Get Started With More Efficient Irrigation Systems

Introduction

The world water crisis is undisputable, yet surprisingly little work is being done to promote, develop and understand more efficient, low cost irrigation systems. Drip is considered the ‘choice’ but is ill suited for remote areas with low technology and unpressurized, unfiltered water systems. The systems described here will work well and use less water than drip. Capturing and utilizing any rain that falls is also desirable. First, make use of catchments and hard surfaces to collect rainwater in cisterns. Then save as much water on the land as possible with micro catchments, pitting, swales and imprinting. Check dams in the gullies of course. Mulch, compost or brush bits if you have them.

Alternative irrigation systems

I have worked with and tested many alternative systems from traditional cultures and worked on new methods that work well and use much less water. These generally also reduce weed growth, minimize disease problems and improve yield. These systems include many you may never have heard of, including:

a. Deep pipe irrigation

Deep pipe irrigation uses an open vertical or near vertical pipe to concentrate irrigation water in the deep root zone. Experiments in Africa showed that grape vine weight on a deep pipe drip system was more than double the weight found with surface drip and more than six times the vine weight of conventional surface irrigation. Deep pipe has been the most effective system for many of my restoration projects. I usually will use 4-5 cm diameter plastic pipe placed vertically in the soil 30-60 cm deep near the seedling or tree with a screen cover (6 mm screen) to keep out lizards and animals. These can be glued on with silicone caulk or polyurethane glue. A series of small holes should be spaced down the side of the pipe nearest the plant. Mark it near the top with paint to get the alignment right. Bamboo with the nodes punched out works also, but wrap the bamboo with a few turns of twine or wire to prevent splitting.

Deep pipe irrigation can be used with low quality water. It is possible to set up with simple materials and unskilled labor without extensive support systems (pressurized filtered water is not needed). The deep pipes provide better water use efficiency (due to reduced evaporation) and weed control. They also enable water to be applied quickly and efficiently with no runoff waste even on steep slopes. Deep pipe irrigation with drip emitters installed in 13 mm pipe was also very effective. This provides for deep irrigation but makes it easy to check and repair emitters.

A commercial system is now sold in the USA as DeepDrip.


Deep pipe drip

b. Watering into tree shelter

Tree shelters like Tubex can be inserted into the ground around (over) a seedling and used for watering by simply pouring water into the mini-dam. The amount of water can be calibrated by marking a fill line on the shelter. Irrigating into tree shelters has worked well for species that tolerate getting wet or on sites with fast draining soil. The tree shelters also improve survival by limiting wind exposure, increasing humidity around the plant, eliminating sand blast, and minimizing herbivory. Combining tree shelters with catchment basins is a good minimal cost irrigation system. Double wall tree shelters have worked better in the hottest desert climates.

c. Wick irrigation

Wicks look very promising, either in capillary wicking (slow), gravity fed (moderate), or pressurized (fast) wick mode. Nylon wicks made with woven (not braided), washed and weathered nylon or polyester rope have been best. You can test them by hanging them down into a bucket of water with some food coloring in it and watching the capillary rise. The flow rate will depend on the type of system and wick. Gulf Rope makes a wick rope for herbicide spreaders that works. A Palo Verde seedling in a bucket of 16 grit silica sand in a very hot and dry greenhouse used only 20-30 ml/day. I have been working with wicks since 1989 and have found that 11 mm wick works well. A gravity flow rate using 11 mm new washed solid braid nylon and the hose clamp tightened one turn past snug released about 1 liter/hour. I will usually tighten further, for a release rate of 20 l in 3-5 days. These require some attention to adjust as plant demand and flow rate varies over time.


Gravity wick

Gravity flow moved moisture down a vertical wick from an open reservoir 1.8 m in 8 minutes and 4.5 m in about 15 minutes. This suggests they will work well for deep watering to get roots to groundwater at 2-5 m. Capillary rise in polyester rope was 46 cm up in 6 hours. Do your own tests to make sure your wicks will work. Use a food coloring in the water to help see water flow in the wick.

