An optimization calculation method for the water storage of inland lakes considering flood control and ecological impacts

Abstract

The present invention discloses an optimized calculation method for the water storage of endorheic lakes considering flood control and ecological impacts. The method includes the following steps: Step 1, analysis of the connectivity of the lake water system; Step 2, analysis of the water storage capacity of the lake; Step 3, construction of a distributed hydrological model; Step 4, construction and calculation of an integrated hydrological-water volume scheduling model; Step 5, construction of a water storage optimization model; Step 6, optimized calculation of the lake water storage. The optimized calculation method for the water storage of endorheic lakes considering flood control and ecological impacts according to the present invention realizes the optimized scheduling of the water volume of endorheic lakes while taking into account ecological and flood control safety, provides a scientific basis for protecting the ecology and flood control safety of endorheic river basins under current climate change conditions, and has very high application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of water conservancy engineering, and particularly relates to an optimized calculation method for the water storage of endorheic lakes considering flood control and ecological impacts. Background Art

[0002] The endorheic area in China accounts for about 36% of the total land area of the country, and is mostly distributed in the arid climate regions in the northwest and the central and northern parts of the Qinghai-Tibet Plateau. In the endorheic area, there are often terminal lakes located in the low-lying terrain of the basin without external drainage channels, such as Toson Lake in Qinghai, Jilantai Salt Lake in Inner Mongolia, and Caohai in Guizhou. Affected by global warming in recent years, the water levels of many lakes in the endorheic area have been rising continuously, and the lake shorelines have expanded outward as a whole during the rising process of the water level, causing the inundation of surrounding grasslands, wetlands, houses and infrastructure, resulting in inundation disasters. Even some lakes have overflowed due to the continuous increase in water volume, causing unpredictable flood disasters. For example, Xiaochaidan Lake in Haixi Mongol and Tibetan Autonomous Prefecture, Qinghai Province, has rapidly expanded its lake surface since 2020, posing a threat to the operation safety of the Liugou Expressway and Dexiao Expressway in the west and south of the lake shore. Inland lakes in the areas of Coqen and Gerze in Tibet are affected by factors such as rising temperature, thawing of frozen soil, increasing precipitation, and intensifying melting of ice and snow in the basin, resulting in continuous expansion of the water area and intensifying land swampification in the area near the lake, posing a significant threat to surrounding facilities such as highways and houses.

[0003] By planning, constructing and reasonably using various water projects, the surface water can be regulated, controlled and distributed in terms of time and space, so as to achieve multiple goals such as flood control and disaster reduction, ecological protection and improvement of comprehensive benefits. Taking the Yangtze River Basin as an example, its optimized operation practice has achieved remarkable results in aspects such as flood control, power generation and water supply. By building reservoir projects such as the Three Gorges, Wudongde and Baihetan, and formulating scientific operation plans, it has successfully coped with many large floods and effectively ensured the flood control safety in the middle and lower reaches of the Yangtze River; by reasonably regulating the reservoir water storage and power generation output, the maximization of power generation benefits has been achieved; by water supply operation, the production, living and ecological water use conditions in the middle and lower reaches have been improved.

[0004] However, current research and practice on optimal water quantity scheduling mainly focus on river basins with external flow, while relatively less attention is paid to river basins with internal flow. Inland rivers and rivers with external flow have completely different hydrological and hydraulic characteristics. The main manifestation is that the terminal lakes within the river basin only receive the water from the basin and have no natural drainage channels. The water consumption mainly depends on evaporation and seepage. Climate change disrupts the original balance between lake inflow and evaporation. The water volume of some lakes continues to increase, resulting in the risk of overflow at the low points of the lake shorelines, causing unconventional flood disasters. In addition, the unique hydrological characteristics and geographical environment of inland rivers determine the fragility of their ecosystems. On the one hand, the water sources of inland rivers mainly come from the melting of alpine snow and ice and mountain precipitation. Climate change such as the retreat of glaciers and changes in precipitation patterns caused by global warming will directly affect the water volume of inland rivers and thus their ecosystems. On the other hand, the ecosystem of inland river basins is often relatively simple and the biodiversity is relatively low. This simple ecosystem structure makes the system less resistant to external disturbances, and once damaged, it is more difficult to recover.

[0005] Therefore, how to achieve the optimal calculation of the water storage of inland lakes while considering flood control and ecological impacts is a technical problem that urgently needs to be solved at present. Summary of the Invention

[0006] The purpose of the present invention is to provide an optimal calculation method for the water storage of inland lakes considering flood control and ecological impacts to solve the above technical problems.

