Method for determining river section water level and flow relation

Abstract

The invention discloses a river section water level flow relation determination method, and belongs to the technical field of hydraulic engineering, and the method comprises the steps: S1, obtaining the parameter information of a river section; s2, generating a river cross-section diagram of a river cross-section based on the parameter information in the step S1; s3, determining characteristic parameters of the river section according to the river section diagram; s4, determining Manning roughness coefficients of different river sections; s5, determining a water level flow relation based on the characteristic parameters and a Manning roughness coefficient; according to the method for determining the river section water level and flow relationship, the relationship with the section flow is established on the basis of the water level combination of the three observation stations, so that a rope sleeve curve is avoided, and meanwhile, the obtained relationship is higher in uniqueness and more accurate in use.

Description

Technical Field

[0001] The present invention relates to the technical field of water conservancy engineering, and particularly relates to a method for determining the water level - discharge relationship of a river cross - section. Background Technique

[0002] In the traditional method for determining the water level - discharge relationship of a river cross - section, data from a single water level measuring station is usually used to establish the relationship between water level and discharge. However, the existing methods have the following problems:

[0003] (1) Loop - rating curve phenomenon: Due to the influence of flood rise and fall, the riverbed morphology and water flow acting forces change, resulting in a complex "loop - rating curve" characteristic in the relationship between water level and discharge. This non - linear relationship makes prediction and management more difficult.

[0004] (2) Large errors: Single - point measurement is difficult to comprehensively reflect the water flow conditions of the entire cross - section. Especially in complex terrain or high - water - level situations, large measurement errors are likely to occur.

[0005] (3) Lack of uniqueness: Based on data from a single measuring station, it is impossible to ensure that the established water level - discharge relationship has sufficient uniqueness and stability, which further affects the accuracy of prediction. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for determining the water level - discharge relationship of a river cross - section to solve the problems existing in the above - mentioned background technique.

[0007] To achieve the above - mentioned purpose, the present invention provides a method for determining the water level - discharge relationship of a river cross - section, including the following steps:

[0008] Step S1: Obtain the parameter information of the river cross - section;

[0009] Step S2: Generate a river cross - section diagram of the river cross - section based on the parameter information in Step S1;

[0010] Step S3: Determine the characteristic parameters of the river cross - section according to the river cross - section diagram;

[0011] Step S4: Determine the Manning roughness coefficient of different river cross - sections;

[0012] Step S5: Determine the water level - discharge relationship based on the characteristic parameters and the Manning roughness coefficient.

[0013] Preferably, Step S1 specifically includes the following steps:

[0014] Step S11: Add water level measuring stations at the upstream and downstream of the river cross - section respectively. There are a total of three water level measuring stations, including Water Level Measuring Station 1, Water Level Measuring Station 2, and Water Level Measuring Station 3. Determine the spacing between adjacent water level measuring stations according to the river channel length and topographic changes.

[0015] Step S12: At each water level measurement station, measurement points are arranged at a certain interval between the two banks of the river section. The interval is generally determined according to the river width and the complexity of the terrain.

[0016] Step S13: Collect flow data. Water level data is collected simultaneously at three water level measurement stations. The collection frequency is determined according to the water flow variation of the river. At the same time, the water level data of the corresponding water level measurement stations is recorded synchronously. The collected water level data and flow data are paired according to the measurement time to ensure that each set of flow data has the corresponding water level data of the three stations. Check the accuracy and integrity of the data, and eliminate the obviously incorrect or unreasonable data points.

[0017] Preferably, step S3 specifically includes the following steps:

[0018] Step S31: According to the cross-sectional shape of the river section diagram drawn in step S2, it is divided into several regular rectangles and trapezoids. Calculate the areas of each rectangle and trapezoid respectively, and accumulate to obtain the cross-sectional area A of the water passage.

[0019] Step S32: Calculate the wetted perimeter according to the cross-sectional shape of the river section diagram drawn in step S2, and calculate the total wetted perimeter P according to the contact length between the water and the section.

[0020] Step S33: Calculate the hydraulic radius according to the formula where A is the cross-sectional area of the water passage obtained in step S31, and P is the total wetted perimeter obtained in step S32.

[0021] Step S34: Calculate the average depth of the section. The formula is: where B is the water surface width.

[0022] Preferably, the Manning roughness coefficient in step S4 is determined according to the composition of the river bed surface in the corresponding area of different water level measurement stations. The Manning roughness coefficient of each area adopts a comprehensive roughness coefficient that can reflect the overall composition of the river bed surface in the area, or takes different values according to the composition of the river bed surface in different areas.

[0023] Preferably, in step S5, on the basis of calculating the characteristic parameters, the water surface slope is calculated simultaneously. The formula is:

[0024]

[0025] where Δh is the water level difference obtained from the water level measurement stations set upstream and downstream; L is the horizontal distance between the two sections.

