A method and system for preventing and controlling non-point source pollution in a river basin

Abstract

This invention relates to the field of watershed pollution control technology, and more particularly to a method and system for controlling non-point source pollution in watersheds. The method includes the following steps: deploying monitoring units along the watershed slope to the confluence channel to acquire surface runoff formation locations and soil moisture parameters under rainfall conditions; determining runoff initiation thresholds based on soil moisture parameters and identifying runoff generation response units; collecting data on the dispersion and convergence process of runoff in the slope within the generation response units, and acquiring runoff retention depth parameters and overflow turning points in surface depressions; determining the triggering conditions for pollutant transformation from an attached state to a migrating state based on the retention depth parameters and overflow turning points, and identifying pollutant release nodes. This invention, through watershed pollution control, gradually slows down and impounds pollutants along their transport path before entering the confluence channel, thereby improving the targeting and stability of non-point source pollution interception during migration.

Description

Technical Field

[0001] This invention relates to the field of watershed pollution control technology, and in particular to a method and system for controlling non-point source pollution in watersheds. Background Technology

[0002] Non-point source pollution in watersheds primarily originates from the scouring and migration of soil and attached pollutants by surface runoff under rainfall conditions. It is characterized by strong dispersion, concealed formation processes, and significant spatial variations. Unlike the concentrated emissions of point source pollution, non-point source pollution exhibits dynamic evolution during slope runoff generation, runoff convergence, and inflow. Its generation is closely related to soil moisture content, surface micro-topography, and runoff pathways. When rainfall occurs, soil moisture gradually approaches saturation, preferentially forming runoff in local areas. This runoff is then retained and redistributed in slope depressions, triggering the transformation of pollutants from attached to migrating states. During runoff transport to confluence channels, particulate matter undergoes alternating processes of initiation and redeposition under different hydrodynamic conditions, resulting in unstable and phased pollutant transport pathways. Existing technologies largely focus on end-of-pipe interception or overall reduction, lacking coordinated identification and segmented control of runoff formation, pollutant release, and transport processes. This makes it difficult to implement refined interventions at key control nodes in different locations within the watershed, thus affecting the targetedness and stability of non-point source pollution control. Summary of the Invention

[0003] Therefore, it is necessary to provide a method and system for preventing and controlling non-point source pollution in watersheds to solve at least one of the above-mentioned technical problems.

[0004] To achieve the above objectives, a method for controlling non-point source pollution in watersheds includes the following steps:

[0005] Step S1: Deploy monitoring units along the watershed slope to the confluence channel to obtain the location of surface runoff formation and soil moisture state parameters under rainfall conditions. Determine the runoff initiation threshold based on the soil moisture state parameters and identify the runoff generation response units.

[0006] Step S2: Collect the runoff dispersion and collection process on the slope in the runoff generation response unit, and obtain the retention depth parameters and overflow turning points of the runoff in the surface depression; based on the retention depth parameters and overflow turning points, determine the triggering conditions for the transformation of pollutants from the attached state to the migrating state, and determine the pollutant release nodes.

[0007] Step S3: Along the runoff path from the pollutant release node to the confluence channel, obtain the starting particle size and critical redeposition particle size of particulate matter during the runoff scouring process, divide the continuous migration section and intermittent deposition section according to the starting particle size and critical redeposition particle size, and determine the transport channel corresponding to the pollutant.

[0008] Step S4: Deploy barrier control units on the transport channel. Adjust the interception position and flux of the barrier control units according to the retention depth parameter and the critical particle size for redeposition, so that pollutants are staged and retained before entering the confluence channel.

[0009] The present invention also provides a watershed non-point source pollution control system for performing the watershed non-point source pollution control method described above, the watershed non-point source pollution control system comprising:

[0010] The runoff generation response unit identification module is used to deploy monitoring units along the watershed slope to the confluence channel, obtain the location of surface runoff formation and soil moisture state parameters under rainfall conditions, determine the runoff initiation threshold based on the soil moisture state parameters, and identify the runoff generation response units.

[0011] The pollutant release node determination module is used to collect the dispersion and collection process of runoff on the slope in the runoff generation response unit, and to obtain the retention depth parameters and overflow turning points of runoff in the surface depressions; based on the retention depth parameters and overflow turning points, the triggering conditions for the transformation of pollutants from the attached state to the migrating state are determined, and the pollutant release nodes are determined.

[0012] The transport channel determination module is used to obtain the initiation particle size and critical redeposition particle size of particulate matter during the runoff scouring process along the runoff path from the pollutant release node to the confluence channel, divide the continuous migration section and intermittent deposition section according to the initiation particle size and critical redeposition particle size, and determine the transport channel corresponding to the pollutant.

[0013] The barrier control module is used to deploy barrier control units on the transport channel. The interception position and flux of the barrier control units are adjusted according to the retention depth parameter and the critical particle size for redeposition, so that pollutants are staged and retained before entering the confluence channel.

[0014] The beneficial effects of this invention are as follows: By constructing monitoring units along the watershed slope to the confluence channel and introducing the correspondence between soil moisture state parameters and runoff initiation thresholds, dynamic constraint identification of runoff generation locations is achieved, transforming the runoff response units from discrete judgments to spatially continuous deterministic results. Based on this, by combining the retention depth parameters of surface depressions and the overflow turning point, the process of runoff transformation from local retention to outward discharge is characterized, providing clear triggering conditions for the transformation of pollutants from attached to migrating states and forming pollutant release nodes corresponding to the terrain structure. Furthermore, by comparing the initiation particle size with the critical redeposition particle size, the alternating processes of particle initiation and deposition in the runoff path are constrained and divided, giving distinguishable boundary characteristics between continuous migration sections and intermittent deposition sections, thereby constructing pollutant transport channels consistent with runoff dynamic changes. Based on the retention depth parameters and the critical redeposition particle size, the location and flux of the control units are matched and adjusted, causing pollutants to gradually slow down and be retained at different stages along the transport path before entering the confluence channel, thereby improving the targeting and stability of non-point source pollution interception during migration. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the steps involved in a method for controlling non-point source pollution in a watershed.

[0016] Figure 2 This is a schematic diagram of the process applied to the watershed non-point source pollution control system;

[0017] Figure 3 A schematic diagram of the runoff generation response unit in the watershed;

[0018] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0019] 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.

[0020] 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.

[0021] 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.

