Experimental system for monitoring runoff characteristics in farmland plots and method for estimating ridge height

Abstract

The invention discloses an experimental system for monitoring the runoff characteristics of a farmland plot and a method for estimating the height of a field ridge, wherein the experimental system comprises a water accumulation depth collection device, comprising a scale buried in the experimental field for measuring the water accumulation depth and a video monitoring device for collecting the scale of the water accumulation surface at the scale; a field runoff collection device, comprising semicircular pipes connected in sequence on four field ridges of the experimental field, one of the first and last semicircular pipes having a closed starting end and the other having an open end, and a water meter is installed at the starting end of the semicircular pipe near the tail; the four connected semicircular pipes are provided with a slope inclined from the starting end to the end, and the top surfaces of the four semicircular pipes are flush with the field ridge.

Description

Technical Field

[0001] The invention relates to the technical field of hydrological monitoring, and in particular to a test system for monitoring runoff characteristics of a farmland plot and a method for estimating the height of a ridge. Background Art

[0002] Farmland with ridges is the main form of farmland layout in the plains of northern China. Usually, a group of ridges surrounds a field of only 1 to 2 mu. A large number of ridges are distributed in the plains to form countless small reservoirs, which have an important impact on the runoff generation in the plains. However, there has been no clear quantitative expression method for how much water and runoff can be stored in farmland with ridges. One of the reasons is that there is no reasonable experimental system. Due to the existence of ridges, the runoff generation process of farmland extends from infiltration to runoff generation, and then to infiltration, water accumulation, and runoff generation. The water accumulation process is affected by rainfall intensity, rainfall duration, and infiltration rate. Under different rainfall conditions, the amount of water intercepted by farmland ridges is also different. This complex coupling process can only be summarized through experiments and then a simulation method is proposed.

[0003] Most of the current experiments focus on monitoring the soil water movement process, but there is no widespread concern about whether the soil can produce runoff after saturation. The rivers in the northern region are almost dry. In addition to the decline in groundwater levels, the reduction in runoff in farmland areas is an important factor. At present, most hydrological models only adjust soil infiltration parameters when simulating the runoff process in plain areas, and do not consider the water storage function of ridges, resulting in the simulation effect of runoff process in plain areas being much lower than that in mountainous areas.

[0004] At present, there is no relevant research on how high the ridges of farmland should be set to ensure the normal growth of crops and the best runoff production of farmland. Therefore, there is an urgent need for a farmland runoff process monitoring test device to fully monitor the entire farmland runoff process. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the test system for monitoring the runoff characteristics of farmland plots and the method for estimating the ridge height provided by the present invention solve the problem that the prior art cannot realize field runoff monitoring and how to select the ridge for optimal runoff production.

[0006] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0007] In a first aspect, a test system for monitoring runoff characteristics of a farm plot is provided, comprising:

[0008] A water accumulation depth collection device, which includes a scale buried in the test field for measuring the water accumulation depth and a video monitoring device for collecting the scale of the water accumulation surface at the scale;

[0009] A field runoff collection device comprises semicircular pipes connected in sequence on four ridges of an experimental field, wherein the starting end of one of the first and last semicircular pipes is a closed end, and the end of the other is an open end, and a water meter is installed at the starting end of the semicircular pipe near the tail; the four connected semicircular pipes are provided with a slope inclined from the starting end to the end, and the top surfaces of the four semicircular pipes are flush with the ridge.

[0010] In a second aspect, a method for estimating the height of a ridge with optimal runoff generation in a field is provided, comprising:

[0011] The experimental system for monitoring the runoff characteristics of farmland plots was used to obtain the rainfall intensity and soil saturated hydraulic conductivity of each rainfall, and the rate of change of water depth in each farmland was obtained by fitting.

[0012] Based on the rainfall, rainfall time and the rate of change of water depth in farmland obtained by the experimental system for monitoring runoff characteristics in farmland plots, a simulation model of farmland runoff in the scenario with ridges was constructed:

[0013]

[0014] Among them, Q i is the farmland runoff of the ith rainfall; t pi is the time of waterlogging in the ith rainfall; h is the height of the ridge; t 2i is the time of water accumulation in the field ridge during the i-th rainfall; p i is the rainfall of the ith rainfall;

[0015] Based on the simulation model of farmland runoff with field ridges, the total runoff Q generated by all rainfall events during the crop production cycle is calculated:

[0016]

[0017] Where n is the total number of rainfall events during the crop production cycle;

[0018] When the rainfall intercepted by the ridge just meets the needs of crop growth, calculate the possible evapotranspiration of the crop:

