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Water is scarce on planet Earth. While 70% of the globe is covered in water, only 4% of this is fresh water. Once
the water in glaciers, snow, ice and aquifers is taken into account, less than 1% of the total volume of water is
available and accessible to support all living organisms on land. As gardeners, we need to value this water and
use it wisely.

Water has a natural cycle, falling as rain then evaporating off surfaces, transpiring through plants, or being absorbed into the soil. Some rainfall will percolate deep into groundwater where it will slowly make its way into streams and rivers. Once it evaporates into the atmosphere, the cycle begins again. The water cycle is a closed cycle; water is constantly moving through the cycle but no new water is created; the water we have now is the same water from thousands of years ago.

Australia is the driest country of the planet, and climate change is resulting in an even hotter, drier environment.
The climate predictions for Melbourne are for less rainfall overall and longer and more volatile summers, with
more frequent, intense heat events. At the same time, we can expect more unpredictable, large rain events, and
these can lead to local flooding.
In a forest environment, there are high levels of transpiration from plants and evaporation from the ground,
with excess rainfall infiltrating the soil and slowly percolating into groundwater base flow. This water makes its
way gradually into creeks and streams. In cities and urban areas, hard surfaces like buildings, roads and paving
reduce the amount of water making its way into soil and groundwater. Fewer trees reduces the amount of
transpiration. Stormwater runoff flows off hard surfaces quickly and all at once into drains. This results in drier
soil, and can overwhelm creeks and streams and cause local flooding.

All of the information above leads us to consider our water use differently; water is precious and we may need
to modify how we use it. We also need to consider how transient water is on our patch – how it flows in, is
retained and used, and how it leaves our gardens.
In our gardens water usually comes from either rainfall or tap water. It is then used to water plants or to support
biodiversity (eg ponds and bird baths), stored in soil or water tanks, or reused as grey water. Eventually water
leaves our garden through stormwater channels, the sewage system, evaporation or transpiration. The only one
of these elements that we can’t have some influence over is rainfall. We can make positive changes in all the
other areas to use water more smartly.
Having a water smart goal can help us to prioritise water in our patch. For example, “To reduce the amount of
water used by our garden and lost in the landscape while maintaining all the environmental benefits.”
Once we have a water smart goal we can then look at several aspects of gardening to see where changes can be
made.

•  Know your site: where are the sunny, hot spots? Where does water pool when it rains?
• Plan for water storage and irrigation, as this is easiest to install when constructing a garden
• Swales, sinks and dry creek beds are ‘soft’ landscaping features that slow water runoff and keep it onsite
  longer. Considerations: you may need gravel, mulch or plants to stop soil erosion; a lining to stop weed growth;
  clay soils may become waterlogged; need an overflow for heavy rain.
• Permeable paving: use mulch or gravel or paths, paving with gaps or a custom product that allows water to
  infiltrate.
• Hydrozoning: group plants according to water needs, eg irrigated veggie patch and unirrigated native beds.
• Consider creating shadier microclimates to cool your space and reduce water use.

• Healthy soils with high organic matter content (compost, leaf litter, animal manure, organic mulch) require less
  water
• Organically managed soil should be: rich in organic matter, teaming with soil micro-organisms, abundant with
  earthworms – the processors and aerators of healthy soil – and covered with a layer of mulch.
• The best approach to adding and keeping moisture in your soil is to add organic material, mulch and water
  correctly, and cover soil with plants including groundcovers.
• Where do I get organic matter?
  • Veggie garden: Use compost made from recycled household waste; animal manures or worm castings
    (vermi-compost); straw mulches.
  • Native garden – Use leaf litter, twigs and other material left to breakdown on site; bark mulches.

• Plants have developed many strategies to cope with hot and dry climates and reduce the need for water:
  • Leaf size or shape (e.g. strappy leaves, small curled leaves) that reduce surface area for transpiration.
  • Leaf colour, with grey/silver/blue leaves reflecting heat and reducing transpiration. Many of these have
    hairy leaves that also trap moisture.
  • Growth in cooler months or dormancy in hotter months (arid wildflowers, bulbs).
  • Different photosynthesis pathways, eg. succulent
• Indigenous plants are suited to the local soil and climate. They often require less water once established.
• Plants from arid, hot climates eg. South Africa and the Mediterranean, are often drought tolerant

Tips for lawns: Redesign to decrease amount of lawn; replace with warm season grasses (eg. Buffalo); short cut
lawns use more water than long cut lawns; use a mulching lawn mower; water deeply (for longer), less often

