A water engineering group comprehensive regulation method and system for large shallow lake blue-green algae bloom prevention and control

Abstract

This invention discloses a comprehensive regulation method and system for water engineering systems to control cyanobacterial blooms in large shallow lakes, belonging to the field of water environment technology evaluation. The method includes: identifying the research object and pre-setting a water diversion scheme; optimizing the inlet combination, inlet flow rate, outlet combination, and outlet flow rate allocation; then, using a three-dimensional mathematical model of wind-driven flow across the entire Taihu Lake area, selecting the optimal hydrodynamic scheme A with the objective of minimizing the spatial distribution of the lake's water exchange cycle, and selecting the optimal water quality scheme B with the objective of maximizing the water quality improvement rate and compliance rate; finally, based on schemes A and B, and combining the overall physical model of wind-driven flow across the entire Taihu Lake area and the three-dimensional mathematical model of Taihu Lake, determining the optimal scheduling scheme for controlling cyanobacterial blooms with the greatest benefit and fastest water exchange, with the objectives of a short average water exchange cycle and low nitrogen and phosphorus load entering the lake. This invention provides key technical support for the precise control of cyanobacterial blooms and the continuous improvement of the water environment in Taihu Lake and similar large shallow lakes.

Description

Technical Field

[0001] This invention belongs to the field of water environment technology assessment, and specifically relates to a comprehensive regulation method and system for water engineering groups to control cyanobacterial blooms in large shallow lakes. Background Technology

[0002] The new round of the "Overall Plan for Comprehensive Water Environment Management in the Taihu Lake Basin," issued by six departments including the National Development and Reform Commission, aims to make Taihu Lake a "benchmark for lake management nationwide," clearly defining the high goals of "two protections and two improvements." Faced with new challenges and a new situation in Taihu Lake management, Jiangsu Province has embarked on a new round of comprehensive Taihu Lake management. Given the difficulty in rapidly reducing phosphorus and nitrogen levels in the short term, accelerating lake water flow and implementing comprehensive regulation of nitrogen and phosphorus pollution loads and cyanobacterial bloom control water engineering projects to disrupt the relatively static hydrodynamic conditions required for cyanobacterial growth and reproduction has become a realistic option. In recent years, many water diversion and drainage projects have been built along the Yangtze River in the Taihu Lake basin to discharge floodwaters into the Yangtze River during high water periods and draw water from the Yangtze River during low water periods. Through reasonable scheduling of sluice gates along the river, Yangtze River water is diverted into the basin's river network and Taihu Lake. The Taihu Lake Management Bureau conducted a "Yangtze River to Taihu Lake" water diversion experiment, further strengthening the connectivity of rivers and lakes in the basin. Practice has shown that the "Yangtze River to Taihu Lake" water diversion project has accelerated the flow of water in the basin, shortened the water exchange cycle of Taihu Lake, and improved the self-purification capacity of rivers and lakes, playing a positive role in improving the water environment of Taihu Lake and its surrounding river network. In recent years, with the accelerated implementation of the Xinmeng River, Xingou River, and Zoumatang projects, the expansion of the Taihu Lake water diversion project is gradually being realized, providing an engineering foundation for accelerating the flow of water in Taihu Lake and breaking the hydrodynamic conditions for cyanobacteria growth.

[0003] Despite multiple rounds of comprehensive management, the overall water quality of Taihu Lake has continued to improve. However, submerged vegetation remains severely degraded, the ecosystem remains fragile, and nitrogen and phosphorus concentrations still exceed the threshold for cyanobacterial blooms. Under suitable hydrological and meteorological conditions, cyanobacteria can still bloom on a large scale, threatening drinking water safety and ecosystem health. Currently, the basin's water diversion and drainage capacity has increased exponentially, resulting in a new pattern of "large-scale inflow and outflow" of water in Taihu Lake. This has led to new global changes in the lake's hydrology, hydrodynamics, and material exchange. Driven by this, the water quality of Taihu Lake is showing a trend towards homogenization, and the aquatic ecosystem is facing new adjustments and rebalancing. Cyanobacterial blooms are exhibiting multiple concurrent and spreading patterns, posing new challenges to prevention and control. Currently, the use of water diversion projects for cyanobacterial bloom control is still in the exploratory stage, and a comprehensive water environment management plan for the basin has not yet been formulated. The impact of the Taihu Lake basin's interconnected water diversion on the aquatic ecological environment lacks systematic summarization. Due to unclear research on the mechanism of cyanobacterial bloom control through water diversion, and the unknown effects and impacts of control measures on cyanobacterial bloom control, water environment management in the basin is often in a localized, short-duration experimental phase. Taihu Lake and its surrounding river network have a shallow gradient, slow flow velocity, and numerous pocket-shaped bays. Domestic and international research on optimizing water conservancy project scheduling, ensuring water quality flowing into the lake, accelerating water flow, and the effect of water flow on cyanobacteria suppression is limited, and there is a lack of relevant literature and research findings. Therefore, it is urgent to develop a comprehensive airflow control technology based on existing scheduling experience. This technology can systematically analyze the combined control effects of water conservancy projects and scientifically optimize scheduling schemes, providing key technical support for the precise prevention and control of cyanobacterial blooms and the continuous improvement of the water environment in Taihu Lake and similar large shallow lakes. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a comprehensive regulation method for water engineering clusters based on the prevention and control of cyanobacterial blooms in large shallow lakes, providing key technical support for the precise prevention and control of cyanobacterial blooms and the continuous improvement of the water environment in Taihu Lake and similar large shallow lakes.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A comprehensive regulation method for water conservancy projects based on the prevention and control of cyanobacterial blooms in large shallow lakes includes the following steps:

[0007] Step 1: Identify the large shallow lake to be studied and obtain a pre-set water diversion and drainage plan for the large shallow lake;

[0008] Step 2: Determine the optimal inlet combination F1, the optimal flow distribution ratio F2 for each inlet, the optimal outlet combination F3, and the optimal flow distribution ratio F4 for each outlet of the large shallow lake.

