Field water management equipment and field water management system

Abstract

To provide a field water management device that can adjust a water level in a field to a target water level while suppressing variations even if there is a difference between the water level at the installation location of a water level sensor and the water levels at other locations in the field.SOLUTION: A field water management device comprises: a water supply mechanism that supplies irrigation water to a field; a water level sensor installed near the water supply mechanism; and a water supply control unit that controls the water supply by the water supply mechanism based on the water level detected by the water level sensor so that the water level in the field becomes a target water level. The water supply control unit is configured to stop the water supply by the water supply mechanism when a preset delay time has elapsed after the water level detected by the water level sensor reaches the target water level from the start of the water supply by the water supply mechanism.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a field water management device and a field water management system. [Background technology]

[0002] In recent years, the use of ICT for water management in fields has been attracting attention. Patent Document 1 discloses a field water supply and drainage system that enables remote operation or automation of field water management at low cost, and provides a system for remotely or automatically controlling field water management. The field water supply and drainage system includes a first electric actuator attached to a water supply device via a first adapter to operate valves and the like provided in the water supply device, and a second electric actuator attached to a drainage device via a second adapter to operate partitions and the like provided in the drainage device. The first and second electric actuators are electric actuators of the same structure.

[0003] Patent Document 2 discloses a field groundwater management system for managing the water depth of groundwater in a field, comprising: a water supply control device that performs a water supply operation to supply water to the field from the surface; and a water depth sensor that senses the water depth of the groundwater and transmits water depth sensing information indicating the sensing result to the water supply control device, wherein the water depth sensing information indicates whether the water depth is below a predetermined management water level, and the water supply control device, based on the water depth sensing information, senses that the water depth is below the management water level, waits for a predetermined waiting period to elapse before performing the water supply operation, and starts the water supply operation after the waiting period has elapsed.

[0004] Non-patent document 1 proposes an underground irrigation system comprising: a drainage pipe laid underground in a field; auxiliary drains arranged at predetermined intervals perpendicular to the drainage pipe in a plan view; a water supply mechanism communicating with the base end of the drainage pipe and supplying irrigation water to the field via the drainage pipe and the auxiliary drains; a water level sensor installed on a water level control device constituting the water supply mechanism; and a valve that automatically stops the water supply by the water supply mechanism based on the water level detected by the water level sensor. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2017-192366 [Patent Document 2] Japanese Patent Publication No. 2021-65170 [Non-patent literature]

[0006] [Non-Patent Document 1] "Manual for the Utilization of Groundwater Level Control Systems in Paddy Field Crop Rotation," edited and published by the National Agriculture and Food Research Organization, January 2014, pp. 1-2. [Overview of the project] [Problems that the invention aims to solve]

[0007] In the technology described in Patent Document 1, after supplying irrigation water to the field by a water supply device, the water supply device was configured to immediately stop supplying water when a water level sensor installed in the field detected that the water level in the field had reached the target level.

[0008] However, in response to the declining farming population, shifting from standard 30-are dispersed paddy fields to larger paddy fields of 1 hectare or more to reduce the workload of large-scale farmers presented a problem: it took time for the irrigation water supplied from the water supply system to reach the target water level throughout the entire field. If water supply was controlled based on the water level detected by water level sensors installed near the water supply system, it was impossible to control the water level in the field to the target level. Furthermore, installing water level sensors in multiple locations in the field resulted in increased equipment costs.

[0009] In the underground irrigation system described in Non-Patent Document 1, the water level sensor installed in the water level control device connected to the base end of the drainage pipe detected that a predetermined target water level had been reached, and the water supply valve installed in the water level control device was immediately closed. Therefore, there was no guarantee that the groundwater level would reach the target water level throughout the entire field, and there was a risk that the groundwater level in the field would fall below the target water level.

[0010] The field groundwater management system described in Patent Document 2 is configured to start water supply operations only after a predetermined waiting period has elapsed, without immediately supplying water when the water depth detected by the water depth sensor falls below the management water level. This aims to avoid unnecessary water supply due to rainfall occurring during the waiting period, and therefore does not solve the above-mentioned problem.

[0011] In view of the above-mentioned prior art, the object of the present invention is to provide a field water management device and a field water management system that can adjust the field water level to a target water level while suppressing variations, even when there is a difference between the water level at the installation location of the water level sensor and the water level at other locations in the field. [Means for solving the problem]

[0012] To achieve the above objective, the first characteristic configuration of the field water management device according to the present invention is a field water management device comprising: a water supply mechanism for supplying irrigation water to a field; a water level sensor installed near the water supply mechanism; and a water supply control unit that controls the water supply by the water supply mechanism based on the water level detected by the water level sensor so that the water level in the field reaches a target water level. The field comprises an underground irrigation system comprising a drainage pipe positioned at the bottom of a guide channel formed underground along one side of the levee, and auxiliary drainage channels positioned above the guide channel at predetermined intervals so as to intersect with the drainage pipe in a plan view, the water supply mechanism connected to the base end of the drainage pipe, and the water level sensor positioned near the base end of the drainage pipe, and the water supply control unit is configured to stop water supply by the water supply mechanism after a delay time has elapsed, which is set based on the time required to eliminate any bias in the detected water level caused by the installation position of the water level sensor, after the groundwater level detected by the water level sensor has reached the target water level, and the delay time is the time required for water to move into the soil between each auxiliary drainage channel, and is a value set based on the time calculated by the water supply control unit based on the permeability coefficient of the soil. It's at a single point.

[0013] After the water supply mechanism starts supplying water, and after the water level detected by the water level sensor reaches the target water level, the water supply mechanism stops supplying water when a predetermined delay time has elapsed. This allows an amount of irrigation water equivalent to the delay time to be used to correct the imbalance between the water level near the water supply mechanism and the water level at a location further away from the water supply mechanism.

