Nature, our great teacher, manages water by catching rainwater, slowing it down and using plants & soil to absorb water into the landscape. These techniques are influenced by nature and used on my 1.5 acre site in the Bellinger Valley, NSW.
1. Catch and store rain water
Catching and storing rainwater in the form of very large dams is often a destructive exercise. Read “When the Rivers Run Dry” by Fred Pierce for a full explanation, but reasons include salination, excess siltation behind the dam, lack of silt flow past the dam and blocking of fish movement.
Catching and storing water on the small scale can allow us to feed ourselves while simultaneously rehabilitating land. Thus, small scale catching and storing of water is a fundamental topic in permaculture. Techniques include tanks, ponds and small dams (up to a few megalitres or so). Rainwater tanks are useful for storing high quality water close to buildings without evaporation. Dams are useful as very cheap storage of larger amounts of water and as good growing sites in their own right.
2. Swale with path at base.
Swales are much used in permaculture to convert fast running surface water to slow moving ground water. In the subtropics you often get short, intense storms. Rainfall from such storms runs quickly down a mown hill and can leave the site as fast as 1 metre/ second. A swale catches surface water and allows it to soak into the soil. Once absorbed into the soil, water moves very slowly downhill, maybe only a few metres/ year. So if you have a well maintained grassy hill, water is leaving the site one million times faster than it needs to. We plant tree crops are on the swale mound to stabilise the mound, provide shade & mulch and to open up the soil to a greater depth. The swale performs better with the help of the trees and and the trees benefit from increased soil moisture & organic matter accumulation provided by the swale.
To build a swale, peg out a line on the ground on contour, i.e. of equal height above sea level. If you don’t have a laser level, there are simple methods using a clear hose or a plumb bob in a triangular frame. Dig a trench on contour and use the same equipment to achieve a level trench floor. Spread the “spoil”, i.e. the dirt you dig up, on the downhill side of the trench.
The bare soil should be immediately planted and thickly mulched. Plants that work well here are a mix of fast growing groundcovers (e.g. pumpkin, sweet potato), clumping plants for mulch & stability (e.g. sugar cane, vetiver grass, fine leaved lomandra), fast growing pioneer shelter plants (e.g. pigeon pea, native Bleeding Heart, wattle), tall tree crops (e.g. macadamia & other native nut trees, avocado), mid sized crops (e.g. jaboticaba, custard apple, banana) and slower growing perennial ground covers (e.g. pineapple, perennial greens, tumeric, ginger).
The easy way to dig swales is to plan the site first and put them in before doing any planting. We were not sufficiently blesed with such foresight and did a “swale reno”, shown below.
3.Swale used as a trench pit.
Another version of a swale. The trench floor isnt used as a path, but as a pit which holds bulk organic matter, such as larger prunings, excess bamboo poles, etc. As with any swale, there is a downslope mound planted with trees or in the example below, clumping bamboo.
4. Gravel filled trench.
This is a variation of a swale useful for areas of high garden traffic. A conventional swale has a mound and trench which is awkward to move over. A gravel filled trench maintains a a flat surface so it can sit nicely within an intensive gardening space, store & distribute water and double up as a path. The spoil can be used to build up a garden bed. The trench is filled with rubble – we used recycled concrete rubble. This trench takes the overflow drom a water tank. Thus, a fast flowing point source of water is converted into a slowly soaking band of soil moisture. Thirsty crops like annual vegies are planted immediately below the trench.
By the way, many people who live on rural land use a sullage trench but have never seen one. A sullage trench is where household wastewater ends up after it leaves the septic tank. A sullage trench looks something like this gravel trench with a few additions. Geotextile fabric is placed over the gravel (to stop soil clogging the gravel pore space), and then about 25cm of soil laid on top and usually used to grow grass.
We’ll define a container as anything in size from a garden pot to a raised bed. An advantage of growing plants in containers is that the drainage and the soil type can be controlled. Containers are a solution if the soil near your kitchen is unsuitable for vegies – maybe it’s a mat of eucalypt roots, maybe it’s concrete.
