Optimal selection method for plain river network polder area water environment scheduling scheme based on network flow

Abstract

The invention relates to a network flow-based plain river network polder area water environment scheduling scheme optimization method. The method comprises the steps of generalizing a target polder area water system to obtain a network flow model; processing the water conservancy project facilities in the target polder area water system according to a preset process and forming a water conservancy project facility scheduling scheme optimization set; according to the water conservancy project facility dispatching scheme optimization set, screening is conducted according to preset indexes, and the preset indexes are the dead water river reach proportion, the river reach flow passing rate or specific river reach running water; and finally, obtaining a corresponding optimal hydraulic engineering facility scheduling scheme under each preset index. According to the method, a water system communication optimization technical scheme with universality is constructed based on the complex water system characteristics of the polder area of the plain river network from the network flow theory, corresponding optimal water conservancy project facility scheduling schemes under different preset indexes can be obtained, the polder area water resource utilization efficiency can be improved through an intelligent technical means, and the water resource utilization rate of the polder area can be improved. And the polder area water environment quality is improved.

Description

Technical Field

[0001] The invention relates to a method for optimizing a water environment dispatching scheme for a plain river network embankment area based on network flow, and belongs to the technical field of ecological and environmental protection intelligence. Background Art

[0002] In plain river network areas, in order to meet the needs of flood control, irrigation, water supply, etc., local people have built a large number of polder areas. The construction of polder areas has significantly changed the physical form, hydrological characteristics and ecological functions of the natural river network, forming a composite river network system composed of natural and artificial water bodies. With the acceleration of urbanization and industrialization, the development and transformation of river and lake water systems within the polder areas has intensified, and the river network structure has tended to be simplified and trunked, which not only reduces the natural regulation capacity of the river network system, damages the aquatic ecological environment, but also increases the risk of floods. Pumping stations and sluice gates and other water conservancy facilities are built on the boundaries of the polder areas. The water systems inside and outside the polder areas are relatively independent. The water volume exchange between the inside and outside of the polder areas mainly relies on artificial regulation, which to a certain extent restricts the free exchange of water bodies inside and outside the polder areas and increases the pressure on the water environment and water ecosystem within the polder areas. In recent years, with the growing needs of the people for a better ecological environment, the expectation for water management has shifted from ensuring water safety to creating a healthy water ecology and water environment and building happy rivers and lakes. Quantitatively assessing the current connectivity of the water system in the polder area, optimizing the layout of the river and lake water system in the polder area, and comprehensively dispatching and managing existing water conservancy facilities are of great significance for improving the connectivity of the water system structure in the polder area, achieving orderly flow of water bodies, and improving the water environment quality in the polder area.

[0003] In recent years, domestic and foreign scholars have conducted a lot of research on the connotation, evaluation and optimization of river-lake water system connectivity. Research on water system connectivity evaluation and optimization methods has made a lot of progress. It can be found that the current research on river-lake water system connectivity at home and abroad presents the following characteristics and trends: (1) Multidisciplinary cross-cutting trend: The research on river-lake water system connectivity presents a multidisciplinary cross-cutting trend, covering multiple fields such as hydrology and hydrodynamics, landscape ecology, river geomorphology and complex networks. For example, hydrology and hydrodynamics provide accurate simulations of water flow processes, landscape ecology focuses on the impact of connectivity on biodiversity, and complex network theory is used to analyze the overall structure and function of water system networks.

[0004] (2) Diverse evaluation methods and indicator systems: There are many evaluation methods and indicator systems for water system connectivity evaluation, mainly using graph theory, landscape ecology, hydrology and hydrodynamics, etc. to construct a comprehensive evaluation indicator system to comprehensively evaluate the water system from the aspects of morphology, structure and function. Specifically, graph theory evaluates water system connectivity by analyzing the relationship between nodes and edges, landscape ecology evaluates ecological connectivity and its impact on biological habitats, and hydrology and hydrodynamics simulates the flow and exchange process of water bodies.

[0005] (3) Multi-objective and model-based optimization methods: In the study of water system connectivity optimization methods, hydrological and hydrodynamic models are currently used for simulation and optimization. Some scholars have also introduced methods such as graph models and complex networks to carry out multi-objective optimization. The optimization method not only focuses on the connectivity of the water system, but also takes into account the needs of multiple aspects such as ecological environment and water resources management.

[0006] Although research has made progress, there are still some key issues that need to be resolved: previous studies at home and abroad have mainly focused on large rivers and regional backbone water systems, and there are relatively few studies on water system connectivity in small-scale areas such as plain river network embankments. The current planning and design of embankment water systems relies more on empirical decision-making, lacks sufficient theoretical support, and some optimization schemes may only consider local connectivity without fully considering the potential impact on the entire water system. Hydrological and hydrodynamic models are commonly used and effective tools for optimizing water system functional connectivity, but they have high data requirements, complex model construction, and high cost of use; in plain river network areas, the water flow rate is small and the hydrological monitoring data is relatively small, which usually makes it difficult to meet the needs of hydrodynamic model construction; the use of hydrodynamic models to optimize river and lake water system structure and water conservancy project scheduling schemes is limited in large-scale promotion and application in plain river network embankments.

[0007] Therefore, it is urgent to study the optimal method for sluice and pump scheduling schemes in the dike area, so as to improve the connectivity of the water system structure in the dike area, realize the orderly flow of water in the dike area, and improve the water environment quality in the dike area. Summary of the invention

[0008] The main purpose of the present invention is to overcome the problems existing in the prior art, provide a method for optimizing the water environment scheduling scheme in the plain river network embankment area based on network flow, and obtain the corresponding optimal water conservancy project facility scheduling scheme under different preset indicators, which is conducive to the improvement of the embankment area water system by intelligent technical means.

[0009] The technical solution of the present invention to solve the technical problem is as follows: The method for optimizing the water environment dispatching scheme of a plain river network polder area based on network flow is characterized by comprising the following steps: The first step is to generalize the water system of the target embankment area to obtain a network flow model; The second step is to process the water conservancy engineering facilities in the target polder area water system according to the preset process and form an optimal set of water conservancy engineering facilities scheduling plans; The third step is to screen the optimal set of water conservancy project facility scheduling plans according to preset indicators, such as the proportion of dead water river sections, the flow rate of river sections, or the living water of specific river sections; finally, the optimal water conservancy project facility scheduling plans corresponding to each preset indicator are obtained.

[0010] This method starts from the network flow theory and is based on the complex water system characteristics of the plain river network embankment. By optimizing the water system connectivity, it obtains the corresponding optimal water conservancy project facility scheduling plan under different preset indicators. It is of great significance to improve the water resource utilization efficiency of the embankment area with intelligent technical means, improve the connectivity of the water system structure in the embankment area, realize the orderly flow of water bodies in the embankment area, and improve the water environment quality in the embankment area.

