Rainfall spatiotemporal generation method and system based on rainfall weighted flow distance

Abstract

The application discloses a watershed space-time rainfall generation method and system based on rainfall weighted flow distance, comprising the following steps: calculating the distance from each rainfall station to the drainage outlet in a watershed, and performing normalization processing; constructing a rainfall weighted distance constraint in any time period; converting the constraint relationship into a nonlinear least square optimization problem; solving the optimization problem by using a sequential quadratic programming algorithm; repeating the optimization process for all time periods to obtain a watershed rainfall proportion matrix, wherein the watershed rainfall proportion matrix is used for representing the proportional distribution relationship of a rainfall process at different rainfall stations and in different time periods. The application can flexibly generate various rainfall distribution scenarios under the condition of meeting specific rainfall space-time index constraint conditions, so as to quantitatively analyze the influence of rainfall center movement on urban flood process.

Description

Technical Field

[0001] This invention relates to the field of hydrological simulation and urban flood analysis technology, and in particular to a method and system for generating watershed spatiotemporal rainfall based on rainfall-weighted flow distance. Background Technology

[0002] Existing watershed rainfall simulation methods are mostly based on statistical analysis of historical rainfall data, and the spatiotemporal distribution characteristics of rainfall summarized by these methods are representative within a certain region. However, these methods are difficult to cover all possible spatiotemporal structures of rainfall, especially in terms of rainfall center location, direction of movement, and intensity changes. Therefore, there is an urgent need for a method and system based on rainfall-weighted flow distance that can flexibly generate multiple rainfall distribution scenarios under specific spatiotemporal rainfall constraints, in order to quantitatively analyze the impact of rainfall center movement on urban flooding processes. Summary of the Invention

[0003] This invention provides a watershed spatiotemporal rainfall generation method and system based on rainfall-weighted flow distance, in order to solve the technical problem that existing technologies cannot flexibly generate multiple rainfall distribution scenarios under specific spatiotemporal rainfall index constraints, so as to quantitatively analyze the impact of rainfall center movement on urban flooding processes.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] This invention provides a method for generating spatiotemporal rainfall in a watershed based on rainfall-weighted flow distance, comprising:

[0006] S1: Calculate the distance from each rain gauge station to the drainage outlet within the watershed and normalize it;

[0007] S2: Construct rainfall-weighted distance constraints for any given time period;

[0008] S3: Transform the constraint relationship into a nonlinear least squares optimization problem;

[0009] S4: The optimization problem is solved using a sequential quadratic programming algorithm;

[0010] S5: Repeat the optimization process for all time periods to obtain the watershed rainfall ratio matrix, wherein the watershed rainfall ratio matrix is ​​used to characterize the proportional distribution relationship of the rainfall process at different rain gauge stations and at different time periods.

[0011] Furthermore, the calculation formula for the normalization process is as follows:

[0012] in, This is the normalized distance from the rain gauge station to the drainage outlet; This is the actual distance from the rain gauge station to the drainage outlet. This represents the actual distance from the rain gauge station furthest from the drainage outlet.

[0013] Furthermore, in S2, the constraint relationship is as follows:

[0014]

[0015]

[0016] Where RWDt is the target rainfall weighted distance value for time period t, ri,t is the rainfall proportion of the i-th rain gauge station in time period t, di is the normalized distance of the i-th rain gauge station, and n is the number of rain gauge stations; “≈” indicates that the calculated rainfall weighted distance value is expected to be close to the target rainfall weighted distance value, rather than requiring the two to be strictly equal.

[0017] Furthermore, in S3, the objective function is as follows:

[0018]

[0019] in, , represents the proportion vector formed by the rainfall proportions of all rain gauges in time period t.

[0020] Furthermore, in S5, the watershed rainfall ratio matrix is ​​as follows:

[0021]

[0022] Where T is the rainfall duration and R is the watershed rainfall proportion matrix.

[0023] Furthermore, in S4, the specific steps for solving the problem include:

[0024] The initial guess value for the scaling vector is set as follows:

[0025]

[0026] Under the constraints that the sum of the proportions is 1 and the range of the proportion values ​​is [0,1], the proportion vector is iteratively updated.

[0027] When the objective function converges to its minimum value, the rainfall ratio vector for the current time period is output.

[0028] This invention also provides a watershed spatiotemporal rainfall generation system based on rainfall-weighted flow distance, comprising:

[0029] Calculation module: used to calculate the distance from each rain gauge station to the drainage outlet within the watershed and perform normalization processing;

[0030] Constraint module: Used to construct rainfall-weighted distance constraints for any given time period;

[0031] Optimization module: used to transform the constraints into a nonlinear least squares optimization problem;

[0032] Solution module: Used to solve the optimization problem using a sequential quadratic programming algorithm;

[0033] Repeat module: used to repeat the optimization process for all time periods to obtain the watershed rainfall ratio matrix, wherein the watershed rainfall ratio matrix is ​​used to characterize the proportional distribution relationship of the rainfall process at different rain gauge stations and at different time periods.

