Construction position and scheduling scheme optimization method for salt tide upstream resisting effect

Abstract

The invention relates to the technical field of water conservancy project planning and operation management, and discloses a construction position and scheduling scheme optimization method for a salt tide upstream resisting effect, and the method comprises the steps: obtaining basic water power and geological data of a river mouth of a drainage basin, and removing an unstable region to determine a feasible construction range of a tide gate; establishing an estuary two-dimensional numerical simulation model, and calibrating by using measured data to obtain an effective model; setting a plurality of candidate positions in the model, simulating a salt tide upstream process, and determining an optimal construction position by comparing salinity indexes; arranging a gate at the optimal position, simulating various scheduling working conditions, and determining an optimal scheduling scheme. According to the method, space site selection and time scheduling optimization are coupled, the salt resistance efficiency of different sections and mean value threshold scheduling modes is quantitatively evaluated through numerical simulation, a salt water channel is accurately cut off in the flood tide high-water-level period, the average salinity of an estuary area and the salinity of key measuring points are reduced, and the safety of estuary fresh water resources is effectively guaranteed.

Description

Technical Field

[0002] This invention relates to the field of water conservancy project planning and operation management technology, specifically to a method for optimizing construction location and scheduling schemes to resist the effects of saltwater intrusion. Background Technology

[0004] As the confluence of rivers and the ocean, estuaries are frequently affected by both runoff and tidal currents, leading to frequent saltwater intrusion. The intrusion of high-salinity water threatens the freshwater supply of coastal cities and the safety of estuarine ecosystems. Constructing tidal gates is a common engineering measure to block saltwater intrusion and protect freshwater resources in inland rivers.

[0005] In the planning and design of existing tide gate projects, the selection of construction sites and the formulation of operation and scheduling plans are often relatively separate. Typically, site selection focuses primarily on engineering economic indicators such as river topography, construction conditions, and land acquisition and resettlement, while rarely delving into the quantitative differences in the physical barriers to salinity transport and diffusion at different cross-sections under complex hydrodynamic environments. This site selection approach, prioritizing ease of implementation while neglecting hydrodynamic salt-blocking effectiveness, results in gates that, although possessing physical barrier functions, fail to maximize the reduction of saline tide kinetic energy using river topography. Furthermore, relying solely on hydraulic indicators for site selection can sometimes overlook the complex geological risks of estuaries. Constructing hydraulic structures in areas with active faults or severely eroded and deposited soft soil foundations can lead to long-term safety hazards.

[0006] Furthermore, in terms of the operation and management of tide gates, existing scheduling strategies largely rely on manual experience or simple fixed water level control. Conventional scheduling often employs fixed gate opening and closing times or single water level thresholds, lacking a dynamic optimization mechanism based on refined numerical simulation. This extensive scheduling method struggles to accurately capture the critical periods of maximum saline intrusion flux, failing to effectively cut off saline replenishment during high tide and fully utilize runoff to suppress salinity during low tide. Consequently, the salinity reduction effect in the estuary area is poor during strong saline intrusions, making it difficult to ensure the water supply security of key intakes around the clock. Therefore, an optimization method is needed that can systematically couple geological safety constraints, spatial site selection optimization, and time-based scheduling strategies. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides an optimization method for construction location and scheduling scheme to resist the upstream effects of saltwater intrusion. This method solves the problems of unsatisfactory salinity control in estuary areas and difficulty in achieving stable water quality standards at key water intakes caused by improper site selection or extensive scheduling strategies in existing tide gate projects when dealing with strong saltwater intrusion.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a method for optimizing the construction location and scheduling scheme to resist the upstream intrusion of saltwater, the method specifically including the following steps:

[0010] First, basic hydrodynamic parameters of the estuary in the upstream area of ​​the saltwater intrusion were obtained, along with geological survey data of the estuary. Based on the geological survey data, the feasible construction area for the tide barrier was determined. Second, a two-dimensional numerical simulation model of the estuary was established. The model parameters were set using the basic hydrodynamic parameters, and the model was calibrated by comparing it with measured salinity data until the simulation error met the preset requirements, thus obtaining an effective two-dimensional numerical simulation model of the estuary.

[0011] Subsequently, using this effective two-dimensional numerical simulation model of the estuary, multiple candidate locations for tide gates were set within the model, and the upstream process of saltwater intrusion was simulated. By comparing the average salinity of the estuary area with the salinity at key measuring points, the optimal construction location of the tide gate was determined from the feasible construction range. Finally, gate boundaries were set at the determined optimal construction location of the tide gate, and the flow field and salinity field under various scheduling conditions were simulated. By comparing the average salinity of the estuary area with the salinity at key measuring points again, the optimal tide gate scheduling scheme was determined.