With 20 l reservoirs and 11 mm solid braid nylon rope wicks washed once, starting in a short length of ~12mm inside vinyl tubing with a hose clamp, the survival was 100% at 5 years after minimal watering for just two years. In 2013 the same wick material performed well in a large garden test. Dr. Preslav Trenchev in Australia has used wicks to irrigate nut tree orchards. About 6,000 nut trees were irrigated for 2 years by this method on 27 farms around Sydney. Seedlings got a 5 liter plastic bucket with a gravity wick with rain collected by an aluminum tray glued to the cover of the bucket. The Groasis Waterboxx, a commercial product, also combines a wick with reservoir and rainwater collection. A low cost wick irrigation system might be made by inserting a wick in the bottom corner of a sturdy plastic garbage bag. This partly filled bag with 80-120 l could provide a couple of months of water for seedlings or young shrubs or trees.

d. Buried clay pot irrigation

Buried clay pot (olla, pitcher) irrigation uses a buried, unglazed terra cotta clay pot filled with water to provide a steady supply of water to plants growing nearby. The water seeps out through the walls of the buried clay pot at a rate that is in part determined by the water used by the plant. This auto regulation leads to very high irrigation efficiency. I found out about this system in an ag extension book by Fan Sheng-chi from ancient China (~50 BCE). Fan Sheng-chi was tasked with improving yields for farmers who had too little land and little water.


Clay pot garden

By selecting covers that collect rainfall any precipitation that does fall can be conserved and utilized. Ollas designed for irrigation are increasingly being sold in the USA, but they are still rare. Most standard red clay garden pots are suitable for irrigation if the bottom hole is plugged. Silicone caulk or epoxy works better than rubber stoppers or corks. Buried clay pot irrigation is also very effective for irrigating cuttings, in the nursery or in the field. In the nursery a sealed pot is placed within a larger pot with the drain left open, with sand or potting mix between them. The interior pot is filled with water and maintains moisture in the soil.


Clay pot herbs

e. Porous capsule irrigation

Porous capsule irrigation is an efficient modern adaptation of buried clay pot irrigation. WetPots are now available in Australia. A great system! Porous capsules can be more easily tied into a piped network than buried clay pots. If you can’t buy them you can make them by gluing clay pots or pots and pot bases together. They have been effective, but are more costly to make and install than buried clay pots or deep pipes.


Homemade porous capsule

Buried porous clay pipes are similar to porous capsules. Finding porous pipe is a challenge, but it’s sold in Japan. Old drain tiles may also be suitable. In a study of buried porous clay pipe in France, water use was cut 80%, chemical fertilizer use was reduced 50% and corn yield increased 83%, melons 48% and potatoes 34%.

f. Porous hose irrigation (leaky hose, sweaty hose, soaker hose, leaky pipe)

Porous hose irrigation parts are readily available and reduce water use. But placing sections of porous hose vertically like a deep pipe is much more efficient. A hose designed for low pressure is needed. This can be connected to a water bottle or a tank and distributing system. Trials of vertically placed 30 cm long 1 cm diameter porous hose were very encouraging. A series of porous hoses in a triangle arrangement can be used to develop wind firmness in very windy areas.


Porous hose on bottle

g. Perforated pipe

Buried slotted drainage pipe run beneath the soil can work much like a horizontal deep pipe. This 10 cm slotted drain pipe has been very successful in installing windbreaks in the Mojave Desert. One run is almost a kilometre. Vertical standpipes with screen covers at about 100 foot intervals are filled from a water truck to water the plants. Filling risers are tied to posts at intervals based on slope and flow direction.


Slotted pipe install, Mojave Desert

h. Micro catchments

Micro catchments are specially contoured with slopes and berms to increase rain runoff and concentrate it. Rain drains into a planting basin where it infiltrates and is effectively ‘stored’ in the soil profile.

Micro catchments are simple and inexpensive to construct and can be built rapidly using local materials and manpower. The runoff water has a low salt content and, because it does not have to be transported or pumped, is relatively inexpensive. Micro catchments enhance leaching and often reduce soil salinity. The primary drawback of micro catchments is that they work only if it rains. Micro catchments improved survival and growth of our transplants in the Mojave Desert. Micro catchments with irrigation can be even better — deep pipes or porous capsules might be best.

i. Waffle gardens

Planting in depressions with compacted walkways between small sections provides some microclimate improvement for the plant and captures added rainfall. The walkways can be rock lined. These waffle gardens were used by the Hopi people in the American Southwest.


Waffle garden

j. Drip — the problem is…

Drip systems require too much water, typically two to four liters per emitter per hour, and they demand regulated water pressure and careful filtration. In addition, we have found that many animals will chew tubing (often called spaghetti tubing) and pipes even when open water is available nearby (including coyotes, rabbits, and dogs). In one study we did using repellants to protect seedlings, all the spaghetti tubing was chewed up before the plants were attacked. We have also tried repellents on the tubing to little avail. The emitters are also easily blocked with sediment and salt, and several insect species plug the emitters. Drip systems are also easily vandalized and repairs can be costly. Supply interruptions can cause plant damage fairly quickly.


