A green small hydropower optimization planning method

Abstract

The present application belongs to the technical field of green hydropower planning, and discloses a green small hydropower optimization planning method, which comprises potential assessment, index system establishment, site selection planning, river connectivity index calculation and site selection evaluation, wherein the site selection planning comprises basin terrain data analysis, hydrological model calculation, small hydropower dam axis position search, small hydropower plant position search and small hydropower development mode discrimination. The present application establishes a systematic and comprehensive basin small hydropower optimization planning method system, covering the complete steps of the whole planning research of "basin small hydropower development potential assessment-green small hydropower index system establishment-small hydropower site selection planning search-river connectivity index calculation-site selection evaluation", which can be operated in a process.

Description

Technical Field

[0001] This invention belongs to the field of green hydropower planning technology, specifically a green small hydropower optimization planning method. Background Technology

[0002] Small hydropower stations, as a technologically mature clean and renewable energy source, have the characteristics of low investment, short cycle, and quick results. They can effectively solve the electricity problem for the population in areas without or lacking electricity, promote rural economic and social development, improve infrastructure construction in remote areas, and reduce firewood logging in the small hydropower supply area, thereby reducing the consumption of traditional fuels such as coal and straw.

[0003] However, the planning areas for small hydropower projects are mostly located in regions lacking actual measurement data, posing significant challenges in geological surveys, hydrological monitoring, site selection, and installed capacity planning. With the advancement of the strategy for sustainable and green development of hydropower, the planning of small hydropower projects must not only consider the economic aspects of power station utilization, regional electricity load, and construction investment costs, but also comprehensively plan at the watershed scale, taking into account ecological environmental protection, fuel efficiency (replacing firewood with diesel), and greenhouse gas emission reduction benefits.

[0004] Current watershed small hydropower planning and development technologies suffer from the following shortcomings: a lack of comprehensive assessment of the development potential of small hydropower at the watershed level; difficulty in quickly and efficiently selecting locations for potential small hydropower stations in the watershed; a lack of consideration for the impact of minimum downstream ecological flow of hydropower stations and cascade development on river connectivity; and a lack of a complete indicator system for evaluating and selecting the best planning schemes. Summary of the Invention

[0005] The purpose of this invention is to provide a green small hydropower optimization planning method to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a green small hydropower optimization planning method, including potential assessment, indicator system establishment, site selection planning, river connectivity index calculation and site selection evaluation. The site selection planning includes watershed topographic data analysis, hydrological model calculation, small hydropower dam axis location search, small hydropower plant location search and small hydropower development mode identification.

[0007] Preferably, the potential assessment includes the theoretical potential of river hydropower, the potential for installed capacity development, the potential for replacing firewood, and the potential for greenhouse gas emission reduction. The potential for greenhouse gas emission reduction includes the carbon emission reduction potential of reducing firewood consumption through electricity consumption replacing fuel and the emission reduction potential of replacing thermal power generation with surplus electricity from fuel replacement.

[0008] Preferably, the establishment of the indicator system includes the impact of multiple factors such as the ecological environment, power station economy, social benefits, and technical complexity, and a green small hydropower planning indicator system is constructed according to the hierarchical analysis method and the selection principles of scientificity, representativeness, and feasibility.

[0009]

[0010] Preferably, the watershed topographic data is analyzed by extracting the elevation points of each river from the watershed's DEM data as topographic input for power station planning, and extracting the environmentally sensitive areas for small hydropower development in the watershed based on the land use type map.

[0011] Preferably, the hydrological model calculation is performed using the three-source Xin'anjiang model, and evapotranspiration, runoff generation, water source differentiation, and confluence calculation are performed based on rainfall data from meteorological stations to derive long-sequence daily runoff data for watershed control hydrological points.

[0012] Preferably, the search for the axis position of the small hydropower dam involves using watershed topographic data and environmentally sensitive areas as input conditions. First, the dam axis position is searched on the developing river, and river grid points located outside the environmentally sensitive area are stored as the initial population for calculation.