[0034] Compared with the prior art, the technical solution disclosed in this invention has the following beneficial effects:

[0035] Compared with existing technologies, this invention constructs a weighted distance constraint for rainfall and uses an optimization algorithm to invert the rainfall ratio of each rain gauge station, thereby generating a rainfall scenario that meets the target rainfall spatial characteristics. This enables controllable simulation of the movement characteristics of the rainfall center. In other words, it is a method that can flexibly generate multiple rainfall distribution scenarios under specific spatiotemporal rainfall index constraints to quantitatively analyze the impact of the movement of the rainfall center on urban flooding processes. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the method for generating spatiotemporal rainfall in a watershed based on rainfall-weighted flow distance, provided in an embodiment of the present invention. Detailed Implementation

[0038] 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.

[0039] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] This invention provides a watershed spatiotemporal rainfall generation method and system based on rainfall-weighted flow distance, which can solve the technical problem that existing technologies cannot flexibly generate multiple rainfall distribution scenarios under specific rainfall spatiotemporal index constraints, so as to quantitatively analyze the impact of rainfall center movement on urban flooding processes.

[0041] This invention provides a method for generating spatiotemporal rainfall in a watershed based on rainfall-weighted flow distance, comprising:

[0042] S1: Calculate the distance from each rain gauge station to the drainage outlet within the watershed and normalize it; the calculation formula for the normalization process is as follows:

[0043] in, This is the normalized distance from the rain gauge station to the drainage outlet; This is the actual distance from the rain gauge station to the drainage outlet. This represents the actual distance from the rain gauge station furthest from the drainage outlet.

[0044] The embodiments in this specification include a normalized distance calculation step for rain gauges, which aims to unify the measurement standard of the spatial location of rain gauges, construct a stable and universal rainfall weighted distance index, and provide the necessary technical foundation for subsequent optimization solutions and rainfall scenario generation. This step has a clear and irreplaceable technical role in the overall technical solution.

[0045] S2: Constructing a weighted distance constraint for rainfall at any given time period. The purpose of constructing a weighted distance constraint for rainfall at any given time period is to transform the spatial location information of the target rainfall center into a quantitative constraint on the rainfall proportion of each rain gauge, so that the rainfall proportion allocation result spatially conforms to the preset rainfall distribution characteristics. Through this constraint relationship, the spatial location parameters of the rain gauges are weighted and coupled with their rainfall proportions, thereby achieving a controllable description of the location of the rainfall center. When the target rainfall weighted distance value changes over time, it can further characterize the movement process of the rainfall center, providing core technical support for generating watershed rainfall scenarios that meet specific spatial evolution characteristics.

[0046] In S2, the constraint relationship is as follows:

[0047]

[0048]

[0049] Among them, RWD t Let r be the weighted distance value of the target rainfall in time period t. i t represents the rainfall percentage at the i-th rain gauge station during the t-th time period, and d represents the rainfall percentage at the ith rain gauge station. iHere, is the normalized distance of the i-th rain gauge, and n is the number of rain gauges; "≈" indicates that the calculated rainfall-weighted distance is expected to be close to the target rainfall-weighted distance, but not required to be strictly equal. This is because the rainfall proportion r of each rain gauge is... i The formula t is subject to the constraints of a ratio sum of 1 and a value range of 0 to 1, making it difficult to obtain an analytical solution that strictly satisfies the above relationship under normal circumstances. Therefore, this invention uses this relationship as a target approximation condition and constructs a nonlinear least squares objective function to minimize the deviation between the calculated rainfall weighted distance value and the target value, thereby obtaining the rainfall ratio combination that is closest to the target rainfall weighted distance value under the constraints.

[0050] S3: Transform the constraint relationship into a nonlinear least squares optimization problem; in S3, the objective function is as follows:

[0051]

[0052] in, , represents the proportion vector formed by the rainfall proportions of all rain gauges in time period t.

[0053] S4: Solve the optimization problem using a sequential quadratic programming algorithm; the specific steps in S4 include:

[0054] The initial guess value for the scaling vector is set as follows:

[0055]

[0056] Under the constraints that the sum of the proportions is 1 and the range of the proportion values ​​is [0,1], the proportion vector is iteratively updated.

[0057] When the objective function converges to its minimum value, the rainfall ratio vector for the current time period is output.

[0058] S5: Repeat the optimization process for all time periods to obtain the watershed rainfall ratio matrix. The watershed rainfall ratio matrix is ​​used to characterize the proportional distribution of rainfall processes at different rain gauge stations and at different time periods. It is the core result data describing the spatial distribution and temporal evolution characteristics of rainfall.