[0011] The technical solution further improved by the present invention is as follows: Preferably, the network flow model includes nodes, edges, directions of edges, and capacities of edges; The nodes include at least one of the water system intersection, isolated point, hanging point, source point and sink point. The isolated point is generalized from an independent water area, the hanging point is generalized from a small water area connected to only one waterway, the source point is generalized from the water inlet of the polder area, and the sink point is generalized from the water flow intersection point in the polder area or the water outlet of the polder area. Edges represent the paths of water flow, which are generalized from natural river sections, artificial waterways or water conservancy facilities in the water system of the polder area. Artificial waterways include channels and culverts, and water conservancy facilities include sluices, pumping stations and gate stations. The direction of the edge represents the directionality and stability of the water flow at this edge, including at least one of unidirectional, periodic unidirectional, and bidirectional. Among them, the direction of the edge is unidirectional, which means that the direction of the water flow at this edge remains constant for a long time; the direction of the edge is periodic unidirectional, which means that the direction of the water flow at this edge is determined within the preset research period under the influence of external factors; the direction of the edge is bidirectional, which means that the direction of the water flow at this edge is uncertain due to the flat terrain, complex water conditions and the influence of human activities; The capacity of an edge represents the flow capacity of this edge during the non-flood season and is determined by the maximum flow capacity corresponding to the controlled water level of the polder area.

[0012] More preferably, in the network flow model, the edge constraints include: capacity constraints, flow conservation constraints, and non-negative flow constraints; The capacity constraint is: for each edge in the network flow model, its flow cannot exceed the capacity, that is: ; In the above formula, For edge of traffic, For edge The capacity, edge The two endpoints are nodes and nodes , For edge A collection of; The flow conservation constraint is: except for the source and sink, for each node in the network flow model , the total inflow is equal to the total outflow, that is: ; The non-negative flow constraint is: for each edge in the network flow model, its flow must be non-negative, that is: .

[0013] In the network flow model, the edge Capacity The flow capacity corresponding to the average width of the river section is used As an approximate substitution, the calculation formula and the hydraulic parameters involved are as follows: ; ; ; ; In the above formulas, is the average width of the river section; It is the difference between the highest controlled water level and the lowest controlled water level in the dike; is the cross-sectional area of ​​water flow; For wet week; is the hydraulic radius; is the slope coefficient; is the hydraulic slope; is the river channel roughness; It is Xie Cai coefficient.

[0014] More preferably, the network flow model further includes an auxiliary source point and auxiliary meeting point , auxiliary source point As the only water source entrance, auxiliary confluence point As the only outlet of water flow; the auxiliary source point Connect to each original source point through edges with preset capacity. The preset capacity of these edges represents the amount of energy from the auxiliary source point to the original source point. The maximum possible flow rate of water between each original source point; connect each original sink point to the auxiliary sink point through an edge with a preset capacity , the preset capacity of these edges represents the flow of water from each original sink to the auxiliary sink In this way, the original multi-source and multi-sink network is transformed into a single source network. To a single point This transformation simplifies the structure of the network, making it easier to analyze and solve using the maximum flow algorithm.

[0015] More preferably, the network flow model adopts a maximum flow algorithm with Ford-Fulkerson algorithm as the core, and the maximum flow algorithm includes the following steps: S1. Initialize the flow of each edge in the network to 0; where the edge is , and the edge The flow rate is ; S2. According to the current flow , construct the residual network ; Each edge in the residual network The capacity of is the capacity of the corresponding edge in the original network The difference is ; For each edge , and the remaining network also includes a reverse edge , whose capacity is ; S3. In the remaining network Find the auxiliary source point To auxiliary meeting point The path is the augmenting path; when searching, the depth-first search DFS algorithm or the breadth-first search BFS algorithm is used.

[0016] S4. For the augmented path found, calculate the minimum remaining capacity of all edges on the path, denoted as ; Then update the flow along the augmenting path; The specific process of updating the flow is: for each positive edge on the augmenting path , increase traffic ; For each reverse edge on the path , reduce traffic ; S5. Update the remaining networks based on the new traffic distribution ; S6, repeat S3 to S5 until no auxiliary source point can be found in the remaining network To auxiliary meeting point When no augmenting path is found, the algorithm terminates. To auxiliary meeting point The flow rate is the maximum flow.

[0017] By adopting the above preferred scheme, the specific technical features of the first step can be further optimized.

[0018] Preferably, the preset process of the second step is: T1. The maximum flow rate of each water conservancy project facility is used as the capacity constraint of its corresponding edge; the maximum flow rate of the pump station is determined by the flow capacity of its pump; the gate opening of the sluice station and the sluice is set to a preset value according to the actual water level of the target embankment area; the maximum flow rate of the sluice is determined by the flow capacity of the gate; for the sluice station, the maximum flow rate of the sluice station during drainage is determined by the flow capacity of the pump, and the maximum flow rate of the sluice station during water diversion is determined by the flow capacity of the gate; T2. Assuming that the water flow direction changes with the change of water conservancy project facility scheduling, the sluice gate is used as a water diversion facility, the pump station is used as a drainage facility, and the sluice station is used as a water diversion facility or drainage facility as needed; according to the principle that drainage facilities should be opened when water diversion facilities are opened to maintain water flow balance, the water diversion facilities and drainage facilities are combined to list a set of water conservancy project facility scheduling plans to form an initial plan set; T3. In the initial plan set, the water conservancy project facility scheduling plan is screened according to the following process: i. For the hydraulic engineering facility dispatching scheme that includes a sluice-pump integrated sluice station, if the scheme uses the sluice-pump integrated sluice station as both a water diversion facility and a drainage facility, the scheme shall be removed; ii. For each water conservancy project facility scheduling plan, list all water diversion paths from the water diversion facilities to the drainage facilities. If the length of any water diversion path is less than the preset value, remove the plan; iii. For a water conservancy project facility scheduling scheme with only one diversion facility and one drainage facility, that is, a single diversion and single drainage scheme, if the diversion flow rate of the scheme is lower than the preset value, the scheme will be eliminated; The water conservancy project facility scheduling plans obtained after screening form an optimal set of water conservancy project facility scheduling plans.

[0019] By adopting the above preferred scheme, the specific technical features of the second step can be further optimized.

[0020] Preferably, in the third step, the proportion of dead water river sections is recorded as , which means: under a certain water conservancy project facility scheduling plan, when the polder network reaches the maximum flow, the total length of the river section with a flow of 0 accounts for the proportion of the total river section length; the specific calculation formula is as follows: ; In this formula, is the total length of the river section with zero flow; is the length of the total river section; The flow rate of a river section is recorded as , which means: under a certain water conservancy project facility scheduling plan, when the polder network reaches the maximum flow, the weighted average of the flow-to-capacity ratio of each river section, and its weight is calculated according to the proportion of the length of each river section to the total length of the river section; the specific calculation formula is as follows: ; In this formula, For the The flow rate of the river section; For the The capacity of the river section; For the Length of the river section; is the total length of the river section.

[0021] More preferably, when the preset indicator is the proportion of dead water river sections, the proportion of dead water river sections in each water conservancy project facility scheduling plan is calculated, and by comparison, the water conservancy project facility scheduling plan with the lowest proportion of dead water river sections is obtained, which means that the plan performs best in improving the connectivity of the water system in the dike area, helps to improve the overall water environment quality of the dike area, and enhances the self-purification capacity of the water body; this plan is used as the optimal result with the proportion of dead water river sections as the indicator.

[0022] Specific practice shows that not all schemes that maximize water flow can effectively improve the hydrodynamic conditions in the polder area. Although some schemes can achieve a large flow rate, the distribution of such flow may not be conducive to the hydrodynamic activity of the entire polder area. The water flow may be concentrated in only a few river channels, rather than being widely distributed throughout the polder area. Therefore, when the scheduling target is to minimize the dead water range in the polder area, the preset indicator should be set as the proportion of dead water river sections, so as to screen out the scheme that performs best in improving the connectivity of the water system.