[0019]

[0020] Among them, ET is the possible evapotranspiration of crops; P is the total rainfall generated by all rainfalls during the crop production cycle;

[0021] According to the Penman formula and the possible evapotranspiration during the crop growth cycle, the optimal ridge height is calculated:

[0022]

[0023] The beneficial effects of the present invention are as follows: the combination of the video monitoring equipment and the ruler of the present scheme can monitor the time and depth of water accumulation in the field during rainfall; combined with the semicircular pipes arranged on the ridges, the start time of field runoff can be monitored and the runoff during the entire rainfall process can be monitored; through this experimental system, the runoff process of farmland with or without ridges under different rainfall conditions can be completely analyzed or simulated.

[0024] The data collected by the experimental system of this scheme can be used to obtain the total rainfall during the entire crop growth cycle and the water demand of the crop during the entire growth cycle. The possible evapotranspiration can be obtained based on these two data, and combined with the Penman formula, the optimal ridge height can be obtained to ensure that the crops can grow normally while releasing excess rainwater into the river as runoff. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the video surveillance equipment, rulers and some semicircular pipes of the experimental system of this scheme arranged on the ridge.

[0026] Figure 2 This is a schematic diagram of a semicircular pipe installed on the ridge of the experimental field and an intercepting ditch arranged around it.

[0027] Figure 3 This is a schematic diagram of three semicircular pipes and a rain shelter installed on the ridge of the experimental field.

[0028] Figure 4 Flow chart of the method for estimating the height of the ridge that has the best runoff production in the field.

[0029] Figure 5 The runoff of ridges with different ridge heights under the average rainfall conditions from 2012 to 2018; (a) is the runoff with no ridge, (b) is the runoff with a 10 cm ridge, (c) is the runoff with a 12 cm ridge, and (d) is the runoff with a 15 cm ridge.

[0030] Among them, 1. Experimental field; 11. Field ridge; 2. Camera; 3. Semicircular pipe; 31. Water meter; 4. Rain shelter; 5. Intercepting ditch; 6. Ruler. DETAILED DESCRIPTION

[0031] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0032] like Figures 1 to 3 As shown, the experimental system for monitoring the runoff characteristics of farmland plots includes a water accumulation depth collection device and a field runoff collection device, wherein the water accumulation depth collection device includes a scale 6 buried in the experimental field 1 for measuring the water accumulation depth and a video monitoring device for collecting the scale of the water accumulation surface at the scale 6.

[0033] Specifically, the camera 2 of the video monitoring device is aimed at the ruler 6; the ruler 6 is a scale, which is installed on the inner side of the ridge 11 of the experimental field 1. The camera 2 is aimed at the scale scale, and the scale scale scale should be clearly readable. In this solution, the image collected by the video monitoring device can obtain the time of rain occurrence, the starting time of water accumulation in the experimental field 1, and the starting time of runoff in the experimental field 1.

[0034] Experimental Field 1 is usually selected in a farmland experimental station, which should have rainfall monitoring equipment. Experimental Field 1 is selected in an area with flat ground suitable for agricultural cultivation, and it is required not to be disturbed by the external environment during the experiment.

[0035] The field runoff collection device includes semicircular pipes 3 connected in sequence on four ridges 11 of the test field 1, one of the first and last semicircular pipes 3 has a closed end at the start end and the other has an open end at the end, and a water meter 31 is installed at the start end of the semicircular pipe 3 near the tail.

[0036] During implementation, the preferred water meter 31 of this solution adopts an intelligent water meter 31 that can record the initial time and the end time of the water flow. Specifically, it can be a Zhuhua intelligent ultrasonic water meter 31. The water meter 31 can record the time and amount of water flow each time the water flows. The implementation principle of the water meter 31 is:

[0037] The ultrasonic water meter 31 uses the time difference method to measure the flow rate. The time difference method uses the difference between the downstream propagation time td and the upstream propagation time tu of the ultrasonic pulse in the fluid to measure the fluid flow rate, thereby calculating the fluid flow rate in the pipeline.

[0038] The four connected semicircular pipes 3 are provided with a slope from the starting end to the end, and the top surface of the four semicircular pipes 3 is flush with the ridge 11. In order to ensure that the rainwater in the four connected semicircular pipes 3 can flow out smoothly from the water meter 31 to achieve accurate measurement of the flow, the present scheme preferably sets a slope of 2‰ from the starting end to the end of the four connected semicircular pipes 3.

