Optimization Method for Water Environment Regulation Scheme in Plain River Network Polder Area Based on Network Flow

Abstract

The present invention relates to an optimization method for water environment scheduling schemes in plain river network polder areas based on network flow, including: generalizing the water system of the target polder area to obtain a network flow model; processing the water conservancy project facilities in the water system of the target polder area according to a preset process and forming an optimization set of water conservancy project facility scheduling schemes; screening according to the optimization set of water conservancy project facility scheduling schemes according to preset indicators, and the preset indicators are the proportion of dead river sections, the passing rate of river section flow, or the flowing water in specific river sections; finally, obtaining the optimized water conservancy project facility scheduling schemes corresponding to each preset indicator. Starting from the network flow theory and based on the complex water system characteristics of plain river network polder areas, the present invention constructs a general water system connectivity optimization technical scheme, which can obtain the optimized water conservancy project facility scheduling schemes corresponding to different preset indicators, and is conducive to improving the water resource utilization efficiency of polder areas and enhancing the water environment quality of polder areas by means of intelligent technologies.

Description

Technical Field

[0001] The present invention relates to a method for optimizing the water environment scheduling scheme of plain river network polder areas based on network flow, belonging to the field of ecological environmental intelligence technology. Background Art

[0002] In the plain river network area, 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 natural river networks, forming a composite river network system composed of natural and artificial water bodies. With the acceleration of the urbanization and industrialization processes, the development and transformation of the internal river and lake water systems in polder areas have intensified, and the river network structure tends to be simplified and trunkified. This not only reduces the natural regulation ability of the river network system, damages the aquatic ecological environment, but also increases the flood risk. Water conservancy facilities such as pumping stations and sluices are built at the polder boundaries, and the water systems inside and outside the polders are relatively independent. The water volume exchange between the inside and outside of the polder mainly relies on artificial regulation, which to a certain extent restricts the free exchange of water bodies inside and outside the polder and increases the pressure on the water environment and water ecosystem inside the polder. In recent years, with the increasing need of the people for a beautiful ecological environment, the expectation for water control has changed from ensuring water safety to creating a healthy water ecology and water environment and building happy rivers and lakes. Quantitatively evaluating the current status of water system connectivity in polder areas, optimizing the layout of river and lake water systems in polder areas, and comprehensively scheduling and managing existing water conservancy facilities are of great significance for improving the connectivity of the water system structure in polder areas, realizing the orderly flow of water bodies, and enhancing the water environment quality in polder areas.

[0003] In recent years, domestic and foreign scholars have conducted relatively many studies on the connotation of river and lake water system connectivity, water system connectivity evaluation, and water system connectivity optimization. Considerable progress has been made in the research on water system connectivity evaluation and optimization methods. It can be found that the current domestic and foreign research on river and lake water system connectivity presents the following characteristics and trends:

[0004] (1) Trend of multidisciplinary intersection: The research on river and lake water system connectivity shows a trend of multidisciplinary intersection, covering multiple fields such as hydrology and hydrodynamics, landscape ecology, fluvial geomorphology, and complex networks. For example, hydrology and hydrodynamics provide accurate simulation of the water flow process, landscape ecology focuses on the impact of connectivity on biodiversity, and complex network theory is used to analyze the overall structure and function of the water system network.

[0005] (2) Diversified evaluation methods and index systems: In terms of water system connectivity evaluation, there are many evaluation methods and index systems. Mainly using methods such as graph theory method, landscape ecology method, and hydrology and hydrodynamics method, a comprehensive evaluation index system is constructed to comprehensively evaluate from aspects such as the morphology, structure, and function of the water system. Specifically, the graph theory method evaluates water system connectivity by analyzing the relationship between nodes and edges, the landscape ecology method evaluates ecological connectivity and its impact on biological habitats, and the hydrology and hydrodynamics method simulates the water body flow and exchange process.

[0006] (3) Multi-objectivization and modeling of optimization methods: In the research on the optimization method of water system connectivity, currently, hydrological and hydrodynamic models are mainly 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 the ecological environment and water resources management.

[0007] Although progress has been made in the research, there are still some key issues to be solved: Previous studies at home and abroad mainly focused on large rivers and regional backbone water systems, and relatively few studies were conducted on the water system connectivity of small-scale areas such as plain river network polder areas. Currently, the water system planning and design in polder areas rely more on empirical decisions, lacking sufficient theoretical support. Moreover, some optimization schemes may only consider local connectivity and do not fully consider the potential impact on the entire water system. The hydrological and hydrodynamic model is a commonly used and effective tool for optimizing the functional connectivity of the water system, but it has high data requirements, complex model construction, and high usage costs; in the plain river network area, the water velocity is small, and there are few hydrological monitoring data, usually making it difficult to well meet the requirements for the construction of hydrodynamic models; the application of hydrodynamic models to optimize the structure of river and lake water systems and the scheduling scheme of water conservancy projects is restricted in large areas of plain river network polder areas.

[0008] . Therefore, it is urgent to study an optimal selection method for the sluice and pump scheduling scheme in polder areas, so as to improve the connectivity of the water system structure in polder areas, realize the orderly flow of water bodies in polder areas, and improve the water environment quality in polder areas. Summary of the Invention

[0009] The main purpose of the present invention is: to overcome the problems existing in the prior art, and provide an optimal selection method for the water environment scheduling scheme of plain river network polder areas based on network flow, which can obtain the optimal scheduling scheme of water conservancy project facilities corresponding to different preset indicators, and is conducive to realizing the improvement of the water system in polder areas by means of intelligent technology.

[0010] The technical solution for the present invention to solve its technical problems is as follows:

[0011] An optimal selection method for the water environment scheduling scheme of plain river network polder areas based on network flow, characterized by including the following steps:

[0012] First step, generalize the water system of the target polder area to obtain a network flow model;

[0013] Second step, process the water conservancy project facilities in the water system of the target polder area according to a preset process and form an optimal selection set of water conservancy project facility scheduling schemes;

[0014] Third step, screen according to the optimal selection set of water conservancy project facility scheduling schemes according to a preset indicator, and the preset indicator is the proportion of dead river sections, the flow passing rate of river sections, or living water in specific river sections; finally, obtain the optimal scheduling scheme of water conservancy project facilities corresponding to each preset indicator.

[0015] . Starting from the network flow theory and based on the complex water system characteristics of the plain river network polder area, through the optimization of water system connectivity, the corresponding optimal scheduling schemes of water conservancy project facilities under different preset indicators are obtained, which is of great significance for improving the water resource utilization efficiency in the polder area by means of intelligent technology, improving the connectivity of the water system structure in the polder area, realizing the orderly flow of water bodies in the polder area, and enhancing the water environment quality in the polder area.

