WO2024177518A1

WO2024177518A1 - Subsurface irrigation system

Info

Publication number: WO2024177518A1
Application number: PCT/NZ2024/050021
Authority: WO
Inventors: Peter Christopher GEARING
Original assignee: Individual
Current assignee: Individual
Priority date: 2023-02-24
Filing date: 2024-02-23
Publication date: 2024-08-29
Anticipated expiration: 2025-08-24
Also published as: AU2024225208B2; AU2024225208A1; NZ819225A

Abstract

A subsurface irrigation and drainage system (100) has one or more elongate conduits (200) for conducting irrigation and drainage liquids, each conduit comprising first (201) and second (202) conduit ends, and a wall portion (203) defining an internal liquid passage (204) between the conduit ends. The wall portion (203) has a plurality of openings (205) formed therein and arranged to allow the transfer of irrigation liquid from the internal liquid passage (204) to the subsurface and the transfer of drainage liquid from the subsurface to the internal liquid passage. The system (100) has a plurality of emitter units (206), an irrigation liquid supply valve (400), a pressurised irrigation liquid source (300), and a drainage pipeline (500). Each emitter unit (206) is associated with at least one opening (205) and configured to control the rate at which the irrigation liquid is emitted into the subsurface.

Description

SUBSURFACE IRRIGATION SYSTEM

This application claims priority from Australian patent applications 2023900484 and 2023903306, the entire contents of which are incorporated herein by way of reference.

FIELD OF THE INVENTION

This invention relates to a subsurface irrigation and drainage system and, in particular, to a combined subsurface drip irrigation and drainage system.

BACKGROUND

Subsurface irrigation can save a substantial amount of water compared with aboveground irrigation where water is lost due to evaporation and runoff. Additionally, because the water used in subsurface irrigation does not contact humans, pets or livestock and does not contaminate runoff from rainfall or sprays, wastewater can be used instead of potable water. However, the high bacterial and organic content of wastewater can enhance algae or bacterial slime growth that clogs or blocks irrigation components.

The use of subsurface drip irrigation is an efficient method to apply water below the soil surface because small precise amounts of water are uniformly applied from multiple emission points underground. Such subsurface drip irrigation systems carry the water into the irrigation area via buried drip irrigation lines, referred to as driplines, with evenly spaced apart drip emitters to control the water release rate into the subsurface.

Irrigated areas such as parks, sports fields, reserves, golf courses, farms, or dedicated disposal areas often suffer from excess moisture from rainfall. Consequently, a drainage system separate from the irrigation system is typically installed to remove the excess moisture. However, different irrigation and drainage systems are costly due to the size and complexity of the two separate systems.

In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents or such sources of information is not to be construed as an admission that such documents or such sources of information, in any jurisdiction, are prior art or form part of the common general knowledge in the art.

It is an object of at least preferred embodiments of the present invention to provide a subsurface irrigation and drainage system that addresses at least some of the disadvantages of known systems, and/or to at least provide the public with a useful alternative.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the invention, there is provided a subsurface irrigation and drainage system comprising: one or more elongate conduits for conducting irrigation and drainage liquids, each conduit comprising first and second conduit ends, and a wall portion defining an internal liquid passage between the conduit ends, the wall portion having a plurality of longitudinally spaced openings formed therein and arranged to allow the transfer of irrigation liquid from the internal liquid passage to the subsurface and the transfer of drainage liquid from the subsurface to the internal liquid passage; a plurality of emitter units, each emitter unit associated with at least one of the openings and configured to control the rate at which the irrigation liquid is emitted into the subsurface; an irrigation liquid supply valve, a drainage liquid release valve, and an irrigation scour cleaning liquid release valve; a pressurised irrigation liquid source arranged to supply pressurised irrigation liquid to the first end of each conduit when the irrigation liquid supply valve is open; and a drainage pipeline arranged to receive drainage liquid from the second end of each conduit and to release the drainage liquid when the drainage liquid release valve or irrigation scour cleaning liquid release valve is open; wherein the system is operable in a normal irrigation mode, in which the irrigation liquid supply valve is open and the drainage liquid release valve is closed, a drainage mode, in which the irrigation liquid supply valve is closed and the drainage liquid release valve is open, and a scour cleaning irrigation mode, in which the irrigation liquid supply valve is open and the irrigation scour cleaning liquid release valve is open.

In an embodiment, the drainage liquid that is released when the irrigation scour cleaning liquid release valve is open comprises particulates that entered the emitter units from the subsurface during the drainage mode and any other internal organic debris or cleaning reagents.

In an embodiment, the pressurised irrigation liquid supplied during the scour cleaning irrigation mode is non-potable. In accordance with a second aspect of the invention, there is provided a subsurface irrigation and drainage system comprising: one or more elongate conduits for conducting irrigation and drainage liquids, each conduit comprising first and second conduit ends, and a wall portion defining an internal liquid passage between the conduit ends, the wall portion having a plurality of longitudinally spaced openings formed therein and arranged to allow the transfer of irrigation liquid from the internal liquid passage to the subsurface and the transfer of drainage liquid from the subsurface to the internal liquid passage; a plurality of emitter units, each emitter unit associated with at least one of the openings and configured to control the rate at which the irrigation liquid is emitted into the subsurface; an irrigation liquid supply valve; a pressurised irrigation liquid source arranged to supply pressurised irrigation liquid to the first end of each conduit when the irrigation liquid supply valve is open; a drainage pipeline arranged to receive drainage liquid from the second end of each conduit; and a supplemental irrigation device positioned on or above a soil surface or positioned shallower in the subsurface than the one or more conduits of the system; wherein the system is operable in a normal irrigation mode, in which the irrigation liquid supply valve is open, and a drainage mode, in which the irrigation liquid supply valve is closed.

In an embodiment, at least one emitter unit comprises a body, at least one conduit- adjacent aperture, at least one subsurface-adjacent aperture, and a labyrinthine channel for conveying liquid between the apertures while generating turbulence in the liquid such that the pressure of the liquid is reduced, the conduit-adjacent aperture being configured to allow irrigation liquid to pass from the conduit into the body and drainage liquid to pass from the body into the conduit, the subsurface-adjacent aperture being configured to allow drainage liquid to pass from the subsurface into the conduit and irrigation liquid to pass from the conduit into the subsurface.

In accordance with a third aspect of the invention, there is provided a subsurface irrigation and drainage system comprising: one or more elongate conduits for conducting irrigation and drainage liquids, each conduit comprising first and second conduit ends, and a wall portion defining an internal liquid passage between the conduit ends, the wall portion having a plurality of longitudinally spaced openings formed therein and aligned at least substantially along a common plane to allow the transfer of irrigation liquid from the internal liquid passage to the subsurface and the transfer of drainage liquid from the subsurface to the internal liquid passage; a plurality of emitter units, each emitter unit associated with at least one of the openings and configured to control the rate at which the irrigation liquid is emitted into the subsurface, each emitter unit comprising a body with a plurality of conduit-adjacent apertures in fluid communication with a plurality of subsurface-adjacent apertures, the conduit-adjacent apertures configured to allow irrigation liquid to pass from the conduit into the body and drainage liquid to pass from the body into the conduit, the subsurface-adjacent apertures configured to allow drainage liquid to pass from the subsurface into the conduit and irrigation liquid to pass from the conduit into the subsurface; an irrigation liquid supply valve; a pressurised irrigation liquid source arranged to supply pressurised irrigation liquid to the first end of each conduit when the irrigation liquid supply valve is open; and a drainage pipeline arranged to receive drainage liquid from the second end of each conduit; wherein the system is operable in a normal irrigation mode, in which the irrigation liquid supply valve is open, and a drainage mode, in which the irrigation liquid supply valve is closed.

In an embodiment, the system includes a drainage liquid release valve, and the drainage pipeline is arranged to release the drainage liquid when the drainage liquid release valve is open, and wherein the drainage liquid release valve is closed in the normal irrigation mode and open in the drainage mode.

In an embodiment, the drainage liquid release valve is motorised.