[0007] To achieve the above purpose, the present invention provides the following technical solutions:

[0008] The present invention discloses an optimal calculation method for the water storage of inland lakes considering flood control and ecological impacts, and the method includes the following steps:

[0009] Step 1, analysis of the connectivity of lake water systems: Collect DEM data, lake distribution data, and remote sensing image data of the target basin; based on the collected DEM data, obtain the river network water system distribution of the target basin through filling depressions, flow direction analysis, flow calculation, and river network water system extraction; based on the collected lake distribution data, compare and verify it with the collected remote sensing image data to determine the distribution of lake depressions in the target basin; according to the river network water system distribution and lake depression distribution of the target basin, analyze the connectivity of the lakes, make a generalized map of lake connectivity, and determine the confluence path of each lake in the target basin.

[0010] Step 2, analysis of the water storage capacity of lakes: Based on the collected remote sensing image data, analyze the lake surface areas at different time points, form a sequence according to the area size, denoted as A_list = [A1, A2,..., A i ,..., A N , with a total of N data, where A iis the lake surface area at the \(i\)th moment; based on the collected DEM data, the lake water levels corresponding to each time point are obtained, forming a water level sequence corresponding to the area sequence, denoted as \(H\_list = [H1, H2,..., H i ,..., H N , with a total of \(N\) data, where \(H i is the lake water level at the \(i\)th moment; according to the water level and area data at different time points, the volume difference of water storage is estimated using the volume calculation formula of a frustum of a pyramid, forming a water storage sequence corresponding to the area sequence, denoted as \(R\_list = [V1, V1 + ΔV2,..., V i-1 +ΔV i ,..., V N-1 +ΔV N , with a total of \(N\) data, where \(V1\) is the initial storage capacity, and when \(A1 = 0\), \(V1 = 0\), and \(ΔV i is the difference in water storage between the \(i\)th and \((i - 1)\)th values, and the calculation formula is:

[0011]

[0012] where \(A i is the lake surface area at the \(i\)th moment, and \(H i is the lake water level at the \(i\)th moment;

[0013] According to the obtained area sequence, water level sequence, and water storage sequence, fit the water level - water storage relationship curve and water level - area relationship curve, where the lake surface area corresponding to the lake bottom water level is 0 and the lake water storage is 0;

[0014] Step 3: Construction of a distributed hydrological model: Construct a distributed hydrological model, which is characterized by using grid - type calculation units, and the calculation grid can cover the entire basin; the model is constructed based on the water balance and energy balance equations, comprehensively considering the interactions of climate, terrain, soil properties, and vegetation, and supports confluence calculation. The hydrometeorological elements that can be calculated in the model include at least precipitation, ground evapotranspiration, water surface evaporation, surface runoff, and subsurface runoff;

[0015] Step 4: Construction and calculation of an integrated hydrological - water volume regulation model: First, generalize the target basin into three types of units: runoff - generating sub - regions, lakes, and sections. On this basis, analyze the topological relationships of each unit in the basin, and conduct the construction and calculation of the integrated hydrological - water volume regulation model, which specifically includes the following steps:

[0016] Step 4 - 1: Construction of an integrated hydrological - water volume regulation model, including the following steps:

[0017] Step 4-1-1: Based on the river network water system and lake depression distribution analyzed in Step 1, divide the target basin into different runoff generation sub-areas. The runoff of each runoff generation sub-area unit flows into lakes or section units, and a topological generalization map of the basin unit is made.

[0018] Step 4-1-2: Based on the confluence paths of each lake in the basin, associate each runoff generation sub-area with the distributed hydrological model calculation grids divided in Step 3. Each runoff generation sub-area is associated with several calculation grids.

[0019] Step 4-1-3: Associate the lakes with the distributed hydrological model calculation grids divided in Step 3. For the calculation grids covered by the lake water surface, no runoff generation and confluence calculations are performed, and only rainfall and evaporation are considered.

[0020] Step 4-1-4: Construct the basin topological relationship, which reflects the upstream and downstream relationships of each runoff generation sub-area, lake and section, and includes the association relationship between the generalized basin units and the distributed hydrological model calculation grids. Manage the basin topological relationship data in a JSON file.

[0021] Step 4-1-5: Manage the characteristic data of each lake unit in the basin in a JSON file. The characteristic data of each lake unit includes name, water level curve, area curve, water storage curve, lake overflow outlet elevation, lake overflow outlet width, and initial water level elevation.

[0022] Step 4-2: Calculate the integrated hydrological-water volume regulation model, including the following steps:

[0023] Step 4-2-1: Use the distributed hydrological model to complete the simulation of the hydrological process of the entire basin for several years. The time step of the model output is 1 day.

[0024] Step 4-2-2: Read in the basin topological relationship data in Step 4-1-4 and the characteristic data of the lake units in Step 4-1-5.