[0014] By setting the delay time to the time required to correct the difference between the water level at the water level sensor's installation location and the water level at a location further away from the sensor, it is possible to adjust the water level to an appropriate level while avoiding unnecessary water supply.

[0015] Irrigation water supplied from the water supply mechanism to the underground drainage pipe seeps into the soil near the pipe as it flows through it, and eventually flows into auxiliary drainage channels arranged at predetermined intervals. The irrigation water flowing inside each auxiliary drainage channel seeps into the soil between adjacent channels from the sides of the channel. Since there is no significant difference between the time it takes for the water level detected by a water level sensor installed near the base end of the underground drainage pipe to reach the target water level and the time it takes for the irrigation water to move from the underground drainage pipe to the auxiliary drainage channels, the time required for water to seep from the auxiliary drainage channels into the surrounding soil can be used as a delay time to suppress variations in groundwater levels across the field area.

[0016] And since the auxiliary underdrains are arranged at a predetermined installation interval so as to intersect the underdrain pipe in plan view, the time required for water to move from both auxiliary underdrains to the soil between adjacent auxiliary underdrains can be calculated based on the permeability coefficient of the soil. Note that the permeability coefficient refers to a coefficient representing the degree of ease with which water passes through the soil. Assuming the cross-sectional area of the layer of soil or sand constituting the soil is A, the length is l, the gradient of water flow (dynamic water gradient) is h, and the flow rate is Q, the permeability coefficient k is defined as Q = kA·h / l (the unit is length / time). Generally, the smaller the particle size of the soil, the smaller the permeability coefficient k, and the larger the particle size, the larger the permeability coefficient k. If the permeability coefficient k is measured in advance according to each field, the time required for water to move a predetermined distance from the auxiliary underdrain can be obtained.

[0017] The second characteristic configuration is a field water management device comprising: a water supply mechanism for supplying irrigation water to a field; a water level sensor installed near the water supply mechanism; and a water supply control unit that controls the water supply by the water supply mechanism based on the water level detected by the water level sensor so that the water level in the field reaches a target water level. The field includes an underdrain pipe disposed at the bottom of a guide groove formed underground along one side of a ridge, and an auxiliary underdrain disposed at a predetermined installation interval above the guide groove so as to intersect the underdrain pipe in plan view. The water supply mechanism is connected to the proximal end side of the underdrain pipe, and the underground irrigation equipment includes a water level sensor disposed near the proximal end side of the underdrain pipe. The water supply control unit starts water supply by the water supply mechanism, and after the underground water level detected by the water level sensor reaches the target water level, The time required to correct the bias in the detected water level caused by the installation position of the water level sensor is set based on this time. is configured to stop the water supply by the water supply mechanism when a delay time elapses. The delay time is the time required for water to move to the soil existing between each auxiliary underdrain, The water supply control unit and is a value set based on the time calculated based on the effective void ratio and saturation coefficient of the soil. ru is at this point.

[0018] After the water supply mechanism starts supplying water, and after the water level detected by the water level sensor reaches the target water level, the water supply mechanism stops supplying water when a predetermined delay time has elapsed. This allows an amount of irrigation water equivalent to the delay time to be used to correct the imbalance between the water level near the water supply mechanism and the water level at a location further away from the water supply mechanism.

[0019] By setting the delay time to the time required to correct the difference between the water level at the water level sensor's installation location and the water level at a location further away from the sensor, it is possible to adjust the water level to an appropriate level while avoiding unnecessary water supply.

[0020] Irrigation water supplied from the water supply mechanism to the underground drainage pipe seeps into the soil near the pipe as it flows through it, and eventually flows into auxiliary drainage channels arranged at predetermined intervals. The irrigation water flowing inside each auxiliary drainage channel seeps into the soil between adjacent channels from the sides of the channel. Since there is no significant difference between the time it takes for the water level detected by a water level sensor installed near the base end of the underground drainage pipe to reach the target water level and the time it takes for the irrigation water to move from the underground drainage pipe to the auxiliary drainage channels, the time required for water to seep from the auxiliary drainage channels into the surrounding soil can be used as a delay time to suppress variations in groundwater levels across the field area.

[0021] Since auxiliary drains are arranged at predetermined intervals so as to intersect with the main drain pipes in a plan view, the time required for water to move from both auxiliary drains to saturate the soil between adjacent auxiliary drains can be calculated based on the soil's effective porosity and saturation coefficient. Effective porosity refers to the proportion of interparticle voids in the soil that are capable of water flow. It is a fraction of the porosity, which is expressed as a percentage of the volume occupied by voids relative to the total volume of soil, and is measured for each field or is a value that is assumed in advance. The saturation coefficient refers to the saturation rate relative to the effective porosity.

[0022] Same number three The characteristic configuration is, A field water management device comprising: a water supply mechanism for supplying irrigation water to a field; a water level sensor installed near the water supply mechanism; and a water supply control unit that controls the water supply by the water supply mechanism based on the water level detected by the water level sensor so that the water level in the field reaches a target water level, The field is a large paddy field exceeding a predetermined area, and the water supply control unit operates from the start of water supply by the water supply mechanism until the field water level detected by the water level sensor reaches the target water level. The time required to correct the bias in the detected water level caused by the installation position of the water level sensor is set based on this time. The water supply mechanism is configured to stop supplying water once the delay time has elapsed, and the delay time is Calculated by the water supply control unit, The key point is that the water flow in the aforementioned field is considered as a one-dimensional, uniform flow, and the average flow velocity is calculated using Manning's formula. The value is then set based on the time calculated based on the value obtained by dividing the flow distance by the average flow velocity.