[0012] In the above method, the basic hydrodynamic parameter data acquired includes geographical topographic data such as measured underwater topographic elevation and land shoreline boundary coordinates of the estuary, hydrodynamic boundary data such as tidal time series at the open sea boundary and runoff flow at the upstream boundary of the inland river, and fluid physical property parameters including Coriolis force parameters, gravitational acceleration, water density properties, atmospheric pressure, surface wind field, bed roughness, and seawater salinity. When determining the feasible construction area, the bearing capacity and stability of the riverbed foundation are assessed based on riverbed stratigraphic structure data, fault distribution data, and geomechanical parameters. Combined with historical riverbed evolution data, the trends of scour and deposition are analyzed to eliminate unstable areas with insufficient foundation bearing capacity, active faults, and severe scour, thereby selecting areas with stable geological conditions.

[0013] To accurately capture changes in the flow field when establishing a two-dimensional numerical simulation model of the estuary, a multi-scale nested or local refinement technique was employed to construct the grid. Within a range of 500 to 1000 meters upstream and downstream of the pre-set candidate axis of the tide barrier, the grid resolution was transitioned from a coarse grid in the open sea area and then refined to a fine grid. The model includes a coupled hydrodynamic calculation module and a salinity transport and diffusion calculation module.

[0014] The hydrodynamic calculation module is based on a two-dimensional depth-averaged set of unsteady shallow water equations. Its momentum equations consider physical effects such as Coriolis force, water level gradient, atmospheric pressure gradient, baroclinic term generated by density gradient, surface wind stress, bed bottom friction stress, wave radiation shear stress, and horizontal eddy viscosity stress. The salinity transport and diffusion calculation module is based on the mass transport equations, using the velocity field and total water depth to simulate the convection and diffusion processes of salt in the water body.

[0015] To ensure model accuracy, a soft-start time was set during the comparison and calibration process, allowing the boundary driving force to increase linearly from zero to the actual value to achieve a dynamic equilibrium. By comparing the simulated output of tidal level, velocity, and salinity process lines with measured data, the bed roughness, eddy viscosity coefficient, and horizontal salinity diffusion coefficient were adjusted until the tidal level Nash efficiency coefficient and salinity relative error met the preset statistical standards.

[0016] In determining the optimal construction location, the average salinity of the estuary area is obtained by averaging the salinity of all grid nodes within the selected estuary waters in the calculation model. The salinity changes over time at sensitive locations are then extracted as key monitoring point salinities. The selection criterion is to choose a construction location that maximizes the reduction of the average salinity in the estuary area while ensuring that the salinity at the key monitoring points is controlled below the national control standard.

[0017] In determining the optimal scheduling scheme, various scheduling conditions were simulated, including conventional peak-shifting scheduling mode, reverse peak-shifting scheduling mode, and average threshold scheduling mode. Among them, the conventional peak-shifting scheduling mode uses linear interpolation control with half-open or full-open operation based on the extreme tide level; the reverse peak-shifting scheduling mode uses linear interpolation control with full-closed or full-open operation based on the extreme tide level.

[0018] The mean threshold scheduling mode calculates the average tide level over the simulated period as the control threshold. At each time step, it assesses the relationship between the real-time tide level and the average tide level: if the real-time tide level is higher than the average tide level, it is considered a high-risk period for saline intrusion during high tide, and the gate opening is set to fully closed; if the real-time tide level is lower than the average tide level, it is considered a low tide or low water level period, and the gate opening is set to fully open. Comparative analysis shows that the mean threshold scheduling mode is most effective in reducing salinity and has been determined as the optimal tide gate scheduling scheme.

[0019] This invention provides an optimization method for construction location and scheduling schemes to resist the effects of saltwater intrusion. It has the following beneficial effects:

[0020] 1. This invention constructs a two-dimensional numerical simulation model of the estuary, coupling the spatial selection of construction sites with the temporal optimization of operation scheduling. Within the selected geologically stable and feasible range, by quantitatively comparing the average salinity of the estuary area and the salinity of key measuring points under different cross sections, the construction site with the best physical barrier effect against saltwater intrusion is determined. Combined with the subsequent optimized scheduling scheme, the dual optimization of water conservancy facilities in physical site selection and operation strategy is achieved, maximizing the effectiveness of the project in resisting the upstream intrusion of saltwater intrusion.

[0021] 2. This invention proposes a mean threshold scheduling mode based on the average tide level. This mode uses the comparison logic between the real-time tide level and the average tide level during the simulated period to forcibly close the gates during the high tide period when the water level is higher than the average level, cutting off the convection channel for high-concentration salt water to flow upstream; during the low tide period when the water level is lower than the average level, the gates are fully opened to make full use of the upstream runoff to flush away the residual salt in the river channel. Compared with the conventional linear peak staggered scheduling, this strategy can more effectively smooth out the salinity peak and reduce the average salinity in the estuary area.

