Water body exchange method for ecological lake and seawater

Abstract

The invention relates to the technical field of hydraulic engineering and environmental hydraulics, and discloses an ecological lake and seawater water body exchange method which comprises the following steps: firstly, establishing a two-dimensional mathematical model of hydrodynamic force and material transportation; secondly, water body exchange schemes such as free exchange and asymmetric control are set for simulation; according to the asymmetric control scheme, the water level in the lake is maintained in a specific interval through operation of fully opening during water diversion and partially opening an exchange channel during water drainage; secondly, semi-exchange periods and water level changes of all the schemes are calculated through tracer agent simulation; finally, according to a preset water level constraint condition and a water body exchange efficiency target, the calculation results of all the schemes are compared, and therefore the optimal scheme considering the ecological and landscape requirements is determined. The water exchange efficiency and the landscape water level are synchronously evaluated in a multi-target and quantitative mode through a mathematical model, and the technical problem that the two are difficult to consider in a traditional design is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydraulic engineering and environmental hydraulics, in particular to a water exchange method for an ecological lake and seawater. BACKGROUND

[0002] With the increasing development of coastal ecological restoration and urban landscape construction, building artificial or semi-closed ecological lakes with both ecological regulation and landscape entertainment functions has become an important engineering practice. Maintaining good and stable water quality in such water bodies is the core prerequisite for their successful operation, and the key technical means to achieve this goal lies in ensuring effective and continuous water exchange between them and the open sea area outside.

[0003] In engineering practice, the most direct way is to build connecting pipes or channels to realize free exchange of water between the lake and the outside sea area using natural tidal power. This mode can maximize the use of tidal energy and theoretically achieve the highest water exchange efficiency. However, the cost is the severe fluctuation of the lake water level, which often completely follows the tidal rise and fall of the outside sea. This results in the exposure of large areas of the lake's beach during low tide, which not only severely damages the aesthetic value of the landscape water body as it should be, but also limits the development of related water activities, greatly reducing its landscape function.

[0004] In order to overcome the damage caused by large fluctuations in water level to the landscape function, existing technologies usually introduce water control structures such as gates to regulate the water level. By artificially setting the opening and closing conditions of the gate, the water level in the lake can be forcibly maintained within the preset and more ideal landscape target range. Although this ensures the visual effect and stability of the lake, it also restricts the exchange capacity of the water body. In order to preserve water, the control of water flow will inevitably reduce the total amount of water entering and leaving the lake, directly leading to a decrease in water renewal speed. This makes it easy to form stagnant water zones in the lake, especially far from the exchange port, which in turn leads to water quality deterioration, contrary to the original intention of improving the ecological environment.

[0005] Therefore, the existing technology generally faces an inherent technical contradiction in the design of ecological lake water exchange schemes. Designers have to make a difficult trade-off between efficient water renewal and stable landscape water level, which are two conflicting goals. Current design methods rely more on experience or simplified evaluation for a single target, lacking a systematic evaluation process that can quantify the two core indicators of water exchange efficiency and water level stability, and accurately predict the full-lake water dynamics and water quality response under different control schemes. The lack of such evaluation methods makes the engineering scheme uncertain in the design stage, and there is a risk that the project cannot meet the dual goals of ecology and landscape after completion. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application provides a water body exchange method for an ecological lake and seawater, which solves the problem of the mutual contradiction between the water level fluctuation caused by efficient water body exchange and the requirement of maintaining a stable landscape water level in the design of an ecological lake project.

[0007] To achieve the above object, the present application is implemented by the following technical scheme: a water body exchange method for an ecological lake and seawater, comprising the following steps:

[0008] S1. Establishing a water dynamics and material transport mathematical model of the ecological lake and at least one first water body exchange channel and one second water body exchange channel thereof in communication with external seawater;

[0009] S2. In the water dynamics and material transport mathematical model, at least two gate operation schemes are set for simulation, at least one of which is an asymmetric control scheme, which defines that the gate opening states of the first water body exchange channel and the second water body exchange channel are different under water intake and water discharge conditions;

[0010] S3. In the water dynamics and material transport mathematical model, the initial water body of the ecological lake is set with a tracer concentration, and under the set tidal current boundary condition, the at least two gate operation schemes are respectively run to calculate the spatiotemporal distribution data of the tracer concentration in the ecological lake;

[0011] S4. Based on the spatiotemporal distribution data, the overall half-exchange period of the ecological lake, the half-exchange period of the preset characteristic point, and the change process of the water level in the lake over time under each scheme are calculated and output;

[0012] S5. According to the preset water level constraint condition and water body exchange efficiency target, an optimal water body exchange scheme is determined from the at least two schemes by comparing the calculation results output in step S4.