[0009] Step 3: With F1, F2, F3 and F4 fixed, use the three-dimensional mathematical model of wind-driven flow in the entire Taihu Lake area to calculate the spatial distribution value of the water exchange cycle in the lake area under each water diversion scheme. Based on the spatial distribution value of the water exchange cycle in the lake area, select the optimal water diversion scheme A with hydrodynamic indicators as the reference.

[0010] Step 4: With F1, F2, F3 and F4 fixed, use the three-dimensional mathematical model of wind-driven flow in the entire Taihu Lake area to calculate the water quality improvement rate and compliance rate of the lake area under each water diversion scheme, and select the optimal water diversion scheme B based on water quality indicators.

[0011] Step 5: Based on the determined optimal water diversion scheme A (referring to hydrodynamic indicators) and optimal water diversion scheme B (referring to water quality indicators), the Taihu Lake wind-driven flow whole-lake area physical model test and the Taihu Lake whole-lake area wind-driven flow three-dimensional mathematical model are combined to determine the optimal scheme for preventing cyanobacterial blooms in Taihu Lake water diversion and diversion, which has the greatest benefit and fastest water exchange, with the optimization function objective of a short average water exchange cycle and a low total nitrogen and phosphorus pollution load entering the lake.

[0012] Furthermore, the method for determining the optimal inlet combination F1 is as follows: identify the existing lake inlets, arrange and combine all the lake inlets, and use the three-dimensional mathematical model of wind-driven flow in the entire Taihu Lake area to numerically simulate the hydraulic residence time of the Yangtze River water diverted into Taihu Lake under the same water diversion flow and different combinations to calculate the average water exchange cycle of the lake area under the same water diversion flow and different combinations. The combination corresponding to the minimum average water exchange cycle is taken as the optimal inlet combination F1.

[0013] Given the optimal inlet combination F1, the water level, hydrodynamic structure, water exchange cycle, and main flow path under different flow distribution ratios of the inlets are measured using the overall physical model of wind-driven flow in the entire Taihu Lake area. The flow distribution ratio corresponding to the minimum average water exchange cycle is the optimal flow distribution ratio F2 of the inlets.

[0014] Based on the determined optimal inlet combination F1 and the optimal inlet flow distribution ratio F2, and given that the existing lake outlets are determined, all the lake outlets are arranged and combined. Using the three-dimensional mathematical model of wind-driven flow in the entire Taihu Lake area, the hydraulic residence time of the Yangtze River water diverted into Taihu Lake is numerically simulated to calculate the average water exchange cycle of the lake area under each combination. The combination corresponding to the minimum average water exchange cycle is the optimal outlet combination F3.

[0015] Based on the determined optimal inlet combination F1, optimal inlet flow distribution ratio F2, and optimal outlet combination F3, the average water exchange cycle of the lake area under different outlet flow distribution ratios was measured using the overall physical model of wind-driven flow in the entire Taihu Lake area. The flow distribution ratio corresponding to the minimum average water exchange cycle is the optimal outlet flow distribution ratio F4.

[0016] Furthermore, the three-dimensional mathematical model of wind-driven flow in the entire Taihu Lake area includes the governing equations for flow field motion, the numerical simulation equations for the hydraulic residence time of Yangtze River water diverted into Taihu Lake, and the pollutant concentration diffusion equations:

[0017] 1) Flow field motion laws, based on the static pressure assumption and the Boussinesq eddy viscosity assumption, and introducing... Coordinate system:

[0018] ,

[0019] In the formula, For point The water level at that location; Water level; The riverbed relative to point Distance from the reference plane The total water depth, i.e. The range of coordinate variation is ;

[0020] Applying the joint differentiation rule, the basic governing equations for the motion of wind-driven currents in a layered three-dimensional shallow lake in the wind-driven current flow field model are as follows:

[0021] ,

[0022] ,

[0023] ,

[0024] , ,

[0025] ,

[0026] In the formula: They are layered respectively Flow velocity in direction For layering directional flow velocity; The Coriolis force coefficient, This is the Earth's rotational angular velocity. The local geographical latitude; The density of algae in water, The density is that of clean water at room temperature; It is the horizontal eddy viscosity coefficient. The vertical eddy viscosity coefficient; For bottom stress, , The drag coefficient, The flow velocity at the top of the bed; For water surface wind stress, , air density, The wind stress coefficient on the water surface The wind speed is 10m above the water surface; based on flow field simulation, the flow field distribution under different wind speeds is obtained, and the mainstream path under different wind fields is obtained.

[0027] 2) The basic equation for the numerical simulation of the hydraulic residence time of Yangtze River passenger water diverted into Taihu Lake is:

[0028] ,

[0029] In the formula, For the concentration of the guest water, , , They are respectively the guest water in , , Diffusion coefficient in the direction of travel;

[0030] Numerical simulation was used to predict and analyze the diffusion and migration process of the Yangtze River water diverted into Taihu Lake, calculate the hydraulic residence time of the Yangtze River water, and obtain the spatial distribution of the water exchange cycle.

[0031] 3) The equation for the diffusion and migration of pollutant concentrations is:

[0032] ,

[0033] In the formula, For pollutant concentration, , , The pollutants are respectively in , , The diffusion coefficient in the direction of water diversion; by numerically calculating the pollutant concentration, the diffusion process of pollutants when water is diverted into Taihu Lake is simulated.

[0034] The calculation area of ​​the three-dimensional mathematical model of wind-driven flow in the entire Taihu Lake area is divided into triangular unit meshes, with a total of 8720 nodes and 16170 units, and 15 layers in the vertical direction; the mesh is locally refined according to the calculation needs.