[0025] Step 4-2-3: Based on the calculation results in Step 4-2-1 and the association relationships between the runoff generation sub-areas, lakes and the distributed hydrological model calculation grids, calculate the multi-year average monthly runoff of each runoff generation sub-area, and calculate the multi-year average monthly precipitation and monthly evaporation of each lake.

[0026] Step 4-2-4: Conduct water storage and regulation calculations for each unit in the basin; according to the basin topological relationship, read the inflow data of each unit from upstream to downstream in sequence. If there are multiple upstream inflows, synthesize the flows; conduct storage and regulation calculations for lake units. Based on the lake water level-storage curve, as well as the bottom elevation and width of the overflow outlet, analyze the water storage capacity and discharge capacity of the lake, and calculate the average annual monthly inflow water volume, precipitation, evaporation, storage capacity, water level, and overflow volume of each lake. Then, according to the water level-area curve, calculate the change process of the lake water surface area.

[0027] Step 4-2-5: Traverse all units in the basin to complete the calculations.

[0028] Step 5: Construct a water storage optimization model: Combine an optimization algorithm with the hydrological-water volume scheduling integrated model constructed in Step 4 to construct a water storage optimization model.

[0029] Step 6: Conduct optimized calculations for lake water storage: Use the water storage optimization model constructed in Step 5 to conduct optimized calculations to obtain the optimized overflow elevations of each lake in the basin.

[0030] Furthermore, the specific process of managing the basin topological relationship data in JSON files in Step 4-1-4 is as follows: Manage the generalized basin units in the form of JSON objects. This object includes "Name", "Id", "Type", "NextId", and "Grid" attributes. Among them, the "Name" attribute stores the name of the unit; the "Id" attribute stores the encoding of the unit, and this encoding is unique among all units; the "Type" attribute stores the type of the unit, with the runoff generation and concentration unit being "Watershed", the lake unit being "Reservoir", and the cross-section unit being "Section"; the "NextId" attribute stores the encoding of the downstream unit of this unit, and this encoding is the "Id" of the first downstream unit of this unit according to the basin topological relationship. When this unit is the most downstream unit in the basin topological relationship, that is, the terminal lake, "NextId" is -1; when this unit is of the runoff generation area or lake type, it includes the "Grid" attribute, and "Grid" is of array type, storing the distributed hydrological model calculation grid numbers associated with this unit.

[0031] Furthermore, the specific process of managing the characteristic data of each lake unit in the basin in JSON files in Step 4-1-5 is as follows: Manage the lake units in the form of JSON objects, and the object includes attributes of "Name", "H_list", "A_list", "R_list", "E", "B", and "E_ini"; among them, the "Name" attribute stores the name of the unit; the "H_list" attribute stores the water level curve obtained in Step 2; the "A_list" attribute stores the area curve obtained in Step 2; the "R_list" attribute stores the water storage curve obtained in Step 2; the "E" attribute stores the elevation of the lake overflow outlet; the "B" attribute stores the width of the lake overflow outlet; the "E_ini" attribute stores the initial water level elevation for lake regulation calculation.

[0032] Furthermore, the optimization algorithms used in Step 5 are genetic algorithm, particle swarm algorithm or SCE-UA algorithm.

[0033] Furthermore, the optimization variable of the water storage optimization model constructed in Step 5 is the elevation of the overflow outlets of lakes in the basin other than the tail lake, and the variable range is set to the current elevation of the overflow outlet to the top elevation of the drainage project within the engineering feasibility range;

[0034] Set the constraint condition of the water storage optimization model that the water level of the tail lake does not exceed the overflow water level;

[0035] Add the adaptability index attribute of animals and plants in the inundation impact area of the lake to the lake unit in Step 4-1-4, and name the adaptability indices of different animals and plants as "Index_1, Index_2,..." in sequence, and the value range is 0 to 1, where 1 represents the strongest adaptability;

[0036] Set the optimization objective function of the water storage optimization model to minimize the weighted sum of the adaptability indices of the relative areas of lakes in the basin, that is, the impact of the increase in the inundation range of the lake on the adaptability of species is minimized, as shown in the following formula:

[0037]

[0038] In the formula, Area i is the area of the i-th lake in the basin; Area_Max i is the maximum area of the i-th lake under the current conditions in the basin, that is, the lake area corresponding to the elevation of the overflow outlet; N' is the number of lakes in the basin; M is the number of species considered for adaptability; Index_i_j is the adaptability index of the j-th species in the inundation impact area of the i-th lake.

