Water management method and water management system

Abstract

To provide a technique for performing water management in channel for terminal.SOLUTION: A water management method is a method of controlling a flow rate of a channel 300 for terminal branched from a channel 200 for branch line. In the water management method, a flow rate in the channel 300 for terminal is controlled by both an underflow flowing a bottom part of a dam plate and an overflow flowing above a top part of the dam plate by using a composite dam 10 provided so as to have a gap between a bottom end of the dam plate and a bottom of the channel 300 for terminal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a water management method, a water management system, and a composite weir. [Background technology]

[0002] In the terminal canals of open-channel agricultural irrigation channels, the flow rate varies not only seasonally but also daily. Therefore, appropriate water level management within the terminal canals is required to ensure an even supply of water to rice paddies. Methods for managing the water level in terminal canals include adjusting the opening of water distribution gates installed at the branch points from the spur canals to the terminal canals, adjusting the opening of water taps that supply water from the terminal canals to each rice paddy field, and adjusting the height of the weir plates installed in the terminal canals for each rice paddy field.

[0003] The technologies described in Patent Documents 1 to 3 are known as techniques for managing water levels in paddy fields and terminal irrigation channels. Patent Document 1 describes a device that controls the water supply and distribution to a field by opening and closing a valve, taking into account the growth state of crops, etc. Patent Document 2 describes a device that adjusts the water level in a small paddy field by opening and closing weir plates installed in the field using a motor. Patent Document 3 describes a system that controls the water supply to a paddy field using a mountain-dividing diversion weir installed at the branch point between the irrigation channel and a downstream channel, and an overflow weir installed in the downstream channel. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-106583 [Patent Document 2] Japanese Patent Application Publication No. 2019-24401 [Patent Document 3] Utility Model Registration No. 3220836 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventional methods for managing the water level of terminal irrigation channels require opening and closing water distribution gates and water faucets, and adjusting the height of weir plates, which poses a problem in terms of the labor involved in these operations. The technologies described in Patent Documents 1 to 3 are technologies for such water level management, but there is a demand for further technologies that can reduce the labor required for managing the water level of terminal irrigation channels.

[0006] One aspect of the present invention has been made to solve the above-mentioned problems, and its object is to provide a technique for managing water in terminal irrigation channels. [Means for solving the problem]

[0007] In order to solve the above problems, one aspect of the water management method of the present invention is a water management method for controlling the flow rate of a terminal irrigation channel branching off from a branch irrigation channel, in which a composite weir is installed so as to have a gap between the lower end of the weir plate and the bottom of the terminal irrigation channel, and the flow rate in the terminal irrigation channel is controlled by both the underflow flowing below the weir plate and the overflow that exceeds the top of the weir plate.

[0008] A water management system according to one aspect of the present invention is a water management system that controls the flow rate of a terminal irrigation canal that branches off from a branch irrigation canal, and is equipped with a composite weir that is arranged so as to have a gap between the lower end of the weir plate and the bottom of the terminal irrigation canal.

[0009] A composite weir according to one embodiment of the present invention has, between the lower end of the weir plate and the bottom of the terminal irrigation channel, an underflow passage area through which underflow flowing below the weir plate passes, and an overflow passage area through which overflow that exceeds the top of the weir plate passes. [Effects of the Invention]

[0010] According to one aspect of the present invention, a technique for managing water in a terminal irrigation channel can be provided. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a block diagram showing a configuration of a main part of a water management system according to an embodiment of the present invention. [Figure 2] 1 is a schematic diagram showing a composite weir according to one embodiment of the present invention. FIG. [Figure 3] FIG. 10 is a diagram showing the results of an experiment using a conventional overflow weir and a composite weir according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Water Management System] A water management system according to one embodiment of the present invention will be described with reference to Figures 1 and 2. Figure 1 is a block diagram showing the configuration of the main components of a water management system 100 according to one embodiment of the present invention. Figure 2 is a schematic diagram showing a composite weir 10 according to one embodiment of the present invention.