[0022] 3. This invention comprehensively considers the constraints of estuary geological conditions and the accuracy control of numerical calculations. By eliminating unstable areas with insufficient foundation bearing capacity and active faults based on geological survey data, it ensures that the selected construction location has the safety and long-term stability for engineering implementation. At the same time, the use of multi-scale nesting and local grid refinement technology in the numerical model ensures that the model can accurately reproduce the abrupt flow field characteristics near the tidal barrier, thereby improving the accuracy and reliability of the optimization results. Attached Figure Description

[0024] Figure 1 This is a flowchart of the construction location and scheduling scheme optimization method of the present invention;

[0025] Figure 2 This is a comparison diagram of salinity before and after changing the position of the tide gate in an embodiment of the present invention;

[0026] Figure 3 This is a comparison chart of the salinity curves of the measuring points over time before and after changing the position and scheduling scheme of the tide gate in an embodiment of the present invention. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] See attached document Figure 1The present invention provides a method for optimizing the construction location and scheduling scheme to resist the effect of saltwater intrusion, which specifically includes steps S1, S2, S3 and S4.

[0030] First, perform step S1: Obtain basic hydrodynamic parameter data for the estuary in the upstream area of ​​the saltwater intrusion zone where saline water pollution is relatively severe. Based on the geological conditions of the estuary, determine the feasible location for constructing a tide barrier. In this step, the data obtained forms the physical basis and boundary input for establishing a two-dimensional numerical simulation model of the estuary. The completeness and accuracy of the data directly determine the realism of the subsequent simulation results in reproducing the natural processes.

[0031] Specifically, in step S1, the basic hydrodynamic parameter data acquired includes, but is not limited to: geographic topographic data of the estuary and nearshore areas, hydrodynamic boundary data, and fluid physical property parameters. The geographic topographic data mainly includes the measured underwater topographic elevation (isodiameter line data) of the estuary waters and the coordinate data of the land shoreline boundaries.

[0032] The geographic topographic data was used to construct the numerical computation grid and define the static water depth in the model. and total water depth (in , (Water level). Hydrodynamic boundary data includes tidal time series data at the open sea boundary and runoff data at the upstream inland river boundary. Tidal data at the open sea boundary are determined by measured water level processes obtained from tide gauge stations deployed in a predetermined sea area or by tidal level processes estimated based on harmonic constants. This data drives water movement within the model's computational area and corresponds to the water level gradient term in the model's governing equations. and The solution boundary is determined. The runoff data of the upstream boundary of the inland river is determined based on the measured flow records of the upstream hydrological control station, which serves as the freshwater source input.

[0033] Furthermore, fluid physical property parameters are used to determine key physical coefficients in the model's governing equations, specifically including: Earth's rotation angular velocity. and the latitude of the region Used to calculate Coriolis force parameters ( This parameter determines the Coriolis force term in the governing equations. and Magnitude; gravitational acceleration Reference density of water and the actual density of the water body Used to calculate the baroclinic term generated by the density gradient; atmospheric pressure The atmospheric pressure gradient term is used to calculate the atmospheric pressure gradient; the water surface wind field data is used to calculate the water surface wind stress components. and The data also includes bed surface roughness data. The bed surface roughness data is determined based on riverbed sediment sampling results (such as sediment particle size and vegetation cover), and is expressed as the Manning coefficient or Chezy coefficient, used to calculate the frictional stress components at the bottom of the model. and Simultaneously, seawater salinity data was acquired, including background salinity concentration at the offshore boundary and initial salinity field distribution within the estuary, to be used as the salinity data in the salinity transport and diffusion equation. The initial and boundary conditions.

[0034] Furthermore, in step S1, determining the feasible location for constructing the tide barrier is based on the acquired estuary geological survey data. Based on the riverbed stratigraphic structure data, fault distribution data, and geomechanical parameters obtained from the geological survey, the foundation bearing capacity and stability of the riverbed are assessed. Simultaneously, combined with historical riverbed evolution data, the scouring and deposition trends of the riverbed are analyzed. Within the estuary basin, unstable areas with insufficient foundation bearing capacity, active faults, or severe scouring are eliminated, and areas with stable geological conditions suitable for the construction of hydraulic structures are selected as the feasible construction range for the tide barrier. In subsequent numerical simulation steps, cross-sections at different distances within this feasible construction range will be selected as alternative construction locations for optimization and comparison.

[0035] After completing step S1, proceed to step S2: establish a two-dimensional numerical simulation model of the estuary to simulate the salinity distribution and calibrate it by comparing it with measured salinity data from the estuary. (See attached...) Figure 1 Step S2 is performed after acquiring the basic data, providing a computing platform for subsequent scheme optimization.

[0036] In step S2, the process of establishing a two-dimensional numerical simulation model of the estuary first involves the construction of the computational grid. Using the underwater topographic and shoreline data of the estuary obtained in step S1, the continuous physical computational water area is discretized into a numerical grid composed of multiple computational nodes and units. For estuarine areas with meandering channels and complex cross-sections, unstructured triangular or structured rectangular grids are used to partition the computational domain, and measured topographic elevations are interpolated onto each grid node to define the spatial geometry of the model's bottom surface. The two-dimensional numerical simulation model of the estuary sets the estuary boundary as the open ocean boundary and the upstream boundary of the river as the open inland boundary. At the inland open boundary, flow boundary conditions are set based on flow control data at different design frequencies from hydrological stations, and the inflow water is defined as freshwater with a salinity of 0 PSU. At the open ocean boundary of the estuary, time-varying water level boundary conditions are set based on water level data from tide gauge stations, and a background seawater salinity (e.g., 35 PSU) is set.