[0039] The beneficial effects of the present invention are as follows: The method for optimizing the calculation of the water storage in endorheic lakes considering flood control and ecological impacts realizes the optimal scheduling of the water volume in endorheic lakes while taking into account both ecology and flood control safety, provides a scientific basis for protecting the ecology and flood control safety in endorheic river basins under current climate change conditions, and has very high application value.

[0040] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is the flow chart of the method of the present invention;

[0042] Figure 2 is the DEM data map of the endorheic river basin in Embodiment 1;

[0043] Figure 3 is the lake distribution data map of the endorheic river basin in Embodiment 1;

[0044] Figure 4 is the remote sensing image data map of the endorheic river basin in Embodiment 1;

[0045] Figure 5 is the river network water system distribution map of the basin extracted based on the DEM data in Embodiment 1;

[0046] Figure 6 is the generalized lake connectivity map in Embodiment 1;

[0047] Figures 7 to 17 are the water level - water storage - area relationship curves of Lakes 1 to 11 in the basin in Embodiment 1 respectively;

[0048] Figure 18 is the distributed hydrological model calculation grid distribution map in Embodiment 1;

[0049] Figure 19 is the topological generalization map of the basin unit in Embodiment 1;

[0050] Figure 20 is the relationship map of runoff generation sub - regions, lakes and calculation grids in the basin in Embodiment 1. SPECIFIC EMBODIMENTS

[0051] The present invention discloses a method for optimizing the calculation of the water storage in endorheic lakes considering flood control and ecological impacts. As Figure 1 shown, the method includes the following steps:

[0052] Step 1. Analysis of lake water system connectivity: Collect DEM data, lake distribution data, and remote sensing image data of the target basin. Based on the collected DEM data, through filling depressions, flow direction analysis, flow calculation, and river network extraction, obtain the river network distribution of the target basin. Based on the collected lake distribution data, compare and verify it with the collected remote sensing image data. When necessary, conduct on-site investigations to determine the distribution of lake depressions in the target basin. According to the river network distribution and lake depression distribution of the target basin, analyze the connectivity between lakes, create a generalized map of lake connectivity, and determine the confluence path of each lake in the target basin.

[0053] Step 2. Analysis of lake water storage capacity: Based on the collected remote sensing image data, analyze the lake surface area at different time points, form a sequence according to the area size, denoted as A_list = [A1, A2,..., A i ,..., A N , with a total of N data, where A i is the lake surface area at the i-th moment. Based on the collected DEM data, obtain the lake water levels corresponding to each time point, form a water level sequence corresponding to the area sequence, denoted as H_list = [H1, H2,..., H i ,..., H N , with a total of N data, where H i is the lake water level at the i-th moment. According to the water level and area data at different time points, use the volume calculation formula of a frustum to estimate the water storage capacity difference, form a water storage capacity sequence corresponding to the area sequence, denoted as R_list = [V1, V1 + ΔV2,..., V i-1 + ΔV i ,..., V N-1 + ΔV N , with a total of N data, where V1 is the initial storage capacity. When A1 is 0, V1 is equal to 0, and ΔV i is the water storage capacity difference between the i-th and the (i - 1)-th values. The calculation formula is as follows:

[0054]

[0055] where, A i is the lake surface area at the i-th moment, and H i is the lake water level at the i-th moment.

[0056] According to the obtained area sequence, water level sequence, and water storage capacity sequence, fit the water level - water storage capacity relationship curve and the water level - area relationship curve, where the lake surface area corresponding to the lake bottom water level is 0 and the lake water storage capacity is 0.

[0057] Step 3: Construction of distributed hydrological model: Construct a distributed hydrological model, which features grid-based calculation units that can cover the entire basin. The model is constructed based on water balance and energy balance equations, can comprehensively consider the interactions among climate, terrain, soil properties, and vegetation, and supports runoff concentration calculation. The hydrometeorological elements that can be calculated in the model include at least precipitation, ground evapotranspiration, water surface evaporation, surface runoff, and groundwater runoff, etc.

[0058] Step 4: Construction and calculation of integrated hydrological-water volume regulation model: Generalize the target basin into three types of units: runoff generation sub-areas, lakes, and sections. On this basis, analyze the topological relationships among the units in the basin and conduct the construction and calculation of the integrated hydrological-water volume regulation model, which specifically includes the following steps:

[0059] Step 4-1: Construct an integrated hydrological-water volume regulation model, including the following steps:

[0060] Step 4-1-1: Based on the river network water system and the distribution of lakes and depressions analyzed in Step 1, divide the target basin into different runoff generation sub-areas, and the runoff of each runoff generation sub-area unit flows into the lake or section unit, and make a topological generalization map of the basin units.

[0061] Step 4-1-2: Based on the runoff concentration paths of the lakes in the basin, further associate each runoff generation sub-area with the calculation grids divided in the distributed hydrological model in Step 3, and each runoff generation sub-area is associated with several calculation grids.

