A water surface evaporation monitoring system with rainfall compensation and low temperature protection

Abstract

The present invention discloses a water surface evaporation monitoring system with rainfall compensation and low temperature protection, comprising a control component, an evaporation dish, a liquid level logging component, a rain gauge, a water replenishment overflow component, a water replenishment tower and an overflow pool; an evaporation calculation unit uses water level data in the liquid level logging and rainfall sent by the rain gauge to estimate rainfall, compensates for the water level difference in the liquid level logging, and calculates evaporation; a low temperature protection unit regularly receives the water temperature in the liquid level logging sent by the magnetic telescopic water level gauge, and when the water temperature in the liquid level logging is lower than a preset temperature threshold, sends a drainage signal to the overflow pump for drainage, so that the water level of the logging body is lower than the preset water level threshold, and keeps the overflow pump in a normally open state until the water temperature is higher than the preset temperature threshold. The present invention can implement low temperature protection for equipment such as pipelines and pumps according to the ambient temperature, and at the same time uses rainfall to compensate for evaporation, effectively improving the measurement accuracy of water surface evaporation.

Description

Technical Field

[0001] The present invention relates to the technical field of evaporation monitoring, and particularly relates to a water surface evaporation monitoring system with rainfall compensation and low-temperature protection. Background Art

[0002] The water surface evaporation amount refers to the amount of water that is dispersed into the air through evaporation from the water surface within a certain period of time, usually expressed in millimeters of the thickness of the evaporated water layer. The measurement of the water surface evaporation amount can be observed through an evaporator. The water surface evaporation amount is very important in hydrological and meteorological research. For example, in arid regions, if the evaporation amount is much greater than the precipitation amount, it will lead to severe drought. In addition, the evaporation amount of the sea surface also has an important impact on the ocean climate and ocean ecology.

[0003] The calculation methods of the water surface evaporation amount can be roughly divided into two categories: one is the theoretical calculation method, and the other is the empirical calculation method. The so-called theoretical calculation method is a method with a strong physical basis, such as the heat balance method, the aerodynamic method, and the water balance method, etc. These calculation methods respectively use principles and theories such as heat balance, aerodynamics, and water balance to determine the water surface evaporation amount. The theoretical calculation methods mainly include the heat balance method, the aerodynamic method, the comprehensive method, and the water balance method. The empirical calculation method is generally a method of estimating the water surface evaporation amount using an empirical formula based on measured data when the accuracy requirements for the measured data are not very high. In addition, there is also a relatively common method, that is, the instrumental measurement method.

[0004] The instrumental measurement method relies on an evaporation pan. The whole set of equipment includes main components such as a control part, a liquid level measuring well part, a water replenishment and overflow component, and a water replenishment tower. By measuring the change in the water level in the liquid level measuring well, the water surface evaporation amounts of different areas are deduced. Ordinary evaporation pans can only be applicable to the natural evaporation of water when there is no rainfall. Once rainfall occurs, due to the additional rainwater in the liquid level measuring well, the calculation result of the evaporation amount will have an error. For this reason, researchers have added a special rain gauge to the existing evaporation pan to measure the rainfall amount, and correct the evaporation amount according to the rainfall amount counted by the rain gauge. However, there are the following two problems with the current method for measuring the water surface evaporation amount using an evaporation pan:

[0005] First, when the evaporation monitoring system is applied in extremely cold regions, the water in the liquid level measuring well may freeze, resulting in inaccurate water level measurement.

[0006] Second, even when a rain gauge is used to measure rainfall, significant measurement errors can still occur due to rainfall. On the one hand, based on the tipping bucket measurement principle of the rain gauge, for certain rainfall situations, such as when the rainfall is small, the rainwater accumulates slowly in the rain gauge and a rainfall signal is generated only after a long period of time. For rainfall statistics, this part of the rainfall value can be ignored, but for evaporation statistics, this part of the rainfall value will cause significant errors. On the other hand, during rainfall, raindrops frequently fall into the liquid level measuring well, affecting the smoothness of the water surface in the liquid level measuring well. At the same time, the water level change in the liquid level measuring well due to the newly added rainwater cannot be transmitted to the water level gauge immediately, resulting in errors in the final water level statistics.

[0007] In addition, most of the current conventional evaporation models use the data of a simple rain sensor (tipping bucket or weighing type) to replace the rainfall in the evaporation calculation. However, due to certain errors in the rain gauge, including the error caused by the inconsistent rain-catching diameters of the rain gauge and the evaporation pan and the measurement error of the rain gauge itself, errors will also occur in the evaporation calculation. Therefore, due to reasons such as the structure of the liquid level measuring well and the limitations of the measuring device, once it rains, uncontrollable errors will occur in the evaporation amount. For the originally small evaporation amount, these errors are sufficient to significantly reduce the monitoring accuracy. Summary of the Invention

[0008] The object of the present invention is to provide a water surface evaporation monitoring system with rainfall compensation and low-temperature protection. On the one hand, it can implement low-temperature protection for equipment such as pipelines and pumps according to the ambient air temperature. On the other hand, by combining the water level to calculate the rainfall amount and using the rainfall amount to compensate for the evaporation amount, the measurement accuracy of the water surface evaporation amount is effectively improved.

