Small reservoir dynamic critical rainfall real-time efficient early warning method considering rainstorm duration

Abstract

The invention provides a small reservoir dynamic critical rainfall real-time efficient early warning method considering rainstorm duration, and the method comprises the steps: carrying out the digitalization and feature extraction of a natural drainage basin through geographic space data, and transplanting the rainfall runoff relation parameters of a region with data to a small reservoir drainage basin without data; the method comprises the following steps: comprehensively considering the influence rainfall and the real-time water volume in the early stage of a drainage basin, setting the reservoir-out total water volume factor under a rainstorm duration condition, finely dividing each stage of reservoir-in flood, reservoir-out flood and water level changing along with time in a flood development process based on a graphic analysis method, and finally calculating by adopting a transplanted rainfall runoff relationship to obtain a small reservoir critical rainfall value; and carrying out grid matching on the meteorological rainfall numerical forecasting result and the water collecting area of the small reservoir basin, and comparing the estimated rainfall within the set rainstorm duration with the critical rainfall analysis result to realize real-time early warning of the disaster-causing rainstorm. The method is high in operation efficiency, and can provide technical support for flood risk early warning of the small reservoir in a large-scale data-free area.

Description

Technical Field

[0001] The invention relates to the technical field of flood forecasting and reservoir risk early warning, and in particular to a real-time and rapid early warning of critical rainfall of a small reservoir. Background Art

[0002] The critical rainfall of a reservoir refers to the maximum rainfall that a reservoir can withstand within a period of time under the condition of flood control safety, taking into account factors such as reservoir engineering parameters, operation and scheduling of water discharge facilities, soil moisture content in the catchment area, and runoff characteristics. Critical rainfall reflects the flood control capacity of a reservoir over a period of time and is often used as a method for reservoir flood risk warning. There are many small reservoirs, and their management experience is relatively lacking compared to large and medium-sized reservoirs. In order to enhance the ability of flood control emergency response and flood risk management in the basin, the need for real-time analysis and early warning of the critical rainfall of small reservoirs during the flood season has emerged.

[0003] At present, the critical rainfall analysis of small reservoirs mostly adopts the trial calculation interpolation method based on the whole process calculation of runoff generation and confluence of hydrological models and various simplified methods based on the principle of water balance.

[0004] In the process of implementing the present invention, the inventors found that there are at least the following problems in the prior art:

[0005] The trial calculation interpolation method based on the hydrological model requires complete runoff model parameters, but most small reservoirs lack historical data, making it difficult to directly calibrate and verify parameters. Most of them are solved by parameter transplantation. Unlike runoff parameters, the transplantation of runoff parameters has always been a difficult point in the field of hydrological technology, and huge errors are usually caused during the transplantation and conversion process. In addition, the trial calculation interpolation method has a large amount of calculations. The number of small reservoirs is large, the area is small, and the forecast period is short. The timeliness of flood warning is extremely high. This method is difficult to effectively meet the actual application needs of flood defense.

[0006] Simplified methods based on the principle of water balance often use methods such as runoff coefficient estimation and rainfall-runoff relationship interpolation to calculate the amount of water entering the reservoir. The calculated amount of water is usually the total amount of flood water entering the reservoir during the entire flood. However, in actual floods, the process of entering the reservoir is generally not completed when the reservoir reaches the highest water level, which often results in a smaller value of the calculated critical rainfall. In addition, this type of method also has problems such as insufficient consideration of the amount of water leaving the reservoir without gate control, and can only consider the total amount of precipitation but not the duration of the rainstorm, which greatly reduces its accuracy and practicality. Summary of the invention

[0007] The present invention provides a real-time and efficient early warning method for critical rainfall of a small reservoir taking into account the duration of a rainstorm. It only needs to transplant the flow parameters of the catchment area, and can accurately calculate the water discharge of the spillway with high accuracy. In addition, the method can take into account the duration of the rainstorm and does not require repeated trial calculations, which has high calculation efficiency and practicality.