Conventional pots and raised beds have way too much drainage and demand too much water. As with many of our environmental errors, it doesnt need to be this way. If drainage is carefully controlled then containers can be a water conservation device. In recent times “wicking beds” have emerged as a water saving alternative. Wicking beds consist of a multi layered container using soil over geotextile blanket over a gravel filled water resorvoir. Water is delivered to the resorvoir and is then theoretically drawn up through the soil profile like a wick. The wicking action depends on geotextile cloth not getting clogged by tiny clay particles and also that the reservoir is kept full.
The bed I built is more simple than a wicking bed. It has only soil (no gravel or geotextile fabric). The whole bed is lined with rubber (to hold water and be a root barrier) within a protective blanket. Drainage holes are close to the top of the bed. I expected to experiment and add more drainage holes as required, but none have been necessary.
Another reason why conventional containers use a lot of water is that the sun heats up the container wall and dries out soil behind it. I found this to be a real problem with metal walled beds. The problem was solved by going to an op shop, getting a large roll of nylon material and laying it thickly inside the bed wall for insulation. Shadecloth was placed on the outside of the walls to cut out direct sun.
An additional feature of this bed is adjustable shade. Sweet, tender greens can be grown in the heat of summer using very little water if the bed is covered with 50% grade shadecloth. In winter the shadecloth is fully retracted and at other times, something in between.
Take a container with no drainage and you have a pond. You can also make a pond by digging a hole and lining it with plastic, rubber, clay, bentonite or concrete. The difference between a pond and a dam is that a dam needs an above ground wall to hold water. A pond is dug entirely below ground level.
There are plenty of nice things to say about ponds. Food grows more rapidly than on land, so urban areas with large roofs next to small gardens might produce more with a pond. Ponds offer great habitat for birds to wash & drink and frogs to breed. A pond can also function as a therepeutic refuge for anyone who feels a bit rushed.
The first question everyone asks about ponds is “What about mosquitos”. Aquaculture is a slightly different skillset to land gardening and in the beginning there will probably be some imbalance in the ecosystem including mosquitos or sandflies. An established pond is a dangerous place for mosquito larvae as it is thickly patrolled with a range of predators. Most tadpoles eat them and certain native fish will eat mosquito larvae but leave frog eggs and tadpoles alone. If you’re really worried you can have a bog pond or “rain garden”. In this type of garden, soil is covered with a thick layer of gravel or woodchips. An overflow pipe exits below the surface of the gravel, so the top of the bed stays dry.
Ponds are a form of water conservation if water that would otherwise leave the site is caught, used productively and conserved by providing summer afternoon shade. Ponds are a form of excess water consumption if water is imported from mains supply and left to evaporate all summer.
7. Give water a complicated pathway
In our society, water use is generally once off. Water is imported long distances, used once, polluted, then exported long distances. Leigh Davison of Southern Cross University and famous wastewater pioneer calls it “big pipes in/ big pipes out”. It’s an obviously unsustainable approach but that’s how our urban areas were built. Sustainable water use involves catching and storing rainwater that falls on the site and placing a great variety of obstacles in it’s path when gravity attempts to take it downhill. If each of these obstacles is useful for storing water, growing food or rehabilitating landscape then water is effectively used many times over.
Here’s an example at my place: Roof water runs into a water tank, then to the shower, then to subsurface pipes under a thickly mulched vegie garden, then through terraced beds of asparagus & taro before settling into a swale feeding more vegies. This all occurs over 8 metres in plan. The water then moves through two more swales over 15m of food forest. For the next 8m it passes through a silt trap and another swale used to grow bamboo and nut trees. After water pushes its way through all that lot, it encounters another 40m of planted native rainforest. The final stop for any water before it leaves the property is a small dam used for native habitat.
8. Concentrate resources
Direct water to a small, intensively managed area. If you have the space, you’ll probably spread out too far with too many plants that need too much water. I made this mistake and so have many others. After learning the error of my ways I made the important garden smaller and smaller. The result was more and more food.
9. Leaky sinks
Note here that in wastewater jargon, a “sink” is not just something you put in the kitchen to wash dishes. It has a much broader meaning which basically means the exit point of used water. Our society has a history of engineers who diligently strived to create sinks that get water away ASAP. One of them said “Early in my career, I learnt how to straighten rivers. Late in my career, I learnt how to bend them.” It’s time to learn to slow water down. The leaky sink converts water from a gush to a dribble.