[0009] To achieve the above technical object, the technical solution adopted by the present invention is as follows:

[0010] A water surface evaporation monitoring system with rainfall compensation and low-temperature protection, the water surface evaporation monitoring system includes a control component, an evaporation pan, a liquid level measuring well component, a rain gauge, a water replenishment and overflow component, a water replenishment tower, and an overflow pool;

[0011] The liquid level measuring well component includes a liquid level measuring well, a float, and a magnetostrictive water level gauge installed on the float; the magnetostrictive water level gauge measures the water level and water temperature at the position of the float and feeds back the measurement results to the control component;

[0012] The water replenishment and overflow component includes a water replenishment pump and an overflow pump. The water replenishment pump is connected between the evaporation pan and the water replenishment tower, and the water replenishment tower is connected to the water source through a float valve; the overflow pump is connected between the evaporation pan and the overflow pool and is used to drain the water in the evaporation pan into the overflow pool;

[0013] The rain gauge is installed near the evaporation pan and is used to measure the rainfall in the area where the evaporation pan is located, and feed the measurement results back to the control component;

[0014] The control component includes a pump control unit, an evaporation calculation unit, a data reporting unit, and a low-temperature protection unit;

[0015] The pump control unit is connected to the make-up water pump and the overflow pump through a relay, and controls the make-up water pump and the overflow pump according to external control instructions;

[0016] The evaporation calculation unit receives the water level data in the liquid level logging well sent by the magnetostrictive water level gauge and the rainfall sent by the rain gauge. When there is no overflow, it estimates the rainfall using the water level data in the liquid level logging well, compensates the water level difference in the evaporation calculation period with the estimated rainfall, and calculates the evaporation. When there is an overflow, it uses the rainfall sent by the rain gauge as the rainfall during the overflow period, compensates the water level difference in the liquid level logging well, and calculates the evaporation;

[0017] The data reporting unit regularly sends the calculated evaporation to the server platform;

[0018] The low-temperature protection unit regularly receives the water temperature in the liquid level logging well sent by the magnetostrictive water level gauge. When the water temperature in the liquid level logging well is lower than the preset temperature threshold, it sends a drainage signal to the overflow pump for drainage, so that the water level in the logging body is lower than the preset water level threshold, and keeps the overflow pump in the normally open state until the water temperature is higher than the preset temperature threshold.

[0019] Further, the make-up water pump is connected to the evaporation pan through a make-up water pipe, and one-way valves are provided at both ends of the make-up water pipe.

[0020] Further, the outlet of the overflow pump is connected to a filtration tank, and the upper clarified part after sedimentation is transported to the make-up water tank for water make-up.

[0021] Further, the low-temperature protection unit includes an abnormality judgment module;

[0022] When the overflow pump is draining, the abnormality judgment module receives the water level data in the logging body in real time, draws a curve of the water level change over time, and judges whether the water level drop amplitude is greater than the minimum amplitude threshold according to the change curve. If it is less, the overflow pump is continuously turned on for more than 1 minute, and then the overflow pump is automatically powered on again for drainage; if the foregoing power-on operation is repeated three times and there is still no water level change, it notifies the data reporting unit to send an alarm message to the server platform.

[0023] Further, the evaporation calculation unit includes a water level balance lag management module, a rainfall identification module, and an evaporation calculation module;

[0024] The water level balance lag management module is used to manage the water level balance lag time X between the liquid level logging and the evaporation pan;

[0025] The rainfall identification module is used to judge the rainfall type by combining the rainfall signal fed back by the rain gauge or the change curve of the water level over time. The rainfall types include no rainfall, light rainfall, moderate rainfall, and heavy rainfall. Among them, light rainfall means that no rainfall signal is received from the rain gauge, but the change curve of the water level over time in the evaporation calculation period reflects rainfall; moderate rainfall means that a 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;

[0026] The evaporation calculation module calls the evaporation models corresponding to different types according to the rainfall type sent by the rainfall identification module, and calculates the evaporation in the current evaporation calculation period. The evaporation models include no rainfall model, light rainfall model, moderate rainfall model, and heavy rainfall model.

[0027] Further, the process of the rainfall identification module judging the rainfall type by combining the rainfall signal fed back by the rain gauge or the change curve of the water level over time includes the following steps:

[0028] A1. Judge whether a rainfall change signal is received from the rain gauge within the evaporation calculation period. If so, judge that there is rainfall, and then further judge whether the rainfall type is moderate rainfall or heavy rainfall according to whether the real-time water level reaches the overflow water level, and end the process. Otherwise, go to step A2;

[0029] A2. Divide the evaporation calculation period into several statistical time periods, and draw the historical evaporation - time curve with a single statistical time period as the basic time unit according to the historical evaporation data without rainfall;

[0030] A3. Analyze the historical evaporation - time curve to obtain the evaporation proportion rule of different statistical time periods within an evaporation calculation period or the evaporation interval of each statistical time period without rainfall;

[0031] A4. Fit the change curve of the water level over time in the corrected evaporation calculation period, calculate and draw the evaporation - time curve of the current evaporation calculation period, and judge whether each statistical time period conforms to the evaporation proportion rule or the corresponding evaporation interval. If all conform, judge no rainfall and end the process. Otherwise, mark the non - conforming statistical time periods as abnormal time periods and go to step A5;

[0032] A5. With a 5-minute analysis period, draw the water level change curve during the abnormal period; judge whether there is rainfall in the current analysis period according to the water level change slope of adjacent analysis periods. If there is rainfall, it is determined that there is light rainfall in the current evaporation calculation period.

[0033] Further, the evaporation calculation formula of the non-rainfall model is:

[0034] E = h 1 - h 2

[0035] In the formula, h 1 represents the average water level collection at the start time of the evaporation calculation period; h 2 represents the average water level collection at the end time of the evaporation calculation period.

[0036] Further, the process of estimating the evaporation amount in the current evaporation calculation period by the light rainfall model includes the following steps:

[0037] B1. Collect the historical evaporation change curves of different research areas, analyze the evaporation change curves without rainfall in each research area, set the evaporation types manually according to the evaporation proportion in the time period, and construct the first data set;

[0038] B2. Use the constructed first data set to train the convolutional neural network to obtain an evaporation type recognition model;

[0039] B3. Import the historical evaporation change curve of the research area into the trained evaporation type recognition model, and output the corresponding evaporation type of the research area;

[0040] B4. For the evaporation type of the current research area, import the evaporation change curves without rainfall in the research areas with the same evaporation type into the LSTM network for training to obtain an evaporation amount prediction model corresponding to the research area;

[0041] B5. Calculate the evaporation amounts in the previous N evaporation calculation periods according to the water level change curves in the previous N evaporation calculation periods, import them into the trained evaporation amount prediction model, and predict the evaporation amount in the current evaporation calculation period.

