Step S26: When a manhole is simultaneously marked as a confluence candidate point and a diversion candidate point, it is marked as a confluence-diversion composite point; Step S27: Combine the confluence candidate points, the branching candidate points, and the confluence-branching composite points to form the structural candidate points.

5. The method for determining the location of monitoring points in an urban drainage system according to claim 4, characterized in that, Step S3 includes: For each candidate structural point, backtrack along the reverse direction of water flow until one of the following is encountered: an adjacent prior candidate structural point, a pipeline source, or a zone boundary. The first one encountered is taken as the upper limit of the upstream responsibility section of the candidate structural point, forming a backtracking path. The pipeline source is the initial inspection well with no upstream pipeline inflow, and the zone boundary is the outer edge of the drainage zone's catchment area. The pipeline network is divided into upstream responsibility segments, each uniquely belonging to a single candidate structural point, by using the candidate structural point as the boundary between adjacent candidate structural points. The backtracking paths of adjacent candidate structural points do not overlap. The number of pipe segments covered by the backtracking path to which the candidate structure point belongs is used as the upstream control number of the candidate structure point.

6. The method for determining the location of monitoring points in an urban drainage system according to claim 5, characterized in that, Step S3 also includes: When the backtracking path passes through a diversion candidate point or a confluence-diversion composite point and bifurcation occurs, backtracking is continued only along the branch with the higher pipeline grade, so that the upstream responsibility segment at the bifurcation point is uniquely assigned to the structural candidate point downstream along the main transfer path, thus avoiding the same upstream pipe segment being repeatedly counted in the upstream control number of different structural candidate points. When the downstream pipeline of a confluence candidate point belongs to a high-level section, it is assigned a high-level grade; otherwise, it is assigned a low-level grade. For diversion candidate points, a high-level grade is assigned. The higher of the levels obtained by taking the confluence and branching points as confluence candidate points and the levels obtained as branching candidate points is taken as the structural level.

7. The method for determining the location of monitoring points in an urban drainage system according to claim 6, characterized in that, Step S4 includes the following steps: Step S41: Overlay the pre-acquired operational risk areas of waterlogging, high water level, external water infiltration, and low water quality concentration onto the directed pipe network, and mark the inspection wells that fall into the operational risk areas as pre-risk candidate points. Step S42: Install water quality testing devices at the inspection wells corresponding to each candidate structural point to test the conductivity, total dissolved solids, characteristic pollutants, and turbidity of the wastewater at the candidate structural point. The conductivity and total dissolved solids represent the mixing of clean water from outside the water source, the characteristic pollutants represent the access of a specific discharge source, and the turbidity represents the scouring and suspension of sediments in the pipeline. Step S43: When conductivity and total dissolved solids decrease together while turbidity remains unchanged, it is determined to be external water infiltration; when only characteristic pollutants increase, it is determined to be unconventional discharge access; when only turbidity increases while conductivity and total dissolved solids remain unchanged, it is determined to be pipeline sedimentation and scouring or cross-connection; thus determining the type of water quality anomaly. Step S44: Based on the water quality anomaly type and the upstream responsibility segment and inflow relationship of the structural candidate points, determine the location of additional risk candidate points; Step S45: Combine the additional risk candidate points with the pre-risk candidate points as risk candidate points.

8. The method for determining the location of monitoring points in an urban drainage system according to claim 7, characterized in that, The specific steps for determining the location of additional risk candidate points in step S44 are as follows: When the structural candidate point is a confluence candidate point or a confluence-diversion composite point, the water quality of its upstream inflow pipe is detected, and the upstream inflow pipe that shows the same water quality abnormality as the structural candidate point is designated as the target pipe. When external water infiltrates, the corresponding location of the responsible section between the target pipeline and its upstream adjacent candidate structure is taken; when unconventional discharges are connected, the connection point of the target pipeline is taken as the additional risk candidate point. When all upstream inflowing pipelines are normal, but the candidate point of the structure shows an anomaly, the location corresponding to the candidate point of the structure is taken as the additional risk candidate point. When a structural candidate point is a diversion candidate point, the water quality of its upstream inlet pipe is detected. If the upstream inlet pipe shows the same water quality anomaly, the corresponding position of the responsibility section between it and the upstream adjacent structural candidate point is taken as an additional risk candidate point. When there is no abnormality in the upstream water inlet pipeline but the diversion candidate point shows an abnormality, the location corresponding to the diversion candidate point is taken as the additional risk candidate point.

9. The method for determining the location of monitoring points in an urban drainage system according to claim 8, characterized in that, Step S5 includes the following steps: Step S51: Merge structural candidate points and risk candidate points whose locations overlap into the same monitoring candidate point; Step S52: Calculate the reasons for the placement of each monitoring candidate point, including the reasons for the placement of the monitoring candidate point as a confluence candidate point, as a diversion candidate point, falling into an area of ​​waterlogging, falling into a high water level area, and falling into an area of ​​external water infiltration or low water quality concentration. Step S53: Group the reasons for the placement into independent categories based on their causes. Each category is counted as one item. Multiple tags under the same category are not counted repeatedly, thereby calculating the overlap.

10. The method for determining the location of monitoring points in an urban drainage system according to claim 8, characterized in that, Step S5 also includes the following steps: Step S54: Select monitoring points from high to low based on the degree of overlap; when the degree of overlap is the same, first select the one with a higher structural level; when the structural levels are also the same, then select the one with a larger upstream control number. Step S55: For two adjacent monitoring points, calculate the distance between them along the pipeline route. When the distance exceeds the upper limit of the distance preset by the pipeline grade of the pipeline segment between them, select the monitoring candidate point with the highest overlap between the two adjacent monitoring points and add it as a monitoring point. Step S56: When there are no unselected candidate monitoring points between two adjacent monitoring points, add a monitoring point at the midpoint of the pipeline route between them.

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