JP2001295252A - Method of controlling field underground water level - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of controlling the underground water level of a field for cultivating the crops, to the predetermined water level so as to be horizontal over the whole field. SOLUTION: The underground of a boundary part of the field 1 is surrounded by a water-barrier curtain 2 made of soft synthetic resin, vertically to the ground along a ridge 8, and the tip part of a culvert near a drainage canal 6 is provided with a drainage water level regulating gate 5 to control the underground water level of the field 1. The underground water level in the field 1 is maintained to the water level set by a covering cylinder 9 of the water level regulating gate 5, by a combination of the water-barrier curtain 2 and water level regulating gate 5. Moreover, the water level of the whole field 1 is maintained to be horizontal. In the case of draining from an upper overflow port 7 by lowering a drainage cylinder 8 of the water level regulating gate 5 to close a side cock, the supply of air to marl from a drainage hole 11 through the culvert is avoided. Since the underground water level on the drainage canal 6 side is not lowered, there is no supply of excessive air from the upper side, and air supply from the underground through the culvert is cut off, so that the decomposition of the marl on the drainage canal 6 side does not particularly advance, nor does the ground above subside to cause the inclination of a field surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field groundwater level control method for controlling a groundwater level in a field where agricultural crops are cultivated so as to be at a predetermined water level and to be horizontal over the entire field.

[0002]

2. Description of the Related Art A culvert drainage pipe is buried at a constant interval and a constant depth in a field, and switching between drainage and flooding (in the case of paddy fields) is performed by opening and closing a water tank (water stopcock) provided at a tip portion of the culvert pipe. I was going.

[0003]

In the conventional culvert drainage,
As is clear from the graph of the temporal change of the groundwater level shown in FIG. 7, there is a problem that the groundwater level in the vicinity of the drainage channel actually decreases, and the groundwater level becomes harder to decrease as the distance from the drainage channel increases. In addition, the standard drainage amount of the culvert in the paddy field is 20 to 50 mm per day.

[0004] This effect is particularly acute in peat fields. That is, on the drainage channel side, air enters the underground with a drop in the groundwater level, and the decomposition of peat proceeds. As a result, the land on the drainage channel side sinks, and the rice field slopes. If the soil is moved from the opposite side to the drainage channel side and leveled to correct the slope, the thickness of the mineral soil that is uniformly deposited on the peat is uneven. In fact, on the opposite side of the peat field where repeated cropping has been repeated, the necessary results of the required soil thickness are beginning to be lacking ("Basic test for horizontal control of groundwater level in the field" by Yoshiyuki Nakayama and Yoshihiro Ota, Proceedings of the 48th Annual Meeting of the Hokkaido Branch of the Japan Society of Agricultural Engineering, p.60-63,19
Described on October 13, 1999).

[0005]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and in order to achieve this object, the ground is placed under the field boundary, along the ridge. And a water-blocking curtain made of a soft synthetic resin is laid vertically, and a drainage level control water tank is provided at the tip of the culvert near the drainage channel to control the groundwater level in the field.

[0006]

[Function] By combining the impermeable curtain and the underground water level control device (discharge water level control inflator), the underground water level in the field is maintained horizontally at the water level set by the covering cylinder. When the drainage cylinder is lowered to close the horizontal plug and drain the water from the upper overflow port, the supply of air from the drainage port to the peat through the culvert is avoided.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be specifically described below with reference to the accompanying drawings and graphs.

In the present invention, the following findings have been obtained. First, the cause of the inclination of the groundwater level in the field was confirmed by an earth tank experiment (see FIGS. 1 and 2). (1) In the vicinity of the drainage channel, groundwater in the field permeates and flows out from the wall surface of the drainage channel, and the groundwater level drops. (2) There is a portion with a high groundwater level outside the field, and when water permeates and flows in from there, the groundwater level in the vicinity increases. For example, when rainwater falling on the land further outside the levee on the opposite side of the drainage channel infiltrates into the field, the groundwater level temporarily rises. Also, when the land is constantly flooded with paddy fields and reservoirs, the groundwater level is always high.

(3) The inclination of the groundwater in the field caused by the above (1) and (2) cannot be eliminated by ordinary drainage of the underdrain (see FIG. 1). (4) However, if infiltration between the drainage channel side and the opposite side is prevented, the groundwater level becomes horizontal over the entire field (see FIG. 2). (5) If the height of the culvert drain is raised or lowered in this state, the groundwater level rises and falls accordingly.