[0035] Furthermore, the Taihu Lake whole-lake wind-driven current overall physical model test refers to using the Taihu Lake whole-lake wind-driven current overall physical model, employing multiple experimental methods including wave height meter, large-scale surface flow field measurement system (LSPIV), acoustic Doppler point velocity meter (ADV), and underwater PIV velocity measurement system (UWPIV) to measure hydrodynamic indicators, and using planar laser-induced fluorescence system (PLIF) to measure water quality indicators; the hydrodynamic indicators include at least one of water level, hydrodynamic structure, water exchange cycle, and mainstream path; the water quality indicator table includes at least one of chemical oxygen demand (COD), ammonia nitrogen (NH3-N), total phosphorus (TP), and total nitrogen (TN).

[0036] Furthermore, a wave height meter was used to measure water level changes, a large-scale surface flow field measurement system (LSPIV) was used to measure surface velocity within 4 cm below the water surface, and an acoustic Doppler point velocity meter (ADV) and an underwater PIV velocity measurement system (UWPIV) were used to measure vertical velocity at measuring points from 4 cm below the water surface to 2 cm above the riverbed bottom. Based on the measured velocity at different measuring points, the impact of water diversion on the hydrodynamic structure of the target lake area was obtained.

[0037] A planar laser-induced fluorescence (PLIF) system was used to measure and analyze the concentration fields of nitrogen and phosphorus pollutants in real time, enabling the tracking of the diffusion and migration process of pollutant concentrations, the mixing process of incoming water and target shallow lake water, and the measurement of water exchange cycle and water quality indicators.

[0038] Furthermore, a holistic physical model experiment of wind-driven flow was conducted across the entire Taihu Lake area to demonstrate the mixing process of imported water and target shallow lake water under different wind speeds and water diversion flow rates. The experiment simulated and analyzed the changes in lake flow structure caused by different water diversion schemes, and studied the effects of water diversion on changes in nitrogen and phosphorus pollution loads and on the control of cyanobacterial blooms.

[0039] Furthermore, with the optimization objective of a short average water exchange cycle and a low total nitrogen and phosphorus pollution load entering the lake, the study analyzed the impact of different water diversion schemes on hydrodynamics, water level changes, and the control of cyanobacterial blooms in different lake areas through a combination of physical model experiments and hydraulic residence time numerical simulations. The study determined the optimal water diversion scheme for controlling cyanobacterial blooms that maximizes benefits and achieves the fastest water exchange among different combinations of water diversion routes.

[0040] Furthermore, this study analyzes the water quality and quantity requirements for total nitrogen, total phosphorus, and ammonia nitrogen in controlling cyanobacterial blooms through water diversion and flow regulation. It proposes suitable water diversion quantity requirements for three different seasonal periods under hydrological conditions, including typical high-water years, normal-water years, and low-water years: the spring period when cyanobacteria gain dominance, the summer period when cyanobacteria flourish, and the autumn / winter period when cyanobacteria decline. The study also analyzes the differences in the hydrodynamic inhibition of cyanobacterial growth by water diversion and flow regulation in different seasons and proposes seasonal water diversion recommendations.

[0041] This invention also protects a comprehensive water engineering system for controlling cyanobacterial blooms in large shallow lakes, comprising: an inlet / outlet determination module, which determines the optimal inlet combination, the optimal flow distribution ratio of each inlet, the optimal outlet combination, and the optimal flow distribution ratio of each outlet based on a preset water diversion and diversion scheme; a hydrodynamic optimal scheme determination module, which calculates the spatial distribution value of the average water exchange cycle of the lake area under each water diversion and diversion scheme based on the determined optimal inlet combination, the optimal flow distribution ratio of each inlet, the optimal outlet combination, and the optimal flow distribution ratio of each outlet, and selects the optimal water diversion and diversion scheme A based on hydrodynamic indicators; and a water quality optimal scheme determination module, which determines the optimal inlet combination, the optimal inlet combination, the optimal flow distribution ratio of each inlet, the optimal outlet combination, and the optimal flow distribution ratio of each outlet, and calculates the spatial distribution value of the average water exchange cycle of the lake area based on the spatial distribution value of the average water exchange cycle of the lake area, and selects the optimal water diversion and diversion scheme A based on hydrodynamic indicators; and a water quality optimal scheme determination module, which determines the optimal inlet combination, the optimal inlet combination, the optimal inlet combination, the optimal inlet combination, and the optimal water exchange cycle based on the determined optimal inlet combination. The optimal flow distribution ratios for each inlet and outlet, as well as the optimal flow distribution ratios for each outlet, are used to calculate the water quality improvement rate and compliance rate of the lake area under each water diversion scheme. Based on the water quality improvement rate and compliance rate, the optimal water diversion scheme B, with water quality indicators as the reference, is selected. In the comprehensive optimization module, based on the optimal water diversion scheme A with hydrodynamic indicators as the reference and the optimal water diversion scheme B with water quality indicators as the reference, combined with the overall physical model test of the wind-driven flow in the entire Taihu Lake area and the numerical simulation of the hydraulic residence time of the Yangtze River passenger water diverted into Taihu Lake using the three-dimensional mathematical model of the wind-driven flow in the entire Taihu Lake area, the optimal scheme for controlling cyanobacterial blooms in Taihu Lake water diversion and diversion with the greatest benefit and fastest water exchange is determined for different reference water diversion route combinations.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] This invention employs a three-dimensional mathematical model and a physical model of wind-driven flow across the entire Taihu Lake area, along with prototype observations. Based on the optimization objectives of minimizing the average water exchange cycle and nitrogen and phosphorus pollution load, and considering various factors, it conducts comprehensive regulation of water engineering systems for the prevention and control of cyanobacterial blooms. It proposes an optimized scheduling decision for water engineering systems used for water diversion and diversion to control cyanobacterial blooms, providing key technical support for the precise prevention and control of cyanobacterial blooms and the continuous improvement of the water environment in Taihu Lake and similar large shallow lakes. Attached Figure Description

[0044] Figure 1 This is a flowchart of the method of the present invention;

[0045] Figure 2 This will create a new water diversion pattern for the Taihu Lake water conservancy project group, characterized by "two inflows and three outflows."

