22 water conservation techniques
The general behaviour of water management in nature, our model of sustainability, is to slow water down, spread it out, sink rain into the soil and in all cases give water a complex pathway. The following are techniques influenced by natures processes and used on my property near Bellingen, NSW.
1. Catch rain water.
It’s not appropriate to pull water out of rivers, creeks, or ground water and distribute it around settlement. It might be appropriate to let waterways and associated wetlands flow but harvest sustainably some of the yields offered by these extroadinary, productive ecosystems (when healthy and undegraded). Direct as much roof water as possible into large tanks. Direct water flowing overland into swales, ponds, terraces and generally direct water from the ground surface into the soil.
2. Swale with path at base.
A swale is an excavation on contour consisting of a trench and mound behind. Storm water running over the soil surface may leave the site at 1m/ second. The same storm water, when held in the swale and gradually infiltrating the soil, may leave the property at the rate of 1m/ year as ground water. Tree crops are planted on the swale mound to provide shade, open up soil and benefit from the enriched soil moisture.
3.Swale used as a pit.
A deeper swale holds more water but may be harder to manage from the base. Instead, use a path upslope of the excavation. Organic matter wastes (e.g. prunings) are thrown into the swale base. Pits are good collectors of water and organic matter even if not necessarily in the form of a swale.
4. Gravel filled swale.
This is a trenched excavation on contour with no mound. The excavation is made as a V shape to avoid slump and then filled with coarse gravel (the example photograph is of recycled concrete rubble). It holds less water but can be easily trafficked by foot or wheelbarrow.
5. Containment/ wicking bed mark II
The house is on a ridge top with large, invasive tree roots nearby. In this case, high water use gardens (e.g. kitchen greens) are raised and lined with plastic or rubber both as a tree root barrier and to conserve water. Drainage is provided not in the garden bed floor but about 40cm from the soil surface.
This is a variation on the wicking bed. A wicking bed has a very porous gravel base under geotextile fabric under soil. Water sits in the base and must be touching the geotextile to “wick” up. An easier method is to have a clay soil base, no geotextile fabric and drainage somewhere up the sides of the bed.
This soil filled bog pond collects water from a roof downpipe and has fine surface gravel for mosquito control & to reduce evaporation. The overflow is not at a single point, but in a semi circular arc of 25mm diameter holes spaced 10cm apart, to spread the overflow out. In most crops, water is the limiting factor, so ponds can be far more productive than land crops. In ponds, the limiting factor is often oxygen, so rocks and gravel are used above and below the surface of this pond to distribute oxygen.
7. Use the same water many times
Design a complicated pathway of catchment overflow and runoff. For example, roof water runs into a water tank, which goes to the shower, which goes subsurface to a vegie garden, which seeps downhill through terraced beds of asparagus & taro before settling into a swale feeding root & fruit crops. This all occurs over 8 metres in plan. The water then moves through another 15m of garden down slope.
8. Concentrate resources
Direct water to a small, intensively managed area of crops that benefit from irrigation. Like many people, I first tried to spread water over too large an area, and nothing in the area thrived. Contracting the cropping area has made things easier and higher yielding.
9. Integration & leaky sinks
Connect water mess with water mop up crops. e.g. the garden tap used to run off onto a lawn and get wasted. Now it is above a vegie garden, so every time hands or potatoes get washed, some spinach gets watered.
10. Build baskets
A basket is a border of closely spaced clumping plants. They act as a silt trap, retarding overland water flow and recycling it as mulch. You can cut the plants for mulch but even if you don’t, the garden will benefit. Some plants I’ve used successfully include lemon grass, Lomandra in most species and cultivars, kangaroo paw (with mixed results), Strelitzia, vetiver grass and clumping bamboo.
11. Species selection
Put hardy plants in tough areas and water demanding plants in favourable areas. You’d think it blatantly obvious but it’s a mistake made many times, including by me. For example, there was a blueberry bed I set up which just could not get enough water. I ripped them out and replanted the bed with hardy crops like mangos, olives, figs and a ground cover of New Zealand spinach. I put water loving crops like taro, water cress, asparagus, kitchen greens, blueberries & bananas close to waste water, water tank overflows, shade and leaky taps.
Most crops on the north coast benefit from judicious shade. Shade cloth or deciduous trellis can work well over vegies. Adjustable shade cloth over vegies is good to pull over during heat waves and pull off during rainy periods, to allow birds to come in and control slugs. Many fruit crops produce better under a semi shading canopy, if the canopy is not over dominant.
13. Waste water – first flush
The first flush is a pipe which collects and diverts the first few litres of runoff from roof water before it might enter a water tank. The idea is to send the highest concentration of dust, bird droppings, etc. away from the tank. Most first flush diverters are too small and a hassle to empty. My first flush diverter is a 200L drum fitted with a tap and located next to 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 outlet 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. Waste water – shower & washing machine
These go to two runs of 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 mulch for mosquito control. The ends of the pipes have screw caps for flushing points. The runs are split using a splitter box which is also a filter, using a combination of flyscreen, wire mesh and shadecloth. We use liquid soap in the shower and little or no laundry detergent. This filter needs to be cleaned every week or two, which takes a couple of minutes. There are plenty of other possible filters. During heat waves, the plants appreciate people taking longer showers! There is a tap on line to divert the grey water back into the septic water treatment system during heavy rain periods. You’re not supposed to use water like this on vegies according to Dept. of Health but we do and are healthier than when living on food provided by Coles. We try to avoid splash by covering the holes with mulch and growing taller crops like vines, capsicum, okra, corn, etc.
15. Waste water – septic
Black water (flush toilet) goes via septic tank to a level, gravel filled trench behind which is planted thirsty or wet soil tolerant crops like banana, jaboticaba, black sapote. There’s some level of 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.
16. Mulch & organic matter
Mulch breaks up rainfall splash, slowing water down and allowing water to infiltrate the soil.
17. Avoid compaction
Soil porosity makes a huge difference to how much water runs off or soaks into soil. Add plenty of mulch & organic matter, and you increase porosity. Add the weight of a machine, person or large animal, and you lose it. It’s one reason why carefully tended home gardens out yield machine dominated agriculture. Avoiding compaction is done by planning a garden such that it can be managed from paths and stepping pavers and maximising the area of soil that is not trodden (or driven) on.
18. Reduce potting mix drainage
Typical potting mixes and are so well drained, they’re almost impossible to over water. I use compost made of 100% organic matter as a potting mix or garden bed soil. There have been no problems propagating and growing over 200 species of fruit, vegies & native plants in compost with the benefit of greatly reduced water use.
Permaculture is about careful design to save work and other resources. Design is planning, but then also refinement – testing, observing and reacting to what’s really happening on the ground. Observation and reaction are vital gardening skills especially when looking at water and changing climate.
20. Food forests
Food forests mimic native forests but are adapted to human needs. In this area, species suitable for a food forest 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
A core aim of permaculture is to grow as much food as possible in the minimum area with minimum dependancy on exported resources and with minmum labour by letting nature do the work. The reason we do this is to release the maximum area of land and resources back to nature, and you can do this on your own property by growing some native habitat. Strategically located and species selected, this native habitat shelters the garden from extremes of heat and dry wind and increases humidity where required.
22. longer cutting cycle
Vegetation is the key to soil and water conservation. Taller ground cover slows down runoff and grows deeper roots. The slower the water, the deeper the roots, the more water that infiltrates soil, the better the vegetation grows 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 shameless untidiness, but you will gain in the noble cause of soil moisture infiltration.