[0013] Preferably, the small hydropower plant location search involves: further inputting river runoff data, using the maximum spacing between dam sites and powerhouses and the minimum downstream ecological flow of the power station as constraints, randomly searching for powerhouse locations, calculating the installed capacity of the power station as the environmental fitness of each dam axis group, applying a genetic algorithm to solve for the optimal powerhouse location corresponding to this dam axis location, dividing the river segment into upstream and downstream segments based on the obtained power station locations, and performing parallel cyclic calculations in segments to obtain the locations of power stations along the entire river.

[0014] Preferably, the small hydropower development mode determination involves further extracting the watershed contour lines and determining whether the power station is a diversion-type power station or a dam-type power station based on the catchment area and slope of the location of the power station dam axis.

[0015] Preferably, the river connectivity index is calculated to characterize the water system network in a topological network structure, and the overall connectivity index of the river network and the node connectivity probability are analyzed based on graph theory methods.

[0016]

[0017] In the formula, PC is the river network connectivity index, a i and a j Let A represent the lengths of river chains i and j, respectively. L Indicates the total length of the river network. It represents the maximum probability product of all possible paths from river chain i to river chain j.

[0018] Preferably, the site selection evaluation is based on the green small hydropower planning index system. According to the actual situation of the study basin, the corresponding secondary indicators of the criteria layer are selected, and the expert scoring method is adopted to propose a strategy for the optimized layout and development of small hydropower in the basin based on the index system scores of potential power station sites.

[0019] The beneficial effects of this invention are as follows:

[0020] 1. This invention establishes a systematic and comprehensive method for optimizing the planning of small hydropower in a watershed, covering the complete steps of the entire planning research process, including "assessment of the development potential of small hydropower in a watershed, establishment of a green small hydropower indicator system, search for small hydropower site selection planning, calculation of river connectivity indicators, and evaluation of site selection". The process can be streamlined.

[0021] 2. In the assessment of the development potential of small hydropower in a watershed, this invention establishes a comprehensive development potential map of the watershed based on the theoretical reserves of hydropower, the development potential of installed capacity, the potential to replace fuel oil, and the potential to reduce greenhouse gas emissions. This map can clearly show the priority areas for the development of small hydropower in the watershed.

[0022] 3. This invention considers various factors such as ecological environment, power station economy, and social benefits in the green small hydropower indicator system, and establishes a scientific and comprehensive evaluation indicator system to facilitate the evaluation of the feasibility of small hydropower planning.

[0023] 4. In the small hydropower site selection and planning search stage, this invention uses high-precision remote sensing image data and geographic information technology and intelligent optimization algorithms to quickly identify potential development sites for small hydropower in a watershed.

[0024] 5. In the process of calculating river connectivity indicators, this invention uses graph theory to analyze the overall connectivity indicators and node connectivity probabilities of the river network after the planning and development of small hydropower projects, and quantitatively assesses the differences in river connectivity under different planning schemes. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the small hydropower site selection and planning search process of the present invention;

[0026] Figure 2 This is a schematic diagram of the abstract topology of the water system network of the present invention;

[0027] Figure 3 This is a schematic diagram illustrating the assessment results of the installed capacity development potential, fuel-fired power generation potential, greenhouse gas emission reduction benefits, and comprehensive development potential of small hydropower development in a certain river basin according to the present invention.

[0028] Figure 4 This is a schematic diagram of the river section small hydropower station location search process of the present invention;

[0029] Figure 5This is a schematic diagram showing the location of potential dam sites for small hydropower development in a certain river basin according to the present invention;

[0030] Figure 6 This is a schematic diagram illustrating the impact of potential power station locations in a certain watershed on river network connectivity.

[0031] Figure 7 This is a heat map illustrating the scoring of the potential power station location index system in a certain watershed according to the present invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] like Figure 1 As shown, on a given river section, an initialization group is generated based on the initial proposed dam site location, water catchment drop, and other parameters. It is then determined whether the group is located within the watershed sensitive protection zone. If so, the power station location parameters are re-initialized; otherwise, the next step is performed.