[0046] Figure 3 A comprehensive physical model of the entire Taihu Lake area, including the wind-driven currents.

[0047] Figure 4 A schematic diagram of particle tracing and flow field measurement results for a large-scale surface process measurement system;

[0048] Figure 5 This is a schematic diagram of vertical velocity testing using an acoustic Doppler point current meter and an underwater PIV velocity measurement system.

[0049] Figure 6 A schematic diagram of the vertical arrangement of velocity measuring points on an acoustic Doppler point-type current meter;

[0050] Figure 7 This is a schematic diagram of the measurement results from the underwater PIV velocity measurement system.

[0051] Figure 8 The results of the PLIF experiment on the concentration of imported water based on the overall physical model of the entire Taihu Lake area with wind-driven currents;

[0052] Figure 9 A schematic diagram illustrating the impact of the new water diversion pattern of the Taihu Lake water conservancy project group on the hydrodynamic characteristics of Zhushui Bay.

[0053] Figure 10 A schematic diagram of the migration and diffusion process of water diverted into Taihu Lake by the Taihu Water Project Group. Detailed Implementation

[0054] To make the technical solution of the present invention clearer, the technical solution of the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

[0055] like Figure 1 As shown, the present invention provides a comprehensive regulation method for water engineering groups based on the prevention and control of cyanobacterial blooms in large shallow lakes, comprising the following steps:

[0056] Step 1: Identify Taihu Lake as a large, shallow lake to be studied, and obtain a pre-designed water diversion plan for Taihu Lake, namely, a new water diversion pattern of "two inflows and three outflows" for the Taihu Lake water conservancy project group, based on the inflow of water from the Wangyu River and Xinmeng River, the outflow of water from the Xingou River, the confluence of the Liangxi River and Zoumatang River into the Grand Canal, and the outflow of water from the Taipu River (e.g., Figure 2 As shown), the "Taihu Lake Grand Circulation" is formed, with the Wangyu River and Xinmeng River entering and the Xingou River and Taipu River exiting, and the "Three Bay Small Circulation" is formed, with the Xinmeng River → Zhushan Bay → Meiliang Bay → Xingou River and the Wangyu River → Gonghu Bay → Meiliang Bay → Liangxi River.

[0057] Step 2: Based on the new water diversion pattern of the Taihu Lake water engineering group, with the goal of improving the hydrodynamics and water environment of the three bays in the northern part of Taihu Lake, namely Zhushan Bay, Meiliang Bay and Gonghu Bay, determine the optimal inlet combination F1, the optimal flow distribution ratio of each inlet F2, the optimal outlet combination F3 and the optimal flow distribution ratio of each outlet F4.

[0058] Step 3: With F1, F2, F3 and F4 fixed, the three-dimensional mathematical model of wind-driven flow in the whole Taihu Lake area is used to numerically simulate the hydraulic residence time of the Yangtze River passenger water diverted into Taihu Lake under each water diversion scheme to calculate the spatial distribution value of the water exchange cycle in the lake area. Based on the spatial distribution value of the water exchange cycle in the lake area, the optimal water diversion scheme A with hydrodynamic indicators as the reference is selected.

[0059] Step 4: With F1, F2, F3, and F4 fixed, the numerical simulation of the pollutant concentration diffusion and migration equation of the three-dimensional mathematical model of wind-driven flow in the entire Taihu Lake area is used to calculate the water quality improvement rate and compliance rate of the lake area under each water diversion scheme, and the optimal water diversion scheme B based on water quality indicators is selected.

[0060] Step 5: Based on the determined optimal water diversion scheme A (referring to hydrodynamic indicators) and optimal water diversion scheme B (referring to water quality indicators), the optimal scheme for controlling cyanobacterial blooms in Taihu Lake is determined by combining the overall physical model test of the entire Taihu Lake area with the numerical simulation of the hydraulic residence time of the Yangtze River passenger water diverted into Taihu Lake using the three-dimensional mathematical model of the entire Taihu Lake area with wind-driven currents. The optimization function objective is to determine the optimal scheme for controlling cyanobacterial blooms in Taihu Lake with the maximum benefit and the fastest water exchange among different combinations of water diversion routes.

[0061] Specifically, the method for determining the optimal inlet combination F1 is as follows: The existing inlets of Taihu Lake are Wangyu River and Xinmeng River. The existing inlets are arranged and combined. The average water exchange cycle of the lake area under the same water diversion flow and different combinations is calculated by numerical simulation of the hydraulic residence time of the Yangtze River water diverted into Taihu Lake using the three-dimensional mathematical model of wind-driven flow in the whole Taihu Lake area. The combination corresponding to the minimum average water exchange cycle is taken as the optimal inlet combination F1.

[0062] Given the optimal inlet combination F1, the water level, hydrodynamic structure, water exchange cycle, and main flow path under different flow distribution ratios of the inlets are measured using the overall physical model of wind-driven flow in the entire Taihu Lake area. The flow distribution ratio corresponding to the minimum average water exchange cycle is the optimal flow distribution ratio F2 of the inlets.