[0026] Preferably, step S5 specifically includes the following steps:

[0027] Step S51: Adopt the Manning formula To establish the water level - discharge relationship, calculate the discharges in the areas between the cross - sections of gauge station 1 and gauge station 2, gauge station 1 and gauge station 3, and gauge station 2 and gauge station 3 respectively. Here, k is the correction coefficient, Q is the discharge, and n is the Manning roughness coefficient;

[0028] Step S52: Sum up the discharges between the cross - sections of each gauge station calculated in Step S51 and then take the average to obtain the discharge data under different water level combinations of the three gauge stations; conduct the same monitoring and calculation for different flow processes, and record the discharge and the water level data of the three gauge stations;

[0029] Step S53: Draw the relationship curves between the water levels of the three cross - sections and the river discharge based on the data obtained in Step S52, so as to determine the water level - discharge relationship.

[0030] Preferably, the specific method for drawing the relationship curves in Step S53 is as follows:

[0031] Determine the water level value of gauge station 1. Given the water level value of a certain gauge station 3, draw the discharge - water level curve with the water level of gauge station 2 as the abscissa and the discharge as the ordinate. Draw such curves for different water levels of gauge station 3 to obtain a set of curve clusters; change the water level of gauge station 1 and draw another set of curve clusters according to the above steps; for different water levels of gauge station 1, obtain several sets of curve clusters.

[0032] Therefore, by adopting the above - mentioned method for determining the water level - discharge relationship of a river cross - section, the present invention has the following beneficial effects:

[0033] (1) By adding gauges upstream and downstream and introducing the water level combination data of the three gauges, it can more comprehensively reflect the water flow characteristics of the river. For example, when there are complex situations such as backwater and floodplain in the river, the water level data of multiple gauges can comprehensively reflect the changes in water flow, providing a more accurate basis for discharge calculation and effectively reducing the discharge calculation error caused by local water flow anomalies;

[0034] (2) By comprehensively considering the upstream and downstream water levels, it can, to a certain extent, eliminate the interference of these complex factors on discharge determination. The water level combination of the three gauges forms a more characteristic input condition, making each water level - discharge combination more unique and avoiding the relationship confusion caused by complex factors in traditional methods;

[0035] (3) Greatly simplifies the process of discharge calculation, reduces manual intervention and complex chart analysis processes, and improves work efficiency;

[0036] (4) By calculating and analyzing a large amount of data to determine the model parameters, the model can predict the discharge more accurately under different water flow conditions, improving the accuracy of discharge calculation.

[0037] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Description of the Drawings

[0038] Figure 1 It is a flowchart of a method for determining the water level - discharge relationship of a river cross - section according to the present invention;

[0039] Figure 2 It is a schematic diagram of the relationship curve between the water level and discharge of the second water level gauging station when the water level of the first water level gauging station is 1130 m in an embodiment of the present invention. Detailed Embodiments

[0040] The following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0041] Please refer to Figure 1 , a method for determining the water level - discharge relationship of a river cross - section, comprising the following steps:

[0042] Step S1: Obtain the parameter information of the river cross - section, specifically including the following steps:

[0043] Step S11: Select suitable positions to add water level gauging stations respectively upstream and downstream of the river cross - section. There are a total of three water level gauging stations, including the first water level gauging station, the second water level gauging station, and the third water level gauging station. The site selection should consider stable water flow conditions, avoiding complex water flow areas such as bends and confluences of tributaries. At the same time, it is necessary to ensure that the terrain around the gauging station is open, which is convenient for instrument installation and maintenance. The distances between the upstream and downstream gauging stations and the existing cross - section are generally determined according to the length of the river, the characteristics of the river channel, and the water flow variation, and can range from several hundred meters to several kilometers;

[0044] Step S12: At each water level gauging station, arrange measurement points at a certain interval between the two banks of the river cross - section. The interval is generally determined according to the width of the river channel and the complexity of the terrain;

[0045] Step S13: Collect flow data. The three water level gauging stations collect water level data simultaneously. The collection frequency is determined according to the water flow variation of the river. Generally, during the flood period, it can be encrypted to collect once every 5 - 10 minutes, and during the normal water period and the dry water period, it can be collected once every 30 minutes - 60 minutes. Ensure that the collected data is continuous and complete. When measuring the flow, record the water level data of the corresponding water level gauging station simultaneously, and pair the collected water level data and flow data according to the measurement time to ensure that each set of flow data has the corresponding water level data of the three gauging stations.

[0046] Preprocess the collected data to ensure data validity, including:

[0047] 1. Check data integrity: Check whether there are missing measurement points or missing data. If so, supplement the measurement in time or perform reasonable interpolation estimation based on surrounding data.