[0034] Using the initial power station location as the center and the maximum water diversion length as the powerhouse search radius, the runoff data simulated by the hydrological model is input. Based on constraints such as the small hydropower water diversion length constraint and water diversion flow constraint, the installed capacity of each location is calculated as the fitness function. The genetic algorithm is then called to determine the optimal power station parameters at the initial location.

[0035] Using the dam site and powerhouse location at the current power station location as upper and lower boundary conditions, the river is divided into upstream and downstream segments. It is determined whether the segment length exceeds the minimum diversion length. If so, the initial segment range is updated, and the search process for the next power station location is executed; otherwise, the search for this segment ends. The two upstream segments are searched in parallel until the search of the entire river is completed.

[0036] like Figures 1 to 7 As shown, this embodiment of the invention provides a green small hydropower optimization planning method, including potential assessment, indicator system establishment, site selection planning, river connectivity index calculation and site selection evaluation. The site selection planning includes watershed topographic data analysis, hydrological model calculation, small hydropower dam axis location search, small hydropower plant location search and small hydropower development mode discrimination.

[0037] This approach streamlines the entire planning and research process by encompassing "basin small hydropower development potential assessment - establishment of a green small hydropower indicator system - small hydropower site selection and planning search - river connectivity index calculation - site selection evaluation," making it more user-friendly. Specifically, potential assessment helps identify priority areas for small hydropower development within the basin. The establishment of a comprehensive and scientific evaluation indicator system facilitates the assessment of the feasibility of small hydropower planning. The site selection planning and search phase then identifies potential development sites within the basin. Finally, river connectivity indicators are used to calculate the overall connectivity index of the developed river network and the probability of node connectivity, enabling the evaluation of differences in river connectivity under different planning schemes. Note: The small hydropower site selection and planning search process is as follows... Figure 1 As shown.

[0038] The potential assessment includes the theoretical potential of river hydropower, the potential for installed capacity development, the potential for replacing fuel oil, and the potential for greenhouse gas emission reduction. The greenhouse gas emission reduction potential includes the carbon emission reduction potential of reducing fuel oil consumption by replacing fuel oil with electricity and the emission reduction potential of replacing thermal power generation with surplus electricity from fuel oil.

[0039] For example, when calculating the theoretical hydropower potential of a river basin, the basin is divided into calculation segments according to the inflow of tributaries. The flow rate is taken as the average of the flow rates at the beginning and end of the cross-section. The hydropower output is calculated segment by segment based on the multi-year average flow rate, and then the total hydropower potential of the entire river is obtained by accumulating the values ​​of each segment. Based on the analysis of the geographical environment, geological conditions, flow rate, and riverbed drop of the power station location, the installed capacity development potential of small hydropower stations in the basin is determined. Then, based on the basin's development level, the amount of firewood consumption reduced by the electricity consumption of fuel-substitute equipment is calculated according to the capacity, usage time, number of fuel-substitute users, and average annual firewood consumption of fuel-substitute users, thus determining the fuel-substitute potential of the hydropower stations in the basin. This facilitates the calculation of the greenhouse gas emission reduction potential of small hydropower stations in the basin based on the carbon emission reduction benefits of reduced firewood consumption from fuel-substitute electricity consumption and the emission reduction benefits of replacing thermal power generation with surplus fuel-substitute electricity. A comprehensive development potential map of the basin is then established based on the above results. The evaluation results of the fuel-substitute potential, carbon emission reduction benefits, emission reduction benefits, and comprehensive development potential of the hydropower stations in the basin are as follows: Figure 3 As shown.

[0040] The establishment of the indicator system includes the impact of various factors such as the ecological environment, power station economy, social benefits, and technical complexity. In accordance with the hierarchical analysis method and the selection principles of scientificity, representativeness, and feasibility, a green small hydropower planning indicator system was constructed.