[0008] The technical problem to be solved by the present invention is achieved by adopting the following technical solutions:

[0009] A real-time and efficient early warning method for dynamic critical rainfall of small reservoirs considering the duration of heavy rain includes the following steps: transplantation of rainfall-runoff relationship, calculation of reservoir critical rainfall, and early warning of reservoir disaster-causing heavy rain;

[0010] Transplantation of rainfall-runoff relationship: using high-resolution geospatial data to digitize and extract features of natural watersheds, and transplanting rainfall-runoff relationship parameters from data-available areas to small reservoir watersheds without data based on similarity analysis methods;

[0011] Calculation of critical rainfall for reservoirs: Comprehensively consider the factors affecting the previous rainfall in the basin, the real-time water volume, and the total water volume discharged from the reservoir under the conditions of the set rainstorm duration. Based on the graphical analysis method, the various stages of flood inflow, flood outflow, and water level change over time in the flood development process are finely divided. Finally, the transplanted rainfall-runoff relationship is used to calculate the critical rainfall value of the small reservoir.

[0012] Reservoir-caused rainstorm warning: Grid-match the numerical forecast results of meteorological precipitation with the catchment area of ​​small reservoir basins, and compare the estimated precipitation within the set rainstorm duration with the critical rainfall analysis results to achieve real-time warning of disaster-causing rainstorms.

[0013] Further technology of the present invention:

[0014] Preferably, the rainfall-runoff relationship transplant is specific:

[0015] Step 101: Using high-resolution geospatial data, extract attribute factors for basin similarity analysis. For small reservoirs without design data, extract their water level and storage capacity relationship curves based on high-precision terrain data;

[0016] Step 102: In step 102, the rank cumulative similarity matrix partitioning method is used for similarity analysis. The attributes of the divided basins must be standardized first, and then the Euclidean distance Dis between the small reservoir basin i without data and the basin j with data is calculated. δ,ij , and assign the rank by the distance, assign the rank of the basin j1 with the smallest Euclidean distance to the small reservoir basin i to 1, and the rank of the basin j2 with the second smallest distance to 2, and so on, assign the rank of all basins with this attribute;

[0017] Step 103: Repeat the above steps for all basin attributes, calculate the ranks of all attributes in the standardized set, obtain the sum of ranks between the small reservoir basin i and the basin with data j, select the basin with the smallest sum of ranks as the donor basin, and transplant its rainfall-runoff relationship to the small reservoir basin.

[0018] Preferably, the attribute factors of the watershed similarity analysis in step 101 include watershed area, area slope, watershed shape coefficient, land cover utilization type, and geological type, all of which are extracted in batches through high-resolution geospatial data such as DEM data, soil type data, geological type data, and land cover utilization data using geographic information technology for digital batch extraction.

[0019] Preferably, the formula for calculating the Euclidean distance is as follows:

[0020]

[0021] Preferably, the critical rainfall calculation of the reservoir is specifically:

[0022] Step 201: Generalize the flood process of the reservoir inflow and the flood process of the reservoir outflow into a triangle, where the peak flow of the flood inflow is set to Q B , and it is assumed that the water level in the reservoir changes linearly with time in the short period of time when the water level rises;

[0023] Step 202: Calculate the amount of water W discharged from the reservoir through the spillway before the reservoir water level rises to the set target water level during the flood. out , calculated according to the following formula:

[0024]

[0025] Where n is the number of points from the weir crest elevation to the set target water level in the reservoir discharge curve, and Z i and are the water level and discharge flow corresponding to each point in the discharge curve, Z 设 and Z 堰 are the target water level and the weir top elevation, t 泄 is the duration of the reservoir discharge greater than 0 before the water level reaches the target level. When calculating, we need to first calculate the proportion of the duration of the discharge greater than 0 in the total duration of the flood process. 泄 , and there is t 泄 =(t 雨 +τ)*T 泄 , t 雨 is the set rainstorm duration, τ is the basin runoff duration;

[0026] Step 203: Based on the relationship between the outflow volume during the water level rise phase, the inflow volume during the water level rise phase, and the reservoir storage volume during the water level rise phase, list the Q B is the unknown variable, and Q is obtained by solving the equation B The value of:

[0027]

[0028] In the formula, a and b are both V0 and V设 etc. Constants related to known variables;

[0029] On this basis, the runoff depth R corresponding to the critical rainfall of the reservoir is calculated, and the corresponding precipitation P in the P+Pa~R or P~Pa~R relationship curve is queried, which is the critical rainfall of the reservoir, where:

[0030]

[0031] Where R is the basin runoff depth, in mm; F ​​is the basin area, in km 2 ; W is the total amount of flood water entering the reservoir, in ten thousand cubic meters.