[0037] To accurately simulate the abrupt changes in flow field and the narrowing effect near the construction location of the tide barrier, multi-scale nesting or local refinement techniques were employed in the mesh construction of the estuary two-dimensional numerical simulation model. Within a range of 500 to 1000 meters upstream and downstream of the pre-set candidate axis of the tide barrier, the mesh resolution was transitioned from coarse mesh (e.g., 100-200 meters) in the open sea area and then refined to fine mesh (e.g., 10-20 meters) to ensure that the estuary two-dimensional numerical simulation model could capture the rapid changes in water level and local turbulence characteristics caused by the opening and closing of the gate, and to eliminate numerical oscillations.

[0038] Furthermore, the numerical model includes a hydrodynamic calculation module and a salinity transport and diffusion calculation module, which are coupled through the flow field and density field. The hydrodynamic calculation module is based on a two-dimensional depth-averaged unsteady shallow water equation set, used to calculate the water level and flow velocity at each grid node at each time step. In the Cartesian coordinate system, the estuary two-dimensional numerical simulation model is laterally ( The momentum equation for the direction is:

[0039] ;

[0040] Two-dimensional numerical simulation model of estuary longitudinal direction ( The momentum equation for the direction is:

[0041] ;

[0042] The physical symbols in the above hydrodynamic equations are defined as follows: Represents time; , Represents the horizontal spatial coordinates in the Cartesian coordinate system; Represents the total water depth; , They represent the depth averaged values ​​respectively. direction and directional velocity component; The Coriolis force parameter is calculated using the following formula: ,in The Earth's rotational angular velocity, Latitude; Represents gravitational acceleration; Represents water surface elevation; This represents the actual density of the water body, which is updated as salinity changes, thus generating baroclinic gradient force in the momentum equation; The reference density representing water; Represents atmospheric pressure; , Represents wind stress on the water surface and Component of direction; , represent the components of the frictional stress at the bottom of the bed surface in the and directions; , , , represent the components of the wave radiation shear stress in each direction; , , represent the horizontal eddy viscosity stress components; represents the magnitude of the point source flow rate (source term / sink term); , represent the flow velocity of the power source.

[0043] Meanwhile, the salinity transport and diffusion calculation module is based on the mass transport equation, and uses the flow velocity field , and the total water depth calculated by the hydrodynamic module to simulate the convection and diffusion processes of salt in the water body. The convection-diffusion equation for salinity transport is:

[0044] ;

[0045] In the formula, represents the depth-averaged salinity; represents the horizontal salinity diffusion coefficient; represents the salinity concentration released by the point source. By solving this equation, the spatio-temporal distribution of salinity in the entire calculation domain is obtained.

[0046] In the specific operation settings of the two-dimensional estuary numerical simulation model, in order to prevent numerical calculation divergence, the startup mode of the model is configured as soft startup, that is, a soft startup time (such as 1 day, that is, 86,400 seconds) is set. During the soft startup period, the boundary driving force gradually linearly increases from zero to the actual value until the flow field and salinity field of the model reach a dynamic equilibrium state, and then the flow field and salinity field in this state are used as the initial values for subsequent simulations.

[0047] After the two-dimensional estuary numerical simulation model is established, parameter calibration work is carried out. The tidal level, flow velocity and salinity process curves simulated by the two-dimensional estuary numerical simulation model are compared with the measured data obtained in step S1. By adjusting the bed surface roughness (Manning coefficient), eddy viscosity coefficient and horizontal salinity diffusion coefficient in the model, the error between the simulated value and the measured value is controlled within the preset range. The specific evaluation criteria use the root mean square error and Nash efficiency coefficient for quantitative evaluation. Only when the Nash efficiency coefficient of the simulated tidal level and the measured tidal level is greater than 0.9, and the relative error between the simulated salinity and the measured salinity is less than 10%, it is considered that the parameter calibration is qualified. If the error exceeds this range, the Manning coefficient or the horizontal salinity diffusion coefficient The simulation continues until the aforementioned statistical indicators are met to ensure the confidence level of the model's predictions. When the simulation results can reproduce the actual hydrodynamic transport characteristics and saltwater intrusion patterns in the estuary, the model is deemed a valid model and used for subsequent optimization calculations in steps S3 and S4.

