A directed graph-based method and system for evaluating the development of cascade reservoirs in a river basin

Abstract

The present invention relates to the technical field of hydrological data analysis, and proposes a method and system for evaluating the development of cascade reservoirs in a watershed based on a directed graph, which comprises the following steps: obtaining digital elevation model data, location data of a controlling hydrological station in a watershed and location data of cascade reservoirs as input data, and constructing a watershed directed graph based on the input data; obtaining the scope of a development evaluation area of ​​cascade reservoirs according to the input data; performing position correction on any one of the reservoirs in the watershed directed graph based on the scope of the development evaluation area of ​​cascade reservoirs; and calculating the flow distance between each pixel in the watershed directed graph, the drop and flow distance between any two cascade reservoirs, and the catchment range and catchment interval of any cascade reservoir according to the position-corrected watershed directed graph, and combining the above data to perform a high-accuracy and efficient evaluation on the development of cascade reservoirs in the watershed.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrological data analysis, and more specifically, to a method and system for evaluating the development of cascade reservoirs in a watershed based on a directed graph. Background Art

[0002] Cascade reservoirs are a series of stepped reservoirs built from the upstream to the downstream of a river or river section in the water conservancy and hydropower development planning of a river in order to make full use of water resources. The development planning of cascade reservoirs is of great strategic significance for power generation, flood control, irrigation, urban and rural water supply, shipping and other issues. The height difference and flow distance of cascade reservoirs are directly related to the power generation efficiency of each reservoir, and the catchment range and confluence interval are related to the ecological benefits of the reservoir, which are all matters of great concern to reservoir managers.

[0003] Existing evaluation methods mainly build watershed network models and evaluate based on data such as the network water connectivity index (RCI). However, due to the complexity of cascade reservoir data, the data obtained from the digital elevation model has a certain deviation from the actual location of the cascade reservoirs, so errors are prone to occur when constructing the watershed network model. In addition, in actual work, the drop and confluence interval of cascade reservoirs often rely on manual determination, which is prone to errors when there are many cascades, making it difficult to obtain cascade reservoir development evaluation results with high accuracy and credibility. Summary of the invention

[0004] In order to overcome the defects of the above-mentioned prior art, namely, high error rate of cascade reservoir data and low accuracy of cascade reservoir development evaluation, the present invention provides a river basin cascade reservoir development evaluation method based on a directed graph, and a river basin cascade reservoir development evaluation system based on a directed graph.

[0005] In order to solve the above technical problems, the technical solution of the present invention is as follows:

[0006] A directed graph-based method for evaluating the development of cascade reservoirs in a watershed includes the following steps:

[0007] S1, obtaining digital elevation model data, basin control hydrological station location data and cascade reservoir location data as input data, and constructing a basin directed graph based on the input data;

[0008] S2. Obtaining the scope of the cascade reservoir development assessment area according to the input data;

[0009] S3, based on the scope of the cascade reservoir development assessment area, correct the position of any reservoir in the watershed directed graph;

[0010] S4. Based on the position-corrected watershed directed graph, calculate the flow distance between each pixel in the watershed directed graph, the drop and flow distance between any two cascade reservoirs, and the catchment range and catchment interval of any cascade reservoir to conduct a cascade reservoir development assessment.

[0011] This technical solution corrects the reservoir position on the basin directed graph constructed by digital elevation model data, basin control hydrological station location data and cascade reservoir location data, and then calculates the flow distance from each cascade reservoir to the basin outlet, the drop between two cascade reservoirs, the confluence interval and water collection range of the reservoir. Combining the above data, a high-accuracy and efficient evaluation of the development of cascade reservoirs in the basin can be carried out.

[0012] Furthermore, the present invention also proposes a watershed cascade reservoir development evaluation system based on directed graph, which applies the above-mentioned watershed cascade reservoir development evaluation method based on directed graph, including a data acquisition module, a watershed directed graph construction module, a regional scope calculation module, a correction module and an evaluation module.

[0013] Among them, the data acquisition module is used to obtain digital elevation model data, basin control hydrological station location data and cascade reservoir location data. The basin directed graph construction module is used to construct a basin directed graph based on the data collected by the data acquisition module. The regional scope calculation module is used to calculate the regional scope of cascade reservoir development assessment based on the data collected by the data acquisition module. The correction module is used to correct the positions of all reservoirs in the basin directed graph constructed by the basin directed graph construction module according to the regional scope of cascade reservoir development assessment. The evaluation module is used to calculate the flow distance between each pixel in the basin directed graph, the drop and flow distance between any two cascade reservoirs, and the catchment range and confluence interval of any cascade reservoir based on the basin directed graph corrected by the correction module, and output it as reference data for basin cascade reservoir development assessment.