[0023] In large-scale fields, when viewing soil water flow macroscopically, we can assume a one-dimensional, uniform flow, meaning that the water depth and velocity are equal at every cross-section within the soil. By applying Manning's formula and dividing the flow distance by the average velocity, we can determine the time it takes for water to travel. Manning's formula, given by average velocity U, Manning's roughness coefficient n, average water depth ha, and hydraulic gradient I, is U = (1 / n)·ha 2 / 3 ·I 1 / 2 It is expressed as follows. By measuring Manning's roughness coefficient n, average water depth ha, and hydraulic gradient I, the average flow velocity U can be determined, and the delay time can be determined by dividing the expected water travel distance by the average flow velocity.

[0024] Same number four The characteristic configuration is, A field water management device comprising: a water supply mechanism for supplying irrigation water to a field; a water level sensor installed near the water supply mechanism; and a water supply control unit that controls the water supply by the water supply mechanism based on the water level detected by the water level sensor so that the water level in the field reaches a target water level, The aforementioned field is a large paddy field exceeding the specified area, The water supply control unit is configured to stop water supply by the water supply mechanism after a delay period has elapsed, which is set based on the time required to correct any bias in the detected water level caused by the installation position of the water level sensor, following the start of water supply by the water supply mechanism and the field water level detected by the water level sensor reaching the target water level. The aforementioned delay time is Calculated by the water supply control unit,The key feature is that it is a value set based on the time it takes for the water level near the drainage mechanism that discharges excess water from the field to reach the target water level, which is calculated by analyzing the water flow in the field using a planar unsteady flow analysis model.

[0025] In large-scale fields, a planar unsteady flow analysis model can be used to calculate the time required to eliminate the water level difference between the water level near the water supply mechanism and the water level near the drainage mechanism.

[0026] The field water management system according to the present invention First The feature configuration is, The system includes a water supply mechanism that supplies irrigation water to a field, a water level sensor installed near the water supply mechanism, and a water supply control unit that controls the water supply by the water supply mechanism based on the water level detected by the water level sensor so that the water level in the field reaches a target water level. A field water management system comprising a field water management device, a remote control terminal for setting remote operation information to the water supply control unit provided in each field water management device, and a remote control device for remotely controlling each field water management device based on the remote operation information set by the remote control terminal, wherein the remote control device is configured to transmit a control command to the water supply control unit so that the water level in the field reaches a target level based on the remote operation information input from the remote control terminal, and to transmit a water supply completion report to the remote control terminal upon receiving a water supply completion response from the water supply control unit. The field comprises an underground irrigation system comprising a drainage pipe positioned at the bottom of a guide channel formed underground along one side of the levee, and auxiliary drainage channels positioned above the guide channel at predetermined intervals so as to intersect with the drainage pipe in a plan view, the water supply mechanism connected to the base end of the drainage pipe, and the water level sensor positioned near the base end of the drainage pipe, and the water supply control unit is configured to stop water supply by the water supply mechanism after a delay time has elapsed, which is set based on the time required to eliminate any bias in the detected water level caused by the installation position of the water level sensor, after the groundwater level detected by the water level sensor has reached the target water level, and the delay time is the time required for water to move into the soil between each auxiliary drainage channel, and is set based on a time calculated by the water supply control unit based on the permeability coefficient of the soil, or a time calculated by the water supply control unit based on the effective porosity and saturation coefficient of the soil. It's at a single point.

[0027] For example, if a field manager uses a remote control terminal to set the water level in each field to the target level on the remote control device, the remote control device can remotely control the water supply control unit installed in each field water management device to remotely control the water level in each field to reach the target level.

[0028] The second characteristic configuration includes a water supply mechanism that supplies irrigation water to a field, a water level sensor installed near the water supply mechanism, and a water supply control unit that controls the water supply by the water supply mechanism based on the water level detected by the water level sensor so that the water level in the field reaches a target water level. A field water management device, A field water management system comprising: a remote control terminal for setting remote operation information for the water supply control unit provided in each field water management device; and a remote control device for remotely controlling each field water management device based on the remote operation information set by the remote control terminal, wherein the remote control device is configured to transmit a control command to the water supply control unit so that the water level in the field reaches a target water level based on the remote operation information input from the remote control terminal, and to transmit a water supply completion report to the remote control terminal upon receiving a water supply completion response from the water supply control unit, wherein the field is a large paddy field of a predetermined size or larger, and the water supply control unit operates from the start of water supply by the water supply mechanism until the water level detected by the water level sensor reaches the target water level. The water supply mechanism is configured to stop supplying water and transmit a water supply completion response to the remote control device when a delay time, which is set based on the time required to eliminate the bias in the detected water level caused by the installation position of the water level sensor, has elapsed. The delay time is a value calculated by the water supply control unit, which calculates the average flow velocity from Manning's formula by considering the water flow in the field as a one-dimensional uniform flow, and sets the time based on the value obtained by dividing the flow distance by the average flow velocity, or a value calculated by the water supply control unit, which is calculated by analyzing the water flow in the field using a planar unsteady flow analysis model, and sets the time it takes for the water level near the drainage mechanism that discharges excess water from the field to reach the target water level. [Effects of the Invention]

[0029] As described above, the present invention provides a field water management device and a field water management system that can adjust the field water level to a target level while suppressing variations, even when there is a difference between the water level at the installation location of the water level sensor and the water level at other locations in the field. [Brief explanation of the drawing]

[0030] [Figure 1] Diagram illustrating the field water management system. [Figure 2] (a) is a plan view diagram of the underground irrigation system in the field, (b) is a cross-sectional diagram of the drainage pipe and auxiliary drainage system, and (c) is a plan view diagram of the water flow path for irrigation. [Figure 3] Diagram illustrating how the groundwater level changes at the base of the drainage pipe and at a location away from the drainage pipe in response to the supply of underground irrigation water. [Figure 4] Diagram illustrating the procedure for controlling the groundwater level in underground irrigation. [Figure 5] (a) is an explanatory diagram of the equations of motion and continuity used in plane unsteady flow analysis, and (b) is an explanatory diagram showing the consideration of the field water level distribution used in plane unsteady flow analysis. [Figure 6] Diagram illustrating the concept of water depth and flow velocity at time t when performing plane unsteady flow analysis. [Best Mode for Carrying Out the Invention]

