A water surface evaporation monitoring method with rainfall compensation

Abstract

The present invention discloses a method for monitoring water surface evaporation with rainfall compensation, comprising: obtaining a water level equilibrium lag time between the evaporation dish and the liquid level logging well based on a connection structure between the liquid level logging well and the evaporation dish; regularly collecting water levels in the liquid level logging well; regularly monitoring the presence of rainfall and the corresponding rainfall amount using a rain gauge; correcting a current evaporation calculation cycle using the water level equilibrium lag time to obtain a corrected evaporation calculation cycle, and fitting a water level variation curve over time for the corrected evaporation calculation cycle; determining rainfall type based on a rainfall signal or water level variation curve fed back by the rain gauge; estimating rainfall for different rainfall types based on water level data in the liquid level logging well and rain gauge measurement data; compensating the water level difference in the evaporation calculation cycle using the estimated rainfall amount to calculate evaporation. The present invention can effectively improve the measurement accuracy of water surface evaporation.

Description

Technical Field

[0001] The present invention relates to the technical field of evaporation monitoring, and in particular to a water surface evaporation monitoring method with rainfall compensation. Background Art

[0002] Evaporation refers to the amount of water released into the air from the surface of the water through evaporation over a specific period of time. It is usually expressed in millimeters of the thickness of the evaporated water layer. Evaporation can be measured using an evaporator. Evaporation is crucial in hydrological and meteorological research. For example, in arid regions, if evaporation far exceeds precipitation, severe drought can result. Furthermore, sea surface evaporation has a significant impact on marine climate and ecology.

[0003] Methods for calculating water surface evaporation can be broadly divided into two categories: theoretical and empirical. Theoretical methods, such as the heat balance method, aerodynamic method, and water balance method, are those with a strong physical basis. These methods utilize principles and theories such as heat balance, aerodynamic method, and water balance to determine water surface evaporation. Theoretical methods primarily include the heat balance method, aerodynamic method, comprehensive method, and water balance method. Empirical methods generally use empirical formulas to estimate water surface evaporation based on measured data, without requiring high precision. Another common method is instrumental measurement.

[0004] The instrumental measurement method utilizes an evaporation dish. The entire device consists of a control unit, a liquid level logging unit, a water replenishment overflow unit, and a water replenishment tower. By measuring the water level changes in the liquid level logging unit, the evaporation rate of different water surface areas can be estimated. However, ordinary evaporation dishes can only be used to measure the natural evaporation of water in the absence of rainfall. Once rainfall occurs, the additional rainwater in the liquid level logging unit causes errors in the evaporation calculation results. To address this, researchers added a dedicated rain gauge to the existing evaporation dish to measure rainfall and correct the evaporation rate based on the rainfall recorded by the rain gauge. However, this method still has the following problems: First, based on the tipping bucket measurement principle of the rain gauge, in certain rainfall situations, such as when the rainfall is light, rainwater accumulates slowly in the rain gauge, and a rainfall signal is not generated until a long time later. For rainfall statistics, this rainfall value is negligible, but for evaporation statistics, this rainfall value will cause a large error. Second, during rainfall, raindrops frequently fall into the liquid level logging well, affecting the stability of the water surface in the liquid level logging well. At the same time, the water level changes in the liquid level logging well caused by the additional rainwater cannot be transmitted to the water level gauge in the first place, resulting in errors in the final water level statistical results.

[0005] In addition, most conventional evaporation models currently use data from simple rain gauges (tipping bucket or weighing type) to replace rainfall in evaporation calculations. However, due to certain errors in rain gauges, including errors caused by the inconsistency between the rain-receiving diameters of the rain gauge and the evaporation dish, as well as measurement errors in the rain gauge itself, errors in evaporation calculations may also occur.

[0006] Therefore, due to the limitations of the liquid level logging structure and measuring equipment, once rainfall occurs, uncontrollable errors will occur in the evaporation amount. For the evaporation amount, which is already small in value, these errors are enough to significantly reduce the monitoring accuracy. Summary of the Invention

[0007] The present invention classifies and studies the characteristics of liquid level logging during rainfall, and proposes a water surface evaporation monitoring method with rainfall compensation, which effectively improves the measurement accuracy of water surface evaporation.

[0008] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0009] The present invention discloses a water surface evaporation monitoring method with rainfall compensation, which comprises the following steps:

[0010] S1, design a water level balance test based on the connection structure of the liquid level logging well and the evaporation dish to obtain the water level balance lag time between the evaporation dish and the liquid level logging well;

[0011] S2, regularly collect the water level in the liquid level logging well, and store the collected water level value and the corresponding collection time in the water level database; use a rain gauge to regularly monitor whether rainfall occurs and the corresponding rainfall amount;

[0012] S3, in a new evaporation calculation cycle, using the water level balance lag time to correct the current evaporation calculation cycle to obtain a corrected evaporation calculation cycle, and fitting to obtain a curve of water level change over time in the corrected evaporation calculation cycle;

[0013] S4, judging the rainfall type based on the rainfall signal fed back by the rain gauge or the water level change curve over time, which includes no rainfall, light rainfall, moderate rainfall, and heavy rainfall. Light rainfall means that no rainfall signal is received from the rain gauge, but the water level change curve over time during the evaporation calculation period indicates rainfall. Moderate rainfall means that a rainfall signal is received from the rain gauge and the maximum water level does not exceed the overflow line level. Heavy rainfall means that the maximum water level after rainfall exceeds the overflow line level and the rainfall period is within the evaporation calculation period.