[0042] Further, the process of estimating the evaporation amount in the current evaporation calculation period by the moderate rainfall model includes the following steps:

[0043] C1. If the rainfall end signal occurs in the current evaporation calculation period, use the following formula to calculate the rainfall amount in the current evaporation calculation period:

[0044]

[0045] Where h px1 represents the water level value X hours before the rainfall start signal; h p1max represents the maximum value of the water level within 1 hour before the rainfall signal; h px2 represents the water level value X hours after the rainfall end signal is generated or at the end of the next evaporation calculation cycle; go to step B4; otherwise, go to step B2;

[0046] C2. Determine whether the cumulative duration of the evaporation amount update period is greater than the preset duration threshold. If it is greater, go to step B3; otherwise, report the evaporation amount of the previous stable period, and increment the evaporation amount update period by one;

[0047] C3. Calculate the rainfall amount of the current evaporation calculation cycle according to the following formula:

[0048] p = h px2 - h p1max ;

[0049] C4. Calculate the evaporation amount using the following formula:

[0050] E = h 1 - h 2 + p

[0051] Where h 1 represents the average water level acquisition at the start time of the evaporation calculation cycle; h 2 represents the average water level acquisition at the end time of the evaporation calculation cycle.

[0052] Furthermore, the process of estimating the evaporation amount of the current evaporation calculation cycle by the large rainfall model includes the following steps:

[0053] Real-time collect the water level in the liquid level logging well with a 5-minute collection period;

[0054] For each collection period, compare the collected water level in the liquid level logging well with the preset overflow water level. If the water level in the liquid level logging well exceeds the overflow water level, mark this collection period as the overflow period, and use the rainfall amount output by the rain gauge as the rainfall amount of this period;

[0055] For non-overflow periods, correct the rainfall start time in combination with the water level balance lag time, and calculate the rainfall amount of the non-overflow period:

[0056]

[0057] Where h px3 represents the water level value at the start of the overflow;

[0058] Integrate the rainfall amount p 1 of the non-overflow period and the rainfall amount p 2, the rainfall P = p under heavy rainfall conditions is obtained 1 + p 2 , the evaporation is corrected to obtain the evaporation:

[0059] E = h 1 - h 2 + p;

[0060] In the formula, h 1 represents the average water level collection at the start time of the evaporation calculation period; h 2 represents the average water level collection at the end time of the evaporation calculation period.

[0061] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0062] First, the water surface evaporation monitoring system with rainfall compensation and low-temperature protection of the present invention regularly measures the water temperature in the liquid level logging well, performs drainage operations according to the measured water temperature, and tests equipment such as pipelines and pumps to effectively implement low-temperature protection.

[0063] Second, the water surface evaporation monitoring system with rainfall compensation and low-temperature protection of the present invention deeply analyzes the reasons for the measurement error of evaporation caused by rainfall, divides the rainfall types into several categories, combines the water level in the liquid level logging well and the feedback value of the rain gauge to calculate the rainfall, and compensates the evaporation with the rainfall, effectively improving the measurement accuracy of the water surface evaporation.

[0064] Third, the water surface evaporation monitoring system with rainfall compensation and low-temperature protection of the present invention designs a water level balance test according to the connection structure of the liquid level logging well and the evaporation pan, obtains the water level balance lag time between the evaporation pan and the liquid level logging well, and corrects the water level value using the water level balance lag time, reducing the error caused by the evaporation pan structure.

[0065] Fourth, the water surface evaporation monitoring system with rainfall compensation and low-temperature protection of the present invention is applicable to evaporation pans such as 20m 2 , 5m 2 , 1m 2 etc., and has strong universality. Description of the Drawings

[0066] Figure 1 is the flow chart of the water surface evaporation monitoring system with rainfall compensation and low-temperature protection of the present invention;

[0067] Figure 2 is an evaporation example diagram for a 4-hour period in a certain research area;

[0068] Figure 3 is a schematic diagram of the normal water level change result in a 1-hour period without rainfall in a certain research area;

[0069] Figure 4 Schematic diagram of water level change during 1-hour rainfall in a certain research area when there is rainfall. Detailed implementation manners

[0070] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0071] Refer to Figure 1 , the present invention discloses a water surface evaporation monitoring system with rainfall compensation and low-temperature protection. The water surface evaporation monitoring system includes a control component, an evaporation pan, a liquid level logging component, a rain gauge, a water replenishment and overflow component, a water replenishment tower, and an overflow pool;

[0072] The liquid level logging component includes a liquid level logging well, a float, and a magnetostrictive water level gauge installed on the float; the magnetostrictive water level gauge measures the water level and water temperature at the position where the float is located and feeds the measurement results back to the control component;

[0073] The water replenishment and overflow component includes a water replenishment pump and an overflow pump. The water replenishment pump is connected between the evaporation pan and the water replenishment tower, and the water replenishment tower is connected to the water source through a float valve; the overflow pump is connected between the evaporation pan and the overflow pool and is used to drain the water in the evaporation pan into the overflow pool;

[0074] The rain gauge is installed near the evaporation pan and is used to measure the rainfall in the area where the evaporation pan is located and feeds the measurement results back to the control component;

[0075] The control component includes a pump control unit, an evaporation calculation unit, a data reporting unit, and a low-temperature protection unit;

[0076] The pump control unit is connected to the water replenishment pump and the overflow pump through a relay and controls the water replenishment pump and the overflow pump according to external control instructions;

[0077] The evaporation calculation unit receives the water level data in the liquid level logging well sent by the magnetostrictive water level gauge and the rainfall sent by the rain gauge. When there is no overflow, the rainfall is estimated using the water level data in the liquid level logging well, and the estimated rainfall is used to compensate the water level difference in the evaporation calculation period to calculate the evaporation. When there is an overflow, the rainfall sent by the rain gauge is used as the rainfall during the overflow period to compensate the water level difference in the liquid level logging well to calculate the evaporation;

[0078] The data reporting unit regularly sends the calculated evaporation to the server platform;

[0079] The low-temperature protection unit regularly receives the water temperature in the liquid level logging well sent by the magnetostrictive water level gauge. When the water temperature in the liquid level logging well is lower than the preset temperature threshold, it sends a drainage signal to the overflow pump for drainage, so that the water level of the logging well body is lower than the preset water level threshold, and keeps the overflow pump in the normally open state until the water temperature is higher than the preset temperature threshold.

