Method for converting the topology of inflow and outflow of a complex river basin into a sequence structure

Abstract

The application provides a complex river basin river channel inflow and outflow topology structure to sequence structure conversion method, comprising: respectively coding a river section and a sub-basin; based on the coding of the river section and the sub-basin, a sequence structure model is constructed; the sequence structure model comprises: a runoff generation and confluence object sequence, an inflow object sequence and a confluence outlet sequence; the inflow of the river section is obtained by traversing the confluence outlet sequence and using the runoff generation and confluence object sequence and the inflow object sequence. The application provides an effective topology structure to sequence structure conversion method, the sequence structure is easy to be batch processed, batch processing of river section inflow and outflow is possible, the calculation speed of large basin flood forecasting is accelerated, the difficulty of constructing a complex water system large basin flood forecasting model is reduced, and the timeliness of flood forecasting and real-time flood forecasting is improved.

Description

Technical Field

[0001] This invention relates to the field of complex watershed hydrological technology, and in particular to a method for converting the inflow and outflow topology of complex watershed channels into a sequence structure. Background Technology

[0002] This invention relates to the preliminary process for calculating inflow and outflow in river segments during flood forecasting using a lumped hydrological model for large watersheds, with a focus on dendritic drainage systems. When using lumped models for flood forecasting, large watersheds typically require dividing the river into numerous units, calculating runoff generation for each unit, and then converging the runoff through inter-unit channels. For complex dendritic drainage systems, the number of units is large, and the computational workload for inter-unit runoff exceeds manual processing capabilities, necessitating batch processing. However, batch calculation of inter-unit runoff differs from regular grid runoff, which can be achieved using the D8 algorithm and a nine-square grid. Figure 1 a) The units in the lumped hydrological model for flood forecasting have an irregular topological structure, making it impossible to achieve the inflow and outflow of rivers connecting the units using a regular grid algorithm. Figure 1 (b) This severely limits the timeliness of lumped hydrological models in real-time flood forecasting. Therefore, there is an urgent need to find a method for batch processing the inflow and outflow topology of complex tree-like drainage basin units.

[0003] Existing inventions concerning watershed confluence, river channel confluence, and real-time flood forecasting primarily focus on improving traditional confluence algorithms, such as the Muskingan method and hydrodynamic methods (CN105912770A, CN104281780A, CN109033605A, CN110955924A, CN111062128A). No description of methods for batch processing of topology structures has been found. Existing inventions of upstream and downstream confluence relationship topology tables lack a clear construction method (CN106897529A), and the construction process is susceptible to human factors, making it difficult to replicate across different watersheds and resulting in poor versatility. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a method for converting the inflow and outflow topology of complex watershed channels into a sequence structure. Specifically, for calculating the inflow and outflow of numerous inter-unit channels in a large, tree-like watershed using a lumped hydrological model, this invention provides an effective method for converting topological results into a sequence structure. The sequence structure facilitates batch processing, enabling the batch processing of inflow and outflow data for different river segments and accelerating the calculation speed for flood forecasting in large watersheds. Furthermore, it reduces the difficulty of constructing flood forecasting models for complex watersheds and improves the timeliness of flood forecasts and real-time flood predictions.

[0005] To achieve the above objectives, this invention proposes a method for transforming the inflow and outflow topology of complex watershed channels into a sequential structure, including:

[0006] The river section and sub-basin are coded separately;

[0007] Based on the coding of the river segment and sub-basin, a sequence structure model is constructed; the sequence structure model includes: a sequence of runoff generation and confluence objects, a sequence of inflow objects, and a sequence of runoff outlets;

[0008] By traversing the confluence-outlet sequence and using the confluence-producing object sequence and inflow object sequence, the inflow of this river segment is obtained.

[0009] Optionally, encoding the river segment includes:

[0010] Starting with the downstream main stream segment coded as 1, the coding number gradually increases upstream until the source of the river, completing the coding of the river segment; when the river bifurcates, the coding number of the segment after the bifurcation gradually increases in a counterclockwise direction; the sub-bifurcations upstream of different bifurcations are numbered together in a counterclockwise direction.

[0011] Optionally, encoding the sub-basin includes:

[0012] Starting with the code 0 for the sub-basin where the downstream main stream section is located, the code is gradually increased upstream until the source sub-basin is reached, thus completing the sub-basin coding. Among them, the sub-basins that are not the downstream are coded according to the code numbers of the river sections whose runoff flows into them but not into their own sub-basin.