[0014] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows: the present invention constructs a watershed directed graph based on digital elevation model data, watershed control hydrological station location data and cascade reservoir location data, and corrects the reservoir positions in the watershed directed graph based on the cascade reservoir development assessment area, which can avoid the impact of cascade reservoir data errors on the assessment results; the corrected watershed directed graph is used to quickly calculate the flow distance from each cascade reservoir to the watershed outlet, the drop between two cascade reservoirs, the confluence interval and water collection range of the reservoir, and the above data can be combined to conduct a high-accuracy and efficient assessment of the development of cascade reservoirs in the watershed. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a flow chart of the directed graph-based basin cascade reservoir development assessment method of Example 1.

[0016] Figure 2 This is a flow chart for correcting the position of any reservoir in the watershed directed graph in Example 2.

[0017] Figure 3 This is a pseudo code diagram of the algorithm for calculating flow distance in Example 2.

[0018] Figure 4 This is a schematic diagram of the original digital elevation model, the locations of the cascade reservoirs, and the location of the Gaoyao hydrological station in Example 3.

[0019] Figure 5 Schematic diagram of the method for saving the watershed directed graph in Example 3.

[0020] Figure 6 This is a schematic diagram of the flow distance in the Xijiang River Basin in Example 3.

[0021] Figure 7 This is a cross-sectional diagram of the development of the Hongshui River hydropower base in Example 3.

[0022] Figure 8 This is a schematic diagram of the catchment area of ​​the 8th-level Letan Reservoir in the Hongshui River Hydropower Base in Example 3.

[0023] Fig. 9 This is a schematic diagram of the confluence section of the 8th-level Letan Reservoir in the Hongshui River Hydropower Base in Example 3.

[0024] Fig.10 This is an architectural diagram of a directed graph-based watershed cascade reservoir development and evaluation system for Example 4. DETAILED DESCRIPTION

[0025] The drawings are for illustrative purposes only and should not be construed as limiting the present patent;

[0026] In order to better illustrate the present embodiment, some parts in the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product;

[0027] It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0028] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0029] Example 1

[0030] This embodiment proposes a basin cascade reservoir development evaluation method based on a directed graph, such as Figure 1 As shown, it is a flow chart of the basin cascade reservoir development assessment method based on directed graph of this embodiment.

[0031] The basin cascade reservoir development assessment method based on a directed graph proposed in this embodiment includes the following steps:

[0032] S1. Acquire digital elevation model data, location data of controlling hydrological stations in the watershed, and location data of cascade reservoirs as input data, and construct a watershed directed graph based on the input data.

[0033] The digital elevation model data in this embodiment includes geographic data information such as the longitude and latitude of the target watershed area, and is further combined with the location data of the basin's controlling hydrological stations and the cascade reservoirs to construct a watershed directed graph containing watershed water system location information, reservoir location information, basin outlet location information and other data for further evaluation of the development of cascade reservoirs in the basin.

[0034] S2. Obtaining the scope of the cascade reservoir development assessment area based on the input data.

[0035] In this embodiment, the scope of the cascade reservoir development assessment area is obtained based on the digital elevation model data. The scope of the cascade reservoir development assessment area is used to limit the scope of the watershed directed graph and to calculate the location coordinates of the cascade reservoirs.

[0036] S3. Based on the scope of the cascade reservoir development assessment area, the position of any reservoir in the basin directed graph is corrected.

[0037] This step corrects the position of any reservoir in the watershed directed graph based on the scope of the cascade reservoir development assessment area and the location coordinates of the cascade reservoirs calculated based on the scope of the cascade reservoir development assessment area, aiming to correct the deviation between the data obtained from the digital elevation model and the actual location of the cascade reservoirs.

[0038] S4. Based on the position-corrected watershed directed graph, calculate the flow distance between each pixel in the watershed directed graph, the drop and flow distance between any two cascade reservoirs, and the catchment range and catchment interval of any cascade reservoir to conduct a cascade reservoir development assessment.

[0039] This embodiment uses the flow distance between pixels obtained through the above calculation, the drop and flow distance between any two cascade reservoirs, and the catchment range and catchment interval of any cascade reservoir as evaluation reference data for cascade reservoir development evaluation.