At a beach near here there’s an outdoor shower with a big metal bowl under it. When people come off the beach and have a rinse, water ends up splashing in the bowl from which dogs gratefully drink. This illustrates an advantage of the “leaky sink”, i.e. put something functional in the way of a drain hole and you get free water.
In the example below there are two water tanks with a couple of taps. Any splash from the taps once fell uselessly onto the grass. Now there is a vegie garden underneath, so every time hands or potatoes get washed, some spinach gets watered.
10. Silt traps
When primary school kids visit my garden I sometimes call these “baskets”. They’re designed to catch. They’re not perfect because they have little holes in them but they do a pretty good job. A good instrument for measuring site stability is a soccer ball. If your garden is on a hill and a soccer ball easily rolls down the hill, you need more silt traps.
A silt trap is a series of closely spaced clumping plants, used as a garden border or a border for beds within a garden. They can be contoured strips, circles, grids – whatever you like. Water and leaf litter moving downhill is trapped and settles into the silt trap. The trapped resources feed the silt trap, the silt trap grows thicker, it catches better, it gets fed more and so on. The same goes below the surface – water is filtered through a dense network of roots. Where you have water, you have dissolved nutrient, so it too is taken up. The silt trap can be cut as mulch. Even left alone it enriches the garden. Some plants I’ve used for silt trap include lemon grass, many species & cultivars of Lomandra, kangaroo paw (with mixed results), Strelitzia, vetiver grass, clumping bamboo, banana and asparagus.
11. Species selection
Put hardy plants together in tough areas and thirsty plants together in kind areas. Obvious but “common sense isnt always common”. Thanks to global warming, seasons here are getting hotter and drier. So sites that might have been OK in the past are now becoming tough sites to grow on. Mangos, olives, figs, guava, mulberry, meditteranean herbs and New Zealand spinach are dry tolerant coastal crops. Annual vegies, perennial greens, banana, clumping bamboo and a range of fruit & nuts need decent moisture levels.
12. Summer shade
If you live in England, you want full summer sun to grow food. On the north coast of NSW, you don’t. Most summer vegies grow better in filtered semi shade and most tree crops grow better under a light overhead canopy. It is useful to arrange planting or buildings that cast heavier shade on a summer afternoon. You can grow these plants in full sun if you want but you are going to need lots and lots of water.
At this place there are structures including shade houses and overhead trellis. There are also plantings for overhead shade within the garden and thicker plantings on its western border. There is crop rotation – some beds that get good winter sun are piled up with mulch and left fallow over summer. With shadehouses, it is good to leave some kind of opening that allows birds to get in and control slugs. It’s also a good idea to build retractable shadehouses so you can peel back shadecloth in winter, when you do want sun.
13. A useful first flush diverter
Any rainwater tank used for drinking usually has a first flush device fitted. This is usually a small pipe that fills up with the first few litres of roof runoff, and emptied later. The idea is that most of the dust, bird droppings etc. is carried in the first runoff and kept out of the tank. Common problems with first flush diverters include they don’t hold enough water, are a hassle to empty and the water in them gets wasted.
My first flush diverter is relatively large – 200 litres. It is the major water supply for the kitchen garden and nursery, the most water demanding activities. The first flush is automatically emptied whenever I water. Most of the dust, etc. is heavy sediment which gravitates to the bottom of the drum, where the tap is. This is an example of deliberately arranging a beneficial connection. The first flush wants to be emptied. The garden wants water to be emptied on it.
14. Grey water diversion
Grey water is all household waste water except flush toilet. The quality of greywater depends on what you put down the sink. Thus, while the NSW Dept of Health allows greywater diversion it doesnt like it used for vegies. I believe it should be a matter of user takes responsibility. We use little or no soap in the shower and washing machine and send the greywater into a thickly mulched vegie garden. The water is good quality and delivered to the plant roots, not splashed on any leaves. There are no mosquitoes because the pipes are covered by thick mulch. “Diversion” means there is a tap in the system that can undivert waste water back into the main treatment sytem if there is a problem or you’re worried about something stronger about to go down the sink.