[0013] Optionally, constructing the sequence of generating and merging objects includes:

[0014] Arrange the numbers in the codes of the sub-basins from largest to smallest to form a descending order sequence of runoff.

[0015] Arrange the numbers in the code of the river segment from largest to smallest to form a descending sequence of confluence, and append it to the descending sequence of runoff to form the sequence of runoff and confluence objects.

[0016] Optionally, constructing the sequence of inflowing objects includes:

[0017] The sequence of generating and confluencing objects is arranged in a sequential order from front to back, and the river segment code / basin outlet into which the generating and confluencing objects flow is not the object is found to form the sequence of inflow objects.

[0018] Optionally, constructing the confluence exit sequence includes:

[0019] The exit code is appended to the end of the descending sequence of the confluence to form the confluence exit sequence.

[0020] Optionally, obtaining the inflow of this river segment includes:

[0021] Traverse the confluence-outflow sequence and calculate the inflow of all objects in the confluence-outflow sequence one by one. In the inflow object sequence, find the same coded river segment. The objects in the same coded river segment corresponding to the confluence-outflow object sequence are all the inflows of this river segment.

[0022] Compared with the prior art, the present invention has the following advantages and technical effects:

[0023] This invention proposes a coding method for river segments and sub-basins that gradually increase upstream, ensuring that each segment and sub-basin has an independent and unique code. In contrast, traditional river classification methods often use non-unique codes for river segments, with many segments sharing the same code, making calculations susceptible to human error. Therefore, the coding method of this invention is clear in its process, yields a unique result, and allows different users to reproduce the same result without variation. Furthermore, it is applicable to different river basins and its usability does not change with the basin.

[0024] This invention proposes a descending order sorting method and a sub-basin-first-then-river-segment sorting method, ensuring that objects in later segments of the sequence are completely dependent on the results of objects in earlier segments during flow calculation. In batch calculations, the input / inflow of a particular object is the sum of the results of certain objects in the preceding segment, while the inflow of the preceding objects has already been pre-calculated during traversal to obtain the outflow. This avoids the awkward situation and error of an object's inflow being uncalculated when the results of its dependent objects have not yet been calculated, thus preventing program malfunctions and significantly reducing the difficulty for users to troubleshoot errors.

[0025] This invention ingeniously utilizes two closely interdependent sequences—the sequence of inflow and outflow objects—to achieve the transformation from topological structure to sequence structure. The sequence structure contains the same sufficient topological information as the topological structure and allows for batch processing without the need for repeated visual interpretation of inflow-outflow relationships. Furthermore, it clarifies the statistical method for inflow in a specific river segment, avoiding over-counting and oversights caused by visually identifying inflow objects, thus enabling batch calculations. In addition, the inflow statistical process for each river segment is clearly defined, the results are unique, different users can reproduce the same results without individual variations, and it is applicable to different watersheds, ensuring the method remains usable even when the watershed changes.

[0026] The method of this invention is simple in its steps, and each step is clearly defined and unique. Existing methods often involve more than 10 steps, with considerable redundancy in each process. Therefore, this invention can significantly improve the user's work efficiency and the certainty of the results, reduce error and troubleshooting time, shorten model running time, and significantly improve the timeliness of real-time flood forecasts. Attached Figure Description

[0027] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0028] Figure 1 This diagram illustrates the merging of regular grid networks and irregular topologies; where, Figure 1 (a) is a schematic diagram of a regular grid. Figure 1 (b) is a schematic diagram of an irregular topological structure confluence;

[0029] Figure 2 This is a flowchart illustrating the technical solution of the method for transforming the inflow and outflow topology of complex tree-like watershed units into a sequence structure, as described in this invention.

[0030] Figure 3 This is a schematic diagram illustrating the specific implementation of steps S1 and S2 of the river segment coding and sub-basin coding process in an embodiment of the present invention; wherein, Figure 3 (a) is a schematic diagram showing the start of river segment coding. Figure 3 (b) is a schematic diagram of the sub-basin following the river segment code encoding. Figure 3 (c) is a schematic diagram of the coding results for all river segments and sub-basins. Detailed Implementation

[0031] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0032] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0033] The technical problem to be solved in this embodiment is that existing lumped hydrological models cannot perform batch processing of river inflow and outflow calculations in flood forecasting of large watersheds with dendritic drainage systems. The units in large watersheds with dendritic drainage systems have irregular topological structures, complex topological structures, many levels, and complex inflow and outflow relationships in river segments, which limits the timeliness of lumped hydrological models in real-time flood forecasting.

