A flood season classification method based on hydrological seasonality indicators

Abstract

The present invention discloses a flood season staging method based on hydrological seasonal indicators. The method comprises the following steps: acquiring data information, performing data preprocessing, and obtaining hydrological element sequence data; then calculating the hydrological seasonal indicators, determining the centroid time and the expected length; extracting flood season characteristics, calculating the flood season start time, the main flood season start time, the main flood season end time, and the flood season end time; completing the flood season staging based on the extracted flood season characteristic elements; the present invention overcomes the defects of the prior art for flood season staging, and realizes a flood season staging process with smaller errors and more accurate staging.

Description

Technical Field

[0001] The invention relates to the technical field of flood season staging, and in particular to a flood season staging method based on hydrological seasonality indicators. Background Art

[0002] Flood season staging has many practical uses in runoff forecasting, floodplain management, and reservoir flood season operation management. In order to make full use of local water resources, reservoirs and other water conservancy projects are implemented in stages to control flood limit water levels, maximize the storage capacity of reservoirs, and store floods and convert them into usable water resources. Reasonable determination of flood season staging is not only the basis for staged flood design and staged flood limit water levels, but also has important significance for reservoir flood control, floodplain management, and safe use of floods.

[0003] The flood season is generally divided into the pre-flood season, the main flood season and the post-flood season. The methods of flood season division can be divided into two categories: qualitative and quantitative. The qualitative analysis method mainly relies on rich practical experience and subjective judgment and analysis ability to divide the flood season. Its typical representative method is the cause analysis method. The quantitative method can be divided into statistical analysis method and cluster analysis method. Commonly used methods include mathematical statistics method, vector statistics method and fuzzy set analysis method. The cause analysis method is based on the analysis of the hydrology and meteorology of the study basin, but there is a certain subjectivity in analyzing the causes of rainstorm weather. Especially for larger basins, there are often multiple combinations of disaster weather, and the workload of stage division is large. The mathematical statistics method is simple and practical, but in the analysis process, the selection of critical values ​​is subjective, and it is difficult to divide the flood season very finely. The fuzzy analysis method integrates the cause analysis, mathematical statistics, and fuzzy statistics methods into one, and uses the membership function to describe the membership of the flood season, which is conducive to reflecting the changing law of the flood season, but this method requires fitting the distribution function and the critical membership of the stage, which may be subjective. However, few studies have proposed methods for dividing flood seasons based on hydrological seasonal indicators.

[0004] Based on the above-mentioned defects in the prior art for flood season division, how to propose a basin flood season division method with smaller errors and more accurate division is a problem that technical personnel in this field urgently need to solve. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a flood season staging method based on hydrological seasonal indicators, to overcome the defects of flood season staging in the prior art, and to achieve a flood season staging process with smaller errors and more accurate staging.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A flood season classification method based on hydrological seasonality indicators comprises the following steps:

[0008] Step 1: Obtain data, perform data preprocessing, and obtain hydrological element sequence data;

[0009] Step 2: Calculate the hydrological seasonality index and determine the centroid time CT and the length of the rainy season D;

[0010] Step 3: Adjust parameter values, extract flood season characteristics, and calculate the start time of the pre-flood season, the start time of the main flood season, the end time of the main flood season, and the end time of the post-flood season;

[0011] Step 4: Complete the flood season phases based on the extracted flood season characteristic elements.

[0012] Preferably, the step 1 is specifically:

[0013] Obtain any one of precipitation data, flow data and water level data;

[0014] Precipitation data are measured data from meteorological stations. Satellite meteorological data or reanalysis methods are used to supplement meteorological data in areas where data are scarce.

[0015] The flow data and water level data use the measured data from the hydrological stations. In areas where data are scarce, the flow and water level data are inverted by building hydrological and hydrodynamic models.

[0016] Preferably, in step 2, a calculation formula is used to determine the centroid time and rainy season length of the sequence data, and the specific formula is:

[0017] The formula for calculating the centroid time is:

[0018] ;

[0019] In the formula, i Represents the annual sky; It is Hydrological elements of the sky;

[0020] The formula for calculating the length of the rainy season is:

[0021]

[0022] In the formula, Indicates Hydrological elements of the sky; Indicates the first Days; CT represents the centroid time of the hydrological process within a year.

[0023] Preferably, the step 3 specifically includes:

[0024] Step 301, calculating the start and end time of the main flood season;

[0025] Step 302: Calculate the start time of the first flood season and the end time of the second flood season.