[0040] This embodiment constructs a watershed directed graph based on digital elevation model data, basin control hydrological station location data and cascade reservoir location data, and corrects the reservoir positions in the watershed directed graph based on the cascade reservoir development assessment area, which can avoid the impact of cascade reservoir data errors on the assessment results; the corrected watershed directed graph is used to quickly calculate the flow distance from each cascade reservoir to the basin outlet, the drop between two cascade reservoirs, the confluence interval and water collection range of the reservoir, and the above data can be combined to conduct a high-accuracy and efficient assessment of the basin cascade reservoir development.

[0041] Example 2

[0042] This embodiment makes improvements on the directed graph-based watershed cascade reservoir development assessment method proposed in Embodiment 1.

[0043] The basin cascade reservoir development assessment method based on a directed graph proposed in this embodiment includes the following steps:

[0044] S1. Acquire digital elevation model data, location data of controlling hydrological stations in the watershed, and location data of cascade reservoirs as input data, and construct a watershed directed graph based on the input data.

[0045] In this step, the step of constructing a watershed directed graph based on the input data includes:

[0046] S1.1. Calculate the flow direction of the digital elevation model data to obtain the flow direction of each pixel in the digital elevation model, and extract the watershed system and its pixels through cumulative flow calculation;

[0047] S1.2. According to the flow direction of each pixel in the digital elevation model, a watershed directed graph is constructed with the pixels as nodes and the flow directions as edges, and the locations of the watershed controlling hydrological stations and the cascade reservoirs are marked in the watershed directed graph according to the location data of the watershed controlling hydrological stations and the cascade reservoirs.

[0048] S2. Obtaining the scope of the cascade reservoir development assessment area based on the input data.

[0049] In this step, the step of obtaining the scope of the cascade reservoir development assessment area according to the input data includes: extracting the input data using the GetGeoTransform function to obtain the starting longitude lon′0, the ending latitude lat′1, and the longitude resolution r of the digital elevation model data. lon and latitude resolution r lat , as well as the number of columns cols and rows rows of the digital elevation model data; calculate the scope of the cascade reservoir development assessment area based on the data extraction results of the input data.

[0050] Among them, the expression for calculating the scope of the cascade reservoir development assessment area based on the data extraction results of the input data is as follows:

[0051]

[0052] Where lon′1 represents the end longitude of the digital elevation model, and lat′0 represents the start latitude of the digital elevation model.

[0053] Therefore, the range of the cascade reservoir development assessment area is {lon′0,lat′0,lon′1,lat′1,cols,rows}.

[0054] S3. Based on the scope of the cascade reservoir development assessment area, the position of any reservoir in the basin directed graph is corrected.

[0055] In this step, the steps of correcting the position of any reservoir in the watershed directed graph include:

[0056] S3.1. According to the scope of the cascade reservoir development assessment area, the watershed system in the digital elevation model is converted into raster data, and the horizontal coordinates of m pixels in the watershed directed graph of the watershed system are obtained. x,j and the vertical axis river y,j , where j = 1, 2, ..., m, and m is the total number of pixels.

[0057] The water system data obtained through the digital elevation model is vector data, which needs to be converted into raster data first for subsequent position correction of cascade reservoirs.

[0058] S3.2. Calculate the horizontal and vertical coordinates of the pixels in the watershed directed graph of the digital elevation model of each reservoir to obtain the reservoir location coordinates; the expression is as follows:

[0059]

[0060] In the formula, row i represents the ordinate of the i-th reservoir, col i represents the horizontal coordinate of the i-th reservoir; lon i represents the longitude of the i-th reservoir, lat i Represents the latitude of the i-th reservoir; where i = 1, 2, ..., n, and n is the total number of reservoirs.

[0061] S3.3. For any reservoir, calculate the distance between the reservoir and all pixels in the watershed system in the watershed directed graph; the expression is as follows:

[0062]

[0063] Where, d i,j It represents the distance between the i-th reservoir and the j-th pixel in the basin water system in the basin directed graph.

[0064] S3.4. For any reservoir, based on the distance between the reservoir and all pixels in the watershed system in the watershed directed graph, the reservoir location coordinates are modified to the location coordinates of the watershed watershed pixel closest to it; the expression is as follows:

[0065]

[0066] In the formula, river y,j′ 、river x,j′ is the ordinate and abscissa of the pixel of the watershed closest to the i-th reservoir, row t,i 、col t,i Respectively represent the ordinate and abscissa of the ith reservoir after correction; d min is the shortest distance between the i-th reservoir and the pixels in the watershed system.