[0048] After completing step S2, proceed to step S3: Once the accuracy of the two-dimensional numerical simulation model of the estuary is confirmed, simulate the upstream salinity of the estuary under different tidal barrier construction locations, compare the estuary salinity distribution and the salinity at the measuring points, and determine the possible construction locations for the tidal barrier. (See attached...) Figure 1 Step S3 is performed after the model is built and verified to be qualified. Its core is to use the numerical model to conduct comparative analysis of multiple options.

[0049] In step S3, several specific candidate locations for the tide gate are first set in the estuary model. The selection of candidate locations follows the dual constraints of geology and environment, namely, the site selection should meet the requirements of geological stability, minimal scour and sedimentation changes, and moderate distance from the estuary. Geological stability means that there are no active faults in the selected area and the foundation bearing capacity meets the engineering construction standards; minimal scour and sedimentation changes mean that the riverbed evolution of the selected section is in a relatively balanced state, avoiding severe scour that could endanger the safety of the gate foundation or serious sedimentation that could affect flood control; moderate distance from the estuary means that the site selection should not be too close to the open sea, resulting in excessively large-scale engineering and costs, nor too far inland, resulting in a large number of downstream river sections still being affected by saltwater intrusion.

[0050] Based on this principle, several (e.g., two or more) gate boundary lines that can cut off the water flow are defined in the grid of the two-dimensional numerical simulation model of the estuary, representing different construction location schemes, such as the location near the estuary (denoted as location 1) and the location upstream of the river channel (denoted as location 2).

[0051] For each candidate location, the numerical model established in step S2 is run to simulate the upstream intrusion of saltwater after a tide gate is constructed at that location. To evaluate the passive blocking effect of the construction location itself on salinity distribution, the simulation at this stage is usually set with the same gate operating state (e.g., keeping it closed during saltwater intrusion or scheduling it according to the same baseline rules). After the simulation, the overall salinity distribution cloud map and statistical data for specific areas under each scheme are output.

[0052] See attached document Figure 2 ,in, Figure 2 (a) shows the salinity distribution of the estuary before optimization (i.e., before the construction of tide gates or in the initial state). It can be seen that high salinity water (shown in red and yellow blocks, with salinity values ​​above 15 PSU and even reaching above 22.5 PSU) flows straight in along the deep channel, not only occupying the wide estuary bay, but also penetrating into the narrow inland waterway, causing serious saltwater intrusion.

[0053] Figure 2 (b) shows the estuary salinity distribution after constructing the tide gate at the optimal location (marked as the gate location in the figure) following optimization and screening. A clear comparison reveals that... Figure 2 In (b), the high-salinity water body is effectively blocked on the downstream side of the gate section, and the river water on the upstream side of the gate appears as purple or dark blue (salinity value below 1.5 PSU), which represents low salinity. This indicates that the path of saltwater upstream is physically blocked and the upstream freshwater resources are effectively protected.

[0054] To quantitatively determine the optimal location, step S3 calculates and compares the evaluation indicators for each scheme. The evaluation indicators mainly include the average salinity of the estuary area and the salinity of key measuring points. The regional average salinity is the average salinity of all grid nodes within the selected estuarine area in the calculation model. The calculation yields the percentage reduction in average salinity for different location schemes compared to the case without a tidal barrier (e.g., a 13.4% reduction for location 1 and a 20.6% reduction for location 2). Key measuring point salinity refers to the salinity changes over time at sensitive locations such as ecological reserves, water intakes, or scenic areas extracted from the model.

[0055] The salinity extremes (maximum values) and durations exceeding standards (times when salinity exceeds national control standards) at these monitoring points were compared under different schemes. After comprehensive comparison, the optimal construction location for the tide gate was determined as the location that maximizes the average salinity reduction in the estuary area and ensures stable salinity control at key monitoring points below national standards or specific ecological thresholds. For example, if location 2 shows a significantly better average salinity reduction than location 1 and better protects the upstream water intake, then location 2 was selected as the final optional construction location.

[0056] After completing step S3 and determining the optimal construction location of the tide barrier (e.g., location 2 mentioned above), proceed to step S4: simulate different scheduling schemes at the available construction locations, and again compare the estuary salinity distribution and the salinity at the measuring points to determine the optimal construction location and scheduling scheme for the tide barrier. (See attached...) Figure 1 Step S4 aims to further explore the potential of water conservancy projects in resisting saltwater intrusion through refined operation and management strategies.

[0057] In step S4, based on the constructed two-dimensional hydrodynamic and salinity coupled numerical model, the boundary of the hydraulic structure (gate) is set at the optimal location selected in the model. To optimize the operating rules, four representative scheduling conditions are set and simulated. The specific parameter settings and control logic for these conditions are as follows:

[0058] Operating condition (1) is the no-scheduling mode (baseline scheme): the gate structure attribute in the model is set to remain fully open (opening degree is 1.0) throughout the entire simulation period. The water exchange situation is simulated when there is only physical channel narrowing but no active interception measures at the construction location, which serves as a benchmark for evaluating the effectiveness of other scheduling schemes.