[0016] The further improved technical solution of the present invention is as follows:

[0017] Preferably, the network flow model includes nodes, edges, the direction of the edges, and the capacity of the edges;

[0018] The nodes include at least one of water system confluence points, isolated points, hanging points, source points, and sink points. Among them, the isolated points are generalized from independent water areas, the hanging points are generalized from small water areas connected to only one watercourse, the source points are generalized from the inlet of the polder area, and the sink points are generalized from the confluence points of water flows in the polder area or the outlet of the polder area;

[0019] The edges represent the paths of water flows, which are generalized from natural river sections, artificial waterways, or water conservancy project facilities in the polder area water system. Among them, the artificial waterways include channels and culverts, and the water conservancy project facilities include sluices, pumping stations, and sluice stations;

[0020] The direction of the edge represents the water flow directionality and its stability of this edge, including at least one of unidirectional, periodically unidirectional, and bidirectional; among them, when the direction of the edge is unidirectional, it means that the water flow direction of this edge remains constant for a long time; when the direction of the edge is periodically unidirectional, it means that the water flow direction of this edge is determined within the preset research period under the influence of external factors; when the direction of the edge is bidirectional, it means that the water flow direction of this edge is uncertain due to the gentle terrain, complex water conditions, and human activities;

[0021] The capacity of the edge represents the water flow passing capacity of this edge during the non-flood season, and is determined by the maximum water flow passing capacity corresponding to the control water level in the polder area.

[0022] More preferably, in the network flow model, the constraint conditions of the edges include: capacity constraint, flow conservation constraint, and non-negative flow constraint;

[0023] The capacity constraint is: for each edge in the network flow model, its flow cannot exceed the capacity, that is:

[0024] ;

[0025] In the above formula, is the flow of edge , is the capacity of edge , the two endpoints of edge are nodes and node , is the set of edges ;

[0026] The flow conservation constraint is that for each node in the network flow model except the source node and the sink node , the total inflow is equal to the total outflow, that is:

[0027] ;

[0028] The non - negative flow constraint is that for each edge in the network flow model, its flow must be non - negative, that is:

[0029] .

[0030] In the said network flow model, the capacity of edge is approximately replaced by the flow - passing capacity corresponding to the average river width of the river reach , and the calculation formula and the involved hydraulic parameters are as follows:

[0031] ;

[0032] ;

[0033] ;

[0034] ;

[0035] In the above formulas, is the average river width of the river reach; is the difference between the highest control water level and the lowest control water level in the polder; is the cross - sectional area of flow - passing; is the wetted perimeter; is the hydraulic radius; is the side - slope coefficient; is the hydraulic gradient; is the roughness coefficient of the river channel; is the Chezy coefficient.

[0036] More preferably, an auxiliary source node and an auxiliary sink node are also provided in the said network flow model. The auxiliary source node is used as the only water source inlet, and the auxiliary sink node is used as the only water flow outlet; the auxiliary source node is respectively connected to each original source node through an edge with a preset capacity, and the preset capacity of these edges represents the maximum possible flow of water from the auxiliary source node to each original source node; each original sink node is respectively connected to the auxiliary sink node through an edge with a preset capacity , the preset capacities of these edges represent the ability of water to flow from each original sink to the auxiliary sink . In this way, the original multi-source multi-sink network is converted into a network from a single source point to a single sink . This conversion simplifies the network structure and makes it easier to analyze and solve using the maximum flow algorithm.

[0037] More preferably, the network flow model adopts a maximum flow algorithm with the Ford-Fulkerson algorithm as the core. This maximum flow algorithm includes the following steps:

[0038] S1. Initialize the flow of each edge in the network to 0; where the edge is , and the flow of the edge is ;

[0039] S2. According to the current flow , construct the residual network ; the capacity of each edge in this residual network is the difference between the capacity of the corresponding edge in the original network , that is ; for each edge , a reverse edge is also included in the residual network, and its capacity is ;

[0040] S3. Search for a path from the auxiliary source point to the auxiliary sink in the residual network , that is, an augmenting path; use the depth-first search DFS algorithm or the breadth-first search BFS algorithm when searching.

[0041] S4. For the found augmenting path, calculate the minimum residual capacity of all edges on this path, denoted as ; then update the flow along the augmenting path;

[0042] The specific process of updating the flow is as follows: for each forward edge on the augmenting path, increase the flow ; for each reverse edge on the path, decrease the flow ;

[0043] S5. Update the residual network according to the new flow distribution;

[0044] S6. Repeat S3 to S5 until no path from the auxiliary source point to the auxiliary sink can be found in the residual network until the augmented path is found; when no augmented path can be found, the algorithm terminates, and at this time, the flow from the auxiliary source point to the auxiliary sink point is the maximum flow rate.

[0045] By adopting the above preferred scheme, the specific technical features of the first step can be further optimized.

[0046] Preferably, the preset process of the second step is as follows:

[0047] T1. Take the maximum flow rate of each water conservancy project facility as the capacity constraint of its corresponding edge; among them, the maximum flow rate of the pumping station is determined by the flow capacity of its pumps; the gate openings of the sluice pumping stations and sluices are set to preset values according to the actual situation of the target polder area water level; the maximum flow rate of the sluice is determined by the flow capacity of the gate; for the sluice pumping station, the maximum flow rate during drainage is determined by the flow capacity of the pumps, and the maximum flow rate during water diversion is determined by the flow capacity of the gate;

[0048] T2. Assume that the water flow direction changes with the scheduling of the water conservancy project facilities. Take the sluice as the water diversion facility, the pumping station as the drainage facility, and the sluice pumping station as the water diversion facility or drainage facility as needed; according to the principle that the drainage facility should be opened to maintain the water flow balance when the water diversion facility is opened, combine the water diversion facilities and drainage facilities to list a set of water conservancy project facility scheduling schemes, forming an initial scheme set;

[0049] T3. In the initial scheme set, screen the water conservancy project facility scheduling schemes according to the following process:

[0050] i. For the water conservancy project facility scheduling scheme that includes the sluice-pump integrated sluice pumping station, if the scheme takes the sluice-pump integrated sluice pumping station as both the water diversion facility and the drainage facility at the same time, then remove this scheme;

[0051] ii. For each water conservancy project facility scheduling scheme, list all the water diversion paths from the water diversion facility to the drainage facility. If the length of any water diversion path is less than the preset value, then remove this scheme;

[0052] iii. For the water conservancy project facility scheduling scheme with only one water diversion facility and only one drainage facility, that is, a single water diversion and single drainage scheme, if the water diversion flow rate of this scheme is lower than the preset value, then remove this scheme;

[0053] The water conservancy project facility scheduling schemes obtained after screening form the preferred set of water conservancy project facility scheduling schemes.

[0054] By adopting the above preferred scheme, the specific technical features of the second step can be further optimized.

[0055] Preferably, in the third step, the proportion of the dead water section is denoted as , which means: under a certain scheduling plan of water conservancy project facilities, when the maximum flow is reached in the polder network, the proportion of the total length of river sections with a flow rate of 0 to the total length of all river sections; the specific calculation formula is as follows:

[0056] ;

[0057] In this formula, is the total length of river sections with a flow rate of 0; is the length of all river sections;

[0058] The flow rate passing rate of a river section is denoted as , which means: under a certain scheduling plan of water conservancy project facilities, when the maximum flow is reached in the polder network, the weighted average of the flow rate 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 all river sections; the specific calculation formula is as follows:

[0059] ;

[0060] In this formula, is the flow rate of the th river section; is the capacity of the th river section; is the length of the th river section; is the length of all river sections.

[0061] More preferably, when the preset index is the proportion of dead river sections, calculate the proportion of dead river sections for each scheduling plan of water conservancy project facilities, and obtain the scheduling plan of water conservancy project facilities with the lowest proportion of dead river sections by comparison. This represents that this plan performs best in improving the water system connectivity of the polder, helps to improve the overall water environment quality of the polder, and enhances the water self-purification ability; use this plan as the optimal result with the proportion of dead river sections as the index.