[0034] The technical solution adopted in this embodiment is to provide a method for transforming the inflow and outflow topology of complex tree-like watershed units into a sequential structure, including the following steps:

[0035] Step S1: River Segment Coding. All river segments are coded according to the tree-like drainage system, starting with the downstream main stream segment coded as 1, and gradually increasing the code number upstream until the river source. When the river bifurcates, the code number for the subsequent segments increases gradually in a counter-clockwise direction. Sub-bifurcations upstream of different bifurcations are numbered together in a counter-clockwise direction. This completes the coding of the river segments, i.e., the digital construction of the river segment's topological structure.

[0036] Step S2: Sub-basin coding. All sub-basins are coded according to the already defined sub-basins / units, starting with 0 for the sub-basin containing the downstream main stream segment and gradually increasing the code number upstream until the source sub-basin. Sub-basins are divided into two types: those with a river segment passing through them, called intermediate sub-basins, and those without a river segment passing through them, usually located upstream of the source segment, called source sub-basins. Sub-basins not at the downstream end are coded according to the code number of the river segment whose runoff flows into them but not within their own sub-basin. This completes the sub-basin coding, i.e., the topological digitization of the sub-basins.

[0037] Step S3: Constructing the runoff generation and confluence object sequence. Runoff generation objects are all sub-basins, arranged in descending order of their sub-basin codes, forming a descending runoff generation sequence. Confluence objects are all river segments, arranged in descending order of their river segment codes, forming a descending confluence confluence sequence, which is then appended to the descending runoff generation sequence to form a descending runoff generation and confluence object sequence. This transforms the topological structure into a sequence structure.

[0038] Step S4: Constructing the Inflow Object Sequence. For the flow-generating and flow-converging object sequence, in chronological order, find the river segment codes / basin outlets into which the flow-generating and flow-converging objects flow, thus forming the flow-generating and flow-converging object inflow object sequence. This transforms the topology into a sequence structure, which includes the flow-generating and flow-converging object sequence and the inflow object sequence.

[0039] Step S5: Batch Calculation of Inflows into River Segments. For a specific time period in the model calculation, this step assumes that the sub-basin runoff and river segment outflow have already been obtained. An outlet sequence ('o') is appended to the end of the descending confluence sequence to form a confluence-outlet sequence. This sequence is traversed, and the inflows of all its objects are calculated one by one. For a given river segment, segments with the same encoding are searched in the inflow object sequence. These segments correspond to the objects in the runoff object sequence, which represent all inflows into this segment. Summing these inflows yields the inflows into this segment. The inflows of all river segments are calculated in this manner.

[0040] The five steps in this embodiment can be summarized as follows: Figure 2 The flowchart.

[0041] The specific implementation steps of this embodiment are described in detail below:

[0042] by Figure 1The b-type watershed is the specific implementation object. This implementation object conforms to the characteristics of a complex tree-like drainage basin, with multiple branching rivers, and is not overly complex. This approach effectively illustrates the technical solution of the invention while avoiding excessive complexity that would increase the difficulty of understanding. The choice of this object does not affect the application of the invention to more complex watersheds, nor does it affect the versatility of the invention, achieving an effective combination of complexity and ease of understanding. Let the watershed outlet be denoted as o.

[0043] S1: River segment code. The river system of the basin is a tree-like system, and the coding starts from the root / lowest downstream (bottom right corner), coded as r1, such as... Figure 3 As shown in diagram a. Continuing upstream, a two-fork is encountered. Based on the principle of counter-clockwise and upstream-incrementing coding upon encountering a fork, these two river segments are coded as r2 and r3 respectively. Then, looking upstream from r2 and r3, it is found that r3 has reached its source and has not forked further, while r2 continues to have two forks. Therefore, again based on the principle of counter-clockwise and upstream-incrementing coding upon encountering a fork, the two river segments upstream of r2 are coded as r4 and r5 respectively. Continuing upstream along r4 and r5, it is found that both of these river segments have two forks upstream. Therefore, the four river segments after these two forks are grouped together and coded counter-clockwise, resulting in r6, r7, r8, and r9. This process continues, yielding the codes for all river segments as follows. Figure 3 As shown in c.