[0080] The control component mainly controls parts such as evaporation data acquisition, calculation, and communication. Through Bluetooth communication, the mobile APP can be used to set the IP address, port number, marking line, and make-up water overflow time. The APP operation interface can also realize the control of manual make-up water and overflow, and the acquisition of real-time water level, 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, and can realize the measurement of the water level with an accuracy of 0.1mm. The rain gauge adopts a double tipping bucket rain gauge to ensure timely rain collection. The make-up water overflow component includes two self-priming pumps: a make-up water pump and an overflow pump. The make-up water pump connects the evaporation dish and the make-up water tower. If there is a device and a water pool similar to the make-up water tower on site, the make-up water tower can be cancelled, and the volume should be greater than 0.8m 3 , and the make-up water tower should be connected to tap water for make-up water through a float valve. The overflow pump connects the evaporation dish and the overflow pool, and drains the water in the evaporation dish into the overflow pool. The overflow pool should be dug with a foundation pit and brickwork around it, and drained by natural infiltration. The whole set of equipment is connected to 220V alternating current. The power supply and control power of the RTU are both 12V, and the two self-priming pumps are controlled through relays. The make-up water pump and the overflow pump are connected to the evaporation dish through a common pipeline. The other end of the make-up water pump is connected to the make-up water tank, and one-way valves are equipped at both ends of the make-up water pipe to avoid backwater without pressure. The outlet of the overflow pump is connected to the filter pool, and the upper clarified part after precipitation can be used for make-up water to the make-up water tank.

[0081] (1) Low-temperature protection

[0082] The magnetostrictive sensor in the liquid level logging well can also measure the water temperature while measuring the water level, and the sampling frequency is 5 minutes.

[0083] Normal situation: (1) When the water temperature collected by the magnetostrictive sensor is lower than the preset temperature at 8 o'clock, the overflow pump is automatically started for drainage operation. During the drainage process, the data collector continuously monitors the water level. If the water level drops normally (the water level changes by more than 0.1mm in 10s), keep the overflow pump continuously running until the water level is lower than 20mm or the water level remains unchanged; keep the overflow pump in the on state and cut off the control power supply of the overflow pump to keep it in the normally open state, so as to avoid damage to the pump body caused by freezing and expansion of the water in the pipeline. After completing the above operations, the drained identifier will be transmitted to the server platform.

[0084] Abnormal situation: (1) When the water temperature collected at 8 o'clock is lower than the preset temperature, the overflow pump is turned on for drainage operation. During the drainage process, the data collector monitors the water level in real time. If the water level drops abnormally or remains unchanged, and the overflow pump continues to operate for more than 1 minute, the controller will automatically power on the overflow pump again. After repeating this three times, if there is still no change in the water level, an alarm message "Drainage failure, please come for maintenance immediately" will be sent to the server platform.

[0085] (2) Evaporation calculation

[0086] The present invention introduces a brand-new rainfall calculation method, that is, calculating rainfall through the water level. The reasons are as follows: 1. The water level measurement and the evaporation pan are in the same water body, without systematic error; 2. The measurement accuracy of the water level is much higher than that of the rain gauge. Specifically, the start time and end time of rainfall are determined by the signal of the rain sensor to obtain the rainfall time period, and then the rainfall is calculated by the corresponding water level in the same time period. However, this method is only applicable to short-term rainfall or when there is no overflow in the rainfall amount. Once a more complex rainfall situation occurs, other adjustments need to be made to the rainfall calculation process. Based on the above-mentioned method of calculating rainfall through the water level, the present invention proposes the following rainfall calculation methods for several rainfall situations.

[0087] (1) Water level balance lag management module

[0088] Since the evaporation pan and the liquid level well are connected by a pipeline, during rainfall, the water level in the evaporation pan changes, but the water level between the evaporation pan and the liquid level well reaches equilibrium after a period of time. That is, during rainfall, the water level in the evaporation pan rises, but the water level in the liquid level well rises to the equilibrium position after a period of time.

[0089] In order to verify the relationship between the size and length of the connecting pipe diameter and the equilibrium time, the present invention designs a water level balance experiment to obtain the water level balance lag time between the evaporation pan and the liquid level well. The reference variables include three parameter variables: pipe diameter (4 points, 6 points), pipeline length (1.5 m, 4.2 m), and the number of elbows.

[0090] First, prepare two transparent tanks with a diameter of Φ200. Manual stop valves are installed on both sides of the tanks. One end of the stop valve connects the two tanks, and the two sides are connected to tap water (for tank water replenishment) and a water tank (for tank drainage) respectively. Different hot melt pipes and elbows are configured for testing according to the test requirements. The test is carried out by first closing the connecting pipe in the two tanks, artificially changing the liquid level difference between the two tanks through water replenishment and drainage, and collecting the water level difference and the required time before and after equilibrium of the two tanks through RTU to complete the test.

[0091] The experimental conclusions are as follows: (1) The length of the pipeline between the tanks is proportional to the equilibrium time; (2) The number of pipeline joints between the tanks is proportional to the equilibrium time; (3) The pipe diameter between the tanks is inversely proportional to the equilibrium time; (4) There is a certain coefficient relationship between the tank equilibrium time and the above parameters.

[0092] The water level equilibrium lag management module is used to manage the water level equilibrium lag time between the evaporation pan and the liquid level well. The water level equilibrium lag time can be obtained through water level equilibrium tests, or can be obtained by analyzing the pipeline parameters between the evaporation pan and the liquid level well. For the latter, the following formula is used to calculate the water level equilibrium lag time between the two:

[0093]

[0094] In the formula, T represents the water level equilibrium lag time; h represents the water level difference between the evaporation pan and the liquid level well; s represents the cross-sectional area of the pipeline; λ represents the conversion coefficient, which is related to the number of on-site pipeline joints and the pipe material; l represents the pipeline length; t represents the basic equilibrium time, which is defined as the equilibrium time required for the limit under a 5mm liquid level difference and a 1.5m pipeline length during on-site measurement. The above formula is deduced based on the design of the standard pipeline joints measured on-site, and can be corrected using the on-site artificially simulated equilibrium time.