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

[0063] More preferably, when the preset index is the river reach flow passing rate, calculate the river reach flow passing rate of each water conservancy project facility scheduling plan, and obtain the water conservancy project facility scheduling plan with the highest river reach flow passing rate through comparison. This represents that this plan performs best in terms of the overall fluidity of the river channels in the polder area, which helps to ensure that the river water in the polder area passes through with a larger flow rate, the water flow velocity increases, the cross-sectional area of the river for flow increases, the water flow velocity in the river increases, the hydraulic retention time is short, the water self-purification ability is greater, the cross-sectional area of the river for flow is larger, the wetted perimeter is larger, and the living space for aquatic organisms is larger; use this plan as the optimal result with the river reach flow passing rate as the index.

[0064] More preferably, when the preset index is the activation of a specific river reach, screen out the plan that realizes the activation of the specific river reach when the maximum flow is reached in the polder area network from each water conservancy project facility scheduling plan; if there are more than two obtained plans, screen out the water conservancy project facility scheduling plan with the lowest proportion of dead river reaches or the highest river reach flow passing rate from these plans; use this plan as the optimal result with the activation of the specific river reach as the index.

[0065] Adopting the above optimal plan can further optimize the specific technical features of the third step.

[0066] Compared with the prior art, starting from the network flow theory and based on the complex water system characteristics of the plain river network polder area, the present invention constructs a general water system connectivity optimization technical plan, which has been verified to be effective and practical, and can obtain the corresponding optimal water conservancy project facility scheduling plans under different preset indexes, which is of great significance for improving the water resource utilization efficiency in the polder area, improving the connectivity of the water system structure in the polder area, realizing the orderly flow of the water body in the polder area, and enhancing the water environment quality in the polder area. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 It is an example diagram of an undirected graph and a directed graph of Embodiment 1 of the present invention.

[0068] Figure 2 It is a schematic diagram of a typical plain river network polder area of Embodiment 1 of the present invention.

[0069] Figure 3 It is an example diagram of converting a multi-source multi-sink network into a single-source single-sink network of Embodiment 1 of the present invention.

[0070] Figure 4 It is a schematic diagram of the general situation of the polder area of Embodiment 2 of the present invention.

[0071] Figure 5 It is a schematic diagram of the generalization of the water system of the polder area of Embodiment 2 of the present invention.

[0072] Figure 6 It is a schematic diagram of the maximum flow passing rate and the proportion of dead river reaches of different scheduling plans of the polder area of Embodiment 2 of the present invention.

[0073] Figure 7 Schematic diagram of the scheduling plan F19 (ensuring water diversion at the Gangbei Sluice and Beizhuangtao Sluice, and water drainage at the Qizhuang Pumping Station and Wujinbang Sluice Station) in Embodiment 2 of the present invention.

[0074] Figure 8 Schematic diagram of the scheduling plan F25 (water diversion at the Wujinbang Sluice Station and Beizhuangtao Sluice, and water drainage at the Qizhuang Pumping Station and Gangbei Sluice Station) in Embodiment 2 of the present invention.

[0075] Figure 9 Schematic diagram of the maximum flow rate and the passing rate of the river section flow rate for different scheduling plans in the polder area in Embodiment 2 of the present invention.

[0076] Figure 10 Schematic diagram of the scheduling plan F10 (water diversion at the Beizhuangtao Sluice, and water drainage at the Qizhuang Pumping Station and Gangbei Sluice Station) in Embodiment 2 of the present invention.

[0077] Figure 11 Schematic diagram of the scheduling plan F12 (water diversion at the Beizhuangtao Sluice, and water drainage at the Gangbei Sluice Station and Wujinbang Sluice Station) in Embodiment 2 of the present invention.

[0078] Figure 12 Schematic diagram of the scheduling plan F13 (water diversion at the Beizhuangtao Sluice; water drainage at the Qizhuang Pumping Station, Gangbei Sluice Station and Wujinbang Sluice Station) in Embodiment 2 of the present invention. Detailed implementation manners

[0079] In specific implementation, the method for optimizing the water environment scheduling plan of the plain river network polder area based on network flow of the present invention includes the following steps:

[0080] First step, generalizing the water system of the target polder area to obtain a network flow model.

[0081] The network flow model includes nodes and edges. The nodes include at least one of the water system intersection points, isolated points, hanging points, source points and sink points. Among them, the isolated points are generalized from independent waters, the hanging points are generalized from small waters connected to only one waterway, the source points are generalized from the polder water inlet, and the sink points are generalized from the water intersection points in the polder or the polder water outlet; the edges represent the paths of water flow, and are generalized from the natural river sections, artificial waterways or water conservancy project facilities in the polder water system. Among them, the artificial waterways include channels and culverts, and the water conservancy project facilities include sluices, pumping stations and sluice stations.

[0082] The network flow model also includes the direction and capacity of edges. The direction of an edge represents the water flow direction and its stability of this edge, including at least one of unidirectional, periodically unidirectional, and bidirectional; among them, if the direction of the edge is unidirectional, it means that the water flow direction of this edge remains constant in the long term; if the direction of the edge is periodically unidirectional, it means that the water flow direction of this edge is determined within the preset research period under the influence of external factors (such as water conservancy project regulation or water system transformation, etc.); if the direction of the edge is bidirectional, it means that the water flow direction of this edge is uncertain due to the gentle terrain, complex water conditions, and human activities. The capacity of an edge represents the flow-through capacity of this edge during the non-flood season and is determined by the maximum flow-through capacity corresponding to the controlled water level in the polder area.

[0083] In this network flow model, the constraint conditions of edges include: capacity constraint, flow conservation constraint, and non-negative flow constraint; among them,

[0084] The capacity constraint is: for each edge in the network flow model, its flow cannot exceed the capacity, that is:

[0085] ;

[0086] In the above formula, is the flow of edge , is the capacity of edge , the two endpoints of edge are node and node , is the set of edges .

[0087] The flow conservation constraint is: except for the source node and the sink node, for each node in the network flow model, the total inflow is equal to the total outflow, that is:

[0088] ;

[0089] The non-negative flow constraint is: for each edge in the network flow model, its flow must be non-negative, that is:

[0090] ;

[0091] In this network flow model, the capacity of edge is approximately replaced by the flow-through capacity corresponding to the average river width of the river section , and the calculation formula and the involved hydraulic parameters are as follows:

[0092] ;

[0093] ;

[0094] ;

[0095] ;

[0096] In the above formulas, is the average river width of the river reach; is the difference between the highest control water level and the lowest control water level inside the polder; is the cross-sectional area of flow; is the wetted perimeter; is the hydraulic radius; is the side slope coefficient; is the hydraulic gradient; is the channel roughness coefficient; is the Chezy coefficient.