[0010] Based on the findings from the above experiments and investigations,
The above-mentioned conventional problems (problems) have been solved by arranging a soft synthetic resin impermeable curtain perpendicular to the ground under the boundary of the field and providing a drainage level control indentation at the tip of the culvert.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 85cm in width and 0.2 in thickness in the field 1
As shown in FIG. 3 and FIG. 5, a polyethylene (soft film) water-impermeable curtain 2 having a thickness of 2 mm was buried vertically along the ridge 3 on the ground. 2. At the end of the culvert drain pipe 4 shown in FIG. As shown in FIG. 4, the water level control water shell 5 is composed of a drainage cylinder 8 having a plurality of overflow ports 7 arranged vertically and an overflow port covering cylinder 9 moving up and down along the cylinder 8. The lower end of the cylinder 8 also serves as a horizontal plug for the culvert 4. The drainage cylinder 8 and the overflow port covering cylinder 9 are provided with a drainage cylinder operation rod 8a and a covering cylinder operation rod 9a projecting above the ground, respectively, so that the drainage cylinder 8 and the overflow port covering cylinder 9 can be adjusted up and down. In FIG. 5, reference numeral 10 denotes an agricultural road.

When the drainage cylinder 8 is raised by the drainage cylinder operating rod 8a and the culvert pipe 4 is opened, water coming from the culvert is discharged to the drainage port 1
1 directly to the drainage channel 6. When the drain cylinder 8 is lowered by the drain cylinder operating rod 8a to stop the flow in the horizontal direction, and the covering cylinder 9 is moved up and down by the covering cylinder operating rod 9a to expose any of the plurality of overflow ports 7, water is discharged. The water flows into the drainage cylinder 8 from the overflow port 7 and flows to the drainage port 11. As described above, the groundwater level can be controlled by moving the covering cylinder 9 up and down. Further, when the covering cylinder 9 is raised to the upper end while the drain cylinder 8 is lowered to stop the horizontal flow, the drain port 11
No more water.

As shown in FIG. 5, in a field 1 in which a groundwater level is controllable by combining a water shield 2 and a groundwater level control device (water level adjusting water tank 5), the groundwater level in the field 1 is covered by a covered cylinder. It is maintained horizontally at the water level (here, 30 cm) set in 9 (see FIGS. 4 and 6A). Further, when the drainage cylinder 8 is lowered to close the horizontal plug and drain the water from the upper overflow port 7, the supply of air from the drainage port 11 to the peat through the culvert is avoided. Since the groundwater level on the drainage channel 6 side does not decrease, there is no air entry from above, and there is no air supply through the underdrain, so that the decomposition of peat on the drainage channel 6 side does not particularly proceed relatively. Therefore, the land on the drainage channel 6 side does not sink and the rice field does not tilt.

As described above, according to the field groundwater level control method of the present invention, a watertight curtain made of a soft synthetic resin is wrapped vertically along the ridge along the levee under the field boundary, so as to be in the vicinity of the drainage channel. The underwater drainage control water tank is provided at the tip of the underdrain to control the groundwater level in the field, so that the following effects can be obtained.

[0015]

The groundwater level in the field can be maintained at the water level set by the covering cylinder of the water level adjusting water shell by combining the water shielding curtain and the water level adjusting water shell. Moreover, the water level of the entire field can be maintained horizontal. In addition, when the drainage cylinder of the water level control tank is lowered to close the horizontal plug and drain the water from the upper overflow port, the supply of air from the drainage port to the peat through the culvert is avoided. Since there is no air supply from above due to a local drop in the groundwater level on the drainage side, and no air supply from underground via culverts, the decomposition of peat on the drainage side progresses and the land above it sinks. In addition, it is possible to prevent a situation where the rice field is inclined.

[Brief description of the drawings]

FIG. 1 is a graph showing a groundwater table at a constant infiltration and leaching water level in an experimental soil tank.

FIG. 2 is a graph showing the shape of a groundwater table at the time of preventing infiltration and leaching in an experimental soil tank.

FIG. 3 is a longitudinal sectional view showing a state in which a water impervious curtain is buried in a field to prevent horizontal penetration of groundwater.

FIG. 4 is a vertical cross-sectional view in which a drainage level control inflator is provided at a tip portion of a culvert.

FIG. 5 is a plan view showing an arrangement of a water shielding curtain for preventing horizontal penetration of a groundwater level in a field, and an installation position of a water level adjusting water shell.

6 (a) and 6 (b) are graphs showing control plots showing changes in groundwater levels of a crop field due to a water shielding curtain and a water level control tanker according to the present invention.

FIG. 7 is a graph showing a temporal change of a groundwater level in a conventional field.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Field 2 Waterproof curtain (polyethylene film) 3 Levees 4 Underdrainage drainage pipe 5 Water level control water tank 6 Drainage channel 7 Multiple overflow ports 8 Drain cylinder 8a Drain cylinder operation rod 9 Overflow port cover cylinder 9a Coated cylinder operation rod 10 Farm road 11 drainage outlet

Claims (1)

[Claims] Claims: 1. A drainage curtain made of a soft synthetic resin is wrapped vertically along the ridge along the ridge, under the basement of a field boundary, and a drainage level control indentation is provided at a tip portion of a culvert near a drainage channel. A method for controlling a groundwater level in a field, wherein the groundwater level in the field is controlled.