[0014] S5, in the case of no rainfall, the evaporation amount of the current evaporation amount calculation period is calculated by combining the water level change value of the evaporation amount calculation period calculated by combining the water level balance lag time;

[0015] For the case of light rainfall, the evaporation of the current evaporation calculation period is predicted by combining the evaporation type of the study area, the evaporation change curve of the previous N evaporation calculation periods, and the water level change curve of the revised evaporation calculation period over time;

[0016] In the case of moderate rainfall, the rainfall start time is corrected in combination with the water level balance lag time to calculate the rainfall for the current evaporation calculation period; the calculated rainfall is used to correct the water level change value for the evaporation calculation period to calculate the evaporation for the current evaporation calculation period;

[0017] In the case of heavy rainfall, overflow periods are selected based on the water level. For each overflow period, the rainfall output by the rain gauge is used as the rainfall for that overflow period. The rainfall start time is then corrected based on the water level balance lag time, and the rainfall for the non-overflow period is calculated based on the water level value. The total rainfall is used to correct the water level change value of the evaporation calculation period, and the evaporation for the current evaporation calculation period is calculated.

[0018] Furthermore, when receiving the rainfall change signal fed back by the rain gauge, the first rainfall change signal is taken as the rainfall start signal, and the last rainfall change signal is taken as the rainfall end signal; the last rainfall change signal means that there is no new rainfall change signal within a preset time range after the rainfall change signal; the time between the rainfall start signal and the corresponding rainfall end signal is taken as a rainfall period.

[0019] Furthermore, the process of determining the rainfall type based on the rainfall signal fed back by the rain gauge or the water level change curve over time includes the following steps:

[0020] A1: Determine whether a rainfall change signal fed back by a rain gauge is received during the evaporation calculation period. If so, it is determined that there is rainfall. Then, based on whether the real-time water level reaches the overflow level, further determine whether the rainfall type is moderate rainfall or heavy rainfall. The process ends. Otherwise, proceed to step A2.

[0021] A2: Divide the evaporation calculation period into several statistical periods. Based on the historical evaporation data when there was no rainfall, use a single statistical period as the basic time unit to draw a historical evaporation-time curve.

[0022] A3: Analyze the historical evaporation-time curve to obtain the evaporation ratio pattern of different statistical periods within an evaporation calculation cycle or the evaporation range of each statistical period when there is no rainfall;

[0023] A4, fitting the water level variation curve over time for the corrected evaporation calculation period, calculating and plotting the evaporation-time curve for the current evaporation calculation period, and determining whether each statistical period conforms to the evaporation proportion pattern or the corresponding evaporation interval. If so, it is determined that there is no rainfall and the process ends. Otherwise, the non-conforming statistical period is marked as an abnormal period and the process proceeds to step A5.

[0024] A5, with 5 minutes as an analysis cycle, draws a water level change curve during the abnormal period; based on the water level change slope of the adjacent analysis cycles, determine whether rainfall occurs in the current analysis cycle. If rainfall occurs, it is determined that light rainfall occurs in the current evaporation calculation cycle.

[0025] Furthermore, in step A4, for each analysis period, water level values ​​are collected 10 times with a period of 30 seconds, and the average value of the 10 water level values ​​is taken as the water level value of the current analysis period.

[0026] Furthermore, for the case of no rainfall, the evaporation calculation formula is:

[0027] E=h1-h2

[0028] Where h1 represents the average water level at the start of the evaporation calculation period; h2 represents the average water level at the end of the evaporation calculation period.

[0029] Furthermore, for the case of light rainfall, the process of predicting the evaporation amount in the current evaporation amount calculation period includes the following steps:

[0030] B1: Collect historical evaporation change curves for different study areas, analyze the evaporation change curves for each study area when there is no rainfall, manually label the evaporation type according to the evaporation ratio during each period, and construct the first dataset;

[0031] B2, using the first constructed data set to train the convolutional neural network to obtain an evaporation type recognition model;

[0032] B3, import the historical evaporation change curve of the study area into the trained evaporation type recognition model, and output the corresponding evaporation type of the study area;

[0033] B4. Based on the evaporation type of the current study area, the evaporation change curve of the study area with the same evaporation type when there is no rainfall is imported into the LSTM network for training to obtain the evaporation prediction model corresponding to the study area;

[0034] B5, calculate the evaporation of the previous N evaporation calculation cycles based on the water level change curves of the previous N evaporation calculation cycles, import it into the trained evaporation prediction model, and predict the evaporation of the current evaporation calculation cycle.

[0035] Furthermore, for the case of moderate rainfall, the calculation process of the rainfall in the current evaporation calculation period includes the following steps:

[0036] C1, if the rainfall end signal occurs in the current evaporation calculation period, the following formula is used to calculate the rainfall in the current evaporation calculation period:

[0037]

[0038] Where h px1 Indicates the water level value at X hours before the rainfall start signal; h p1max Indicates the highest water level value within 1 hour before the rainfall signal; h px2 Indicates the water level value for X periods of time after the rainfall end signal is generated or the next evaporation calculation cycle ends; proceed to step B4; otherwise, proceed to step B2;

[0039] C2: Determine whether the cumulative duration of the evaporation amount not updated period is greater than a preset duration threshold. If so, proceed to step B3; otherwise, report the evaporation amount of the previous stable period, and increment the evaporation amount not updated period by one.

[0040] C3, calculate the rainfall in the current evaporation calculation period according to the following formula:

[0041] p=h px2 -h p1max ;

[0042] C4, the evaporation rate is calculated using the following formula:

[0043] E=h1-h2+p

[0044] Where h1 represents the average water level at the start of the evaporation calculation period; h2 represents the average water level at the end of the evaporation calculation period.

[0045] Furthermore, in the case of heavy rainfall, the water level in the level logging well is collected in real time with a collection period of 5 minutes;

[0046] For each collection cycle, the water level in the collected level logging well is compared with the preset overflow water level. If the water level in the level logging well exceeds the overflow water level, the collection cycle is marked as an overflow period, and the rainfall output by the rain gauge is used as the rainfall amount for this period;

[0047] For the non-overflow period, the rainfall start time is corrected by combining the water level balance lag time to calculate the rainfall amount during the non-overflow period:

[0048]

[0049] Where hpx3 Indicates the water level value when overflow begins;

[0050] The rainfall amount during the non-overflow period, p1, and the rainfall amount during the overflow period, p2, are combined to obtain the rainfall amount during heavy rainfall, P = p1 + p 2， Correct the evaporation amount to obtain the evaporation amount:

[0051] E=h1-h2+p;

[0052] Where h1 represents the average water level at the start of the evaporation calculation period; h2 represents the average water level at the end of the evaporation calculation period.