[0013] Preferably, the asymmetric control scheme in step S2 is specifically:

[0014] In the water intake condition, the gates of the first water body exchange channel and the second water body exchange channel are opened at the same time;

[0015] In the water discharge condition, only the gate of the second water body exchange channel is opened, and the gate of the first water body exchange channel is kept closed.

[0016] Preferably, in step S1, the first water body exchange channel is located on the north side of the ecological lake, and the second water body exchange channel is located on the south side of the ecological lake.

[0017] Preferably, the water level constraint condition in the S5 step is to maintain the water level of the ecological lake between 1.0 meters and 1.5 meters.

[0018] Preferably, the other scheme in the at least two gate operation schemes in the S2 step is a free exchange scheme, that is, at least one water body exchange channel is not provided with a gate, and water bodies are allowed to freely enter and exit according to the water level difference formed by natural tides.

[0019] Preferably, the calculation method of the half exchange period in the S4 step comprises:

[0020] The initial average concentration of the tracer in the ecological lake is set as C0, the change process of the average concentration C(t) of the tracer in the ecological lake with time is monitored and recorded, and when C(t) decreases to 0.5C0, the time elapsed is determined as the half exchange period.

[0021] Preferably, the preset feature points in the S4 step at least include: a near-field exchange area adjacent to the water body exchange channel, a far-field stagnant water area located in an area where the lake body water flow exchange is not active, and an intermediate channel area connecting different water areas in the lake.

[0022] Preferably, the hydrodynamic and material transport mathematical model in the S1 step is established based on two-dimensional shallow water equations and convection-diffusion equations.

[0023] Preferably, the first water body exchange channel and the second water body exchange channel in the S1 step are both pipe culverts, the pipe diameter is 0.4 meters to 0.6 meters, and the pipe length is 40 meters to 60 meters.

[0024] The present application provides a water body exchange method for an ecological lake and seawater.

[0025] 1、The present application can quantitatively evaluate the water exchange scheme, solve the problem that the water exchange efficiency and the landscape water level are difficult to consider in the previous design, and through the establishment of a unified mathematical model, the half exchange period representing the water body renewal speed and the water level change process representing the landscape effect can be calculated simultaneously, so that the designer can compare different schemes according to clear data, for example, an asymmetric control scheme that meets the water level constraint condition of 1.0 meters to 1.5 meters and also meets the water quality requirement can be selected, so that the final decision no longer depends on qualitative judgment or single objective optimization.

[0026] 2、The asymmetric control scheme provided by the present application can form a long-distance overall water body transport path in the ecological lake by setting different inlet and outlet water passage combinations, specifically, the mode of multiple-point inlet and single-point outlet during water intake and water discharge can forcibly drive the water body in the lake to produce macroscopic flow, thereby improving the water body exchange in the area far from the exchange port, and through analysis of the half-exchange period of the characteristic points at different positions in the lake, it can be proved that the method can effectively reduce the range of the water flow exchange inactive area and promote more balanced improvement of the water quality in the whole lake.

[0027] 3、The present application provides a systematic process for scheme verification and optimization before engineering implementation, reduces the uncertainty and later risk of engineering design, and the designer can test multiple operation schemes and obtain their performance parameters by using the simulation steps of the method before physical construction, the process can identify inherent defects of certain schemes in advance, for example, the free exchange scheme cannot maintain a stable water level, through the pre-selection and optimization based on simulation data, it can be ensured that the finally selected engineering scheme is technically feasible and efficient, thereby avoiding the cost and difficulty of rectification after actual construction due to unqualified effect. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a flow chart of the method of the present application;

[0029] Figure 2 is a schematic diagram of the ecological inner lake before (left) and after (right) reconstruction of the present application;

[0030] Figure 3 is a schematic diagram of the concentration distribution (left), water level (right upper), and average concentration (right lower) of scheme one of the present application at the initial time;