[0063] Based on the determined optimal inlet combination F1 and the optimal inlet flow distribution ratio F2, and with the outlets of the Xingou River, Taipu River, Liangxi River and Zoumatang River flowing into the Grand Canal determined, all outlets are arranged and combined. Using the three-dimensional mathematical model of wind-driven flow in the entire Taihu Lake area, the hydraulic residence time of the Yangtze River water diverted into Taihu Lake is numerically simulated to calculate the average water exchange cycle of the lake area under each combination. The combination corresponding to the minimum average water exchange cycle is the optimal outlet combination F.

[0064] Based on the determined optimal inlet combination F1, optimal inlet flow distribution ratio F2, and optimal outlet combination F3, the average water exchange cycle of the lake area under different outlet flow distribution ratios was measured using the overall physical model of wind-driven flow in the entire Taihu Lake area. The flow distribution ratio corresponding to the minimum average water exchange cycle is the optimal outlet flow distribution ratio F4.

[0065] Specifically, such as Figure 3 The Taihu Lake aeolian flow overall physical model shown follows the gravity similarity criterion, with a horizontal scale of 1:500, a vertical scale of 1:10, a planar dimension of 140m × 140m, an average water depth of approximately 20cm, and a model height of 1.1m. The model simulates the Taihu Lake area, 23 rivers flowing into and out of the lake, and 49 lake islands. The Taihu Lake aeolian flow overall physical model includes five subsystems: a water circulation system, an aeolian system, a hydrodynamic monitoring and control system, a water environment monitoring system, and a real-time monitoring and transmission system. The model adopts a cross-sectional aeolian system to simulate the natural wind field, with a total of 28 air supply cross-sections arranged, with an adjacent cross-section spacing of 5m, a maximum wind speed of 18m / s, and adjustable wind speed. It can be used to conduct research on shallow lake hydrodynamic characteristics, pollutant migration and diffusion patterns, cyanobacterial bloom aggregation and dispersion characteristics, ecological dredging and siltation schemes, aquatic plant habitat restoration, optimized scheduling of water diversion and diversion projects, and algae suppression and control measures based on hydrodynamic factor improvements.

[0066] A physical model experiment was conducted based on the aforementioned overall physical model of the Taihu Lake wind-driven current flow area, including:

[0067] Water level changes were measured using a wave height meter;

[0068] The surface velocity within a 4 cm depth below the water surface was measured using a Large-Scale Surface Flow Field Measurement System (LSPIV). Specifically, for points within the coverage area of ​​the LSPIV, the velocity result at that point was directly taken as the surface water velocity result. In the processing of the planar circulation results, the velocity results of the surface water and the water within 4 cm below the surface were first statistically analyzed to obtain the vertical velocity results at different measuring points. Then, the vertical velocity results at each measuring point were averaged to obtain the planar velocity result at that measuring point. Figure 4 The flow field diagrams obtained using a large-scale surface flow field measurement system are presented;

[0069] The vertical flow velocity (e.g., 4 cm below the water surface to 2 cm above the riverbed bottom) was measured using an acoustic Doppler point current meter (ADV) and an underwater PIV current measurement system (UWPIV). Figure 5As shown in the figure), during the experiment, the flow velocity was measured at three points along the vertical line at the top, middle, and bottom of each flow velocity measuring point. The top flow velocity was measured approximately 4 cm below the water surface, the bottom flow velocity was measured 1 cm above the lakebed, and the middle flow velocity was measured at the midpoint between the top and bottom. The average of the flow velocities at the three locations was taken as the average flow velocity at the corresponding measuring point (e.g., ...). Figure 6 and Figure 7 (As shown in the figure); Based on the average flow velocity at different measuring points, the impact of water diversion on the hydrodynamic structure of the target lake area is obtained.

[0070] A planar laser-induced fluorescence (PLIF) system was used for real-time measurement and analysis of nitrogen and phosphorus pollutant concentration fields during water exchange cycles. This allowed for the tracking of pollutant diffusion and migration processes, as well as the mixing process between imported water and Taihu Lake water (e.g.,...). Figure 8 As shown in the figure, the water exchange cycle and water quality indicators are measured.

[0071] Specifically, based on the overall physical model of wind-driven flow in the entire Taihu Lake area, numerical simulations of the mixing process of Yangtze River water and Taihu Lake water under different wind fields and water diversion conditions were conducted. The changes in lake flow structure caused by different water diversion schemes were simulated and analyzed, especially the impact on the internal circulation structure of Meiliang Bay, Zhushan Bay, and Gonghu Bay. The effects of water diversion on the changes in nitrogen and phosphorus pollution load in Taihu Lake and its control on cyanobacterial blooms were studied.

[0072] Specifically, taking the average water exchange cycle of the three bays, Meiliang Bay, Gonghu Bay, and Zhushan Bay, as the optimization objective and the total nitrogen and phosphorus pollution load entering the lake as low, the study analyzed the impact of different water diversion schemes on the hydrodynamics, water level changes, and cyanobacterial bloom control effects of different lake areas in Taihu Lake through a combination of physical model experiments and numerical simulation of the hydraulic residence time of the Yangtze River water diversion into Taihu Lake. The study determined the optimal scheme for controlling cyanobacterial blooms in Taihu Lake with the greatest benefit and fastest water exchange among different combinations of water diversion routes. Figure 9 The impact of the new water diversion pattern of the "two inlets and three outlets" Taihu Lake water project group on the hydrodynamic characteristics of Zhushan Bay was presented using LSPIV, ADV and UWPIV measurements. It shows that the new water diversion pattern will significantly enhance the hydrodynamic intensity of Zhushan Bay and Gonghu Bay, reduce the water exchange cycle, and effectively suppress cyanobacterial blooms.