[0095] Currently, with a 1.5m long 4 - way pipeline design between the evaporation pan and the liquid level well and 4 elbows in the middle, the water level equilibrium time (lag) does not exceed 10 minutes. Therefore, the present invention takes 15 minutes as the water level equilibrium lag time.

[0096] In the new evaporation calculation period, the water level equilibrium lag time is used to correct the current evaporation calculation period, obtaining the corrected evaporation calculation period, and fitting the curve of the water level change with time for the corrected evaporation calculation period. Assuming the current evaporation calculation period is one day, the start time and end time of the corrected evaporation calculation period are both postponed by 15 minutes. For example, select the measured water level at 0:15 on the current day as the starting water level of the current evaporation calculation period, and select the measured water level at 0:15 the next day as the ending water level of the current evaporation calculation period. Take the difference between the ending water level and the starting water level as the evaporation amount for that day. This can eliminate the evaporation amount error caused by the water level equilibrium lag time, especially when the water level suddenly changes due to some external factors. For example, when we set the start of a new evaporation calculation period after water replenishment, and take the water level of the liquid level well 15 minutes after water replenishment as the starting water level of the current evaporation calculation period, it can effectively eliminate the impact of the water level rise caused by water replenishment on the evaporation amount calculation.

[0097] In addition, during rainfall, the water level balance lag time can also correct the water level rise value caused by rainfall, avoiding large errors in the rainfall calculation results due to sudden water level changes caused by rainfall.

[0098] (2) Rainfall identification module

[0099] The rainfall identification module is used to combine the rainfall signal feedback by the rain gauge or the water level change curve over time to determine the rainfall type. The rainfall types include no rainfall, light rainfall, moderate rainfall, and heavy rainfall. Among them, 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 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.

[0100] In view of the influence of rainfall in the evaporation calculation process, the present invention reclassifies the rainfall types. It should be noted that the rainfall types in the present invention are specifically classified for evaporation calculation and are not the same concept as the conventional rainfall types.

[0101] The rainfall types include no rainfall, light rainfall, moderate rainfall, heavy rainfall, and continuous rainfall. Among them, 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 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.

[0102] For the case of light rainfall, it is necessary to combine the rainfall signal feedback by the rain gauge or the water level change curve over time to determine the rainfall type.

[0103] According to natural laws, the evaporation in a 4-hour period at the same station within a certain time will show certain regularity, and rainfall will cause the evaporation in the period to be smaller or zero. Therefore, this kind of regularity can be used to set the evaporation standard curve, and then compare the evaporation curve in the current evaporation calculation period with the evaporation standard curve to determine whether light rainfall occurs.

[0104] See Figure 2 , Figure 2 is the daily evaporation curve of a certain research area on January 8, January 9, January 10, and January 11. From Figure 2It can be seen that for the maximum evaporation in 4 hours, there are some peaks with relatively high evaporation proportions according to the rule. For this study area, evaporation is concentrated from 8 to 12 o'clock and from 20 to 0 o'clock, accounting for about 50% of the total evaporation. In the long run, there are upper and lower limits for evaporation in different time periods. Thus, the evaporation proportion rule in the non-rainy time periods and the rainfall intervals in different time periods in this study area are summarized. This is because the evaporation in the same study area is still determined by local environmental parameters and geographical parameters, and there will naturally be regularities.

[0105] In practical applications, for the case where the evaporation calculation period is one day and the evaporation is relatively stable, the daily average evaporation within a week or a longer time can also be selected to obtain the daily evaporation average value. Then, taking the average value ± 0.4 mm (this value is inferred based on the historical evaporation characteristics of the site) as the possible variation range, if it is lower or higher than this interval, it needs to be marked as doubtful in the achievement report, and further analyze the water level change characteristics to determine whether there is a light rainfall.

[0106] For each abnormal time period, with 5 minutes as an analysis period, draw the water level change curve within the abnormal time period. According to the water level change slope of adjacent analysis periods, determine whether there is a light rainfall in the current analysis period, and obtain the rainfall time periods included in the abnormal time period. 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 shows a sharp rise or fall, except for normal water replenishment, overflow, artificial water change, rainfall and other operations of the system itself, it belongs to abnormal situations and needs to be judged according to the water level change curve. Figure 3 is the normal water level change of evaporation (the normal water level change in 1 hour). It can be analyzed that for this study area, the specific constraint is that the water level change in every 5 minutes does not exceed ± 0.1 mm (in order to reduce the water level measurement error, the water level can be sampled 10 times within 30S each time, and the average value of 10 times is used as the basis for water level judgment). When there is a light rainfall, the water level in 5 minutes will be abnormal, such as Figure 4 shown. Therefore, for this study area, if the average water level in 5 minutes shows a continuous rise of more than 0.1 mm, or there is no change in the water level in 5 minutes for many times within 1 hour continuously, it indicates that there is a light rainfall, and at the same time, the specific rainfall time period of the light rainfall can be located. For different study areas, the water level change value in 5 minutes is different, but in the case of no rainfall, it will show a continuous and slow decline. And if the water level abnormality that cannot be reflected by the 5-minute water level curve is too small in value, it can be ignored as the variation within the allowable range of evaporation monitoring error.

[0107] 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 the preset time range after this rainfall change signal; the time between the rainfall start signal and the corresponding rainfall end signal is taken as one rainfall period. Then, according to the time when the rainfall end signal occurs and the real-time water level in the liquid level logging well, it is judged whether there is an overflow or a cross-period, and further the rainfall type is judged as moderate rainfall, heavy rainfall or continuous rainfall.

[0108] (3) Evaporation calculation module

[0109] The evaporation calculation module calls the evaporation models corresponding to different types according to the rainfall type sent by the rainfall identification module, and calculates the evaporation amount of the current evaporation calculation period; the evaporation models include no-rainfall model, light-rainfall model, moderate-rainfall model and heavy-rainfall model.

