Ecological flow calculation method and device for plain river network area, medium and equipment

Abstract

The invention discloses a plain river network area ecological flow calculation method and device, a medium and equipment, and relates to the technical field of river network ecological environments. The method comprises the following steps: determining a non-flood-season ecological water level, a flood-season ecological water level and a main-flood-season ecological water level of a river network, and further determining a water level index of the river network; determining a first water depth of the river network according to the suitable water depth of the multiple aquatic plants in the river network, determining a second water depth of the river network according to the suitable water depth of the multiple fishes in the river network, and further determining a water depth index; determining a first water flow velocity of the river network according to an algae water flow velocity statistical model or a chlorophyll a water flow velocity statistical model, determining a second water flow velocity of the river network according to stimulated water flow velocities required by oviposition behaviors of various fishes in a breeding season, and further determining a water flow velocity index of the river network; the ecological flow of the river network is adjusted according to the incidence relation among the water level index, the water depth index and the water flow speed index. Through the scheme, the ecological flow of the plain river network area can be accurately calculated.

Description

Technical Field

[0001] This invention relates to the technical field of river network ecological environment, and in particular to a method, apparatus, medium and equipment for calculating ecological flow in plain river network areas. Background Technology

[0002] Ecological flow refers to the water flow with specific quantity and quality characteristics that is retained to maintain and protect the aquatic ecological functions and biodiversity in natural ecosystems. It regulates and maintains the flow of water according to the needs of a specific ecosystem and the survival requirements of the biological community. Therefore, calculating the ecological flow of a specific region plays a crucial role in ensuring the biodiversity, habitat integrity, and normal operation of ecological processes within that region's ecosystem.

[0003] Existing methods for calculating ecological flow mainly employ hydrological methods, habitat simulation methods, and hydraulic methods. Hydrological methods primarily utilize causal analysis, mathematical statistics, geographic synthesis, empirical formulas, and heat balance methods. Habitat simulation methods mainly employ flow-time curve methods, methods combining hydrodynamic numerical simulation with habitat models, and system synergy theory methods. Hydraulic methods primarily utilize data analysis, variation range methods, functional analysis, and hydraulic habitat models to calculate ecological flow in river networks.

[0004] However, existing technologies calculate the ecological flow of river networks in isolation based on hydrological methods, habitat simulation methods, and hydraulic methods, and cannot correlate the relevant indicators of ecological flow calculated by hydrological methods, habitat simulation methods, and hydraulic methods respectively, thus failing to accurately obtain the ecological flow of river networks. Summary of the Invention

[0005] Therefore, it is necessary to provide a method, device, medium, and equipment for calculating ecological flow in plain river network areas, addressing the technical problem that existing technologies cannot accurately obtain the ecological flow of river networks.

[0006] The present invention adopts the following technical solution: In a first aspect, the present invention provides a method for calculating ecological flow in plain river network areas, the method comprising: The minimum ecological water level of the river network is determined and used as the non-flood season ecological water level of the river network; the flood season ecological water level and the main flood season ecological water level of the river network are determined based on the typical annual water level change curve or ecological water level curve of the river network; the water level index of the river network is determined based on the non-flood season ecological water level, the flood season ecological water level, and the main flood season ecological water level. The first water depth of the river network is determined based on the minimum water depth required by various plants in the river network, and the second water depth of the river network is determined based on the minimum water depth required by various fish species in the river network. The water depth index of the river network is determined based on the first water depth and the second water depth. The first water flow velocity of the river network is determined based on a pre-constructed statistical model of algal water flow velocity or a statistical model of chlorophyll a water flow velocity. The second water flow velocity of the river network is determined based on the stimulation water flow velocity required for the spawning behavior of various fish species in the river network during the breeding season. The water flow velocity index of the river network is determined based on the first water flow velocity and the second water flow velocity. The ecological flow of the river network is adjusted based on the correlation between the water level index, water depth index, and flow velocity index of the river network.

[0007] Furthermore, the various plants include submerged plants, phytoplankton, floating-leaved plants, and emergent plants, and the various fish include black carp, grass carp, silver carp, and bighead carp.

[0008] Furthermore, the determination of the minimum ecological water level of the river network is obtained by calculating the water level data of the river network using the 90% guarantee rate method, the 7Q10 method, and the driest month average method. The calculation expression for the 90% guarantee rate method is as follows: ; in, f(x Γ(α) is the probability density function of type P-III, and Γ(α) is the gamma function. α , β , α 0 For parameters , x For water level variables, This represents the average water level. It is the coefficient of variation, used to measure the amplitude of water level fluctuations. It is the skewness coefficient, used to describe water level distribution.

[0009] Furthermore, the calculation expression for the average value of the driest month is as follows: ; in, This is the average water level for the driest month in many years. The measured water level for the driest month of each year is given, where m and n are the year numbers.

[0010] Furthermore, the ecological flow of the river network is adjusted based on the correlation between the river network's water level index, water depth index, and flow velocity index, specifically including: An ecological flow adjustment coupled model for the river network is constructed based on the fundamental equations of hydraulics and the Saint-Venant equations. Using the water level, water depth, and flow velocity of the river network as targets, the real-time measured water level, water depth, and flow velocity of the river network are used as initial values ​​and input into the ecological flow adjustment coupling model for iteration. The ecological flow of the river network is adjusted according to the iteration results.