[0031] Figure 4 is a schematic diagram of the concentration distribution (left), water level (right upper), and average concentration (right lower) of scheme one of the present application at the 7th hour;

[0032] Figure 5 is a schematic diagram of the concentration distribution (left), water level (right upper), and average concentration (right lower) of scheme one of the present application at the 14th hour;

[0033] Figure 6 is a schematic diagram of the concentration distribution (left), water level (right upper), and average concentration (right lower) of scheme one of the present application at the 20th hour;

[0034] Figure 7 is a schematic diagram of the concentration distribution (left), water level (right upper), and average concentration (right lower) of scheme one of the present application at the 25th hour;

[0035] Figure 8 is a schematic diagram of the characteristic point position of the ecological inner lake of the present application.

[0036] Figure 9 Concentration change process at t1 for the present application scheme one;

[0037] Figure 10 Concentration change process at t2 for the present application scheme one;

[0038] Figure 11 Concentration change process at t3 for the present application scheme one;

[0039] Figure 12 Concentration change process at t4 for the present application scheme one;

[0040] Figure 13 Concentration distribution (left), water level (upper right), and average concentration (lower right) at 7 hours for the present application scheme two;

[0041] Figure 14 Concentration distribution (left), water level (upper right), and average concentration (lower right) at 14 hours for the present application scheme two;

[0042] Figure 15 Concentration distribution (left), water level (upper right), and average concentration (lower right) at 28 hours for the present application scheme two;

[0043] Figure 16 Concentration distribution (left), water level (upper right), and average concentration (lower right) at 48 hours for the present application scheme two;

[0044] Figure 17 Concentration change process at t1 for the present application scheme two;

[0045] Figure 18 Concentration change process at t2 for the present application scheme two;

[0046] Figure 19 Concentration change process at t3 for the present application scheme two;

[0047] Figure 20 Concentration change process at t4 for the present application scheme two. DETAILED DESCRIPTION

[0048] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the present application specification. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0049] Please refer to the drawings in the present application specification Figure 1Embodiments of the present application provide a method for water exchange between an ecological lake and seawater. In a specific implementation scenario, a two-dimensional mathematical model coupling hydrodynamic and material transport processes is constructed to achieve this. The model aims to accurately reproduce the internal water flow movement and water exchange process of a specific ecological lake under the action of tides.

[0050] The core of the mathematical model consists of two interrelated parts: hydrodynamic calculation and material transport calculation. The hydrodynamic calculation part is based on a two-dimensional shallow water equation set to simulate the rise and fall of water levels in the lake and the changes in water flow speed and direction over time at various locations under the external marine tide drive, thereby generating a dynamic flow field for the entire lake. The material transport calculation part is based on the convection-diffusion equation, which uses the dynamic flow field calculated by the hydrodynamic part to simulate the spatiotemporal distribution changes of a set tracer under the combined action of water flow carrying (i.e., convection) and its own concentration gradient (i.e., diffusion).

[0051] In the process of constructing the model, the ecological lake under study needs to be geometrically generalized first. Based on the actual coastline data and underwater topographic measurement data of the ecological lake, a two-dimensional calculation grid is established that can reflect its true shape and water depth distribution. On this basis, two water exchange channels connecting the inner lake and the outer sea are set in the model. According to the specific layout of the present embodiment, the first water exchange channel is set on the north side of the ecological lake, and the second water exchange channel is set on the south side of the ecological lake.

[0052] In the present embodiment, both of these water exchange channels are designed as pipe culverts with specific specifications. As a preferred solution, the pipe culvert is set to have a pipe diameter of 0.5 meters and a pipe length of 50 meters, with the same bottom elevation at both ends to adapt to the geological and hydrological conditions of the project site. In other application scenarios, the pipe diameter can be selected within the range of 0.4 meters to 0.6 meters, and the pipe length can be adjusted within the range of 40 meters to 60 meters, and the method of the present application is still applicable.

[0053] To drive the operation of the entire model, its boundary conditions need to be set. In the model, the location representing the interface with the outer sea, i.e., the open boundary, is input with a time-varying tidal level process, which can use the measured or astronomical tide data of the representative spring tide period in the study area. The part of the model representing the land shoreline of the lake is set as a fixed, impermeable closed boundary. Through the above configuration, the entire mathematical model can serve as a digital experimental platform for subsequent simulation and evaluation of different exchange schemes.