[0053] Furthermore, the rainfall type includes continuous rainfall; continuous rainfall means that the maximum water level after rainfall exceeds the overflow line water level, and the rainfall period covers more than one evaporation calculation cycle; the evaporation monitoring process during continuous rainfall includes the following steps:

[0054] D1, determine whether the evaporation calculation cycle duration is less than a preset duration threshold. If so, proceed to step D2;

[0055] D2: Based on the evaporation change curve for the evaporation calculation period at the start of rainfall when no rainfall occurs, select the one with the highest similarity from the evaporation change curves for the same period of the past N days. The evaporation of the selected evaporation change curve for the same day and period is reported as the reference evaporation for each evaporation calculation period during continuous rainfall. The process ends.

[0056] D3, for the evaporation calculation cycle at the beginning of rainfall, the rainfall period is divided into multiple overflow periods, and the rainfall output by the rain gauge is used as the rainfall in the overflow period. For the rainfall in the non-overflow period, the formula is used. Calculate the rainfall; obtain the total rainfall in the evaporation calculation period from the start of rainfall, and draw the evaporation-time change curve when there is no rainfall;

[0057] According to the water level value of the evaporation calculation period at the end of rainfall, the evaporation-time variation curve when there is no rainfall in the evaporation calculation period at the end of rainfall is drawn;

[0058] Combining the evaporation change curves over time in the non-rainfall periods of the two evaporation calculation cycles at the beginning and end of rainfall, as well as the rainfall at the beginning of rainfall, a curve of evaporation change over time in the study area during one evaporation calculation cycle was fitted. The evaporation calculated based on this curve was used as the evaporation for all evaporation calculation cycles during continuous rainfall.

[0059] Furthermore, if the rainfall-free periods in the two evaporation calculation cycles at the beginning and end of rainfall cannot cover the entire evaporation calculation cycle, the one with the highest similarity is selected from the evaporation change curves of the past N days based on the drawn part, and it is used as a reference to fit the evaporation-time change curve of the entire evaporation calculation cycle.

[0060] Compared with the prior art, the present invention has the following beneficial effects:

[0061] First, the water surface evaporation monitoring method with rainfall compensation of the present invention adopts different rainfall compensation schemes according to different rainfall situations, thereby effectively improving the measurement accuracy of water surface evaporation.

[0062] Second, the water surface evaporation monitoring method with rainfall compensation of the present invention designs a water level balance test based on the connection structure of the liquid level logging well and the evaporation dish, obtains the water level balance lag time between the evaporation dish and the liquid level logging well, and uses the water level balance lag time to correct the water level value, thereby reducing the error caused by the evaporation dish structure.

[0063] Third, the water surface evaporation monitoring method with rainfall compensation of the present invention is applicable to 20m 2 , 5m 2 , 1m 2 The method can be used in combination with other evaporating dishes, and does not require any improvement to the existing evaporator structure, has strong universality and is easy to promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 This is a flow chart of the water surface evaporation monitoring method with rainfall compensation of the present invention;

[0065] Figure 2 This is an example graph of evaporation over a 4-hour period in a certain study area;

[0066] Figure 3 This is a schematic diagram of the 1-hour normal water level change results in a certain study area when there is no rainfall;

[0067] Figure 4 This is a schematic diagram of the water level changes in a certain study area during a 1-hour rainfall period. DETAILED DESCRIPTION

[0068] The embodiments of the present invention are described in further detail below with reference to the accompanying drawings.

[0069] See also Figure 1 The present invention discloses a water surface evaporation monitoring method with rainfall compensation, the water surface evaporation monitoring method comprising the following steps:

[0070] S1. Design a water level balance test based on the connection structure of the liquid level logging well and the evaporation dish to obtain the water level balance lag time between the evaporation dish and the liquid level logging well.

[0071] S2, regularly collect the water level in the liquid level logging well, and store the collected water level value and the corresponding collection time in the water level database; use a rain gauge to regularly monitor whether rainfall occurs and the corresponding rainfall amount.

[0072] S3, in the new evaporation calculation cycle, using the water level balance lag time to correct the current evaporation calculation cycle to obtain a corrected evaporation calculation cycle, and fitting to obtain a curve of water level change over time in the corrected evaporation calculation cycle.

[0073] S4. Determine the rainfall type based on the rainfall signal fed back by the rain gauge or the curve of water level change over time. The rainfall types include no rainfall, light rainfall, moderate rainfall, heavy rainfall and continuous rainfall. Light rainfall means that no rainfall signal is received from the rain gauge, but the curve of water level change over time during the evaporation calculation period reflects rainfall. Moderate rainfall means that the rainfall signal is received from the rain gauge and the maximum water level value does not exceed the overflow line water level. Heavy rainfall means that the maximum water level value after rainfall exceeds the overflow line water level and the rainfall period is within the evaporation calculation period. Continuous rainfall means that the maximum water level value after rainfall exceeds the overflow line water level and the rainfall period covers more than one evaporation calculation period.

[0074] S5, in the case of no rainfall, the evaporation amount of the current evaporation amount calculation period is calculated by combining the water level change value of the evaporation amount calculation period calculated by combining the water level balance lag time.

[0075] In the case of light rainfall, the rainfall is estimated by combining the water level change curves of the previous N evaporation calculation cycles and the water level change curve over time of the corrected evaporation calculation cycle. The estimated rainfall is used to correct the water level change value of the evaporation calculation cycle to calculate the evaporation of the current evaporation calculation cycle.

[0076] In the case of moderate rainfall, the rainfall start time is corrected in combination with the water level balance lag time to calculate the rainfall for the current evaporation calculation period; the calculated rainfall is used to correct the water level change value for the evaporation calculation period to calculate the evaporation for the current evaporation calculation period.