[0067] like Figure 2 As shown, this is a flow chart of the present implementation for correcting the position of any reservoir in a directed graph of a watershed.

[0068] This embodiment calculates the distance between any reservoir and the rasterized water system based on the scope of the cascade reservoir development assessment area and the location coordinates of the cascade reservoirs calculated based on the scope of the cascade reservoir development assessment area, and then moves it to the nearest river section to correct the position of the reservoir in the watershed directed graph, which can effectively avoid the data deviation of the directly acquired digital elevation data affecting the accuracy of the cascade reservoir development assessment.

[0069] Furthermore, in one embodiment, for convenient data storage, the watershed directed graph with corrected reservoir position coordinates is stored in a table format, and the coordinates of the cascade reservoirs are converted into numbers to query their upstream and downstream relationships with other pixels.

[0070] The coordinates of the cascade reservoirs are converted into numbers; the number of the i-th cascade reservoir is:

[0071] index i =row t,i rows+col t,i ;

[0072] The horizontal and vertical coordinates of all pixels in the watershed digraph are recorded with numbers. Then the numbers of each pixel are used as index columns of the watershed digraph table, and the upstream pixels of each pixel are used as data columns of the watershed digraph table to obtain and store the watershed digraph table.

[0073] S4. Based on the position-corrected watershed directed graph, calculate the flow distance between each pixel in the watershed directed graph, the drop and flow distance between any two cascade reservoirs, and the catchment range and catchment interval of any cascade reservoir to conduct a cascade reservoir development assessment.

[0074] Among them, when calculating the flow distance between each pixel in the watershed directed graph, the D8 algorithm is used to calculate the flow direction of each pixel in the watershed directed graph according to the preset flow direction to obtain the flow distance from any pixel to the next pixel.

[0075] In this embodiment, in the watershed directed graph, the pixel without downstream is defined as the exit pixel, and the flow distance of the exit pixel is defined as 0; the flow distance from any pixel to the exit pixel is calculated in the upstream direction from the exit pixel, and the expression is as follows:

[0076] dist upstream =dist downstream +d upstream

[0077] In the formula, dist upstream Indicates the flow distance from the current pixel to the exit pixel, dist downstream Indicates the flow distance from the downstream pixel of the current pixel to the exit pixel, d upstream Represents the flow distance from the current cell to its downstream cell.

[0078] like Figure 3 The figure shows a pseudo code diagram of the algorithm for calculating the flow distance in this embodiment.

[0079] In a specific implementation process, 8 flow directions are recorded with 64, 128, 1, 2, 4, 8, and 32 respectively: north, northeast, east, southeast, south, southwest, west, and northwest. For any two directly connected pixels, different flow directions have different flow distances. If the resolution of the digital elevation model is r, then the flow distance resolutions corresponding to the 8 directions of north, northeast, east, southeast, south, southwest, west, and northwest are r, respectively. r, r, r, Further, based on the flow direction of each pixel calculated in step S1.1, the D8 algorithm can be used to find the flow distance from any pixel to the next pixel.

[0080] Furthermore, considering that the original cascade reservoir location data only contains the latitude and longitude information of the reservoir, and there is no upstream and downstream topological relationship, this embodiment obtains the flow distance between any reservoir and the outlet pixel according to the flow distance between each pixel in the watershed directed graph, and sorts the flow distance between any reservoir and the outlet pixel to construct the cascade reservoir topological relationship, which can be used to query the flow distance from any reservoir to the outlet. The reservoir with a larger flow distance has a lower level and is located upstream.

[0081] When calculating the drop and flow distance between any two cascade reservoirs, the position coordinates of the cascade reservoirs are obtained from the position-corrected basin directed graph, and the elevation of each cascade reservoir is obtained based on the position coordinates of the cascade reservoirs and the digital elevation model to calculate the drop between any two cascade reservoirs.

[0082] The expression for the drop between any two cascade reservoirs is as follows:

[0083] Δh p =elev p -elev p+1

[0084] In the formula, Δh p Indicates the height difference of the p-th reservoir, elev p is the elevation of the p-th level reservoir.

[0085] Furthermore, the flow distance between any two cascade reservoirs is calculated based on the flow distance between each pixel in the watershed directed graph. The expression is as follows:

[0086] Δfd p =fd p -fd p+1

[0087] Where Δfd p represents the flow distance from the pth reservoir to the p+1th reservoir, fd p It represents the flow distance from the p-th reservoir to the basin outlet.