In an embodiment, the system includes an irrigation scour cleaning liquid release valve, and the drainage pipeline is arranged to release the drainage liquid when the irrigation scour cleaning liquid release valve is open, and wherein the system is operable in a scour cleaning irrigation mode, in which the irrigation liquid supply valve is open and the irrigation scour cleaning liquid release valve is open.

In an embodiment, at least one of the emitter units is a semi-pressure compensating emitter.

In an embodiment, at least one emitter unit contains a filter element with a plurality of pores, the pores being sized and shaped to allow soil particulates in the drainage liquid to pass through the pores but prevent debris in the irrigation liquid from passing through the pores.

In an embodiment, the filter element is in the conduit-adjacent aperture(s).

In an embodiment, at least one emitter unit has at least two spaced-apart subsurface- adjacent apertures aligned along a common plane. In an embodiment, at least one conduit-adjacent aperture is also aligned with the subsurface-adjacent apertures along the common plane.

In an embodiment, the body of the emitter unit(s) is substantially flat and sized to be accommodated within the internal liquid passage of a conduit.

In an embodiment, an inlet manifold is connected to the first end of at least two of the conduits and an outlet manifold is connected to the second end of at least two of the conduits.

In an embodiment, the system provides one or more subsurface irrigation and drainage zones, each zone comprising a plurality of conduits between an inlet manifold and an outlet manifold as well as an irrigation liquid supply valve.

In an embodiment, there are two or more subsurface irrigation and drainage zones and each zone includes a one-way valve between the outlet manifold and the drainage pipeline.

In an embodiment, there are two or more subsurface irrigation and drainage zones and each zone includes a control valve between the outlet manifold and the drainage pipeline.

In an embodiment, the control valve is motorised.

In an embodiment, the drainage pipeline is bifurcated into two drainage branch pipes in which one drainage branch pipe is connected to a or the drainage liquid release valve, while the other drainage branch pipe is connected to a or the irrigation scour cleaning liquid release valve.

In an embodiment, the irrigation liquid comprises non-potable water, such as stormwater, wastewater, or non-tertiary treated effluent.

In an embodiment, the irrigation liquid comprises potable water.

In an embodiment, the system includes a collection zone to collect the drainage liquid from a or the drainage liquid release valve and the collected drainage liquid is reused as at least a portion of the irrigation liquid. In an embodiment, the system includes a collection zone to collect the drainage liquid from a or the drainage liquid release valve and the collected drainage liquid is released from the system by gravity, suction pump, or lift pump.

In an embodiment, the system does not include a drainage collection zone and the drainage liquid is released from the system to the environment through a or the drainage release valve.

In an embodiment, the drainage pipeline is downwardly angled and/or uses suction to receive drainage liquid from the second end of each conduit.

In an embodiment, the system includes one or more gas introduction ports to introduce gas into at least one of the conduits for aeration of the subsurface.

In an embodiment, the system includes a or the supplemental irrigation device, wherein the supplemental irrigation device is a surface irrigation device or a relatively shallow subsurface irrigation device.

In accordance with a fourth aspect of the invention, there is provided a method of subsurface irrigation and/or drainage, the method comprising the use of the subsurface irrigation and drainage system as outlined in relation to the first, second or third aspects above.

In an embodiment, the method comprises operating the subsurface irrigation and drainage system in a drainage mode.

In an embodiment, the method comprises operating the subsurface irrigation and drainage system in an irrigation mode.

In an embodiment, the irrigation mode is the normal irrigation mode.

In an embodiment, the irrigation mode is the scour cleaning irrigation mode.

In an embodiment, the method comprises simultaneously operating one or more subsurface irrigation and drainage zones in the irrigation mode and one or more subsurface irrigation and drainage zones in the drainage mode. In an embodiment, the method comprises operating the subsurface irrigation and drainage system in an aeration mode.

In an embodiment, the subsurface irrigation and drainage system is installed on a slope.

In an embodiment, the subsurface irrigation and drainage system is installed on a convex irrigation area.

In an embodiment, the method comprises collecting the drainage liquid and reusing the drainage liquid as at least a portion of the irrigation liquid in the subsurface irrigation and drainage system.

The term 'comprising' as used in this specification and claims means 'consisting at least in part of'. When interpreting statements in this specification and claims which include the term 'comprising', other features besides the features prefaced by this term in each statement can also be present. Related terms such as 'comprise' and 'comprised' are to be interpreted in a similar manner.

The term 'subsurface' as used herein refers to any geological material below the ground surface and may comprise soil, sand, silt, clay, loam, gravel, stone, rock, compost, biochar, organic material, and the like.

The term 'subsurface irrigation and drainage system' as used herein refers to an irrigation system where the openings and emitter units are buried in, or are configured to be buried in, the subsurface.

The term 'subsurface irrigation and drainage zone' as used herein refers to a portion of a subsurface irrigation and drainage system comprising a plurality of conduits between an inlet manifold and an outlet manifold as well as an irrigation liquid supply valve.

The irrigation liquid and/or drainage liquid may comprise wastewater, treated effluent, stormwater, stream water, river water, lake water, pond water, or potable water. In an embodiment, the irrigation liquid comprises wastewater. In another embodiment, the irrigation liquid comprises agricultural effluent.

It is intended that reference to a range of numbers disclosed herein (for example, 1 to 10) also incorporates reference to all rational numbers within that range (for example, 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9 and 10) and also any range of rational numbers within that range (for example, 2 to 8, 1.5 to 5.5 and 3.1 to 4.7) and, therefore, all sub-ranges of all ranges expressly disclosed herein are hereby expressly disclosed. These are only examples of what is specifically intended and all possible combinations of numerical values between the lowest value and the highest value enumerated are to be considered to be expressly stated in this application in a similar manner.

This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more said parts, elements or features.

To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting. Where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

As used herein the term '(s)' following a noun means the plural and/or singular form of that noun. As used herein the term 'and/or' means 'and' or 'or', or where the context allows both.

The invention consists in the foregoing and also envisages constructions of which the following gives examples only.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described by way of example only and with reference to the accompanying drawings in which:

Figure 1 shows a schematic view of an embodiment of a subsurface irrigation and drainage system having one combined irrigation and drainage zone;

Figure 2 shows a schematic view of a first embodiment of a subsurface irrigation and drainage system having two combined irrigation and drainage zones;

Figure 3 shows a schematic cross-sectional view of the embodiment shown in Figure 2; Figure 4 shows a schematic view of a second embodiment of a subsurface irrigation and drainage system having two combined irrigation and drainage zones including a drainage collection zone; Figure 5 shows a perspective view of a conduit for conducting irrigation and drainage liquids;

Figure 6 shows a perspective view of a portion of the conduit containing a flat in-pipe emitter unit (with a cut-through section showing the emitter unit within the tube); Figure 7 shows a cross-sectional view of the conduit shown in Figure 6;

Figure 8 shows a schematic view of an embodiment of a subsurface irrigation and drainage system having four combined irrigation and drainage zones for use on a convex irrigation area, and also shows the drainage collection liquid being able to be repumped back into the irrigation;

Figure 9 shows a cross-sectional view of the embodiment shown in Figure 8;

Figure 10 shows a schematic cross-sectional view of an embodiment of a subsurface irrigation and drainage system having a supplemental irrigation system according to a first embodiment;

Figure 11 shows a schematic cross-sectional view of an embodiment of a subsurface irrigation and drainage system having a supplemental irrigation system according to a second embodiment; and

Figure 12 shows schematic cross-sectional view showing a conduit of a subsurface irrigation and drainage system in the subsurface.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Figures 1 to 4 show embodiments of a subsurface irrigation and drainage system 100 for the subsurface irrigation and drainage of an area of land such as a park, reserve, garden, farm, orchard, sports field, racetrack, golf course, plantation, forest or the like. The subsurface irrigation and drainage system 100 has one or more conduits 200 buried, or at least partially buried, in the subsurface for conducting irrigation and drainage liquids, a pressurised irrigation liquid source 300 arranged to supply pressurised irrigation liquid to the conduit(s) when an irrigation liquid supply valve 400 is open, and a drainage pipeline 500 to receive drainage liquid from the conduit(s) and release the drainage liquid from the subsurface irrigation and drainage system 100 when a drainage liquid release valve 600 is open. The system is operable in a normal irrigation mode, in which the irrigation liquid supply valve 400 is open and the drainage liquid release valve 600 is closed, and a drainage mode, in which the irrigation liquid supply valve is closed and the drainage liquid release valve is open.