[0039] When the test system provided by this solution is tested, the implementation process is as follows:

[0040] The experimental system is started when rainfall occurs, and the video surveillance equipment collects image information at the scale 6 in real time. When water accumulates in the ridge 11, the water surface intersects with the scale, and the start time, end time and depth of water accumulation can be obtained through the images collected by the video surveillance equipment. When the depth of water accumulation exceeds the height of the ridge 11, precipitation overflows from the ridge 11 of the experimental field 1 into the semicircular pipe 3, flows along the slope direction in the semicircular pipe 3, and finally flows out from the water outlet (the opening of the semicircular pipe 3 at the tail end). The water meter 31 installed at the water outlet can record the initial time and end time of the water flow and the total amount of water passing through.

[0041] In one embodiment of the present invention, the experimental system for monitoring the flow characteristics of farmland plots also includes a rain shelter 4 installed on each ridge 11 to prevent water in non-experimental fields from flowing into the semicircular pipe 3; the rain shelter 4 is inclined toward the outside of the experimental field 1, and its highest side is located in the same plane as the inner surface of the ridge 11.

[0042] The setting of the rain shelter 4 can prevent rainwater in non-experimental fields 1 from entering the semicircular pipe 3, and can also prevent rainwater on the rain shelter 4 from entering the experimental field 1, thereby ensuring accurate measurement of the time of water accumulation and flow generation in the experimental field 1 and the flow generation of the experimental field.

[0043] During implementation, this solution preferably has a ditches 5 outside the ridge 11 to prevent water from non-experimental fields from entering, so as to prevent excessive rainfall intensity from causing water to accumulate outside the experimental field 1 and backflow, so as to ensure that the time of water accumulation, water accumulation depth, and flow rate in the experimental field 1 are accurately collected. It is further preferred that the ditches 5 are located 50 cm outside the ridge 11.

[0044] The top edge of the semicircular pipe 3 near the experimental field 1 is located in the same plane as the inner surface of the ridge 11. Figure 1 Such an arrangement can ensure that when the runoff of the test field 1 is generated, it can enter the semicircular pipe 3 at the first time, preventing rainwater from flowing through the ridge 11 and infiltrating outward, so as to avoid inaccurate runoff measurement.

[0045] The experimental system also includes a plurality of soil moisture sensors, which are buried in the soil of the area enclosed by the experimental field 1 and are used to collect the real-time moisture content of the soil. The collected data is transmitted to the server (computer); the soil moisture sensor can be an RS485 soil moisture sensor.

[0046] The following is an example of runoff monitoring carried out in the experimental field 1 set up in a certain experimental station in Hebei Province to illustrate the experimental data that can be obtained by this experimental system:

[0047] The area of ​​experimental field 1 is 6m 2(2m×3m), install the various components of the farmland runoff monitoring system. On a certain day, a rainfall occurred, and the meteorological station in the experimental station monitored the rainfall information. The initial rainfall time was recorded as t0. The rainfall that entered the experimental field 1 at the beginning first infiltrated. The rainfall continued to occur, and water accumulated in the experimental field 1. At this time, the camera 2 of the water accumulation monitoring system accurately captured the time when water accumulated on the surface of the community, which was recorded as time t1. The rainfall continued, and the depth of water accumulation continued to increase. Camera 2 continued to monitor. When the depth of water accumulation reached the height of the ridge 11 (h'), camera 2 displayed the time as time t2.

[0048] The period from t1 to t2 is the water accumulation stage. Based on the monitoring data, the water accumulation rate and infiltration rate in the experimental field 1 can be calculated, where the water accumulation rate is (j): Unit: mm / min;

[0049] When calculating the infiltration rate, the rainfall intensity is calculated first. The rainfall intensity (r') is obtained by monitoring the rainfall at the meteorological station on the station: P' is the rainfall from t1 to t2 monitored by the meteorological station in the station, unit: mm / min; the infiltration rate is (i'): i'=r'-j, unit: mm / min.

[0050] When rainfall continues, the depth of water accumulation exceeds the ridge 11 and runoff occurs. The runoff enters the semicircular pipe 3 and the water also enters the water meter 31. The water meter 31 records the time when the water enters, which is recorded as t3. When the rainfall ends and the runoff stops, the water meter 31 records the stop time as t4 and records the flow rate Q' of the water at the same time. Q' is the farmland runoff of this rainfall, and the runoff rate (q'). Unit: m 3 / min.

[0051] Through the above monitoring, the characteristic values ​​of the runoff generation process of the farmland during this rainfall can be obtained, including the infiltration rate, water accumulation rate and runoff generation rate, as well as the infiltration time, water accumulation time and runoff generation time. The monitoring can be repeated multiple times by adjusting different ridge heights or facing different rainfall processes.