[0023] More preferably, when the preset indicator is the river section flow rate, the river section flow rate of each water conservancy project facility scheduling plan is calculated, and the water conservancy project facility scheduling plan with the highest river section flow rate is obtained by comparison. This represents that the plan performs best in terms of the overall fluidity of the river channel in the embankment area, and helps to ensure that the water flow in the river channel in the embankment area passes through a larger flow rate, the water flow velocity increases, the river flow area increases, the river flow velocity increases, the hydraulic retention time is short, the water body self-purification capacity is greater, the river flow cross-sectional area is larger, the wet perimeter is larger, and the living space for aquatic organisms is larger; this plan is used as the optimal result with the river section flow rate as the indicator.

[0024] More preferably, when the preset indicator is the running water of a specific river section, a plan for achieving running water in the specific river section when the polder network reaches the maximum flow is selected from the various water conservancy project facility scheduling plans; if there are more than two plans, the water conservancy project facility scheduling plan with the lowest proportion of dead water river sections or the highest river section flow passing rate is selected from these plans; and this plan is used as the preferred result with the running water of the specific river section as the indicator.

[0025] By adopting the above preferred scheme, the specific technical features of the third step can be further optimized.

[0026] Compared with the existing technology, the present invention starts from the network flow theory and is based on the complex water system characteristics of the plain river network embankment area to construct a universal water system connectivity optimization technical solution. It has been verified to be effective and practical, and can obtain the corresponding optimal water conservancy project facility scheduling plan under different preset indicators. It is of great significance to improve the water resource utilization efficiency of the embankment area, improve the connectivity of the water system structure in the embankment area, realize the orderly flow of water bodies in the embankment area, and improve the water environment quality in the embankment area. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is an example diagram of an undirected graph and a directed graph according to Embodiment 1 of the present invention.

[0028] Figure 2 This is a schematic diagram of a typical plain river network embankment area in Example 1 of the present invention.

[0029] Figure 3 This is an example diagram of converting a multi-source and multi-sink network into a single-source and single-sink network according to Embodiment 1 of the present invention.

[0030] Figure 4 This is a schematic diagram of the general situation of the polder area in Example 2 of the present invention.

[0031] Figure 5 This is a generalized schematic diagram of the water system in the polder area of ​​Example 2 of the present invention.

[0032] Figure 6 Schematic diagram of the maximum flow rate and the proportion of dead water sections in different scheduling schemes for the polder area in Example 2 of the present invention.

[0033] Figure 7 This is a schematic diagram of the dispatching scheme F19 (ensuring water diversion from Gangbei Sluice Gate and Beizhuang Taosluice Gate, and drainage from Qizhuang Pumping Station and Wujinbang Sluice Station) of Example 2 of the present invention.

[0034] Figure 8 This is a schematic diagram of the dispatching scheme F25 (water diversion from Wujinbang Sluice Station and Beizhuang Taozha, drainage from Qizhuang Pumping Station and Baogang North Sluice Station) of Example 2 of the present invention.

[0035] Fig. 9 This is a schematic diagram of the maximum flow rate and the flow rate through the river section in different scheduling schemes of the polder area in Example 2 of the present invention.

[0036] Fig.10 It is a schematic diagram of the dispatching scheme F10 (water diversion through Beizhuang Taozha, drainage through Qizhuang Pumping Station and Baogang North Sluice Station) of Example 2 of the present invention.

[0037] Fig.11 This is a schematic diagram of the dispatching scheme F12 (water diversion at Beizhuangtaozha and drainage at Baogangbeizha Station and Wujinbangzha Station) of Example 2 of the present invention.

[0038] Fig.12This is a schematic diagram of the dispatching scheme F13 (water diversion through Beizhuang Taozha; drainage through Qizhuang Pumping Station, Baogang North Sluice Station and Wujinbang Sluice Station) of Example 2 of the present invention. DETAILED DESCRIPTION

[0039] In specific implementation, the method for optimizing the water environment scheduling scheme of a plain river network polder area based on network flow of the present invention comprises the following steps: The first step is to generalize the water system of the target embankment area to obtain a network flow model.

[0040] The network flow model includes nodes and edges. Nodes include at least one of water system intersection points, isolated points, hanging points, source points and sink points, where isolated points are generalized from independent water areas, hanging points are generalized from small water areas connected to only one waterway, source points are generalized from water inlets in the polder area, and sink points are generalized from water flow intersection points or water outlets in the polder area; edges represent the paths of water flow, which are generalized from natural river sections, artificial waterways or water conservancy engineering facilities in the polder area water system, where artificial waterways include channels and culverts, and water conservancy engineering facilities include sluices, pumping stations and sluice stations.

[0041] The network flow model also includes the direction and capacity of the edge. The direction of the edge represents the directionality and stability of the water flow on this edge, including at least one of unidirectional, periodic unidirectional, and bidirectional. Among them, if the direction of the edge is unidirectional, it means that the flow direction of the water flow on this edge remains constant for a long time; if the direction of the edge is periodic unidirectional, it means that the flow direction of the water flow on this edge is determined within the preset research period under the influence of external factors (such as water conservancy project regulation or water system reconstruction); if the direction of the edge is bidirectional, it means that the flow direction of the water flow on this edge is uncertain due to the flat terrain, complex water conditions and human activities. The capacity of the edge represents the flow capacity of this edge in the non-flood season, and is determined by the maximum flow capacity corresponding to the water level controlled by the polder area.

[0042] In this network flow model, the edge constraints include: capacity constraint, flow conservation constraint, and non-negative flow constraint; among them, The capacity constraint is: for each edge in the network flow model, its flow cannot exceed the capacity, that is: ; In the above formula, For edge of traffic, For edge The capacity, edge The two endpoints are nodes and nodes , For edge A collection of .

[0043] The flow conservation constraint is: except for the source and sink, for each node in the network flow model , the total inflow is equal to the total outflow, that is: ; The non-negative flow constraint is: for each edge in the network flow model, its flow must be non-negative, that is: ; In this network flow model, the edge Capacity The flow capacity corresponding to the average width of the river section is used As an approximate substitution, the calculation formula and the hydraulic parameters involved are as follows: ; ; ; ; In the above formulas, is the average width of the river section; It is the difference between the highest controlled water level and the lowest controlled water level in the dike; is the cross-sectional area of ​​water flow; For wet week; is the hydraulic radius; is the slope coefficient; is the hydraulic slope; is the river channel roughness; It is Xie Cai coefficient.

[0044] The network flow model also has auxiliary source points and auxiliary meeting point , auxiliary source point As the only water source entrance, auxiliary confluence point As the only outlet of water flow; the auxiliary source point Connect to each original source point through edges with preset capacity. The preset capacity of these edges represents the amount of energy from the auxiliary source point to the original source point. The maximum possible flow rate of water between each original source point; connect each original sink point to the auxiliary sink point through an edge with a preset capacity , the preset capacity of these edges represents the flow of water from each original sink to the auxiliary sink In this way, the original multi-source and multi-sink network is transformed into a single source network. To a single point This transformation simplifies the structure of the network, making it easier to analyze and solve using the maximum flow algorithm.

[0045] In this network flow model, the flow saturation path on the maximum flow path between two nodes is the cut edge, which represents the bottleneck river section. These edges are the key factors that limit the maximum flow; the maximum flow of the network is equal to the sum of the flows on the cut edges; the minimum cut is to divide the network into two non-intersecting subsets, and make the auxiliary source point To auxiliary meeting point A set of cut edges that minimizes the flow.