[0022] To achieve the above objectives, please refer to Figures 1 to 3 A method for preventing and controlling non-point source pollution in watersheds includes the following steps:

[0023] All specific values ​​involved in this embodiment are exemplary parameters used to clearly illustrate the technical operation process and are not the only limitation of the present invention.

[0024] Step S1: Deploy monitoring units along the watershed slope to the confluence channel to obtain the location of surface runoff formation and soil moisture state parameters under rainfall conditions. Determine the runoff initiation threshold based on the soil moisture state parameters and identify the runoff generation response units.

[0025] Step S2: Collect the runoff dispersion and collection process on the slope in the runoff generation response unit, and obtain the retention depth parameters and overflow turning points of the runoff in the surface depression; based on the retention depth parameters and overflow turning points, determine the triggering conditions for the transformation of pollutants from the attached state to the migrating state, and determine the pollutant release nodes.

[0026] Step S3: Along the runoff path from the pollutant release node to the confluence channel, obtain the starting particle size and critical redeposition particle size of particulate matter during the runoff scouring process, divide the continuous migration section and intermittent deposition section according to the starting particle size and critical redeposition particle size, and determine the transport channel corresponding to the pollutant.

[0027] Step S4: Deploy barrier control units on the transport channel. Adjust the interception position and flux of the barrier control units according to the retention depth parameter and the critical particle size for redeposition, so that pollutants are staged and retained before entering the confluence channel.

[0028] In one embodiment, monitoring units are deployed within the range from the watershed slope to the confluence channel. Hydrological sensors are used to acquire the location of surface runoff formation and soil moisture state parameters under rainfall conditions. The runoff initiation threshold is determined based on the gradient of soil moisture state parameter changes in each monitoring unit. Spatial continuity analysis is performed on the runoff initiation thresholds of different monitoring units, and areas that meet the criteria of progressively decreasing thresholds and have a slope connectivity trend are selected as runoff generation response units.

[0029] Within the runoff response unit, the dispersion and convergence process of runoff in the slope micro-topography is collected. Surface depressions are identified as retention units, and the retention depth parameters and water level changes of each retention unit are obtained. When the water level reaches the overflow boundary of the corresponding retention unit, the overflow turning point is determined, and the runoff discharge path is constructed based on the spatial connectivity between the overflow turning points. Based on the matching relationship between the retention depth parameters and the overflow turning points, the triggering conditions for the transformation of pollutants from the attached state to the migrating state are determined, and the locations that meet the triggering conditions are identified as pollutant release nodes.

[0030] The initiation particle size and critical redeposition particle size of particulate matter are obtained along the runoff path from the pollutant release node to the confluence channel, and spatial correspondence analysis is performed on the particle size changes along the same path. Based on the comparison relationship between the initiation particle size and the critical redeposition particle size, the segments in the runoff path where particulate matter alternates between continuous initiation and repeated deposition are identified, and these segments are determined as intermittent deposition segments. Furthermore, based on the spatial distribution of intermittent deposition segments, continuous migration segments are divided, and pollutant transport channels are determined by the spatial connectivity of the continuous migration segments.

[0031] By deploying control units along the transport channel and adjusting the interception position and flux of the control units according to the retention depth parameters and critical redeposition particle size at each location, the interception capacity of the control units is adapted to the runoff transport capacity, thereby forming a graded retention structure before pollutants enter the confluence channel.

[0032] In another embodiment, assuming that 200 monitoring units are deployed in a certain watershed, when the rainfall intensity is 25 mm / h, the soil moisture state parameter increases from 0.35 to 0.82; the starting threshold ranges from 0.55 to 0.78, the length of the area that meets the condition of continuous slope reduction is about 120 m, forming 3 runoff response units, of which the main runoff response unit covers an area of ​​about 0.32 km².

[0033] Assuming that approximately 45 retention units are identified within the runoff response unit, with retention depth parameters ranging from 0.03m to 0.18m; after 40 minutes of continuous rainfall, 18 retention units experience overflow transitions, with typical overflow transition water levels concentrated around 0.12m; 6 pollutant release nodes are formed, mainly distributed in the confluence transition zone in the middle and lower part of the slope.

[0034] Assuming a runoff path length of 320m, with an initiation grain size range of 0.05mm–1.2mm and a critical redeposition grain size range of 0.03mm–0.9mm, approximately 5 intermittent depositional sections were identified through comparison, with a cumulative length of approximately 140m; a continuous migration section of approximately 180m was identified, forming 2 main transport channels, with the main channels contributing approximately 72% of the runoff.

[0035] Assuming a total of 12 sets of interception control units are deployed on the transport channel, with the upstream interception flux set at 0.6, the midstream at 0.4, and the downstream at 0.25; after adjustment, the particulate matter retention rate of pollutants before entering the confluence channel increases from the initial 38% to about 81%, with the highest retention efficiency for particles larger than 0.3 mm, reaching over 90%.

[0036] It should be added that you are welcome to participate. Figure 3 The image shows water flowing from the upper slope into retention units formed by surface depressions. Red circles mark the runoff overflow turning points and retention depths. After localized stagnation at the depressions, the water flows outwards along the overflow turning points, connecting with adjacent retention units. This demonstrates the retention and guidance effect of surface depressions on runoff, a key aspect requiring focused control in non-point source pollution prevention and control, providing a basis for deploying control units and achieving tiered retention.

[0037] Of particular importance, step S1 includes:

[0038] Monitoring units are deployed along the watershed slope to the confluence channel to track changes in soil moisture state parameters during rainfall, extract the stage of transition from infiltration accumulation to critical saturation, and determine the spatial distribution of runoff initiation threshold accordingly.

[0039] By continuously comparing the runoff initiation thresholds of adjacent monitoring units, areas where the thresholds decrease progressively and extend along the slope are identified as the preferential runoff formation ranges.

[0040] Within the scope, monitoring units that reach the runoff initiation threshold and experience leakage are selected, and continuous runoff-producing sections are formed based on their connectivity, which are then identified as runoff-producing response units.

[0041] In one embodiment, monitoring units are deployed in a 50m×50m grid within the area from the watershed slope to the confluence channel. Soil moisture sensors continuously collect water content parameters and divide the water content changes during the rainfall process into stages. When the water content changes from the slow infiltration stage to the rapid accumulation stage, it is used as the judgment interval for the transition to critical saturation, and the water content level corresponding to this interval is used as the basis for determining the runoff initiation threshold.