[0026] Furthermore, the step 301 is specifically as follows:

[0027] The start and end time of the main flood season are calculated based on the centroid time CT and rainy season length D obtained in step 2. The calculation formula is:

[0028]

[0029]

[0030] In the formula, Indicates the start time of the main flood season; Indicates the end time of the main flood season; CT It represents the centroid time of the hydrological process within a year; D Indicates the length of the rainy season; is the regulating factor, ; is the shrinkage factor, ;Right now The length of the main flood season;

[0031] Furthermore, the step 302 is specifically as follows:

[0032] 1) Calculate the start time of the pre-flood season: Calculate the start time of the pre-flood season based on the start time of the main flood season. The calculation formula is:

[0033]

[0034] In the formula, Indicates the start time of the pre-flood season; Indicates the start time of the main flood season; Indicates the length of the rainy season; represents the front expansion factor, ;Right now is the length of the pre-flood season;

[0035] 2) Calculate the end time of the post-flood season: Calculate the end time of the post-flood season based on the end time of the main flood season. The calculation formula is:

[0036]

[0037] In the formula, Indicates the end time of the post-flood season; Indicates the end time of the main flood season; Indicates the length of the rainy season; represents the post-expansion factor, ;Right now It is the length of the post-flood season.

[0038] In addition, the present invention also discloses a flood season classification system based on hydrological seasonal indicators, including:

[0039] Data acquisition module: used to obtain basin data, perform data preprocessing, and obtain sequence data;

[0040] Hydrological seasonality index calculation module: used to determine the distribution characteristics of the sequence data, and then calculate the centroid time and the length of the rainy season;

[0041] The main flood season start and end time calculation module is used to calculate the start and end time of the main flood season, the start time of the pre-flood season and the end time of the post-flood season according to the hydrological seasonality index;

[0042] Flood season stage module: Divide the flood season according to the extracted flood season characteristic elements.

[0043] Compared with the prior art, the flood season staging method based on hydrological seasonal indicators disclosed in the present invention has the following beneficial effects:

[0044] The present invention uses hydrological seasonal indicators as the basis for flood season division, and uses the annual centroid time and the length of the rainy season to calculate and divide the front and rear flood seasons and the main flood season, thereby overcoming the non-uniform characteristics of hydrological elements, and utilizing the characteristic that the centroid time is more sensitive to the time of occurrence of heavy rain and above precipitation, making the calculation result of the flood season time more accurate.

[0045] The present invention overcomes the defects of the prior art in flood season division, not only eliminates the errors caused by human subjective factors, but also increases the flood season time to a daily scale, thereby achieving a flood season division process with smaller errors and more accurate division. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a time diagram of the centroid of the daily runoff process in a certain year;

[0047] Figure 2 It is a schematic diagram of flood season characteristics of the present invention;

[0048] Figure 3 is a flow chart of the present invention;

[0049] Figure 4 is a system structure diagram of the present invention;

[0050] Figure 5 This is the distribution of meteorological stations and Thiessen polygons in Sichuan Province. DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] like Figure 3 As shown, the embodiment of the present invention provides a flood season stage method based on hydrological seasonal indicators, which includes the following steps:

[0053] Step 1: Obtain data, perform data preprocessing, and obtain hydrological element sequence data;

[0054] Step 2: Figure 1 As shown, the hydrological seasonality index is calculated, and the centroid time CT and the length of the rainy season D are determined;

[0055] Step 3: Figure 2 As shown, adjust the parameter values, extract the flood season characteristics, and calculate the start time of the pre-flood season, the start time of the main flood season, the end time of the main flood season, and the end time of the post-flood season;

[0056] Step 4: Complete the flood season phases based on the extracted flood season characteristic elements.

[0057] Preferably, the step 1 is specifically:

[0058] Obtain any one of precipitation data, flow data and water level data;

[0059] The precipitation data are measured data from meteorological stations. In areas where data are scarce, satellite meteorological data or reanalysis methods are used to supplement meteorological data. The data preprocessing method is to use any of the Thiessen polygon method and the average method to calculate the basin surface precipitation series data.

[0060] Flow data and water level data use measured data from hydrological stations. In areas where data are scarce, flow and water level data are inverted by building hydrological and hydrodynamic models. The data preprocessing method is to build a basin lumped, semi-distributed or distributed hydrological model to simulate basin surface flow and water level series data based on flow data and water level data.