[0052] like Figure 4 As shown, the present solution also provides a method for estimating the height of a ridge 11 with optimal runoff generation in a field, which includes steps 101 to 105.

[0053] In step 101, the rainfall intensity and soil saturated hydraulic conductivity of each rainfall are obtained by using an experimental system for monitoring the runoff characteristics of farmland plots, and the rate of change of water depth in each farmland is obtained by fitting:

[0054] G i =r i -(α(K(θ)+β)

[0055] Among them, G i is the rate of change of water depth in the i-th farmland; r i is the measured rainfall intensity of the ith field; α and β are fitting parameters; K(θ) is the saturated hydraulic conductivity of the soil;

[0056] In step 102, based on the rainfall and rainfall time and the rate of change of water depth in farmland obtained by the test system for monitoring the runoff characteristics of farmland plots, a simulation model of farmland runoff under the scenario of ridge 11 is constructed:

[0057]

[0058] Among them, Q i is the farmland runoff of the ith rainfall; t pi is the time of water accumulation in the ith rainfall; h is the height of the ridge 11; t 2i is the time of water accumulation in the field ridge during the i-th rainfall; p i is the rainfall of the ith rainfall;

[0059] In step 103, based on the simulation model of farmland runoff in the scenario with field ridge 11, the total runoff Q generated by all rainfalls during the crop production cycle is calculated:

[0060]

[0061] Where n is the total number of rainfall events during the crop production cycle;

[0062] In step 104, when the rainfall intercepted by the ridge 11 just meets the needs of crop growth, the possible evapotranspiration of the crop is calculated:

[0063]

[0064] Among them, ET is the possible evapotranspiration of crops; P is the total rainfall generated by all rainfalls during the crop production cycle;

[0065] In step 105, the optimal height of the ridge 11 is calculated according to the Penman formula and the possible evapotranspiration during the crop growth period:

[0066]

[0067] The Penman formula is used to calculate the possible evapotranspiration during the crop growth cycle, and its specific expression is:

[0068]

[0069] Where Δ is the slope of the saturated water vapor pressure curve; R n is the net radiation of the surface; G is the soil heat flux; γ is the psychrometric constant; T meanis the daily average temperature; u2 is the wind speed at a height of 2 meters; e s is the saturated water vapor pressure; e a is the actual water vapor pressure; K c is the crop coefficient.

[0070] In this scheme, the time of waterlogging in each rainfall can be obtained by the rainfall start time monitored by the meteorological station in the experimental station and the time corresponding to the image of waterlogging collected by camera 2. It can also be calculated by using the field waterlogging occurrence time calculation model constructed according to the Smith-Parlange infiltration model. The calculation model is:

[0071]

[0072] Among them, t p is the time of waterlogging; r is the rainfall intensity; K(θ) is the soil saturated hydraulic conductivity; S is the intermediate parameter; D(θ) is the soil moisture diffusion rate; θ is the real-time soil moisture content; θ0 is the initial soil moisture content; θ s is the saturated hydraulic conductivity of soil.

[0073] Both the real-time soil moisture content and the initial soil moisture content are collected using soil moisture sensors.

[0074] In order to more clearly show the difference in runoff under different ridge heights, the following simulation period is 2012-2018, and the average rainfall during the crop growth period (June-September) is 384 mm. The runoff under the scenarios of no ridge, 10 cm ridge, 12 cm ridge and 15 cm ridge height are analyzed:

[0075] The runoff from farmland under all rainfall conditions from 2012 to 2018 is as follows: Figure 5 As shown, Figure 5 In (a) to (b), the horizontal axis is the precipitation duration, and the vertical axis is the precipitation intensity. The curve is the dividing line between runoff generation and non-runoff generation. Rainfall above the curve will cause runoff (black dots), while rainfall below the curve will not cause runoff because the precipitation intensity is too small or the precipitation duration is too short, and the runoff generation conditions are not met.

[0076] from Figure 5 It can be seen that as the height of the ridge 11 increases, the rainfall that generates runoff becomes less and less, which means that the amount of rainfall remaining in the ridge 11 of the farmland increases. In the absence of the ridge 11, most of the precipitation will form runoff, and it is difficult for the farmland to store water, which cannot meet the needs of crop growth. When the ridge 11 exceeds 15 cm, only a few rainfalls will form runoff. At this time, although the farmland intercepts more rainfall, it will have an adverse impact on the river and ecology outside the farmland.