[0042] Spatial sorting and neighborhood difference calculations were performed on the runoff initiation thresholds of each monitoring unit. When the threshold difference between adjacent units was less than a set threshold and showed a gradual decreasing trend from upstream to downstream, the area was determined to have continuous conditions for preferential runoff formation. Based on this, monitoring units that actually reached the runoff initiation threshold and showed surface leakage response were selected and connected and merged according to their adjacency relationship in the slope direction to form a spatially continuous runoff generation zone structure. This runoff generation zone was identified as the runoff generation response unit.

[0043] In another embodiment, it is assumed that 180 monitoring units are deployed in a small to medium watershed with a grid spacing of 40m and a rainfall intensity of approximately 30mm / h. After 25 minutes of continuous rainfall, the soil moisture state parameter gradually increases from an initial 0.32 to 0.79, with the range of 0.62–0.74 corresponding to the critical saturation transition stage, and the spatial distribution range of the runoff initiation threshold is formed accordingly.

[0044] After continuous comparison of adjacent monitoring units, it was found that within a range of approximately 130m in the upper part of the slope, the runoff initiation threshold showed a continuous distribution characteristic, decreasing from 0.71 to 0.58. The area meeting the connectivity condition accounted for approximately 42% of the total slope area. Within this area, 47 monitoring units that reached the runoff initiation threshold and exhibited a leakage response were identified. After connecting and aggregating these units through adjacency relationships, two main runoff zones were formed. The main runoff zones were approximately 210m long, accounting for 68% of the total runoff response area, and were thus identified as runoff response units.

[0045] Preferably, step S2 includes:

[0046] The spatial distribution of surface depressions within the runoff response unit is identified as retention units, and the retention depth parameters of each retention unit are measured.

[0047] Under continuous rainfall, monitor the water level changes of each retention unit, determine the overflow turning point when the water level reaches the overflow boundary, and establish the connection relationship between adjacent retention units;

[0048] Based on the retention depth parameter and the overflow turning point, the conditions for the runoff to change from local retention to continuous outflow are determined, the triggering conditions for attached pollutants to be stripped into the water body are identified, and the location that meets the triggering conditions is determined as the pollutant release node.

[0049] In one embodiment, a digital elevation model is used to extract the surface micro-topography within the runoff response unit, identifying depressions with local minimum potential energy characteristics and defining them as retention units. For each retention unit, the elevation difference between its internal lowest point and the boundary lowest outflow point is extracted as a retention depth parameter to characterize its water storage capacity. During continuous rainfall, water level changes within each retention unit are collected in real time by a water level monitoring unit. When the water level gradually approaches the boundary lowest outflow point, the boundary point corresponding to that location is determined as the overflow turning point, and the runoff outflow direction is determined based on the local slope aspect at that point.

[0050] Based on the spatial adjacency between overflow turning points, a unidirectional connection is established between retention units. When an upstream retention unit overflows and its runoff discharge direction points towards a downstream retention unit, a continuous discharge path is formed. Retention units with low retention depth parameters and frequent overflow turning points are designated as priority stripping areas. At the critical state of their transition from local retention to continuous discharge, the triggering conditions for the transformation of pollutants from an attached state to a migrating state are determined, and the corresponding overflow turning points are identified as pollutant release nodes.

[0051] In another embodiment, it is assumed that approximately 52 retention units were identified within a certain slope runoff response unit, with retention depth parameters ranging from 0.02m to 0.21m. After 35 minutes of continuous rainfall, 21 retention units reached the overflow boundary state, with the overflow turning points mainly concentrated in the depression zone in the middle of the slope. Among the retention units with retention depth parameters below 0.08m, approximately 80% experienced continuous leakage in the later stages of rainfall, gradually forming three distinct interconnected leakage paths. During the continuous runoff leakage process, the time interval between upstream and downstream retention units gradually shortened. When the overflow interval between two consecutive levels of retention units was less than a set threshold (e.g., 3 minutes), the area was determined to have entered a continuous leakage state. Ultimately, six pollutant release nodes were identified, four of which were located on the main interconnected leakage paths and two at the confluence of branch runoffs, corresponding to areas exhibiting strong pollutant stripping and migration activity.

[0052] Preferably, the spatial distribution of surface depressions is identified within the runoff response unit, and this is included as a retention unit:

[0053] Within the runoff response unit, local elevation undulations on the slope are obtained to identify low-lying areas where runoff converges and linear depressions extending along the slope direction.

[0054] Based on the degree of boundary closure of the low-potential region and the degree of convergence of the linear depression, the flow generation response unit is spatially divided to form stagnation blocks;

[0055] The elevation difference between the lowest internal point and the lowest outflow point of each retention block is extracted to determine the storage conditions of the retention block under the action of runoff, and retention units that can form stable existence are selected from the retention blocks.

[0056] In one embodiment, local elevation undulations on the slope are extracted within the runoff response unit based on a digital elevation model. Local gradient analysis identifies low-lying areas formed by runoff convergence and linear depressions extending continuously along the slope direction. These two types of terrain units serve as the basis for potential retention spaces. The continuity of the boundary elevation of the low-lying areas is detected based on the degree of boundary closure. When there is a continuous closure of the boundary elevation without obvious leakage gaps, it is determined to have independent accumulation capacity. Simultaneously, the convergence of the linear depressions is analyzed. When the slopes on both sides continuously converge towards the centerline, it is determined to have runoff guiding capacity.

[0057] Based on the above two characteristics, the runoff response unit is spatially segmented, dividing the combined structure of low-potential areas and linear depressions into multiple retention blocks, ensuring that each retention block has independent runoff collection and discharge boundaries. The elevation difference between the lowest internal point and the lowest external discharge point of each retention block is extracted, and this elevation difference is used as a criterion for water storage capacity. When the rising water level can cover this elevation difference, the retention block is determined to be in a full-storage state. Based on this, retention blocks that can stably form a storage and discharge cycle under rainfall conditions are selected as stable retention units.