[0032] Preferably, in step 202, the proportion of the time when the discharge flow is greater than 0 in the total duration of the flood process is T 泄 The calculation formula is as follows:

[0033]

[0034] K1 and K2 are the duration proportions of the flooding section and the receding section of the flood process, respectively, which can be obtained by consulting the reservoir design report; Q D It is the reservoir discharge flow corresponding to the target water level. Its value is obtained by directly reading the reservoir water level-discharge relationship curve. In the absence of a discharge relationship curve, it can be calculated based on the relevant weir parameters of the reservoir and the applicable discharge formula.

[0035] Preferably, the runoff depth R is calculated from the total amount of flood water entering the reservoir W during the entire flood, which is proportional to the peak flow rate Q of the flood water entering the reservoir. B The relationship between them is as follows:

[0036] V0+W in -W out =V 设

[0037]

[0038] V0 is the storage capacity of the reservoir corresponding to the water level at the initial moment, V 设 The corresponding storage capacity of the reservoir for the set target water level can be obtained through the water level and storage capacity curve.

[0039] Preferably, the reservoir disaster-causing rainstorm warning is specifically:

[0040] Step 301: The calculation method of numerically predicted precipitation in the catchment area of ​​a small reservoir is as follows:

[0041]

[0042] Where i' and j' are the number of grids on the long side and wide side of the matrix grid surface, i'∈(1,2…m), j'∈(1,2…n); Pi',j' is the forecast precipitation value of the grid in the i'th row and j'th column in the numerical forecast product, S i',j' is the overlapping area of ​​the grid and the reservoir catchment area; F is the total area of ​​the reservoir catchment area;

[0043] Step 302: Conduct reservoir flood risk warning, calculate the critical rainfall P under the condition of set rainstorm duration t, and compare it with the forecast precipitation ∑P F For comparison, if P<∑P F , a flood risk warning will be issued for the reservoir.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] (1) The formula derivation of the present invention is mostly based on graphic analysis, which has strong logic, high operability and versatility, and is applicable to a wider range of small reservoirs than the prior art;

[0046] (2) Under current technical conditions, there is a large error in the migration of runoff parameters in the hydrological model. In the present invention, only relatively stable runoff parameters need to be migrated, which eliminates the migration process of runoff parameters in the prior art and can effectively improve the calculation accuracy.

[0047] (3) The parameters involved in the present invention are basically stable and do not change over time. In the process of software development and implementation, most steps can be configured in advance in the background, and no resources need to be occupied in real-time calculations. At the same time, there is no need to perform repeated trial calculations. Compared with the existing hydrological model trial calculation method, it is more efficient and more in line with the actual needs of small reservoir flood control;

[0048] (4) Compared with other existing simplified methods, this method clearly distinguishes the various stages of flood inflow, outflow and water level process over time in the flood development process without significantly increasing the amount of calculation, accurately calculates the outflow before the highest water level appears in the reservoir, eliminates the influence of runoff that does not contribute to the highest water level in the late flood period on the calculation, and greatly improves the calculation accuracy. In addition, it solves the problem that the traditional simplified method can only consider the total amount of precipitation but not the duration of precipitation, and its practicality is further enhanced.

[0049] (5) With the advancement of satellite, remote sensing and other technologies, large-scale, full-coverage geographic spatial data collection and application are becoming increasingly mature. The present invention makes better use of the latest scientific and technological achievements and has less demand for basic data such as historical materials. Compared with existing technologies, it has better prospects for promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solution of the present invention, the following is a brief introduction to the drawings required for the method introduction. Obviously, the drawings described below are some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0051] Figure 1 It is a schematic diagram of the method flow of the present invention.

[0052] Figure 2 This is a generalized schematic diagram of the flood inflow process, discharge process and water level process of a small reservoir.