[0011] Secondly, the present invention provides an ecological flow calculation device for plain river network areas, comprising: The water level calculation module is used to determine the minimum ecological water level of the river network, and to use the minimum ecological water level as the non-flood season ecological water level of the river network; based on the annual water level change curve or ecological water level curve of the typical river network, it determines the flood season ecological water level and the main flood season ecological water level of the river network; and it determines the water level index of the river network based on the non-flood season ecological water level, the flood season ecological water level, and the main flood season ecological water level. The water depth calculation module is used to determine the first water depth of the river network based on the minimum water depth required by various plants in the river network, determine the second water depth of the river network based on the minimum water depth required by various fish in the river network, and determine the water depth index of the river network based on the first water depth and the second water depth. The flow velocity calculation module is used to determine the first flow velocity of the river network based on a pre-constructed statistical model of algal flow velocity or chlorophyll a flow velocity, determine the second flow velocity of the river network based on the stimulation flow velocity required for the spawning behavior of various fish species in the river network during the breeding season, and determine the flow velocity index of the river network based on the first flow velocity and the second flow velocity. The ecological flow determination module is used to adjust the ecological flow of the river network based on the correlation between the river network's water level index, water depth index, and water flow velocity index.

[0012] This invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the method for calculating ecological flow in plain river network areas.

[0013] The present invention provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the method for calculating ecological flow in plain river network areas.

[0014] The at least one technical solution adopted in this invention can achieve the following beneficial effects: First, this invention determines the minimum ecological water level of the river network, and uses this minimum ecological water level as the non-flood season ecological water level of the river network; based on the typical annual water level change curve or ecological water level curve of the river network, it determines the flood season ecological water level and the main flood season ecological water level of the river network; based on the non-flood season ecological water level, the flood season ecological water level, and the main flood season ecological water level, it determines the water level index of the river network, which can combine the characteristics of the ecological water level of the river network in different flood seasons to obtain a more accurate water level index. Then, based on the minimum water depth required by various plants in the river network, it determines the first water depth of the river network; based on the minimum water depth required by various fish species in the river network, it determines the second water depth of the river network; based on the first and second water depths, it determines the water depth index of the river network, which can combine the minimum water depth required by aquatic plants and the minimum water depth required by fish to comprehensively determine the water depth index that meets the needs of the vast majority of animals or plants in the river network, enabling aquatic plants in the river network to grow healthily and improving their reproductive capacity, thereby indirectly improving the plant's water purification capacity and ecological restoration effect. Then, based on a pre-constructed statistical model of algal flow velocity or chlorophyll a flow velocity, the first flow velocity of the river network is determined. The second flow velocity is determined based on the stimulus flow velocity required for the spawning behavior of various fish species during the breeding season. Based on the first and second flow velocities, the flow velocity index of the river network is determined, which accelerates algal growth, prolongs algal growth cycles, promotes algal cell energy metabolism and nutrient absorption, improves algal cell morphology, and enhances the reproductive capacity of fish in the river network. Finally, the ecological flow of the river network is adjusted based on the correlation between the river network's water level, water depth, and flow velocity indices. The above scheme enables the determination of ecological flow in plain river networks from three perspectives: water level during different flood seasons, water depth and flow velocity that meet the needs of healthy growth and reproduction of animals and plants in the river network. It also enables the correlation of relevant indicators of ecological flow in river networks calculated by hydrological methods, habitat simulation methods and hydraulic methods, respectively, thereby obtaining accurate ecological flow of plain river networks. Furthermore, the ecological flow of river networks can be adjusted according to the correlation between the obtained water level, water depth and flow velocity indicators, so as to accurately adjust the ecological flow of river networks to a level suitable for the survival of various organisms in the river network. Attached Figure Description

[0015] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0016] Figure 1 A schematic diagram of the process for calculating ecological flow in plain river network areas provided by this invention; Figure 2This invention provides an overall framework diagram for a method of calculating ecological flow in plain river network areas; Figure 3 A schematic diagram of urban river restoration stress and restoration function flow provided by the present invention; Figure 4 A schematic diagram of an ecological flow calculation device for a plain river network area provided by the present invention; Figure 5 A schematic diagram of a computer device for implementing a method for calculating ecological flow in a plain river network area, provided by the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention and corresponding drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0018] The server mentioned in this invention can be a server set up on a business platform, or a device such as a desktop computer or laptop computer capable of executing the solution of this invention. For ease of explanation, the following description focuses solely on the server as the executing entity. The technical solutions provided by various embodiments of this invention are described in detail below with reference to the accompanying drawings.

[0019] refer to Figure 1 The method for calculating ecological flow in plain river network areas in this invention specifically includes the following steps: S10: Determine the minimum ecological water level of the river network and use it as the non-flood season ecological water level of the river network; determine the flood season ecological water level and the main flood season ecological water level of the river network based on the typical annual water level change curve or ecological water level curve of the river network; determine the water level index of the river network based on the non-flood season ecological water level, the flood season ecological water level and the main flood season ecological water level.