[0059] Operating condition (2) is the conventional off-peak scheduling mode: a linear control strategy that varies with the tide level is adopted. The specific implementation method is: real-time tide level data of the outer sea boundary or downstream of the gate are read in the two-dimensional hydrodynamic and salinity coupled numerical model, and the highest tide level value in the annual tide level process is identified ( ) and lowest tide level ( Set when the real-time tide level reaches... When the tide level is at a certain point, the gate opening is limited to 0.5; when the real-time tide level is... At that time, the gate opening is set to 1.0 (fully open). For those between and Any real-time tide level between Gate opening Determined by calculation using a linear interpolation function.

[0060] The specific linear interpolation control function is expressed as follows:

[0061] ;

[0062] In the formula, for The gate opening at any given moment; for Real-time tide level at any given moment; and These represent the highest and lowest tide levels within a preset period. This scheme limits the flow of high-salinity water by partially closing the gates during high tide.

[0063] Operating condition (3) is a reverse peak-shifting scheduling mode: it also adopts a linear control strategy, but increases the blocking force at high tide. It is set that when the real-time tide level reaches... When the tide level is 0, the gate is completely closed (opening degree is 0); when the real-time tide level is 0, the gate is completely closed (opening degree is 0). At that time, the gate is fully open (opening degree is 1.0). The opening degree at intermediate moments is also adjusted linearly based on the real-time tide level.

[0064] Its control function is expressed as:

[0065] ;

[0066] This functional relationship ensures that the gate opening decreases linearly as the tide rises, until it is completely closed at high tide. This scheme aims to test the effectiveness of completely cutting off the upstream passage at high tide.

[0067] Operating condition (4) is the mean threshold scheduling mode: threshold-based binarized logic control is adopted. First, the average tide level for the whole year or the simulated period is calculated. This serves as a control threshold. At each time step of the numerical simulation, the real-time tide level is determined. and Relationship: If If the area is deemed to be at high risk of saltwater intrusion during high tide, the gate opening will be forcibly set to 0 (fully closed) to completely block the upstream flow of highly saline water using a physical barrier; if If it is determined to be a low tide or low water level period, the gate opening is set to 1.0 (fully open) to use the freshwater runoff from upstream to flush away the residual salt in the river channel.

[0068] Unsteady simulations were performed by loading the four scheduling conditions mentioned above into the numerical model, and the flow field and salinity field under each condition were calculated. After the simulation, the salinity values ​​of all grid nodes in the target area of ​​the estuary were extracted to calculate the regional average salinity, and salinity time series data of key sensitive points (such as ecological protection areas and water intakes of water sources) were extracted.

[0069] See attached document Figure 3 The figure details the dynamic differences in salinity before and after scheduling optimization. The orange curve represents the salinity change at the measuring point before optimization (or Condition 1), exhibiting dramatic periodic fluctuations. The peak value repeatedly climbed to the 20-25 PSU range, and the high salinity period lasted for a long time, indicating that saltwater intrusion swept in with the rising tide, severely impacting the water quality around the measuring point. The blue curve represents the salinity change at the measuring point after adopting the optimal location and optimal scheduling scheme (Condition 4).

[0070] As can be seen from the comparison, the overall baseline of the blue curve is lowered, the salinity peak is effectively flattened, and the salinity value is controlled below 15 PSU for most of the time, even approaching freshwater levels in some periods. This indicates that the strategy of closing all channels during high tide and opening all channels during low tide in Condition 4 precisely cuts off the channel during the period when the salinity intrusion force is strongest, and maximizes the salinity suppression effect of freshwater during the ebb tide period.

[0071] Based on the simulation data, when using condition (4), the average salinity in the estuary area drops to the lowest level (e.g., from 4.87 PSU in condition 1 to 0.83 PSU), and the salinity exceeding the standard at key measuring points is the shortest. Therefore, step S4 ultimately determines condition (4) as the optimal tidal barrier scheduling scheme. Combined with the optimal location determined in step S3, a complete optimization result of the construction location and scheduling scheme for enhancing the tidal barrier's ability to resist upstream saltwater intrusion is formed.

[0072] Based on the implementation of steps S1 to S4 above, the implementation effect of the optimization method for construction location and scheduling scheme of the enhanced tide gate to resist the upstream intrusion of saltwater is now summarized.

[0073] See attached document Figure 2 and attached Figure 3 Through the systematic optimization process of this invention, the dual optimization of spatial site selection and time scheduling for the construction project of the estuary tidal barrier is achieved. The specific implementation effect is reflected in the following quantitative data and physical field distribution improvement.

[0074] First, at the spatial location selection level, the simulation comparison in step S3 clarified the differences in the physical barriers to upstream saltwater intrusion at different river cross-sections. In the simulation experiment, the average salinity of the estuary area was compared with that without a tide gate when the tide barrier was located at different cross-sections (locations 1, 2, and 3). The calculation results showed that the reduction effect of saltwater intrusion varied depending on the location. Location 1 reduced the average salinity of the estuary by 13.4%, location 3 by 14.7%, and location 2 by 20.6%. Based on this quantitative data, this invention accurately identified location 2 as the optimal construction cross-section for physically blocking saltwater intrusion. Figure 2 As shown in (b), after the tidal gate was built at the optimal location, the high salinity water front was restricted to the downstream of the gate, and the salinity of the vast inland waters upstream of the gate remained at a low level (purple area), effectively delineating the physical boundary between fresh and brackish water.