[0059] In S5, the watershed rainfall ratio matrix is ​​as follows:

[0060]

[0061] Where T is the rainfall duration and R is the watershed rainfall proportion matrix.

[0062] This invention also provides a watershed spatiotemporal rainfall generation system based on rainfall-weighted flow distance, comprising:

[0063] Calculation module: used to calculate the distance from each rain gauge station to the drainage outlet within the watershed and perform normalization processing;

[0064] Constraint module: Used to construct rainfall-weighted distance constraints for any given time period.

[0065] Optimization module: used to transform the constraints into a nonlinear least squares optimization problem.

[0066] Solution module: Used to solve the optimization problem using a sequential quadratic programming algorithm;

[0067] Repeat module: used to repeat the optimization process for all time periods to obtain the watershed rainfall ratio matrix, wherein the watershed rainfall ratio matrix is ​​used to characterize the proportional distribution relationship of the rainfall process at different rain gauge stations and at different time periods.

[0068] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0069] The block diagrams of devices, apparatuses, devices, and systems involved in this invention are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0070] It should also be noted that in the apparatus, device, and method of the present invention, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered as equivalent solutions of the present invention.

[0071] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the invention. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of the invention. Therefore, the invention is not intended to be limited to the aspects shown herein, but rather to be carried out within the widest scope consistent with the principles and novel features disclosed herein.

[0072] It should be understood that the qualifying terms "first", "second", "third", "fourth", "fifth" and "sixth" used in the description of the embodiments of the present invention are only used to more clearly illustrate the technical solutions and are not intended to limit the scope of protection of the present invention.

[0073] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of the invention to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations therein.

Claims

1. A watershed spatiotemporal rainfall generation method based on rainfall-weighted flow distance, characterized in that, include: S1: Calculate the distance from each rain gauge station to the drainage outlet within the watershed and normalize it; S2: Construct rainfall-weighted distance constraints for any given time period; S3: Transform the constraint relationship into a nonlinear least squares optimization problem; S4: The optimization problem is solved using a sequential quadratic programming algorithm; S5: Repeat the optimization process for all time periods to obtain the watershed rainfall ratio matrix, wherein the watershed rainfall ratio matrix is ​​used to characterize the proportional distribution relationship of the rainfall process at different rain gauge stations and at different time periods.

2. The watershed spatiotemporal rainfall generation method based on rainfall-weighted flow distance according to claim 1, characterized in that, The calculation formula for the normalization process is as follows: in, This is the normalized distance from the rain gauge station to the drainage outlet; This is the actual distance from the rain gauge station to the drainage outlet. This represents the actual distance from the rain gauge station furthest from the drainage outlet.

3. The watershed spatiotemporal rainfall generation method based on rainfall-weighted flow distance according to claim 1, characterized in that, In S2, the constraint relationship is as follows: Among them, RWD t Let r be the weighted distance value of the target rainfall in time period t. i，t Let d be the proportion of rainfall at the i-th rain gauge station in time period t. i is the normalized distance of the i-th rain gauge, and n is the number of rain gauges; "≈" indicates that the calculated rainfall weighted distance is expected to be close to the target rainfall weighted distance value, rather than requiring the two to be strictly equal.

4. The watershed spatiotemporal rainfall generation method based on rainfall-weighted flow distance according to claim 1, characterized in that, In S3, the objective function is as follows: in, , represents the proportion vector formed by the rainfall proportions of all rain gauges in time period t.

5. The watershed spatiotemporal rainfall generation method based on rainfall-weighted flow distance according to claim 1, characterized in that, In S5, the watershed rainfall ratio matrix is ​​as follows: Where T is the rainfall duration and R is the watershed rainfall proportion matrix.

6. The watershed spatiotemporal rainfall generation method based on rainfall-weighted flow distance according to claim 1, characterized in that, The specific steps for solving S4 include: The initial guess value for the scaling vector is set as follows: Under the constraints that the sum of the proportions is 1 and the range of the proportion values ​​is [0,1], the proportion vector is iteratively updated. When the objective function converges to its minimum value, the rainfall ratio vector for the current time period is output.

7. A watershed spatiotemporal rainfall generation system based on rainfall-weighted flow distance, characterized in that, include: Calculation module: used to calculate the distance from each rain gauge station to the drainage outlet within the watershed and perform normalization processing; Constraint module: Used to construct rainfall-weighted distance constraints for any given time period; Optimization module: Used to transform constraints into nonlinear least squares optimization problems; Solution module: Used to solve the optimization problem using a sequential quadratic programming algorithm; Repeat module: used to repeat the optimization process for all time periods to obtain the watershed rainfall ratio matrix, wherein the watershed rainfall ratio matrix is ​​used to characterize the proportional distribution relationship of the rainfall process at different rain gauge stations and at different time periods.

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