[0097] In this network flow model, there are also an auxiliary source node and an auxiliary sink node . The auxiliary source node serves as the only water source inlet, and the auxiliary sink node serves as the only water flow outlet; the auxiliary source node is respectively connected to each original source node through edges with preset capacities, and the preset capacities of these edges represent the maximum possible flow of water from the auxiliary source node to each original source node; each original sink node is respectively connected to the auxiliary sink node through edges with preset capacities, and the preset capacities of these edges represent the ability of water to flow from each original sink node to the auxiliary sink node . In this way, the original multi-source and multi-sink network is converted into a network from a single source node to a single sink node . This conversion simplifies the structure of the network and makes it easier to analyze and solve using the maximum flow algorithm.

[0098] In this network flow model, the flow-saturated paths on the maximum flow path between two nodes are cut edges, representing the bottleneck river reaches of the water bottle. These edges are the key factors restricting the maximum flow; the maximum network flow is equal to the sum of the flows on the cut edges; the minimum cut is a set of cut edges that divides the network into two non-overlapping subsets and minimizes the flow from the auxiliary source node to the auxiliary sink node .

[0099] In this network flow model, a maximum flow algorithm with the Ford-Fulkerson algorithm as the core is adopted. This maximum flow algorithm includes the following steps:

[0100] S1. Initialize the flow of each edge in the network to 0; where the edge is , and the flow of the edge is 。

[0101] S2. Construct a residual network according to the current flow ; The capacity of each edge in the residual network is the difference between the capacity of the corresponding edge in the original network , that is ; For each edge , there is also a reverse edge in the residual network, and its capacity is . 。

[0102] S3. Search for a path from the auxiliary source point to the auxiliary sink point in the residual network , that is, an augmenting path.

[0103] When searching, use the depth-first search DFS algorithm or the breadth-first search BFS algorithm.

[0104] S4. For the found augmenting path, calculate the minimum residual capacity of all edges on this path, denoted as ; Then update the flow along the augmenting path.

[0105] The specific process of updating the flow is as follows: For each forward edge on the augmenting path, increase the flow ; For each reverse edge on the path, decrease the flow .

[0106] S5. Update the residual network according to the new flow distribution.

[0107] S6. Repeat S3 to S5 until no augmenting path from the auxiliary source point to the auxiliary sink point can be found in the residual network; When no augmenting path can be found, the algorithm terminates, and at this time, the flow from the auxiliary source point to the auxiliary sink point is the maximum flow.

[0108] Second, process the water conservancy project facilities in the target polder water system according to a preset process to form an optimal set of water conservancy project facility scheduling plans.

[0109] The preset process is as follows:

[0110] T1. Take the maximum discharge capacity of each water conservancy project facility as the capacity constraint for its corresponding side. Among them, the maximum discharge capacity of a pumping station is determined by the flow capacity of its pumps; the gate openings of a sluice pumping station and a sluice are set to preset values according to the actual situation of the target polder area water level; the maximum discharge capacity of a sluice is determined by the flow capacity of the gate; for a sluice pumping station, the maximum discharge capacity during drainage is determined by the flow capacity of the pumps, and the maximum discharge capacity during water diversion is determined by the flow capacity of the gate.

[0111] T2. Assume that the water flow direction changes with the scheduling of water conservancy project facilities. Consider the sluice as a water diversion facility, the pumping station as a drainage facility, and the sluice pumping station as a water diversion facility or a drainage facility as needed. According to the principle that a drainage facility should be opened when a water diversion facility is opened to maintain water flow balance, combine the water diversion facilities and drainage facilities to list a set of water conservancy project facility scheduling plans, forming an initial plan set.

[0112] T3. In the initial plan set, screen the water conservancy project facility scheduling plans according to the following process:

[0113] i. For a water conservancy project facility scheduling plan that includes a sluice-pump integrated sluice pumping station, if the plan uses the sluice-pump integrated sluice pumping station as both a water diversion facility and a drainage facility at the same time, then remove this plan.

[0114] ii. For each water conservancy project facility scheduling plan, list all the 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, then remove this plan.

[0115] iii. For a water conservancy project facility scheduling plan with only one water diversion facility and only one drainage facility, that is, a single water diversion and single drainage plan, if the water diversion flow rate of this plan is lower than the preset value, then remove this plan.

[0116] The water conservancy project facility scheduling plans obtained after screening form an optimized set of water conservancy project facility scheduling plans.

[0117] Step 3. According to the optimized set of water conservancy project facility scheduling plans, screen according to a preset index. The preset index is the proportion of dead river sections, the flow rate passing rate of river sections, or the flowing water in a specific river section; finally, obtain the corresponding optimized water conservancy project facility scheduling plans under different preset indexes.

[0118] In Step 3, the proportion of dead river sections is denoted as , and its meaning is: under a certain water conservancy project facility scheduling plan, when the polder area network reaches the maximum flow, the proportion of the total length of river sections with a flow rate of 0 in the total length of all river sections; the specific calculation formula is as follows:

[0119] ;

[0120] In this formula, is the total length of the river reaches with a flow rate of 0; is the length of the total river reaches.

[0121] The flow rate passing rate of the river reaches is denoted as , which means: under a certain water conservancy project facility scheduling scheme, when the polder area network reaches the maximum flow, the weighted average of the ratio of the flow rate to the capacity of each river reach, and its weight is calculated according to the proportion of the length of each river reach in the total length of the river reaches; the specific calculation formula is as follows:

[0122] ;

[0123] In this formula, is the flow rate of the th river reach; is the capacity of the th river reach; is the length of the th river reach; is the length of the total river reaches.

[0124] When the preset index is the proportion of dead river reaches, calculate the proportion of dead river reaches of each water conservancy project facility scheduling scheme, and obtain the water conservancy project facility scheduling scheme with the lowest proportion of dead river reaches by comparison. This represents that this scheme performs best in improving the water system connectivity of the polder area, helps to improve the overall water environment quality of the polder area, and enhances the water self-purification ability; take this scheme as the optimal result with the proportion of dead river reaches as the index.

[0125] Specific practices show that not all schemes that maximize the water flow can effectively improve the hydrodynamic conditions in the polder area. Although some schemes can achieve a large flow rate, the distribution of this flow rate may not be beneficial to the hydrodynamic activity of the entire polder area. The water flow may only be concentrated in a few channels rather than widely distributed throughout the polder area. Therefore, when the scheduling goal is to minimize the dead water range in the polder area, the preset index should be set as the proportion of dead river reaches, so as to screen out the scheme that performs best in improving the water system connectivity.

[0126] When the preset index is the flow rate passing rate of the river reaches, calculate the flow rate passing rate of the river reaches of each water conservancy project facility scheduling scheme, and obtain the water conservancy project facility scheduling scheme with the highest flow rate passing rate of the river reaches by comparison. This represents that this scheme performs best in the overall fluidity of the polder area river channels. The water flow velocity in the river channels increases, the hydraulic residence time is short, the water self-purification ability is greater, the cross-sectional area of the river channel for water flow is larger, the wetted perimeter is larger, and the living space for aquatic organisms is larger; take this scheme as the optimal result with the flow rate passing rate of the river reaches as the index.

[0127] When the preset index is the activation of a specific river section, select from the scheduling plans of each water conservancy project facility the plan that enables the activation of the specific river section when the maximum flow is reached in the polder network; if there are more than two such plans, then select from these plans the scheduling plan of the water conservancy project facility with the lowest proportion of dead river sections or the highest river section flow passing rate; use this plan as the optimal result with the activation of the specific river section as the index.