[0058] In another embodiment, assuming that within a certain runoff response unit, approximately 38 low-potential zones and approximately 22 linear depressions were identified through DEM analysis, with the low-potential zone boundary closure rate ranging from 0.65 to 0.92 and the linear depression convergence angle concentrated in the range of 8° to 18°. After spatial segmentation, a total of 41 retention blocks were formed, of which approximately 70% of the retention blocks simultaneously contained a composite structure of low-potential zones and linear depressions, possessing strong runoff collection capacity. The elevation difference parameters between the lowest point within each retention block and the lowest outward leakage point at the boundary were statistically analyzed, with the elevation difference ranging from 0.03m to 0.19m. Retention blocks with an elevation difference less than 0.08m experienced full storage response 20 minutes after rainfall. Finally, 16 stable retention units were selected. These units exhibited stable cycle characteristics of collection-storage-overflow under continuous rainfall conditions and were mainly distributed in the continuous depression zone area in the middle and lower part of the slope.

[0059] Preferably, based on the degree of boundary closure of the low-potential region and the convergence of the linear depression, it is spatially divided to form a stagnant block with independent accumulation constraints, including:

[0060] Extract the boundary elevation continuity within the low-potential area, determine whether there is a boundary leakage gap in the low-potential area based on the boundary elevation continuity, and mark the corresponding leakage location;

[0061] Analyze the convergence of the elevations on both sides towards the centerline along the direction of the linear depression to identify whether a continuous guide section is formed and determine the extension path of the guide section.

[0062] When there is no boundary leakage gap in the low-potential area and the linear depression does not form a continuous flow section, the entire area is divided by the boundary enclosure range to form a single retention block.

[0063] When a low-potential area has a boundary leakage gap and a linear depression forms a continuous diversion section, the low-potential area is divided along the diversion path with the continuous diversion section as the boundary, forming a retention block connected sequentially along the runoff direction.

[0064] When the boundary leakage gap and the linear concave diversion section coexist but do not form a corresponding relationship, the boundary is divided by the intersection of the leakage location and the diversion section as a common constraint, so that the dividing boundary passes through both the leakage control point and the runoff collection location.

[0065] In one embodiment, boundary elevation continuity features are extracted within the low-potential zone. Elevation consistency analysis is performed on the boundary closure path to identify any local interruptions in the boundary. Points where elevation continuity decreases are marked as potential leakage gaps to characterize the actual overflow capacity of the low-potential zone. The elevation change trend on both sides of the slope is extracted along the linear depression direction. When the elevations on both sides continuously converge towards the centerline and exhibit directional consistency, the linear depression is determined to form a continuous diversion section, and its spatial extension path is extracted to characterize the preferential transport channel for runoff. The segmentation strategy is selected based on the combination relationship between the leakage gap in the low-potential area and the linear concave diversion section: when the boundary of the low-potential area is continuously closed and no continuous diversion section is formed, the boundary range is used as the overall constraint to form a single retention block; when there is a leakage gap in the low-potential area and the linear concavity forms a continuous diversion section, the diversion section is used as the dominant boundary to sequentially segment the low-potential area along the runoff direction, so that the retention blocks are distributed in series; when the leakage gap and the diversion section exist simultaneously but their spatial positions do not correspond, the intersection of the leakage gap position and the diversion section position is used as a common constraint to dual-locate the segmentation boundary, so that it passes through both the leakage control point and the runoff collection point, thereby forming a retention block structure with consistent constraints.

[0066] In another embodiment, assuming 28 low-potential zones are identified within a certain runoff response unit, with boundary elevation continuity indices ranging from 0.62 to 0.94, analysis reveals approximately 9 low-potential zones with outflow gaps, mainly concentrated in the weak boundary zone of the lower and middle slope. Approximately 17 linear depression structures are identified, of which 11 form continuous guide sections, with lengths ranging from approximately 15m to 85m, and most extending continuously along the main slope direction.

[0067] After segmentation based on the combination of outflow gaps and diversion sections, three types of structures were formed: approximately 12 low-lying areas, due to their complete closed boundaries and lack of continuous diversion sections, were classified as single retention blocks; approximately 10 low-lying areas, due to the presence of outflow gaps and their alignment with the diversion sections, were segmented into retention blocks connected in series along the slope; the remaining 6 low-lying areas, due to spatial misalignment between their outflow locations and diversion sections, were processed using a double-constraint segmentation method to form composite-constraint retention blocks. The retention blocks obtained through this segmentation method showed a reduction of approximately 32% in runoff collection error under rainfall conditions, and a significantly improved match between the block boundaries and the actual overflow path, exhibiting more stable accumulation and outflow structural characteristics.

[0068] Preferably, monitoring the water level changes of each retention unit under continuous rainfall, determining the overflow turning point when the water level reaches the overflow boundary, and establishing the connectivity between adjacent retention units includes:

[0069] The process of water level rise in each retention unit under continuous rainfall is monitored, and the process of water level approaching the lowest discharge point at the boundary is taken as the critical stage.

[0070] When the water level reaches the critical stage, the point is determined as the overflow turning point, and the local slope corresponding to the overflow turning point is extracted as the direction of runoff outflow.

[0071] Based on the direction of leakage, determine the adjacent retention units into which the runoff enters, and establish a one-way connection between the current retention unit and the adjacent retention units.

[0072] In one embodiment, water level monitoring nodes are deployed in each retention unit within the runoff response unit. These nodes include micro-topographic sampling points in the vicinity of the lowest outflow point at the boundary and internal water depth sampling points, and simultaneously record the rainfall infiltration intensity and the slope runoff inflow intensity. Under continuous rainfall, water level rise curves within each retention unit are obtained at preset sampling intervals, and the local slope changes of the water level curves are analyzed. When the rate of water level rise and the elevation difference of the lowest outflow point at the boundary converge, the corresponding stage is determined as the critical stage of outflow. Within this stage, the local elevation gradient direction at the lowest outflow point at the boundary is extracted, and the preferred outflow path is determined by combining it with the continuous decreasing elevation direction of the neighboring area. The outflow path is then spatially matched with the catchment inlet of the downstream adjacent retention unit to establish a one-way connection relationship from the current retention unit to the target adjacent retention unit, forming a continuous retention unit connection link along the slope potential energy decreasing direction.