[0041]

[0042]

[0043] Among them, the watershed topographic data: the elevation points of each river are extracted from the watershed DEM data as the topographic input for power station planning, and the environmentally sensitive areas for small hydropower development in the watershed are extracted from the land use type map.

[0044] Then, high-precision remote sensing imagery was used to extract digital elevation data (DEM) of a watershed. Based on the DEM data, topographic surface parameters (elevation, elevation difference, distance, slope, aspect, curvature, etc.) and topographic morphological features (mountain peaks, depressions, ridgelines, valley lines, watershed extent, etc.) were extracted. Runoff simulation was used to extract the watershed's river network, obtaining the elevation data along the course of each river in the watershed. Land use maps were drawn based on Sentinel-2 satellite remote sensing imagery data, and environmentally sensitive areas were delineated according to special protected areas, ecologically sensitive and vulnerable areas, and areas of social concern within the study area.

[0045] Among them, the hydrological model calculation: the Xin'anjiang model with three water sources is adopted. Based on the rainfall data of the meteorological station, evapotranspiration calculation, runoff generation calculation, water source calculation and confluence calculation are carried out to derive the long-sequence daily runoff data of the watershed control hydrological points.

[0046] Using the Xin'anjiang hydrological model with three water sources, the study basin is divided into multiple unit basins. Runoff generation and runoff calculations are performed for each unit basin to obtain its outflow process. Flood calculations are then performed downstream of the outflow to obtain the basin's overall flow process. Summing the outflow processes of each unit basin yields the total outflow process at the basin's outlet. To estimate the flow at points along each tributary, several confluence points are added along each tributary. Assuming that the ratio of the sub-basin flow to the basin's total flow is proportional to the ratio of the sub-basin area to the total basin area, the flow process along each tributary is estimated using piecewise linear interpolation based on the outflow processes at the outlets of each unit basin.

[0047] Among them, the search for the axis location of small hydropower dams: using watershed topographic data and environmentally sensitive areas as input conditions, the dam axis location is first searched on the developed river, and the river grid points located outside the environmentally sensitive area are stored as the initial population for calculation.

[0048] On a given river segment, an initial population is generated based on parameters such as the initial proposed site location and catchment drop. It is then determined whether the population is located within an environmentally sensitive area. If so, the power plant parameters are reinitialized; otherwise, the process continues. Starting from the initial proposed site location, each river grid point is used as a site analysis search point along the river's flow direction. All river grids are searched sequentially according to their river codes. Simultaneously, the constraint condition for each search point is evaluated based on the distribution of environmentally sensitive areas within the region. If the point is not located within an environmentally sensitive area, its location is stored, and a search for the power plant location is initiated.

[0049] Among them, the search for the location of small hydropower plants involves further inputting river runoff data, using the maximum spacing between dam sites and power plants and the minimum downstream ecological flow of the power station as constraints, randomly searching for power plant locations, calculating the installed capacity of the power station as the environmental fitness of each dam axis group, applying a genetic algorithm to solve for the optimal power plant location corresponding to this dam axis location, dividing the river segment into upstream and downstream segments according to the obtained power station locations, and performing parallel cyclic calculations in segments to obtain the locations of power stations on the entire river.

[0050] Based on the stored Euclidean distance map between the dam axis location grid and its downstream river segment, the model searches for neighboring river grids within the maximum water diversion range from the initial dam axis location to determine the location of the hydropower plant. Inputting runoff data simulated by the hydrological model, and based on the search results for the dam axis location and power plant location, combined with constraints at various levels of small hydropower planning, the model calculates the installed capacity of the planned power plant at this location. A genetic algorithm is then used, with the calculation results as the parent population, to solve for the optimal small hydropower site in the basin through genetic operator operations. After determining the initial site location optimization results, the model divides the river into upstream and downstream segments, using the current planned power plant's dam axis and power plant location as upper and lower boundaries. The genetic algorithm is then applied to each segment to search for the power plant location in parallel. At the end of each segment's search, two new search segments are generated. The process ends when the search exceeds the river length limit or fails to meet the minimum water diversion length constraint. This cycle continues until the entire planned river segment is searched, obtaining the Pareto optimal solution set for the small hydropower site in the planned river segment. The river segment search diagram is shown below. Figure 5 As shown.