[0031] The field water management device and field water management system according to the present invention will be described below. [Configuration of a field water management system equipped with underground irrigation facilities] Figure 1 shows a field water management system 1 equipped with underground irrigation facilities. The field water management system 1 comprises a water supply mechanism 10 located at one end of the field 2 to supply irrigation water, a capacitive water level sensor S installed near the water supply mechanism 10, a drainage mechanism 30 located at the other end of the field 2 to discharge excess water from the field 2, and a water supply control unit 20 that controls the water supply by the water supply mechanism 10 and the drainage water level by the drainage mechanism 30 based on the water level detected by the water level sensor S so that the water level in the field 2 reaches a target water level. The water supply control unit 20 may be configured by dividing it into a water supply control unit that controls the water supply mechanism 10 and a drainage control unit that controls the drainage mechanism 30. Furthermore, the water level sensor S is not limited to a capacitive type, and other types of sensors can also be used.

[0032] The water supply mechanism 10 is a device that guides irrigation water flowing through water pipelines 4, which are laid along the levees 3 of each field 2, to the field 2 via a water conduit. It is equipped with a water supply box and a water tap. The outlet of the water tap is equipped with a water supply pipe 12 that communicates with the base end of the underground drainage pipe 44 of the underground irrigation facility 40, which will be described later, and a gate valve. By switching the gate valve, it is possible to switch between supplying water to the field 2 and supplying water to the underground drainage pipe 44.

[0033] The water tap comprises a cylindrical valve box, a valve seat protruding from the inner circumference of the valve box, and a disc-shaped valve body positioned opposite the valve seat. The lower end of the valve box is connected to the water conduit. A motor-driven actuator is provided at the upper end of the valve box to move the valve body up and down. When the valve body is moved upward, water is supplied to field 2 from the outlet provided in the valve box.

[0034] The drainage mechanism 30 includes a drainage basin, a support frame installed at the bottom of the drainage basin, a cylindrical drain pipe supported by the support frame so as to be movable up and down, and a motor-driven lifting mechanism that moves the drain pipe up and down. The upper end opening of the drain pipe functions as a drain outlet, and excess irrigation water supplied to the field 2 overflows from this outlet and flows out into the drainage channel 6 via the discharge channel 5.

[0035] The water supply control unit 20 drives a motor in the water supply mechanism 10 to open or close the water tap, and drives a motor in the drainage mechanism 30 to move the drain pipe up and down. The water supply control unit 20 adjusts the drainage water level by the drainage mechanism 30 to reach the target water level, and controls the opening and closing of the water tap based on the detected water level input from the water level sensor S. The drainage water level becomes the target water level for field 2. In the case of a drainage mechanism 30 that is not motor-driven, the height of the drain pipe will be adjusted manually.

[0036] The configuration of the underground irrigation system is illustrated in Figures 1 and 2(a) and (b). The underground irrigation system 40 includes a drainage pipe 44 located at the bottom of a guide channel 42 formed underground along one side of the levee, and auxiliary drainage channels 46 arranged at predetermined intervals above the guide channel 42 so as to intersect with the drainage pipe 44 in a plan view. The water supply pipe 12 of the water supply mechanism 10 is connected to the base end of the drainage pipe 44, and a water level sensor S is located near the base end of the drainage pipe 44.

[0037] A water supply mechanism 10 is installed on one end of the field 2, which is surrounded by ridges and has a roughly rectangular shape when viewed from above, and a drainage mechanism 30 is installed on the other end. Three guide grooves 42 are formed in a parallel position from the water supply mechanism 10 to the drainage mechanism 30.

[0038] As shown in Figure 2(b), each guide channel 42 is filled with drainage material such as rice husks, wood chips, and crushed stone, and a drainage pipe 44 with numerous fine openings formed on its circumferential surface is installed at the bottom of the guide channel 42. The base and terminal ends of the three drainage pipes 44 are connected by connecting pipes. The drainage pipes 44 are installed at intervals of 10m in the ground at a depth of 60cm from the paddy field surface G of field 2.

[0039] The auxiliary drainage channels 46 are located 40 cm below the surface G of field 2, directly above each guide channel 42, at 1 m intervals, and consist of cavities with a diameter of approximately 5 cm.

[0040] As shown in Figure 2(c), irrigation water supplied from the water supply pipe 12 of the water supply mechanism 10 to the central drainage pipe 44 flows through connecting pipes to the drainage pipes 44 on both sides, and flows out into the guide channel 42 through openings formed around the drainage pipes 44. The outflowing water rises up the guide channel 42 along the drainage material filling the guide channel 42, flows into the auxiliary drainage channel 46 formed above it, flows along the auxiliary drainage channel 46, and then diffuses into the ground of the field 2 from the auxiliary drainage channel 46.

[0041] The underground irrigation system 40 is installed to adjust the moisture content of field 2 when it is converted from a rice paddy to a field crop. Therefore, by switching the gate valve before and after the conversion, it is possible to switch between supplying water from the water tap to the surface of field 2 or supplying it to the underground drainage pipe 44 via the water supply pipe 12. At the same time, if necessary, the water level sensor S is also replaced with an appropriate type of sensor, and the height of the drain pipe provided in the drainage mechanism 30 is adjusted. Note that if a sensor capable of measuring both the water level in the paddy during rice cultivation and the groundwater level during field crop cultivation with the underground irrigation system 40 is used as the water level sensor S, replacement is unnecessary. Also, if the drainage mechanism 30 cannot be used for both rice cultivation and field crop cultivation with the underground irrigation system 40, separate drainage mechanisms 30 corresponding to each case should be provided, and the height of the drain pipe should be adjusted to the appropriate level for each case.