[0073] In another embodiment, assuming a slope runoff response unit is divided into 5 adjacent retention units, denoted as L1 to L5, where L1 is located in the uphill runoff initiation zone and L5 is adjacent to the runoff channel inlet; under continuous rainfall for 2 hours, the water level of retention units L1–L3 gradually approaches the lowest outflow point at the boundary, and the elevation difference convergence interval decreases from approximately 35cm to 5cm, indicating the entry into the critical outflow stage; unit L2 reaches the critical outflow state first at the 42nd minute, with its local slope direction at the lowest outflow point pointing towards L3, thus establishing a unidirectional connection between L2 and L3; subsequently, L3 enters the critical outflow stage at the 58th minute, with its outflow direction pointing towards L4, thereby forming a continuous connection link L2→L3→L4; L5, due to its complete boundary closure and water level not reaching the critical outflow condition, does not participate in the connection expansion. Through the step-by-step establishment of the above-mentioned connection relationships, the sequential transmission and spatial constraint solidification of runoff outflow paths between different retention units are achieved.

[0074] Preferably, when the water level reaches the critical stage, this point is determined as the overflow turning point, and the local slope direction corresponding to the overflow turning point is extracted as the direction of runoff outflow, including:

[0075] The process of water level rise within the retention unit is tracked, and the change in elevation difference between the water level and the lowest outflow point at the boundary is calculated.

[0076] When the elevation difference converges to the preset range, the water level is determined to enter the critical state of leakage, and the lowest leakage point at the corresponding boundary is determined as the overflow turning point.

[0077] The elevation distribution of the neighborhood at the overflow turning point is extracted, and the dominant path with continuously decreasing elevation is screened as the candidate direction of runoff leakage.

[0078] Candidate directions are constrained and screened, and directions that are connected to the outside of the retention unit and have a continuous slope are retained and determined as runoff outflow directions.

[0079] In one embodiment, water level observation profiles are deployed along the lowest outflow point and its upstream catchment area within a single retention unit, and local elevation raster data are acquired simultaneously. Under continuous rainfall input, the water level inside the retention unit is continuously tracked, the vertical elevation difference between the current water level and the lowest outflow point is calculated, and a sequence of elevation difference changes is constructed. When the elevation difference change changes from rapid decrease to slow convergence, and the convergence amplitude stabilizes within a preset threshold range, the water body is determined to have entered a critical state of outflow, and the corresponding lowest outflow point is identified as the overflow turning point. A local elevation gradient field is extracted within the neighborhood of the overflow turning point, and multiple potential outflow paths are identified based on gradient continuity. The slope continuity and spatial connectivity of each path are screened, internal closed backflow paths are eliminated, and only the dominant path that has a spatial connection with an external adjacent retention unit or catchment channel is retained. The direction corresponding to the dominant path is determined as the runoff outflow direction.

[0080] In another embodiment, assuming the lowest outflow point elevation within a certain retention unit is 102.3m and the initial water level is 98.0m, after 30 minutes of continuous rainfall, the water level rises to 101.8m, the elevation difference decreases from 4.3m to 0.5m, and then stabilizes within the 0.3–0.6m range for the next 10 minutes, indicating a critical outflow state. In this state, an elevation distribution with a 10m radius around the outflow point is constructed, and three candidate runoff paths are extracted: path A descends 3.2% along the slope but terminates in an internal concave closed area; path B descends 2.8% along the slope and connects to the downstream retention unit inlet; path C descends 1.5% but has a local reverse slope section. After screening for connectivity and slope continuity, only path B meets the external connectivity condition. Therefore, the direction of path B is determined as the runoff outflow direction of this retention unit and is used as the spatial reference for establishing subsequent connectivity relationships.

[0081] Preferably, based on the retention depth parameter and the overflow turning point, the conditions for the transition of runoff from local retention to continuous outflow are determined, the triggering conditions for the stripping of attached pollutants into the water body are identified, and the locations that meet the triggering conditions are determined as pollutant release nodes, including:

[0082] Within the retention unit, the degree of exceedance of the retention depth parameter relative to the lowest outflow point of the boundary is obtained to determine whether the local water body has transitioned from static retention to critical outflow state.

[0083] By combining the local slope changes at the overflow turning point, the acceleration trend of runoff when crossing the overflow turning point is calculated, and the degree of intensification of water flow from the retention area to the outflow channel is determined.

[0084] By matching the retention depth parameter with the degree of flow enhancement, the bottom particles are identified as changing from a pressurized covered state to an exposed state under fluid shearing, which serves as a criterion for the instability of attached contaminants.

[0085] When the attached pollutants reach the instability criterion, the corresponding overflow turning point is determined as the trigger point for the pollutants to be stripped into the water body, and is used as the pollutant release node.

[0086] In one embodiment, water level depth sensors and slope sampling points near the boundary spillway are simultaneously deployed inside the retention unit to acquire retention depth parameters and local slope change information, respectively. Under continuous rainfall, the excess of the retention depth parameter relative to the lowest spillway point is calculated in real time, and an evolution curve of the excess over time is constructed. When the excess changes from stable growth to restricted fluctuation and approaches the control range of the spillway boundary, it is determined that the local water body has changed from static retention to critical spillway state. At the same time, based on the local slope change at the overflow turning point, the velocity increment and acceleration change of the runoff before and after crossing the position are calculated to form a flow enhancement degree parameter. Furthermore, the water pressure corresponding to the retention depth parameter is coupled with the flow enhancement degree for analysis. When the water pressure constraint on the bottom particles is lower than the shear enhancement effect, it is determined that the bottom particles have changed from a pressure-covered state to an exposed unstable state, and the overflow turning point corresponding to this unstable state is determined as the pollutant stripping trigger point, thereby forming a pollutant release node.

[0087] In another embodiment, assuming the lowest outflow point elevation of a certain retention unit boundary is 100.0m, the water level gradually rises from 96.5m to 99.8m during rainfall. At the 45th minute, the relative exceedance of the retention depth parameter reaches 3.2m and enters the fluctuation range of 0.2–0.4m, indicating a critical outflow state. Simultaneously, at the overflow turning point, the local slope increases from 1.8% to 3.5%, corresponding to a flow velocity increase from 0.12m / s to 0.28m / s, indicating a significant enhancement in flow intensification. Under these conditions, the adhesion status of bottom particles is assessed. It is found that when the water level further rises to 99.9m, the shear intensity exceeds the adhesion stability threshold, causing fine particles to change from a covered state to a suspended exposed state. Based on this, the overflow turning point at this moment is determined as the pollutant stripping trigger point, and this location is fixed as the pollutant release node for subsequent runoff transport analysis.