[0048] 2. Eliminate abnormal data: Check whether there are outliers that deviate significantly from other data in the data, such as data errors caused by measurement instrument failures, human errors, etc. Outliers can be identified and eliminated by methods such as plotting scatter plots and calculating statistics.

[0049] 3. Data calibration: Calibrate the measurement data according to the calibration parameters of the measurement instrument and the known standard point data to eliminate the influence of factors such as instrument errors.

[0050] Step S2: Generate a river cross-section diagram of the river cross-section based on the parameter information in Step S1;

[0051] Step S3: Determine the characteristic parameters of the river cross-section according to the river cross-section diagram, specifically including the following steps:

[0052] Step S31: According to the cross-section shape of the river cross-section diagram drawn in Step S2, divide it into several regular rectangles and trapezoids, calculate the areas of each rectangle and trapezoid respectively, and accumulate to obtain the cross-sectional area A of the water-crossing section. For irregular cross-sections, approximate methods can be used for division;

[0053] Step S32: Calculate the wetted perimeter according to the cross-section shape of the river cross-section diagram drawn in Step S2, and calculate the total wetted perimeter P according to the contact length between water and the cross-section;

[0054] Step S33: Calculate the hydraulic radius according to the formula where A is the cross-sectional area of the water-crossing section obtained in Step S31, and P is the total wetted perimeter obtained in Step S32;

[0055] Step S34: Calculate the average cross-sectional water depth, and the formula is: where B is the water surface width.

[0056] Step S4: Determine the Manning roughness coefficient of different river cross-sections; take values according to the composition of the riverbed surface in the corresponding areas of different water level gauging stations. The Manning roughness coefficient of each area adopts a comprehensive roughness coefficient that can reflect the overall composition of the riverbed surface in the area, or different values are taken according to the composition of the riverbed surface in different areas.

[0057] Step S5: Determine the water level-discharge relationship based on the characteristic parameters and the Manning roughness coefficient, specifically including the following steps:

[0058] Step S51: Adopt the Manning formula To establish the water level - discharge relationship, calculate the discharge in the areas between the cross - sections of gauge station 1 and gauge station 2, gauge station 1 and gauge station 3, and gauge station 2 and gauge station 3 respectively. Here, k is the correction coefficient, Q is the discharge, and n is the Manning roughness coefficient;

[0059] Step S52: Calculate the water surface slope. The formula is:

[0060]

[0061] where Δh is the water level difference obtained from the water level gauges set upstream and downstream; L is the horizontal distance between the two cross - sections;

[0062] Step S53: Sum up the discharges between the cross - sections where each water level gauge is located calculated in Step S51 and then take the average to obtain the discharge data under different water level combinations of the three water level gauges; conduct the same monitoring and calculation for different discharge processes, and record the discharge and the water level data of the three water level gauges;

[0063] Step S54: Draw the relationship curve between the water levels of the three cross - sections and the river discharge based on the data obtained in Step S52, so as to determine the water level - discharge relationship. The specific method for drawing the relationship curve is as follows:

[0064] Determine the water level value of gauge station 1. Given the water level value of a certain gauge station 3, draw the discharge - water level curve with the water level of gauge station 2 as the abscissa and the discharge as the ordinate. Draw such curves for different water levels of gauge station 3 to obtain a set of curve clusters; change the water level of gauge station 1 and draw another set of curve clusters according to the above steps; for different water levels of gauge station 1, obtain several sets of curve clusters.

[0065] Establish a water level - discharge relationship model with the water level combinations of the three gauges as the independent variable and the cross - section discharge as the dependent variable. For example, using a multiple linear regression model can be expressed as: Q = a×H1 + b×H2 + c×H3 + d, where H1, H2, and H3 are the water levels of the upstream, existing cross - section, and downstream gauges respectively, a, b, and c are the regression coefficients, and d is the constant term. Using non - linear regression can be expressed as: Q = eH f f, where H is the water level, and e and f are the regression coefficients. By calculating and analyzing a large amount of data, determine the values of the regression coefficients and the constant term, so as to obtain the specific water level - discharge relationship model. The water level - discharge relationship models obtained by the two methods can be compared to obtain the optimal water level - discharge relationship model.

[0066] Select some measured discharge data at different time periods from those used when establishing the model as the comparison samples, compare the discharges calculated by the model in this embodiment with the measured discharges, and calculate the absolute error and relative error. The formulas are:

[0067] Absolute error = |Q计算 -Q 实测 |;

[0068]

[0069] If the error is small, the obtained model can be used as the water level-discharge relationship model.

[0070] If the error is large, analyze the reasons and appropriately adjust parameters such as the Manning roughness coefficient and correction coefficient, recalculate the flow rate and compare it with the measured data until the error meets the requirements.