Greywater diversion works well for vegies because they like regular water and people regularly shower. If they shower a bit longer in hot weather, they’re helping the garden. It’s a good idea to have some kind of filter. There are off the shelf products but I used a simple splitter box with shadecloth and fabric. It needs to be cleaned fortnightly and takes a few minutes to clean.
The splitter box also allows for equal distribution into two separate runs. In this case a run is PVC pipe laid on the top of the garden bed and made level by sitting on bricks. 10mm holes are drilled in the top of the pipes about every 20 – 25cm and covered with thick mulch. The ends of the pipes have screw caps for flushing points.
Twice/ year I unscrew the caps and run clean water through the sytem. Then I screw the caps on, uncover the mulch and check the water flow out of all the pipe holes is even. If it isnt, it can be adjusted by packing pipes over the bricks they sit on.
15. Black water
Black water is water from a flush toilet. Kitchen water is not technically black water but it can be high in salt, fat and deterent so we don’t send it into a vegie garden. This water goes via a septic tank to a sullage trench – a level, gravel filled trench behind which is planted thirsty crops like banana, jaboticaba and black sapote. There’s debate between the benefits of conserving water with a compost toilet or storing rainwater and using it for crops in the above manner via a flushing toilet. When we bought this house it already came with a flush toilet so it was easiest to modify that.
16. Mulch & organic matter
The key to water conservation is to create soil acts like a sponge. It is the easiest, cheapest, best way of storing water. You do this by adding as much mulch and organic matter as you can get, and conserving soil health. I have imported literally truckloads of forestry mulch from tree loppers. It makes good mulch after about a year of aging and adding urine.
17. Avoid compaction
“Bulk density” is the scientific measure of how soft & spongy your soil is. Let’s just keep it simple here and call it “sponginess”. Sponginess makes a huge difference to how much water runs off or soaks into soil and the general health & productivity of soil. When you’re checking out gardens, farms, old rainforests or assessing your own garden, get into the habit of feeling the soil for sponginess. Add plenty of mulch & organic matter, and you increase sponginess. Add the weight of a machine, person or large animal, and you lose it. That’s why sensitive gardeners are very pedantic about where people tread in their garden.
18. Water retentive potting mix
Typical potting mixes and garden bed supplies are extremely well drained. An advantage is they are virtually impossible to over water. Two disadvantages; they use way too much water and that develops a culture where we think it’s normal to water every day. I use 100% organic matter compost as a potting mix or garden bed additive with no problems and greatly reduced water use.
Every good gardener in human history has been observant and reacted to their observations. You can make plans, try strategies and be sure it’s a good idea but you have to assess if it really works. If it isnt working so well, you have to respond with a better solution. On top of that, the climate is rapidly changing so what did work before might not be working now.
20. Food forests
Food forests mimic native forests but are adapted to human needs. Local species suitable for a food forests include a canopy of nut trees (macadamia, native peanut, kurrajong, edible wattle), sub canopy of fruit trees (custard apple, lychee, longan, black sapote, jaboticaba), shade tolerant lower storey (banana, papaya), ground covers (perennial greens, sweet potato, taro), specialist edge plants (citrus, mango, fig, pomegranate) in some cases acting as trellis for edge vines (grape, passionfruit). The whole show is fully mulched during establishment and becomes self mulching and almost self maintaining when mature. The benefits include excellent water conservation as you would expect from a forest.
21. Surrounding microclimate
The idea of permaculture is to grow the most food in the least space with the least imported resources using the least labour. This allows the most land possible to be returned to nature. Strategically located and species selected, the native habitat you provide shelters the garden from extremes of heat and dry wind.
22. Longer cutting cycle
Vegetation is the key to soil and water conservation. Taller ground cover slows down runoff and grows deeper roots. Slower water makes deeper roots, which infiltrate more soil moisture, which grows more vegetation and thus a postive cycle revolves. If you’re sheet mulching, you don’t have to pat everything down nice and evenly, it’s probably better to leave things a bit lumpy – creating many micro pits. Instead of keeping a manicured lawn, let grass grow longer and slash periodically – a special slasher/ mower would be required. The original flat green lawn vista could be replaced by a bumpy, pleasant view of bees visiting dandelions and native finches eating the grass seeds you let go. You can expect to lose some friends who disapprove of your untidiness. It is a worthy sacrifice in the noble cause of land rehabilitation.