[0053] Figure 3 This is a schematic diagram of the corresponding relationship between the reservoir characteristic water level and the discharge curve when calculating the reservoir discharge volume.

[0054] Figure 4 Schematic diagram of the relationship between the matrix grid and the catchment area of ​​a small reservoir when calculating forecast precipitation. DETAILED DESCRIPTION

[0055] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific embodiments.

[0056] The present invention provides a real-time and efficient early warning method for dynamic critical rainfall of a small reservoir considering the duration of a rainstorm, comprising the following technical steps:

[0057] Step 1: Transplant the rainfall-runoff relationship. The calculation of reservoir inflow requires the rainfall-runoff relationship of the catchment area as support, but small reservoirs generally lack historical hydrological data and cannot directly calibrate runoff parameters. However, for specific areas, when the climate and underlying surface conditions are basically the same, the runoff characteristics of the basin are relatively stable, and directly transplanting the rainfall-runoff relationship in the area with data has higher accuracy.

[0058] Step 101: Obtain high-resolution geospatial data such as DEM data, soil type data, geological type data, land use / cover data, etc. in the study area, digitize natural sub-basins through geographic information technology, and extract basic hydrological characteristics of each basin, such as area, area slope, basin shape coefficient, land cover / use type, geological type, etc., as attribute factors for basin similarity analysis.

[0059] Step 102: For small reservoirs without design data, their water level-reservoir capacity relationship curve can be extracted based on high-precision terrain data.

[0060] Step 103: A regionalization method based on rank-accumulated similarity matrix is ​​used to divide similar watersheds. This method is a physical similarity method. The specific calculation steps are as follows:

[0061] Standardize the attributes of the divided watershed to obtain a standardized set of watershed attributes, recorded as Set m,n , where m is the number of selected watershed attributes and n is the number of watersheds divided in the study area;

[0062] For any basin attribute δ, calculate the Euclidean distance Dis between the small reservoir basin i without data and the basin j with data. δ,ij :

[0063]

[0064] For the basin attribute δ, the rank assignment of the basin j1 with the smallest Euclidean distance to the small reservoir basin i is The rank of the basin j2 with the second smallest distance is And so on, the ranks of all watersheds are assigned.

[0065] Repeat the above steps for all basin attributes, calculate the ranks of all attributes in the standardized set, and obtain the rank sum Sr between the small reservoir basin i and the basin j with data ij :

[0066]

[0067] Select the rank and Sr ij The smallest basin j with data is used as the donor basin of small reservoir i, and the rainfall-runoff relationship of basin j is transplanted to the small reservoir basin i;

[0068] Step 2: Calculate the critical rainfall of the reservoir. Taking into account various factors such as the early soil moisture content, real-time storage capacity, and the amount of water discharged from the spillway within a set period of time, drawing on the design results of small reservoirs, the critical rainfall of small reservoirs is calculated using a method based on flood process generalization. The specific technical steps are as follows:

[0069] Step 201: Most small reservoirs are located in hilly areas, with small watersheds and fast flood convergence. Under the influence of heavy rains, the water level in the reservoir rises and falls sharply. Therefore, in the field of small reservoir design, the flood process line of small reservoirs is often generalized into a triangle. In addition, the watershed characteristics of small reservoirs determine that the flooding time of the reservoir is relatively short. To simplify the calculation, this method assumes that the water level Z of the small reservoir in the short-term flooding period is linearly related to the time t.

[0070] Step 202: When calculating the design flood of the reservoir, the starting water level is usually the weir crest elevation. In addition, when the reservoir water level is lower than the weir crest elevation, the remaining flood control storage capacity of the reservoir is large and there is no flow discharge, so the flood control risk is low. In view of this, the present invention mainly describes the critical rainfall calculation method when the water level at the initial moment is the weir crest elevation. At this time, the reservoir's inflow flood process ABC, discharge process ADE, and water level process LMN are as shown in the attached figure. Figure 2 shown.

[0071] In the figure, point D indicates that the inflow is equal to the outflow. At this time, the inflow and outflow are balanced and the water level reaches the highest point Z. M , it is not difficult to understand that there is Z M = set target water level. In addition, it can be seen from the figure that t H The amount of water entering the reservoir after time S ΔHDC and outflow water volume S HDE There is no impact on the maximum water level of the reservoir.

