Outdoor water use

Typically, around 40% of household water is used outdoors, though for some households this figure may be much higher. Sizeable gardens, pools, and dry climates can contribute to high outdoor water use. There are many easy ways to reduce outdoor water use that save time and money, and benefit the natural environment.

Think about future water use when you are first establishing your garden. Smart design decisions now can save water in the long run.

Garden design

Careful landscaping can reduce your outdoor water needs. For example, paved areas increase heat radiation and water runoff from the site, so using garden beds or permeable surfaces instead of paving can improve water retention refer to Stormwater for more information.

Plant trees to create natural shade, and windbreaks to reduce evaporation. Locate high water-use plants in areas where they are sheltered from drying winds and strong sunlight. Where possible, use alternative water sources, such as rainwater or greywater, for high water-use plants.

Photo: Kathie Stove

Plant selection

Select plants that suit the climate, soil and garden conditions. Many Australian native plants have evolved to cope with very little water, and local indigenous plants have evolved to handle local conditions. Incorporating native plants into the garden also provides habitat and food for birds and insects. They, in turn, can aid in pest control and pollination.

Some exotics from South Africa, California and the Mediterranean can cope well with limited water. But that may also mean they have the potential to become environmental weeds. Check for appropriate and pest species with your local natural resources or catchment board, particularly in outer urban or country zones and near conservation areas.

Explore your neighbourhood to discover what appears to grow well in your area. Take note of street trees, which are rarely watered or maintained.

Examples of plants for water-use zones

Group plants with similar water needs together. Divide plants into high, medium, and low water-use zones in your garden. Refer to Landscaping and garden design for more information.

• high water use – lawns, most vegetables, fruit trees, exotic shrubs like azaleas and camellias, flowering herbaceous annuals and many bulbs
• medium water use – hardy vegetables like pumpkins and potatoes, hardy fruit trees and vines like nut trees and grapes, many herbs, some exotic shrubs, most grey or hairy leafed (tomentose) plants, roses and daisies
• low water use – most Australian natives including banksias, grevilleas and eucalypts; succulents and cacti, olive trees, and some exotic ornamentals such as bougainvillea

Reduce lawn area and choose grasses with low water needs

Lawns consume up to 90% of water and most of the energy used in the majority of gardens. They also take the most time and money to maintain. Lawns need mowing, weeding, edging and fertilising, and equipment requires fuel and maintenance.

Reducing lawn area is the easiest way to save water. Replace lawn areas with porous paving, pebbles or drought-tolerant ground covers such as prostrate grevilleas, snake vine (Hibbertia scandens) or myoporum. Create garden beds or spread mulch in areas used infrequently or where grass grows poorly. Seek advice at your local plant nursery.

Different grass types have different watering needs. Select a type that needs less water, such as carpet grass, couch, buffalo, Nathus Green (Sporobolus virginicus), Queensland blue couch, and tall fescues. Many blends and species are region specific. Ask your local plant nursery for the most suitable low-water species for your climate and soil type.

Mulch

Mulching is an essential element of a water-efficient garden. Mulching around plants saves water by preventing evaporation and reducing runoff. Mulching also limits weed growth and can improve soil conditions, depending on the type of mulch.

Mulch can be in the form of leaves and grass clippings, sawdust, rocks and gravel, straw and other crop residues, bark and woodchips. Coarse mulch is excellent for reducing weeds and keeping soil cool but it will not improve the soil. Some nitrogen-rich fertilisers may need to be added before the mulch is laid. Medium and fine mulch are also good for limiting weed growth but can limit water absorption from low rain events, and wear faster over time. Wear can be prevented by less frequent watering.

Before mulching, clear weeds, break up the soil crust and water the area. Spread mulch evenly to a depth of 7 to 10cm. If you are using fine mulch such as sawdust, then a thin layer of around 2.5cm is sufficient. Reapply mulch at least once a year, or as it breaks down. Do not allow organic mulch to touch woody plant stems and trunks or it may cause collar rot and kill the plant.

Understanding and improving soil

Water-holding capacity is determined by the texture of the soil and levels of organic matter. The greater particle surface area of finer soils gives them a greater capacity to hold water.

The 3 main soil types are sand, loam, and clay. Sandy soils drain rapidly; clay soils hold water but make it difficult for many plants to grow; loam soils are between the 2. A soil with plenty of organic matter and a mixture of fine and coarse particles that form into small composite particles (called ‘peds’) is ideal.