[0062] Step 4-1-3: Associate the lakes with the calculation grids divided in the distributed hydrological model in Step 3. The calculation grids covered by the lake water surface do not perform runoff generation and concentration calculations, and only rainfall and evaporation are considered.

[0063] Step 4-1-4: Construct the watershed topological relationship, which reflects the upstream and downstream relationships of each runoff generation area, lake, and section, and includes the association relationship between the generalized watershed units and the calculation grids of the distributed hydrological model. Manage the watershed topological relationship data in a JSON file. Specifically: Manage the generalized watershed units in the form of JSON objects, and this object includes attributes such as "Name", "Id", "Type", "NextId", "Grid", etc. The "Name" attribute stores the name of the unit; the "Id" attribute stores the code of the unit, and this code is unique among all units; the "Type" attribute stores the type of the unit, the runoff generation and concentration unit is "Watershed", the lake unit is "Reservoir", and the section unit is "Section"; the "NextId" attribute stores the code of the downstream unit of this unit, and this code is the "Id" of the first downstream unit of this unit according to the watershed topological relationship. When this unit is the most downstream unit in the watershed topological relationship, that is, the terminal lake, "NextId" is -1; when this unit is of the runoff generation area or lake type, it includes the "Grid" attribute, and "Grid" is of array type, storing the numbers of the calculation grids of the distributed hydrological model associated with this unit.

[0064] Step 4-1-5: Manage the characteristic data of each lake unit in the watershed in a JSON file. Specifically: Manage the lake units in the form of JSON objects, and this object includes attributes such as "Name", "H_list", "A_list", "R_list", "E", "B", "E_ini", etc. The "Name" attribute stores the name of the unit; the "H_list" attribute stores the water level curve obtained in Step 2; the "A_list" attribute stores the area curve obtained in Step 2; the "R_list" attribute stores the water storage curve obtained in Step 2; the "E" attribute stores the elevation of the lake overflow outlet; the "B" attribute stores the width of the lake overflow outlet; the "E_ini" attribute stores the initial water level elevation for the lake regulation calculation.

[0065] Step 4-2: Calculate the integrated hydrological-water volume scheduling model, including the following steps:

[0066] Step 4-2-1: Use the distributed hydrological model to complete the simulation of the hydrological process of the entire watershed for several years, and the time step of the model output is 1 day;

[0067] Step 4-2-2: Read in the watershed topological relationship data prepared in Step 4-1-4 and the characteristic data of the lake units prepared in Step 4-1-5;

[0068] Step 4-2-3: Based on the calculation results in Step 4-2-1 and the correlation relationships among the runoff generation sub-areas, lakes, and the computational grids of the distributed hydrological model, calculate the average monthly runoff of each runoff generation sub-area over the years, and calculate the average monthly precipitation and evaporation of each lake over the years.

[0069] Step 4-2-4: Conduct water storage and regulation calculations for each unit within the basin. According to the basin topology relationship, read the inflow data of each unit from upstream to downstream in sequence. If there are multiple upstream inflows, synthesize the flows. For lake units, conduct storage and regulation calculations. Based on the lake water level-storage capacity curve, as well as the bottom elevation and width of the spillway, analyze the water storage capacity and discharge capacity of the lake, and calculate the average monthly inflow water volume, precipitation, evaporation, storage capacity, water level, and overflow discharge of each lake over the years. And according to the water level-area curve, calculate the change process of the lake water surface area.

[0070] Step 4-2-5: Traverse all units within the basin to complete the calculations.

[0071] Step 5: Construct a water storage optimization model: Combine the optimization algorithm with the hydrological-water volume scheduling integrated model constructed in Step 4 to construct a water storage optimization model. The optimization algorithms that can be used include common optimization algorithms such as genetic algorithm, particle swarm algorithm, and SCE-UA algorithm.

[0072] Specifically, the optimization variable of the water storage optimization model is the elevation of the spillway of lakes other than the terminal lake within the basin, and the variable range is set from the current spillway elevation to the top elevation of the drainage project within the engineering feasibility range. Set the constraint condition of the water storage optimization model as that the water level of the terminal lake does not exceed the overflow water level.

[0073] To consider the impact of lake storage and regulation on the ecology, add the suitability index attribute of animals and plants in the inundation impact area of the lake in the lake unit in Step 4-1-4. The suitability indices of different animals and plants are named successively as "Index_1, Index_2...", etc., and the value range is all 0-1, where 1 represents the strongest suitability, that is, the increase in the lake water surface has a greater impact on its survival in this basin.