As shown in Figure 3, in the embodiments shown, the drainage pipeline 500 is downwardly angled relative to the conduit(s) 200 so that the drainage liquid flows out of the conduit(s) under the influence of gravity. The fall or percent of slope may be in the order of accepted drainage gradients, for example 1-2% fall or substantially less. In another embodiment, a suction drainage pipeline is used to draw the drainage liquid from the conduit(s) 200 using suction. The suction could be used in addition to, or instead of, the downward angle of the drainage pipeline.

The pressurised irrigation liquid source 300 may comprise a pump, piston, or other suitable device or source (such as town water supply, or other) to pressurise the irrigation liquid. The two valves 400 and 600 may be shutoff valves, such as ball or butterfly valves or remotely pressure-controlled irrigation-type diaphragm valves. Alternatively, the valves 400 and 600 may be any other suitable valves that allow the control of liquid flow through the valves. For example, if the drainage liquid release valve 600 needs to open with very low pressure to allow drainage to occur, this valve may need to be motor operated or externally driven rather than be driven by water pressure.

While five conduits 200 are shown in Figure 1 and ten conduits 200 are shown in Figures 2 and 4, it will be appreciated that, depending upon the size of the land area to be irrigated and drained, the subsurface irrigation and drainage system 100 may have as few as one conduit and no limit on the maximum number of conduits. It will also be appreciated that the subsurface irrigation and drainage system 100 can be used in a method of subsurface irrigation and drainage.

Figure 5 is a view of one of the conduits 200 buried in a subsurface irrigation field. Each conduit 200 is elongated with first 201 and second 202 conduit ends, and a wall portion 203 (refer Figure 6) defining an internal liquid passage 204 between the conduit ends. The wall portion 203 has opposed inner and outer surfaces.

In one embodiment, the wall portion 203 comprises a hollow cylindrical tube of substantially uniform external diameter typically between 12 to 32 mm, optionally 12 to 20 mm, including a wall thickness of between 0.1 to 1.3 mm. However, it will be appreciated that the diameter could be smaller or larger than this range, and the wall thickness could be greater or thinner.

The wall portion 203 may be formed of plastic, such as a flexible thermoplastic polymer like polyethylene for example. The first end 201 of the conduit 200 is connected, either directly or indirectly, to the pressurised irrigation liquid source 300. The second end 202 of the conduit 200 is connected, either directly or indirectly, to the drainage pipeline 500.

The wall portion 203 has a plurality of longitudinally spaced openings 205 formed therein. The openings 205 may be evenly spaced apart or may alternatively have varying spacings for applications where greater irrigation is required in some regions than other regions. The openings 205 are arranged to transfer irrigation liquid from the internal liquid passage 204 to the surrounding subsurface as well as the transfer of drainage liquid from the subsurface into the internal liquid passage.

To maximise the volume of the internal liquid passage 204, the openings 205 are aligned along, or at least substantially along, a common plane. This prevents drainage liquid from entering the internal liquid passage 204 from the subsurface through some openings 205 and, if the subsurface is not saturated, leaving the internal liquid passage to re-enter the subsurface through other openings. For example, if the openings 205 are circumferentially spaced apart by 180 degrees (i.e., parallel to the ground surface) rather than being substantially in the same vertical plane then the conduit(s) can only be half-filled with drainage liquid, greatly reducing the drainage efficiency.

Preferably the openings 205 are circumferentially spaced apart by 0 to 90 degrees, more preferably by 0 to 45 degrees, and most preferably by zero degrees (i.e., facing vertically upward to the ground surface).

Associated with at least one opening 205 is an emitter unit 206 configured to control the rate at which the irrigation liquid is emitted into the subsurface, such as typically between a nominal 0.5 to 8 litres per hour for example. In the exemplified embodiment, the emitter unit 206 is a drip emitter or dripper for providing subsurface drip irrigation and drainage.

As shown in Figure 6 and Figure 7, the emitter unit 206 comprises a body 206a, at least one conduit-adjacent aperture 206b, at least one subsurface-adjacent aperture 206c, and a labyrinthine channel 206d for conveying liquid between the apertures while generating turbulence in the liquid such that the pressure of the liquid is reduced. The labyrinthine channel 206d can be zig-zagged, serpentine or any other tortuous shape. The conduit-adjacent aperture(s) 206b are open to the internal liquid passage 204 of the conduit 200 and are configured to allow irrigation liquid to pass from the conduit into the body 206a and drainage liquid to pass from the body into the conduit. The subsurface- adjacent aperture(s) 206c are configured to allow drainage liquid to pass from the subsurface into the conduit and irrigation liquid to pass from the conduit into the subsurface. The conduit-adjacent aperture(s) 206b and the subsurface-adjacent aperture(s) 206c are in fluid communication with each other through the body 206a. Once the irrigation liquid has passed into the subsurface, the irrigation liquid will move away from each emitter unit 206 by capillary action to spread the irrigation liquid into the subsurface.

Each emitter unit 206 advantageously includes a filter element with a plurality of pores, the pores being sized and shaped to allow soil particulates in the drainage liquid to pass through the pores but prevent debris in the irrigation liquid from passing through the pores. The pores may be any suitable shape, for example circular holes or rectangular slots, with either parallel or tapered cross section. The filter element can be located in any suitable location in the emitter unit 206. Preferably, the filter element is located in the conduit-adjacent aperture(s) 206b to prevent the emitter unit 206 from becoming clogged or blocked with debris in the irrigation liquid. The soil particulates in the drainage liquid enter the conduit through the pores in the filter, where they can be flushed out of the conduit by the scour cleaning procedure discussed below to maintain the performance of the emitter units 206.

The rate at which the irrigation liquid is emitted from a subsurface-adjacent aperture 206c into the subsurface may be variable or constant. In one embodiment, the emission rate is variable and proportional to the pressure in the conduit 200. This emitter unit 206 is referred to in the art as a 'semi-pressure compensating' or 'turbulent flow' type. In another embodiment, the emitter unit 206 includes a pressure-regulating diaphragm to provide a constant emission rate for a particular pressure range. This emitter unit is referred to in the art as a 'fully pressure compensating' type. Semi-pressure compensating emitters may be advantageous when the irrigation liquid is non-potable as the absence of a diaphragm prevents particulates from being caught under the diaphragm, potentially degrading system performance.

An emitter unit 206 may be mounted on the outer surface of the wall portion 203 of the conduit(s) 200, i.e., an 'on-pipe' emitter. Alternatively, an emitter unit 206 may be mounted on the inner surface of the wall portion 203, in the wall portion, or within the internal liquid passage 204 of the conduit(s) 200, i.e., an 'in-pipe' emitter. In-pipe emitter units are likely to be installed at the time of manufacture of the conduit(s). However, on-pipe emitter units may be retrospectively installed on existing conduit(s). In one embodiment, the in-pipe emitter unit has a cylindrical body sized to snugly fit within the internal liquid passage 204 of a conduit 200 such that contact is made between the body and the inner surface of the conduit 200 around the entire circumference of the body. This type of in-pipe emitter unit is referred to in the art as a 'round' drip emitter or dripper. Examples of commercially available round in-pipe emitters include, but are not limited to, ADI drippers from Metzerplas (fully pressure compensating) and IDIT or SUPER COMPACT drippers from Metzerplas (semi-pressure compensating).