[0054] After the above mathematical model is established, at least two different running schemes are set up for simulation and calculation to evaluate and optimize the water exchange effect of the ecological lake. The core difference between these schemes lies in the different control methods of the north and south water exchange channels.

[0055] The first scheme is a free exchange scheme, which is used as a benchmark for subsequent evaluation. In the setting of this scheme, the gates of the two exchange channels are not installed or kept open. Therefore, the exchange between the water body in the lake and the seawater outside is completely driven by the water level difference between the inside and outside formed by natural tides, and the water flow can freely enter and exit without any artificial intervention.

[0056] The second scheme is an asymmetric control scheme, which is a preferred embodiment provided by the present application. This scheme is equipped with independently controllable gates at both exchange channels and follows a set of preset asymmetric operation logic. The goal of this logic is to maintain the water level in the ecological lake within a specific target interval, which is set to 1.0-1.5 meters in this embodiment.

[0057] The specific operation rules of this asymmetric control scheme are as follows: in the water intake condition, i.e., when the instantaneous tide level of the external seawater is higher than the water level in the lake, the gates of the first water body exchange channel on the north side and the second water body exchange channel on the south side are opened simultaneously to maximize the intake of fresh seawater.

[0058] On the contrary, in the water discharge condition, i.e., when the water level in the lake is higher than the instantaneous tide level of the external seawater, only the gate of the second water body exchange channel on the south side is opened for water discharge, and the gate of the first water body exchange channel on the north side is kept closed. Through this asymmetric operation of bidirectional in water intake and unidirectional in water discharge, precise regulation of the water volume and water level in the lake is achieved to achieve the preset goal of maintaining the landscape water level. Simulating these two completely different operation schemes can provide sufficient quantitative basis for subsequent optimization decision-making.

[0059] To quantify the difference in water exchange effect between the two aforementioned operation schemes, the present method further implements tracer tracking simulation in the constructed mathematical model. At the initial time of simulation, the entire water body in the ecological lake is set to a uniform initial tracer concentration of C0. This tracer is defined as an ideal conservative substance in the model, which does not decay physically or participate in chemical reactions during simulation. At the same time, the tracer concentration of seawater outside the model boundary is always set to zero.

[0060] Based on this setting, the model runs with the water body containing tracer in the lake being exchanged with the external seawater not containing tracer, resulting in a gradual decrease in the average concentration C(t) of the tracer in the lake over time. The present method uses the half-exchange period as the core indicator for evaluating the water body renewal efficiency.

[0061] The specific calculation method of the half-exchange period is as follows: the change process of the average concentration C(t) of the tracer in the lake is monitored and recorded, and when the concentration value is first reduced to half of the initial concentration, i.e., 0.5C0, the time elapsed is determined as the overall half-exchange period under the scheme.

[0062] In addition to evaluating the overall exchange efficiency, the method also focuses on the spatial uniformity of the water exchange process in the lake. For this purpose, a number of representative feature monitoring points are pre-arranged in the calculation domain of the model to analyze the water renewal in local areas. The selection of these feature points is not random, but is based on the hydrodynamic characteristics of the lake, and respectively represents different types of functional areas.

[0063] Specifically, these feature points at least include: a near-field exchange zone monitoring point adjacent to the outlet of the water exchange channel, to reflect the area most directly affected by the inflow of fresh seawater; a far-field stagnant water zone monitoring point located in an area with inactive water flow exchange in the lake body, to evaluate the ability of the scheme to improve the "dead water area"; and an intermediate channel zone monitoring point located in a narrow area connecting different main water areas in the lake, to investigate the connectivity of water transport within the lake. By calculating the half-exchange periods of these feature points respectively, the water flow organization pattern and the spatial distribution characteristics of the exchange efficiency induced by each operation scheme in the lake can be comprehensively revealed.

[0064] After completing the simulation calculations of the free exchange scheme and the asymmetric control scheme respectively, the method obtains two complete sets of spatiotemporal distribution data. Based on these data, each key evaluation index under each scheme can be further calculated and output, including the overall half-exchange period of the ecological lake, the half-exchange periods of each preset feature point, and the change process of the water level in the lake over time.