[0020] In this embodiment, the hydrological situation of most urban rivers has been fundamentally altered by urbanization and water conservancy projects. Hydrological changes, along with other factors such as rising water temperature and deteriorating water quality, have exacerbated the degradation of river ecosystems. Since the restoration of river hydrology essentially depends on the ecological restoration of the entire watershed, restoring the hydrological situation to its pre-urbanization state is no longer realistic in watersheds with high development levels and severe competition between urban and river ecological water use. Therefore, efforts should be made to restore the river's "functional flows"—flows that maintain key geomorphological, ecological, or biogeochemical processes—to partially restore the river's ecological functions. Thus, it is necessary to establish a coupled model based on existing hydrological and ecological data to determine key hydrological and hydraulic parameters and hydrological-ecological response relationships, and to simulate the relationship between various flow scenarios and the probability of the occurrence of protected species. Based on social and aquatic ecosystem needs, the flow, frequency, duration, timing, and rate of change of each key hydrological event should be integrated according to sub-river sections and seasons to suggest variation ranges.

[0021] refer to Figure 3 This demonstrates the resilience and restorative flow of urban rivers—flows that sustain key geomorphological, ecological, or biogeochemical processes. Figure 3 The curves showing the changes in natural flow, post-development flow, and functional flow of urban rivers at different time periods are presented respectively.

[0022] In this embodiment, the river network refers to one or more rivers in a plain river network; the main flood season is from June to August; the flood season is from April, May, September, and October; and the non-flood season is from January, February, March, November, and December. (Reference) Figure 2 The minimum ecological water level of the river network is calculated using hydrological methods, including the 90% guarantee rate method, the 7Q10 method, and the average value of the driest month.

[0023] Specifically, the calculation formula for the 90% guarantee rate method is as follows: ; in, f(x Γ(α) is the probability density function of type P-III, and Γ(α) is the gamma function. α , β , α 0 For parameters , x Water level variable (unit: meters) This represents the average water level. It is the coefficient of variation, used to measure the amplitude of water level fluctuations. It is the skewness coefficient, used to describe water level distribution.

[0024] Specifically, the 7Q10 method refers to using the 90% guarantee rate method to determine the average flow rate over the seven consecutive dryest days.

[0025] Specifically, the calculation expression for the driest month average method is as follows: ; in, This is the average water level for the driest month in many years. For the i The measured water level of the driest month of the year, where n is the number of years.

[0026] S20: Determine the first water depth of the river network based on the minimum water depth required by various plants in the river network, determine the second water depth of the river network based on the minimum water depth required by various fish species in the river network, and determine the water depth index of the river network based on the first and second water depths.

[0027] In this embodiment, reference Figure 2 The water depth of the river network was calculated using habitat simulation methods, which include the minimum water depth method for aquatic plants and the minimum water depth method for fish. The first water depth of the river network was determined based on the minimum water depth required by various plants in the network, i.e., the minimum water depth method for aquatic plants was used to determine the first water depth of the river network during different flood seasons. The second water depth of the river network was determined based on the minimum water depth required by various fish species in the network, i.e., the minimum water depth method for fish was used to calculate the second water depth of the river network during different flood seasons.

[0028] In this embodiment, a variety of plants include submerged plants, phytoplankton, floating-leaved plants, and emergent plants, and a variety of fish include black carp, grass carp, silver carp, and bighead carp.

[0029] In this embodiment, the water level of natural water bodies, especially small enclosed water areas, is often affected by rainfall and fluctuates. Both excessively high and low water levels can negatively impact the growth and development of aquatic plants. Water depth indirectly affects the water purification capacity and ecological restoration effects of aquatic plants by influencing their growth, physiological condition, and reproductive capacity. Suitable water depths for some aquatic plants are shown in Table 1. Submerged plants generally adapt to water depths of 1m and above; the suitable water depth for floating-leaved plants varies depending on the plant, but most adapt to shallower waters; emergent plants adapt to shallower water depths and can even survive without water, but Phragmites communis, Nelumbo nucifera, Carex esculenta, and Lythrum salicaria can adapt to depths exceeding 1m. In landscape water bodies, the minimum water depth required for aquatic plants is 0.3m.

[0030] Table 1. Common Aquatic Plants and Suitable Water Depths in Landscape Water Bodies of the Eastern Plain River Network Area Water levels correspond one-to-one with the living space of organisms; therefore, the minimum ecological water level can be determined by the living space requirements of various organisms within the river channel. Lake plants, fish, and other organisms all require a minimum ecological water level to prevent severe decline in their respective communities. The maximum value of these minimum ecological water levels is the minimum ecological water level of the lake.

[0031] Generally, fish are the apex community in aquatic ecosystems, playing a crucial role in the presence and abundance of other groups; therefore, they are used as indicator species. If the minimum ecological water level meets the needs of fish, the minimum needs of other organisms can be considered guaranteed. The minimum water depth required by fish is 2-3 times their body length. Based on measured data, the maximum body length of all fish species in the area does not exceed 0.4m; calculated at 3 times, this is 1.2m. Therefore, the formula for calculating the ecological water level of this area using the minimum water depth required by fish is:

[0032] ; In the formula: H This is the lowest ecological water level. H 0 The elevation of the lake (river) bottom is given in meters.