[0088] Preferably, step S3 includes:

[0089] Along the runoff path from the pollutant release node to the confluence channel, the starting particle size of particulate matter under the action of runoff at each location along the path is obtained, and the changes in flow state at the corresponding locations are recorded.

[0090] The critical redeposition size of particulate matter is extracted at locations where runoff is weakened or local diffusion occurs, forming a corresponding distribution relationship between the initiation size and the critical redeposition size along the same path;

[0091] By comparing the initiation particle size with the critical redeposition particle size, the section in which particles repeatedly initiate and redeposition is identified, and this section is determined as the intermittent deposition section.

[0092] Based on the distribution of intermittent depositional zones in the runoff path, the runoff path is segmented into intermittent depositional zones and continuous migration zones, and the transport channels of pollutants are determined along the spatial connectivity of the continuous migration zones.

[0093] In one embodiment, a spatially discrete sampling path is constructed along the pollutant release node to the confluence channel, dividing the runoff path into continuous, equally spaced sampling locations. At each sampling location, flow velocity, flow depth, and bed shear strength parameters are simultaneously acquired to characterize the runoff state. Based on the differences in particle initiation conditions under different flow states, the initiation particle size threshold corresponding to each location is calculated and bound to the local flow state to form an initiation particle size-flow state mapping sequence. At path locations where runoff energy decays or lateral diffusion is enhanced, the re-entry of particles under local backflow and retention conditions is further extracted. The critical deposition size is determined and spatially aligned with the corresponding initiation size to construct a dual-threshold distribution relationship on the same path. When the initiation size in a certain segment is continuously lower than the critical redeposition size and is accompanied by alternating boundary crossings, it is determined that the particles in that segment exhibit repeated initiation and redeposition behavior and are identified as intermittent deposition segments. Furthermore, based on the spatial proportion and distribution continuity of the intermittent deposition segments in the radial connectivity path, the original runoff path is structurally segmented to form intermittent deposition segments and continuous migration segments, and the main transport channel is established along the direction of continuous shear force enhancement in the continuous migration segment.

[0094] In another embodiment, assuming the path length from the pollutant release node to the confluence channel is 200m, it is divided into 20 equidistant sampling segments of 10m each. In the upstream 0–60m range, the flow velocity gradually decreases from 0.35m / s to 0.18m / s, corresponding to a decrease in the initiation particle size from 0.6mm to 0.2mm. In the 60–120m range, due to local micro-topographic depressions forming backflow, the flow velocity fluctuates between 0.10–0.22m / s, at which point the critical re-deposition particle size increases to 0.35–0.5mm. The 5mm particle size exhibited multiple alternating boundary crossings with the initiation particle size, resulting in a total of 7 repeated initiation / deposition switchings, thus classifying this section as an intermittent deposition section. Within the 120–200m range, the flow velocity steadily increased to above 0.40m / s, the initiation particle size remained consistently above 0.7mm, and redeposition conditions ceased, classifying this as a continuous migration section. Based on the spatial continuity of the continuous migration section, the 120–200m path was determined as the main pollutant transport channel, and the interference of the intermittent deposition section on the connectivity of the main channel was excluded.

[0095] Preferably, the initiation particle size is compared with the critical redeposition particle size to identify the section where particles repeatedly initiate and redeposition, and this section is determined as the intermittent deposition section.

[0096] Establish the correspondence between the initiation particle size and the critical redeposition particle size at each location along the runoff path in spatial order, and extract the stress state changes of the same particle size at adjacent locations.

[0097] When the same particle size meets the initiation particle size condition in the upstream position and the redeposition critical particle size condition in the downstream position, it is determined that the particle size is in a state of alternating initiation and redeposition.

[0098] The number of consecutive occurrences of alternating states along the path is counted. When the number of consecutive occurrences reaches a preset number, the corresponding spatial range is determined as the section where particulate matter repeatedly starts and redeposits.

[0099] Using the range of variation between the starting grain size and the critical grain size for redeposition within a section as a constraint, the section boundary is converged to form an intermittent deposition section.

[0100] In one embodiment, a spatial sequence sampling model is established along the runoff path from the pollutant release node to the confluence channel. The path is divided into continuous sampling positions at equal intervals, and bed shear stress, flow velocity, and particle stress state parameters are simultaneously acquired at each position. Based on local hydrodynamic conditions, the particle initiation diameter at the corresponding position is calculated, and the critical redeposition diameter is determined by combining the relationship between the fluid drag force and gravity equilibrium of the particles, thereby establishing a one-to-one correspondence between the initiation diameter and the critical redeposition diameter in the spatial sequence. Furthermore, the state of the same diameter at adjacent positions is tracked, and when the particle diameter is within a certain range... When the upstream position meets the initiation conditions and the downstream position enters the redeposition control zone, it is determined that the grain size has undergone initiation-redeposition alternation behavior, and this alternation state is used as a marker of local transport instability. The continuous occurrence of this marker in the spatial sequence is statistically analyzed. When the number of consecutive occurrences of the alternation state exceeds a preset threshold, the corresponding spatial range is determined as a repeated initiation and redeposition segment. Finally, the fluctuation range of the difference between the initiation grain size and the critical redeposition grain size in this segment is used as a boundary constraint to converge and correct the start and end positions of the segment, forming a stably defined intermittent deposition segment.

[0101] In another embodiment, assuming the path length from the pollutant release node to the confluence channel is 150m, divided into 15 sampling locations at 10m intervals, the flow velocity gradually decreases from 0.32m / s to 0.18m / s within the 0–50m range, corresponding to a decrease in the initiation particle size from 0.55mm to 0.25mm. Within this range, the critical redeposition particle size fluctuates between 0.30–0.45mm, with a typical alternation phenomenon observed in the 3rd to 6th sampling segments: the initiation particle size in the upstream segment is approximately 0.52mm, meeting the initiation condition, while in the downstream segment, the critical redeposition particle size rises to 0.48mm, causing particles to fall back and deposit, forming five consecutive initiation-deposition cycles. The alternation process was observed; within the 50–110m range, the alternation state continuously intensified, with a total of 9 consecutive alternation behaviors, exceeding the preset threshold 6 times, thus identifying this range as a repeated initiation and redeposition zone; within the 110–150m range, the flow velocity steadily increased to above 0.38m / s, the initiation particle size steadily exceeded 0.65mm and the critical redeposition particle size was below 0.40mm, and the alternation state disappeared; based on the fluctuation range of the difference between the initiation particle size and the critical redeposition particle size within the zone (approximately 0.05–0.18mm), the boundary was converged and corrected, and the 50–110m range was identified as an intermittent deposition zone for subsequent identification of continuous migration zones and extraction of transport channels.