[0077] In the case of heavy rainfall, overflow periods are selected based on the water level. For each overflow period, the rainfall output by the rain gauge is used as the rainfall for that overflow period. The rainfall start time is then corrected based on the water level balance lag time, and the rainfall for the non-overflow period is calculated based on the water level value. The total rainfall is used to correct the water level change value of the evaporation calculation period, and the evaporation for the current evaporation calculation period is calculated.

[0078] In the case of continuous rainfall, for each evaporation calculation cycle, the water levels of the current evaporation calculation cycle and the previous evaporation calculation cycle are combined to determine whether to correct the rainfall start time and the rainfall type of the current evaporation calculation cycle, and the evaporation of the current evaporation calculation cycle is calculated based on the judgment results.

[0079] (1) Water level balance lag time

[0080] The evaporator of the present invention also includes the main components such as the control part, the liquid level logging part, the special rain gauge, the water replenishment overflow component, the water replenishment tower, etc. The control part mainly controls the evaporation data collection, calculation, communication and other parts. The IP address, port number, mark line, water replenishment overflow time are set by the mobile phone APP through Bluetooth communication. The APP operation interface can also realize manual water replenishment, overflow control, real-time water level collection, etc. The liquid level logging component includes a high-precision magnetostrictive water level gauge, a float, a magnetic ring, etc., with a resolution of 0.024mm, which can realize the measurement of water level of 0.1mm. The special rain gauge adopts a double-tipping bucket rain gauge to ensure that the rainfall is collected in time. The water replenishment overflow component includes two self-priming pumps. The water replenishment pump connects the evaporating dish to the water replenishment tower. If there is a device and a water pool similar to the water replenishment tower on site, the water replenishment tower can be cancelled, and the volume should be greater than 0.8m 3 The make-up tower should be connected to tap water via a float valve. An overflow pump connects the evaporation dish and overflow tank, discharging the evaporation dish water into the overflow tank. A foundation pit should be dug for the overflow tank, surrounded by brickwork, allowing for natural infiltration. The entire system requires 220V AC power, with both the RTU power supply and control circuitry at 12V. Pump control is achieved via relays. The make-up pump and overflow pump are connected to the evaporation dish via a common pipeline. The other end of the make-up pump is connected to the make-up tank. Check valves are installed at both ends of the make-up pipe to prevent unpressurized backflow. The overflow pump outlet is connected to the filter tank. After sedimentation, the upper clarified portion can be used to replenish the make-up tank.

[0081] Because the evaporation dish and the liquid level logging well are connected by a pipe, the water level in the evaporation dish changes when it rains, but the water level between the evaporation dish and the liquid level logging well will reach equilibrium after a period of time. That is, when it rains, the water level in the evaporation dish rises, but it takes a period of time for the water level in the liquid level logging well to rise to the equilibrium position.

[0082] To verify the relationship between the diameter and length of the connecting pipe and the equilibrium time, this paper designed a water level equilibrium test to obtain the water level equilibrium lag time between the evaporation dish and the liquid level logging well. The reference variables included three parameters: pipe diameter (4 inch, 6 inch), pipe length (1.5m, 4.2m), and the number of bends.

[0083] First, prepare two Φ200-caliber transparent tanks. Manual shutoff valves are installed on either side of the tanks. One end of the shutoff valve connects the two tanks, and the other ends are connected to tap water (for tank replenishment) and a sink (for tank drainage). Tests are performed using different hot-melt pipes and elbows according to test requirements. The test begins by closing the connecting pipes between the two tanks and artificially changing the liquid level difference between the two tanks by adding or draining water. The RTU records the water level difference before and after the two tanks reach equilibrium, as well as the time required.

[0084] The experimental conclusions are as follows: (1) The length of the inter-tank piping is directly proportional to the balancing time; (2) The number of inter-tank piping joints is directly proportional to the balancing time; (3) The inter-tank pipe diameter is inversely proportional to the balancing time; and (4) The tank balancing time and the above parameters have a certain coefficient relationship. Currently, a 1.5m long, four-branch piping design is used between the evaporation dish and the liquid level logging well, with four elbows in the middle. According to tests, the water level balancing time (lag) does not exceed 10 minutes. This invention adopts a 15-minute water level balancing lag time.

[0085] In addition to being able to obtain the water level balance lag time through water level balance tests, it can also be obtained through analysis of the pipe parameters between the evaporation dish and the liquid level logging well. For the latter, the water level balance lag time between the two can be calculated using the following formula:

[0086]

[0087] Where T represents the water level equilibrium lag time; h represents the water level difference between the evaporation dish and the level logging well; s represents the cross-sectional area of ​​the pipeline; λ represents the conversion factor, which is related to the number of on-site pipe joints and the pipe material; l represents the pipeline length; and t represents the basic equilibrium time, which is defined as the equilibrium time required for a 5mm liquid level difference and a 1.5m pipeline length during field measurements. The above formula is based on the design of standard pipeline joints measured in the field and can be corrected using simulated on-site equilibrium times.

[0088] In the new evaporation calculation cycle, the water level equilibrium lag time is used to correct the current evaporation calculation cycle to obtain the corrected evaporation calculation cycle. The water level variation over time for the corrected evaporation calculation cycle is then fitted. Assuming the current evaporation calculation cycle is one day, the corrected evaporation calculation cycle shifts both the start and end times by 15 minutes. For example, the water level measured at 00:15 on the current day is used as the starting water level of the current evaporation calculation cycle, and the water level measured at 00:15 the next day is used as the ending water level of the current evaporation calculation cycle. The difference between the ending and starting water levels is used as the evaporation for that day. This eliminates evaporation errors caused by the water level equilibrium lag time, especially when the water level changes suddenly due to external factors. For example, if we set the start time of the new evaporation calculation cycle after water replenishment and use the water level measured at the liquid level logging 15 minutes after water replenishment as the starting water level of the current evaporation calculation cycle, we can effectively eliminate the impact of the water level rise caused by water replenishment on the evaporation calculation.