[0075] Secondly, at the operational scheduling strategy level, the control mechanism of different opening and closing rules on salinity transport flux was revealed through the simulation of the operating conditions in step S4. Based on the determined optimal location (location 2), the simulation results show that: if the un-scheduled operating condition (1) is used, the regional average salinity is 4.87 PSU; if the conventional staggered peak scheduling operating condition (2) is used, the regional average salinity is 5.06 PSU, indicating that simply operating half-open is not conducive to salinity suppression due to the disturbance of the flow field; if the reverse staggered peak scheduling operating condition (3) is used, the regional average salinity drops to 2.94 PSU, and the effect is improved; while using the mean threshold scheduling operating condition (4) preferred by this invention, that is, when the tide level is higher than the annual average tide level, the gate is fully closed, and when the tide level is lower than the annual average tide level, the gate is fully open, and the regional average salinity is significantly reduced to 0.83 PSU. This data shows that the average salinity of operating condition (4) is only about 17% of that of the un-scheduled operating condition, which is a huge reduction.

[0076] See attached document Figure 3 The horizontal axis of the figure shows the time series during October 2024 (e.g., October 10 to October 22), and the vertical axis represents the salinity value (unit: PSU), showing the dynamic difference in salinity before and after scheduling optimization.

[0077] The orange curve represents the salinity change at the measurement points before optimization, exhibiting dramatic periodic fluctuations. For example... Figure 3 As shown, the optimized salinity curve (blue) demonstrates that this method not only reduces the average value but also smooths out extreme values. This optimization scheme utilizes the principles of tidal dynamics, forming a solid wave wall by completely closing the gates during high tide, thus cutting off the convective input channel of high-concentration salt water; during low tide, the gates are fully opened to maximize the use of the kinetic energy of upstream runoff, pushing any trace amounts of salt that may seep into the river channel downstream to the open sea. Through the combination of the optimal location and the optimal scheduling scheme determined by the above method, effective protection of freshwater resources in the estuary area during periods of severe saltwater intrusion is achieved, reducing the salinity index at ecologically sensitive points and water intakes, and providing quantifiable and verifiable scientific basis for the planning, design, and operation management of estuarine water conservancy projects.

Claims

1. A method for optimizing the construction location and scheduling scheme to resist the upstream effects of saltwater intrusion, characterized in that, Includes the following steps: Step S1: Obtain basic hydrodynamic parameter data of the estuary in the upstream area of ​​saltwater intrusion, and obtain geological survey data of the estuary. Based on the geological survey data of the estuary, determine the feasible construction range for the construction of the tide barrier. Step S2: Establish a two-dimensional numerical simulation model of the estuary, set the model parameters using the basic hydrodynamic parameter data, and calibrate the two-dimensional numerical simulation model of the estuary using measured salinity data until the simulation error meets the preset requirements, and obtain an effective two-dimensional numerical simulation model of the estuary. Step S3: Using the effective two-dimensional numerical simulation model of the estuary, set multiple candidate locations for the tide gate in the two-dimensional numerical simulation model of the estuary, simulate the upstream process of saltwater intrusion, and determine the optimal construction location of the tide gate from the feasible construction range by comparing the average salinity of the estuary area and the salinity of key measuring points. Step S4: Set the gate boundary at the optimal construction location of the tide barrier, simulate the flow field and salinity field under various scheduling conditions, and determine the optimal tide barrier scheduling scheme by comparing the average salinity of the estuary area and the salinity of key measuring points.

2. The method for optimizing the construction location and scheduling scheme to resist the upstream intrusion of saltwater as described in claim 1, characterized in that, In step S1, the basic hydrodynamic parameter data includes: Geographic topographic data including measured underwater topographic elevations of the estuary and coordinates of the land shoreline boundaries; Hydrodynamic boundary data including tidal time series at the open sea boundary and runoff flow at the upper inland river boundary; It also includes fluid physical property parameters such as Coriolis force parameters, gravitational acceleration, reference density of water, actual density of water, atmospheric pressure, water surface wind field data, bed surface roughness data, and seawater salinity data.

3. The method for optimizing the construction location and scheduling scheme to resist the upstream intrusion of saltwater as described in claim 1, characterized in that, In step S1, the specific steps for determining the feasible construction scope of the tide barrier include: Based on the aforementioned estuary geological survey data, data on riverbed stratigraphic structure, fault distribution, and geomechanical parameters were obtained. Assess the foundation bearing capacity and stability of the riverbed, and analyze the scouring and deposition trends of the riverbed by combining historical riverbed evolution data; After excluding unstable areas within the estuary basin with insufficient foundation bearing capacity, active faults, or severe scouring, areas with stable geological conditions were selected as the feasible construction area.