[0033] Preferably, in this embodiment, when determining the minimum water depth required by fish, in addition to considering water level, water depth and flow velocity, water quality parameters of the river network (such as dissolved oxygen content, nitrogen and phosphorus content), bottom conditions (such as soil, sand, clay, etc.) and riparian vegetation information can also be combined.

[0034] The above factors affect the survival and reproduction of fish, specifically: In a river network with a silty bottom and eutrophic water quality, the silty bottom consumes a large amount of oxygen, leading to a decrease in dissolved oxygen levels. Simultaneously, eutrophication triggers a massive algal bloom, further depleting oxygen in the water. In this situation, fish may choose deeper areas with relatively stable currents to escape the low-oxygen and highly polluted environment. Conversely, if a section of the river network has clear water and a bottom of pebbles or gravel, providing a good habitat and foraging environment for fish, then fish may prefer to inhabit that area and be less demanding in terms of water depth.

[0035] Therefore, after calculating the ecological water level of the area using the minimum water depth required by fish, by combining water quality parameters, bottom sediment conditions and riparian vegetation information to improve or decrease the adaptability of the ecological water level of the area, a more suitable ecological water level for the area can be obtained.

[0036] This embodiment determines the first water depth based on the minimum water depth required by various plants in the river network, and the second water depth based on the minimum water depth required by various fish species in the river network. This allows for the determination of the minimum water depths suitable for aquatic plants, various fish species, and other animals in the river network, thereby meeting the requirements for the survival and development of various organisms in the river network and indirectly improving the self-repair capacity of the river network's ecological environment.

[0037] S30: Determine the first water flow velocity of the river network based on the pre-constructed statistical model of algal water flow velocity or chlorophyll a water flow velocity, determine the second water flow velocity of the river network based on the stimulation water flow velocity required for the spawning behavior of various fish species in the river network during the breeding season, and determine the water flow velocity index of the river network based on the first water flow velocity and the second water flow velocity.

[0038] In this embodiment, reference Figure 2 The flow velocity of the river network is calculated using hydraulic methods, including algal habitat methods and fish habitat methods. The first flow velocity of the river network is determined based on a pre-constructed statistical model of algal flow velocity or chlorophyll a flow velocity, i.e., the first flow velocity of the river network during different flood seasons is determined using the algal habitat method. The second flow velocity of the river network is determined based on the stimulus flow velocity required for the spawning behavior of various fish species during the breeding season, i.e., the second flow velocity of the river network during different flood seasons is determined using the fish habitat method.

[0039] Specifically, the steps for constructing a statistical model of algal flow velocity or a statistical model of chlorophyll a flow velocity are as follows: Step 1: Data Collection and Processing: Collect algal growth data for the river network and surrounding areas, including algal species, quantities, and distribution in different seasons and river sections. Record synchronous water flow velocity data, covering the magnitude, direction, and changes in flow velocity at various locations within the river network, accurate to different depths and time points. Collect other environmental data related to algal growth, such as water temperature, nutrient concentration (nitrogen, phosphorus, etc.), light intensity, and dissolved oxygen content. This data can be obtained through field monitoring, historical data review, and relevant research materials.

[0040] Step 2, Data Preprocessing: Clean the collected raw data to remove outliers and erroneous data. For missing data, imputation is performed using mean imputation, interpolation, or machine learning-based missing value prediction algorithms, depending on the data characteristics and distribution. Data from different sources and organizations are standardized to unify units and formats, ensuring data comparability.

[0041] Step 3, Model selection and construction, including but not limited to: using a linear regression model to establish a linear equation between algal or chlorophyll a concentration and flow rate, or utilizing the powerful nonlinear fitting capabilities of neural networks (such as multilayer perceptrons, convolutional neural networks, etc.) to construct a complex relationship model between algal or chlorophyll a and flow rate and other environmental factors.

[0042] Step 4, Model Training and Optimization: Divide the preprocessed data into training and test sets according to a certain ratio (70% training set and 30% test set in this embodiment). Use the training set data to train the selected model, adjusting the model parameters to enable the model to fit the data well. Evaluate the model's performance using methods such as cross-validation, and select the optimal combination of model parameters. Utilize algorithms such as grid search and random search to find the optimal model parameters in the parameter space, improving the model's accuracy and generalization ability.

[0043] Step 5: Model Evaluation and Validation: Select appropriate evaluation metrics, such as mean squared error (MSE), root mean square error (RMSE), mean absolute error (MAE), and coefficient of determination (R²), to evaluate the model's predictive accuracy. Input test set data into the trained model, calculate the evaluation metric values, and determine the model's performance. Employ multiple validation methods, such as independent validation set validation and cross-validation, to ensure the model's reliability and generalization ability.