[0046] The network flow model adopts the maximum flow algorithm with Ford-Fulkerson algorithm as the core, which includes the following steps: S1. Initialize the flow of each edge in the network to 0; where the edge is , and the edge The flow rate is .

[0047] S2. According to the current flow , construct the residual network ; Each edge in the residual network The capacity of is the capacity of the corresponding edge in the original network The difference is ; For each edge , and the remaining network also includes a reverse edge , whose capacity is .

[0048] S3. In the remaining network Find the auxiliary source point To auxiliary meeting point , that is, the augmenting path.

[0049] When searching, use the depth-first search DFS algorithm or the breadth-first search BFS algorithm.

[0050] S4. For the augmented path found, calculate the minimum remaining capacity of all edges on the path, denoted as ; Then update the flow along the augmenting path.

[0051] The specific process of updating the flow is: for each positive edge on the augmenting path , increase traffic ; For each reverse edge on the path , reduce traffic .

[0052] S5. Update the remaining networks based on the new traffic distribution .

[0053] S6, repeat S3 to S5 until no auxiliary source point can be found in the remaining network To auxiliary meeting point When no augmenting path is found, the algorithm terminates. To auxiliary meeting point The flow rate is the maximum flow.

[0054] The second step is to process the water conservancy engineering facilities within the target embankment water system according to the preset process and form an optimal set of water conservancy engineering facilities scheduling plans.

[0055] The default process is: T1. The maximum flow rate of each water conservancy project facility is taken as the capacity constraint of its corresponding edge; among them, the maximum flow rate of the pump station is determined by the flow capacity of its pump; the gate opening of the sluice station and the sluice is set to a preset value according to the actual water level of the target embankment area; the maximum flow rate of the sluice is determined by the flow capacity of the gate; for the sluice station, the maximum flow rate of the sluice station during drainage is determined by the flow capacity of the pump, and the maximum flow rate of the sluice station during water diversion is determined by the flow capacity of the gate.

[0056] T2. Assuming that the direction of water flow changes with the change of water conservancy project facility scheduling, the sluice gate is used as a water diversion facility, the pump station is used as a drainage facility, and the sluice station is used as a water diversion facility or drainage facility as needed; according to the principle that when the water diversion facility is opened, the drainage facility must be opened to maintain the water flow balance, the water diversion facility and the drainage facility are combined to list a set of water conservancy project facility scheduling plans to form an initial plan set.

[0057] T3. In the initial plan set, the water conservancy project facility scheduling plan is screened according to the following process: i. For the hydraulic engineering facility dispatching scheme that includes a sluice-pump integrated sluice station, if the scheme uses the sluice-pump integrated sluice station as both a water diversion facility and a drainage facility, the scheme shall be removed; ii. For each water conservancy project facility scheduling plan, list all water diversion paths from the water diversion facilities to the drainage facilities. If the length of any water diversion path is less than the preset value, remove the plan; iii. For a water conservancy project facility scheduling scheme with only one diversion facility and one drainage facility, that is, a single diversion and single drainage scheme, if the diversion flow rate of the scheme is lower than the preset value, the scheme will be eliminated; The water conservancy project facility scheduling plans obtained after screening form an optimal set of water conservancy project facility scheduling plans.

[0058] The third step is to screen the optimal set of water conservancy project facility scheduling plans according to preset indicators, such as the proportion of dead water river sections, the flow rate of river sections, or the living water of specific river sections; finally, the optimal water conservancy project facility scheduling plans corresponding to different preset indicators are obtained.

[0059] In the third step, the proportion of dead water sections is recorded as , which means: under a certain water conservancy project facility scheduling plan, when the polder network reaches the maximum flow, the total length of the river section with a flow of 0 accounts for the proportion of the total river section length; the specific calculation formula is as follows: ; In this formula, is the total length of the river section with zero flow; is the total length of the river section.

[0060] The flow rate of a river section is recorded as , which means: under a certain water conservancy project facility scheduling plan, when the polder network reaches the maximum flow, the weighted average of the flow-to-capacity ratio of each river section, and its weight is calculated according to the proportion of the length of each river section to the total length of the river section; the specific calculation formula is as follows: ; In this formula, For the The flow rate of the river section; For the The capacity of the river section; For the Length of the river section; is the total length of the river section.

[0061] When the preset indicator is the proportion of dead water river sections, the proportion of dead water river sections in each water conservancy project facility scheduling plan is calculated, and the water conservancy project facility scheduling plan with the lowest proportion of dead water river sections is obtained through comparison. This means that this plan performs best in improving the connectivity of the water system in the dike area, which helps to improve the overall water environment quality of the dike area and enhance the self-purification capacity of the water body. This plan is used as the optimal result with the proportion of dead water river sections as the indicator.

[0062] Specific practice shows that not all schemes that maximize water flow can effectively improve the hydrodynamic conditions in the polder area. Although some schemes can achieve a large flow rate, the distribution of such flow may not be conducive to the hydrodynamic activity of the entire polder area. The water flow may be concentrated in only a few river channels, rather than being widely distributed throughout the polder area. Therefore, when the scheduling target is to minimize the dead water range in the polder area, the preset indicator should be set as the proportion of dead water river sections, so as to screen out the scheme that performs best in improving the connectivity of the water system.

[0063] When the preset indicator is the river section flow rate, the river section flow rate of each water conservancy project facility scheduling plan is calculated, and the water conservancy project facility scheduling plan with the highest river section flow rate is obtained by comparison. This means that the plan has the best performance in the overall fluidity of the river channel in the embankment area, the water flow velocity in the river channel increases, the hydraulic residence time is short, the self-purification capacity of the water body is greater, the cross-sectional area of ​​the river channel is larger, the wetted perimeter is larger, and the living space of aquatic organisms is larger; this plan is used as the optimal result with the river section flow rate as the indicator.

[0064] When the preset indicator is the running water of a specific river section, a plan for achieving running water in the specific river section when the polder network reaches the maximum flow is selected from the various water conservancy project facility scheduling plans; if there are more than two plans, the water conservancy project facility scheduling plan with the lowest proportion of dead water river sections or the highest river section flow passing rate is selected from these plans; this plan is used as the optimal result with the running water of the specific river section as the indicator.

[0065] The present invention will be described in further detail below with reference to the accompanying drawings and in combination with embodiments, but the present invention is not limited to the examples given.

[0066] Example 1 This embodiment is the construction of a network flow model for a polder area.

[0067] The specific contents of this embodiment are as follows: 1. Definition and concept of graph (1) Definition of graph set up is a non-empty set of finite vertices, where It is an edge set. The set of unordered pairs of some elements in , consisting of the vertex set and edge sets The two-tuple It is called a graph and is denoted by .in is the set of nodes in the network; is the set of edges in the network. The graph defined above is called an undirected graph. If the edges have directions, it is called a directed graph, denoted by Examples of undirected and directed graphs are Figure 1 shown.

[0068] In addition, the node The number of edges with endpoints is called the degree of the node, denoted by , a point with degree 0 is called an isolated point, a point with degree 1 is called a hanging point, an edge of a hanging point is called a hanging edge, a point with an odd degree is called an odd point, and a point with an even degree is called an even point. For a directed graph, it is called the out-degree and in-degree of a node, and the node The out-degree is is the directed edge from the starting node (i.e. from the vertex The number of directed edges starting from ;node The in-degree is The directed edge that is the end point (i.e., the edge that enters the node The number of directed edges of .

[0069] (2) Weighted Graph For directed graphs , if the graph Each of Assign weight , then the directed graph after assignment is a weighted graph, which can be written as .