[0051] Among them, the development mode of small hydropower is determined by extracting the topographic contour lines of the watershed and determining whether the power station is a diversion power station or a dam power station based on the catchment area and slope of the location of the dam axis.

[0052] For power stations with large catchment areas and gentle slopes, dam-type development is selected. A dam is constructed at the initially proposed site to raise the upstream water level. The dam height and width are determined based on the reservoir topography, and the reservoir capacity is determined based on the dam height and catchment area DEM data. For power stations with smaller catchment areas and steeper slopes, diversion-type development is selected. The layout is simplified to an intake-diversion channel-power plant configuration. The dam axis will serve as the intake channel, and the line connecting the intake to the power plant will be the diversion channel. This yields the potential dam site locations for small hydropower development in the basin. The potential dam site locations for a specific basin are as follows: Figure 6 As shown.

[0053] The river connectivity index is calculated by representing the river network using a topological network structure. Graph theory methods are used to analyze the overall river network connectivity index and node connectivity probabilities. Note: The river network and the overall river network connectivity index and node connectivity probabilities are as follows: Figure 2 As shown;

[0054]

[0055] In the formula, PC is the river network connectivity index, a i and a j Let A represent the lengths of river chains i and j, respectively. L Indicates the total length of the river network. It represents the maximum probability product of all possible paths from river chain i to river chain j.

[0056] Then, based on the graph theory model, topological coding was performed on all potential power station locations and river endpoints and confluences in a certain watershed. The planned rivers in the watershed were abstracted into a directed river network graph model. The river network graph was divided into 102 river segments by a total of 103 nodes, including power stations and nodes.

[0057] The longitudinal connectivity of the main stream and tributaries is calculated using the connectivity PC index:

[0058]

[0059] The PC value mainly considers the position of the dam in the river network. The capacity of a single power station is defined as [0, 1]. Considering that small hydropower stations are mostly low dams or weirs, their impact on the river channel capacity is relatively small. The capacity of all power stations in the river network is defined as 0.8. The capacity of the confluence node of the main stream and the endpoint of the tributary is defined as 1. The overall connectivity of the river network and the connectivity of each tributary are calculated.

[0060] Once all 91 potential power stations are completed, the overall connectivity PC value of the river network in this basin will be 26.8, the overall connectivity value of the main stream will be 100, and the connectivity PC values ​​of the remaining tributaries are shown in the table below.

[0061] PC index of overall connectivity of river network and tributaries in a certain watershed after the construction of power stations at potential sites

[0062]

[0063]

[0064] The calculation of the overall connectivity of the river network after the construction of a power station at each location is performed by sequentially removing the engineering dams and replacing them with complete river channel nodes. The change in the overall connectivity of the river network after each removal is calculated as dPC, which can be used to evaluate the contribution of each node to the connectivity of the river network.

[0065]

[0066] A higher dPC value indicates that constructing a hydropower station at that location is more detrimental to the overall connectivity of the river network. The dPC values ​​for the 91 potential power stations obtained using the above method... Figure 6 As shown.

[0067] Among them, the site selection evaluation is based on the green small hydropower planning index system. According to the actual situation of the study watershed, the corresponding secondary indicators of the criteria layer are selected, and the expert scoring method is adopted. Based on the index system scores of potential power station sites, strategies for optimizing the layout and development of small hydropower in the watershed are proposed.

[0068] Then, considering the actual situation of a certain watershed, appropriate evaluation indicators are selected. The weight coefficients of each indicator are calculated by the expert scoring entropy weight method and the comprehensive weight method. The feasibility index of green small hydropower development is obtained by combining the sub-objective values ​​and sub-objective weights. Based on the weighted feasibility index of each potential small hydropower station site, the planning scheme for green small hydropower in the watershed is determined.