[0102] Of particular importance is obtaining the initial particle size of particulate matter under the influence of runoff at each location along the runoff path from the pollutant release node to the confluence channel, and recording the changes in flow state at the corresponding locations, including:

[0103] Divide the runoff path into continuous locations, obtain the state of runoff effect on particles at each location, and mark the locations where the runoff changes from gentle to concentrated or from concentrated to dispersed.

[0104] At each location, the minimum starting particle size is determined based on the critical state at which the particle changes from a stationary state to a state where it can be driven, and the starting particle size is correlated with the runoff state at the corresponding location.

[0105] By continuously comparing the starting particle size at adjacent locations, when the runoff action state changes and the corresponding starting particle size increases or decreases synchronously, that location is determined as the node of change in starting particle size.

[0106] In one embodiment, a discrete spatial path for runoff is constructed from the pollutant release node to the confluence channel, and the path is continuously divided at fixed intervals. Miniature velocity sensing units and bed shear sampling units are deployed at each discrete location to obtain the local runoff state. Through joint analysis of velocity distribution and streamline convergence, the runoff state is divided into gentle diffusion type and concentrated scouring type, and the spatial location where the transition between the two types of states is marked. At each discrete location, the transition of particles from a static state to an initial rolling or jumping state is used as a critical criterion. The corresponding minimum starting particle size is determined by gradually increasing the hydrodynamic input through simulation, and a corresponding mapping relationship between the particle size and the local runoff state is established. Based on this, the starting particle size sequence of adjacent locations is continuously compared. When a certain location simultaneously satisfies the runoff state transition and the starting particle size shows synchronous increase or decrease, the location is determined as the starting particle size change node, which is used to characterize the spatial abrupt change point of runoff transport capacity.

[0107] The present invention also provides a watershed non-point source pollution control system for performing the watershed non-point source pollution control method described above, the watershed non-point source pollution control system comprising:

[0108] The runoff generation response unit identification module 101 is used to deploy monitoring units along the watershed slope to the confluence channel, acquire the location of surface runoff formation and soil moisture state parameters under rainfall conditions, determine the runoff initiation threshold based on the soil moisture state parameters, and identify the runoff generation response units.

[0109] The pollutant release node determination module 102 is used to collect the dispersion and collection process of runoff on the slope in the runoff generation response unit, and to obtain the retention depth parameters and overflow turning points of runoff in the surface depression; based on the retention depth parameters and overflow turning points, the triggering conditions for the transformation of pollutants from the attached state to the migrating state are determined, and the pollutant release node is determined.

[0110] The transport channel determination module 103 is used to obtain the starting particle size and critical redeposition particle size of particulate matter during the runoff scouring process along the runoff path from the pollutant release node to the confluence channel, divide the continuous migration section and intermittent deposition section according to the starting particle size and critical redeposition particle size, and determine the transport channel corresponding to the pollutant.

[0111] The barrier control module 104 is used to deploy barrier control units on the transport channel. The interception position and flux of the barrier control units are adjusted according to the retention depth parameter and the critical particle size for redeposition, so that pollutants are staged and retained before entering the confluence channel.

[0112] 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 controlling non-point source pollution in watersheds, characterized in that, Includes the following steps: Step S1: Deploy monitoring units along the watershed slope to the confluence channel to obtain the location of surface runoff formation and soil moisture state parameters under rainfall conditions. Determine the runoff initiation threshold based on the soil moisture state parameters and identify the runoff generation response units. Step S2: Collect the runoff dispersion and collection process on the slope in the runoff generation response unit, and obtain the retention depth parameters and overflow turning points of the runoff in the surface depression; based on the retention depth parameters and overflow turning points, determine the triggering conditions for the transformation of pollutants from the attached state to the migrating state, and determine the pollutant release nodes. Step S3: Along the runoff path from the pollutant release node to the confluence channel, obtain the starting particle size and critical redeposition particle size of particulate matter during the runoff scouring process, divide the continuous migration section and intermittent deposition section according to the starting particle size and critical redeposition particle size, and determine the transport channel corresponding to the pollutant. Step S4: Deploy barrier control units on the transport channel. Adjust the interception position and flux of the barrier control units according to the retention depth parameter and the critical particle size for redeposition, so that pollutants are staged and retained before entering the confluence channel.

2. The method for preventing and controlling non-point source pollution in a river basin according to claim 1, characterized in that, Step S2 includes: The spatial distribution of surface depressions within the runoff response unit is identified as retention units, and the retention depth parameters of each retention unit are measured. Under continuous rainfall, monitor the water level changes of each retention unit, determine the overflow turning point when the water level reaches the overflow boundary, and establish the connection relationship between adjacent retention units; Based on the retention depth parameter and the overflow turning point, the conditions for the runoff to change from local retention to continuous outflow are determined, the triggering conditions for attached pollutants to be stripped into the water body are identified, and the location that meets the triggering conditions is determined as the pollutant release node.

3. The method for preventing and controlling non-point source pollution in a river basin according to claim 2, characterized in that, Identify the spatial distribution of surface depressions within the runoff response unit, and include them as retention units: Within the runoff response unit, local elevation undulations on the slope are obtained to identify low-lying areas where runoff converges and linear depressions extending along the slope direction. Based on the degree of boundary closure of the low-potential region and the degree of convergence of the linear depression, the flow generation response unit is spatially divided to form stagnation blocks; The elevation difference between the lowest internal point and the lowest outflow point of each retention block is extracted to determine the storage conditions of the retention block under the action of runoff, and retention units that can form stable existence are selected from the retention blocks.