Porous hose drip

3. Try alternative irrigation — help advance the knowledge

The cost of all of these systems is modest and they work. Try them! Plants should also receive a tree shelter if possible or a fence to reduce windblast and chewing by animals and insects. These alternative and little-known irrigation systems can dramatically increase survival and improve plant growth even in severe desert conditions. Supplemental irrigation for seedling shrubs and trees should be provided for as long as possible, perhaps once every two weeks the first three months and then once a month for two summers. Water demands for the garden will be higher but may still require refills just once a week. These effective and efficient irrigation systems should be considered for gardens, farms, restoration, landscaping and interior greenscapes because they save water and time.

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15 thoughts on “Get Started With More Efficient Irrigation Systems

  1. I miss the Groasis Waterboxx here. It’s a bit costly, but can be used several times over. The program contains several elements, such as specific planting instructions, knowledge about deep rooting of plants, the use of micorrhiza and lots more. It can all be read on the website, http://www.groasis.com/en . The device uses the water vapour, dew and rain from the sky rather than your own input. I find especially all the available knowledge about the development of strong roots a fascinating read. The idea is to generate such a strong plant that it can survive on its own, with the water it finds in the soil itself. Apparently it’s not only used for trees, but vegetables as well.

    1. Oops, should have read more carefully… Very good article though! It’s a subject that deserves a lot more attention world wide.

    1. Because the horizontal fibers mess up the capillary action along the longitudinal fibers. Twisted spun (not braided) rope works fairly well whether deployed twisted or untwisted into the three constituent ropes.

    2. The very thing that makes plastic so obnoxious, its biodegradable half life being millennia, works in favor of making plastic irrigation solutions extremely sustainable. Compare to any form of processed clay, plant matter, wood, or even metals. A non-pressurized plastic irrigation system might outlast the human race.

  2. The FAO published a book about pitcher culture several years ago. It’s in German. Has it been published in English?

  3. Very thrilled to read this now since ive been looking into better irrigation options for our community. Will dfnatly combine deep pipe & microcatchment! Am sure it will work good.thnx

  4. I’ve read about the deep drip pipes and ollas before, I even thought that a deep drip pipe equipped with some kind of low pressure emitter could be the hot ticket for the area I’m looking to build my Permaculture farm in (high desert of Eastern Oregon, USA). Ollas are hard to come by where I currently live in Western Oregon, though I haven’t checked any of the nurseries in the desert yet. Combining these technologies with good earthworks such as swales, gabions, keyline plowing and such could very well be the key to re-greening deserts worldwide. Thanks for the well written article!

  5. I would suggest a four fold taxonomy for irrigation: surface, subsurface, pulsed, and continuous.

    Surface and subsurface are obvious. Pulsed and continuous reference the manner in which water is applied to the soil in immediate contact with the irrigation system.

    Pulsed irrigation delivers water in batches over relatively short periods of time thereby saturating the soil in contact which may stress plants. Pulsed might also be called pressurized because that is the most common way to do it. Surface sprinkler and surface drip irrigation are obvious examples of pulsed irrigation as is deep pipe irrigation. Subsurface Drip Irrigation (SDI) is a big agribusiness (led by Netafim) using pressurization to drive the water into contact with the soil through emitters in buried pipelines while inevitably encountering the complications mentioned in the article.

    Continuous irrigation releases appropriate amounts of water at all times in response to the varying physical condition of the contacted soil while attempting to avoid saturation. Capillary action and gravity are the primary means of delivery and spread of the supplied water, although osmosis could play a role, especially in contact with plant roots. Wick irrigation and ollahs are obvious examples. It is worth noting that continuous irrigation systems are inherently non-mechanical in their basic nature.

    Continuous systems could also be called stored water systems in that each means of releasing water in to the soil acts as if an unending source of water was constantly in contact with it. Continuous irrigation can use pipes, rain catchment, and even mechanically assisted low pressure for water distribution such as to an uphill reservoir. The “fast” wick mode mentioned in the article could be a pressurized continuous system but more likely would be used in pulsed mode as keeping up the pressure would incur cost in terms of energy expenditure and maintenance.

    Although there are relatively few continuous irrigation systems in use, the physics of continuous irrigation is well studied in thermo and fluid dynamics: Darcy’s law, etc. Albert Einstein published his first scientific paper on the topic. The material properties of porosity, permeability, membrane characteristics, and contact (angle) with water (such as the amazing advantage of fiberglass over nylon rope) play a major role in the design continuous irrigation systems. The same fundamental principles are commonly considered in many other fields including hydrology, soil science, geology, and oil exploration.

  6. Don’t give up on drip irrigation quite yet. It does work in cases where you use clean water as in many of the examples above. I have not experienced emitter clogging or damage by animals others have, but each site is different. Water can be pulsed or not and low pressure gravity works well with proper design and emitters. Drip does require maintenance as with any other irrigation system and is relatively inexpensive if plants are not too far apart.

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