[0042] The configuration, materials, size, etc., of the water supply mechanism 10, drainage mechanism 30, water level sensor S, and underground irrigation equipment 40 described above are not particularly limited, and can be implemented using publicly known materials as long as they perform similar functions.

[0043] [Field water management system configuration] The field water management system 100 is a system that centrally manages field water management devices 1 installed in multiple fields 2. It is a system in which a water supply control unit 20 installed in each field 2, a remote operation terminal 60 consisting of a mobile terminal such as a smartphone owned by the manager of each field 2, and a remote control device 50 that remotely controls each water supply control unit 20 are connected to each other via the internet so that they can communicate with one another. For example, a cloud server is used to function as the remote control device 50.

[0044] Furthermore, if the water supply control unit 20 is configured as a water supply control unit and a drainage control unit separately, each of the water supply control unit and the drainage control unit may be configured to be connectable to the remote control device 50, or it may suffice for either the water supply control unit or the drainage control unit to be configured to be connectable to the remote control device 50. For example, if the water supply control unit is connected to the remote control device 50, the drainage control unit may be configured to be indirectly controlled by the water supply control unit.

[0045] The remote control device 50 is configured to send a control command to the water supply control unit 20 based on remote operation information input from the remote operation terminal 60, so that the water level in field 2 reaches the target water level, and to send a water supply completion report to the remote operation terminal 60 when it receives a water supply completion response from the water supply control unit 20.

[0046] The water supply control unit 20 is configured to send a water supply completion response to the remote control device 50 when the water level in field 2 reaches the target water level after the water supply mechanism 10 has started supplying water. The water level in field 2 reaching the target water level includes when the water level in field 2 detected by the water level sensor S reaches the target water level, or when a preset delay time has elapsed after the water level in field 2 detected by the water level sensor S reaches the target water level.

[0047] [Operation of the water supply control unit installed in the field water management system] When cultivating rice in a standard 30-are dispersed paddy field, and controlling the water level of field 2 to a predetermined level, it is sufficient to stop the water supply by the water supply mechanism 10 when the water level in field 2 detected by the water level sensor S reaches the target water level. However, when converting to upland crops and controlling the groundwater level to a target level using the underground irrigation equipment 40 described above, stopping the water supply by the water supply mechanism 10 when the groundwater level detected by the water level sensor S reaches the target water level may result in an uneven supply of water to the entire underground area of ​​field 2. Similarly, when cultivating rice in a large-scale paddy field of 1 hectare or more, stopping the water supply by the water supply mechanism 10 when the field water level detected by the water level sensor S reaches the target water level may result in an uneven supply of water to the entire field 2.

[0048] The present invention was made to address such cases, and the water supply control unit 20 is configured to stop water supply by the water supply mechanism 10 after a preset delay time has elapsed, following the start of water supply by the water supply mechanism 10 and after the water level detected by the water level sensor S has reached the target water level.

[0049] After the start of water supply by the water supply mechanism 10, and after the water level detected by the water level sensor S reaches the target water level, the water supply by the water supply mechanism 10 is stopped when a predetermined delay time has elapsed. This allows an amount of irrigation water equivalent to the delay time to be used to eliminate the imbalance between the water level near the water supply mechanism 10 and the water level at a location far from the water supply mechanism 10.

[0050] The delay time is preferably set based on the time required to correct the bias in the detected water level caused by the installation location of the water level sensor S. By setting the delay time to the time required to correct the bias between the water level at the installation location of the water level sensor S and the water level at a location separated from the installation location of the water level sensor S, it is possible to adjust to an appropriate water level while avoiding unnecessary water supply.

[0051] Specifically, the water supply control unit 20 is configured to stop water supply by the water supply mechanism 10 after a delay time has elapsed following the start of water supply by the water supply mechanism 10 and the groundwater level detected by the water level sensor S reaching the target water level. The delay time is the time required for water to move into the soil present between each auxiliary drainage channel 46, and can be set to a value based on a time calculated based on the soil's permeability coefficient.

[0052] Irrigation water supplied from the water supply mechanism 10 to the drainage pipe 44 fills the guide channel 42 in which the drainage pipe 44 is installed as it flows through the drainage pipe 44, eventually seeping into the nearby soil and flowing into the auxiliary drainage channels 46. The irrigation water flowing inside each auxiliary drainage channel 46 seeps into the soil between adjacent auxiliary drainage channels 46 from the side of the auxiliary drainage channel 46. Since there is no significant difference between the time it takes for the water level detected by the water level sensor S installed near the base end of the drainage pipe 44 to reach the target water level and the time it takes for the irrigation water to move from the drainage pipe 44 to the auxiliary drainage channels 46, the time required for water to seep from the auxiliary drainage channels 46 into the surrounding soil can be used as a delay time to suppress variations in the groundwater level across the field 2.

[0053] Figure 3 shows an example of the characteristics when the groundwater level is controlled to a target level using the underground irrigation system 40. The graph shows the change in groundwater level between the base end of the drainage pipe 44 and the adjacent auxiliary drainage pipe 46 at the other end of the drainage pipe 44 when water supply to the underground irrigation system 40 is started at 8:30. When the target water level is set to 40 cm underground, the same as the auxiliary drainage pipe 46, a delay of approximately 3 hours occurs between the time the groundwater level at the base end of the drainage pipe 44 reaches the target water level and the time the groundwater level between the adjacent auxiliary drainage pipe 46 at the other end of the drainage pipe 44 reaches the target water level. Note that the delay time varies depending on the size of the field, the composition of the soil, the configuration of the underground irrigation system 40, etc., but similar characteristics are observed in all fields.

[0054] It goes without saying that if the delay time is measured in advance for each field, the delay time can be set based on those measurements. Since the auxiliary drainage pipes 46 are arranged at predetermined intervals so as to intersect with the drainage pipes 44 in a plan view, the time required for water to move from both auxiliary drainage pipes 46 to the soil between adjacent auxiliary drainage pipes 46 can be calculated based on the soil's permeability coefficient.