[0110] (3.1) In the case of no rainfall

[0111] For the case of no rainfall, the evaporation calculation formula is:

[0112] E = h 1 -h 2

[0113] In the formula, h 1 represents the average water level acquisition at the start time of the evaporation calculation period; h 2 represents the average water level acquisition at the end time of the evaporation calculation period. The evaporation calculation period here is the start time and end time corrected by the water level balance lag time.

[0114] (3.2) In the case of light rainfall

[0115] For the case of light rainfall, first, for the historical evaporation change curve of the corresponding research area, analyze to obtain the evaporation type of the research area and the set of evaporation change curves without rainfall. This step can be completed by means of a convolutional neural network. Specifically, analyze the evaporation change curves without rainfall in different research areas, manually label the evaporation type (which can be set according to the evaporation proportion in a time period), and construct the first data set; use the constructed first data set to train the convolutional neural network, and then import the historical evaporation change curve of the current research area into the trained convolutional neural network to output the corresponding evaporation type.

[0116] For the evaporation type in the current research area, the evaporation volume change curve without rainfall in the research areas with the same evaporation type is imported into the LSTM network for training. Then, based on the water level change curve in the first N evaporation volume calculation periods, the evaporation volume in the first N evaporation volume calculation periods is calculated and imported into the trained LSTM network to predict the evaporation volume in the current evaporation volume calculation period.

[0117] Preferably, the rainfall can also be estimated according to the water level change curve over time in the corrected evaporation volume calculation period and the predicted evaporation volume in the current evaporation volume calculation period.

[0118] Rainfall condition in (3.3)

[0119] For moderate rainfall, the rainfall amount is generally not very large, and there will be no overflow. Moreover, the rain gauge has a rainfall start signal and a rainfall end signal. However, due to the large error of the rain gauge itself, the present invention uses the water level difference to calculate the rainfall amount. Specifically, the rainfall amount in one evaporation volume calculation period under moderate rainfall conditions can be calculated using the following formula:

[0120]

[0121] In the formula, h px1 represents the water level value 15 minutes before the rainfall start signal; h p1max represents the highest water level value within 1 hour before the rainfall signal; h px2 represents the water level value 15 minutes after the rainfall end signal is generated or at the end of the next evaporation calculation period.

[0122] After obtaining the rainfall amount, the following formula is used to correct the water level difference and calculate the evaporation volume:

[0123] E = h 1 - h 2 + p

[0124] In the formula, h 1 represents the average water level acquisition at the start time of the evaporation volume calculation period; h 2 represents the average water level acquisition at the end time of the evaporation volume calculation period.

[0125] For moderate rainfall, there is a special case where the rainfall may continue into the next evaporation calculation period. Currently, the minimum update interval for all data, regardless of rainfall, water level, or evaporation, is 5 minutes, that is, the minimum theoretical output is 5 minutes. Therefore, when the evaporation calculation period is relatively short, it is very likely that the rainfall period will span different areas, and the rainfall may not have ended or stabilized by the end of the evaporation calculation period. In theory, for this situation, the water level 15 minutes after the end of the evaporation calculation period can be used to replace the water level value 15 minutes after the rainfall end signal is generated for calculation. For the next evaporation calculation period, the measured water level at the start time is used as the actual starting water level. However, when the duration of the evaporation calculation period is short, the data stability is poor. Therefore, the present invention proposes to set different evaporation data reporting methods for evaporation calculation periods of different durations to achieve a balance between data stability and timeliness.

[0126] Specifically, a preset duration threshold is set. If the duration between the end time of the current evaporation calculation period and the reporting time of the previous evaporation update data is less than the preset duration threshold, the previous evaporation update data is still reported this time to ensure the stability of the reported data. Conversely, if the cumulative duration of the evaporation non-update period is greater than the preset duration threshold, considering the timeliness of the data, the rainfall amount for the current evaporation calculation period is calculated according to the following formula:

[0127] p = h px2 - h p1max

[0128] And the water level difference is corrected using the following formula to calculate the evaporation amount:

[0129] E = h 1 - h 2 + p

[0130] In the formula, h 1 represents the average water level acquisition at the start time of the evaporation calculation period; h 2 represents the average water level acquisition at the end time of the evaporation calculation period.

[0131] Of course, it can also be judged according to the duration of the evaporation calculation period. For example, when the evaporation calculation period is one day, when the rainfall signal appears across days, the updated evaporation data is reported for each evaporation calculation period. If the evaporation calculation period is several hours, only the evaporation data of the previous stable period is reported, and the non-update duration is accumulated until the accumulated non-update duration spans days. Although this sacrifices some data timeliness, the accuracy for daily data is relatively high.

[0132] (3.4) Situation of heavy rainfall

[0133] In the case of heavy rainfall, the correction of the initial water level is similar to that in moderate rainfall. The difference is that due to the large rainfall, overflow occurs. Once overflow occurs, it is difficult to infer the rainfall amount from the water level change. At this time, a rain gauge must be used; if the rain gauge is blindly used to count the rainfall amount, there will be the aforementioned error problem.

[0134] Therefore, in order to effectively count the overflow water volume and take into account the rainfall measurement accuracy at the same time, the present invention proposes a segmented rainfall measurement method based on the 5-minute water level. Specifically, for the case of heavy rainfall, the water level in the liquid level measuring well is collected in real time with a 5-minute collection period. For each collection period, the collected water level in the liquid level measuring well is compared with the preset overflow water level. If the water level in the liquid level measuring well exceeds the overflow water level, the collection period is marked as the overflow period, and the rainfall amount output by the rain gauge is used as the rainfall amount in this overflow period.

[0135] For non-overflow periods, since non-overflow periods usually occur at the beginning of rainfall, the starting time of rainfall can be corrected by combining the water level balance lag time, and the rainfall amount in the non-overflow period is calculated as follows:

[0136]

[0137] In the formula, h px3 represents the water level value at the start of overflow.