[0072] Step 203: Calculate the invalid flow generation and confluence time t when the corresponding flood occurs C -t H The proportion of flood events during the flood 无效产流 , attached Figure 2 In the equation ΔBGC≈ΔDHC, according to the similar triangle theory, we know that Right now

[0073] In the formula, Q D is the reservoir discharge flow corresponding to the set target water level, that is, Figure 2 DH can be obtained by reading the water level and discharge relationship; Q B is the generalized inflow peak flow, namely Figure 2 Medium BG, currently unknown.

[0074] Further calculations yield

[0075]

[0076] Where K1 and K2 are the proportion of the duration of the flood stage and the proportion of the duration of the water receding stage in the flood process entering the reservoir, that is, AG=K1*AC, GC=K2*AC. K1 and K2 can be obtained by referring to the reservoir design report. In the absence of design data, K1 can generally be taken as 1 / 3 to 1 / 2.

[0077] Step 204: Calculate the proportion of the time period during which the reservoir discharge is greater than 0 before the reservoir reaches the highest water level in the flood process T 泄 , by the attached Figure 2 It can be seen that:

[0078]

[0079] Substituting formula (3) into formula (4), we can obtain:

[0080]

[0081] Step 205: From this, it can be calculated that the rainstorm duration is set to t 雨 Under the condition of , the time t for water to flow down through the spillway before the reservoir reaches the highest water level 泄 for:

[0082] t 泄 =(t 雨 +τ)*T 泄 (Formula 6)

[0083] Where τ is the confluence duration of the small reservoir, which can be obtained through geographic information technology analysis or by referring to relevant design documents.

[0084] Step 206: Calculate the amount of water discharged from the reservoir through the spillway during the process of the reservoir water level rising from the initial moment to the set water level under the set rainstorm duration condition. Similarly, taking the calculation of the critical rainfall to reach the design water level as an example, the characteristic water levels of the reservoir, the water level-discharge relationship curve, and the water level-storage capacity relationship curve are shown in the attached figure. Figure 3 As shown;

[0085] In this method, according to the characteristics of small reservoir floods, the water level and time in the flooding stage of the reservoir are generalized into a linear relationship. Figure 3 For example, the water level rises from Z1 to Z2. The amount of water discharged from the reservoir through the spillway during this period It can be expressed as:

[0086]

[0087] In the formula, Z 设 and Z 堰 are the target water level and weir top elevation, respectively. and are the discharge flows when the reservoir water level is Z1 and Z2, respectively, which can be obtained by querying the water level discharge curve. By analogy for other periods, the total amount of flood discharged through the spillway during the process of the reservoir water level rising from the initial moment to the design water level can be calculated as:

[0088]

[0089] Where n is the number of points between the weir crest elevation and the set target water level in the reservoir discharge curve, and Z i and are the water level and discharge flow corresponding to each point in the discharge curve respectively.

[0090] Step 207: Calculate the amount of water W that enters the reservoir before it reaches the highest water level inAccording to the water balance principle, we have:

[0091] V0+W in -W out =V 设 (Formula 9)

[0092] In the formula, V0 is the water storage capacity of the reservoir at the initial moment, V 设 The water storage capacity corresponding to the set target water level can be read through the reservoir capacity curve.

[0093] but

[0094] W in =V 设 -V0+W out (Formula 10)

[0095] It is not difficult to understand that when the water level at the initial moment is the weir top elevation, W in Corresponding attachment Figure 2 The area of ​​quadrilateral ABDH.