[0065] In the simulation results of this embodiment, the free exchange scheme exhibits the highest exchange efficiency, with a shorter overall half-exchange period. However, the water level in the lake under this scheme changes dramatically, with fluctuations exceeding the preset landscape water level constraint, especially during low tide periods, when the lake water level is significantly lower than the target lower limit of 1.0 meters.

[0066] In contrast, the simulation results of the asymmetric control scheme show that its overall half-exchange period is longer than that of the free exchange scheme, indicating a relatively slower water renewal speed. However, it is crucial that the water level of the ecological lake is successfully maintained within the target interval of 1.0 meters to 1.5 meters throughout the entire operation period of the scheme, without ever exceeding the limit. At the same time, the analysis of different feature points in the lake shows that the scheme can effectively drive the water in the far-field stagnant water area to participate in exchange, showing better spatial exchange uniformity.

[0067] Finally, the results of the above two schemes are compared to determine the optimal water exchange scheme according to the preset water level constraint condition and water body exchange efficiency target. The decision-making process first filters according to the rigid index of the water level constraint condition. Since the free exchange scheme cannot meet the requirement of maintaining the water level between 1.0 meters and 1.5 meters, the scheme is excluded first.

[0068] The asymmetric control scheme completely meets the water level constraint condition. On this basis, although its exchange efficiency is not the highest, its water body exchange capacity is still within the acceptable engineering target range, and it can significantly improve the uniformity of exchange in the lake. Therefore, after comprehensive evaluation, the asymmetric control scheme is determined as the optimal scheme in this embodiment which takes into account both stable landscape water level and effective water body exchange.

[0069] Test example:

[0070] Please refer to the attached Figure 2 - attached Figure 20 In order to verify the effectiveness of the method described in the present application, a specific test case is provided. The application object of this case is an ecological inner lake which is transformed from a discarded breeding pond. The shapes before and after the transformation are shown in Figure 2 .

[0071] Firstly, according to the actual topography of the ecological lake, a two-dimensional mathematical model including water dynamics and material transport calculation is established. Two water exchange channels connected to the outer sea are set in the model, both of which are pipe culverts, one located on the north side of the lake body and the other located on the south side. According to the engineering design, the pipe diameters of the two pipe culverts are both set to 0.5 meters, the pipe lengths are both 50 meters, and the bottom elevations of the two ends are both 0 meters.

[0072] Based on the model, the following two schemes are set for simulation calculation and comparison.

[0073] Scheme one (free exchange scheme): the south and north pipe culverts are not provided with gates, and the water body in the lake and the outer sea are freely exchanged under the action of natural tides.

[0074] Scheme two (asymmetric control scheme): the south and north pipe culverts are both equipped with controllable gates. The control target of this scheme is to ensure that the water level in the inner lake varies within the range of 1.0 meters to 1.5 meters. The specific operation rule is: when water needs to be introduced, the south and north gates are both opened; when water needs to be discharged, only the south gate is opened and the north gate remains closed.

[0075] At the initial moment of simulation calculation, the water body of the ecological inner lake is set as a uniform surface source, and the initial concentration of the tracer is 1.0 g / L (as shown in Figure 3 left), while the tracer concentration of the outer sea water is always 0. Subsequently, under the same external tidal current driving, scheme one and scheme two are respectively run.

[0076] Analyze the calculation results of Scheme 1. For example... Figures 3 to 7 As shown by the curve in the lower right corner, the overall semi-exchange cycle of the entire ecological lake is approximately 20 hours. Under this scheme, as... Figures 3 to 7 As shown by the curve in the upper right corner, the water level in the lake varies from 0.38 meters to 1.6 meters. To analyze the spatial differences in water exchange within the lake, four characteristic points t1-t4 were set up within the lake (their locations are shown in the figure). Figure 8 As shown). Based on the concentration change process lines of each characteristic point ( Figures 9 to 12 According to calculations, the half-exchange cycle of the southern region (characteristic point t2) is about 9 hours, and that of the northern region (characteristic point t1) is about 19 hours; while the exchange capacity of the narrow passage in the middle (characteristic point t3) is weak, with a half-exchange cycle of more than 25 hours; and the region located at the top of the inner lake (characteristic point t4) receives almost no exchange.