[0089] In addition, the water level balance lag time can also be used to correct the water level rise caused by rainfall during rainfall, avoiding large errors in rainfall calculation results due to sudden changes in water levels caused by rainfall.

[0090] (2) Calculation of rainfall during evaporation

[0091] The present invention introduces a new rainfall method, which is to calculate rainfall by water level. The reasons are: 1. The water level measurement and the evaporation dish are in the same water body, so there is no systematic error; 2. The measurement accuracy of the water level is much greater than that of the rain gauge. Specifically, the rainfall start and end time are determined by determining the rain sensor signal, and the rainfall time period is obtained, and then the rainfall is calculated by the water level corresponding to the same period. However, this method is only suitable for short-term rainfall or when the rainfall does not cause overflow. Once a more complex rainfall situation occurs, other adjustments to the rainfall calculation process are required. Based on the above-mentioned calculation of rainfall by water level, the present invention proposes the following rainfall calculation methods for the following rainfall situations.

[0092] (1) Analysis of rainfall types

[0093] The present invention reclassifies rainfall types to address the impact of rainfall on evaporation calculations. It should be noted that the rainfall types of the present invention are specifically classified for evaporation calculations and are not the same as conventional rainfall types.

[0094] Rainfall types include no rainfall, light rainfall, moderate rainfall, heavy rainfall, and continuous rainfall. Light rainfall refers to the absence of rainfall signals from the rain gauge, but the water level over time curve during the evaporation calculation period reflects rainfall; moderate rainfall refers to the presence of rainfall signals from the rain gauge and the maximum water level does not exceed the overflow level; and heavy rainfall refers to the maximum water level after rainfall exceeding the overflow level and the rainfall period is within the evaporation calculation period.

[0095] In the case of light rainfall, it is necessary to determine the rainfall type based on the rainfall signal fed back by the rain gauge or the water level change curve over time.

[0096] According to natural laws, evaporation over a 4-hour period at the same station over a given period will show a certain regularity, and rainfall can cause evaporation during that period to be lower or even zero. Therefore, this regularity can be used to set an evaporation standard curve. The evaporation curve for the current evaporation calculation period can then be compared with the evaporation standard curve to determine whether light rainfall has occurred.

[0097] See also Figure 2 , Figure 2 This is the evaporation curve of a certain study area on January 8, January 9, January 10, and January 11. Figure 2 As can be seen from the data, the maximum 4-hour evaporation rate exhibits a pattern of peak evaporation with a high proportion. For this study area, evaporation is concentrated between 8:00 and 12:00 and between 20:00 and 0:00, accounting for approximately 50% of the total evaporation. Furthermore, over the long term, evaporation at different times has upper and lower limits. This provides a summary of the evaporation rate patterns during periods without rainfall and the rainfall ranges at different times. This is because evaporation within the same study area is still determined by local environmental and geographical parameters, which naturally exhibits regularity.

[0098] In practical applications, when the evaporation calculation cycle is one day and the evaporation is relatively stable, the daily average evaporation over a week or longer period can also be selected to obtain the daily evaporation average value, and then the average value ±0.4mm (this value is inferred based on the historical evaporation characteristics of the site) is used as the possible variation range. If it is lower or higher than this range, it must be marked as doubtful in the results report, and the water level change characteristics must be further analyzed to determine whether micro-rainfall has occurred.

[0099] For each abnormal period, a water level change curve is drawn within the abnormal period, with 5 minutes as an analysis cycle. The slope of the water level change in the adjacent analysis period is used to determine whether there is light rainfall in the current analysis period, and the rainfall period included in the abnormal period is obtained. This is because the water level will gradually decrease with natural evaporation, while rainfall (even light rainfall) will cause the water level to increase. Therefore, when the water level rises or falls sharply, such as when the system itself undergoes normal water replenishment, overflow, manual water change, rainfall and other operations, it is an abnormal situation and needs to be judged based on the water level change curve. Figure 3 The normal evaporation water level change (1 hour normal water level change) shows that for this study area, the specific constraint is that the water level change every 5 minutes does not exceed ±0.1mm (in order to reduce the water level measurement error, the water level can be sampled 10 times within 30 seconds each time, and the average value of the 10 times is used as the basis for water level judgment). When light rainfall occurs, the 5-minute water level will be abnormal, such as Figure 4 As shown. Therefore, for this study area, a sustained rise of more than 0.1 mm in the 5-minute average water level, or multiple periods of no change in the 5-minute water level over a continuous 1-hour period, indicates the occurrence of micro-rainfall, and the specific period of time during which the micro-rainfall occurred can also be located. The 5-minute water level change values ​​vary across different study areas, but in the absence of rainfall, they all exhibit a sustained, slow decline. Water level anomalies that cannot be reflected by the 5-minute water level curve are negligible due to their small values, representing variations within the allowable error range for evaporation monitoring.

[0100] When receiving rainfall change signals from the rain gauge, the first rainfall change signal is considered the rainfall start signal, and the last rainfall change signal is considered the rainfall end signal. The last rainfall change signal refers to the period of time after which no new rainfall change signals occur. The time between the rainfall start signal and the corresponding rainfall end signal is considered a rainfall period. The time of the rainfall end signal and the real-time water level in the liquid level logging well are then used to determine whether overflow or cross-period has occurred, further determining whether the rainfall type is moderate, heavy, or continuous.

[0101] (2) When there is no rainfall

[0102] For the case of no rainfall, the evaporation calculation formula is:

[0103] E=h1-h2

[0104] Where h1 represents the average water level at the start of the evaporation calculation period, and h2 represents the average water level at the end of the evaporation calculation period. The evaporation calculation period here is the start and end time corrected for the water level equilibrium lag time.

[0105] (3) Light rainfall

[0106] For light rainfall, we first analyze the historical evaporation curves for the study area to determine the study area's evaporation type and a set of evaporation curves for periods without rainfall. This step can be accomplished using a convolutional neural network. Specifically, we analyze the evaporation curves for different study areas without rainfall, manually annotating the evaporation types (which can be set based on the evaporation percentage during each time period) to construct a first dataset. This dataset is then used to train the convolutional neural network. The historical evaporation curves for the current study area are then imported into this trained convolutional neural network to output the corresponding evaporation type.