[0096] Step 208: Based on the similarity of ΔBGC≈ΔDHC, W in Expressed as S ΔABC According to the triangle similarity theory, Figure 2 middle:

[0097]

[0098] again

[0099]

[0100] Combining equations (11) and (12), we can obtain:

[0101]

[0102] but

[0103]

[0104] Step 209: Calculate the total amount of flood water entering the reservoir during this flood. According to the triangle area formula, we have:

[0105]

[0106] Combining equations (4), (6), (10), (14) and (15), we get:

[0107]

[0108] In the formula, except Q B is an unknown variable, and the others are known. After simplifying equation (16), we can get:

[0109]

[0110] in:

[0111] Therefore, the total amount of flood water W entering the reservoir during this flood can be calculated using the triangle area formula, namely:

[0112] W=0.5*Q B *(t 雨 +τ)(Equation 19)

[0113] Step 210: Comprehensively consider the previous soil moisture content of the watershed and calculate the critical rainfall P based on the transplanted rainfall-runoff relationship. The specific method is as follows:

[0114] The basin runoff depth R is calculated based on the amount of water W entering the reservoir during each flood:

[0115]

[0116] Where R is the basin runoff depth, in mm; F ​​is the basin area, in km 2 ; W is the total amount of flood water entering the reservoir, unit: ten thousand cubic meters.

[0117] According to the calculated R and Pa, query the corresponding precipitation in the P+Pa~R or P~Pa~R relationship curve. The rainfall value P is the water level at the initial moment, which is the elevation of the weir top. The duration of the rainstorm is t 雨 The critical rainfall for the reservoir to reach the set target water level under certain conditions. Among them, Pa is the previous impact rainfall, which is calculated continuously on a daily basis since the beginning of the flood season.

[0118] Step 3: Reservoir-caused rainstorm warning. Grid-match the numerical forecast results of meteorological precipitation with the catchment area of ​​the small reservoir basin, and compare the estimated precipitation within the set rainstorm duration with the critical rainfall analysis results to achieve real-time and efficient warning of disaster-causing rainstorms. The specific implementation methods are as follows:

[0119] Step 301: Calculate the numerical forecast precipitation in the small reservoir catchment area. Based on the numerical forecast precipitation grid, an m×n matrix grid surface is established within the small reservoir catchment area. The principle of grid establishment is that the distribution range should be slightly larger than the outer boundary of the basin, such as the attached Figure 4 As shown in the figure, the numerically predicted rainfall P in a single period of time in the reservoir catchment area F The area-weighted average method is calculated as follows:

[0120]

[0121] Where i' and j' are the number of grids on the long side and wide side of the matrix grid surface, i'∈(1,2…m), j'∈(1,2…n); Pi',j' is the forecast precipitation value of the grid in the i'th row and j'th column in the numerical forecast product, S i',j' is the overlapping area of ​​the grid and the reservoir catchment area; F is the total area of ​​the reservoir catchment area.

[0122] Step 302: Conduct reservoir flood risk warning. Calculate the critical rainfall P under the condition of a set rainstorm duration t, and accumulate the numerical forecast precipitation of the reservoir catchment area in the future time t according to the time period according to formula (21) to obtain the total forecast precipitation ∑P F :

[0123] If P<∑P F , a flood risk warning will be issued for the reservoir to remind the public to pay attention to risk prevention.

[0124] Through examples, the key steps in this method are further explained and verified. Taking the Qingnian Reservoir in Shandong Province as an example, this reservoir is a small (2) type reservoir mainly used for flood control and farmland irrigation, with a controlled basin area of ​​5.4km 2 , the length of the river is 4.17km, the comprehensive decline of the river is 1.9%, the landform is mainly erosion-erosion hills, there are many rocks in the basin, the soil layer is thin, the vegetation is general, and it belongs to the mountainous area. After similarity analysis and comparison with the nearby basins with data, the rainfall-runoff relationship of the nearby Nishan Reservoir was selected for transfer. After consulting the relevant design documents, the flood limit water level of the Qingnian Reservoir is 170.30m, the design water level is 173.26m, the verification water level is 174.54m, K1 and K2 are 1 / 3 and 2 / 3 respectively, the average confluence time of the basin is 0.5h, and the relationship between water level storage capacity and discharge capacity is shown in Table 1.

[0125] Table 1: Relationship table between water level and storage capacity, and water level and discharge of Qingnian Reservoir.

[0126] Water level H(m) 170.3 171 171.5 172 172.5 173 173.5 174 174.5 175 <![CDATA[Storage capacity V (10,000 m 3 )]]> 0.95 2.08 3.22 4.83 6.9 9.46 12.32 15.29 18.33 21.38 <![CDATA[Discharge Q (m 3 / s)]]> 0 12.3 27.61 46.55 68.53 93.17 120.21 149.46 180.76 213.98

[0127] Through calculation, when the real-time water level of the reservoir reaches the flood limit water level of 170.30m, the critical rainfall from the flood design water level and the flood limit water level under various previous soil moisture levels is shown in Table 2.