[0074] Set the optimization objective function of the water storage optimization model as the minimum weighted sum of the suitability indices of the relative areas of each lake within the basin, that is, the impact of the increase in the lake inundation range on the suitability of species is the smallest, as shown in the following formula.

[0075]

[0076] In the formula, Area i is the area of the i-th lake within the basin; Area_Max i$A_{i}$ is the maximum area of the $i$-th lake in the current condition within the basin, that is, the lake area corresponding to the elevation of the overflow outlet; $N'$ is the number of lakes in the basin; $M$ is the number of species considered for suitability; Index$_{i,j}$ is the suitability index of the $j$-th species in the inundation impact area of the $i$-th lake.

[0077] Step 6, Optimization calculation of lake water storage: Use the water storage optimization model constructed in Step 5 for optimization calculation to obtain the optimized overflow elevation of each lake in the basin.

[0078] Example 1

[0079] This example is an application example of the above method.

[0080] This example discloses an optimization calculation method for the water storage of endorheic lakes considering flood control and ecological impacts, including the following steps:

[0081] Step 1, Analysis of lake water system connectivity: Collect DEM data, lake distribution data, and remote sensing image data of a certain endorheic river basin. Among them, the DEM data is as Figure 2 shown, the lake distribution data is as Figure 3 shown, and the remote sensing image data is as Figure 4 shown.

[0082] Based on the DEM data, extract the river network water system distribution of the basin, as Figure 5 shown; and according to the lake and water system distribution, analyze the connectivity between each lake, and make a generalized map of lake connectivity as Figure 6 shown. A total of 4 confluence paths are obtained, namely: a) Lake 2 - Confluence Path 1 - Lake 1; b) Confluence Path 2 - Lake 1; c) Lake 3 - Lake 4 - Confluence Path 3 - Lake 1; d) Lake 5 - Lake 6 - Lake 7 - Lake 8 - Lake 9 - Lake 10 - Lake 11 - Confluence Path 4 - Lake 1. It can be seen that each lake in the basin finally converges into Lake 1 through four confluence paths, and Lake 1 is the terminal lake of this basin.

[0083] Step 2, Analysis of lake water storage capacity: Analyze and obtain the water level - water storage relationship curve and water level - area relationship curve of 11 lakes in the basin, as Figures 7 to 17 shown.

[0084] Step 3, Construction of a distributed hydrological model: Construct a distributed hydrological model covering the entire basin. The model uses grid - type calculation units, and the entire basin is divided into 682 calculation grids, as Figure 18 shown.

[0085] Step 4. Construction and calculation of the integrated hydrological - water volume regulation model: According to the distribution of lake water systems in the basin, the inland river basin is divided into 16 runoff generation sub - regions, 3 sections are set, the topological relationships among the 16 runoff generation sub - regions, 11 lakes and 3 sections in the basin are analyzed, and a generalized map is made as shown in Figure 19 shown, and the correlation relationships among the runoff generation sub - regions, lakes and the calculation grids of the distributed hydrological model are analyzed, as shown in Figure 20 shown.

[0086] The generalized units of the basin are managed in the form of JSON objects as follows:

[0087]

[0088] The lake units are managed in the form of JSON objects as follows:

[0089]

[0090] The hydrological calculation results of the runoff generation sub - regions and lakes are calculated as follows:

[0091]

[0092] The calculation results of lake water storage regulation are calculated as follows:

[0093]

[0094] Step 5. Construction of the water storage optimization model: The optimization algorithm is combined with the integrated hydrological - water volume regulation model constructed in Step 4 to construct a water storage optimization model. To consider the impact of lake regulation on the ecosystem, a suitability index attribute is added to the lake units, and the suitability of two types of species is considered as follows:

[0095]

[0096] Step 6. Optimization calculation of lake water storage: After performing optimization calculations using the water storage optimization model constructed in Step 5, the overflow elevations of each lake are obtained as shown in Table 1. It can be seen that by building water retaining projects on Lake 8 and Lake 11, raising the overflow elevations by 1.2 m and 3 m respectively, the goal of preventing the tail - end lake in the basin from overflowing through upstream water volume regulation and minimizing the impact on the ecosystem can be achieved.