• Mulch is a fantastic water-saving tool in the garden. It keeps soil moist for longer (less evaporation), suppresses
  weed growth, reduces water runoff and prevents hydrophobic soils, regulates soil temperature and adds
  nutrients to the soil as it breaks down.
• Use organic mulch (bark, wood chips, leaves, straw) in most cases. Inorganic mulch (pebble, scoria, rocks and
  gravel) is an alternative when erosion is a risk, eg in swales or sinks, around ponds.
• Which organic mulch?
  • Chunky is best, allowing more air and rain to penetrate and breaking down slowly.
  • Wood chip / landscapers mulch is best for native and ornamental gardens. It breaks down slowly and
    provides habitat for insects and fungi.
  • Straw mulches are best for veggie gardens: Pea straw, Lucerne, oat / wheat straw, sugar cane mulch.
• Living mulches provide all the benefits of mulch plus they shade the soil and create a cooler microclimate.
  Suggested species: Creeping Boobialla (Myoporum parvifolium); Fanflower (Scaevola sps); Kidney Weed,
  (Dichondra repens); Native Violet (Viola hederacea).
• Applying mulch:
  • The best time to add mulch is after spring rains but before summer drying.
  • Make sure the soil is moist prior to mulching.
  • How thick? Bark mulch: 25 → 75mm; Straw mulch: 50 →100 mm (will compact down as it settles)
  • Keep mulch away from plant stems and tree trunks to avoid the risk of collar rot.

The water we use in the garden comes either from the tap (not ideal) or from rainwater or grey water.
Other ways to capture water include raingardens and downpipe diversion.

Rainwater Tanks

• Capturing water and storing it for future use is a feature of water-wise gardens. There are a lot of options for
  tanks in terms of materials, position, size, whether a pump is needed etc. It’s a good idea to do some research
  and consult a licensed plumber. Also check whether council approval is needed. How big should the tank be?
  1mm of rain on 1 m2 of roof equals 1l of water.
• Rainwater capture: ensure access to the tank is good and consider installing it on the shady side of the house.
  Tanks need an overflow connection, and a first flush diverter is also desirable to avoid contaminants entering the tank. Rainwater tanks can also be connected to flush toilets

Distributing rainwater

• Using gravity: water pressure will depend on how full the tank is and the gradient of the site and height
  of tank. Gravity feed is suitable for low pressure drip line systems.
• Pumps will increase water pressure but need a power source. There are different options available to
  have water pressure constantly charged or to increase pressure only when water is being used.

Consider water banking

If a rain event is predicted, (part) empty your tank water into your soil to increase water stored deep in your soil and make room in your tank for more rainfall.

Grey Water

• Grey water is a reliable source of garden water but it comes with some special considerations. Grey water usually refers to waste water from the bathroom and laundry (not toilet or kitchen). Grey water systems can be simple (diverting water using a bucket or hose) or complex (treatment systems).
• Grey Water Use Recommendations
  • Grey water may contain organisms that are dangerous to human and/or animal health!
  • Don’t use grey water on vegies /herbs that could come in direct contact with the grey water.
  • Can use on fruit trees
  • Do not allow children to play with grey water or pets to drink grey water.
  • Do not use untreated grey water for spray irrigation.
  • Use subsurface distribution such as porous hoses or drippers beneath a layer of mulch.
  • Choose detergents used in the house carefully – low in Phosphorus and salt
  • Rinse water is the best
  • Alternate with fresh water to dilute chemicals

Water should be delivered directly to the plants’ root zone, preferably in the early morning when the
temperatures are cooler.

• For garden beds: water more thoroughly, less often to encourage the development of deep roots, increasing
  drought tolerance.
• For pots and containers: water sparingly, more often and place a saucer or container under the pot to collect water in summer.
• Consider installing a drip irrigation system or using a soaker or seeper hose. Watering at the soil’s surface avoids wasting water as a result of spray drift and evaporation. Surface / subsurface irrigation promotes deeper root growth and delivers water to where it’s needed: plant roots.
• Self-watering pots and wicking beds are also excellent options for water conservation

In summary, as gardeners we should aim to use enough water to keep our gardens healthy without wasting a drop. We can do this through smart garden design, creating shady microclimates, focusing on soil health, watering efficiently and
choosing and zoning plants wisely. We can also consider ways to store rainfall and use grey water so that we aren’t totally reliant on tap water. All these measures will help us meet our waterwise gardening goals.

Watch the Water Smart Gardening video, presented by Sustainable Gardens Australia

Other useful links include:

Good Life Permaculture swale pathways

SGA permeable paving

Tankulator tank size calculator

Renew water conservation, collection and reuse

Gardening Australia guide to greywater

Gardening Australia grey water maintenance

Melbourne Water raingarden instruction sheets

Deep Green Permaculture how to make a rainwater tank from olive barrels

Deep Green Permaculture how to make a rainwater tank from a wheelie bin

SGA wicking beds