[0138] Combining the rainfall amount p 1 in the non-overflow period and the rainfall amount p 2 in the overflow period, the rainfall amount P = p 1 + p 2 is obtained. After correcting the evaporation amount, the evaporation amount is obtained:

[0139] E = h 1 - h 2 + p

[0140] In the formula, h 1 represents the average water level collection at the start time of the evaporation amount calculation period; h 2 represents the average water level collection at the end time of the evaporation amount calculation period.

[0141] (3.5) Case of continuous rainfall

[0142] For rainy regions, the present invention also sets a continuous rainfall type. 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. Continuous rainfall has both overflow characteristics and cross-region characteristics. Different from cross-region during moderate rainfall, due to the overflow characteristics of continuous rainfall, in the next or the next N evaporation calculation periods, the water level value in the liquid level logging well will remain at the overflow water level line, and the water level difference cannot be measured.

[0143] Therefore, the present invention sets different evaporation calculation methods for evaporation calculation periods of different durations. For a relatively short evaporation calculation period (such as 4h), according to the evaporation change curve of the evaporation calculation period at the start of rainfall when there is no rainfall, select the one with the highest similarity from the evaporation change curves of the same time period in the past N days, and report the evaporation amount on that day as the evaporation amount during continuous rainfall as the reference evaporation amount. For a relatively long evaporation calculation period (such as one day), first, for the evaporation calculation period at the start of rainfall, adopt a rainfall calculation method similar to that of heavy rainfall, that is, divide into multiple overflow periods, and take the rainfall output by the rain gauge as the rainfall amount in the overflow periods. For the rainfall amount in non-overflow periods, use the formula for rainfall calculation; finally, statistically obtain the total rainfall amount of the evaporation calculation period at the start of rainfall, and draw the evaporation-time change curve when there is no rainfall. Secondly, since there is a water level difference in the evaporation calculation period at the end of rainfall, draw the evaporation-time change curve when there is no rainfall in the evaporation calculation period at the end of rainfall. Thirdly, combine the evaporation-time change curves of the non-rainfall periods in the two evaporation calculation periods at the start and end of rainfall, and the rainfall amount in the initial stage of rainfall, and fit to obtain the evaporation-time change curve of the study area in one evaporation calculation period. Take the evaporation amount calculated according to this curve as the evaporation amount of all evaporation calculation periods during continuous rainfall. If the non-rainfall periods in the two evaporation calculation periods at the start and end of rainfall cannot cover the entire evaporation calculation period, then you can select the one with the highest similarity from the evaporation change curves of the past N days based on the part that has been drawn, and use it as a reference to fit the evaporation-time change curve of the entire evaporation calculation period.

[0144] Those skilled in the art should understand that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memory, CD-ROM, optical memory, etc.) that contain computer-usable program code. The solutions in the embodiments of the present application can be implemented in various computer languages. For example, object-oriented programming languages such as Java and interpreted scripting languages such as JavaScript, etc.

[0145] The present application is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions run by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0146] These computer program instructions can 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, such that the instructions stored in the computer-readable memory generate a manufactured article including instruction means, and the instruction means implement the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0147] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are run on the computer or other programmable device to generate a computer-implemented process, so that the instructions running on the computer or other programmable device provide steps for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0148] Although the preferred embodiments of the present application have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0149] Obviously, those skilled in the art can 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 equivalent technologies, this application is also intended to cover these modifications and variations.

Claims

1. A water surface evaporation monitoring system with rainfall compensation and low temperature protection, characterized in that: The water surface evaporation monitoring system includes a control component, an evaporation dish, a liquid level logging component, a rain gauge, a water replenishment overflow component, a water replenishment tower and an overflow tank; The liquid level logging component includes a liquid level logging component, a float, and a magnetostrictive water level gauge installed on the float; the magnetostrictive water level gauge measures the water level and water temperature at the location of the float, and feeds back the measurement results to the control component; The water replenishment overflow assembly includes a water replenishment pump and an overflow pump. The water replenishment pump is connected between the evaporation dish and the water replenishment tower. The water replenishment tower is connected to the water source through a float valve. The overflow pump is connected between the evaporation dish and the overflow tank to discharge the water in the evaporation dish into the overflow tank. The rain gauge is installed near the evaporation dish and is used to measure the rainfall in the area where the evaporation dish is located, and feed the measurement result back to the control component; The control assembly includes a pump control unit, an evaporation amount calculation unit, a data reporting unit and a low temperature protection unit; The pump control unit is connected to the water supply pump and the overflow pump through a relay, and controls the water supply pump and the overflow pump according to an external control instruction; The evaporation calculation unit receives the water level data in the liquid level logging well sent by the magnetostrictive water level gauge and the rainfall sent by the rain gauge, and when no overflow occurs, uses the water level data in the liquid level logging well to estimate the rainfall, and uses the estimated rainfall to compensate the water level difference in the evaporation calculation period to calculate the evaporation; when overflow occurs, uses the rainfall sent by the rain gauge as the rainfall in the overflow period, compensates the water level difference in the liquid level logging well, and calculates the evaporation; The data reporting unit periodically sends the calculated evaporation amount to the server platform; The low-temperature protection unit periodically receives the water temperature in the liquid level logging well sent by the magnetostrictive water level gauge. When the water temperature in the liquid level logging well is lower than a preset temperature threshold, a drainage signal is sent to the overflow pump for drainage, so that the water level of the logging body is lower than the preset water level threshold, and the overflow pump is kept in a normally open state until the water temperature is higher than the preset temperature threshold.

2. The water surface evaporation monitoring system with rainfall compensation and low temperature protection according to claim 1 is characterized in that: The water supply pump is connected to the evaporating dish through a water supply pipe, and both ends of the water supply pipe are equipped with one-way valves.

3. The water surface evaporation monitoring system with rainfall compensation and low temperature protection according to claim 1 is characterized in that: The outlet of the overflow pump is connected to the filter tank, and the upper clarified part after sedimentation is transported to the water replenishment tank for water replenishment.