[0097] Table 1 Calculation results of the overflow elevations of each lake

[0098] Lake Name Overflow Elevation (m) Optimized Overflow Elevation (m) Height Increase of Overflow Outlet (m) Lake 5 4828 4828 0 Lake 6 4804 4804 0 Lake 7 4799 4799 0 Lake 8 4647 4648.2 1.2 Lake 9 4646 4646 0 Lake 10 4551 4551 0 Lake 11 4550 4553 3.0 Lake 3 4672 4672 0 Lake 4 4561 4561 0 Lake 2 4663 4663 0 Lake 1 4544.64 4544.64 0

[0099] Finally, it should be noted that the above is only used to illustrate the technical solution of the present invention and not to limit it. Although the present invention has been described in detail with reference to the preferred arrangement, those of ordinary skill in the art should understand that the technical solution of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. An optimized calculation method for the water storage of inland lakes considering flood control and ecological impacts, characterized in that The method includes the following steps: Step 1, Lake water system connectivity analysis: Collect DEM data, lake distribution data, and remote sensing image data of the target basin; based on the collected DEM data, obtain the river network water system distribution of the target basin through depression filling, flow direction analysis, flow calculation, and river network water system extraction; based on the collected lake distribution data, compare and verify it with the collected remote sensing image data to determine the lake depression distribution in the target basin; according to the river network water system distribution and lake depression distribution of the target basin, analyze the connectivity of lakes, make a generalized map of lake connectivity, and determine the confluence path of each lake in the target basin. Step 2, Lake water storage capacity analysis: Based on the collected remote sensing image data, analyze the lake surface area at different time points, and form a sequence according to the area size, denoted as A_list = [A1, A2,..., A i ,..., A N , with a total of N data, where A i is the lake surface area at the i-th moment; based on the collected DEM data, obtain the lake water levels corresponding to each time point, and form a water level sequence corresponding to the area sequence, denoted as H_list = [H1, H2,..., H i ,..., H N , with a total of N data, where H i is the lake water level at the i-th moment; according to the water level and area data at different time points, use the volume calculation formula of a frustum of a pyramid to estimate the difference in water storage capacity, and form a water storage capacity sequence corresponding to the area sequence, denoted as R_list = [V1, V1 + ΔV2,..., V i-1 +ΔV i ,..., V N-1 +ΔV N , with a total of N data, where V1 is the initial reservoir capacity, and when A1 is 0, V1 is equal to 0, and ΔV i is the difference in water storage capacity between the i-th and the (i - 1)-th values, and the calculation formula is: Among them, A i is the lake surface area at the i-th moment, and H i is the lake water level at the i-th moment; According to the obtained area sequence, water level sequence, and water storage sequence, fit the water level-water storage relationship curve and water level-area relationship curve, where the lake surface area corresponding to the lake bottom water level is 0 and the lake water storage is 0. Step 3, Distributed hydrological model construction: Construct a distributed hydrological model, which features grid-type calculation units, and the calculation grid can cover the entire basin; the model is constructed based on the water balance and energy balance equations, comprehensively considering the interactions of climate, terrain, soil properties, and vegetation, and supports confluence calculation. The hydrometeorological elements that can be calculated in the model include at least precipitation, ground evapotranspiration, water surface evaporation, surface runoff, and groundwater runoff. Step 4, Construction and calculation of the integrated hydrological-water volume regulation model: First, generalize the target basin into three types of units: runoff generation areas, lakes, and sections. On this basis, analyze the topological relationships of each unit in the basin and conduct the construction and calculation of the integrated hydrological-water volume regulation model, which specifically includes the following steps: Step 4-1, Construction of the integrated hydrological-water volume regulation model, including the following steps: Step 4-1-1, Based on the river network water system and lake depression distribution analyzed in Step 1, divide the target basin into different runoff generation areas, and the runoff of each runoff generation area unit flows into the lake or section unit, and make a generalized map of the basin unit topology. Step 4-1-2, Based on the confluence paths of each lake in the basin, associate each runoff generation area with the calculation grids divided in the distributed hydrological model in Step 3, and each runoff generation area is associated with several calculation grids. Step 4-1-3, Associate the lakes with the calculation grids divided in the distributed hydrological model in Step 3. The calculation grids covered by the lake water surface do not perform runoff generation and confluence calculations, and only rainfall and evaporation are considered. Step 4-1-4, Construct the basin topological relationship, which reflects the upstream and downstream relationships of each runoff generation area, lake, and section, and includes the association relationship between the generalized basin units and the calculation grids of the distributed hydrological model, and manage the basin topological relationship data in a JSON file. Step 4-1-5, Manage the characteristic data of each lake unit in the basin in a JSON file; the characteristic data of each lake unit includes name, water level curve, area curve, water storage curve, lake overflow outlet elevation, lake overflow outlet width, and initial water level elevation. Step 4-2, Calculate the integrated hydrological-water volume regulation model, including the following steps: Step 4-2-1, Use the distributed hydrological model to complete the simulation of the hydrological process of the entire basin for several years, and the time step output by the model is 1 day. Step 4-2-2: Read in the basin topological relationship data in Step 4-1-4 and the characteristic data of lake units in Step 4-1-5; Step 4-2-3: Based on the calculation results in Step 4-2-1, as well as the relationship between runoff generation areas, lakes and the computational grids of the distributed hydrological model, calculate the average monthly runoff of each runoff generation area over the years, and calculate the average monthly precipitation and evaporation of each lake over the years; Step 4-2-4: Conduct water storage and regulation calculations for each unit in the basin; According to the basin topological relationship, read the inflow data of each unit from upstream to downstream in sequence. If there are multiple upstream inflows, the flows are synthesized; For lake units, conduct storage and regulation calculations. According to the lake water level-storage capacity curve, as well as the bottom elevation and width of the overflow outlet, analyze the water storage capacity and discharge capacity of the lake, and calculate the average monthly inflow water volume, precipitation, evaporation, storage capacity, water level, and overflow discharge of each lake over the years. And according to the water level-area curve, calculate the change process of the lake water surface area; Step 4-2-5: Traverse all units in the basin to complete the calculation; Step 5: Construct a water storage optimization model: Combine an optimization algorithm with the hydrological-water volume scheduling integrated model constructed in Step 4 to construct a water storage optimization model; Step 6: Conduct optimization calculations for lake water storage: Use the water storage optimization model constructed in Step 5 to conduct optimization calculations to obtain the optimized overflow elevation of each lake in the basin.