[0088] When calculating the catchment area and flow interval of any cascade reservoir, the reachability analysis is performed on the position-corrected watershed directed graph to obtain the catchment area of ​​any reservoir, wherein for any pixel j in the watershed directed graph, if there is a path connecting pixel j with the pixel where reservoir i is located, then pixel j belongs to the catchment area of ​​reservoir i.

[0089] The expression for pixel j belonging to the catchment area of ​​reservoir i is as follows:

[0090] D i ={pixel j |pixel j →pixel i}

[0091] Where D i is the catchment area of ​​reservoir i, pixel j Indicates the position of pixel j, pixel i represents the location of reservoir i.

[0092] Furthermore, the confluence interval of the reservoir is calculated according to its catchment range, and its expression is as follows:

[0093] A i+1 =D i+1 -D i

[0094] In the formula, A i+1 It is the confluence interval of the i+1th level reservoir, and the i+1th level reservoir is the direct downstream reservoir of the i-th level reservoir.

[0095] In another specific implementation process, by defining a class class and a function def(), steps S1 to S4 are encapsulated into multiple classes and functions, and the code is saved as a .py file. When conducting a cascade reservoir development assessment, the classes and functions can be used after being imported using the import statement.

[0096] Example 3

[0097] This embodiment applies the directed graph-based watershed cascade reservoir development assessment method proposed in Embodiment 1 or Embodiment 2 to conduct a watershed cascade reservoir development assessment on the Hongshui River Hydropower Base in the Xijiang River Basin of China.

[0098] The steps in this embodiment are analyzed as follows:

[0099] S1. Collect and store the digital elevation model required for the development and evaluation of the cascade reservoirs of the Hongshui River Hydropower Base in the Xijiang River Basin, the location data of the Gaoyao hydrological station, and the location data of the cascade reservoirs of the Hongshui River Hydropower Base.

[0100] This embodiment defines variables dem, station, and cascade_reservoirs to store corresponding file paths. The above data file is called by the d8flowdir function in pygeoc to calculate the digital elevation flow direction of the Xijiang River Basin and construct a directed graph of the basin.

[0101] like Figure 4 As shown in FIG. 1 , it is a schematic diagram of the original digital elevation model, the location of the cascade reservoirs, and the location of the Gaoyao hydrological station in this embodiment. And the watershed directed graph of this embodiment is saved as follows: Figure 5 shown.

[0102] S2. Use the Open function of gdal to read the digital elevation model data of the Xijiang River Basin and convert it into a Dataset object. Use the GetGeotransform method in the Dataset object to obtain the calculation range and scale in this calculation instance.

[0103] S3. Based on the scope of the cascade reservoir development assessment area, the position coordinates of any reservoir in the basin directed graph are corrected.

[0104] S3.1. Use the Rasterize function in gdal to rasterize the watershed system extracted above, and save the horizontal and vertical coordinates of the water system pixels respectively.

[0105] S3.2. Use the read_file function of GeoPandas to read the location data of the cascade reservoirs of the Hongshui River Hydropower Base, convert it into a GeoDataFrame object, and use the geometry.x and geometry.y methods to obtain the longitude and latitude of the reservoir. Based on the longitude and latitude and the digital elevation model data information obtained in the , calculate the pixel number of the reservoir in the digital elevation model.

[0106] S3.3. According to the principle of minimum distance, the position of the cascade reservoirs is corrected by calculating the distance between the cascade reservoirs of the Hongshui River Hydropower Base and the gridded Xijiang River Basin water system.

[0107] S4. Evaluation of cascade reservoir development.

[0108] S4.1. Using Python's for loop, we start from the outlet pixel of the Xijiang River Basin and iterate upstream to gradually calculate the flow distance from each pixel to the outlet of the basin. After calculation, we use the Python third-party library gdal to save it as a tiff file.

[0109] like Figure 6 As shown, it is a schematic diagram of the flow distance of the Xijiang River Basin in this embodiment.

[0110] S4.2. Use the sort function in Python to sort the cascade reservoirs of the Hongshui River according to the flow distance to obtain the connection relationship of the cascade reservoirs of the Hongshui River. The reservoir with a larger flow distance has a lower grade and is located upstream.