As shown in Figure 6 and Figure 7, in another embodiment, the in-pipe emitter unit has a substantially flat, tablet-shaped, or boat-shaped body sized to be easily accommodated within the internal liquid passage 204 of a conduit 200 and contacts only a portion of the cross-sectional inner surface of the conduit. This type of in-pipe emitter unit is referred to in the art as a 'flat' drip emitter or dripper. Examples of commercially available flat in-pipe emitter units include, but are not limited to, VERED or VARDIT series (including for example VARDIT, INBAR and ASSIF) drippers from Metzerplas (fully pressure compensating) and LIN, MINILIN or MICROLIN drippers from Metzerplas (semi-pressure compensating). Unlike round in-pipe emitter units customised to fit conduits with a particular diameter, flat in-pipe emitter units can be mounted within conduits with various diameters.

Commercially available flat emitters typically only have one subsurface-adjacent aperture 206c, limiting the rate at which irrigation liquid can be emitted into the subsurface. In contrast, commercially available round emitters normally have two subsurface-adjacent apertures 206c. However, these two subsurface-adjacent apertures 206c are typically located at the same end of the emitter body and on opposing faces. As a result, drainage liquid that enters the emitter body through an upper subsurface- adjacent aperture can leave the emitter body through a lower subsurface-adjacent aperture.

Advantageously, as shown in Figure 6, a flat emitter unit 206 will have, or could have been modified to include, at least two spaced-apart subsurface-adjacent apertures 206c. These subsurface-adjacent apertures 206c (or the subsurface-adjacent apertures on any type of emitter unit, whether round, flat, fully pressure compensating or semi-pressure compensating) are spaced-apart as much as possible in the emitter unit body 206a and aligned along or at least substantially along a common plane so that, when the emitter unit is installed in a conduit, all the subsurface-adjacent apertures face the same direction, namely vertically upwards. The conduit-adjacent aperture(s) 206b may also be located along the same plane or at least substantially along the same plane.

The conduit(s) 200 will typically be buried in the subsurface at depths of between 10 to 50 cm below ground surface. For example, the conduit(s) 200 may be buried at depths of between 10 to 50 cm to irrigate plants or crops with shallow root systems such as turf grass. The conduit(s) 200 will usually be buried such that the entire conduit(s) is situated in the subsurface. However, the conduit(s) 200 could be partially buried in the subsurface, for example, with at least a substantial portion of the conduit(s) situated in the subsurface and one or more portions of the conduit(s) located on or above the ground surface or otherwise not exposed to the subsurface. In this embodiment, the substantial portion of the conduit(s) 200 situated in the subsurface comprises the openings 205 and the emitter units 206 to facilitate the subsurface irrigation and drainage.

To create a gradient to assist with drainage and irrigation liquid flow through the conduit(s) 200, the conduit(s) may be downwardly angled from the first end 201 to the second end 202. This downward angle may be substantially less than the downward angle of the drainage pipeline 500 relative to the conduit(s). In one embodiment, the conduit(s) 200 are buried or partially buried in the subsurface such that the first end 201 of the conduit is located slightly closer to the ground surface, or less deep in the subsurface, than the second end 202 of the conduit. The fall or percent of slope may be in the order of drainage gradients, for example 1-2% fall, or substantially less, in order to allow for both effective irrigation and drainage.

In embodiments having more than one conduit 200, the subsurface irrigation and drainage system 100 preferably includes an inlet manifold 700a connected to the first end 201 of at least two conduits 200 and an outlet manifold 700b connected to the second end 202 of at least two conduits 200.

The inlet manifold 700a is interposed between the first end 201 of the conduits 200 and the pressurised irrigation liquid source 300. In contrast, the outlet manifold 700b is interposed between the second end 202 of the conduits and the drainage pipeline 500. The inlet and outlet manifolds 700a, 700b conveniently provide a single connection point between the conduits 200 and the pressurised irrigation liquid source 300 as well as between the conduits and the drainage pipeline 500. Unlike the subsurface irrigation and drainage system 100 shown in Figure 1 which has a single irrigation and drainage zone, the embodiments shown in Figures 2 and 4 have two spaced-apart irrigation and drainage zones. Multiple irrigation and drainage zones can be beneficial in reducing erosion and runoff where the terrain to be irrigated and drained comprises at least one slope or for larger irrigation areas where multiple zones are required. The amount of irrigation liquid supplied to the conduits in each zone, as well as the number and spacing of the conduits in each zone, can be independently adjusted depending on the zone's location on the slope.

Each irrigation and drainage zone comprises a plurality of conduits 200 between an inlet manifold 700a and an outlet manifold 700b, as well as an irrigation liquid supply valve 400 that, when open, allows pressurised irrigation liquid to enter the first end 201 of the conduits through the inlet manifold. Because each irrigation and drainage zone has its own irrigation liquid supply valve 400, the amount of irrigation liquid supplied to the conduits 200 in each zone can be independently controlled by opening or closing the corresponding irrigation liquid supply valve.

As shown in Figure 2, where there are two or more irrigation and drainage zones, each zone may also include a one-way valve 900 between the outlet manifold 700b and the drainage pipeline 500. This one-way valve 900 allows liquid to flow into the drainage pipeline 500 but prevents liquid from flowing out from the drainage pipeline back into the outlet manifold 700b. The one-way valve 900 may be a mechanical non-return valve, check valve or any other suitable valve which is spring actuated, or uses a flap to prevent at least significant backflow of liquid from the drainage pipeline 500. Accordingly, each irrigation and drainage zone can use the same drainage pipeline 500 without the irrigation and/or drainage liquid from one irrigation and drainage zone entering the conduits 200 of another irrigation and drainage zone through the drainage pipeline.

In the embodiment shown in Figure 4, the one-way valves 900 are replaced with control valves 1000, such as remotely-controlled pressure driven valves or other control valve types, whether manually, hydraulically or electrically controlled, that can be opened or closed so that one irrigation and drainage zone can be used for irrigation at the same time as another irrigation and drainage zone is used for drainage. The pressure driven control valves 1000 may be automatic irrigation-type diaphragm valves activated by a central controller and a solenoid. The electrically activated solenoid can either be located on the valve itself or connected via a small, pressurised water tube to open and close the valve. Irrespective of the solenoid's location or type, the pressure-controlled valve 1000 opens when water pressure is released from above the diaphragm and closes when water pressure is returned above the diaphragm. Alternatively, these control valves 1000 may be motor driven to ensure that they will open during drainage mode.

In an embodiment, the subsurface irrigation and drainage system 100 includes both oneway valves 900 and control valves 1000, with the control valves advantageously being manually controlled so they can be operated during a power cut. The control valves 1000 will typically be open so that the one-way valves 900 do the work under normal conditions. However, in the event of a power cut, for example during a natural disaster such as a flood, the control valves 1000 can be manually closed as appropriate.

In an embodiment, the subsurface irrigation and irrigation system 100 has an irrigation scour cleaning liquid release valve 800. In this embodiment, the subsurface irrigation and drainage system 100 may optionally have a drainage liquid release valve 600.

Optionally, but advantageously, the drainage pipeline 500 is bifurcated into two drainage branch pipes 501, 502 in which one drainage branch pipe 501 is connected to the drainage liquid release valve 600, while the other drainage branch pipe is connected to the irrigation scour cleaning liquid release valve 800. It will be appreciated that the drainage pipeline 500 could be bifurcated in different ways, for example, using a tee connection on the drainage pipeline. The irrigation scour cleaning liquid release valve 800 may be a shutoff valve, such as, a ball or butterfly valve or a pressure driven irrigation-type diaphragm control valve (or other type). This valve 800 is typically kept closed except when it is opened along with the irrigation liquid supply valve 400 to clean the conduit(s) by flushing the conduit(s) with pressurised irrigation liquid. Periodically scouring the internal liquid passage 204 of the conduit(s) 200 with pressurised irrigation liquid in accordance with the American Society of Agricultural and Biological Engineers (ASABE) flush velocity standards, as opposed to a simple flush, helps to prevent the formation of clogs or blockages in the conduit(s) caused by the accumulation of residue such as soil particulates, bacterial slimes, metal compounds, and other detritus. This residue is flushed out of the subsurface irrigation and drainage system 100 through the irrigation scour cleaning liquid release valve 800. The drainage liquid that is released when the irrigation scour cleaning liquid release valve 800 is open comprises particulates that entered the emitter units 206 from the subsurface during the drainage mode and any other internal organic debris or cleaning reagents.