[0061] Preferably, in step 2, a calculation formula is used to determine the centroid time and rainy season length of the sequence data, and the specific formula is:

[0062] The formula for calculating the centroid time is:

[0063] ;

[0064] In the formula, i Represents the annual sky; It is Hydrological elements of the sky;

[0065] The formula for calculating the length of the rainy season is:

[0066]

[0067] In the formula, Indicates Hydrological elements of the sky; Indicates the first Days; CT represents the centroid time of the hydrological process within a year.

[0068] Preferably, the step 3 specifically includes:

[0069] Step 301, calculating the start and end time of the main flood season;

[0070] Step 302: Calculate the start time of the first flood season and the end time of the second flood season.

[0071] Furthermore, the step 301 is specifically as follows:

[0072] The start and end time of the main flood season are calculated based on the centroid time CT and rainy season length D obtained in step 2. The calculation formula is:

[0073]

[0074]

[0075] In the formula, Indicates the start time of the main flood season; Indicates the end time of the main flood season; CT It represents the centroid time of the hydrological process within a year; D Indicates the length of the rainy season; is the regulating factor, ; is the shrinkage factor, ;Right now The length of the main flood season;

[0076] Furthermore, the step 302 is specifically as follows:

[0077] 1) Calculate the start time of the pre-flood season: Calculate the start time of the pre-flood season based on the start time of the main flood season. The calculation formula is:

[0078]

[0079] In the formula, Indicates the start time of the pre-flood season; Indicates the start time of the main flood season; Indicates the length of the rainy season; represents the front expansion factor, ;Right now is the length of the pre-flood season;

[0080] 2) Calculate the end time of the post-flood season: Calculate the end time of the post-flood season based on the end time of the main flood season. The calculation formula is:

[0081]

[0082] In the formula, Indicates the end time of the post-flood season; Indicates the end time of the main flood season; Indicates the length of the rainy season; represents the post-expansion factor, ;Right now It is the length of the post-flood season.

[0083] In addition, the present invention also discloses a flood season classification system based on hydrological seasonal indicators, including:

[0084] Data acquisition module: used to obtain basin data, perform data preprocessing, and obtain sequence data;

[0085] Hydrological seasonality index calculation module: used to determine the distribution characteristics of the sequence data, and then calculate the centroid time and the length of the rainy season;

[0086] The main flood season start and end time calculation module is used to calculate the start and end time of the main flood season, the start time of the pre-flood season and the end time of the post-flood season according to the hydrological seasonality index;

[0087] Flood season stage module: Divide the flood season according to the extracted flood season characteristic elements.

[0088] The flood season in Sichuan Province in 2019 is taken as an example to demonstrate the technical effect achieved by the present invention.

[0089] In 2019, the annual precipitation in Sichuan Province was 1034.4 mm, 8% more than the normal year, ranking 16th in history. A total of 457 rainstorms occurred in the province, 50 more than the normal year, and the number of rainstorms ranked more than 10th in history, including 79 heavy rainstorms, 16 more than the normal year. Last year, the maximum precipitation in Gulin County and Ganluo County reached 163.7 mm and 98.6 mm, breaking the historical records of the maximum daily precipitation in these two stations; the daily precipitation in Emeishan City on August 3 was 211.5 mm, the maximum daily precipitation in the province in 2019; the process rainfall in Tongjiang County from October 3 to 11 was 332.8 mm, the maximum process rainfall in the province in 2019.

[0090] Specifically, the steps of dividing the flood season into stages using the method of the present invention are as follows:

[0091] Step 1: Use the precipitation sequence of Sichuan Province to divide the flood season into stages, and select Thiessen polygons to obtain long-term series data of basin surface precipitation: Draw Thiessen polygons of 35 meteorological stations, see Figure 4 ; Then calculate the proportion of each meteorological station in the basin, see Table 1; strictly align the precipitation data for each period; based on the obtained meteorological station proportions, estimate the surface precipitation series data of Sichuan Province.

[0092] Table 1 Precipitation series in Sichuan Province in 2019

[0093]

[0094] Step 2: Calculate the hydrological seasonality index. Using the formula, the centroid time is 200, which is converted into calendar days as July 19. The length of the rainy season is 60.3 days.