[0069]

[0070] Finally, based on the calculation results of the green small hydropower planning index system, the top 10 power stations ranked in the index system score were selected as the priority planning and layout schemes. The heat map of the total score of potential power station locations obtained by the above method is shown below. Figure 7 As shown.

[0071] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0072] 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. A method for optimizing the planning of green small hydropower projects, comprising the following steps: S1: Potential assessment, the indicators of which include the theoretical potential of river hydropower, the potential for development of installed capacity, the potential for replacing firewood and diesel, and the potential for greenhouse gas emission reduction, wherein the potential for greenhouse gas emission reduction includes the carbon emission reduction potential of reducing firewood consumption by replacing fuel electricity and the emission reduction potential of replacing thermal power generation with surplus fuel electricity. S2: Establishment of indicator system. Taking into account the influence of multiple factors such as ecological environment, power station economy, social benefits, and technical complexity, a green small hydropower planning indicator system is constructed according to the hierarchical analysis method and the selection principles of scientificity, representativeness and feasibility. S3: Site selection planning, specifically including: S3-1 Watershed Topographic Data Analysis: Based on the watershed river system DEM data, the elevation points of each river are extracted as topographic input for power station planning. Based on the land use type map, the environmentally sensitive areas for small hydropower development in this watershed are extracted. S3-2 Hydrological Model Calculation: Establish the corresponding watershed river system model, and perform evapotranspiration calculation, runoff generation calculation, water source calculation and confluence calculation based on meteorological station rainfall data to derive long-sequence daily runoff data of watershed control hydrological points; S3-3 Small Hydropower Dam Axis Location Search: Using watershed topographic data and environmentally sensitive areas as input conditions, the dam axis location is first searched on the developed river, and the river grid points located outside the environmentally sensitive area are stored as the initial population for calculation. S3-4 Small Hydropower Plant Location Search: Input river runoff data, use the maximum spacing between dam sites and powerhouses and the minimum downstream ecological flow of the power station as constraints, randomly search for powerhouse locations, calculate the installed capacity of the power station as the environmental fitness of each dam axis group, apply a genetic algorithm to solve for the optimal powerhouse location corresponding to this dam axis location, divide the river segment into upstream and downstream segments according to the obtained power station locations, and perform parallel cyclic calculations in segments to obtain the locations of power stations on the entire river. S3-5 Identification of Small Hydropower Development Method: Extract the topographic contour lines of the watershed, and determine whether the power station is a diversion-type power station or a dam-type power station based on the catchment area and slope of the location of the power station dam axis. S4: River connectivity index calculation and site selection evaluation, wherein the river connectivity index calculation represents the river network in a topological network structure, and analyzes the overall connectivity index and node connectivity probability of the river network based on graph theory methods, using the following formula to calculate the river network connectivity index PC: PC=(Σ(i=1→n) Σ(j=1→n) a i ·a j ·p ij ) / A_L² In the formula, PC is the river network connectivity index, a i and a j Let p represent the lengths of river chain i and river chain j, respectively, and let A_L represent the total length of the river network. ij It represents the maximum probability product of all possible paths from river chain i to river chain j; the site selection evaluation is based on the green small hydropower planning index system. According to the actual situation of the study basin, the corresponding secondary indicators of the criterion layer are selected, and the expert scoring method is adopted. Based on the index system scores of potential power station sites, a strategy for optimizing the layout and development of small hydropower in the basin is proposed.

2. The green small hydropower optimization planning method according to claim 1, characterized in that: In step S1, the potential for replacing firewood with fuel is calculated based on the capacity of the fuel replacement equipment, the usage time, the number of fuel replacement users, and the average annual amount of firewood burned by fuel replacement users; the potential for greenhouse gas emission reduction is calculated based on the carbon emission reduction benefits of small hydropower's electricity consumption replacing firewood consumption and the emission reduction benefits of surplus electricity from fuel replacement replacing thermal power generation.