[0013] The water management system 100 is a system that controls the flow rate of a terminal irrigation channel 300 that branches off from a branch irrigation channel 200. The branch irrigation channel 200 is an agricultural irrigation channel and can be an open channel type channel with the water surface in contact with the atmosphere. Multiple terminal irrigation channels 300 branch off from the branch irrigation channel 200. Farm fields 400 are adjacent to the terminal irrigation channels 300, and the multiple farm fields 400 are arranged approximately parallel to the direction of flow of the terminal irrigation channels 300. One example of the farm fields 400 is a rice paddy field.

[0014] 1, the water management system 100 includes a composite weir 10 and a water distribution gate 20. The water management system 100 may also include a water faucet 30, a control device 40, and a measurement device 50.

[0015] (Composite weir 10) The composite weir 10 is installed so that there is a gap between the lower end of the weir plate 11 and the bottom of the terminal irrigation channel 300. That is, between the lower end of the weir plate 11 and the bottom of the terminal irrigation channel, the composite weir 10 has an underflow passing area 12 through which the underflow flowing below the weir plate passes, and an overflow passing area 13 through which the overflow that exceeds the upper part of the weir plate 11 passes. This allows the flow rate in the terminal irrigation channel 300 to be controlled by both the underflow flowing below the weir plate 11 of the composite weir 10 and the overflow that exceeds the upper part of the weir plate 11. In other words, the composite weir 10 utilizes the underflow that flows below the weir plate 11 in addition to the overflow utilized in conventional overflow weirs.

[0016] The overflow passing region 13 side of the composite weir 10 may be a full-width weir, a square weir, or a triangular weir. Figure 2 shows an example in which the overflow passing region 13 side of the composite weir 10 is a full-width weir. The weir height H of the weir plate 11 (the sum of the height w of the weir plate 11 and the height d of the underflow passing region 12) can be set to the desired water depth h upstream of the weir, depending on the flow rate of the terminal irrigation channel.

[0017] Conventional overflow weirs control the flow rate in the terminal canal only by the flow that overflows the weir plate, so they have low flow capacity. As a result, an increase in flow rate in the terminal canal results in a relatively large rise in water level. In order to use such an overflow weir to maintain a constant water depth at the water supply point from the terminal canal to each field and ensure the amount of water supplied to downstream fields, it is necessary to adjust the height of the weir plate to match the flow rate in the terminal canal, and this operation requires a lot of effort.

[0018] In the water management system 100, the composite weir 10 controls the flow rate in the terminal irrigation channel 300 using both underflow and overflow, resulting in high flow capacity. Therefore, even if the flow rate in the terminal irrigation channel 300 changes, the amount of water level fluctuation is small. As a result, the water depth at the water supply point from the terminal irrigation channel 300 to each field 400 can be kept constant, and the amount of water supplied to downstream fields can also be ensured. With the composite weir 10, the water depth at the water supply point from the terminal irrigation channel 300 to each field 400 can be kept constant while the weir height H is fixed.

[0019] It is preferable that a composite weir 10 is provided for each of the multiple fields 400 adjacent to the terminal irrigation channel 300. This makes it possible to maintain a constant water depth at the water supply point from the terminal irrigation channel 300 to each field 400, thereby ensuring the amount of water supplied to each field 400.

[0020] (Water distribution gate 20) The water distribution gate 20 is provided at the branch point of the spur irrigation channel 200 and the terminal irrigation channel 300. In other words, the water distribution gate 20 is provided upstream of the terminal irrigation channel 300. In the water management system 100, the water flow from the spur irrigation channel 200 to the terminal irrigation channel 300 is controlled by opening and closing the water distribution gate 20. The type of the water distribution gate 20 is not particularly limited, and may be a sluice type or a flap type.

[0021] In the water management system 100, the water supply from the terminal irrigation channel 300 to the field 400 is controlled by a water supply hydrant 30. As an example, the water management system 100 opens the water supply hydrant 30, fixes the weir height H of the composite weir 10, and controls the water supply from the terminal irrigation channel 300 to the field 400 by opening and closing the water distribution gate 20. In the water management system 100, the water depth at the water supply point from the terminal irrigation channel 300 to each field 400 is kept constant, and the amount of water supplied to the field 400 is secured, so there is no need to adjust the opening of the water supply hydrant or the height of the weir to supply water to the field 400.