[0073] Figure 10 The migration and diffusion process of the water diverted into Taihu Lake by the "two inlets and three outlets" water project group was measured using a planar laser-induced fluorescence system (PLIF) under southeast wind and wind speed of 5 m / s. The Wangyu River water diffused from Gonghu Lake along the north bank to Meiliang Lake, which helped to push the cyanobacteria that were pushed to the west bank of Gonghu Bay during the southeast wind to the outside of the bay, thereby reducing the density of cyanobacteria and alleviating the algal bloom disaster. The water diversion from the Wangyu River into the lake can significantly improve the water quality of the water intake areas of Wuxi Xidong Water Plant and Wuxi Nanquan Water Plant.

[0074] Specifically, this study analyzes the water quality and quantity requirements for total nitrogen, total phosphorus, and ammonia nitrogen in controlling cyanobacterial blooms through water diversion and flow regulation. Based on this, it proposes suitable water diversion quantities for three different seasonal periods under typical hydrological years (high-water, normal-water, and low-water years): the spring period when cyanobacteria gain dominance, the summer period when cyanobacteria flourish, and the autumn / winter period when cyanobacteria decline. Based on the principles of biodynamic and hydrodynamic inhibition of cyanobacterial growth, the study analyzes the suitable water quality and water level requirements for inhibiting cyanobacteria under different seasonal conditions, and proposes suitable water diversion quantities for different seasons under typical hydrological years. It also analyzes the differences in hydrodynamic inhibition of cyanobacterial growth through water diversion and flow regulation in different seasons, and proposes seasonal water diversion recommendations. Table 1 shows the inflow and outflow rates (m³) of the Taihu Lake water engineering group's water diversion schemes for different seasons. 3 / s);

[0075] Table 1

[0076]

[0077] As shown in Table 1, the operation is mainly divided into three periods: autumn / winter (October to March of the following year), spring (April to June), and summer (July to September). According to the water diversion requirements in the "Taihu Lake Basin Water Allocation Scheme," the average water level of Taihu Lake is higher than the water diversion limit line during the summer period. At this time, flood control needs should be the primary consideration. The Wangyu River only considers drainage operation. During the spring and autumn / winter periods, the average water level of Taihu Lake fluctuates around the water diversion limit line. At this time, both water resource allocation and ecological water level requirements should be considered. The Wangyu River considers two operation modes: water diversion and drainage. The former operates from April to June during the cyanobacteria bloom period, with the goal of controlling cyanobacteria blooms and suppressing algal blooms. The latter operates from October to March of the following year during the non-cyanobacteria bloom period, with the goal of water resource allocation and water quality improvement.

[0078] This invention provides a comprehensive water engineering system for controlling cyanobacterial blooms in large shallow lakes, comprising: an inlet / outlet determination module, which determines the optimal inlet combination, the optimal flow distribution ratio of each inlet, the optimal outlet combination, and the optimal flow distribution ratio of each outlet based on a preset water diversion and diversion scheme; a hydrodynamic optimal scheme determination module, which calculates the average spatial distribution value of the lake area's water exchange cycle under each water diversion and diversion scheme based on the determined optimal inlet combination, the optimal flow distribution ratio of each inlet, the optimal outlet combination, and the optimal flow distribution ratio of each outlet, and selects the optimal water diversion and diversion scheme A based on hydrodynamic indicators; and a water quality optimal scheme determination module, which determines the optimal inlet combination, the optimal inlet combination, the optimal flow distribution ratio of each inlet, the optimal outlet combination, and the optimal flow distribution ratio of each outlet, and calculates the average spatial distribution value of the lake area's water exchange cycle under each water diversion and diversion scheme, and selects the optimal water diversion and diversion scheme A based on the average spatial distribution value of the lake area's water exchange cycle; and a water quality optimal scheme determination module, which determines the optimal inlet combination, the optimal inlet combination, the optimal inlet combination, the optimal flow distribution ratio of each outlet, and the optimal water diversion and diversion scheme A based on the determined optimal inlet combination; and a water quality optimal scheme determination module, which determines the optimal inlet combination, the optimal inlet combination, the optimal inlet combination, and the optimal water quality optimal scheme based on the determined optimal inlet combination. The optimal flow distribution ratios of each inlet and outlet, as well as the optimal flow distribution ratios of each outlet, are used to calculate the water quality improvement rate and compliance rate of the lake area under each water diversion scheme. Based on the water quality improvement rate and compliance rate, the optimal water diversion scheme B, with water quality indicators as the reference, is selected. In the comprehensive optimization module, based on the optimal water diversion scheme A with hydrodynamic indicators as the reference and the optimal water diversion scheme B with water quality indicators as the reference, combined with the overall physical model test of the wind-driven flow in the entire Taihu Lake area and the numerical simulation of the hydraulic residence time of the Yangtze River passenger water diverted into Taihu Lake by the three-dimensional mathematical model of the wind-driven flow in the entire Taihu Lake area, the optimal scheme for controlling cyanobacterial blooms in Taihu Lake water diversion and diversion with the greatest benefit and fastest water exchange is determined for different reference water diversion route combinations.

[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made by those skilled in the art within the scope of the technology disclosed in this invention, based on the technical solution and concept of the present invention, should be included within the protection scope of this invention. Therefore, the protection scope of this invention should be determined by the scope of the claims.