[0077] From this we can see that the selection of the optimal ridge height will promote the normal growth of plants as well as rivers and ecology.

Claims

1. A method for estimating the height of a ridge with optimal runoff generation in a field, characterized in that: include: The experimental system for monitoring the runoff characteristics of farmland plots was used to obtain the rainfall intensity and soil saturated hydraulic conductivity of each rainfall, and the rate of change of farmland waterlogging depth in each rainfall was obtained by fitting. Based on the rainfall, rainfall time and the rate of change of water depth in farmland obtained by the experimental system for monitoring runoff characteristics in farmland plots, a simulation model of farmland runoff in the scenario with ridges was constructed: in, Q i For the i Farm runoff from rainfall events; t pi For the i The time when water accumulation occurs during rainfall; h is the height of the ridge; t 2i For the i The time of water accumulation in the field ridges after a rainfall; p i For the i The amount of rainfall during a rainfall event; r i For the measured i The intensity of rainfall; G i For the i The rate of change of water depth in farmland; Based on the simulation model of farmland runoff with field ridges, the total runoff generated by all rainfall events during the crop production cycle is calculated. Q : in, n is the total number of rainfall events during the crop production cycle; When the rainfall intercepted by the ridge just meets the needs of crop growth, calculate the possible evapotranspiration of the crop: in, ET is the possible evapotranspiration of the crop; P The total rainfall produced by all rainfall events during the crop production cycle; According to the Penman formula and the possible evapotranspiration during the crop growth cycle, the optimal ridge height is calculated: 。 2. The method for estimating the height of the ridge with the best runoff generation in the field according to claim 1, characterized in that: The Penman formula is: in, is the slope of the saturated water vapor pressure curve; is the net radiation from the surface; is the soil heat flux; is the psychrometric constant; is the daily average temperature; is the wind speed at a height of 2 meters; is the saturated water vapor pressure; is the actual water vapor pressure; is the crop coefficient.

3. The method for estimating the height of the ridge with the best runoff generation in the field according to claim 1, characterized in that: The calculation formula for the rate of change of farmland water depth in each rainfall is fitted as follows: in, α、β are the fitting parameters respectively; is the saturated hydraulic conductivity of soil.

4. The method for estimating the height of a ridge with optimal runoff generation in a field according to claim 1, characterized in that: The occurrence time of waterlogging in each rainfall event is calculated using a field waterlogging occurrence time calculation model constructed based on the Smith-Parlange infiltration model. The calculation model is: ， in, t p The time when the water accumulation occurred; r is the rainfall intensity; is the saturated hydraulic conductivity of soil; S is the intermediate parameter; is the soil moisture diffusion rate; It is the real-time soil moisture content; is the initial soil moisture content; is the saturated hydraulic conductivity of soil.

5. The method for estimating the height of the ridge with the best runoff generation in the field according to claim 1, characterized in that: The test system for monitoring runoff characteristics of farmland plots comprises: A water accumulation depth collection device, which includes a scale buried in the test field for measuring the water accumulation depth and a video monitoring device for collecting the scale of the water accumulation surface at the scale; A field runoff collection device comprises semicircular pipes connected in sequence on four ridges of an experimental field, wherein the starting end of one of the first and last semicircular pipes is a closed end, and the end of the other is an open end, and a water meter is installed at the starting end of the semicircular pipe near the tail; the four connected semicircular pipes are provided with a slope inclined from the starting end to the end, and the top surfaces of the four semicircular pipes are flush with the ridges.

6. The method for estimating the height of the ridge with the best runoff generation in the field according to claim 5, characterized in that: It also includes a rain shelter installed on each ridge to prevent water in non-experimental fields from flowing into the semicircular pipe; the rain shelter is inclined toward the outside of the experimental field, and its highest side is located in the same plane as the inner surface of the ridge.

7. The method for estimating the height of the ridge with the best runoff generation in the field according to claim 5, characterized in that: A ditches is provided outside the field ridge to prevent water from non-experimental fields from entering.

8. The method for estimating the height of the ridge with the best runoff generation in the field according to claim 5, characterized in that: The four connected semicircular pipes are set with a slope of 2‰ from their head end to the end.

9. The method for estimating the height of the ridge with the best runoff generation in the field according to claim 5, characterized in that: The top edge of the semicircular pipe near the experimental field is located in the same plane as the inner surface of the ridge.

10. The method for estimating the height of the ridge with the best runoff generation in the field according to claim 5, characterized in that: It also includes a plurality of soil moisture sensors, which are buried in the soil of the area enclosed by the test field and are used to collect the real-time moisture content of the soil.

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