[0070] 2. Basic concepts of network flow model (1) Capacity network Given a weighted graph ,in is a collection of nodes, is the edge set, is the capacity function of the edge, and the graph satisfies the following conditions: 1) In the node collection There are two special node subsets in the source point set and the collection of meeting points . Source point set All nodes in have 0 in-degree, and the sink set All nodes in have 0 out-degree; 2) Each edge in are assigned a non-negative real value As the capacity of the edge, it means that the edge The maximum flow that can be carried.

[0071] (2) Feasible flow exist In each edge There is a flow , the collection of these flows is called a flow on the network. A flow is called a feasible flow if it satisfies the following conditions: 1) Capacity limitation: Each edge in , ,in It is the edge Capacity; 2) Flow conservation: For Any non-source and non-sink point , inflow The total flow is equal to the outflow The total flow of the source point Hehuidian , the total flow out of the source is equal to the total flow into the sink.

[0072] (3) Cut If there exists an edge set yes A subset of Can be split into two sub-graphs and , whose node sets are and ,satisfy , , and the source point belong , Meeting Point belong , and the following conditions are met: 1) is non-connected; 2) There is a yes A proper subset of are connected.

[0073] Then it is called for The cut set of . cut set All starting points in , the end point is The sum of the capacities of the edges is called The cut set capacity of In the capacity network There may be multiple cut sets in the network, among which the cut set with the smallest capacity is called the network The minimum cut of .

[0074] From the definition of cut set, we can see that in the capacity network, the cut set represents the To the meeting point If any cut set is removed, the source point Hehuidian Therefore, the flow of any feasible flow will not exceed the capacity of any cut set.

[0075] (4) Augmenting Path An augmenting path is a path from a source to a sink that can increase the flow of the network. This means that if there is a path from a source to a sink such that each edge on the path can carry the additional flow, i.e., it has not reached its capacity limit, then this path can be considered an augmenting path. The process of adding flow on an augmenting path increases the total flow from the source to the sink until one of the edges reaches its capacity limit and can no longer add more flow.

[0076] (5) Residual Network The residual network is a concept related to the original network flow graph, used to consider the flow that has already flowed through the network when finding augmenting paths. The residual network consists of all the nodes and edges in the original network, but the edge capacities are adjusted according to the flow of the original network.

[0077] For each edge in the original network , if its capacity is And the current flow is , then in the residual network, the residual capacity of this edge is This indicates how much more flow can be added through this edge without exceeding the capacity limit.

[0078] In addition, the residual network also introduces reverse edges. For each edge in the original network , there will be a line in the remaining network from arrive The reverse edge of This means that traffic that has already flowed can be partially or completely withdrawn in order to redistribute this traffic to other paths in the network.

[0079] 3. Construction of network flow model in polder area The polder area is an important way to develop and utilize the plain river network area. The polder area is built by building dams along the river and lake, digging ditches inside, and building water conservancy facilities such as pumping stations and sluices on the border. The water system is relatively independent. The water exchange between the inside and outside of the polder area mainly relies on artificial regulation. The polder area can block external water flow during floods to prevent flood invasion. At the same time, it can draw water inward through sluice pumps during the dry season to ensure water use within the polder. Typical plain river network polder areas, such as Figure 2 As shown in the figure, the basic structure and layout of the water conservancy project in the polder area are shown. Among them, the dike is the most important protective facility in the polder area. It can not only block external floods, but also prevent the internal water body from leaking out. The ditch is used for water flow regulation inside the polder area to ensure the needs of irrigation and drainage. Pumping stations and sluices are key facilities for controlling the inflow and outflow of water. They jointly maintain the balance of water levels inside and outside the polder area and ensure the normal operation of the polder area. The polder area not only improves the flood control capacity and land use efficiency of specific areas, but also plays an important role in maintaining ecological balance, protecting biodiversity and promoting regional economic and social development.

[0080] The water network of the plain river network polder area mainly includes the intersection of river branches, small water areas (such as lakes, ponds, etc.) and water conservancy engineering facilities (such as sluices, pumping stations, bridges and culverts, etc.). The three main components of the polder area network flow model are: nodes, edges, and the direction and capacity of edges. Nodes are divided into water system intersection points, isolated points (independent water areas), hanging points (small water areas connected to only one waterway), source points (water inlets of polder areas) and confluence points (intersection points, water outlets of polder areas) according to their functions and location characteristics. Natural river sections and artificial waterways (such as channels, culverts, etc.) in the water system are abstracted as edges, representing the path of water flow. In order to facilitate the construction and solution of the model, water conservancy engineering facilities such as sluices and pumps can be generalized as edges in the model. Depending on the stability and direction of the water flow, these sides can be unidirectional (for waterways with a long-term constant flow direction), periodic unidirectional (waterways with a fixed flow direction during a preset research period due to factors such as water conservancy project regulation or water system reconstruction), or bidirectional (in areas with flat terrain, complex water conditions, and greater impact from human activities, the flow direction of some rivers is uncertain). In the non-flood season, the flow capacity (capacity) of each side is determined by the maximum flow capacity corresponding to the controlled water level of the polder area.

[0081] The maximum flow capacity of the river corresponding to the controlled water level of the polder area is taken as the capacity constraint of the edge. When the maximum flow of the polder area water system network is evaluated under different gate pump dispatching, the optimal dispatching scheme of the polder area is obtained by optimizing the index. The specific constraints of the edge are as follows: (1) Capacity constraints: For each edge in the network ,flow Cannot exceed the capacity of the edge .

[0082] ; (2) Flow conservation constraints: Except source point Hehuidian In addition, each node in the network The total inflow is equal to the total outflow.

[0083]

[0084] (3) Non-negative flow constraint: The flow on each edge in the network must be non-negative.

[0085]

[0086] Edge Capacity Flow capacity corresponding to the average width of the available river section Approximately, the hydraulic parameters involved are as follows: ; ; ; ; In the formula, is the average width of the river section; It is the difference between the highest controlled water level and the lowest controlled water level in the dike; is the cross-sectional area of ​​water flow; For wet week; is the hydraulic radius; is the slope coefficient; is the hydraulic slope; is the river channel roughness; It is Xie Cai coefficient.

[0087] In order to facilitate the solution of the network flow model, the water network is further constructed and mathematically processed. Two special vertices are added to the original water network, namely the source point Hehuidian , source point As the only water source entrance of the entire network, the confluence point It is the only outlet of water flow in the network. Connect to each source node of the original network through edges with preset capacities. The preset capacities of these edges represent the The maximum possible flow rate of water between each source. Similarly, each sink is connected to the sink through an edge with a preset capacity. The preset capacities of these edges represent the flow of water from within the network to the final sink. Through the above steps, the original multi-source and multi-sink network is converted into a single source point. To a single point This transformation simplifies the structure of the network, making it easier to analyze and solve using the maximum flow algorithm. For ease of understanding, an example is Figure 3 As shown in Figure a, where Figure a is a multi-source multi-sink network, with source points A and D, sink points C and F, and auxiliary source points are added to facilitate maximum flow calculation Hehuidian , converted to b-graph, the number on the left in the bracket on the edge in the graph represents the flow of the edge, and the number on the right represents the capacity of the edge.