4. The method for preventing and controlling non-point source pollution in a river basin according to claim 3, characterized in that, Based on the degree of boundary closure of the low-potential region and the convergence of the linear concavity, it is spatially divided to form stagnant blocks with independent accumulation constraints, including: Extract the boundary elevation continuity within the low-potential area, determine whether there is a boundary leakage gap in the low-potential area based on the boundary elevation continuity, and mark the corresponding leakage location; Analyze the convergence of the elevations on both sides towards the centerline along the direction of the linear depression to identify whether a continuous guide section is formed and determine the extension path of the guide section. When there is no boundary leakage gap in the low-potential area and the linear depression does not form a continuous flow section, the entire area is divided by the boundary enclosure range to form a single retention block. When a low-potential area has a boundary leakage gap and a linear depression forms a continuous diversion section, the low-potential area is divided along the diversion path with the continuous diversion section as the boundary, forming a retention block connected sequentially along the runoff direction. When the boundary leakage gap and the linear concave diversion section coexist but do not form a corresponding relationship, the boundary is divided by the intersection of the leakage location and the diversion section as a common constraint, so that the dividing boundary passes through both the leakage control point and the runoff collection location.

5. The method for preventing and controlling non-point source pollution in a river basin according to claim 2, characterized in that, Monitoring water level changes in each retention unit under continuous rainfall, determining the overflow turning point when the water level reaches the overflow boundary, and establishing connectivity between adjacent retention units include: The process of water level rise in each retention unit under continuous rainfall is monitored, and the process of water level approaching the lowest discharge point at the boundary is taken as the critical stage. When the water level reaches the critical stage, the point is determined as the overflow turning point, and the local slope corresponding to the overflow turning point is extracted as the direction of runoff outflow. Based on the direction of leakage, determine the adjacent retention units into which the runoff enters, and establish a one-way connection between the current retention unit and the adjacent retention units.

6. The method for preventing and controlling non-point source pollution in a river basin according to claim 5, characterized in that, When the water level reaches the critical stage, this point is determined as the overflow turning point, and the local slope direction corresponding to the overflow turning point is extracted as the direction of runoff outflow, including: The process of water level rise within the retention unit is tracked, and the change in elevation difference between the water level and the lowest outflow point at the boundary is calculated. When the elevation difference converges to the preset range, the water level is determined to enter the critical state of leakage, and the lowest leakage point at the corresponding boundary is determined as the overflow turning point. The elevation distribution of the neighborhood at the overflow turning point is extracted, and the dominant path with continuously decreasing elevation is screened as the candidate direction of runoff leakage. Candidate directions are constrained and screened, and directions that are connected to the outside of the retention unit and have a continuous slope are retained and determined as runoff outflow directions.

7. The method for preventing and controlling non-point source pollution in a river basin according to claim 2, characterized in that, Based on the retention depth parameters and overflow inflection points, the conditions for the transition of runoff from local retention to continuous outflow are determined, the triggering conditions for attached pollutants to be stripped and enter the water body are identified, and the locations that meet the triggering conditions are determined as pollutant release nodes, including: Within the retention unit, the degree of exceedance of the retention depth parameter relative to the lowest outflow point of the boundary is obtained to determine whether the local water body has transitioned from static retention to critical outflow state. By combining the local slope changes at the overflow turning point, the acceleration trend of runoff when crossing the overflow turning point is calculated, and the degree of intensification of water flow from the retention area to the outflow channel is determined. By matching the retention depth parameter with the degree of flow enhancement, the bottom particles are identified as changing from a pressurized covered state to an exposed state under fluid shearing, which serves as a criterion for the instability of attached contaminants. When the attached pollutants reach the instability criterion, the corresponding overflow turning point is determined as the trigger point for the pollutants to be stripped into the water body, and is used as the pollutant release node.

8. The method for preventing and controlling non-point source pollution in a river basin according to claim 1, wherein, Step S3 includes: Along the runoff path from the pollutant release node to the confluence channel, the starting particle size of particulate matter under the action of runoff at each location along the path is obtained, and the changes in flow state at the corresponding locations are recorded. The critical redeposition size of particulate matter is extracted at locations where runoff is weakened or local diffusion occurs, forming a corresponding distribution relationship between the initiation size and the critical redeposition size along the same path; By comparing the initiation particle size with the critical redeposition particle size, the section in which particles repeatedly initiate and redeposition is identified, and this section is determined as the intermittent deposition section. Based on the distribution of intermittent depositional zones in the runoff path, the runoff path is segmented into intermittent depositional zones and continuous migration zones, and the transport channels of pollutants are determined along the spatial connectivity of the continuous migration zones.

9. The method for preventing and controlling non-point source pollution in a river basin according to claim 8, characterized in that, By comparing the initiation particle size with the critical redeposition particle size, the region where particles repeatedly initiate and redeposition is identified, and this region is designated as the intermittent deposition region. Establish the correspondence between the initiation particle size and the critical redeposition particle size at each location along the runoff path in spatial order, and extract the stress state changes of the same particle size at adjacent locations. When the same particle size meets the initiation particle size condition in the upstream position and the redeposition critical particle size condition in the downstream position, it is determined that the particle size is in a state of alternating initiation and redeposition. The number of consecutive occurrences of alternating states along the path is counted. When the number of consecutive occurrences reaches a preset number, the corresponding spatial range is determined as the section where particulate matter repeatedly starts and redeposits. Using the range of variation between the starting grain size and the critical grain size for redeposition within a section as a constraint, the section boundary is converged to form an intermittent deposition section.

10. A system for preventing and controlling non-point source pollution in a river basin, characterized in that, For performing the watershed non-point source pollution control method as described in claim 1, the watershed non-point source pollution control system comprises: The runoff generation response unit identification module is used to deploy monitoring units along the watershed slope to the confluence channel, obtain the location of surface runoff formation and soil moisture state parameters under rainfall conditions, determine the runoff initiation threshold based on the soil moisture state parameters, and identify the runoff generation response units. The pollutant release node determination module is used to collect the dispersion and collection process of runoff on the slope in the runoff generation response unit, and to obtain the retention depth parameters and overflow turning points of runoff in the surface depressions; based on the retention depth parameters and overflow turning points, the triggering conditions for the transformation of pollutants from the attached state to the migrating state are determined, and the pollutant release nodes are determined. The transport channel determination module is used to obtain the initiation particle size and critical redeposition particle size of particulate matter during the runoff scouring process along the runoff path from the pollutant release node to the confluence channel, divide the continuous migration section and intermittent deposition section according to the initiation particle size and critical redeposition particle size, and determine the transport channel corresponding to the pollutant. The barrier control module is used to deploy barrier control units on the transport channel. The interception position and flux of the barrier control units are adjusted according to the retention depth parameter and the critical particle size for redeposition, so that pollutants are staged and retained before entering the confluence channel.

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