[0128] The present invention will be further described in detail below with reference to the accompanying drawings and in conjunction with embodiments. However, the present invention is not limited to the given examples.

[0129] Embodiment 1

[0130] This embodiment is for the construction of the polder network flow model.

[0131] The specific content of this embodiment is as follows:

[0132] (I) Definition of graph and its concepts

[0133] (1) Definition of graph

[0134] Let be a non-empty set composed of a finite number of vertices, where is the edge set, which is a set of unordered pairs of some elements in , and the binary tuple composed of the vertex set and the edge set is called a graph (graph), denoted as . Among them, is the set of nodes in the network; is the set of edges in the network. The one formed in the previous definition is called an undirected graph. If the edge has a direction, it is called a directed graph, denoted as . Examples of undirected graphs and directed graphs are as Figure 1 shown.

[0135] In addition, the number of edges with node as the end point is called the degree of the node, denoted as . A point with a degree of zero is called an isolated point, a point with a degree of 1 is called a pendant point, the edge of the pendant point is called a pendant edge, a point with an odd degree is called a singular point, and a point with an even degree is called an even point. For a directed graph, they are called the out-degree and in-degree of the node. The out-degree of node is the number of directed edges with as the starting node (i.e., the directed edge starting from vertex ), denoted as ; the in-degree of node is the number of directed edges with as the end point (i.e., the directed edge entering node ), denoted as .

[0136] (2)Weighted graph

[0137] For a directed graph , if for each in the graph a weight is assigned, the directed graph after assignment is a weighted graph, which can be denoted as .

[0138] (II)Basic concepts of network flow model

[0139] (1)Capacity network

[0140] Given a weighted graph , where is the set of nodes, is the set of edges, is the capacity function of the edges, and the graph satisfies the following conditions:

[0141] 1) In the set of nodes , there are two special subsets of nodes, the source node set and the sink node set . All nodes in the source node set have an in-degree of 0, while all nodes in the sink node set have an out-degree of 0;

[0142] 2) Each edge in is assigned a non-negative real value as the capacity of the edge, representing the maximum flow that the edge

[0143] (2)Feasible flow

[0144] In , each edge has a flow , and the set of these flows is called a flow on the network. If the flow satisfies the following conditions, it is called a feasible flow:

[0145] 1) Capacity constraint: For each edge in , , where is the capacity of the edge ;

[0146] 2) Flow conservation: For any non-source and non-sink node in , the total flow into is equal to the total flow out of The total flow. For the source and the sink , the total flow out of the source is equal to the total flow into the sink.

[0147] (3) Cut

[0148] If there exists an edge set that is a subset of such that can be split into two subgraphs , whose node sets are and , satisfying , , and the source belongs to , the sink belongs to , and the following conditions are satisfied:

[0149] 1) is non - connected;

[0150] 2) There exists a that is a proper subset of such that

[0151] Then is called the cut set of , denoted as . The sum of the capacities of all the edges in the cut set whose starting points are in and ending points are in is called the cut set capacity of , denoted as . In the capacity network , there may be multiple cut sets, and the cut set with the minimum cut set capacity is called the minimum cut of the network

[0152] From the definition of the cut set, it can be seen that in the capacity network, the cut set represents the only path from the source to the sink . If any cut set is removed, the source and the sink will no longer be connected. Therefore, the flow of any feasible flow will not exceed the capacity of any cut set.

[0153] (4) Augmenting path

[0154] An augmenting path is a path from the source node to the sink node along which the network flow can be increased. This means that if there is a path from the source node to the sink node such that each edge on the path can carry additional flow, i.e., it has not reached its capacity limit, then this path can be considered an augmenting path. The process of increasing the flow along the augmenting path increases the total flow from the source node to the sink node until one of the edges reaches its capacity limit and no more flow can be added.

[0155] (5) Residual network

[0156] The residual network is a concept related to the original network flow graph and is used to consider the flow that has already passed through the network when finding augmenting paths. The residual network consists of all the nodes and edges in the original network, but the capacity of the edges is adjusted according to the flow in the original network.

[0157] 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 pass through this edge without exceeding the capacity limit.

[0158] In addition, the residual network also introduces reverse edges. For each edge in the original network , there will be a reverse edge in the residual network from to , and its capacity is . This represents that the flow that has already passed can be partially or fully revoked so that this part of the flow can be redistributed to other paths in the network.

[0159] (III) Construction of the network flow model in the polder area

[0160] The polder area is an important way of developing and utilizing the plain river network area. In the polder area, by building dikes and dams along rivers and lakes, digging ditches inside, and constructing water conservancy facilities such as pumping stations and sluice gates at the boundaries, 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 the external water flow during floods to prevent flood intrusion, and at the same time draw water inward through sluice pumps during the dry season to ensure water use inside the polder. A typical plain river network polder area, such as Figure 2As shown, it presents the basic structure and layout of the water conservancy project in the polder area. Among them, the dike is the most important protective facility in the polder area. It can not only block the external flood but also prevent the internal water from flowing out. The ditches are used for the water flow regulation within the polder area to ensure the needs of irrigation and drainage. The pumping stations and sluice gates are the key facilities for controlling the water volume in and out. They jointly maintain the balance of the 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 prevention ability and land use efficiency of a specific area but also plays an important role in maintaining the ecological balance, protecting biodiversity, and promoting the economic and social development of the region.

[0161] In the water system network of the plain river network polder area, it mainly includes the intersections of river branches, small water areas (such as lakes, ponds, etc.), and water conservancy project facilities (such as sluice gates, 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 the edges. Nodes are classified into water system intersection points, isolated points (independent water areas), hanging points (small water areas connected to only one watercourse), source points (the water inlet of the polder area), and sink points (intersection points, the water outlet of the polder area) according to their functional and location characteristics. The natural river sections and artificial watercourses (such as channels, culverts, etc.) in the water system are abstracted as edges, representing the paths of water flow. For the convenience of model construction and solution, water conservancy project facilities such as sluice gates and pumps can be generalized as edges in the model. According to the stability and directionality of water flow, these edges can be one-way (for watercourses with a long-term constant flow direction), periodically one-way (affected by factors such as water conservancy project regulation or water system transformation, the watercourse with a determined flow direction within the preset research period), or two-way (in areas with gentle terrain, complex water conditions, and large human activity influence, the flow direction of some river channels is uncertain). During the non-flood season, the flow capacity (capacity) of each edge is determined by the maximum flow capacity corresponding to the polder area control water level.

[0162] Taking the maximum flow capacity of the river corresponding to the polder area control water level as the capacity constraint of the edge, when evaluating the maximum flow of the polder area water system network under different sluice gate and pump dispatching, the optimal dispatching scheme of the polder area is obtained through the optimal selection index. The specific constraint conditions of the edge are as follows:

[0163] (1) Capacity constraint:

[0164] For each edge in the network , the flow shall not exceed the capacity of the edge .

[0165] ;

[0166] (2) Flow conservation constraint:

[0167] Except for the source point and the sink point , the total inflow of each node in the network is equal to the total outflow.

[0168]

[0169] (3) Non - negative flow constraint:

[0170] The flow on each edge in the network must be non - negative.