The subsurface irrigation and drainage system 100 is operable in a drainage mode and two irrigation modes. In the drainage mode, the irrigation liquid supply valve 400 (and the irrigation scour cleaning liquid release valve 800) is closed while the drainage liquid release valve 600 is open. Because the irrigation liquid supply valve 400 is closed, the conduit(s) 200 are isolated from the pressurised irrigation liquid source 300.

Additionally, because the drainage liquid release valve 600 is open, the subsurface irrigation and drainage system 100 operates as a gravity-controlled drainage system. The drainage liquid release valve 600 may be of a normally open type - meaning that when the irrigation is turned off - the whole system 100 is sitting in drainage mode - and this valve only closes when the pump and an irrigation valve is open.

Normal irrigation valves (typically either electrical solenoid or hydraulic activated) require internal line pressure to work or operate. Therefore, with the pump of the pressurised irrigation liquid source 300 activated and operational - the whole irrigation system is pressurised - so under these circumstances there is normally sufficient back pressure for the irrigation scour cleaning liquid release valve 800 to open and close when activated (if a normal irrigation type valve). However, when in drainage mode, there may be negligible pressure in the dual function drip system, so under these circumstances it may be highly likely that a normal irrigation type valve may not even open when activated. For this reason, the drainage liquid release valve 600 may be motorised or externally driven if there is insufficient internal water pressure during the drainage mode to open a normal irrigation type valve.

Accordingly, the irrigation scour cleaning liquid release valve 800 may be a normal irrigation type valve and a different physical type as compared to the drainage liquid release valve 600 (which may be of a motorised or externally opened/closed type).

The system comprises two types of irrigation modes: normal irrigation mode and scour cleaning irrigation mode. In normal irrigation mode, the irrigation liquid supply valve 400 is open and the drainage liquid release valve 600 (and the scour cleaning liquid release valve 800) is closed. Under these conditions the conduit(s) 200 are exposed to the pressurised irrigation liquid source 300 and the subsurface irrigation and drainage system 100 operates as a pressurised irrigation system.

In scour cleaning irrigation mode, the irrigation liquid supply valve 400 and the irrigation scour cleaning liquid release valve 800 are both open, while the drainage liquid release valve 600 is closed. Consequently, the conduit(s) 200 are flushed under pressure with the pressurised irrigation liquid, which may be potable or non-potable. It is safe to use non-potable liquid, even in a public space, because the irrigation occurs below the soil surface. The residue removed from the conduit(s) is evacuated from the subsurface irrigation and drainage system 100 via the irrigation scour cleaning liquid release valve 800.

The contaminated liquid passing through the irrigation scour cleaning liquid release valve 800 may be incompatible with the surrounding environment and may need to be disposed of separately from the drainage liquid that passes through the drainage liquid release valve 600 during the drainage mode. The liquid passing through the irrigation scour cleaning liquid release valve 800 is typically non-potable.

The ability to separate the contaminated liquid released from the irrigation scour cleaning liquid release valve 800 from the liquid released from the drainage liquid release valve 600 is advantageous because the liquid released from the drainage liquid release valve 600 can be reused or released into the environment while the contaminated liquid released from irrigation scour cleaning liquid release valve 800 can be treated or disposed of in a controlled manner.

In an embodiment containing two or more irrigation and drainage zones, with each zone having an irrigation liquid supply valve 400, typically only the irrigation liquid supply valve will be opened at a time to scour clean the conduit(s) 200 of one zone at a time. However, it is possible to scour clean the conduit(s) 200 of multiple irrigation and drainage zones simultaneously by opening multiple irrigation liquid supply valves 400.

In an embodiment, such as that shown in Figure 4, containing two or more irrigation and drainage zones, with each zone having a control valve 1000 in place of the one-way valves 900, the control valve can be closed in the zone(s) operating in irrigation mode and be open in the zone(s) operating in drainage mode. Accordingly, one or more irrigation and drainage zones can be used for irrigation at the same time as other irrigation and drainage zone(s) are used for drainage. The ability to independently control each drainage and irrigation zone is a significant advantage, especially for large areas of land.

Optionally, the subsurface irrigation and drainage system 100 can be operated in an aeration mode in which one or more compressed gasses comprising oxygen, typically air, are pumped through the conduit(s) 200 in place of the irrigation liquid. The ability to supply compressed air or oxygen to the roots of plants can be advantageous, for example, after a flood when the stems and/or leaves of plants are covered with silt and unable to receive oxygen from the above surface environment. Figure 4 shows an embodiment of the subsurface irrigation and drainage system 100 in aeration mode. The pressurised irrigation liquid source 300 is isolated from the pressurised mainline by closing an isolation valve 1100. The drainage liquid release valve 600 is also closed together with any control valves 1000 associated with closed irrigation liquid supply valves 400 and the scour cleaning liquid release valve 800.

In aeration mode, compressed air or other gasses comprising oxygen may be introduced into the pressurised irrigation liquid mainline at a first gas introduction port 1200, such as tee with a manual valve and a gas injection inlet. The irrigation liquid supply valves 400 are opened individually or in any combination to allow the oxygenated gas to enter the conduit(s) 200 of the corresponding irrigation and drainage zone(s). The gas passes through the emitter units within the conduit(s) 200 and is released into the subsurface to aerate the root systems of plants and/or reduce anaerobic soil conditions and/or reduce soil saturation.

If the pump or other device used to pressurise the irrigation liquid is inoperable after a flood, the compressed gas may be introduced into the subsurface drainage and irrigation system 100 at a second gas introduction port 1300, such as opened manual valves. As shown in Figure 4, these manual valves 1300 are interposed between the irrigation liquid supply valves 400 and the corresponding inlet manifolds 700a. The drainage liquid release valve 600 is closed along with any control valves 1000 and the irrigation scour cleaning liquid release valve 800.

When the drainage liquid release valve 600 is open, the drainage liquid may drain to an open discharge system. Alternatively, as shown in Figure 4, the drainage liquid may drain to a collection zone 1400 such as a sump, storage tank or vessel, pond, dam, or reservoir. The ability to collect the drainage liquid in a dedicated collection zone 1400 can be advantageous during periods of heavy rain or flooding. The collected drainage liquid can be removed from the collection zone 1400, for example, by gravity, suction pump (not shown), or lift pump (not shown), and either be drained to waste or reused as, or supplement at least a portion of, the irrigation liquid by being pressurised at the pressurised irrigation liquid source 300. Because the drainage liquid release valve 600 is separate from the irrigation scour cleaning liquid release valve 800, the collected drainage liquid will not contain the residue removed from the conduit(s) 200 when the subsurface irrigation and drainage system 100 is operated in scour cleaning irrigation mode. Accordingly, the conduit(s) 200 will not be clogged or blocked with the removed residue by reusing the drainage liquid as at least a portion of the irrigation liquid. The irrigation and/or drainage liquid can comprise various types of waters, including potable and non-potable water. Typically, the drainage liquid will comprise stormwater produced by rainfall. The irrigation liquid could comprise naturally occurring water such as accumulated stormwater, stream water, river water, lake water, or pond water. However, to conserve potable water and reduce water storage costs, it may be desirable to use non-potable water such as wastewater or non-tertiary treated effluent as the irrigation liquid. For example, agricultural effluent can be used as the irrigation liquid, such as dairy or other farm effluent, as could municipal I domestic wastewater, or effluent.

If non-potable water sources, such as secondary treated effluents or wastewater, are used as the irrigation liquid, it is desirable to incorporate an antibacterial agent into the inner surface of the wall portion 203 of the conduit(s) 200. Doing so will minimise the risk of undesired build-up of bacterial growth and associated slime within the conduit(s) 200.