[0088] The flow saturation paths on the maximum flow path between two nodes are called cut edges, which can also be called water bottleneck sections. These edges are the key to limiting the maximum flow. Figure 3As shown in Figure b, the saturated capacity edges are (A→B), (D→B), (E→F), and (B→F). The maximum flow of the network is equal to the sum of the flows on the cut edges, but not all saturated paths constitute the minimum cut, which is a set of cut edges that divides the network into two disjoint subsets and minimizes the flow from the source node to the sink node. Therefore, the minimum cuts in the figure are (A→B), (D→B), and (E→F), and their maximum flow is 10.

[0089] 4. Ford-Fulkerson algorithm The maximum flow of a network aims to find the maximum flow that can pass from a given source point to a given sink point in a directed network, that is, from arrive The flow rate reaches the maximum feasible flow. The present invention adopts the Ford-Fulkerson algorithm to calculate the maximum flow. The core idea is to continuously find and augment the augmenting path until no augmenting path can be found. At this time, the flow is the maximum flow. The specific steps are as follows: (1) Initialization flow Initialize each edge in the network Traffic is 0. This means that initially, no traffic passes through the network.

[0090] (2) Constructing the residual network According to the current flow , construct the residual network . Each edge in the remaining network The capacity of is the capacity of the corresponding edge in the original network The difference is For each edge , and the remaining network also includes a reverse edge , whose capacity is .

[0091] (3) Finding augmenting paths In the remaining network Find the source point To the meeting point Such a path is called an augmenting path because it can be used to increase the number of arrive The total flow of . You can use depth-first search (DFS) or breadth-first search (BFS) to find such a path.

[0092] (4) Increase traffic For the augmented path found, calculate the minimum remaining capacity of all edges on the path, denoted as Then, update the flow along the augmenting path: for each positive edge on the path , increase traffic For each reverse edge on the path , reduce traffic .

[0093] (5) Update the remaining network Update the remaining networks based on the new traffic distribution This may result in some new augmenting paths appearing, or some original augmenting paths no longer being available.

[0094] (6) Output maximum flow Repeat the search for augmenting paths, augmenting flows, and updating the remaining network until no augmenting paths from arrive When no augmenting path is found, the algorithm terminates. To the meeting point The flow rate is the maximum flow.

[0095] 5. Analysis and visualization tools The visualization of the complex network of river network water system involves a large number of nodes and edges, as well as the complex relationship between these elements. In order to effectively represent this complexity and visualize it, some existing tools and software such as Gephi, Cytoscape, NetworkX, igraph, etc. can be used. These tools not only support the basic visualization of the network, but also provide advanced functions such as layout optimization, interactivity and in-depth analysis of the network structure. This embodiment selects igraph and ggraph packages based on R language to analyze and visualize the complex network of river network water system. igraph is one of the most popular network analysis and visualization packages in R language, providing rich functions, including the creation, modification, visualization of the network and complex analysis of the network structure and dynamics. Ggraph is based on the syntax of ggplot2, providing a flexible and expressive way to create network diagrams, inheriting the ease of use, high customizability and beautiful graphic design of ggplot2.

[0096] Example 2 This embodiment is an example of applying the technical solution of the present invention to a practical scenario.

[0097] The water quality of rivers and lakes in the polder area and the health of the ecosystem are directly related to agricultural production, residents' lives and the protection of biodiversity. Sluice and pump scheduling is an important means to regulate the water exchange inside and outside the polder area and the water quality of the water body inside the polder area. Running water scheduling is an important means to improve the fluidity of water bodies and improve the water ecological environment. Different scheduling schemes will affect the flow path and distribution method of water, thereby affecting the utilization efficiency of water resources. By accurately controlling the operation of sluices and pumps, the internal water circulation of the polder area can be promoted and the water quality can be improved.

[0098] (I) This embodiment takes a certain connected weir in a typical weir area of ​​a town as an example.

[0099] The polder area has problems such as low-lying terrain, unreasonable water system layout, dense hydraulic structures and single dispatching scheme, which lead to poor water flow, deterioration of water ecological environment and insufficient flood control and drainage capacity. These problems not only affect the normal function of the polder area, but also pose a threat to the quality of life of local residents and the sustainable development of the region. By optimizing the river network layout, improving drainage capacity, improving dispatching schemes and strengthening water ecological environment management, the water environment and water ecology of the polder area can be effectively improved and the sustainable development of the polder area can be achieved.

[0100] The focus of this embodiment is to construct a network flow model of the polder area for the example polder area, optimize the gate and pump scheduling plan, and improve the functional connectivity of the polder area water system.

[0101] 2. Overview of the Lianwei and the generalization of the water system The total area of ​​the Lianwei is 6.57km², which belongs to the mixed wei area and is a common wei in the Taihu Lake Basin. Figure 4 As shown. The highest elevation in the weir is 5m and the lowest is 3.2m. The highest controlled water level in the weir is 2.9m and the lowest is 2.4m. The average water level in the weir is 2.45m. The average water level of the river outside the weir is 3.24m, the highest is 4.47m (2021.7.28), and the lowest is 2.74m (2021.2.22). Due to the low ground elevation in the weir, the normal water level of the river outside the weir is higher than the ground elevation in the weir all year round. The water volume inside and outside the weir is mainly exchanged through pump stations and sluices, and the living water in the weir area is realized by the method of gate diversion and pumping. There are 2 water diversion gates (Bao Gangdong Gate and Beizhuang Set Gate) in the weir area, 1 drainage pump station (Qi Zhuang Pumping Station), and 2 integrated diversion and drainage gate stations (Bao Gangbei Gate Station and Wujinbang Gate Station). The specific information is shown in Table 1 below. There are 14 rivers in the dike, the main function of which is to divert water and drain water. Considering the gentle terrain of the dike area, the small gradient of the river channel, and the roughly similar river channel morphology, referring to the relevant research on plain river network, The hydraulic slope is 0.0008. The roughness coefficient of the river channel is taken as 0.03.

[0102] Table 1. Basic information of the Lianwei sluice pump

[0103] After generalization, the liaison has 33 nodes and 36 edges. Figure 5 The edges (5,6) are for the Baogangbei Sluice Station, (7,13) are for the Baogangdong Sluice Station, (16,9) are for the Beizhuang Sluice Station, (32,31) are for the Wujinbang Sluice Station, (14,33) are for the Qizhuang Pumping Station, and the remaining edges are river sections, as shown in Table 2.

[0104] Table 2. Generalized basic information of the Lianwei water system

[0105] (III) Multi-sluice pump joint dispatching scheme set The dike area uses sluice gates and pumps to discharge live water. The limiting capacity of the side corresponding to the sluice pump is taken as its maximum flow rate. Taking into account the water level inside and outside the dike, the gate opening is taken as 0.5m. See Table 3 for details.

[0106] Table 3: Overview of the Lianwei sluice pump

[0107] Assuming that the direction of water flow changes with the change of gate pump scheduling, a set of optimized gate pump scheduling schemes for the embankment area is proposed. Each open water diversion gate requires at least one corresponding drainage pump station to be opened to maintain the balance of water flow. All possible water diversion and drainage combinations are listed. After calculation, there are 105 gate pump scheduling schemes. Considering that the gate pumps of Baogang North Gate Station and Wujinbang Gate Station are integrated, it is impossible to divert and discharge at the same time, and the water diversion path of Baogang North Pump Station is too short after the water diversion of Baogang East Gate, and the single diversion and single discharge effect is not good, a total of 28 gate pump scheduling schemes were finally screened out, as shown in Table 4 below.