[0044] In this embodiment, hydrodynamic conditions not only directly affect algal growth but also indirectly influence algal reproduction by altering the redistribution of nutrients, carbon dioxide, and light in the water. Due to environmental factors such as eutrophication and heat waves, algal blooms frequently occur in July and August, causing problems such as loss of aquatic biodiversity, decline in food chain quality, and decreased water transparency. Compared to still water, a moderate water flow velocity of 0.30 m / s increases algal growth rate, prolongs algal growth cycle, promotes algal cell energy metabolism and nutrient absorption, and improves cell morphology. At water flow velocities of 0.06 m / s, 0.10 m / s, and 0.15 m / s, cyanobacteria shift towards green algae becoming the dominant species. At a water flow velocity of 0.30 m / s, green algae and diatoms become the dominant species, but their numbers are fewer than those of the dominant algal species in still water. Higher water flow velocities result in lower chlorophyll a concentrations, and since chlorophyll a is a necessary factor for algal growth, the algae-suppressing water flow velocity should not be lower than 0.30 m / s.

[0045] Fish spawning and reproduction require sufficient hydrodynamic conditions. The habitat quality of spawning grounds for the four major Chinese freshwater fish (black carp, grass carp, silver carp, and bighead carp) during their breeding season (May-August) directly impacts the overall fish resources of the entire cross-section. During the breeding season, the spawning behavior of these four species typically requires a certain water flow velocity and depth. According to various fish ecology studies, the optimal water flow velocity for spawning in these four species is 0.8 m / s-1.3 m / s, with a maximum velocity of 3.0 m / s. Drifting fish eggs need to remain suspended in the water for a certain period to hatch into viable larvae. Water flow velocities below 0.25 m / s will cause the eggs to sink and die, reducing the number of larvae. 0.25 m / s is also a suitable minimum water flow velocity to stimulate spawning; excessively high or low flow velocities will reduce spawning suitability.

[0046] This embodiment calculates the first water flow velocity of the river network using the algae habitat method and the second water flow velocity using the fish habitat method. This allows us to obtain the water flow velocity suitable for algae growth and reproduction and the second water flow velocity suitable for fish growth and reproduction in the river network. By combining the first and second water flow velocities, we can obtain the water flow velocity suitable for algae and fish growth and reproduction in the river network, thereby improving the self-repair capability of the river network's ecological environment.

[0047] S40: Adjust the ecological flow of the river network based on the correlation between the river network's water level index, water depth index, and water flow velocity index.

[0048] In this embodiment, after obtaining the water level, water depth, and flow velocity indices of the river network, the ecological flow of the river network is adjusted based on the interrelationships between water level, water depth, and flow velocity. Specifically:

[0049] I. Relationship between water level and water depth: Water level is the primary determinant of water depth. At the same cross-section, a rise in water level directly leads to an increase in water depth, and vice versa. For example, during the main flood season, if the water level rises from 0.69m to 0.80m (in the Jiashan demonstration area), and the riverbed elevation remains unchanged, the water depth will increase by 0.11m accordingly. Water depth also influences water level: changes in water depth can indirectly affect water level dynamics. For instance, an increase in water depth may alter the water volume, thus affecting the rate of rise and fall in water level (e.g., a rapid increase in water depth during flood season may lead to a faster rate of water level rise).

[0050] 0. Relationship between water level and water flow velocity: Dynamically related to water level difference driving flow velocity: The main driving force of water flow velocity is the water level difference (hydraulic gradient). According to Bernoulli's equation, the greater the water level difference, the more potential energy of the water flow is converted into kinetic energy, and the faster the flow velocity. For example, when the water level difference between the upstream and downstream of a river increases, the flow velocity will increase accordingly. Formula for the influence of water level on flow velocity: In uniform flow in an open channel, the flow velocity can be expressed by Manning's formula. When the water level difference increases, the flow velocity increases accordingly.

[0051] In real-world scenarios, the performance differs between the flood season and the non-flood season: During the main flood season, the water level is higher, and the water level difference between upstream and downstream may increase, leading to faster flow velocity (e.g., the flow velocity in Jiashan during the main flood season is ≥0.30m / s); during the non-flood season, the water level is lower, the water level difference is smaller, and the flow velocity may decrease (there is no mandatory requirement for flow velocity during the non-flood season).

[0052] 1. The relationship between water depth and water flow velocity: 1. The Influence of Water Depth on Flow Velocity in Hydraulics: Under constant flow conditions, an increase in water depth leads to a larger cross-sectional area, and according to the continuity equation, the flow velocity will decrease accordingly. For example, when the flow rate remains constant, if the water depth increases from 0.8m to 1.2m, the cross-sectional area expands, and the flow velocity may decrease from 0.30m / s to 0.20m / s (adjustments need to be made based on the river channel shape). Feedback of Flow Velocity on Water Depth: Changes in flow velocity can affect riverbed scouring and sedimentation, thus altering the water depth. For example, high flow velocities (such as during floods) may scour the riverbed, leading to an increase in water depth; low flow velocities may induce sedimentation, reducing water depth.

[0053] 2. The trade-off between algae control and fish habitat in ecological scenarios: Algae suppression requires a flow velocity of ≥0.30m / s (hydraulic method), but high flow velocity may lead to a decrease in water depth (when the flow rate is constant); fish spawning requires a flow velocity of ≥0.25m / s and a water depth of ≥1.2m. The two requirements need to be balanced through flow regulation (such as meeting the requirements of a flow velocity of 0.30m / s and a water depth of 1.20m during the main flood season).