The antimicrobial agent may be applied to the inner surface of the wall portion 203 of the conduit(s) 200 as discussed in United States Patent No. 8,286,667, issued October 16, 2012, to Rodney Ruskin, the full disclosure of which is incorporated herein by reference. This patent describes dispensing an antibacterial agent on the inner wall of an irrigation conduit to prevent build-up of bacterial growth. Such conduits are available from Geoflow, Inc. under the trade mark WASTEFLOW. The present system may comprise such an antimicrobial agent in the inner wall of the irrigation conduit(s) 200.

The antimicrobial agent used in the inner surface of the wall portion 203 of the conduit(s) 200 of the present system may be of the type disclosed in United States Patent No. 8,286,667 or be a non-arsenic based antimicrobial, for example, tributyltin maleate (TBTM) or zinc pyrithione. Unlike arsenic based products (such as oxybisphenoxarsine, OBPA), TBTM and zinc pyrithione are safe to both the environment and public health, as shown by their use in hypoallergenic and human hygiene products.

The conduit(s) 200 and/or emitter units 206 can be protected against the hazard of root growth intrusion by the application of various growth inhibitors, such as copper or infused chemicals, and including but not limited to Treflan (Trifluralin) or Pendimethalin. One or more root growth inhibitors may be applied to the inner surface of the wall portion 203 of the conduit(s) 200 and/or to the interior of the emitter units 206. Alternatively, the root growth inhibitor(s) may be incorporated into the plastic of the conduit(s) 200 and/or emitter units 206 during manufacture. The root growth inhibitor(s) may be incorporated into these products as discussed in United States Patent No. 6,821,928, issued November 23, 2004, to Rodney Ruskin, the full disclosure of which is incorporated herein by reference. Such drip irrigation products are available from Geoflow, Inc. under the trade marks ROOTGUARD and NANO-ROOTGUARD.

Figure 8 and Figure 9 show an embodiment of a subsurface irrigation and drainage system 100 for a convex irrigation area, such as a sports field. The central region (CR) of the field is higher than the sideline regions (SR). Accordingly, the sloped terrain can prevent ponds of water forming on the field or irrigation area by directing surface runoff to the sideline regions (SR).

Advantageously, as shown in Figure 8, the pressurised irrigation liquid source 300, which includes a pump 301, the irrigation liquid supply valves 400, and the inlet manifolds 700a are in the central region (CR) of the field at the top of the slope. The conduits 200 run down the slope (across the irrigation area) rather than across the slope (along the length of the irrigation area). As a result, the conduits 200 can be at a uniform depth below the ground surface for optimal irrigation whilst also still being downwardly angled from the first end 201 to the second end 202. Drainage liquid can then optionally be collected in a collection zone 1400 downstream from the drainage liquid release valve 600, where it can be collected and reused as at least a portion of the irrigation liquid after being pressurised by the pump 301. The collection zone 1400 can be a sump, storage tank or vessel, pond, dam, or reservoir.

The subsurface irrigation and drainage system 100 may include a controller that is in electrical, radio, or fibre communication with various components of the system, such as the valves. A user interface may be provided to enable a user to program or interact with the controller to control the modes of operation of the system. Alternatively, the valves and modes of operation of the system may be manually controlled.

The subsurface irrigation and drainage systems 100 disclosed herein can be used in a method of subsurface irrigation and/or drainage, the method comprising the use of the subsurface irrigation and drainage system as outlined herein.

In an embodiment, the method comprises operating the subsurface irrigation and drainage system 100 in a drainage mode.

In an embodiment, the method comprises operating the subsurface irrigation and drainage system 100 in an irrigation mode. In an embodiment, the irrigation mode is a normal irrigation mode.

In an embodiment, the irrigation mode is a scour cleaning irrigation mode.

In an embodiment, the method comprises operating the subsurface irrigation and drainage system 100 simultaneously in both an irrigation mode and a drainage mode

In an embodiment, the method comprises operating the subsurface irrigation and drainage system 100 in an aeration mode.

In an embodiment, the subsurface irrigation and drainage system 100 is installed on a slope.

In an embodiment, the subsurface irrigation and drainage system 100 is installed on a convex irrigation area, as shown in Figures 8 and 9 for example.

In an embodiment, the method comprises collecting the drainage liquid and reusing the drainage liquid as at least a portion of the irrigation liquid in the subsurface irrigation and drainage system 100.

The normal irrigation mode, scour cleaning irrigation mode, drainage mode, and aeration mode can be operated separately and alternately. The modes will not be operated concurrently for a single subsurface irrigation and drainage zone. For example, the subsurface irrigation and drainage system 100 may be used alternately in the normal irrigation mode for a first time period and the drainage mode for a second time period, with less frequent usage of the scour cleaning irrigation mode and the aeration mode.

For example, depending upon seasonal requirements, during a wet season or time period the subsurface irrigation and drainage system 100 may be used in the drainage mode for an extended period (for example, one or more days or weeks). Intermittently, the drainage mode may be stopped and the subsurface irrigation and drainage system 100 may be used in the scour cleaning irrigation mode for a suitable time period (such as between one and several minutes for example) before the drainage mode is restarted.

To keep the liquid shallow in the plant root zone, the subsurface irrigation and drainage system 100 will typically be operated in the normal irrigation mode daily or every two to three days. However, less frequent use of the irrigation mode, such as every 4-14 days, can be advantageous. Less frequent use of the normal irrigation mode allows for better lateral spread of the irrigation liquid and may assist avoiding "wetted" green stripes within the grass or crop on the soil surface. It also allows the slow-moving ammonia to adhere to the soil in the cool of winter, be converted to nitrate in the warmth of summer, and be consumed by the plant (and hence removed from the environment at harvest) rather than percolate to groundwater and cause nitrogen pollution of the groundwater. Additionally, where the irrigation liquid is wastewater or non-tertiary treated effluent, less frequent irrigation use gives the plants more time to absorb the irrigation liquid before the next application.

Conveniently, where the subsurface irrigation and drainage system 100 has two or more irrigation and drainage zones and each zone has a control valve 1000 in place of the one-way valve 900, one or more of the irrigation and drainage zones can simultaneously be operated in irrigation mode while the other irrigation and drainage zones are not in use or may be operated in drainage mode. For example, in a subsurface irrigation and drainage system 100 with eight irrigation and drainage zones on an eight-day irrigation rotation, one of the zones will be operated in irrigation mode each day while the other seven zones are either rested or operated in drainage mode in any combination on any given day. This dual-mode operation is especially beneficial when an effluent (either domestic, municipal, manufacturing or agricultural) is used as the irrigation liquid since the effluent will likely be collected daily and need to be used every day throughout the year regardless of the weather and seasonal drainage needs.

Figures 10 and 11 show two embodiments of a subsurface irrigation and drainage system 100. The subsurface irrigation and drainage system 100 of this embodiment is as hereinbefore described in any embodiment. In the illustrated schematic of Figure 10, it is shown that there are the one or more buried conduits 200, or at least partially buried, in the subsurface for conducting irrigation and drainage liquids, an irrigation liquid supply valve 400, and a drainage pipeline 500 to receive drainage liquid from the conduit(s) and release the drainage liquid from the subsurface irrigation and drainage system 100. Other components described in relation to embodiments of the subsurface irrigation and drainage system 100 may be provided as appropriate, such as, but not limited to the inlet and outlet manifolds 700a, 700b as described with reference to Figures 2 and 3. For example, Figure 11 also shows the connection to the pressurised irrigation liquid source 300 and the one-way valve 900.

Additionally, in the embodiments of Figures 10 and 11, the subsurface irrigation and drainage system 100 further comprises a supplemental irrigation device 2000. The supplemental irrigation device 2000 is additional to the subsurface irrigation and drainage system 100.

The supplemental irrigation device 2000 is for irrigation. In this manner, the supplemental irrigation device 2000 is for providing an irrigation liquid. In the embodiments of Figures 10 and 11, the subsurface irrigation and drainage system 100 is shallow and primarily used for drainage, with occasional deep irrigation.