[0022] That is, with the water management system 100, it is possible to control the water supply to fields 400 adjacent to the terminal irrigation canal 300 simply by controlling the opening and closing of the water distribution gates 20. Furthermore, by opening the water supply taps 30 of each of the multiple fields 400 adjacent to the terminal irrigation canal 300, fixing the weir height H of each composite weir 10, and controlling the opening and closing of the water distribution gates 20, it is possible to collectively control the water supply to multiple fields 400. Furthermore, with the water management system 100, it is possible to maintain a constant water depth at the water supply point from the terminal irrigation canal 300 to each field 400, so it is possible to achieve a constant water supply to each field 400 simply by opening and closing the water distribution gates 20.

[0023] The opening and closing of the water distribution gate 20 can be controlled by the control device 40. The control can be based on at least one of the water level in the field 400 adjacent to the terminal irrigation canal 300 and the water level and flow rate in the terminal irrigation canal 300. For example, the control device 40 may control the opening and closing of the water distribution gate 20 by remotely operating a drive device (not shown) provided in the water distribution gate 20.

[0024] The control device 40 may control the opening and closing of the water distribution gate 20 based on at least one of the water level in the field 400 adjacent to the terminal irrigation canal 300 and the water level and flow rate in the terminal irrigation canal 300 measured by the measurement device 50. The measurement device 50 is, for example, at least one of a water level measuring device such as a water level gauge installed in the field 400, and a water level measuring device such as a water level gauge and a flow rate measuring device such as a flow meter installed in the terminal irrigation canal 300. The measurement device 50 outputs the measured data to the control device 40. The measurement device 50 may also store the measured data in a storage device (not shown) on a cloud server. For example, the control device 40 acquires the data output from the measurement device 50 via wireless communication or wired communication.

[0025] For example, when the water level in the field 400 adjacent to the terminal irrigation canal 300 measured by the measuring device 50 is low, the water level in the terminal irrigation canal 300 is low, or the flow rate is low, the control device 40 opens the water distribution gate 20 to increase the flow rate in the terminal irrigation canal 300 and increase the amount of water supplied to the field 400. Also, for example, when the water level in the field 400 adjacent to the terminal irrigation canal 300 measured by the measuring device 50 is high, the water level in the terminal irrigation canal 300 is high, or the flow rate is high, the control device 40 closes the water distribution gate 20 to reduce the flow rate in the terminal irrigation canal 300 and reduce the amount of water supplied to the field 400.

[0026] In addition, the control device 40 may control the opening and closing of the water distribution gate 20 based on at least one of the water level in the field 400 and the water level and flow rate in the terminal irrigation canal 300 so as to maintain at least one of the water level in the field 400 and the water level and flow rate in the terminal irrigation canal 300 within a predetermined range.

[0027] In this way, the water management system 100 monitors the water level in the field 400 and at least one of the water level and flow rate in the terminal irrigation canal 300, and controls the opening and closing of the water distribution gate 20 based on this data, thereby enabling automatic centralized control of water supply to the field 400 adjacent to the terminal irrigation canal 300.

[0028] [Composite weir] A composite weir according to one aspect of the present invention is a composite weir installed in a terminal irrigation canal branching off from a branch irrigation canal, and has, between the lower end of the weir plate and the bottom of the terminal irrigation canal, an underflow passing area through which underflow flowing below the weir plate passes, and an overflow passing area through which overflow that exceeds the top of the weir plate passes. In other words, the composite weir 10 provided in the water management system 100 described above is one aspect of the composite weir according to the present invention. Therefore, details of the composite weir according to this aspect of the present invention follow the description of the composite weir 10 described above.

[0029] [Water management method] A water management method according to one aspect of the present invention controls the flow rate of a terminal canal branching off from a branch canal, using a composite weir installed to provide a gap between the lower end of the weir plate and the bottom of the terminal canal to control the flow rate in the terminal canal by both underflow flowing below the weir plate and overflow over the upper part of the weir plate. The water management method can also control the flow of water from the branch canal to the terminal canal by opening and closing a water distribution gate installed at the branch point between the branch canal and the terminal canal. Furthermore, the water management method can control the flow rate in the terminal canal by using a composite weir installed for each of multiple fields adjacent to the terminal canal.