[0107] According to the evaporation type of the current study area, the evaporation change curve of the study area with the same evaporation type in the absence of rainfall is imported into the LSTM network for training. Then, the evaporation of the first N evaporation calculation cycles is calculated based on the water level change curve of the first N evaporation calculation cycles, and it is imported into the trained LSTM network to predict the evaporation of the current evaporation calculation cycle.

[0108] Preferably, the rainfall amount can also be estimated based on the water level change curve over time in the revised evaporation amount calculation period and the predicted evaporation amount in the current evaporation amount calculation period.

[0109] (4) Moderate rainfall

[0110] In the case of moderate rainfall, the rainfall is generally not heavy, overflow does not occur, and the rain gauge will produce rainfall start and end signals. However, due to the large error of the rain gauge itself, the present invention uses the water level difference to estimate the rainfall. Specifically, the rainfall in one evaporation calculation cycle under moderate rainfall conditions can be calculated using the following formula:

[0111]

[0112] Where h px1 Indicates the water level value 15 minutes before the rainfall start signal; h p1max Indicates the highest water level value within 1 hour before the rainfall signal; h px2 Indicates the water level value 15 minutes after the rainfall end signal is generated or the next evaporation calculation cycle ends.

[0113] After obtaining the rainfall, the water level difference is corrected using the following formula to calculate the evaporation:

[0114] E=h1-h2+p

[0115] Where h1 represents the average water level at the start of the evaporation calculation period; h2 represents the average water level at the end of the evaporation calculation period.

[0116] For moderate rainfall, there is a special case where rainfall may continue until the next evaporation calculation cycle. Currently, the minimum interval for updating all data, whether rainfall, water level, or evaporation, is 5 minutes, that is, the theoretical minimum output is 5 minutes. Therefore, when the evaporation calculation cycle is short, it is very likely that the rainfall period will cross regions, and the rainfall will not end or stabilize at the end of the evaporation calculation cycle. In this case, in theory, the water level 15 minutes after the end of the evaporation calculation cycle can be used instead of the water level 15 minutes after the rainfall end signal is generated for calculation. The next evaporation calculation cycle then uses the measured water level at the start time as the actual starting water level. However, when the evaporation calculation cycle is short, the data stability is poor. To this end, the present invention proposes setting different evaporation data reporting methods for evaporation calculation cycles of different lengths to achieve a balance between data stability and timeliness.

[0117] Specifically, a preset time threshold is set. If the time between the end of the current evaporation calculation cycle and the reporting time of the last evaporation update data is less than the preset time threshold, the last evaporation update data will still be reported to ensure the stability of the reported data. Conversely, if the cumulative time of the evaporation unupdated period is greater than the preset time threshold, considering the timeliness of the data, the rainfall in the current evaporation calculation cycle is calculated according to the following formula:

[0118] p=h px2 -h p1max

[0119] The water level difference is corrected using the following formula to calculate the evaporation amount:

[0120] E=h1-h2+p

[0121] Where h1 represents the average water level at the start of the evaporation calculation period; h2 represents the average water level at the end of the evaporation calculation period.

[0122] Of course, it is also possible to make a judgment based on the duration of the evaporation calculation cycle. For example, if the evaporation calculation cycle is one day, then when a rainfall signal appears across days, updated evaporation data will be reported for each evaporation calculation cycle. If the evaporation calculation cycle is several hours, only the evaporation data for the last stable period will be reported, and the time period without update will be accumulated until the accumulated time period without update spans days. Although this sacrifices some data timeliness, it is relatively accurate for daily data.

[0123] (5) Heavy rainfall

[0124] In the case of heavy rainfall, the correction of the starting water level is similar to that of moderate rainfall. The difference is that due to the large amount of rainfall, overflow occurs. Once overflow occurs, it is difficult to use water level changes to calculate the rainfall. At this time, a rain gauge must be used. If the rain gauge is used alone to calculate the rainfall, the aforementioned error problem will exist.

[0125] Therefore, to effectively count overflow water while ensuring accurate rainfall measurement, this paper proposes a segmented rainfall measurement method based on the 5-minute water level. Specifically, in the event of heavy rainfall, the water level in the level logging well is collected in real time with a 5-minute collection cycle. For each collection cycle, the collected water level in the level logging well is compared with the preset overflow level. If the water level in the level logging well exceeds the overflow level, the collection cycle is marked as an overflow period, and the rainfall output by the rain gauge is used as the rainfall during the overflow period.

[0126] For the non-overflow period, since the non-overflow period usually occurs at the beginning of rainfall, the rainfall start time can be corrected by combining the water level balance lag time to calculate the rainfall amount during the non-overflow period:

[0127]

[0128] Where h px3 Indicates the water level value when overflow begins.

[0129] The rainfall amount P1 in the non-overflow period and the rainfall amount P2 in the overflow period are combined to obtain the rainfall amount P=p1+p2 in the case of heavy rainfall. The evaporation amount is corrected to obtain the evaporation amount:

[0130] E=h1-h2+p

[0131] Where h1 represents the average water level at the start of the evaporation calculation period; h2 represents the average water level at the end of the evaporation calculation period.

[0132] (6) Continuous rainfall

[0133] For rainy areas, the present invention also provides a continuous rainfall type. Continuous rainfall refers to the maximum water level after rainfall exceeding the overflow line, and the rainfall period covers more than one evaporation calculation cycle. Continuous rainfall exhibits both overflow and cross-region characteristics. Unlike the cross-region characteristics of moderate rainfall, continuous rainfall exhibits overflow characteristics. Therefore, during the next or the next N evaporation calculation cycles, the water level in the level logging well will remain at the overflow line, making it impossible to measure the water level difference.