[0055] The permeability coefficient is a coefficient that represents the degree to which water can easily pass through soil. If the cross-sectional area of ​​the soil or sand layer is A, the length is l, the gradient of water flow (hydraulic gradient) is h, and the flow rate is Q, then the permeability coefficient k is defined as Q = kA·h / l (unit: length / hour). Generally, the smaller the soil particle size, the smaller the permeability coefficient k, and the larger the particle size, the larger the permeability coefficient k. If the permeability coefficient k is measured in advance for each field, the time required for water to travel a predetermined distance (50 cm in this embodiment) from the auxiliary drain 46 can be determined. The permeability coefficient k can also be estimated from the water level decrease during rice cultivation. For example, when controlling the flooding of each field during rice cultivation, the amount of water lost from the field can be determined from the amount of water level decrease per unit time measured by the water level sensor. The amount of water lost can be used to estimate the permeability coefficient k by subtracting the average evapotranspiration rate at that time from the amount of water lost.

[0056] Let's explain another example. The water supply control unit 20 is configured to stop water supply by the water supply mechanism 10 after a delay time has elapsed following the start of water supply by the water supply mechanism 10 and the groundwater level detected by the water level sensor S reaching the target water level. The delay time is the time required for water to move into and saturate the soil between each auxiliary drainage channel 46, and can be set based on a time calculated based on the effective porosity and saturation coefficient of the soil.

[0057] Since the auxiliary drains 46 are arranged at predetermined intervals so as to intersect with the drain pipes 44 in a plan view, the time required for water to move from both auxiliary drains 46 to the soil between adjacent auxiliary drains 46 and saturate can be calculated based on the effective porosity and saturation coefficient of the soil. The effective porosity refers to the proportion of interparticle voids in the soil that are capable of water flow, and is a value of one-tenth to one-tenth of the porosity, which is the ratio of the volume occupied by voids to the total volume of the soil expressed as a percentage, and is measured for each field or is a value that is assumed in advance. The saturation coefficient refers to the sufficiency rate relative to the effective porosity.

[0058] In this embodiment, to irrigate a distance of 1 m between adjacent auxiliary drains 46, the required water volume can be calculated from the time it takes for the soil to become saturated 50 cm from the auxiliary drain 46. When the water supply volume is Q, the field area is X, and the delay time is T, the amount of water required for the irrigation area is given by φ cm (diameter of auxiliary drain 46) × l cm (half the distance of the auxiliary drain 46) × s (saturation coefficient) × η (effective porosity). The delay time can be calculated from the formula (Q / X) × T = φ × l × s × η. The values ​​of the saturation coefficient s and the effective porosity η can be determined in advance by measuring them for each field.

[0059] [Water supply control operation for fields equipped with underground irrigation facilities using a field water management system] If the field 2 to be controlled is a standard 30-are paddy field and is being used for rice cultivation (SA1), the remote control device 50 instructs the water supply control unit 20 of the field to set a target water level for flooding control and also instructs the drainage water level of the drainage mechanism 30, and transmits a water supply start command. Based on the instructions from the remote control device 50, the water supply control unit 20 sets the target water level in its own memory (SA2), adjusts the drainage water level of the drainage mechanism 30 (SA3), and starts water supply (SA4).

[0060] The water supply control unit 20 continues to supply water until the water level detected by the water level sensor S reaches the target water level, and when the target water level is reached (SA5, Y), it stops supplying water (SA6).

[0061] If the field 2 to be controlled is a standard 30-are paddy field and is being converted to another crop (SA1), the remote control device 50 sends a command to start water supply to the water supply control unit 20 of the field, instructing it to determine the target groundwater level, parameters for determining the delay time, and the drainage water level from the drainage mechanism 30. In the case of crop conversion, a groundwater level meter is installed in advance by the field manager as needed.

[0062] The water supply control unit 20 of the field sets a target groundwater level in its own memory (SA8), sets a parameter to determine the delay time (SA9), adjusts the drainage water level of the drainage mechanism 30 (SA10), and starts water supply (SA11) based on instructions from the remote control device 50. The target groundwater level is set, in principle, to the installation depth of the auxiliary drainage pipe 46.

[0063] The water supply control unit 20 continues to supply water until the groundwater level detected by the water level sensor S reaches the target level. When the target level is reached (SA12, Y), it calculates a delay time based on the parameters (SA13). When the delay time has elapsed (SA14, Y), it stops the water supply and sends a water supply completion report to the remote control device 50 (SA7). Subsequently, the remote control device 50 sends a water supply completion report to the remote operation terminal 60 (SA15). If a drainage mechanism 30 that is not motor-driven is used, the field manager will manually adjust the height of the drain pipe in advance, instead of steps SA3 and SA10.

[0064] The parameters used to determine the delay time are the permeability coefficient k mentioned above, or the values ​​shown in the formula (Q / X) × T = φ × l × s × η, which calculates the delay time.

[0065] [Water supply control operation for large-scale paddy fields] Figure 4 illustrates the water supply control operation for a field equipped with underground irrigation facilities, but the basic process for water supply control operation for a paddy field in the second section is the same. In step SA1, it is determined whether the paddy field is a large plot or a standard plot. If it is a standard plot, steps SA2 through SA5, SA6, SA7, and SA15 are executed. A large plot refers to a paddy field with a size of 1 hectare or more.

[0066] In step SA1, if it is a large-scale paddy field, the processes from step SA8 to SA14, SA6, SA7, and SA15 are executed. In step SA8, the target water level (flood level) of the field is set, in step SA9, parameters for calculating the delay time for large-scale paddy fields are set, and in step SA13, the delay time is calculated based on these parameters. If the delay time for water supply is measured in advance for each field, the delay time corresponding to the individual water supply can be set in advance.