[0071] Therefore, the present invention adopts the above method for determining the water level-discharge relationship of a river cross-section. By introducing upstream and downstream gauging stations, multi-dimensional water level data comprehensively reflects the water flow characteristics. In combination with a multivariate mathematical model, it accurately fits the water level-discharge relationship and reduces the calculation error. Based on the water level combination of three gauging stations, a relationship with the cross-section flow rate is established, which avoids the rope curve. At the same time, the obtained relationship is more unique and more accurate in use.

[0072] In this embodiment, the water level-discharge relationship curve obtained by this method is as Figure 2 shown Figure 2 It is a schematic diagram of the curve relationship between the water level of gauging station two and the flow rate when the water level of gauging station one is 1130 m. Each curve in the figure represents the water level of different gauging stations three.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for determining the relationship between water level and flow rate in a river section, characterized in that: The following steps are involved: Step S1, obtaining parameter information of a river section; Step S2, generating a river cross-section diagram of the river cross-section based on the parameter information of step S1; Step S3, determining characteristic parameters of the river section according to the river section diagram; Step S4, determining the Manning roughness coefficient of different river sections; Step S5: determining the water level-flow relationship based on the characteristic parameters and the Manning roughness coefficient.

2. A method for determining the relationship between water level and flow rate in a river section according to claim 1, characterized in that: Step S1 specifically includes the following steps: Step S11, adding water level measuring stations at the upstream and downstream of the river section, a total of three water level measuring stations, including water level measuring station 1, water level measuring station 2 and water level measuring station 3, and determining the spacing between adjacent water level measuring stations according to the length of the river channel and the change of terrain; Step S12: at each water level measuring station, measuring points are arranged at a certain interval between the two banks of the river section; Step S13, collecting flow data, and synchronously recording the water level data of the corresponding water level measuring stations, pairing the collected water level data and flow data according to the measurement time, and ensuring that each set of flow data has corresponding water level data of the three water level measuring stations.

3. The method for determining the relationship between water level and flow rate of a river section according to claim 1, characterized in that: Step S3 specifically includes the following steps: Step S31, dividing the cross-sectional shape of the river cross-sectional diagram drawn in step S2 into a number of regular rectangles and trapezoids, calculating the area of ​​each rectangle and trapezoid respectively, and accumulating to obtain the area A of the water-passing cross-sectional area; Step S32, calculating the wetted perimeter according to the cross-sectional shape of the river cross-sectional diagram drawn in step S2, and calculating the total wetted perimeter P according to the contact length between water and the cross-sectional shape; Step S33: According to the formula Calculate the hydraulic radius, where A is the water flow cross-sectional area obtained in step S31, and P is the total wetted perimeter obtained in step S32; Step S34, calculate the average water depth of the section, the formula is: Where B is the width of the water surface.

4. The method for determining the relationship between water level and flow rate in a river section according to claim 1, characterized in that: The Manning's roughness coefficient in step S4 is determined according to the composition of the riverbed in the areas corresponding to different water level measuring stations. The Manning's roughness coefficient of each area adopts a comprehensive roughness coefficient that can reflect the composition of the riverbed in the entire area, or takes different values ​​according to the composition of the riverbed in different areas.

5. The method for determining the relationship between water level and flow rate of a river section according to claim 2, characterized in that: In step S5, on the basis of calculating the characteristic parameters, the water surface gradient is calculated at the same time, and the formula is: Among them, Δh is the water level difference obtained according to the water level measuring stations set up upstream and downstream; L is the horizontal distance between the two sections.

6. A method for determining the relationship between water level and flow rate in a river section according to claim 3, characterized in that: Step S5 specifically includes the following steps: Step S51: Using the Manning formula To establish the relationship between water level and flow, the flow between the sections of water level station 1 and water level station 2, water level station 1 and water level station 3, and water level station 2 and water level station 3 are calculated respectively, where k is the correction coefficient, Q is the flow, and n is the Manning roughness coefficient; Step S52, summing up the flow rates between the sections where the water level measuring stations are located calculated in step S51 and taking the average, to obtain the flow rate data under different water level combination conditions of the three water level measuring stations; performing the same monitoring and calculation on different flow processes, and recording the flow rates and the water level data of the three water level measuring stations; Step S53: Draw relationship curves between the water levels of the three sections and the river flow according to the data obtained in step S52, so as to determine the relationship between the water level and the flow.

7. A method for determining the relationship between water level and flow rate in a river section according to claim 6, characterized in that: The specific method for drawing the relationship curve in step S53 is: Determine the water level value of a water level station one. Given the water level value of a water level station three, draw a flow-water level curve with the water level of water level station two as the horizontal coordinate and the flow as the vertical coordinate. Draw a set of curve clusters for different water levels of water level station three; change the water level of water level station one, and draw another set of curve clusters according to the above steps; for different water levels of water level station one, obtain several sets of curve clusters.

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