[0111] S4.3. For any level of reservoir in the Hongshui River Hydropower Base, the drop and flow distance between it and the next level of reservoir can be calculated. Figure 7 The figure shows a cross-sectional view of the development of the Hongshui River hydropower base in this embodiment.

[0112] S4.4. For any cascade reservoir, accessibility analysis is performed based on the directed graph of the watershed to calculate its catchment area and further calculate its catchment interval.

[0113] like Figure 8 , 9 As shown, they are schematic diagrams of the catchment range and the confluence interval of the 8th-level Letan Reservoir in the Hongshui River Hydropower Base of this embodiment.

[0114] Depend on Figures 6 to 9 It can be seen that the basin cascade reservoir development assessment method based on directed graph proposed in this embodiment can obtain cascade reservoir development assessment results with higher accuracy and credibility.

[0115] Example 4

[0116] This embodiment proposes a directed graph-based watershed cascade reservoir development assessment system, and applies the directed graph-based watershed cascade reservoir development assessment method proposed in Embodiment 1 or Embodiment 2. Fig.10 As shown, it is the architecture diagram of the watershed cascade reservoir development evaluation system based on directed graph of this embodiment.

[0117] The directed graph-based watershed cascade reservoir development assessment system proposed in this embodiment includes a data acquisition module 1, a watershed directed graph construction module 2, a regional range calculation module 3, a correction module 4 and an assessment module 5.

[0118] The data acquisition module 1 of this embodiment is used to obtain digital elevation model data, basin control hydrological station location data and cascade reservoir location data.

[0119] The watershed directed graph construction module 2 of this embodiment is used to construct a watershed directed graph according to the data collected by the data collection module 1 .

[0120] The regional scope calculation module 3 of this embodiment is used to calculate the regional scope of cascade reservoir development assessment based on the data collected by the data collection module 1.

[0121] The correction module 4 of this embodiment is used to correct the positions of all reservoirs in the watershed directed graph constructed by the watershed directed graph construction module 2 according to the scope of the cascade reservoir development assessment area.

[0122] The evaluation module 5 of this embodiment is used to calculate the flow distance between each pixel in the basin directed graph, the drop and flow distance between any two cascade reservoirs, and the water collection range and confluence interval of any cascade reservoir based on the basin directed graph corrected by the correction module 4, and output it as reference data for the development evaluation of cascade reservoirs in the basin.

[0123] In the specific implementation process, the digital elevation model data, the location data of the basin's controlling hydrological stations and the location data of the cascade reservoirs are obtained through the data acquisition module 1, and the data acquisition module 1 transmits the collected data to the basin directed graph construction module 2 and the regional range calculation module 3 respectively.

[0124] The watershed directed graph construction module 2 constructs a watershed directed graph according to the input data. Specifically, the watershed directed graph construction module 2 calculates the flow direction of the digital elevation model data to obtain the flow direction of each pixel in the digital elevation model, and extracts the watershed water system and its pixels through cumulative flow calculation, and then constructs a watershed directed graph according to the flow direction of each pixel in the digital elevation model, with the pixel as the node and the flow direction as the edge, and marks the watershed controlled hydrological station location and the cascade reservoir location in the watershed directed graph according to the watershed controlled hydrological station location data and the cascade reservoir location data. The watershed directed graph construction module 2 sends the generated watershed directed graph to the correction module 4.

[0125] The regional range calculation module 3 obtains the regional range of the cascade reservoir development assessment based on the input data. Specifically, the input data is extracted using the GetGeoTransform function to obtain the starting longitude lon′0, the ending latitude lat′1, and the longitude resolution r of the digital elevation model data. lon and latitude resolution r lat , as well as the number of columns cols and rows rows of the digital elevation model data, and finally output the cascade reservoir development assessment area range {lon′0,lat′0,lon′1,lat′1,cols,rows} to the correction module 4.

[0126] The correction module 4 corrects the reservoir position coordinates in the watershed digraph. Specifically, the watershed system in the digital elevation model is converted into raster data according to the cascade reservoir development assessment area, and the horizontal coordinates of the m pixels in the watershed digraph are obtained. x,j and the vertical coordinate river y,j . Then calculate the horizontal and vertical coordinates of the pixels of the digital elevation model of each reservoir in the watershed directed graph to obtain the reservoir location coordinates. For any reservoir, calculate the distance between the reservoir and all pixels in the watershed water system in the watershed directed graph, and then modify the reservoir location coordinates to the location coordinates of the watershed water system pixel closest to it based on the distance between the reservoir and all pixels in the watershed water system in the watershed directed graph. After traversing all reservoirs in the watershed directed graph, the correction module 4 outputs the watershed directed graph with the position correction completed and transmits it to the evaluation module 5.