[0054] IV. The Synergistic Effect of the Three in Ecological Flow Management: 1. Coupling Relationships under Ecological Objectives: Coordination between Water Level and Depth: Water level determines the baseline for water depth, which directly affects the living space of aquatic organisms. For example, in the Jiashan area, the water level during the non-flood season is ≥0.57m. If the riverbed elevation is -0.63m, the water depth is 0.57 - (-0.63) = 1.20m, meeting the minimum water depth requirement for fish. Coordination between Flow Velocity and Water Depth: Flow velocity affects water exchange and ecological processes (such as algae control and fish spawning), while water depth affects the magnitude of the flow velocity. For example, during the main flood season, by regulating the flow rate, maintaining a flow velocity of 0.30m / s at a water depth of 1.20m both inhibits algae growth and meets the spawning stimulation requirements of fish.

[0055] 2. Management Strategy Examples: Flood Season Regulation: Increase water level and depth through reservoir scheduling, and simultaneously increase flow velocity using the water level difference (e.g., water level 0.80m, water depth 1.20m, flow velocity 0.30m / s during the main flood season) to achieve the dual ecological goals of "water depth and flow velocity"; Non-Flood Season Protection: Maintain water level ≥0.57m and ensure water depth ≥1.20m (assuming riverbed elevation ≤-0.63m). Although there is no mandatory requirement for flow velocity, the risk of algal blooms caused by excessively low flow velocities must be avoided.

[0056] For example, Table 2 shows the calculation results of the ecological flow index of the Jiashan demonstration area according to the scheme of this embodiment, and Table 3 shows the suggested control requirements for the ecological flow index of the Jiashan demonstration area.

[0057] Table 2. Calculation results of ecological flow by three methods for sub-indicators in Jiashan Demonstration Area Table 3. Recommended Control Requirements for Ecological Flow in the Jiashan Demonstration Area based on Figure 1This method for calculating ecological flow in a plain river network region first determines the minimum ecological water level of the river network, which is then used as the non-flood season ecological water level. Based on the annual water level variation curve or ecological water level curve of a typical river network, the flood season ecological water level and the main flood season ecological water level are determined. Water level indicators for the river network are then determined based on these three levels, combining the characteristics of the ecological water level during different flood seasons to obtain more accurate indicators. Next, the first water depth of the river network is determined based on the minimum water depth required by various plants, and the second water depth is determined based on the minimum water depth required by various fish species. Water depth indicators are then determined based on the first and second depths, combining the minimum water depths required by aquatic plants and fish to comprehensively determine water depth indicators that meet the needs of the vast majority of animals and plants in the river network. This ensures the healthy growth of aquatic plants and improves their reproductive capacity, thereby indirectly enhancing the plant's water purification capacity and ecological restoration effect. Then, based on a pre-constructed statistical model of algal flow velocity or chlorophyll a flow velocity, the first flow velocity of the river network is determined. The second flow velocity is determined based on the stimulus flow velocity required for the spawning behavior of various fish species during the breeding season. Based on the first and second flow velocities, the flow velocity index of the river network is determined, which accelerates algal growth, prolongs algal growth cycles, promotes algal cell energy metabolism and nutrient absorption, improves algal cell morphology, and enhances the reproductive capacity of fish in the river network. Finally, the ecological flow of the river network is adjusted based on the correlation between the river network's water level, water depth, and flow velocity indices. The above scheme enables the determination of ecological flow in plain river networks from three perspectives: water level during different flood seasons, water depth and flow velocity that meet the needs of healthy growth and reproduction of animals and plants in the river network. It also enables the correlation of relevant indicators of ecological flow in river networks calculated by hydrological methods, habitat simulation methods and hydraulic methods, respectively, thereby obtaining accurate ecological flow of plain river networks. Furthermore, the ecological flow of river networks can be adjusted according to the correlation between the obtained water level, water depth and flow velocity indicators, so as to accurately adjust the ecological flow of river networks to a level suitable for the survival of various organisms in the river network.

[0058] When applying the ecological flow calculation method for plain river network areas provided by this invention, it is not necessary to rely on... Figure 1 The steps shown are executed in sequence. The specific execution order of each step can be determined as needed, and this invention does not impose any restrictions on it.

[0059] In one or more embodiments of the present invention, the ecological flow of the river network is adjusted according to the correlation between the river network's water level index, water depth index, and flow velocity index, specifically including: A coupled model for ecological flow adjustment in river networks is constructed based on the fundamental equations of hydraulics and the Saint-Venant equations.

[0060] Using the water level, water depth, and flow velocity of the river network as targets, the real-time measured water level, water depth, and flow velocity of the river network are used as initial values ​​to input into the ecological flow adjustment coupling model for iteration. The ecological flow of the river network is then adjusted based on the iteration results.

[0061] Specifically, the construction steps of the ecological flow adjustment coupling model are as follows: I. Determine the core relationship between water level, water depth, and water flow velocity.

[0062] Water flow velocity (V) and water depth (h): Chezy formula: V=C In a rectangular river channel, the hydraulic radius R ≈ h, therefore V ∝ Roughness factor n affects the Chezy coefficient C= R 1 / 6 .