The supplemental irrigation device 2000 is positioned above or shallower to the subsurface irrigation and drainage system 100 in the soil profile. Whilst subsurface irrigation and drainage system 100 is referred to, the supplemental irrigation device 2000 is part of subsurface irrigation and drainage system 100. Therefore, in some configurations, the supplemental irrigation device 2000 is positioned above or shallower to features that provide the irrigation and drainage of subsurface irrigation and drainage system 100. More particularly, in some configurations, the supplemental irrigation device 2000 is above or shallower than the buried conduits 200 of subsurface irrigation and drainage system 100 in the soil profile. Additionally or alternatively, in some configurations the supplemental irrigation device 2000 is above or shallower than at least one of the liquid supply valve 400, and/or the drainage pipeline 500, and/or the inlet manifolds 700a and/or the outlet manifolds 700b as appropriate, when present.

The supplemental irrigation device 2000 is relatively shallower than the subsurface irrigation and drainage system 100. Likewise, the subsurface irrigation and drainage system 100 is relatively deeper than the supplemental irrigation device 2000. The supplemental irrigation device 2000 may be in the soil shallower than the subsurface irrigation and drainage system 100, may be on the soil surface, or may be above the soil surface. Therefore, the supplemental irrigation device 2000 is a relatively shallow subsurface irrigation device or a surface irrigation device.

In some configurations, the supplemental irrigation device 2000 may be a spray irrigation device, a surface drip irrigation device, or a shallow subsurface drip irrigation device. The supplemental irrigation device 2000 may comprise one or more apparatuses to provide the irrigation. For example, the supplemental irrigation device 2000 may comprise one or more spray heads or spray nozzles and/or one or more irrigation conduits.

The supplemental irrigation device 2000 is positioned above the drainage and irrigation system 100 to provide a soil profile separation for any bioremediation of any applied wastewater or treated effluent water via land treatment or disposal of the applied water from shallow irrigation through the soil environment, before the drainage of any surplus soil water through the deeper subsurface irrigation and drainage system 100. In addition to the function of drainage, the supplemental irrigation device 2000 allows the drainage and irrigation system 100 to optionally provide: (i) deep irrigation (e.g. in drought); (ii) injection of fertiliser, or other soluble chemical or biological reagents such as: soil conditioners; biological agents; hydrogels, or other; (iii) or control of salt front(s); (iv) or deep aeration; (v) or other functions.

In the embodiment shown in Figure 11, the supplemental irrigation device 2000 is a popup or other type of overhead sprinkler or spray irrigation device. A separate potable water source may be used for an additional overhead irrigation. The overall potable water volume consumed is greatly reduced as most of the irrigation liquid used in the subsurface drainage and irrigation system 100 may be recycled water. The subsurface drainage and irrigation system 100 may be operated in conjunction with the supplemental irrigation device 2000 so to assist with: (i) washing in solid fertiliser; (ii) helping germinate new grass seed or other seed; or (iii) assisting soften the soil and ensure even grass texture in very dry conditions.

As shown in Figure 12, the conduits 200 of the subsurface drainage and irrigation system may be within a shallow sand carpet or other water permeable material 3000 overlaid on a deeper subsoil 4000 with less permeability, such as, a modified sports field in which a shallow topsoil or sand carpet is laid over clay or heavy soil. The conduits 200 may be located between a first region 3100 and a second region 3200 of the sand carpet or other permeable material, the first region having a depth of between 150 mm and 500 mm, for example 200 mm, and the second region having a depth of between 10 mm and 100 mm, for example 50 mm. Due to the impermeable subsoil 4000, water cannot drain away downwards from the sand carpet or other permeable material 3000 and will perch in the second region 3200 of the sand carpet or other permeable material. This water will simply drain through the conduits 200 via the vertically aligned openings 205 formed therein without the need to operate the subsurface drainage and irrigation system in aeration mode or apply any injected air.

The subsurface drainage and irrigation system 100 may be installed at sufficient depth in the sand carpet or other permeable material 3000 to enable turf or other agronomic maintenance practices, such as verti-draining or mechanical aeration via coring etc, to be completed unimpeded. This is especially applicable if the subsurface drainage and irrigation system 100 is installed in conjunction with an overhead spray system as the supplemental irrigation device 2000.

The subsurface drainage and irrigation system 100 described herein substitutes the need for a separate, conventional drainage system (in combination with a conventional irrigation system) with the system performing both functions. A conventional drainage system is often the most expensive system component, making the dual-use subsurface drainage and irrigation system 100 economically attractive.

If the subsurface drainage and irrigation system 100 is the deeper system, i.e. installed under either a surface disposal system, or is a shallow system where the majority of the irrigation is undertaken by the shallow or surface system, then: (i) the recycled water applied on the surface (or via the shallow system) will be bioremediated by the soil before it enters the deeper subsurface disposal system, when it is in drainage mode; (ii) the applied water (and any draining rainfall) may be effectively drained from the irrigation area to a sensitive receiving environment, as being non-contaminated by virtue of the soil bioremediation; (iii) this may be particularly relevant in situations with a high permeable topsoil over impermeable deeper soils; (iv) this could be the case in both the urban environment, or large-scale rural land treatment systems; and (v) where also the system 100 may be very useful when in irrigation mode for the distribution of hydrogels or reagents or deep irrigation or deep aeration - involving a greater soil volume than if introduction via the shallow, or surface irrigation system.

The disclosed subsurface drainage and irrigation system 100 enables occasional high velocity scour flushing where the irrigation scour cleaning liquid release valve 800 separates dirty flush water from clean drain water via the drainage liquid release valve 600.

Preferred embodiments of the invention have been described by way of example only and modifications may be made thereto without departing from the scope of the claimed invention.

Claims

1. A subsurface irrigation and drainage system comprising: one or more elongate conduits for conducting irrigation and drainage liquids, each conduit comprising first and second conduit ends, and a wall portion defining an internal liquid passage between the conduit ends, the wall portion having a plurality of longitudinally spaced openings formed therein and arranged to allow the transfer of irrigation liquid from the internal liquid passage to the subsurface and the transfer of drainage liquid from the subsurface to the internal liquid passage; a plurality of emitter units, each emitter unit associated with at least one of the openings and configured to control the rate at which the irrigation liquid is emitted into the subsurface; an irrigation liquid supply valve, a drainage liquid release valve, and an irrigation scour cleaning liquid release valve; a pressurised irrigation liquid source arranged to supply pressurised irrigation liquid to the first end of each conduit when the irrigation liquid supply valve is open; and a drainage pipeline arranged to receive drainage liquid from the second end of each conduit and to release the drainage liquid when the drainage liquid release valve or irrigation scour cleaning liquid release valve is open; wherein the system is operable in a normal irrigation mode, in which the irrigation liquid supply valve is open and the drainage liquid release valve is closed, a drainage mode, in which the irrigation liquid supply valve is closed and the drainage liquid release valve is open, and a scour cleaning irrigation mode, in which the irrigation liquid supply valve is open and the irrigation scour cleaning liquid release valve is open.

2. The subsurface irrigation and drainage system according to claim 1, wherein the pressurised irrigation liquid supplied during the scour cleaning irrigation mode is non-potable.

3. A subsurface irrigation and drainage system comprising: one or more elongate conduits for conducting irrigation and drainage liquids, each conduit comprising first and second conduit ends, and a wall portion defining an internal liquid passage between the conduit ends, the wall portion having a plurality of longitudinally spaced openings formed therein and arranged to allow the transfer of irrigation liquid from the internal liquid passage to the subsurface and the transfer of drainage liquid from the subsurface to the internal liquid passage; a plurality of emitter units, each emitter unit associated with at least one of the openings and configured to control the rate at which the irrigation liquid is emitted into the subsurface; an irrigation liquid supply valve; a pressurised irrigation liquid source arranged to supply pressurised irrigation liquid to the first end of each conduit when the irrigation liquid supply valve is open; a drainage pipeline arranged to receive drainage liquid from the second end of each conduit; and a supplemental irrigation device positioned on or above a soil surface or positioned shallower in the subsurface than the one or more conduits of the system; wherein the system is operable in a normal irrigation mode, in which the irrigation liquid supply valve is open, and a drainage mode, in which the irrigation liquid supply valve is closed.