[0077] Analyze the calculation results of Scheme 2. For example... Figures 13 to 16 As shown in the series of figures, the overall semi-exchange cycle of the entire ecological lake is approximately 33 hours. Under the control of this scheme, the lake water level was successfully maintained within the preset target range of 1.0 meter to 1.5 meters. Based on the characteristic points (locations see...) Figure 8 Concentration change process line () Figures 17 to 20 According to calculations, the southern region (characteristic point t2), which serves as the main drainage outlet, has the strongest exchange capacity, with a half-exchange cycle of about 13 hours; the northern region (characteristic point t1), which is only opened during water intake, has a slower exchange capacity, with a half-exchange cycle of about 20 hours; the middle channel (characteristic point t3) has a half-exchange cycle of 33 hours; while the water exchange capacity of the top region of the lake (characteristic point t4) remains very poor.

[0078] Finally, the two schemes were compared and the optimal one was selected. Although Scheme 1 has a higher water exchange efficiency (half-exchange cycle of 20 hours), its water level drops to a minimum of 0.38 meters, failing to meet the water level constraint of 1.0 to 1.5 meters. Although Scheme 2 has a lower water exchange efficiency (half-exchange cycle of 33 hours), it fully meets the water level constraint. Therefore, based on comprehensive evaluation, Scheme 2 was determined to be the superior scheme that can simultaneously meet the ecological water quality exchange requirements and the landscape water level requirements.

[0079] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An ecological lake and seawater water body exchange method, characterized by, The method comprises the following steps: S1, establishing a hydrodynamic and material transport mathematical model of the ecological lake and at least one first water exchange channel and one second water exchange channel connected with the outside seawater; S2, in the hydrodynamic and material transport mathematical model, at least two gate operation schemes are set for simulation, at least one of which is an asymmetric control scheme, which defines that the gate opening states of the first water exchange channel and the second water exchange channel are different in the water intake working condition and the water discharge working condition; S3, in the hydrodynamic and material transport mathematical model, the initial water body of the ecological lake is set with tracer concentration, and the at least two gate operation schemes are respectively run under the set tidal current boundary condition to calculate the space-time distribution data of the tracer concentration in the ecological lake; S4, based on the space-time distribution data, the overall half-exchange period of the ecological lake, the half-exchange period of the preset characteristic point, and the change process of the water level in the lake with time under each scheme are calculated and output; S5, according to the preset water level constraint condition and water exchange efficiency target, an optimal water exchange scheme is determined from the at least two schemes by comparing the calculation results output in step S4.

2. The method of claim 1, wherein the method is characterized by, The asymmetric control scheme in step S2 is specifically: In the water intake working condition, the gates of the first water exchange channel and the second water exchange channel are opened at the same time; In the water discharge working condition, only the gate of the second water exchange channel is opened, and the gate of the first water exchange channel is kept closed.

3. The method of claim 1, wherein the method is characterized by, In step S1, the first water exchange channel is located on the north side of the ecological lake, and the second water exchange channel is located on the south side of the ecological lake.

4. The method of claim 3, wherein the water body is a lake or a sea. The water level constraint condition in step S5 is to maintain the water level of the ecological lake between 1.0 meters and 1.5 meters.

5. The method of claim 1, wherein the method is characterized by, Another scheme in the at least two gate operation schemes in step S2 is a free exchange scheme, that is, at least one water exchange channel is not provided with a gate, and water bodies are allowed to freely enter and exit according to the water level difference formed by natural tides.

6. The method of claim 1, wherein the method is characterized by, The calculation method of the half-exchange period in step S4 includes: The initial average concentration of the tracer in the ecological lake is set as C0, the change process of the average concentration C(t) of the tracer in the ecological lake with time is monitored and recorded, and when C(t) decreases to 0.5C0, the time elapsed is determined as the half-exchange period.

7. The method of claim 1, wherein the method is characterized by, The preset characteristic points in step S4 at least include: a near-field exchange area adjacent to the water exchange channel, a far-field stagnant water area located in an inactive area of lake water flow exchange, and an intermediate channel area connecting different water areas in the lake.

8. The method of claim 1, wherein the method is characterized by, The hydrodynamic and material transport mathematical model in step S1 is established based on two-dimensional shallow water equation and convection-diffusion equation.

9. The method of claim 1, wherein the method is characterized by, The first water exchange channel and the second water exchange channel in step S1 are both pipe culverts, with a pipe diameter of 0.4 meters to 0.6 meters and a pipe length of 40 meters to 60 meters.

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