[0067] If field 2 is a large paddy field exceeding a predetermined number of plots, the water supply control unit 20 is configured to stop water supply by the water supply mechanism 10 after a delay time has elapsed following the start of water supply by the water supply mechanism 10 and the field water level detected by the water level sensor S reaching the target water level. If the delay time in the target field has not been measured in advance, the water flow in field 2 can be treated as a one-dimensional uniform flow, the average flow velocity can be calculated from Manning's formula, and the delay time can be set based on the time calculated based on the value obtained by dividing the flow distance by the average flow velocity.

[0068] In a large - scale field, when macroscopically observing the water flow in the soil, assuming a one - dimensional uniform flow, that is, a flow with equal water depth and flow velocity at any cross - section in the soil, the Manning's formula is applied. By dividing the flow - down distance by the average flow velocity, the time for water to move can be obtained. When the average flow velocity is U, the Manning's roughness coefficient is n, the average water depth is ha, and the hydraulic gradient is I, Manning's formula is U=(1 / n)·ha 2 / 3 ·I 1 / 2 is expressed as. By measuring the Manning's roughness coefficient n, the average water depth ha, and the hydraulic gradient I, the average flow velocity U can be obtained, and by dividing the assumed water movement distance by the average flow velocity, the delay time can be obtained.

[0069] Also, when Field 2 is a large - scale paddy field with a plot area of a predetermined area or more, the delay time can be set based on the time until the water level near the drainage mechanism reaches the target water level, which is calculated by analyzing the water flow in Field 2 using a plane unsteady - flow analysis model.

[0070] In a large - scale field, by using a plane unsteady - flow analysis model, the time required to eliminate the water - level difference between the water level near the water - supply mechanism and the water level near the drainage mechanism can be calculated.

[0071] In the plane unsteady - flow analysis model, the field is divided into meshes of arbitrary width, and the equations of motion and continuity shown in Fig. 5(a) are used. Here, x and y are the mesh widths in each direction, t is time, V x ,V y are the flow velocities in each direction, i x ,i y are the gradients in each direction, h is the water level of each mesh at time t, n is the Manning's roughness coefficient, g is the acceleration due to gravity, and Q xy represents the flow rate per unit mesh width.

[0072] As shown in Fig. 5(b), it is assumed that the water surface of the field becomes lower as it moves away from the water - supply mechanism, forming a linearly gentle gradient. The measured value of the hydraulic gradient of the field required for the calculation is adopted. The above - mentioned equations of motion and continuity are solved using the finite - difference method. Figure 6 illustrates the concepts of propulsion and flow velocity at time t. Within each mesh, which is created by dividing the field into arbitrary widths, water depth data exists, and flow velocity exists between adjacent meshes due to differences in water depth. k and l represent the mesh positions in the x and y directions, respectively.

[0073] Water depth at time t t h xy To find this, we can use the water depth and current velocity from the previous calculation time t-1. t-1 h xy Flow velocity at time t at the four corners t U is determined from the equation of motion. In Figure 6, only one velocity point is shown in the area where the grid overlaps, but in the calculation there are two data points, in the x and y directions. After determining the velocity, the water depth at t-1 is calculated. t-1 h xy By calculating the water balance with the four adjacent meshes in the continuity equation, the water depth at time t can be determined. t h xy This allows us to determine the water surface conditions in the field at time t. By performing this operation for all meshes, we can refine the conditions of the water surface in the field at time t. Similarly, the water depth at t+1 can be calculated using the water depth and flow velocity at time t, and the delay time can be determined by repeating this process until the water depth in the field stabilizes.

[0074] In the embodiments described above, we explained a field water management system that performs water level control for fields equipped with underground irrigation facilities in standard-sized plots and capable of switching between rice cultivation and crop rotation, and a field water management system that performs water level control for a group of fields where standard-sized plots and large-sized plots are mixed. However, a field water management system that performs water level control for fields equipped with underground irrigation facilities in large-sized plots and capable of switching between rice cultivation and crop rotation can be configured in a similar manner.

[0075] The embodiments described above are merely examples of the present invention, and it is not intended that this description limits the technical scope of the present invention. It goes without saying that the specific configurations of the water supply mechanism, drainage mechanism, underground irrigation equipment, water supply control unit, remote control device, etc., can be appropriately modified and designed within the scope that achieves the effects of the present invention. [Explanation of Symbols]

[0076] 100: Field water management system 1: Field water management system 2: Field S: Water level sensor 10: Water supply mechanism 20: Water supply control unit 30: Drainage mechanism 40: Underground irrigation facilities 41: Guide groove 44: Underground drainage pipe 46: Auxiliary culvert

Claims

1. A field water management device comprising: a water supply mechanism for supplying irrigation water to a field; a water level sensor installed near the water supply mechanism; and a water supply control unit that controls the water supply by the water supply mechanism based on the water level detected by the water level sensor so that the water level in the field reaches a target water level, The field is equipped with an underground irrigation system comprising a drainage pipe located at the bottom of a guide channel formed underground along one side of the levee, and auxiliary drainage channels arranged at predetermined intervals above the guide channel so as to intersect with the drainage pipe in a plan view, the water supply mechanism being connected to the base end of the drainage pipe, and the water level sensor being located near the base end of the drainage pipe. The water supply control unit is configured to stop the water supply by the water supply mechanism after a delay period has elapsed, which is set based on the time required to correct any bias in the detected water level caused by the installation position of the water level sensor, following the start of water supply by the water supply mechanism and the groundwater level detected by the water level sensor reaching the target water level. The aforementioned delay time is the time required for water to move into the soil between each auxiliary drain, and is a value set by the water supply control unit based on the time calculated based on the permeability coefficient of the soil, in a field water management device.