Soil testing

A simple test to identify soil type is to take a handful of soil from the garden and add just enough water to mould it into a ball. Test soil from various sites and from different depths in the garden. You can identify which of the 3 soil types you have in different areas:

• Sandy soils crumble and do not form a ball. They are light coloured and have little or no smell. Water drains away rapidly and they are low in nutrients.
• Loam soils form a ball that is friable, usually brown with a pleasantly ‘earthy’ smell. They hold and drain water well and provide good levels of nutrients. Loams are best for plants.
• Clay soils ball easily and range in colour from white to red or dark brown. Clay has fine, dense particles that do not allow water to soak in easily and become hard and resist water when dry. Clays may be high in nutrients that are unavailable to most plants.

Improving soil

Add organic material. The water- and nutrient-holding capacity of sand and clay soils can be improved by the addition of organic matter such as manure, leaf mould, worm farm castings, and compost. Dig in to a depth of 15 to 20cm.

Gypsum and sand added to clay soils help break the clay into clumps, and improves air space and drainage. Add gypsum at the rate of 0.5 to 1.0kg/m². A combination of gypsum, sand, and composted organic matter produces the best results in clay soils.

Chemical additives often produce a quick fix but may have adverse environmental impacts in the medium or long term. Natural methods are better. Make use of organic food waste by using a home composting system or worm farm to supply natural soil conditioner and fertiliser, and reduce waste going to landfill.

Water crystals and soil-wetting agents can increase soil moisture for use by plants. Soil-wetting agents allow water to penetrate dry soil surfaces and prevent runoff; water crystals help store water in the soil.

Finally, hardy, deep-rooted plants can help break up poor soils, and adding composted organic matter encourages microbial activity and worms to improve soil condition and moisture retention.

Watering

Water your garden and lawn early in the morning or evening as this allows water to penetrate before it evaporates. Early morning watering allows plants to use the water throughout the day.

Less frequent, deep soakings train plant roots to grow down into the soil and increase the drought tolerance of plants. Water the roots, not the leaves. Water on the leaves evaporates easily and can lead to scorching. Reduce competition for water by controlling weeds.

Ideally, fertilise plants with organic liquid fertiliser or compost. Dry fertilisers take up some water from the soil and can raise salt levels.

Water-saving equipment and products

Install alternative water supplies such as rainwater tanks and greywater systems refer to Wastewater for more information. A home incorporating whole-of-house water design collects rainwater to use internally and uses it a second time for greywater irrigation.

Poorly designed and inefficient automatic irrigation systems may use more water than hand-held hoses and sprinklers. Automatic systems that are set to turn on, regardless of weather conditions and soil moisture content, waste water. Systems not adjusted to seasonal needs may deliver water too fast, resulting in runoff, or supply more water than plants require.

Drip irrigation is the most efficient system. It delivers water to the roots of individual plants and minimises evaporation and wind drift. Reticulated drip systems are preferable. Install soil moisture sensors that trigger cut-off switches when it rains and adjust watering duration according to soil moisture levels.

Water-storing crystals can hold hundreds of times their weight in water. When mixed with water they form a soft gel and retain a reservoir of moisture for plant roots during dry periods. Some products can be sprayed onto plant surfaces to reduce sunburn and water loss.

Soil-wetting agents allow water to penetrate deeply into soil. Humectants, or moistening agents, attract moisture from air spaces in the soil and are particularly effective in sandy soils.

Photo: Sydney Water

Reduce water use on lawns

Set your mower to cut 4cm or higher. This encourages a deeper root system and the longer grass blades shade the soil, reducing evaporation.

Water only when the lawn is showing signs of stress. Long, slow soakings that allow water to penetrate to a depth of about 15cm encourage a deeper, hardier root system.

A lightly fertilised lawn uses up to 30% less water than an unfertilised lawn of the same grass type. A diluted spray of the liquid drained from your composting worm farm (or purchased from a commercial vermiculture operation) is ideal fertiliser. It returns your waste to the soil and plants.

Beyond the garden

You can reduce your water use in other outdoor activities:

• Use a broom instead of a hose to clean paths and the outside of buildings.
• Wash the car (or dog) on the lawn to prevent water and detergent flowing down the drain. Choose a different place on the lawn each time. Or wash your car or boat at a car wash that recycles water and detergents.
• Save up to 30,000L of water a year by covering your swimming pool and lowering the water level. Swimming pool covers significantly reduce evaporative losses, and an overfilled swimming pool can lose more water through splashing.

Smart Approved WaterMark

Reduce water use outdoors by choosing products and services labelled with a Smart Approved WaterMark. This label is approved for many outdoor goods and services that achieve water savings, as assessed by technical experts. Look for the Smart Approved WaterMark on items and services, or check the database of approved products and services on the Smart WaterMark website.

• Smart Approved WaterMark.
• Smart garden watering, Online calculator to help determine outdoor water savings.

Learn more

• Explore Reducing water use for ways to also reduce your indoor water use
• Review Shading to learn about using vegetation to shade your home
• View Design for climate to discover the best approach for your region

Authors

Original author: Denise Day
 
Updated: Monique Retamal 2013