[0171]

[0172] Capacity of the edge The flow - passing capacity corresponding to the average river width of the available river reach Approximately replace, and the related hydraulic parameters are as follows:

[0173] ;

[0174] ;

[0175] ;

[0176] ;

[0177] In the formula, is the average river width of the river reach; is the difference between the highest control water level and the lowest control water level in the polder; is the cross - sectional area of the water flow; is the wetted perimeter; is the hydraulic radius; is the side - slope coefficient; is the hydraulic gradient; is the roughness coefficient of the river channel; is the Chezy coefficient.

[0178] To facilitate the solution of the network flow model, further construction and mathematical processing are carried out on the water system network. In the original water system network, two special vertices are added, namely the source vertex and the sink vertex . The source vertex serves as the only water source entrance of the entire network, while the sink vertex serves as the only water outlet in the network. Connect the source vertex to each source vertex of the original network through an edge with a preset capacity. The preset capacity of these edges represents the maximum possible flow of water from the network source vertex to each source vertex. Similarly, connect each sink vertex to the sink vertex through an edge with a preset capacity. The preset capacity of these edges represents the ability of water to flow from the inside of the network to the final sink vertex . Through the above steps, the original multi - source and multi - sink network is converted into a single - source vertex to a single - sink vertex The network, this conversion 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 shown as Figure 3 shown. Among them, Figure a is a multi-source multi-sink network, the source nodes are A and D, and the sink nodes are C and F. To facilitate the maximum flow calculation, an auxiliary source node and sink node are added, and it is converted into Figure b. The number on the left in the parentheses on the edge in the figure represents the flow of the edge, and the number on the right represents the capacity of the edge.

[0179] The flow-saturated path on the maximum flow path between two nodes is called a cut edge, and it can also be called a bottleneck reach of a water bottle. These edges are the key to restricting the maximum flow. As Figure 3 shown in Figure b of

[0180] (IV) Ford-Fulkerson Algorithm

[0181] The maximum flow of a network aims to find the maximum flow that can pass from a given source node to a given sink node in a directed network, that is, the flow from to reaches the maximum feasible flow. The present invention uses the Ford-Fulkerson algorithm for maximum flow calculation. Its core idea is to continuously find an augmenting path and augment it until no augmenting path can be found. At this time, the flow is the maximum flow. The specific steps are as follows:

[0182] (1) Initialize the flow

[0183] Initialize the flow of each edge in the network to 0. This means that initially, no flow passes through the network.

[0184] (2) Construct the residual network

[0185] According to the current flow , construct the residual network . The capacity of each edge in the residual network is the difference between the capacity of the corresponding edge in the original network , that is . For each edge , there is also a reverse edge in the residual network, and its capacity is 。

[0186] (3)Find an augmenting path

[0187] In the residual network find a path from the source node to the sink node . Such a path is called an augmenting path because it can be used to increase the total flow from to . Depth-First Search (DFS) or Breadth-First Search (BFS) can be used to find such a path

[0188] (4)Augment the flow

[0189] For the found augmenting path, calculate the minimum residual capacity of all edges on the path, denoted as . Then, update the flow along the augmenting path: for each forward edge on the path, increase the flow by . For each backward edge on the path, decrease the flow by

[0190] (5)Update the residual network

[0191] According to the new flow distribution, update the residual network . This may result in some new augmenting paths emerging, or some of the original augmenting paths becoming unavailable

[0192] (6)Output the maximum flow

[0193] Repeat the process of finding an augmenting path, augmenting the flow, and updating the residual network until no augmenting path from to can be found in the residual network. When no augmenting path can be found, the algorithm terminates, and the flow from the source node to the sink node is the maximum flow

[0194] (V)Analysis and visualization tools

[0195] ​The visualization of complex networks of river networks involves a large number of nodes and edges, as well as the complex relationships between these elements. To effectively represent this complexity and perform visualization, some existing tools and software can be utilized, such as Gephi, Cytoscape, NetworkX, igraph, etc. These tools not only support the basic visualization of networks but also provide advanced functions, such as layout optimization, interactivity, and in-depth analysis of network structures. In this embodiment, igraph and ggraph packages based on the R language are selected to analyze and visualize the complex network of river networks. igraph is one of the most popular network analysis and visualization packages in the R language, providing rich functions, including the creation, modification, visualization of networks, and complex analysis of network structures and dynamics. ggraph, on the other hand, is based on the syntax of ggplot2 and provides a flexible and expressive way to create network diagrams, inheriting the ease of use, high customizability, and aesthetic graphic design of ggplot2.

[0196] Embodiment 2

[0197] This embodiment is an example of applying the technical solution of the present invention to an actual scenario.

[0198] The water quality of rivers and lakes and the health of the ecosystem within the polder are directly related to agricultural production, residents' lives, and the protection of biodiversity. The sluice and pump scheduling is an important means to regulate the water volume exchange inside and outside the polder and the water quality within the polder, and the live water scheduling is an important means to improve water body mobility and water ecological environment. Different scheduling schemes will affect the water flow path and distribution method, thus affecting the utilization efficiency of water resources. By precisely controlling the operation of sluices and pumps, the internal water flow circulation in the polder can be promoted and the water quality can be improved.

[0199] (1) This embodiment takes a certain polder in a typical polder area of a certain town as an example.

[0200] This polder area has problems such as low terrain, unreasonable water system layout, dense hydraulic structures, and a single scheduling scheme, resulting in poor water body mobility, deteriorated water ecological environment, and insufficient flood control and drainage capabilities. These problems not only affect the normal functions of the polder area but also pose threats to the quality of life of local residents and the sustainable development of the region. By optimizing the river network layout, improving the drainage capacity, improving the scheduling scheme, and strengthening the governance of the water ecological environment, the water environment and water ecological conditions in the polder area can be effectively improved, and the sustainable development of the polder area can be achieved.

[0201] The focus of this embodiment is: for the example polder area, construct a polder area network flow model, optimize the sluice and pump scheduling scheme, and improve the functional connectivity of the polder area water system.

[0202] (2) General situation of this polder and generalization of the water system

[0203] 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.

[0204] Table 1. Basic information of the Lianwei sluice pump

[0205]

[0206] 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.

[0207] Table 2. Generalized basic information of the Lianwei water system

[0208]

[0209] (III) Multi-sluice pump joint dispatching scheme set

[0210] 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.

[0211] Table 3: Overview of the Lianwei sluice pump

[0212]

[0213] Assume that the water flow direction changes with the sluice-pump operation scheduling, and an optimized sluice-pump operation scheduling plan set for the polder area is formulated. Each opened water intake gate requires at least one corresponding drainage pump station to be opened to maintain the water flow balance. List all possible water intake and drainage combinations. After calculation, there are 105 sluice-pump operation scheduling plans in total. Considering factors such as ensuring the integration of the sluice and pump at the Gangbei Sluice Station and Wujinbang Sluice Station, where it is impossible to draw water while discharging, and the fact that the water intake path from the Gangdong Sluice to the Gangbei Pumping Station is too short and the effect of single water intake and single drainage is not good, finally 28 sluice-pump operation scheduling plans are selected, as shown in Table 4 below.