[0128] Table 2: Calculation results of critical rainfall of Qingnian Reservoir.

[0129]

[0130] On this basis, the numerical model precipitation forecast results for the reservoir catchment area in the next 1 to 6 hours can be assigned based on the reservoir catchment area range and the grids divided by the numerical model, and the system can determine whether to issue a reservoir-causing rainstorm warning based on actual conditions.

[0131] In summary, the use of this method to calculate the critical rainfall of the reservoir does not require repeated trial calculations, is easy to implement through programming, and can more finely consider the impact of the amount of water discharged from the reservoir through the spillway and different rainstorm intensities on the critical rainfall. The method derivation process and calculation results are logical, and the characteristics of short-duration rainstorms are more in line with the actual needs of flood defense in small reservoirs. Compared with existing methods, both practicality and accuracy have been improved.

[0132] The above shows and describes the basic principles, main features and characteristics of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of the present invention to be protected is defined by the attached claims and their equivalents.

Claims

1. A real-time and efficient early warning method for dynamic critical rainfall of small reservoirs considering the duration of heavy rain, characterized by: The following steps are involved: Transplantation of rainfall-runoff relationship, calculation of critical rainfall of reservoirs, and early warning of rainstorms that may cause disasters in reservoirs; Transplantation of rainfall-runoff relationship: using high-resolution geospatial data to digitize and extract features of natural watersheds, and transplanting rainfall-runoff relationship parameters from data-available areas to small reservoir watersheds without data based on similarity analysis methods; Calculation of critical rainfall for reservoirs: Comprehensively consider the factors affecting the previous rainfall in the basin, the real-time water volume, and the total water volume discharged from the reservoir under the conditions of the set rainstorm duration. Based on the graphical analysis method, the various stages of flood inflow, flood outflow, and water level change over time in the flood development process are finely divided. Finally, the transplanted rainfall-runoff relationship is used to calculate the critical rainfall value of the small reservoir. Reservoir-caused rainstorm warning: Grid-match the numerical forecast results of meteorological precipitation with the catchment area of ​​small reservoir basins, and compare the estimated precipitation within the set rainstorm duration with the critical rainfall analysis results to achieve real-time warning of disaster-causing rainstorms.

2. The real-time and efficient early warning method for dynamic critical rainfall of small reservoirs taking into account the duration of heavy rain according to claim 1 is characterized by: Specific information about rainfall-runoff relationship transplantation: Step 101: Using high-resolution geospatial data, extract attribute factors for basin similarity analysis. For small reservoirs without design data, extract their water level and storage capacity relationship curves based on high-precision terrain data; Step 102: In step 102, the rank cumulative similarity matrix partitioning method is used for similarity analysis. The attributes of the divided basins must be standardized first, and then the Euclidean distance Dis between the small reservoir basin i without data and the basin j with data is calculated. δ,ij , and the rank is assigned by the distance. The rank of the basin j1 with the smallest Euclidean distance to the small reservoir basin i is assigned to 1, and the rank of the basin j2 with the second smallest distance is assigned to 2. And so on, the ranks of all basins with this attribute are assigned; Step 103: Repeat the above steps for all basin attributes, calculate the ranks of all attributes in the standardized set, obtain the sum of ranks between the small reservoir basin i and the basin with data j, select the basin with the smallest sum of ranks as the donor basin, and transplant its rainfall-runoff relationship to the small reservoir basin.

3. The real-time and efficient early warning method for dynamic critical rainfall of small reservoirs taking into account the duration of heavy rain according to claim 2 is characterized by: The attribute factors of the watershed similarity analysis in step 101 include watershed area, area slope, watershed shape coefficient, land cover utilization type, and geological type, all of which are extracted in batches through high-resolution geographic spatial data such as DEM data, soil type data, geological type data, and land cover utilization data using geographic information technology.