4. The subsurface irrigation and drainage system according to any one of claims 1 to 3, wherein at least one emitter unit comprises a body, at least one conduit- adjacent aperture, at least one subsurface-adjacent aperture, and a labyrinthine channel for conveying liquid between the apertures while generating turbulence in the liquid such that the pressure of the liquid is reduced, the conduit-adjacent aperture being configured to allow irrigation liquid to pass from the conduit into the body and drainage liquid to pass from the body into the conduit, the subsurface-adjacent aperture being configured to allow drainage liquid to pass from the subsurface into the conduit and irrigation liquid to pass from the conduit into the subsurface.

5. A subsurface irrigation and drainage system comprising: one or more elongate conduits for conducting irrigation and drainage liquids, each conduit comprising first and second conduit ends, and a wall portion defining an internal liquid passage between the conduit ends, the wall portion having a plurality of longitudinally spaced openings formed therein and aligned at least substantially along a common plane to allow the transfer of irrigation liquid from the internal liquid passage to the subsurface and the transfer of drainage liquid from the subsurface to the internal liquid passage; a plurality of emitter units, each emitter unit associated with at least one of the openings and configured to control the rate at which the irrigation liquid is emitted into the subsurface, each emitter unit comprising a body with a plurality of conduit-adjacent apertures in fluid communication with a plurality of subsurface-adjacent apertures, the conduit- adjacent apertures configured to allow irrigation liquid to pass from the conduit into the body and drainage liquid to pass from the body into the conduit, the subsurface-adjacent apertures configured to allow drainage liquid to pass from the subsurface into the conduit and irrigation liquid to pass from the conduit into the subsurface; an irrigation liquid supply valve; a pressurised irrigation liquid source arranged to supply pressurised irrigation liquid to the first end of each conduit when the irrigation liquid supply valve is open; and a drainage pipeline arranged to receive drainage liquid from the second end of each conduit; wherein the system is operable in a normal irrigation mode, in which the irrigation liquid supply valve is open, and a drainage mode, in which the irrigation liquid supply valve is closed.

6. The subsurface irrigation and drainage system according to claim 3 or 5, wherein the system includes a drainage liquid release valve, and the drainage pipeline is arranged to release the drainage liquid when the drainage liquid release valve is open, and wherein the drainage liquid release valve is closed in the normal irrigation mode and open in the drainage mode.

7. The subsurface irrigation and drainage system according to any one of claims 1, 2 and 6, wherein the drainage liquid release valve is motorised.

8. The subsurface irrigation and drainage system according to any one of claims 3, 5 or 6, wherein the system includes an irrigation scour cleaning liquid release valve, and the drainage pipeline is arranged to release the drainage liquid when the irrigation scour cleaning liquid release valve is open, and wherein the system is operable in a scour cleaning irrigation mode, in which the irrigation liquid supply valve is open and the irrigation scour cleaning liquid release valve is open.

9. The subsurface irrigation and drainage system according to any one of claims 1 to

8, wherein at least one of the emitter units is a semi-pressure compensating emitter.

10. The subsurface irrigation and drainage system according to any one of claims 1 to

9, wherein at least one emitter unit contains a filter element with a plurality of pores, the pores being sized and shaped to allow soil particulates in the drainage liquid to pass through the pores but prevent debris in the irrigation liquid from passing through the pores.

11. The subsurface irrigation and drainage system according to claim 10 when dependent on claim 4 or 5, wherein the filter element is in the conduit adjacent aperture(s).

12. The subsurface irrigation and drainage system according to claims 4, 5 or 11, wherein at least one emitter unit has at least two spaced-apart subsurface- adjacent apertures aligned along a common plane.

13. The subsurface irrigation and drainage system according to claim 12, wherein at least one conduit-adjacent aperture is also aligned with the subsurface-adjacent apertures along the common plane.

14. The subsurface irrigation and drainage system according to any one of claims 4, 5 or 11 to 13, wherein the body of the emitter unit(s) is substantially flat and sized to be accommodated within the internal liquid passage of a conduit.

15. The subsurface irrigation and drainage system according to any one of claims 1 to 14, wherein an inlet manifold is connected to the first end of at least two of the conduits and an outlet manifold is connected to the second end of at least two of the conduits.

16. The subsurface irrigation and drainage system according to claim 15, wherein the system provides one or more subsurface irrigation and drainage zones, each zone comprising a plurality of conduits between an inlet manifold and an outlet manifold as well as an irrigation liquid supply valve.

17. The subsurface irrigation and drainage system according to claim 16, wherein there are two or more subsurface irrigation and drainage zones and each zone includes a one-way valve between the outlet manifold and the drainage pipeline.

18. The subsurface irrigation and drainage system according to claim 16 or 17, wherein there are two or more subsurface irrigation and drainage zones and each zone includes a control valve between the outlet manifold and the drainage pipeline.

19. The subsurface irrigation and drainage system according to claim 18, wherein the control valve is motorised.

20. The subsurface irrigation and drainage system according to any one of claims 1 to

19, wherein the drainage pipeline is bifurcated into two drainage branch pipes in which one drainage branch pipe is connected to a or the drainage liquid release valve, while the other drainage branch pipe is connected to a or the irrigation scour cleaning liquid release valve.

21. The subsurface irrigation and drainage system according to any one of claims 1 to

20, wherein the irrigation liquid comprises non-potable water, such as stormwater, wastewater, or non-tertiary treated effluent.

22. The subsurface irrigation and drainage system according to any one of claims 1 to

20, wherein the irrigation liquid comprises potable water.

23. The subsurface irrigation and drainage system according to any one of claims 1 to 22, wherein the system includes a collection zone to collect the drainage liquid from a or the drainage liquid release valve and the collected drainage liquid is reused as at least a portion of the irrigation liquid.

24. The subsurface irrigation and drainage system according to any one of claims 1 to 22, wherein the system includes a collection zone to collect the drainage liquid from a or the drainage liquid release valve and the collected drainage liquid is released from the system by gravity, suction pump, or lift pump.

25. The subsurface irrigation and drainage system according to any one of claims 1 to 22, wherein the system does not include a drainage collection zone and the drainage liquid is released from the system to the environment through a or the drainage release valve.

26. The subsurface irrigation and drainage system according to any one of claims 1 to

25, wherein the drainage pipeline is downwardly angled and/or uses suction to receive drainage liquid from the second end of each conduit.

27. The subsurface irrigation and drainage system according to any one of claims 1 to

26, wherein the system includes one or more gas introduction ports to introduce gas into at least one of the conduits for aeration of the subsurface.

28. The subsurface irrigation and drainage system according to any one of claims 1 to

27, wherein the system includes a or the supplemental irrigation device, wherein the supplemental irrigation device is a surface irrigation device or a relatively shallow subsurface irrigation device.

29. A method of subsurface irrigation and/or drainage, the method comprising the use of the subsurface irrigation and drainage system according to any one of claims 1 to 28.

30. The method according to claim 29, comprising operating the subsurface irrigation and drainage system in a drainage mode.

31. The method according to claim 29 or 30, comprising operating the subsurface irrigation and drainage system in an irrigation mode.

32. The method according to claim 31, wherein the irrigation mode is the normal irrigation mode.

33. The method according to claim 31, wherein the irrigation mode is the scour cleaning irrigation mode.

34. The method according to any one of claims 31 to 33, comprising simultaneously operating one or more subsurface irrigation and drainage zones in the irrigation mode and one or more subsurface irrigation and drainage zones in the drainage mode.

35. The method according to any one of claims 29 to 34, comprising operating the subsurface irrigation and drainage system in an aeration mode.

36. The method according to any one of claims 29 to 35, wherein the subsurface irrigation and drainage system is installed on a slope.

37. The method according to any one of claims 29 to 36, wherein the subsurface irrigation and drainage system is installed on a convex irrigation area.

38. The method according to any one of claims 29 to 37, comprising collecting the drainage liquid and reusing the drainage liquid as at least a portion of the irrigation liquid in the subsurface irrigation and drainage system.