[0214] Table 4. Sluice-pump operation scheduling plan for this polder

[0215]

[0216] (4) Optimization of the scheduling plan

[0217] 1. Proportion of dead water sections

[0218] The proportion of dead water sections ( ) is defined as the proportion of the total length of the river sections with a flow rate of 0 to the total length of the river sections when the polder area network reaches the maximum flow under different scheduling plans. The specific calculation formula is as follows:

[0219] ;

[0220] In the formula is the total length of the river sections with a flow rate of 0 (unit: m); is the total length of the river sections (unit: m).

[0221] This index reflects the effect of the scheduling plan in improving the water system connectivity. The lower the proportion of dead water sections, the more river sections the plan can keep flowing. By comparing the proportion of dead water sections of different plans, the best-performing plan in improving the water system connectivity can be selected, which helps to improve the overall water environment quality of the polder area and enhance the water self-purification ability.

[0222] The calculation results of the maximum water passing capacity and the proportion of dead water sections in the polder area under different scheduling plans are as Figure 6 shown. In the figure, the blue bar chart is the maximum water passing capacity of the polder area, and the red broken line is the proportion of dead water sections in the polder area under different plans. Generally speaking, the maximum water passing capacity of the polder area does not correspond to the maximum proportion of dead water sections in the polder area, which indicates that not all plans that maximize the water flow can effectively improve the hydrodynamic conditions in the polder area. Although some sluice-pump operation scheduling plans can achieve a large water passing capacity, this distribution of water flow may not be conducive to the hydrodynamic activity of the entire polder area. The water flow may only be concentrated in a few river channels rather than widely distributed throughout the polder area.

[0223] Among them, the maximum water passing capacity of Plan F19 is the largest, reaching 6.81m 3 / s, the proportion of dead river sections is 49.45%, indicating that by ensuring the water diversion through Gangbei Sluice and Beizhuangtao Sluice and discharging it through Qizhuang Pumping Station and Wujinbang Sluice Station, it will cause the Songjiagang, Zhongwanggang, and Xiongji Port in the middle of the polder area to be unable to have flowing water. See specifically Figure 7 . In Scheme F25, the proportion of dead river sections in the polder area is 20.43%, and the maximum discharge is 6.05 m 3 / s. By diverting water through Wujinbang Sluice Station and Beizhuangtao Sluice and discharging it through Qizhuang Pumping Station and Gangbei Sluice Station, the maximum flow value of this scheme is less than those of Schemes F16, F19, and F22. However, under this scheme, the Songjiagang and Zhongwanggang in the middle of the polder area have achieved flowing water, and the proportion of dead river sections in the polder area is the lowest. See specifically Figure 8 . Generally speaking, Scheme F25 can achieve a larger flowing water range while ensuring a relatively high discharge, effectively improving the hydrodynamic conditions and ecological environment quality in the polder area. Therefore, when the minimum dead water range in the polder area is taken as the scheduling goal, Scheme F25 can be considered as the current optimal sluice-pump scheduling scheme for this connected polder area.

[0224] 2. River section flow passing rate

[0225] The river section flow passing rate ( ), is defined as the weighted average of the ratio of the flow to the capacity of each river section when the polder area network reaches the maximum flow under different scheduling schemes, where the weight is calculated according to the proportion of the length of each river section to the total length of the river sections. The specific calculation formula is as follows:

[0226] ;

[0227] In the formula is the flow of the th river section (unit: m 3 / s); is the capacity of the th river section (unit: m 3 / s); is the length of the th river section (unit: m); is the total length of the river sections (unit: m).

[0228] This index reflects the overall utilization efficiency of the river channel capacity under different scheduling schemes. The higher the ratio, the larger the actual flow velocity of the river channel, the larger the cross-sectional area of the river channel, the larger the wetted perimeter, the shorter the hydraulic residence time, and the higher the self-purification ability of the water body under a certain water head difference inside and outside the polder. By analyzing the changes in the river section flow passing rate under different schemes, the optimal water conservancy facility scheduling scheme can be identified.

[0229] After calculation, the maximum discharge and river section flow passing rate of different scheduling schemes in the polder area are as shown in Figure 9As shown, the utilization rate of the river section of the scheduling plan F25 is the highest, which is 47.60%. Therefore, considering the passing rate of the river section flow, Plan 25 can be considered as the optimal sluice-pump scheduling plan.

[0230] 3. Live water in a specific river section

[0231] In the above preferred plans, no live water is achieved in the Xiongji Port. It shows that only considering the proportion of dead water sections in the polder area and the passing rate of the river section flow cannot fully achieve the overall live water in the polder area. It is found in the simulation process that Plans F10, F12, and F13 can achieve live water in the Xiongji Port. For details, see Figure 10 、 Figure 11 、 Figure 12 As shown. Plan F10 mainly diverts water through the Beizhuang Sluice, discharges it through the Qizhuang Pumping Station and the Beibaozhanggang Pumping Station. The maximum flow value is 4.32 m 3 / s. The proportion of dead water sections in the polder area is 58.91%, and the passing rate of the river section flow is 30.07%. Plan F12 diverts water through the Zhuangtao Sluice, discharges it through the Beibaozhanggang Pumping Station and the Wujinbang Sluice Station. The maximum flow value is 4.32 m 3 / s. The proportion of dead water sections in the polder area is 61.47%, and the passing rate of the river section flow is 25.69%. Plan F13 discharges through the Beizhuang Sluice, Qizhuang Pumping Station, Beibaozhanggang Pumping Station, and Wujinbang. The maximum flow value is 4.32 m 3 / s. The proportion of dead water sections in the polder area is 61.47%, and the passing rate of the river section flow is 25.69%. The overall scheduling ideas and routes of the three plans are relatively close, and all can achieve live water in the Xiongji Port. Comparing the live water range and river utilization rate in the polder area, Plan F10 is selected as the live water plan for the Xiongji Port.

[0232] Based on the above embodiments, starting from the network flow theory and based on the complex water system characteristics of the plain river network polder area, the present invention constructs a general water system connectivity optimization technical solution, which has been verified to be effective and practical, and can obtain the optimal scheduling plans of water conservancy engineering facilities corresponding to different preset indicators, which is of great significance for improving the water resource utilization efficiency in the polder area, improving the connectivity of the water system structure in the polder area, realizing the orderly flow of water bodies in the polder area, and enhancing the water environment quality in the polder area.

[0233] In addition to the above embodiments, the present invention may have other implementation manners. Any technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope required by the present invention.