[0030] The water management method also controls the water supply from the terminal irrigation canal to the field by opening a water supply valve that controls the water supply from the terminal irrigation canal to the field and fixing the height H of the composite weir, and by opening and closing the water distribution gate. Furthermore, the water management method controls the opening and closing of the water distribution gate based on at least one of the water level in the field adjacent to the terminal irrigation canal and the water level and flow rate in the terminal irrigation canal.

[0031] That is, the above-described water management system 100 is one aspect of a water management system for carrying out a water management method according to the present invention. Therefore, details of the water management method according to one aspect of the present invention are in accordance with the description of the above-described water management system 100.

[0032] Conventionally, when supplying water to fields using weir plates (e.g., full-width weirs) in open-channel terminal canals, the number of water supply points in the field may need to be adjusted to ensure the required amount of water supply, resulting in a significant amount of effort required to change the installation locations of the weir plates. Therefore, if the water level at each water supply point could be maintained with the weir plates fixed throughout the irrigation period and the required amount of water supply could be ensured, this effort could be reduced. Conventional techniques that suppress water level fluctuations by using inclined weirs or duckbill weirs with long overflow sections to increase flow capacity have been applied to main canals, but the facility structures are large and unsuitable for use in terminal canals.

[0033] According to one aspect of the water management method of the present invention, a simple structure using conventional weir plates can be used to increase the flow capacity by using a composite weir that combines overflow and underflow, thereby suppressing water level fluctuations and ensuring water supply volume with a simple facility structure that can also be applied to terminal irrigation canals.

[0034] The above-described configuration of the present invention leads to the maintenance and development of agriculture, which can contribute to the achievement of Goal 2 of the Sustainable Development Goals (SDGs), "Zero Hunger."

[0035] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Example]

[0036] Hydraulic experiments and hydraulic calculations were used to compare the effectiveness of a conventional full-width weir and a composite weir according to one embodiment of the present invention as water level control facilities in a terminal irrigation channel.

[0037] (Experimental Method) Hydraulic experiments were conducted in an acrylic rectangular open channel with a length of 10 m, sidewall height of 30 cm, width of 25 cm, and no channel gradient, with a model full-width weir and a composite weir installed 7 m from the upstream end. Two experimental cases were performed: a full-width weir (weir height H = 12 cm) and a composite weir (weir height H = 13 cm, underflow opening d = 1 cm). The discharge coefficients C of the full-width weir and composite weir were calculated using the relationship equation for the discharge of the overflow weir based on the measured discharge and water depth upstream of the weir.

[0038] Assuming the application of a compound weir to a terminal irrigation channel, a non-uniform flow calculation was carried out for the on-site channel using the flow coefficient C obtained from hydraulic experiments. The non-uniform flow calculation is a sequential calculation method based on Bernoulli's theorem. The calculation conditions are as shown in Table 1, with reference to the specifications of Area A, where water level adjustment is carried out in the terminal irrigation channel using a full-width weir, and are a channel length of 50m, a channel gradient of 1 / 580, and an upstream end discharge of 0.03m. 3 / s. [Table 1]

[0039] The locations of weirs G1 and G2 were assumed to be one point on the 30m short side of a 30a field, 10m and 40m from the upstream of the waterway, and the height H of each weir was the same for each case. Water was supplied by an orifice, which was located 5m upstream of G1 and G2.

[0040] (Results and Discussion) The discharge coefficient C of the overflow weir calculated from the results of hydraulic experiments was 1.65 for the full-width weir and 2.10 for the compound weir. The discharge coefficient C of a compound weir, which combines the overflow from a square weir with the underflow, is predicted to increase due to the effect of the high flow velocity at the underflow inlet extending upstream of the weir and increasing the velocity head. The overflow weir studied in this study was a full-width weir, but a similar trend is expected.