[0127] The evaluation module 5 calculates the flow distance between each pixel in the basin directed graph, the drop and flow distance between any two cascade reservoirs, and the catchment range and confluence interval of any cascade reservoir based on the position-corrected basin directed graph, and conducts cascade reservoir development evaluation.

[0128] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for evaluating the development of cascade reservoirs in a river basin based on a directed graph, characterized in that: The following steps are involved: S1. Obtain digital elevation model data, basin control hydrological station location data and cascade reservoir location data as input data, and construct a basin directed graph based on the input data; wherein: S1.

1. Calculate the flow direction of the digital elevation model data to obtain the flow direction of each pixel in the digital elevation model, and extract the watershed system and its pixels through cumulative flow calculation; S1.

2. According to the flow direction of each pixel in the digital elevation model, a directed graph of the watershed is constructed with the pixel as the node and the flow direction as the edge, and the locations of the controlling hydrological stations in the watershed and the cascade reservoirs are marked in the directed graph of the watershed according to the location data of the controlling hydrological stations in the watershed and the location data of the cascade reservoirs; S2. Obtaining the scope of the cascade reservoir development assessment area according to the input data; S3. Based on the scope of the cascade reservoir development assessment area, the position coordinates of any reservoir in the basin directed graph are corrected; where: S3.

1. According to the scope of the cascade reservoir development assessment area, the watershed system in the digital elevation model is converted into raster data, and the horizontal coordinates of m pixels in the watershed directed graph of the watershed system are obtained. x,j and the vertical axis river y,j , where j = 1, 2, ..., m; S3.

2. Calculate the horizontal and vertical coordinates of the pixels in the watershed directed graph of the digital elevation model of each reservoir to obtain the reservoir location coordinates; the expression is as follows: In the formula, row i represents the ordinate of the i-th reservoir, col i represents the horizontal coordinate of the i-th reservoir; lon i represents the longitude of the i-th reservoir, lat i represents the latitude of the i-th reservoir; where i = 1, 2, ..., n; lat1′ represents the end latitude of the digital elevation model, lon1′ represents the end longitude of the digital elevation model; r lat is the latitude resolution, r lon is the longitude resolution; S3.

3. For any reservoir, calculate the distance between the reservoir and all pixels in the watershed system in the watershed directed graph; the expression is as follows: Where, d i,j It represents the distance between the i-th reservoir and the j-th pixel in the watershed system in the watershed directed graph; S3.

4. For any reservoir, based on the distance between the reservoir and all pixels in the watershed system in the watershed directed graph, the reservoir location coordinates are modified to the location coordinates of the watershed watershed pixel closest to it; the expression is as follows: In the formula, river y,j′ 、river x,j′ is the ordinate and abscissa of the pixel of the watershed closest to the i-th reservoir, row t,i 、col t,i Respectively represent the ordinate and abscissa of the ith reservoir after correction; d min is the shortest distance between the i-th reservoir and the pixel in the watershed system; S4. Based on the position-corrected watershed directed graph, calculate the flow distance between each pixel in the watershed directed graph, the drop and flow distance between any two cascade reservoirs, and the catchment range and catchment interval of any cascade reservoir to conduct a cascade reservoir development assessment.

2. The method for evaluating the development of cascade reservoirs in a river basin based on a directed graph according to claim 1, characterized in that: In the step S2, the step of obtaining the scope of the cascade reservoir development assessment area according to the input data includes: extracting the input data using the GetGeoTransform function to obtain the starting longitude lon0′, the ending latitude lat1′, and the longitude resolution r of the digital elevation model data. lon and latitude resolution r lat , as well as the number of columns cols and rows rows of the digital elevation model data; the scope of the cascade reservoir development assessment area is calculated based on the data extraction results of the input data, and the expression is as follows: Where lon1′ represents the end longitude of the digital elevation model, and lat0′ represents the start latitude of the digital elevation model.

3. The method for evaluating the development of cascade reservoirs in a river basin based on a directed graph according to claim 2, characterized in that: The step S3 further includes the following steps: The basin directed graph with corrected reservoir position coordinates is stored in a table: Convert the coordinates of the cascade reservoirs into numbers; the number of the i-th cascade reservoir is: index i =row t,i ·rows+col t,i ; The horizontal coordinates and the vertical coordinates of all the pixels in the watershed directed graph are recorded by numbers; The serial number of each pixel is used as the index column of the watershed directed graph table, and the upstream pixel of each pixel is used as the data column of the watershed directed graph table, so as to obtain the watershed directed graph table and store it.