Claims

1. A comprehensive regulation method for water engineering clusters based on the prevention and control of cyanobacterial blooms in large shallow lakes, characterized in that, Includes the following steps: Step 1: Identify the large shallow lake to be studied and obtain a pre-set water diversion and drainage plan for the large shallow lake; Step 2: Determine the optimal inlet combination F1, the optimal flow distribution ratio F2 for each inlet, the optimal outlet combination F3, and the optimal flow distribution ratio F4 for each outlet of the large shallow lake. Step 3: With F1, F2, F3 and F4 fixed, use the three-dimensional mathematical model of wind-driven flow in the entire Taihu Lake area to calculate the spatial distribution value of the water exchange cycle in the lake area under each water diversion scheme. Based on the spatial distribution value of the water exchange cycle in the lake area, select the optimal water diversion scheme A with hydrodynamic indicators as the reference. Step 4: With F1, F2, F3 and F4 fixed, use the three-dimensional mathematical model of wind-driven flow in the entire Taihu Lake area to calculate the water quality improvement rate and compliance rate of the lake area under each water diversion scheme, and select the optimal water diversion scheme B based on water quality indicators. Step 5: Based on the determined optimal water diversion scheme A (referring to hydrodynamic indicators) and optimal water diversion scheme B (referring to water quality indicators), the optimal water diversion scheme for controlling cyanobacterial blooms is determined by combining the overall physical model test of the Taihu Lake wind-driven flow area and the three-dimensional mathematical model of the Taihu Lake wind-driven flow area. The optimization function objective is to minimize the average water exchange cycle and minimize the total nitrogen and phosphorus pollution load entering the lake.

2. The comprehensive regulation and control method for water engineering groups based on the prevention and control of cyanobacterial blooms in large shallow lakes according to claim 1, characterized in that, The method for determining the optimal inlet combination F1 is as follows: identify the existing lake inlets, arrange and combine all the lake inlets, and use the three-dimensional mathematical model of wind-driven flow in the whole Taihu Lake area to numerically simulate the hydraulic residence time to calculate the average water exchange cycle of the lake area under the same water diversion flow and different combinations. The combination corresponding to the minimum average water exchange cycle is taken as the optimal inlet combination F1. Given the optimal inlet combination F1, the water level, hydrodynamic structure, water exchange cycle, and main flow path under different flow distribution ratios of the inlets are measured using the overall physical model of wind-driven flow in the entire Taihu Lake area. The flow distribution ratio corresponding to the minimum average water exchange cycle is the optimal flow distribution ratio F2 of the inlets. Based on the determined optimal inlet combination F1 and the optimal inlet flow distribution ratio F2, and given that the existing lake outlets are determined, all the lake outlets are arranged and combined. The average water exchange cycle of the lake area under each combination is calculated by numerical simulation of the hydraulic residence time using the three-dimensional mathematical model of wind-driven flow in the entire Taihu Lake area. The combination corresponding to the minimum average water exchange cycle is the optimal outlet combination F3. Based on the determined optimal inlet combination F1, optimal inlet flow distribution ratio F2, and optimal outlet combination F3, the average water exchange cycle of the lake area under different outlet flow distribution ratios was measured using the overall physical model of wind-driven flow in the entire Taihu Lake area. The flow distribution ratio corresponding to the minimum average water exchange cycle is the optimal outlet flow distribution ratio F4.

3. The comprehensive regulation and control method for water engineering groups based on the prevention and control of cyanobacterial blooms in large shallow lakes according to claim 1, characterized in that, The three-dimensional mathematical model of wind-driven flow in the entire Taihu Lake area includes the governing equations of flow field motion, the numerical simulation equations of hydraulic residence time of Yangtze River water diverted into Taihu Lake, and the equations of pollutant concentration diffusion and migration. 1) Regarding the flow field motion law, based on the static pressure assumption and the Boussinesq eddy viscosity assumption, and introducing... Coordinate system: ， In the formula, For point The water level at that location; Water level; For point The distance of the riverbed relative to the reference surface. The total water depth, i.e. The range of coordinate variation is ; Applying the joint differentiation rule, the basic governing equations for the motion of wind-driven currents in a layered three-dimensional shallow lake are as follows: ， ， ， ， ， ， In the formula: They are divided into layers. Flow velocity in direction For layering directional flow velocity; The Coriolis force coefficient, The angular velocity of Earth's rotation. The local geographical latitude; The density of algae in water, The density is that of clean water at room temperature; It is the horizontal eddy viscosity coefficient. The vertical eddy viscosity coefficient; For bottom stress, , The drag coefficient, The flow velocity at the top of the bed; For water surface wind stress, , air density, The wind stress coefficient on the water surface The wind speed is located 10 meters above the water surface. Based on flow field simulation, the flow field distribution under different wind speeds is obtained, and the mainstream path under different wind fields is obtained. 2) The basic equation for the numerical simulation of the hydraulic residence time of Yangtze River passenger water diverted into Taihu Lake is: ， In the formula, For the concentration of the guest water, , , They are respectively the guest water in , , Diffusion coefficient in the direction of travel; Numerical simulation was used to predict and analyze the diffusion and migration process of the Yangtze River water diverted into Taihu Lake, calculate the hydraulic residence time of the Yangtze River water, and obtain the spatial distribution of the water exchange cycle. 3) The equation for the diffusion and migration of pollutant concentration is: , In the formula, For pollutant concentration, , , The pollutants are respectively in , , The diffusion coefficient in the direction of water diversion; by numerically calculating the pollutant concentration, the diffusion process of pollutants when water is diverted into Taihu Lake is simulated. The calculation area of ​​the three-dimensional mathematical model of wind-driven flow in the entire Taihu Lake area is divided into triangular unit meshes, with a total of 8,720 nodes and 16,170 units, and divided into 15 layers in the vertical direction; and the mesh is locally refined according to the calculation needs.

4. The comprehensive regulation and control method for water engineering groups based on the prevention and control of cyanobacterial blooms in large shallow lakes according to claim 1, characterized in that, The Taihu Lake whole-area wind-driven current overall physical model experiment refers to the use of the Taihu Lake whole-area wind-driven current overall physical model, employing a variety of experimental methods including wave height meters, large-scale surface flow field measurement systems, acoustic Doppler point velocity meters, and underwater PIV velocity measurement systems to measure hydrodynamic indicators, and using a planar laser-induced fluorescence system to measure water quality indicators; the hydrodynamic indicators include at least one of water level, hydrodynamic structure, water exchange cycle, and mainstream path; the water quality indicators include at least one of chemical oxygen demand, ammonia nitrogen, total phosphorus, and total nitrogen.