2. A field water management device comprising: a water supply mechanism for supplying irrigation water to a field; a water level sensor installed near the water supply mechanism; and a water supply control unit that controls the water supply by the water supply mechanism based on the water level detected by the water level sensor so that the water level in the field reaches a target water level, The field is equipped with an underground irrigation system comprising a drainage pipe located at the bottom of a guide channel formed underground along one side of the levee, and auxiliary drainage channels arranged at predetermined intervals above the guide channel so as to intersect with the drainage pipe in a plan view, the water supply mechanism being connected to the base end of the drainage pipe, and the water level sensor being located near the base end of the drainage pipe. The water supply control unit is configured to stop the water supply by the water supply mechanism after a delay period has elapsed, which is set based on the time required to correct any bias in the detected water level caused by the installation position of the water level sensor, following the start of water supply by the water supply mechanism and the groundwater level detected by the water level sensor reaching the target water level. The aforementioned delay time is the time required for water to move into the soil between each auxiliary drainage channel, and is a value set by the water supply control unit based on the time calculated based on the effective porosity and saturation coefficient of the soil in the field water management device.

3. A field water management device comprising: a water supply mechanism for supplying irrigation water to a field; a water level sensor installed near the water supply mechanism; and a water supply control unit that controls the water supply by the water supply mechanism based on the water level detected by the water level sensor so that the water level in the field reaches a target water level, The aforementioned field is a large paddy field exceeding the specified area, The water supply control unit is configured to stop water supply by the water supply mechanism after a delay period has elapsed, which is set based on the time required to correct any bias in the detected water level caused by the installation position of the water level sensor, following the start of water supply by the water supply mechanism and the field water level detected by the water level sensor reaching the target water level. The aforementioned delay time is a value set based on a time calculated by the water supply control unit, which calculates the average flow velocity from Manning's formula by considering the water flow in the field as a one-dimensional uniform flow, and divides the flow distance by the average flow velocity.

4. A field water management device comprising: a water supply mechanism for supplying irrigation water to a field; a water level sensor installed near the water supply mechanism; and a water supply control unit that controls the water supply by the water supply mechanism based on the water level detected by the water level sensor so that the water level in the field reaches a target water level, The aforementioned field is a large paddy field exceeding the specified area, The water supply control unit is configured to stop water supply by the water supply mechanism after a delay period has elapsed, which is set based on the time required to correct any bias in the detected water level caused by the installation position of the water level sensor, following the start of water supply by the water supply mechanism and the field water level detected by the water level sensor reaching the target water level. The aforementioned delay time is a value calculated by the water supply control unit and determined by analyzing the water flow in the field using a planar unsteady flow analysis model, and is set based on the time it takes for the water level near the drainage mechanism that discharges excess water from the field to reach the target water level.

5. A field water management device comprising: a water supply mechanism for supplying irrigation water to a field; a water level sensor installed near the water supply mechanism; and a water supply control unit that controls the water supply by the water supply mechanism based on the water level detected by the water level sensor so that the water level in the field reaches a target water level. A remote control terminal for setting remote control information for the water supply control unit provided in each field water management device, A remote control device that remotely controls each field water management device based on remote control information set by the aforementioned remote control terminal, A field water management system that is connected in a communication manner, The remote control device is configured to transmit a control command to the water supply control unit so that the water level in the field reaches the target water level, based on the remote operation information input from the remote operation terminal, and to transmit a water supply completion report to the remote operation terminal upon receiving a water supply completion response from the water supply control unit. The field is equipped with an underground irrigation system comprising a drainage pipe located at the bottom of a guide channel formed underground along one side of the levee, and auxiliary drainage channels arranged at predetermined intervals above the guide channel so as to intersect with the drainage pipe in a plan view, the water supply mechanism being connected to the base end of the drainage pipe, and the water level sensor being located near the base end of the drainage pipe. The water supply control unit is configured to stop the water supply by the water supply mechanism after a delay period has elapsed, which is set based on the time required to correct any bias in the detected water level caused by the installation position of the water level sensor, following the start of water supply by the water supply mechanism and the groundwater level detected by the water level sensor reaching the target water level. The aforementioned delay time is the time required for water to move into the soil between each auxiliary drainage channel, and is a value set based on the time calculated by the water supply control unit based on the permeability coefficient of the soil, or a value set based on the time calculated by the water supply control unit based on the effective porosity and saturation coefficient of the soil, in a field water management system.

6. A field water management device comprising: a water supply mechanism for supplying irrigation water to a field; a water level sensor installed near the water supply mechanism; and a water supply control unit that controls the water supply by the water supply mechanism based on the water level detected by the water level sensor so that the water level in the field reaches a target water level. A remote control terminal for setting remote control information for the water supply control unit provided in each field water management device, A remote control device that remotely controls each field water management device based on remote control information set by the aforementioned remote control terminal, A field water management system that is connected in a communication manner, The remote control device is configured to transmit a control command to the water supply control unit so that the water level in the field reaches the target water level, based on the remote operation information input from the remote operation terminal, and to transmit a water supply completion report to the remote operation terminal upon receiving a water supply completion response from the water supply control unit. The aforementioned field is a large paddy field exceeding the specified area, The water supply control unit is configured to stop supplying water by the water supply mechanism and transmit a water supply completion response to the remote control device after a delay time has elapsed, which is set based on the time required to correct any bias in the detected water level caused by the installation position of the water level sensor, following the start of water supply by the water supply mechanism and the water level sensor has reached the target water level. Field water management system wherein the delay time is a value set based on a time calculated by the water supply control unit, which calculates the average flow velocity from Manning's formula by considering the water flow in the field as a one-dimensional uniform flow, and divides the flow distance by the average flow velocity, or a value set based on the time it takes for the water level near a drainage mechanism that discharges excess water from the field to reach the target water level, which is calculated by the water supply control unit and by analyzing the water flow in the field using a plane unsteady flow analysis model.

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