[0041] The results of the hydraulic calculations are shown in Figure 3. Figure 3 shows the results of calculations using a conventional overflow weir and a composite weir according to one embodiment of the present invention. As shown in graph 1001 in Figure 3, the water level upstream of G1 was highest in Case 1, and decreased in the order of Case 2-1 and Case 2-2 as the underflow opening d increased. The water level upstream of G2 also showed a similar trend. As such, the composite weir not only increases the underflow flow rate as the underflow opening increases, but also exhibits the effect of increasing the flow coefficient C of the overflow weir, improving the flow capacity and suppressing water level rise.

[0042] Because changes in water depth affect the flow rate of water supplied by the orifice, the water supply rates of Out1 and Out2 decreased in the order of Case 1, Case 2-1, and Case 2-2 as the water depth decreased, as shown in graph 1002 in Figure 3. This shows that the composite weir can suppress the rise in water level and reduce the water supply rate.

[0043] From these results, as shown in graph 1003 in Figure 3, the difference in water flow rate between the composite weir and the full-width weir increases with each water supply, reaching 0.002 m downstream of Out2. 3 / s. In this way, since a composite weir can increase the flow rate in the downstream channel compared to a full-width weir, it was shown that an increase in the flow rate in the downstream channel can be expected by installing more composite weirs. [Explanation of symbols]

[0044] 10 Composite weir 20 Water Distribution Gate 30 Water Tap 40 Control device 50 Measuring devices (water level measuring device, flow rate measuring device) 100 Water Management Systems 200 Branch canal 300 Terminal canal

Claims

1. A water management method for controlling the flow rate of a terminal irrigation channel branching off from a branch irrigation channel, using a water management system equipped with a composite weir, a water distribution gate, and a water supply valve, comprising: The water distribution gate is provided at a branch point between the branch irrigation canal and the terminal irrigation canal that branches off from the branch irrigation canal and has a plurality of fields arranged adjacent to each other along the flow direction of the terminal irrigation canal, the composite weir and the hydrant are provided for each of a plurality of fields adjacent to the terminal irrigation channel; the composite weir is provided with a gap between the lower end of the weir plate and the bottom of the terminal irrigation channel, and controls the flow rate in the terminal irrigation channel by both the underflow flowing below the weir plate and the overflow over the upper part of the weir plate; A water management method in which the water supply from the terminal irrigation canal to the field is controlled by simply controlling the opening and closing of the water distribution gate while the water supply tap is in an open state and the weir height of the composite weir, which controls the flow rate in the terminal irrigation canal by both the underflow and the overflow, is fixed.

2. The water management method according to claim 1, wherein the opening and closing of the water distribution gate is controlled based on at least one of the water level in a field adjacent to the terminal irrigation canal and the water level and flow rate in the terminal irrigation canal.

3. A water management system that controls the flow rate of a terminal irrigation channel branched from a branch irrigation channel, The system comprises a composite weir, a distribution gate, and a water supply valve, The water distribution gate is provided at a branch point between the branch irrigation canal and the terminal irrigation canal that branches off from the branch irrigation canal and has a plurality of fields arranged adjacent to each other along the flow direction of the terminal irrigation canal, the composite weir and the hydrant are provided for each of a plurality of fields adjacent to the terminal irrigation channel; the composite weir is provided with a gap between the lower end of the weir plate and the bottom of the terminal irrigation channel, and controls the flow rate in the terminal irrigation channel by both the underflow flowing below the weir plate and the overflow over the upper part of the weir plate; The water supply from the terminal irrigation channel to the field is controlled by simply controlling the opening and closing of the water distribution gate while the water supply valve is open and the weir height of the composite weir, which controls the flow rate in the terminal irrigation channel by both the underflow and the overflow, is fixed. Water management system.

4. A water level measuring device for measuring the water level in a field adjacent to the terminal irrigation canal, and at least one of a water level measuring device for measuring the water level in the terminal irrigation canal and a flow rate measuring device for measuring the flow rate; a control device that controls the opening and closing of the water distribution gate based on at least one of the water level in a field adjacent to the terminal irrigation canal and the water level and flow rate in the terminal irrigation canal; The water management system of claim 3 further comprising:

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