4. The water surface evaporation monitoring system with rainfall compensation and low temperature protection according to claim 1 is characterized in that: The low temperature protection unit includes an abnormality judgment module; When the overflow pump is draining water, the abnormal judgment module receives the water level data in the logging body in real time, draws a curve of the water level change over time, and judges whether the water level drop is greater than the minimum amplitude threshold based on the change curve. If it is less, the overflow pump is continuously turned on for more than 1 minute, and then the overflow pump is automatically powered on again to drain water; if the above power-on operation is repeated three times and there is still no water level change, the data reporting unit is notified to send an alarm message to the server platform.

5. The water surface evaporation monitoring system with rainfall compensation and low temperature protection according to claim 1 is characterized in that: The evaporation calculation unit includes a water level balance hysteresis management module, a rainfall identification module and an evaporation calculation module; The water level balance lag management module is used to manage the water level balance lag time X between the liquid level logging and the evaporation dish; The rainfall identification module is used to judge the rainfall type in combination with the rainfall signal fed back by the rain gauge or the water level change curve over time, and the rainfall types include no rainfall, light rainfall, moderate rainfall and heavy rainfall; wherein, light rainfall means that no rainfall signal fed back by the rain gauge is received, but the water level change curve over time in the evaporation calculation period reflects rainfall; moderate rainfall means that the rainfall signal fed back by the rain gauge is received 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; The evaporation calculation module retrieves evaporation models corresponding to different rainfall types sent by the rainfall recognition module to calculate the evaporation of the current evaporation calculation cycle; the evaporation models include no rainfall model, light rainfall model, medium rainfall model and heavy rainfall model.

6. The water surface evaporation monitoring system with rainfall compensation and low temperature protection according to claim 5 is characterized in that: The rainfall identification module combines the rainfall signal fed back by the rain gauge or the water level change curve over time to determine the rainfall type, and the process includes the following steps: A1, determine whether the rainfall change signal fed back by the rain gauge is received during the evaporation calculation period. If yes, it is determined that there is rainfall, and then further determine whether the rainfall type is medium rainfall or heavy rainfall according to whether the real-time water level reaches the overflow water level, and end the process. Otherwise, go to step A2; A2, divide the evaporation calculation period into several statistical periods, and draw the historical evaporation-time curve based on the historical evaporation data when there is no rainfall, taking a single statistical period as the basic time unit; A3, analyze the historical evaporation-time curve to obtain the evaporation proportion law of different statistical periods within an evaporation calculation cycle or the evaporation range of each statistical period when there is no rainfall; A4, fitting to obtain the water level variation curve over time of the modified evaporation calculation period, calculating and drawing the evaporation-time curve of the current evaporation calculation period, judging whether each statistical period conforms to the evaporation proportion law or the corresponding evaporation interval, if all conform, judging that there is no rainfall, and ending the process, otherwise, marking the non-conforming statistical period as an abnormal period, and proceeding to step A5; A5, with 5 minutes as an analysis cycle, draws the water level change curve during the abnormal period; judges whether rainfall occurs in the current analysis cycle based on the water level change slope of the adjacent analysis cycle. If rainfall occurs, it is determined that light rainfall occurs in the current evaporation calculation cycle.

7. The water surface evaporation monitoring system with rainfall compensation and low temperature protection according to claim 5 is characterized in that: The evaporation calculation formula of the no-rainfall model is: E=h1-h2 Wherein, h1 represents the average water level collected at the start time of the evaporation calculation period; h2 represents the average water level collected at the end time of the evaporation calculation period.

8. The water surface evaporation monitoring system with rainfall compensation and low temperature protection according to claim 5 is characterized in that: The process of estimating the evaporation of the current evaporation calculation period using the micro-rainfall model comprises the following steps: B1, collect the historical evaporation change curves of different study areas, analyze the evaporation change curves of each study area when there is no rainfall, manually mark the evaporation type according to the evaporation ratio of the time period, and construct the first data set; 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, according to the evaporation type of the current study area, the evaporation change curve of the study area with the same evaporation type without rainfall is imported into the LSTM network for training to obtain the evaporation prediction model corresponding to the study area; B5, the evaporation of the first N evaporation calculation cycles is calculated according to the water level change curve of the first N evaporation calculation cycles, and the evaporation is imported into the trained evaporation prediction model to predict the evaporation of the current evaporation calculation cycle.

9. The water surface evaporation monitoring system with rainfall compensation and low temperature protection according to claim 5 is characterized in that: The process of estimating the evaporation of the current evaporation calculation period using the medium rainfall model comprises the following steps: C1, if the rainfall end signal occurs in the current evaporation calculation cycle, the rainfall in the current evaporation calculation cycle is calculated using the following formula: In the formula, 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 at X hours after the rainfall end signal is generated or the next evaporation calculation cycle ends; go to step B4; otherwise, go to step B2; C2, determine whether the accumulated duration of the evaporation amount not updated period is greater than the preset duration threshold, if so, proceed to step B3, otherwise, report the evaporation amount of the last stable period, and the evaporation amount not updated period is increased 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 is calculated using the following formula: E=h1-h2+p Wherein, h1 represents the average water level collected at the start time of the evaporation calculation period; h2 represents the average water level collected at the end time of the evaporation calculation period.

10. The water surface evaporation monitoring system with rainfall compensation and low temperature protection according to claim 5, characterized in that: The process of estimating the evaporation of the current evaporation calculation period using the heavy rainfall model comprises the following steps: The water level in the level logging well is collected in real time with a collection cycle of 5 minutes; For each collection period, 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 period is marked as the overflow period, and the rainfall output by the rain gauge is used as the rainfall in this period; For the non-overflow period, the rainfall start time is corrected by combining the water level balance lag time, and the rainfall in the non-overflow period is calculated: In the formula, h px3 Indicates the water level value when overflow begins; Combining the rainfall p1 in the non-overflow period and the rainfall p2 in the overflow period, we get the rainfall P=p1+p2 in the case of heavy rainfall. We correct the evaporation to get the evaporation: E = h1 - h2 + p; Wherein, h1 represents the average water level collected at the start time of the evaporation calculation period; h2 represents the average water level collected at the end time of the evaporation calculation period.

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