[0134] To this end, the present invention sets different evaporation calculation methods for evaporation calculation cycles of different lengths. For a shorter evaporation calculation cycle (such as 4h), based on the evaporation change curve of the evaporation calculation cycle at the beginning of rainfall when there is no rainfall, the one with the highest similarity is selected from the evaporation change curves of the same period in the past N days, and the evaporation of that day is used as the evaporation during continuous rainfall and reported as the reference evaporation. For a longer evaporation calculation cycle (such as one day), first, for the evaporation calculation cycle at the beginning of rainfall, a rainfall calculation method similar to that for heavy rainfall is adopted, that is, multiple overflow periods are divided, and the rainfall output by the rain gauge is used as the rainfall in the overflow period. For the rainfall in the non-overflow period, the formula is used. Perform rainfall calculations; ultimately, calculate the total rainfall for the evaporation calculation period at the start of rainfall, and plot an evaporation-time curve for the period without rainfall. Secondly, due to the water level difference during the evaporation calculation period at the end of rainfall, plot an evaporation-time curve for the period without rainfall at the end of rainfall. Thirdly, combine the evaporation-time curves for the two evaporation calculation periods without rainfall at the start and end of rainfall, as well as the rainfall at the start of rainfall, to fit an evaporation-time curve for the study area during one evaporation calculation period. The evaporation calculated from this curve is used as the evaporation for all evaporation calculation periods during continuous rainfall. If the periods without rainfall at the start and end of rainfall calculation periods do not cover the entire evaporation calculation period, select the evaporation curve with the highest similarity from the past N days based on the plotted portion and use it as a reference to fit the evaporation-time curve for the entire evaporation calculation period.

[0135] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code. The scheme in the embodiment of the present application can be implemented in various computer languages, for example, object-oriented programming language Java and literal translation scripting language JavaScript, etc.

[0136] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0137] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0138] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions for executing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0139] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present application.

[0140] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application is intended to include these modifications and variations.

Claims

1. A method for monitoring water surface evaporation with rainfall compensation, characterized in that: The water surface evaporation monitoring method The following steps are involved: S1, design a water level balance test based on the connection structure of the liquid level logging well and the evaporation dish to obtain the water level balance lag time between the evaporation dish and the liquid level logging well; S2, regularly collect the water level in the liquid level logging well, and store the collected water level value and the corresponding collection time in the water level database; use a rain gauge to regularly monitor whether rainfall occurs and the corresponding rainfall amount; S3, in a new evaporation calculation cycle, using the water level balance lag time to correct the current evaporation calculation cycle to obtain a corrected evaporation calculation cycle, and fitting to obtain a curve of water level change over time in the corrected evaporation calculation cycle; S4, judging the rainfall type based on the rainfall signal fed back by the rain gauge or the water level change curve over time, which includes no rainfall, light rainfall, moderate rainfall, and heavy rainfall. Light rainfall means that no rainfall signal is received from the rain gauge, but the water level change curve over time during the evaporation calculation period indicates rainfall. Moderate rainfall means that a rainfall signal is received from the rain gauge and the maximum water level does not exceed the overflow line level. Heavy rainfall means that the maximum water level after rainfall exceeds the overflow line level and the rainfall period is within the evaporation calculation period. S5, in the case of no rainfall, the evaporation amount of the current evaporation amount calculation period is calculated by combining the water level change value of the evaporation amount calculation period calculated by combining the water level balance lag time; For the case of light rainfall, the evaporation of the current evaporation calculation period is predicted by combining the evaporation type of the study area, the evaporation change curve of the previous N evaporation calculation periods, and the water level change curve of the revised evaporation calculation period over time; In the case of moderate rainfall, the rainfall start time is corrected in combination with the water level balance lag time to calculate the rainfall for the current evaporation calculation period; the calculated rainfall is used to correct the water level change value for the evaporation calculation period to calculate the evaporation for the current evaporation calculation period; In the case of heavy rainfall, overflow periods are selected based on the water level. For each overflow period, the rainfall output by the rain gauge is used as the rainfall for that overflow period. The rainfall start time is then corrected based on the water level balance lag time, and the rainfall for the non-overflow period is calculated based on the water level value. The total rainfall is used to correct the water level change value of the evaporation calculation period, and the evaporation for the current evaporation calculation period is calculated.

2. The method for monitoring water surface evaporation with rainfall compensation according to claim 1, characterized in that: When receiving the rainfall change signal fed back by the rain gauge, the first rainfall change signal is taken as the rainfall start signal, and the last rainfall change signal is taken as the rainfall end signal; the last rainfall change signal means that there is no new rainfall change signal within a preset time range after the rainfall change signal; the time between the rainfall start signal and the corresponding rainfall end signal is taken as a rainfall period.

3. The method for monitoring water surface evaporation with rainfall compensation according to claim 1, characterized in that: The process of determining the rainfall type based on the rainfall signal or water level change curve fed back by the rain gauge includes the following steps: A1: Determine whether a rainfall change signal fed back by a rain gauge is received during the evaporation calculation period. If so, it is determined that there is rainfall. Then, based on whether the real-time water level reaches the overflow level, further determine whether the rainfall type is moderate rainfall or heavy rainfall. The process ends. Otherwise, proceed to step A2. A2: Divide the evaporation calculation period into several statistical periods. Based on the historical evaporation data when there is no rainfall, use a single statistical period as the basic time unit to draw a historical evaporation-time curve. A3. Analyze the historical evaporation-time curve to obtain the evaporation ratio pattern of different statistical periods within an evaporation calculation cycle or the evaporation range of each statistical period when there is no rainfall; A4, fitting the water level variation curve over time for the corrected evaporation calculation period, calculating and plotting the evaporation-time curve for the current evaporation calculation period, and determining whether each statistical period conforms to the evaporation proportion pattern or the corresponding evaporation interval. If so, it is determined that there is no rainfall and the process ends. Otherwise, the non-conforming statistical period is marked as an abnormal period and the process proceeds to step A5. A5, with 5 minutes as an analysis cycle, draws a water level change curve during the abnormal period; based on the water level change slope of the adjacent analysis cycles, determine whether rainfall occurs in the current analysis cycle. If rainfall occurs, it is determined that light rainfall occurs in the current evaporation calculation cycle.