Claims

1. An optimal selection method for the water environment scheduling scheme in the plain river network polder area based on network flow, characterized in that, It includes the following steps: First step: Generalize the water system of the target polder area to obtain a network flow model; In the said network flow model, the constraint conditions of the edges include: capacity constraint, flow conservation constraint, and non - negative flow constraint; The capacity constraint is: For each edge in the network flow model, its flow cannot exceed the capacity, that is: ； In the above formula, is the flow of edge , is the capacity of edge . The two endpoints of edge are node and node . is the set of edges . The flow conservation constraint is that for each node in the network flow model, except for the source node and the sink node , 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 a non - negative value, that is: ； In the network flow model, the edge capacity is approximately replaced by the flow capacity corresponding to the average river width of the river reach. The calculation formula and the involved hydraulic parameters are as follows: ​ ； ； ； ； In the above formulas, is the average river width of the river reach; is the difference between the highest control water level and the lowest control water level in the polder; is the cross-sectional area of flow; is the wetted perimeter; is the hydraulic radius; is the side slope coefficient; is the hydraulic gradient; is the roughness coefficient of the river channel; is the Chezy coefficient; The said network flow model adopts a maximum - flow algorithm with the Ford - Fulkerson algorithm as the core; Second step: Process the water conservancy project facilities in the target polder area according to a preset process and form an optimal set of water conservancy project facility scheduling plans; Among them, the preset process is: T1: Take the maximum passing flow of each water conservancy project facility as the capacity constraint of its corresponding edge; among them, the maximum passing flow of the pumping station is determined by the passing - flow capacity of its pump units; the gate opening of the sluice - pumping station and the sluice is set to a preset value according to the actual situation of the water level in the target polder area; the maximum passing flow of the sluice is determined by the passing - flow capacity of the gate; for the sluice - pumping station, when draining water, the maximum passing flow of the sluice - pumping station is determined by the passing - flow capacity of the pump units, and when diverting water, the maximum passing flow of the sluice - pumping station is determined by the passing - flow capacity of the gate; T2: Assume that the water flow direction changes with the change of the water conservancy project facility scheduling. Take the sluice as a water - diversion facility, the pumping station as a drainage facility, and the sluice - pumping station as a water - diversion facility or a drainage facility as needed; according to the principle that when opening the water - diversion facility, a drainage facility should be equipped to maintain water flow balance, combine the water - diversion facilities and the drainage facilities, and thus list a set of water conservancy project facility scheduling plans to form an initial plan set; T3: In the initial plan set, screen the water conservancy project facility scheduling plans according to the following process: i. For the water conservancy project facility scheduling plan containing the sluice - pump integrated sluice - pumping station, if the plan takes the sluice - pump integrated sluice - pumping station as both a water - diversion facility and a drainage facility at the same time, then remove this plan; ii. For each water conservancy project facility scheduling plan, list all the water - diversion paths from the water - diversion facility to the drainage facility. If the length of any water - diversion path is less than the preset value, then remove this plan; iii. For the water conservancy project facility scheduling plan with only one water - diversion facility and only one drainage facility, that is, a single - diversion and single - drainage plan, if the water - diversion flow of this plan is lower than the preset value, then remove this plan; The water conservancy project facility scheduling plans obtained after screening form an optimal set of water conservancy project facility scheduling plans; Third step: According to the optimal set of water conservancy project facility scheduling plans, screen according to a preset index. The preset index is the proportion of dead - water sections, the passing rate of river - section flow, or the flowing water in a specific river - section; finally, obtain the corresponding optimal water conservancy project facility scheduling plans under each preset index; Among them, the proportion of the dead river section is denoted as , which means: under a certain scheduling plan of water conservancy project facilities, when the weir area network reaches the maximum flow, the proportion of the total length of the river section with a flow rate of 0 in the total length of the river section; the specific calculation formula is as follows: ； In this formula, is the total length of the river section with a flow rate of 0; is the length of the total river section; The flow passing rate of the river section is denoted as , which means: under a certain scheduling plan of water conservancy project facilities, when the polder area network reaches the maximum flow, the weighted average of the ratio of the flow to the capacity of each river section, and its weight is calculated according to the proportion of the length of each river section in the total length of the river section; the specific calculation formula is as follows: ； In this formula, is the flow of the th river section; is the capacity of the th river section; is the length of the th river section; is the length of the total river section; When the preset index is the proportion of dead - water sections, calculate the proportion of dead - water sections of each water conservancy project facility scheduling plan, and obtain the water conservancy project facility scheduling plan with the lowest proportion of dead - water sections by comparison; take this plan as the optimal result with the proportion of dead - water sections as the index; When the preset index is the passing rate of river section flow, calculate the passing rate of river section flow for each water conservancy project facility dispatching plan, and obtain the water conservancy project facility dispatching plan with the highest passing rate of river section flow by comparison; use this plan as the optimal result with the passing rate of river section flow as the index; When the preset index is the activation of a specific river section, select the plan that activates the specific river section when the maximum flow is reached in the polder network from each water conservancy project facility dispatching plan; if there are more than two obtained plans, select the water conservancy project facility dispatching plan with the lowest proportion of dead river sections or the highest passing rate of river section flow from these plans; use this plan as the optimal result with the activation of a specific river section as the index.

2. The preferred method for the water environment scheduling plan of the plain river network polder area based on network flow according to claim 1, characterized in that The network flow model includes nodes, edges, the direction of edges, and the capacity of edges; Nodes include at least one of the water system intersection point, isolated point, hanging point, source point, and sink point. Among them, 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 intake of the polder, and the sink point is generalized from the water intersection point in the polder or the outlet of the polder; Edges represent the path of water flow and are generalized from natural river sections, artificial waterways, or water conservancy project facilities in the polder water system. Among them, artificial waterways include channels and culverts, and water conservancy project facilities include sluices, pumping stations, and sluice stations; The direction of an edge represents the water flow directionality and its stability of this edge, including at least one of unidirectional, periodically unidirectional, and bidirectional; where the direction of the edge is unidirectional, it means that the water flow direction of this edge remains constant for a long time; the direction of the edge is periodically unidirectional, it means that the water flow direction of this edge is determined within the preset research period under the influence of external factors; the direction of the edge is bidirectional, it means that the water flow direction of this edge is uncertain due to gentle terrain, complex water conditions, and human activities; The capacity of an edge represents the flow - passing capacity of this edge during the non - flood season and is determined by the maximum flow - passing capacity corresponding to the control water level of the polder.

3. The method for optimizing the water environment scheduling plan in the plain river network polder area based on network flow according to claim 1, characterized in that The network flow model further includes an auxiliary source node and an auxiliary sink node . The auxiliary source node serves as the only water source inlet, and the auxiliary sink node serves as the only water outlet; connect the auxiliary source node to each original source node through edges with a preset capacity, and the preset capacity of these edges represents the maximum possible water flow from the auxiliary source node to each original source node; connect each original sink node to the auxiliary sink node through edges with a preset capacity, and the preset capacity of these edges represents the ability of water to flow from each original sink node to the auxiliary sink node .

4. The method for optimizing the water environment scheduling plan in the plain river network polder area based on network flow according to claim 1, characterized in that, The maximum - flow algorithm includes the following steps: S1. Initialize the traffic of each edge in the network to 0; where the edge is , and the traffic of edge is ; S2. According to the current traffic , construct the residual network ; The capacity of each edge in the residual network is the difference between the capacity of the corresponding edge in the original network , that is ; For each edge , there is also a reverse edge in the residual network, and its capacity is ; S3. In the remaining network find a path from the auxiliary source point to the auxiliary sink point , i.e., the augmenting path; when finding, use the depth-first search DFS algorithm or the breadth-first search BFS algorithm; S4. For the found augmenting path, calculate the minimum residual capacity of all edges on this path, denoted as ; then update the flow along the augmenting path; The specific process of updating the flow is as follows: For each forward edge on the augmenting path , increase the flow ; For each backward edge on the path , decrease the flow ; S5. Update the remaining network according to the new traffic distribution ; S6. Repeat S3 to S5 until no augmenting path from the auxiliary source node to the auxiliary sink node can be found in the remaining network; when no augmenting path can be found, the algorithm terminates, and the flow from the auxiliary source node to the auxiliary sink node is the maximum flow at this time.

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