2. The optimized calculation method for the water storage of an endorheic lake considering flood control and ecological impacts according to claim 1, wherein The specific process of managing the basin topological relationship data in Step 4-1-4 in a JSON file is as follows: Manage the generalized basin units in the form of JSON objects, and this object includes attributes such as "Name", "Id", "Type", "NextId", and "Grid"; Among them, the "Name" attribute stores the name of the unit; the "Id" attribute stores the encoding of the unit, and this encoding is unique among all units; the "Type" attribute stores the type of the unit, the runoff generation and confluence unit is "Watershed", the lake unit is "Reservoir", and the cross-section unit is "Section"; the "NextId" attribute stores the encoding of the downstream unit of this unit, and this encoding is the "Id" of the first downstream unit of this unit according to the basin topological relationship. When this unit is the most downstream unit in the basin topological relationship, that is, the terminal lake, "NextId" is -1; When this unit is of the runoff generation area or lake type, it includes the "Grid" attribute, and "Grid" is of array type, storing the numbers of the computational grids associated with this unit in the distributed hydrological model.

3. The optimized calculation method for the water storage of an endorheic lake considering flood control and ecological impacts according to claim 1, wherein The specific process of managing the characteristic data of each lake unit in the basin in JSON files as described in Step 4-1-5 is as follows: The lake units are managed in the form of JSON objects, and the object includes attributes of "Name", "H_list", "A_list", "R_list", "E", "B", and "E_ini"; among them, the "Name" attribute stores the name of the unit; the "H_list" attribute stores the water level curve obtained in Step 2; the "A_list" attribute stores the area curve obtained in Step 2; the "R_list" attribute stores the water storage curve obtained in Step 2; the "E" attribute stores the elevation of the lake overflow outlet; the "B" attribute stores the width of the lake overflow outlet; and the "E_ini" attribute stores the initial water level elevation for lake regulation calculation.

4. A method for optimizing the calculation of the water storage of an endorheic lake considering flood control and ecological impacts according to claim 1, characterized in that, The optimization algorithms adopted in Step 5 are genetic algorithm, particle swarm algorithm, or SCE-UA algorithm.

5. The optimized calculation method for the water storage of an endorheic lake considering flood control and ecological impacts according to claim 2, characterized in that, The optimization variables of the water storage optimization model constructed in Step 5 are the elevations of the overflow outlets of lakes other than the tail lake in the basin, and the variable range is set from the current overflow outlet elevation to the top elevation of the drainage project within the engineering feasibility range; Set the constraint condition of the water storage optimization model as that the water level of the tail lake does not exceed the overflow water level; Add the suitability index attribute of animals and plants in the inundation impact area of the lake to the lake unit in Step 4-1-4, and name the different suitability indices of animals and plants as "Index_1, Index_2,..." in sequence, and the value range is 0 to 1, where 1 represents the strongest suitability; Set the optimization objective function of the water storage optimization model as the minimum weighted sum of the suitability indices of the relative areas of lakes in the basin, that is, the impact of the increase in the lake inundation range on the suitability of species is the smallest, as shown in the following formula: In the formula, Area i is the area of the i-th lake in the basin; Area_Max i is the maximum area of the i-th lake under the current conditions in the basin, that is, the lake area corresponding to the elevation of the overflow outlet; N' is the number of lakes in the basin; M is the number of species considered for suitability; Index_i_j is the suitability index of the j-th species in the inundation impact area of the i-th lake.

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