[0108] Table 4. Dispatching plan for the sluice pump of the Lianwei

[0109] (IV) Optimal Scheduling Scheme 1. Proportion of dead water sections Proportion of dead water river sections ( ), defined as the ratio of the total length of the river section with zero flow to the total length of the river section when the polder network reaches the maximum flow under different scheduling schemes. The specific calculation formula is as follows: ;

[0110] In the formula is the total length of the river section with zero flow (unit: m); is the total length of the river section (unit: m).

[0111] This indicator reflects the effect of the scheduling scheme in improving the connectivity of the water system. The lower the proportion of dead water river sections, the more river sections can be kept flowing by the scheme. By comparing the proportion of dead water river sections of different schemes, the scheme with the best performance in improving the connectivity of the water system can be screened out, which will help improve the overall water environment quality of the polder area and enhance the self-purification capacity of the water body.

[0112] The calculation results of the maximum flow rate of different dispatching schemes in the polder area and the proportion of dead water sections in the polder area are as follows: Figure 6As shown in the figure, the blue bar graph is the maximum flow rate of the polder area, and the red broken line is the proportion of dead water sections in the polder area under different schemes. Overall, the maximum flow rate of the polder area does not correspond to the proportion of dead water sections in the largest polder area, which shows that not all schemes that maximize water flow can effectively improve the hydrodynamic conditions in the polder area. Although some sluice pump scheduling schemes can achieve a large flow rate, this flow distribution may not be conducive to the hydrodynamic activity of the entire polder area. The water flow may only be concentrated in a few rivers, rather than being widely distributed throughout the polder area.

[0113] Among them, the maximum flow rate of scheme F19 is the largest, reaching 6.81m 3 / s, the dead water section accounts for 49.45%, indicating that the water is diverted through Baogang North Gate and Beizhuang Gate, and discharged through Qizhuang Pumping Station and Wujinbang Gate Station, which will cause Songjia Port, Zhongwang Port and Xiongji Port in the middle of the embankment area to be unable to flow water. Figure 7 In the scheme F25, the dead water section accounts for 20.43% of the area, and the maximum flow rate is 6.05m 3 / s, water is diverted through Wujinbang Sluice Station and Beizhuang Sluice Station, and discharged through Qizhuang Pumping Station and Baogang North Sluice Station. The maximum flow value of this scheme is smaller than that of schemes F16, F19 and F22, but under this scheme, Songjiagang and Zhongwanggang in the middle of the polder area have achieved running water, and the proportion of dead water river sections in the polder area is the lowest. Figure 8 As shown. In general, Scheme F25 can achieve a larger range of active water while ensuring a higher flow rate, effectively improving the hydrodynamic conditions and ecological environment quality in the polder area. Therefore, when the scheduling target is to minimize the dead water range in the polder area, Scheme F25 can be considered as the optimal sluice pump scheduling scheme for the polder area.

[0114] 2. Flow rate of river section Flow rate of river section ( ), defined as the weighted average of the flow-to-capacity ratios of each river section when the polder network reaches maximum flow under different dispatching schemes, where the weight is calculated based on the ratio of each river section length to the total river section length. The specific calculation formula is as follows: ;

[0115] In the formula For the Flow rate of the river section (unit: m 3 / s); For the The capacity of the river section (unit: m 3 / s); For the The length of the river section (unit: m); is the total length of the river section (unit: m).

[0116] This indicator reflects the overall utilization efficiency of river capacity under different scheduling schemes. The higher the ratio, the greater the actual flow velocity of the river under the condition of a certain head difference inside and outside the dike, the larger the cross-sectional area of ​​the river, the larger the wetted perimeter, the shorter the hydraulic retention time, and the higher the self-purification capacity of the water body. By analyzing the changes in the flow rate of the river section under different schemes, the optimal water conservancy facility scheduling scheme can be identified.

[0117] After calculation, the maximum flow rate of different dispatching schemes in the polder area and the flow rate of the river section are as follows: Fig. 9 As shown in the figure, the river section utilization rate of scheduling scheme F25 is the highest, which is 47.60%. Therefore, considering the flow rate of the river section, scheme 25 can be considered as the optimal sluice pump scheduling scheme.

[0118] 3. Flowing water in specific river sections In the above preferred schemes, Xiongji Harbor did not achieve running water. This shows that only considering the proportion of dead water river sections in the polder area and the flow rate of the river section cannot fully achieve running water in the polder area. In the simulation process, it was found that schemes F10, F12 and F13 can achieve running water in Xiongji Harbor. See details. Fig.10 , Fig.11 , Fig.12 Scheme F10 mainly diverts water through Beizhuang sluice gate, passes through Qizhuang pump station, and ensures discharge from Gangbei pump station, with a maximum flow value of 4.32m 3 / s, the dead water section in the embankment area accounts for 58.91%, and the flow rate of the section is 30.07%; Scheme F12 diverts water through Zhuangtao Gate and discharges it through Baogang North Pump Station and Wujinbang Gate Station, with a maximum flow value of 4.32m 3 / s, the dead water section in the embankment area accounts for 61.47%, and the flow rate of the section is 25.69%; Scheme F13 is discharged through Beizhuang Taozha Qizhuang Pump Station, Baogang North Pump Station, and Wujinbang, with a maximum flow value of 4.32m 3 / s, the proportion of dead water in the polder area is 61.47%, and the flow rate of the river section is 25.69%. The overall dispatching ideas and routes of the three schemes are relatively similar, and all can realize the living water of Xiongji Port. Comparing the living water range and river utilization rate of the polder area, Scheme F10 is selected as the living water scheme of Xiongji Port.

[0119] Based on the above embodiments, the present invention starts from the network flow theory and is based on the complex water system characteristics of the plain river network embankment area to construct a universal water system connectivity optimization technical solution, which has been verified to be effective and practical, and can obtain the corresponding optimal water conservancy project facility scheduling plan under different preset indicators. It is of great significance to improve the water resource utilization efficiency of the embankment area, improve the connectivity of the water system structure in the embankment area, realize the orderly flow of water bodies in the embankment area, and improve the water environment quality in the embankment area.

[0120] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A method for optimizing water environment scheduling schemes in plain river network polder areas based on network flow, characterized by: The following steps are involved: The first step is to generalize the water system of the target polder area to obtain a network flow model; The second step is to process the water conservancy engineering facilities in the target polder area water system according to the preset process and form an optimal set of water conservancy engineering facilities scheduling plans; The third step is to screen the optimal set of water conservancy project facility scheduling plans according to preset indicators, such as the proportion of dead water river sections, the flow rate of river sections, or the living water of specific river sections; finally, the optimal water conservancy project facility scheduling plans corresponding to each preset indicator are obtained.

2. The method for optimizing the water environment scheduling scheme of a plain river network polder area based on network flow according to claim 1 is characterized in that: The network flow model includes nodes, edges, edge directions, and edge capacities; The nodes include at least one of the water system intersection, isolated point, hanging point, source point and sink point. The isolated point is generalized from an independent water area, the hanging point is generalized from a small water area connected to only one waterway, the source point is generalized from the water inlet of the polder area, and the sink point is generalized from the water flow intersection point in the polder area or the water outlet of the polder area. Edges represent the paths of water flow, which are generalized from natural river sections, artificial waterways or water conservancy facilities in the water system of the polder area. Artificial waterways include channels and culverts, and water conservancy facilities include sluices, pumping stations and gate stations. The direction of the edge represents the directionality and stability of the water flow at this edge, including at least one of unidirectional, periodic unidirectional, and bidirectional. Among them, the direction of the edge is unidirectional, which means that the direction of the water flow at this edge remains constant for a long time; the direction of the edge is periodic unidirectional, which means that the direction of the water flow at this edge is determined within the preset research period under the influence of external factors; the direction of the edge is bidirectional, which means that the direction of the water flow at this edge is uncertain due to the flat terrain, complex water conditions and the influence of human activities; The capacity of an edge represents the flow capacity of this edge during the non-flood season and is determined by the maximum flow capacity corresponding to the controlled water level of the polder area.