[0063] Water depth and water level (Z): h = Z − Z b Riverbed elevation Z b When fixed, the water level Z directly determines the water depth h.

[0064] Flow rate (Q) and water velocity: Q=V A, the cross-sectional area of ​​the water passage is A=B h (B is the width of the river).

[0065] Second, the water level, water depth and flow velocity of the river network are taken as targets (i.e., the ecological flow control requirements of the Jiashan demonstration area as determined in Table 3 are taken as targets).

[0066] III. Constructing a coupling model.

[0067] (1) Saint-Venant's equations (one-dimensional unsteady flow): Continuity equation: + =q; Momentum equation: + ( )+gA =gA( ); Among them, friction slope Nengpo ΔZ / L.

[0068] (2) Embedding of ecological constraints Construct the objective function: min{w1(h min -h) 2 +w2(V min-V) 2 +w3(Z min -Z) 2}; Where w1=0.4, w2=0.3, w3=0.3 (weights), h min =1.2m, V min and Z min Values ​​are taken according to a period.

[0069] Iterative optimization algorithm: Input the initial flow rate Q0 and calculate Z, h, and V.

[0070] Compare the calculated Z, h, and V with the comparative ecological thresholds (i.e., the recommended ecological flow control requirements for the Jiashan demonstration area as determined in Table 3). If the ecological thresholds are not met, adjust the flow rate: Q k+1 =Q k +K (threshold − measured value); K is taken from 0.1 to 0.5, until the error is less than 5%.

[0071] Specifically, the following are specific implementation examples for determining the ecological flow of river networks (main flood season): 1. Given that the river width B = 20m and the riverbed elevation Z... b =−0.3m, river section length L=500m, water level difference ΔZ=0.2m, roughness coefficient n=0.025.

[0072] 2. Calculation process: Initial flow rate assumption: Q0 = 10m 3 / s, cross-sectional area of ​​water passage A0=B h0=20h0, flow velocity V0=Q0 / A0=10 / (20h0)=0.5 / h0.

[0073] Hydraulic correlation calculations: Energy slope J = ΔZ / L = 0.2 / 500 = 0.0004, Chezy coefficient .

[0074] Depend on Substituting, we get: = Solving for h0, we get h0 ≈ 1.0 m, then the water level Z = h0 + Z b =0.7m, flow velocity V0=0.5 / 1.0=0.5m / s.

[0075] Ecological constraint verification: water depth 1.0m < 1.2m, water level 0.7m < 0.8m. If the above targets are not met, adjustments are required.

[0076] Iterative flow adjustment: Target water depth h = 1.2m, then water level Z = 1.2 − 0.3 = 0.9m, and cross-sectional area A = 20 × 1.2 = 24m². 2 .

[0077] From V=C =40×1.21 / 6× ≈0.32m / s (satisfying V≥0.3m / s).

[0078] Ecological flow Q=V A = 0.32 × 24 = 7.68m 3 / s. Since the initial Q0 = 10m 3 When the water depth is insufficient at a certain value, it needs to be iterated according to the objective function until Q=7.68m. 3 / s, at which point all three indicators meet the standard.

[0079] The adjusted main flood season flow rate Q = 7.68 m³ 3 At a flow rate of / s: water level Z=0.9m≥0.8m, water depth h=1.2m, flow velocity V=0.32m / s≥0.3m / s, which fully meets the ecological threshold.

[0080] The above describes a method for calculating ecological flow in plain river network areas, provided by one or more embodiments of the present invention. Based on the same idea, the present invention also provides a corresponding device for calculating ecological flow in plain river network areas, such as... Figure 4 As shown, it includes: The water level calculation module is used to determine the minimum ecological water level of the river network and use it as the non-flood season ecological water level of the river network. Based on the annual water level change curve or ecological water level curve of the typical river network, the module determines the flood season ecological water level and the main flood season ecological water level of the river network. Based on the non-flood season ecological water level, the flood season ecological water level, and the main flood season ecological water level, the module determines the water level indicators of the river network.

[0081] The water depth calculation module is used to determine the first water depth of the river network based on the minimum water depth required by various plants in the river network, to determine the second water depth of the river network based on the minimum water depth required by various fish in the river network, and to determine the water depth index of the river network based on the first water depth and the second water depth.

[0082] The flow velocity calculation module is used to determine the first flow velocity of the river network based on a pre-constructed statistical model of algal flow velocity or chlorophyll a flow velocity, determine the second flow velocity of the river network based on the stimulus flow velocity required for the spawning behavior of various fish species in the river network during the breeding season, and determine the flow velocity index of the river network based on the first flow velocity and the second flow velocity.

[0083] The ecological flow determination module is used to adjust the ecological flow of the river network based on the correlation between the river network's water level index, water depth index, and water flow velocity index.

[0084] Specific limitations regarding the ecological flow calculation device for plain river network areas can be found in the above-described limitations regarding the ecological flow calculation method for plain river network areas, and will not be repeated here. Each module in the aforementioned ecological flow calculation device for plain river network areas can be implemented entirely or partially through software, hardware, or a combination thereof. Each module can be embedded in or independent of the processor in a computer device in hardware form, or it can be stored in the memory of a computer device in software form, so that the processor can call and execute the operations corresponding to each module.