[0044] S2: Sub-basin coding. First, the downstreamest sub-basin is coded, i.e., the sub-basin through which river segment r1 flows, coded as b0, such as... Figure 3 As shown in b. Then, tracing upstream along river segment r1, we find the sub-basins through which river segments r2 and r3 flow, i.e., intermediate sub-basins. Based on the principle of using the downstream river segment as a reference, the downstream river segment into which the water yield of this sub-basin flows is r1. Therefore, using r1 as the reference, the sub-basin is coded as b1. Continuing upstream along river segments r2 and r3, we find that the upstream of r3 is a source sub-basin. The downstream river segment into which the water yield of this source sub-basin flows is r3; therefore, this source sub-basin is coded as b3. The sub-basin upstream of river segment r2 is the intermediate sub-basin through which river segments r4 and r5 flow. The downstream river segment into which this sub-basin flows is r2; therefore, this sub-basin is coded as b2. Then, continuing upstream along the r4 and r5 river segments, it is found that the sub-basin upstream of r4 is an intermediate sub-basin through which the r6 and r7 river segments flow. The downstream river segment into which the runoff of this sub-basin flows is r4; therefore, this source sub-basin is coded as b4. Similarly, it is found that the sub-basin upstream of r5 is an intermediate sub-basin through which the r8 and r9 river segments flow. The downstream river segment into which the runoff of this sub-basin flows is r5; therefore, this source sub-basin is coded as b5. This process is repeated to obtain the codes for all sub-basins, such as... Figure 3 As shown in c.

[0045] S3: Construction of the descending sequence of runoff-generating and runoff-converging objects. The sub-basin is the runoff-generating object. The runoff-generating objects are first sorted in descending order, which is the bolded part in the second column sb(i) of Table 1. Then, the runoff-converging objects are sorted after this column. The runoff-converging objects are river segments, so the river segments are sorted in descending order according to the code, which is the unbolded part in the second column sb(i) of Table 1. In this way, the descending sequence sb of runoff-generating and runoff-converging objects is constructed, as shown in the second column of Table 1. i is the sequence number, then sb(1) = b19, sb(38) = r1.

[0046] S4: Construction of the inflow object sequence. Traverse each object in the flow-generating and confluence-generating object sequence from front to back, find the downstream river segment / outlet into which it flows, and form the inflow object sequence by their numbers. The first object in the sequence is sb(1) = b19. According to the watershed topology, the river segment into which the flow of b19 flows is r19, so r19 is the first object in the inflow object sequence. The second object in the flow-generating and confluence-generating object sequence is sb(2) = b18. According to the watershed topology, the river segment into which the flow of b18 flows is r18, so r18 is the second object in the inflow object sequence. The 20th object in the flow-generating and confluence-generating object sequence is sb(20) = b0. According to the watershed topology, b0 is the most downstream sub-watershed, and the river segment into which its flow flows is the watershed outlet o, so o is the 20th object in the inflow object sequence. The 21st inflow object sequence is sb(21) = r19. According to the watershed topology, the outflow from the r19 segment flows into the r15 segment, which is the 21st inflow object sequence. This process is repeated to obtain the inflow object sequence, as shown in the third column of Table 1, qn(i).

[0047] Table 1 shows the specific results of the constructed flow generation and confluence object sequences, inflow object sequences, and flow outflow sequences.

[0048]

[0049]

[0050] S5: Batch calculation of river inflow. For a certain period of the model, the output of all sub-basins and the outflow of all river segments are known. The outflow code o is appended to the end of the descending sequence of confluence sb[21:39] to obtain the confluence-outflow sequence, as shown in column 4 of Table 1, qo(i), which is 20 in length. Traverse each object of qo(i) and calculate its inflow. When i=1, qo(1)=r19. Calculate the inflow of river segment r19. Search for r19 in the inflow object sequence. The result is only qn(1)=r19. According to the sequence number i=1, the inflow of r19 is the output of the confluence object sb(1)=b19 sub-basin. Similarly, when i = 14, qo(14) = r6. Calculate the inflow of the r6 river segment. Search for r6 in the inflow object sequence. The results are qn(14) = r6, qn(29) = r6, qn(30) = r6. According to the sequence numbers i = 14, 29, 30, the corresponding flow-generating and flow-converging objects are sb(14) = b6, sb(29) = r11, sb(30) = r10. Then the inflow of r6 is the sum of the flow-generating flow of the b6 sub-basin, the outflow of the r11 river segment, and the outflow of the r10 river segment. The inflow of the r11 and r10 river segments in this period has already been calculated in the preceding sequence of the confluence outlet, and the corresponding outflow has already been calculated in the previous period. Therefore, the total inflow of the r6 river segment can be obtained by directly summing the three water volumes. By analogy, the inflow of all river segments and the outlet o of the basin can be obtained.

[0051] In summary, the transformation from the topological structure of the basin's runoff generation and confluence to a sequence structure was achieved through the coding of river segments and sub-basins in S1 and S2, and the construction of runoff generation and confluence objects and inflow object sequences in S3 and S4. In step S5, the batch calculation of inflow of confluence outlet objects was realized based on the transformed sequence structure.