4. The method for monitoring water surface evaporation with rainfall compensation according to claim 2, characterized in that: In step A4, for each analysis period, water level values ​​are collected 10 times with a period of 30 seconds, and the average value of the 10 water level values ​​is taken as the water level value of the current analysis period.

5. The method for monitoring water surface evaporation with rainfall compensation according to claim 1, characterized in that: For the case of no rainfall, the evaporation calculation formula is: E=h1-h2 Where h1 represents the average water level at the start of the evaporation calculation period; h2 represents the average water level at the end of the evaporation calculation period.

6. The method for monitoring water surface evaporation with rainfall compensation according to claim 1, characterized in that: For the case of light rainfall, the process of predicting the evaporation for the current evaporation calculation period includes the following steps: B1: Collect historical evaporation change curves for different study areas, analyze the evaporation change curves for each study area when there is no rainfall, manually label the evaporation type according to the evaporation ratio during each period, and construct the first dataset; B2, using the first constructed data set to train the convolutional neural network to obtain an evaporation type recognition model; B3, import the historical evaporation change curve of the study area into the trained evaporation type recognition model, and output the corresponding evaporation type of the study area; B4. Based on the evaporation type of the current study area, the evaporation change curve of the study area with the same evaporation type when there is no rainfall is imported into the LSTM network for training to obtain the evaporation prediction model corresponding to the study area; B5, calculate the evaporation of the previous N evaporation calculation cycles based on the water level change curves of the previous N evaporation calculation cycles, import it into the trained evaporation prediction model, and predict the evaporation of the current evaporation calculation cycle.

7. The method for monitoring water surface evaporation with rainfall compensation according to claim 1, characterized in that: For moderate rainfall, the calculation process of rainfall for the current evaporation calculation period includes the following steps: C1, if the rainfall end signal occurs in the current evaporation calculation period, the following formula is used to calculate the rainfall in the current evaporation calculation period: Where h px1 Indicates the water level value X hours before the rainfall start signal; h p1max Indicates the highest water level value within 1 hour before the rainfall signal; h px2 Indicates the water level value for X periods of time after the rainfall end signal is generated or the next evaporation calculation cycle ends; proceed to step B4; otherwise, proceed to step B2; C2: Determine whether the cumulative duration of the evaporation amount not updated period is greater than a preset duration threshold. If so, proceed to step B3; otherwise, report the evaporation amount of the previous stable period, and increment the evaporation amount not updated period by one. C3, calculate the rainfall in the current evaporation calculation period according to the following formula: p=h px2 -h p1max ; C4, the evaporation rate is calculated using the following formula: E=h1-h2+p Where h1 represents the average water level at the start of the evaporation calculation period; h2 represents the average water level at the end of the evaporation calculation period.

8. The method for monitoring water surface evaporation with rainfall compensation according to claim 1, characterized in that: In case of heavy rainfall, the water level in the level logging well is collected in real time with a collection period of 5 minutes; For each collection cycle, the water level in the collected level logging well is compared with the preset overflow water level. If the water level in the level logging well exceeds the overflow water level, the collection cycle is marked as an overflow period, and the rainfall output by the rain gauge is used as the rainfall amount for this period; For the non-overflow period, the rainfall start time is corrected by combining the water level balance lag time to calculate the rainfall amount during the non-overflow period: Where h px3 Indicates the water level value when overflow begins; The rainfall amount during the non-overflow period, p1, and the rainfall amount during the overflow period, p2, are combined to obtain the rainfall amount during heavy rainfall, P = p1 + p 2， Correct the evaporation amount to obtain the evaporation amount: E=h1-h2+p; Where h 11 h2 represents the average water level collected at the start time of the evaporation calculation period; h3 represents the average water level collected at the end time of the evaporation calculation period.

9. The method for monitoring water surface evaporation with rainfall compensation according to claim 1, characterized in that: The rainfall type includes continuous rainfall; continuous rainfall means that the maximum water level after rainfall exceeds the overflow line water level, and the rainfall period covers more than one evaporation calculation cycle; the evaporation monitoring process during continuous rainfall includes the following steps: D1, determine whether the evaporation calculation cycle duration is less than a preset duration threshold. If so, proceed to step D2; D2: Based on the evaporation change curve for the evaporation calculation period at the start of rainfall when no rainfall occurs, select the one with the highest similarity from the evaporation change curves for the same period of the past N days. The evaporation of the selected evaporation change curve for the same day and period is reported as the reference evaporation for each evaporation calculation period during continuous rainfall. The process ends. D3, for the evaporation calculation cycle at the beginning of rainfall, the rainfall period is divided into multiple overflow periods, and the rainfall output by the rain gauge is used as the rainfall in the overflow period. For the rainfall in the non-overflow period, the formula is used. Calculate the rainfall; obtain the total rainfall in the evaporation calculation period from the start of rainfall, and draw the evaporation-time change curve when there is no rainfall; According to the water level value of the evaporation calculation period at the end of rainfall, the evaporation-time variation curve when there is no rainfall in the evaporation calculation period at the end of rainfall is drawn; Combining the evaporation change curves over time in the non-rainfall periods of the two evaporation calculation cycles at the beginning and end of rainfall, as well as the rainfall at the beginning of rainfall, a curve of evaporation change over time in the study area during one evaporation calculation cycle was fitted. The evaporation calculated based on this curve was used as the evaporation for all evaporation calculation cycles during continuous rainfall.

10. The method for monitoring water surface evaporation with rainfall compensation according to claim 9, characterized in that: If the rainfall-free periods in the two evaporation calculation cycles at the beginning and end of rainfall cannot cover the entire evaporation calculation cycle, the one with the highest similarity from the evaporation change curves of the past N days is selected based on the drawn part and used as a reference to fit the evaporation-time change curve of the entire evaporation calculation cycle.

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