4. The real-time and efficient early warning method for dynamic critical rainfall of small reservoirs taking into account the duration of heavy rain according to claim 2 is characterized by: The formula for calculating Euclidean distance is as follows:

5. The real-time and efficient early warning method for dynamic critical rainfall of small reservoirs taking into account the duration of heavy rain according to claim 1 is characterized by: Calculation of critical rainfall for reservoirs: Step 201: Generalize the flood process of the reservoir inflow and the flood process of the reservoir outflow into a triangle, where the peak flow of the flood inflow is set to Q B , and it is assumed that the water level in the reservoir changes linearly with time in the short period of time when the water level rises; Step 202: Calculate the amount of water W discharged from the reservoir through the spillway before the reservoir water level rises to the set target water level during the flood. out , calculated according to the following formula: Where n is the number of points from the weir crest elevation to the set target water level in the reservoir discharge curve, and Z i and are the water level and discharge flow corresponding to each point in the discharge curve, Z 设 and Z 堰 are the target water level and the weir top elevation, t 泄 is the duration of the reservoir discharge greater than 0 before the water level reaches the target level. When calculating, we need to first calculate the proportion of the duration of the discharge greater than 0 in the total duration of the flood process. 泄 , and there is t 泄 =(t 雨 +τ)*T 泄 , t 雨 is the set rainstorm duration, τ is the basin runoff duration; Step 203: Based on the relationship between the outflow volume during the water level rise phase, the inflow volume during the water level rise phase, and the reservoir storage volume during the water level rise phase, list the Q B is the unknown variable, and Q is obtained by solving the equation B The value of: In the formula, a and b are both V0 and V 设 etc. Constants related to known variables; On this basis, the runoff depth R corresponding to the critical rainfall of the reservoir is calculated, and the corresponding precipitation P in the P+Pa~R or P~Pa~R relationship curve is queried, which is the critical rainfall of the reservoir, where: Where R is the basin runoff depth, in mm; F ​​is the basin area, in km 2 ; W is the total amount of flood water entering the reservoir, in ten thousand cubic meters.

6. The real-time and efficient early warning method for dynamic critical rainfall of small reservoirs taking into account the duration of heavy rain according to claim 5 is characterized by: In step 202, the proportion of the time when the discharge flow is greater than 0 in the total duration of the flood process is T 泄 The calculation formula is as follows: K1 and K2 are the duration proportions of the flooding section and the receding section of the flood process, respectively, which can be obtained by consulting the reservoir design report; Q D It is the reservoir discharge flow corresponding to the target water level. Its value is obtained by directly reading the reservoir water level-discharge relationship curve. In the absence of a discharge relationship curve, it can be calculated based on the relevant weir parameters of the reservoir and the applicable discharge formula.

7. The real-time and efficient early warning method for dynamic critical rainfall of small reservoirs taking into account the duration of heavy rain as described in claim 6 is characterized by: The runoff depth R is calculated from the total amount of flood water entering the reservoir during the entire flood, W, which is proportional to the peak flow rate of the flood water entering the reservoir, Q. B The relationship between them is as follows: V0+W in -IN out =V 设 V0 is the storage capacity of the reservoir corresponding to the water level at the initial moment, V 设 The corresponding storage capacity of the reservoir for the set target water level can be obtained through the water level and storage capacity curve.

8. The real-time and efficient early warning method for dynamic critical rainfall of small reservoirs taking into account the duration of rainstorms according to claim 7 is characterized by: The specific warnings for rainstorms causing disasters in reservoirs are as follows: Step 301: The calculation method of numerically predicted precipitation in the catchment area of ​​a small reservoir is as follows: Where i' and j' are the number of grids on the long side and wide side of the matrix grid surface, i'∈(1,2…m), j'∈(1,2…n); P i',j' is the forecast precipitation value of the grid in the i'th row and j'th column in the numerical forecast product, S i',j' is the area of ​​overlap between the grid and the reservoir catchment area; F is the total area of ​​the reservoir catchment; Step 302: Conduct reservoir flood risk warning, calculate the critical rainfall P under the condition of set rainstorm duration t, and compare it with the forecast precipitation ∑P F For comparison, if P<∑P F , a flood risk warning will be issued for the reservoir.

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