3. The green small hydropower optimization planning method according to claim 1, characterized in that: The green small hydropower planning indicator system constructed in step S2 includes a target layer, a criterion layer, and an indicator layer. The target layer is green small hydropower planning, the criterion layer includes ecological environment, power station economy, social benefits, and technical complexity, and the indicator layer includes primary indicators and secondary indicators.

4. The green small hydropower optimization planning method according to claim 1, characterized in that: In step S3-1, a land use map is drawn based on the Sentinel-2 satellite remote sensing image data, and the environmentally sensitive areas are divided according to the special protection areas, ecologically sensitive and fragile areas and areas of social concern in the study area.

5. The green small hydropower optimization planning method according to claim 1, characterized in that: In step S3-2, the hydrological model adopts the Xin'anjiang Three-Source Model, which divides the study basin into multiple unit basins. For each unit basin, runoff generation and runoff calculations are performed to obtain the outflow process of the unit basin. Then, the river flood calculations below the outflow are performed to obtain the flow process of the basin.

6. The green small hydropower optimization planning method according to claim 1, characterized in that: In step S3-3, on a given river section, an initial group is generated based on the initial proposed dam site location and water drop parameters. It is then determined whether the group is located within an environmentally sensitive area. If so, the power station parameters are re-initialized; otherwise, the location is stored and a search for the power plant location is performed.

7. The green small hydropower optimization planning method according to claim 1, characterized in that: In step S3-4, the segmented parallel cyclic calculation to obtain the location of the power station on the entire river is specifically as follows: taking the dam site and powerhouse location of the current power station location as the upper and lower boundaries, the river is divided into an upstream segment and a downstream segment. The genetic algorithm is then applied to each segment to search for the location of the power station in parallel. When the search of each segment ends, two new search segments will be generated. The operation ends when the river length is exceeded or the minimum water diversion length limit is not met. This cycle continues until the entire planned river segment is searched, and the Pareto optimal solution set of the small hydropower station locations in the planned river segment is obtained.

8. The green small hydropower optimization planning method according to claim 1, characterized in that: In steps S3-5, a site with a large catchment area and a gentle slope is selected as a dam-type power station. A dam is built at the proposed site to raise the upstream water level. The dam height and width are determined based on the reservoir topography. The reservoir capacity is determined based on the dam height and catchment area DEM data. A site with a small catchment area and a gentle slope is selected as a diversion-type hydropower station. The layout is in the form of water intake-diversion channel-power plant. The dam axis is used as the water intake channel, and the line connecting the water intake to the power plant is the diversion channel.

9. The green small hydropower optimization planning method according to claim 1, characterized in that: In step S4, the throughput capacity of a single power station is defined as 0 to 1. Considering that small hydropower stations are mostly low dams or weirs, the throughput capacity of all power stations in the river network is defined as 0.8, and the throughput capacity of the confluence node of the main stream and the endpoint of the tributary is defined as 1. By removing the engineering dams one by one and replacing them with complete river nodes, the degree of change in the overall connectivity of the river network after each removal is calculated as dPC, and the contribution of each node to the connectivity of the river network is evaluated. In this formula, dPC = 100 × (PC - PC_remove) / PC, where PC is the connectivity index of the river network before removal, and PC_remove is the connectivity index of the river network after removal, that is, the river network connectivity index recalculated after removing each engineering dam and replacing it with a complete river node.

10. The green small hydropower optimization planning method according to claim 1, characterized in that: In step S4, the site selection evaluation uses the expert scoring entropy weight method and the comprehensive weight method to calculate the weight coefficient of each indicator. The feasibility index of green small hydropower development is obtained by combining the sub-objective value and the sub-objective weight. Based on the value of the weighted feasibility index of each potential small hydropower station site, the planning scheme of green small hydropower in the basin is determined, and the power station with the highest weighted feasibility index is selected as the priority planning and layout scheme.

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