3. The method for optimizing the water environment scheduling scheme of a plain river network polder area based on network flow according to claim 1 is characterized in that: In the network flow model, the edge constraints include: capacity constraints, flow conservation constraints, and non-negative flow constraints; The capacity constraint is: for each edge in the network flow model, its flow cannot exceed the capacity, that is: ； In the above formula, For edge of traffic, For edge The capacity, edge The two endpoints are nodes and nodes , For edge A collection of; The flow conservation constraint is: except for the source and sink, for each node in the network flow model , the total inflow is equal to the total outflow, that is: ； The non-negative flow constraint is: for each edge in the network flow model, its flow must be non-negative, that is: ； In the network flow model, the edge Capacity The flow capacity corresponding to the average width of the river section is used As an approximate substitution, the calculation formula and the hydraulic parameters involved are as follows: ； ； ； ； In the above formulas, is the average width of the river section; It is the difference between the highest controlled water level and the lowest controlled water level in the dike; is the cross-sectional area of ​​water flow; For wet week; is the hydraulic radius; is the slope coefficient; is the hydraulic slope; is the river channel roughness; It is Xie Cai coefficient.

4. The method for optimizing the water environment scheduling scheme of a plain river network polder area based on network flow according to claim 3 is characterized in that: The network flow model also has an auxiliary source point and auxiliary meeting point , auxiliary source point As the only water source entrance, auxiliary confluence point As the only outlet of water flow; the auxiliary source point Connect to each original source point through edges with preset capacity. The preset capacity of these edges represents the amount of energy from the auxiliary source point to the original source point. The maximum possible flow rate of water between each original source point; connect each original sink point to the auxiliary sink point through an edge with a preset capacity , the preset capacity of these edges represents the flow of water from each original sink to the auxiliary sink ability.

5. The method for optimizing the water environment scheduling scheme of a plain river network area based on network flow according to claim 3 is characterized in that: The network flow model adopts a maximum flow algorithm with the Ford-Fulkerson algorithm as the core, and the maximum flow algorithm includes the following steps: S1. Initialize the flow of each edge in the network to 0; where the edge is , and the edge The flow rate is ; S2. According to the current flow , construct the residual network ; Each edge in the residual network The capacity of is the capacity of the corresponding edge in the original network The difference is ; For each edge , and the remaining network also includes a reverse edge , whose capacity is ; S3. In the remaining network Find the auxiliary source point To auxiliary meeting point The path is the augmenting path; when searching, the depth-first search DFS algorithm or the breadth-first search BFS algorithm is used; S4. For the augmented path found, calculate the minimum remaining capacity of all edges on the path, denoted as ; Then update the flow along the augmenting path; The specific process of updating the flow is: for each positive edge on the augmenting path , increase traffic ; For each reverse edge on the path , reduce traffic ; S5. Update the remaining networks based on the new traffic distribution ; S6, repeat S3 to S5 until no auxiliary source point can be found in the remaining network To auxiliary meeting point When no augmenting path is found, the algorithm terminates. To auxiliary meeting point The flow rate is the maximum flow.

6. The method for optimizing the water environment scheduling scheme of a plain river network polder area based on network flow according to claim 3 is characterized in that: The default process for the second step is: T1. The maximum flow rate of each water conservancy project facility is used as the capacity constraint of its corresponding edge; the maximum flow rate of the pump station is determined by the flow capacity of its pump; the gate opening of the sluice station and the sluice is set to a preset value according to the actual water level of the target embankment area; the maximum flow rate of the sluice is determined by the flow capacity of the gate; for the sluice station, the maximum flow rate of the sluice station during drainage is determined by the flow capacity of the pump, and the maximum flow rate of the sluice station during water diversion is determined by the flow capacity of the gate; T2. Assuming that the water flow direction changes with the change of water conservancy project facility scheduling, the sluice gate is used as a water diversion facility, the pump station is used as a drainage facility, and the sluice station is used as a water diversion facility or drainage facility as needed; according to the principle that drainage facilities should be opened when water diversion facilities are opened to maintain water flow balance, the water diversion facilities and drainage facilities are combined to list a set of water conservancy project facility scheduling plans to form an initial plan set; T3. In the initial plan set, the water conservancy project facility scheduling plan is screened according to the following process: i. For the hydraulic engineering facility dispatching scheme that includes a sluice-pump integrated sluice station, if the scheme uses the sluice-pump integrated sluice station as both a water diversion facility and a drainage facility, the scheme shall be removed; ii. For each water conservancy project facility scheduling plan, list all water diversion paths from the water diversion facilities to the drainage facilities. If the length of any water diversion path is less than the preset value, remove the plan; iii. For a water conservancy project facility scheduling scheme with only one diversion facility and one drainage facility, that is, a single diversion and single drainage scheme, if the diversion flow rate of the scheme is lower than the preset value, the scheme will be eliminated; The water conservancy project facility scheduling plans obtained after screening form an optimal set of water conservancy project facility scheduling plans.

7. The method for optimizing the water environment scheduling scheme of a plain river network area based on network flow according to claim 3 is characterized in that, in the third step, the proportion of dead water river sections is recorded as , which means: under a certain water conservancy project facility scheduling plan, when the polder network reaches the maximum flow, the total length of the river section with a flow of 0 accounts for the proportion of the total river section length; the specific calculation formula is as follows: ； In this formula, is the total length of the river section with zero flow; is the length of the total river section; The flow rate of a river section is recorded as , which means: under a certain water conservancy project facility scheduling plan, when the polder network reaches the maximum flow, the weighted average of the flow-to-capacity ratio of each river section, and its weight is calculated according to the proportion of the length of each river section to the total length of the river section; the specific calculation formula is as follows: ； In this formula, For the The flow rate of the river section; For the The capacity of the river section; For the Length of the river section; is the total length of the river section.

8. The method for optimizing the water environment scheduling scheme of a plain river network area based on network flow according to claim 7 is characterized in that: When the preset indicator is the proportion of dead water river sections, the proportion of dead water river sections in each water conservancy project facility scheduling plan is calculated, and the water conservancy project facility scheduling plan with the lowest proportion of dead water river sections is obtained through comparison; this plan is used as the optimal result with the proportion of dead water river sections as the indicator.

9. The method for optimizing the water environment scheduling scheme of a plain river network area based on network flow according to claim 7 is characterized in that: When the preset indicator is the river section flow rate, the river section flow rate of each water conservancy project facility scheduling plan is calculated, and the water conservancy project facility scheduling plan with the highest river section flow rate is obtained through comparison; this plan is used as the optimal result with the river section flow rate as the indicator.

10. The method for optimizing the water environment scheduling scheme of a plain river network polder area based on network flow according to claim 7 is characterized in that: When the preset indicator is the running water of a specific river section, a plan for achieving running water in the specific river section when the polder network reaches the maximum flow is selected from the various water conservancy project facility scheduling plans; if there are more than two plans, the water conservancy project facility scheduling plan with the lowest proportion of dead water river sections or the highest river section flow passing rate is selected from these plans; this plan is used as the optimal result with the running water of the specific river section as the indicator.

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