5. The comprehensive regulation and control method for water engineering groups based on the prevention and control of cyanobacterial blooms in large shallow lakes according to claim 4, characterized in that, Water level changes were measured using a wave height meter, surface velocity within 4 cm below the water surface was measured using a large-scale surface flow field measurement system, and vertical velocity at measuring points from 4 cm below the water surface to 2 cm above the riverbed bottom was measured using an acoustic Doppler point current meter and an underwater PIV velocity measurement system. Based on the measured velocity at different measuring points, the impact of water diversion on the hydrodynamic structure of the target lake area was obtained. A planar laser-induced fluorescence system was used to measure and analyze the concentration field of nitrogen and phosphorus pollutants in real time, enabling the tracking of the diffusion and migration process of pollutant concentrations, the mixing process of incoming water and target shallow lake water, and the measurement of water exchange cycle and water quality indicators.

6. The comprehensive regulation and control method for water engineering groups based on the prevention and control of cyanobacterial blooms in large shallow lakes according to claim 5, characterized in that, A holistic physical model experiment of wind-driven flow was conducted across the entire Taihu Lake area to demonstrate the mixing process of imported water and target shallow lake water under different wind speeds and water diversion flow rates. The experiment simulated and analyzed the changes in lake flow structure caused by different water diversion schemes, and studied the effects of water diversion on changes in nitrogen and phosphorus pollution loads and on the control of cyanobacterial blooms.

7. A comprehensive regulation method for water engineering groups based on the prevention and control of cyanobacterial blooms in large shallow lakes, as described in claim 6, is characterized in that... With the optimization objective of a short average water exchange cycle and a low total nitrogen and phosphorus pollution load entering the lake, this study analyzes the impact of different water diversion schemes on hydrodynamics, water level changes, and the control of cyanobacterial blooms in different lake areas through a combination of physical model experiments and numerical simulation of hydraulic residence time. The study determines the optimal water diversion scheme for controlling cyanobacterial blooms that maximizes benefits and achieves the fastest water exchange among different reference water diversion route combinations.

8. A comprehensive regulation method for water engineering groups based on the prevention and control of cyanobacterial blooms in large shallow lakes, as described in claim 7, is characterized in that... This study analyzes the water quality and quantity requirements for total nitrogen, total phosphorus, and ammonia nitrogen in controlling cyanobacterial blooms through water diversion and regulation. It proposes suitable water diversion quantities for three different seasonal periods under hydrological conditions, including typical high-water years, normal-water years, and low-water years: the spring period when cyanobacteria gain dominance, the summer period when cyanobacteria flourish, and the autumn / winter period when cyanobacteria decline. The study also analyzes the differences in hydrodynamic inhibition of cyanobacterial growth during water diversion and regulation in different seasons and proposes seasonal water diversion recommendations.

9. A comprehensive water engineering system for controlling cyanobacterial blooms in large shallow lakes, characterized in that: The method for comprehensive regulation of water conservancy projects for controlling cyanobacterial blooms in large shallow lakes, as described in any one of claims 1 to 8, includes: an inlet / outlet determination module, which determines the optimal combination of inlets, the optimal flow distribution ratio of each inlet, the optimal combination of outlets, and the optimal flow distribution ratio of each outlet based on a pre-set water diversion and diversion scheme; a hydrodynamic optimal scheme determination module, which calculates the average spatial distribution value of the lake area's water exchange cycle under each water diversion and diversion scheme based on the determined optimal combination of inlets, the optimal flow distribution ratio of each inlet, the optimal combination of outlets, and the optimal flow distribution ratio of each outlet, and selects the optimal water diversion and diversion scheme A based on hydrodynamic indicators according to the average spatial distribution value of the lake area's water exchange cycle; and a water quality optimal scheme determination module, which determines the optimal combination of inlets, the optimal flow distribution ratio of each inlet, the optimal combination of outlets, and the optimal flow distribution ratio of each outlet based on the determined optimal combination of inlets, the optimal flow distribution ratio of each inlet, and the optimal combination of outlets, and the optimal flow distribution ratio of each outlet, and then selects the optimal water diversion and diversion scheme A based on the hydrodynamic indicators; and a water quality optimal scheme determination module, which determines the optimal combination of inlets, the optimal combination of inlets, the optimal flow distribution ratio of each inlets, and the optimal water exchange cycle A based on the determined optimal combination of inlets, the optimal combination of inlets, and the optimal flow distribution ratio of each outlet, and then selects the optimal water diversion and diversion scheme A based on the determined optimal combination of inlets, the optimal combination of inlets, and the optimal combination of outlets, and the optimal combination of inlets ... The optimal combination of inlets, the optimal flow distribution ratio of each inlet, the optimal combination of outlets, and the optimal flow distribution ratio of each outlet are used to calculate the water quality improvement rate and compliance rate of the lake area under each water diversion scheme. Based on the water quality improvement rate and compliance rate, the optimal water diversion scheme B, with water quality indicators as the reference, is selected. In the comprehensive optimization module, based on the optimal water diversion scheme A with hydrodynamic indicators as the reference and the optimal water diversion scheme B with water quality indicators as the reference, combined with the overall physical model test of the wind-driven flow in the entire Taihu Lake area and the numerical simulation of the hydraulic residence time of the Yangtze River passenger water diverted into Taihu Lake by the three-dimensional mathematical model of the wind-driven flow in the entire Taihu Lake area, the optimal scheme for controlling cyanobacterial blooms with the greatest benefit and fastest water exchange of different reference water diversion route combinations is determined.

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