[0095] Step 3: Adjust parameter values ​​and extract flood season characteristics. There are two methods for model parameter calibration: manual and automatic. Manual calibration is to manually adjust parameters by trial and error. This method is greatly influenced by human subjectivity and requires the modeler to correctly understand the model structure and the meaning of each parameter. Automatic calibration is based on the optimization idea and converts parameter calibration into optimization problem solving. Not only are the results objective and accurate, but the efficiency is significantly improved. Automatic parameter calibration can be divided into local search method, statistical method and heuristic search method according to its algorithm structure and search mechanism. The local search method is mainly based on the gradient method for optimization, which has the disadvantages of being easy to fall into the local optimum, or the algorithm structure is complex and the gradient solution process is cumbersome; the statistical method is mainly based on random sampling. Although it can avoid the decision-making risk caused by the distortion of the results to a certain extent, the huge amount of calculation makes it difficult to promote in practical applications; the heuristic search algorithm belongs to an intelligent algorithm, which uses the heuristic information of the problem to guide the search in the state space to reduce the search range and reduce the complexity of the problem. Determine the parameter value through automatic calibration.

[0096] when =0.514, =-0.387, =212(July 31), =243 (August 31). when =1.51, =121(May 1). when =0.66, =283 (October 10).

[0097] Step 4: According to the flood season characteristics extracted in step 3, the flood season in Sichuan Province in 2019 starts on May 1 and ends on October 10, with a total of 162 days. The pre-flood season starts on May 1, with a total of 91 days; the main flood season starts on July 31 and ends on August 31, with a total of 31 days; the post-flood season ends on October 10, with a total of 40 days.

[0098] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0099] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A flood season classification method based on hydrological seasonality indicators, characterized by: It includes the following steps: Step 1: Obtain data, perform data preprocessing, and obtain hydrological element sequence data; Step 2: Calculate the hydrological seasonality index and determine the centroid time CT and the length of the rainy season D; Step 3: Adjust parameter values, extract flood season characteristics, and calculate the start time of the pre-flood season, the start time of the main flood season, the end time of the main flood season, and the end time of the post-flood season; Step 4: Based on the extracted flood season characteristic elements, complete the flood season stage division; In step 2, a calculation formula is used to determine the centroid time and rainy season length of the sequence data. The specific formula is: The formula for calculating the centroid time is: ； In the formula, i Represents the annual sky; It is Hydrological elements of the sky; The formula for calculating the length of the rainy season is: ； In the formula, Indicates Hydrological elements of the sky; Indicates the first sky; CT represents the centroid time of the hydrological process within the year; The step 3 specifically includes: Step 301, calculating the start and end time of the main flood season; Step 302, calculating the start time of the first flood season and the end time of the second flood season; The step 301 is specifically as follows: The start and end time of the main flood season are calculated based on the centroid time CT and rainy season length D obtained in step 2. The calculation formula is: ； ； In the formula, Indicates the start time of the main flood season; Indicates the end time of the main flood season; CT It represents the centroid time of the hydrological process within a year; D Indicates the length of the rainy season; is the regulating factor, ; is the shrinkage factor, ;Right now The length of the main flood season; The step 302 is specifically as follows: 1) Calculate the start time of the pre-flood season: Calculate the start time of the pre-flood season based on the start time of the main flood season. The calculation formula is: ； In the formula, Indicates the start time of the pre-flood season; Indicates the start time of the main flood season; Indicates the length of the rainy season; represents the front expansion factor, ;Right now is the length of the pre-flood season; 2) Calculate the end time of the post-flood season: Calculate the end time of the post-flood season based on the end time of the main flood season. The calculation formula is: ； In the formula, Indicates the end time of the post-flood season; Indicates the end time of the main flood season; Indicates the length of the rainy season; represents the post-expansion factor, ;Right now It is the length of the post-flood season.

2. The method for dividing flood season into stages based on hydrological seasonal indicators according to claim 1, characterized in that: The step 1 is specifically as follows: Obtain any one of precipitation data, flow data and water level data; Precipitation data are measured data from meteorological stations. Satellite meteorological data or reanalysis methods are used to supplement meteorological data in areas where data are scarce. The flow data and water level data use the measured data from the hydrological stations. In areas where data are scarce, the flow and water level data are inverted by building hydrological and hydrodynamic models.

3. A flood season staging system using the flood season staging method based on hydrological seasonal indicators as claimed in claim 1, characterized in that: include: Data acquisition module: used to obtain basin data, perform data preprocessing, and obtain sequence data; Hydrological seasonality index calculation module: used to determine the distribution characteristics of the sequence data, and then calculate the centroid time and the length of the rainy season; The main flood season start and end time calculation module is used to calculate the start and end time of the main flood season, the start time of the pre-flood season and the end time of the post-flood season according to the hydrological seasonality index; Flood season stage module: Divide the flood season according to the extracted flood season characteristic elements.

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