4. The method for optimizing the construction location and scheduling scheme to resist the upstream intrusion of saltwater as described in claim 1, characterized in that, In step S2, when establishing the two-dimensional numerical simulation model of the estuary, multi-scale nesting or local refinement techniques are used to construct the mesh; Within a range of 500 to 1,000 meters upstream and downstream of the pre-set candidate axis for the tide barrier, the grid resolution will be transitioned from a coarse grid in the open sea area and then refined to a fine grid.

5. The method for optimizing the construction location and scheduling scheme to resist the upstream intrusion of saltwater as described in claim 1, characterized in that, The two-dimensional numerical simulation model of the estuary includes a hydrodynamic calculation module and a salinity transport and diffusion calculation module. The hydrodynamic calculation module is based on a two-dimensional depth-averaged set of unsteady shallow water equations, the momentum equation of which includes: Coriolis force term, water level gradient term, atmospheric pressure gradient term, baroclinic term generated by density gradient, surface wind stress term, bed bottom friction stress term, wave radiation shear stress term, and horizontal eddy viscosity stress term; The salinity transport and diffusion calculation module is based on the mass transport equation and uses the velocity field and total water depth calculated by the hydrodynamic calculation module to simulate the convection and diffusion process of salt in the water body.

6. The method for optimizing the construction location and scheduling scheme to resist the upstream intrusion of saltwater as described in claim 1, characterized in that, In step S2, the specific steps for comparing and calibrating the two-dimensional numerical simulation model of the estuary to obtain the effective two-dimensional numerical simulation model of the estuary include: Set a soft start time to allow the boundary driving force to increase linearly from zero to the actual value until the flow field and salinity field of the two-dimensional numerical simulation model of the estuary reach a dynamic equilibrium state. The simulated tidal level, simulated flow velocity, and simulated salinity process lines output by the two-dimensional numerical simulation model of the estuary are compared with the measured data. Adjust the bed roughness, eddy viscosity coefficient, and horizontal salinity diffusion coefficient in the two-dimensional numerical simulation model of the estuary until the Nash efficiency coefficient between the simulated tidal level and the measured tidal level is greater than a preset threshold, and the relative error between the simulated salinity and the measured salinity is less than a preset ratio.

7. The method for optimizing the construction location and scheduling scheme to resist the upstream intrusion of saltwater as described in claim 1, characterized in that, In step S3, the average salinity of the estuary area is the average salinity of all grid nodes within the selected estuary water area in the two-dimensional numerical simulation model of the estuary. The salinity at the key measuring points is the salinity change over time at the sensitive locations in the two-dimensional numerical simulation model of the estuary. The criteria for determining the optimal location for the tidal barrier are: to select a location that maximizes the reduction in average salinity in the estuary area and ensures that the salinity at the key measuring points is below the national control standard.

8. The method for optimizing the construction location and scheduling scheme to resist the upstream intrusion of saltwater as described in claim 1, characterized in that, In step S4, the various scheduling conditions include a conventional peak-shaving scheduling mode, and the control strategy for the conventional peak-shaving scheduling mode is as follows: Identify the highest and lowest tide levels throughout the year; When the real-time tide level reaches the highest tide level value, the gate opening will be restricted to a half-open state; When the real-time tide level is the lowest tide level, the gate opening is set to fully open. For the real-time tide level between the highest tide level and the lowest tide level, the gate opening is calculated using a linear interpolation function.

9. The method for optimizing the construction location and scheduling scheme to resist the upstream intrusion of saltwater as described in claim 1, characterized in that, In step S4, the various scheduling conditions include a reverse peak-shifting scheduling mode, and the control strategy for the reverse peak-shifting scheduling mode is as follows: When the real-time tide level reaches the highest tide level, the gate opening is set to fully closed. When the real-time tide level is at its lowest value, set the gate opening to fully open. For real-time tide levels between the highest and lowest tide levels, the gate opening decreases linearly as the tide level rises.

10. The method for optimizing the construction location and scheduling scheme to resist the upstream intrusion of saltwater as described in claim 1, characterized in that, In step S4, the multiple scheduling conditions include an average threshold scheduling mode, and the control strategy for the average threshold scheduling mode is as follows: The average tide level during the simulation period is calculated as the control threshold. Determine the relationship between the real-time tide level and the average tide level at each time step of the two-dimensional numerical simulation model of the estuary: If the real-time tide level is greater than the average tide level, it is determined to be a high-risk period for saltwater intrusion during high tide, and the gate opening is set to fully closed. If the real-time tide level is less than the average tide level, it is determined to be an ebb tide or a low water level period, and the gate opening is set to fully open. Among them, the mean threshold scheduling mode was determined to be the optimal tide gate scheduling scheme after comparison.

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