4. The method for evaluating the development of cascade reservoirs in a river basin based on a directed graph according to any one of claims 1 to 3, characterized in that: In the step S4, the step of calculating the flow distance between each pixel in the watershed directed graph includes: According to the preset flow direction, the D8 algorithm is used to calculate the flow direction of each pixel in the watershed directed graph to obtain the flow distance from any pixel to the next pixel; where: In the watershed directed graph, the pixels without downstream are defined as outlet pixels, and the flow distance of the outlet pixels is defined as 0; The flow distance from any pixel to the exit pixel is calculated in the upstream direction from the exit pixel. The expression is as follows: dist upstream =dist downstream +d upstream In the formula, dist upstream Indicates the flow distance from the current pixel to the exit pixel, dist downstream Indicates the flow distance from the downstream pixel of the current pixel to the exit pixel, d upstream Represents the flow distance from the current cell to its downstream cell.

5. The method for evaluating the development of cascade reservoirs in a river basin based on a directed graph according to claim 4, characterized in that: The step S4 further includes the following steps: The flow distance between any reservoir and the outlet pixel is obtained according to the flow distance between each pixel in the watershed directed graph, and the flow distance between any reservoir and the outlet pixel is sorted to construct the topological relationship of the cascade reservoirs.

6. The method for evaluating the development of cascade reservoirs in a river basin based on a directed graph according to any one of claims 1 to 3, characterized in that: In step S4, the step of calculating the drop and flow distance between any two cascade reservoirs includes: The position coordinates of the cascade reservoirs are obtained from the position-corrected basin directed graph. The elevation of each cascade reservoir is obtained based on the position coordinates of the cascade reservoirs and the digital elevation model, and the drop between any two cascade reservoirs is calculated. The expression is as follows: Δh p =student p -student p+1 In the formula, Δh p Indicates the height difference of the p-th reservoir, elev p is the elevation of the p-th reservoir; According to the flow distance between each pixel in the watershed directed graph, the flow distance between any two cascade reservoirs is calculated; its expression is as follows: Δfd p =fd p -fd p+1 Where, Δfd p represents the flow distance from the pth reservoir to the p+1th reservoir, fd p It represents the flow distance from the p-th reservoir to the basin outlet.

7. The method for evaluating the development of cascade reservoirs in a river basin based on a directed graph according to any one of claims 1 to 3, characterized in that: In the step S4, the step of calculating the water collection range and flow collection interval of any cascade reservoir includes: The reachability analysis is performed on the position-corrected watershed directed graph to obtain the catchment range of any reservoir. For any pixel j in the watershed directed graph, if there is a path that connects pixel j with the pixel where reservoir i is located, then pixel j belongs to the catchment range of reservoir i. The expression is as follows: D i ={pixel j |pixel j →pixel i } Where D i is the catchment area of ​​reservoir i, pixel j Indicates the position of pixel j, pixel i represents the location of reservoir i; The flow range of the reservoir is calculated according to its catchment range. The expression is as follows: A i+1 =D i+1 -D i In the formula, A i+1 It is the confluence interval of the i+1th level reservoir, and the i+1th level reservoir is the direct downstream reservoir of the i-th level reservoir.

8. A directed graph-based river basin cascade reservoir development assessment system, using the directed graph-based river basin cascade reservoir development assessment method according to any one of claims 1 to 7, characterized in that: include: Data acquisition module, used to obtain digital elevation model data, basin control hydrological station location data and cascade reservoir location data; A watershed directed graph construction module is used to construct a watershed directed graph according to the data collected by the data collection module; A regional scope calculation module is used to calculate the regional scope of cascade reservoir development assessment based on the data collected by the data collection module; A correction module is used to correct the positions of all reservoirs in the watershed directed graph constructed by the watershed directed graph construction module according to the scope of the cascade reservoir development assessment area; The evaluation module is used to calculate the flow distance between each pixel in the basin directed graph, the drop and flow distance between any two cascade reservoirs, and the catchment range and catchment interval of any cascade reservoir based on the basin directed graph corrected by the correction module, and output it as reference data for the development evaluation of cascade reservoirs in the basin.

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