[0085] The present invention also provides a computer-readable storage medium storing a computer program that can be used to execute the above-mentioned... Figure 1 A method for calculating ecological flow in plain river network areas is provided.

[0086] The present invention also provides Figure 5 The schematic diagram of the computer device shown is as follows: Figure 5 As shown, at the hardware level, this computer device includes a processor, internal bus, network interface, memory, and non-volatile memory, and may also include other hardware required for business operations. The processor reads the corresponding computer program from the non-volatile memory into memory and then runs it to implement the aforementioned... Figure 1 A method for calculating ecological flow in plain river network areas is provided.

[0087] Those skilled in the art will understand that implementing all or part of the processes in the methods of the embodiments can be accomplished by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the methods described. Any references to memory, storage, databases, or other media used in the embodiments provided by this invention can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, or optical storage, etc. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.

[0088] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this invention.

Claims

1. A method for calculating ecological flow in plain river network areas, characterized in that, include: The minimum ecological water level of the river network is determined and used as the non-flood season ecological water level of the river network; the flood season ecological water level and the main flood season ecological water level of the river network are determined based on the typical annual water level change curve or ecological water level curve of the river network; the water level index of the river network is determined based on the non-flood season ecological water level, the flood season ecological water level, and the main flood season ecological water level. The first water depth of the river network is determined based on the minimum water depth required by various plants in the river network, and the second water depth of the river network is determined based on the minimum water depth required by various fish species in the river network. The water depth index of the river network is determined based on the first water depth and the second water depth. The first water flow velocity of the river network is determined based on a pre-constructed statistical model of algal water flow velocity or a statistical model of chlorophyll a water flow velocity. The second water flow velocity of the river network is determined based on the stimulation water flow velocity required for the spawning behavior of various fish species in the river network during the breeding season. The water flow velocity index of the river network is determined based on the first water flow velocity and the second water flow velocity. The ecological flow of the river network is adjusted based on the correlation between the water level index, water depth index, and flow velocity index of the river network.

2. The method for calculating ecological flow in plain river network areas as described in claim 1, characterized in that, The various plants include submerged plants, phytoplankton, floating-leaved plants, and emergent plants, and the various fish include black carp, grass carp, silver carp, and bighead carp.

3. The method for calculating ecological flow in plain river network areas as described in claim 1, characterized in that, The determination of the minimum ecological water level of the river network is obtained by calculating the water level data of the river network using the 90% guarantee rate method, the 7Q10 method, and the driest month average method. The calculation expression for the 90% guarantee rate method is as follows: ； in, f(x Γ(α) is the probability density function of type P-III, and Γ(α) is the gamma function. α , β , α 0 For parameters , x For water level variables, This represents the average water level. It is the coefficient of variation, used to measure the amplitude of water level fluctuations. It is the skewness coefficient, used to describe water level distribution.

4. The method for calculating ecological flow in plain river network areas as described in claim 3, characterized in that, The calculation expression for the driest month average method is as follows: ； in, This is the average water level for the driest month in many years. The measured water level for the driest month of each year is given, where m and n are the year numbers.

5. The method for calculating ecological flow in plain river network areas as described in claim 1, characterized in that, The ecological flow of the river network is adjusted based on the correlation between the water level index, water depth index, and flow velocity index of the river network, specifically including: An ecological flow adjustment coupled model for the river network is constructed based on the fundamental equations of hydraulics and the Saint-Venant equations. Using the water level, water depth, and flow velocity of the river network as targets, the real-time measured water level, water depth, and flow velocity of the river network are used as initial values ​​and input into the ecological flow adjustment coupling model for iteration. The ecological flow of the river network is adjusted according to the iteration results.

6. An ecological flow calculation device for plain river network areas, characterized in that, include: The water level calculation module is used to determine the minimum ecological water level of the river network, and to use the minimum ecological water level as the non-flood season ecological water level of the river network; based on the annual water level change curve or ecological water level curve of the typical river network, it determines the flood season ecological water level and the main flood season ecological water level of the river network; and it determines the water level index of the river network based on the non-flood season ecological water level, the flood season ecological water level, and the main flood season ecological water level. The water depth calculation module is used to determine the first water depth of the river network based on the minimum water depth required by various plants in the river network, determine the second water depth of the river network based on the minimum water depth required by various fish in the river network, and determine the water depth index of the river network based on the first water depth and the second water depth. The flow velocity calculation module is used to determine the first flow velocity of the river network based on a pre-constructed statistical model of algal flow velocity or chlorophyll a flow velocity, determine the second flow velocity of the river network based on the stimulation flow velocity required for the spawning behavior of various fish species in the river network during the breeding season, and determine the flow velocity index of the river network based on the first flow velocity and the second flow velocity. The ecological flow determination module is used to adjust the ecological flow of the river network based on the correlation between the river network's water level index, water depth index, and water flow velocity index.

7. A computer-readable storage medium, characterized in that, The storage medium stores a computer program, which, when executed by a processor, implements a method for calculating ecological flow in plain river network areas as described in any one of claims 1 to 5.

8. A computer device, characterized in that, It includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement a method for calculating ecological flow in plain river network areas as described in any one of claims 1 to 5.

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