[0052] This embodiment proposes a coding method for river segments and sub-basins that gradually increase upstream, ensuring that each river segment and sub-basin has an independent and unique code. In contrast, traditional river classification methods often use non-unique codes for river segments, with many segments sharing the same code, making calculations susceptible to human error. Therefore, the coding method in this embodiment is clear in its process, yields a unique result, and allows different users to reproduce the same result without variations. Furthermore, it is applicable to different river basins and its usability does not change with the basin.

[0053] This embodiment proposes a descending order sorting method and a sub-basin-first-then-river-segment sorting method, ensuring that objects in later segments of the sequence are completely dependent on the results of objects in earlier segments during flow calculation. In batch calculations, the input / inflow of a particular object is the sum of the results of certain objects in the preceding segment, while the inflow of the preceding objects has already been pre-calculated during traversal to obtain the outflow. This avoids the awkward situation and error of an object's inflow being uncalculated when the results of its dependent objects have not yet been calculated, thus preventing program malfunctions and significantly reducing the difficulty for users to troubleshoot errors.

[0054] This embodiment cleverly utilizes two closely interdependent sequences—the sequence of inflow and the sequence of runoff-generating objects—to achieve the transformation from a topological structure to a sequence structure. It also clarifies the statistical results of inflow objects in a specific river segment, avoiding over-counting and oversights caused by visually identifying inflow objects, thus enabling batch calculations. Furthermore, the statistical process for inflow objects in each river segment is clearly defined, the results are unique, different users can reproduce the same results, and the method is not affected by individual differences. It is also applicable to different watersheds, ensuring its usability even when the watershed changes.

[0055] The method in this embodiment has only 5 steps, and each step is clearly defined and unique. Existing methods often have more than 10 steps, and each process is redundant. Therefore, this embodiment can significantly improve the user's work efficiency and the certainty of the results, reduce the time for error and fault diagnosis, reduce model running time, and significantly improve the timeliness of real-time flood forecasts.

[0056] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for converting complex watershed channel inflow and outflow topology into a sequential structure, characterized in that, The method is used for calculating the inflow and outflow of rivers among a large number of units in a dendritic drainage system using a lumped hydrological model. The river section and sub-basin are coded separately; Based on the coding of the river segment and sub-basin, a sequence structure model is constructed; the sequence structure model includes: a sequence of runoff generation and confluence objects, a sequence of inflow objects, and a sequence of runoff outlets; Traverse the confluence-outlet sequence and use the confluence-producing object sequence and inflow object sequence to obtain the inflow of this river segment; Constructing the sequence of generating and merging objects includes: Arrange the numbers in the codes of the sub-basins from largest to smallest to form a descending order sequence of runoff; Arrange the numbers in the code of the river segment from largest to smallest to form a descending sequence of confluence, and append it to the descending sequence of runoff to form the sequence of runoff and confluence objects. Constructing the inflow object sequence includes: The sequence of runoff-generating and runoff-converging objects is arranged in a forward-to-back order, and the river segment codes / basin outlets into which the runoff-generating and runoff-converging objects flow into non-objects are searched to form the sequence of inflow objects. Constructing the confluence exit sequence includes: The exit code is appended to the end of the descending sequence of the confluence to form the confluence exit sequence; Obtaining the inflow of this river section includes: Traverse the confluence-outflow sequence and calculate the inflow of all objects in the confluence-outflow sequence one by one. In the inflow object sequence, find the same coded river segment. The objects in the same coded river segment corresponding to the confluence-outflow object sequence are all the inflows of this river segment.

2. The method for converting complex watershed channel inflow and outflow topology into a sequence structure according to claim 1, characterized in that, Encoding the river segment includes: Starting with the downstream main stream segment coded as 1, the coding number gradually increases upstream until the source of the river, completing the coding of the river segment; when the river bifurcates, the coding number of the segment after the bifurcation gradually increases in a counterclockwise direction; the sub-bifurcations upstream of different bifurcations are numbered together in a counterclockwise direction.

3. The method for converting complex watershed channel inflow and outflow topology into a sequence structure according to claim 1, characterized in that, Encoding the sub-basin includes: Starting with the code 0 for the sub-basin where the downstream main stream section is located, the code is gradually increased upstream until the source sub-basin is reached, thus completing the sub-basin coding. Among them, the sub-basins that are not the downstream are coded according to the code numbers of the river sections whose runoff flows into them but not into their own sub-basin.

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