It has been estimated that up to 50% of all domestic water is used in our gardens and in metropolitan areas it is here that the restrictions have been hardest felt. As you'll see, however, there are things you can do to become more water-wise when planning, planting, reinstating and maintaining your garden, all of which will reduce your reliance on mains water, benefit the environment and make your garden healthy and pest free.
First, let’s define a water-wise garden as one where there are efficient watering practices. This means taking full advantage of rainwater, recycled water, grey water and reducing reliance on mains water. A water-wise garden does not mean a dead or desert garden, nor does it necessarily mean a lawn free garden. In truth, being water-wise means you can have a lush green lawn and healthy abundant vegetation. In fact, many plant problems arise from over watering, not under watering!
Hard surfaces
Take a look at hard surfaces like roofing, driveways, roads, walls, and walkways. They soak up heat like crazy, which then causes the moisture in the soil to evaporate more quickly. Locating trees, covered pergolas and other types of vegetation around hard surfaces will create shade which will cool the surrounding landscape and provide protection from strong summer sun.
Many hard surfaces are designed to channel rainwater quickly and efficiently into the storm water system and then our waterways. There is typically little or no treatment of this water which means that not only does the water leave an area without benefiting the garden, it also washes pollution and litter into our waterways.
In many cases, it would be just as simple to design garden areas so that rainwater gets captured and used in the garden. This can be either by directing rainwater straight into garden areas if soil conditions are suitable or collecting it in a tank for later use. Garden beds should also be shaped and constructed so that they retain water. For instance, if garden beds are not mounded above the paving level then water can flow into them and replenish soil moisture.
Water harvesting and alternative water sources
Rainwater collected from roofs is mixed with debris including leaves, possum droppings and even heavy metals from traffic emissions. However, it is safe to use on the garden with little filtration. To maintain a good quality rainwater supply, a rainwater tank requires good design and installation, and a regular, ongoing maintenance regime. Stormwater collected off other surfaces may contain rubbish, oil, petrol, soil and Salts. It can be used for garden irrigation but some pre-treatment such as a Raingarden is usually required. A Raingarden is a special area of the garden that filters water to remove pollutants before it is either stored for future use or directed back to the stormwater system.
Greywater for diversion can be collected from the shower, hand basin, bath and laundry. It can contain contaminants such as faeces, urine, soil, cleaning products, fats, oils and Salts. Regulations vary throughout the country but in most areas of Australia untreated, diverted greywater can be used for garden irrigation only, and must be connected to a sub-surface irrigation system. All forms of greywater are capable of transmitting disease, and can have a negative impact on your garden if not managed correctly. In many cases it pays to have your greywater tested before starting to use it on the garden to identify any possible problems.
Greywater diversion systems should not be used in areas identified as having major limitations to on-site disposal. These limitations could include heavy clay soils, and an inability to provide an alternative disposal option in the case of on site system failure. Treated greywater systems are also available. These systems remove contaminants from the water and give you better flexibility in regards to how the treated greywater is used.
In all situations it is essential to ensure that you have chosen an option suitable to your needs. Make sure that the amount of rainwater or greywater you can capture makes your choice worthwhile both for the environment and your hip pocket.
Good soil
You can’t have healthy and drought proof plants without good soil. The better the soil the more water and nutrients it will absorb and retain. Different types of soils have different characteristics. Clay, for example, is generally dense and absorbs water slowly, causing run off and water wastage. It can be improved by adding gypsum and organic matter. Sandy soil is gritty and absorbs and drains water quickly. It has a low water-holding capacity, dries out easily, and lacks nutrients. It can be improved by incorporating organic matter and even water-holding crystals. Those people with loamy soil are incredibly lucky as it retains moisture yet drains well making it the perfect soil. In all cases it is usually better to improve the existing site soil, rather than removing it and bringing in new soil.
It’s also a good idea to start a compost bin. This will provide you with free organic matter that can be used in the garden as well as reducing landfill.
Plant selection
The next step is to choose plants that are suitable for the local environment and site conditions. Many of our indigenous plants are beautiful, unusual and perfectly adapted to the climate and any fluctuating rainfall levels. We also have a huge variety of exotic plants we can choose from. A good place to start is to look around your neighbourhood at the trees and other plants that are doing well. Also consider the different microclimates in your garden. You may have a naturally moist area of the garden which is shaded by a tree. This will be the ideal location for plants which originated in dense, temperate forest areas, while coastal plants might be better suited to windy, exposed areas. If you live in an area which enjoys long hot summers but suffers freezing winters then succulents and cacti may not be suitable as they will freeze in winter.
By grouping plants with similar soil, sun and water needs it makes it easier to irrigate your garden, especially if you are only going to water by hand. Your local nursery can help you choose waterwise plants, but remember that these plants will only be water-wise if planted in a suitable area. Another tip is to buy smaller plants rather than larger ones of the same species from the nursery. The small plants will establish stronger root systems and quickly match the size of the larger ones. The best time to plant varies throughout Australia. As a general rule try to plant when temperatures are mild and there is natural rainfall.
Using mulch
The correct use of mulch can reduce weeds, water evaporation and assist in keeping the soil moist and cool. Organic mulches include woodchips, straw and compost. As organic mulches break down they release nutrients into the soil and help to improve its structure, but remember that organic mulches will need topping up annually. Inorganic mulches include sand, pebbles and shells.
Lawn
The use of turf in unsuitable situations is a waste of good garden space, water and money. If you want a patch of lawn, plant it in a location where it will be used. Grass planted in median strips, shady areas or on sloping areas is not generally used much so maintaining turf here doesn’t make sense. These areas are more suited to be used as garden beds.
The use of warm season turf grass can reduce water requirements but be aware that in the cooler parts of Australia, warm season grasses may stop growing and turn yellow in winter. When mowing your grass, mow tall, cutting no more than the top third off the grass. Longer grass slows water evaporation, keeps roots cool and reduces the need for fertilisers. Many lawn grasses will go into dormancy when things get tuff. This is a natural, seasonal variation – there is no reason to feel guilty about it!
Roots follow water gradients in the soil. If watering is shallow then the roots will be concentrated just below the surface of the soil. This makes them vulnerable to heat. Ensure that any irrigation systems used deliver water to where it is absorbed by the plants – the roots. Irrigation systems that use below ground dripper hoses deliver water directly to roots without water loss through evaporation.
Irrigation systems
Irrigation systems should be checked to ensure that there are no leaks and that sprinklers point to where they are required. Automatic systems should be fitted with a rain sensor to ensure that they do not turn on when it has rained and checked to ensure that they are not over or under watering. A good rule of thumb is to wait two hours after irrigation has stopped, go into the garden and dig a hole. The soil should be moist down to a depth of 20cm. A hand held soil moisture probe will also help you to decide when you need to water as it tests the soil moisture level in the root zone.
Watering regime
Plants, like people, are about 80 per cent water so they do need it to survive. A mature deciduous tree will use around 150 litres of water a day. Plants in irrigated gardens can be conditioned to need less water, but it needs to be done gradually. If you have been watering your garden on a regular basis try to stretch out the frequency of watering and slightly increase the length of time you irrigate for. For instance, instead of watering every second day, try every third day, then every fourth day until you can go a fortnight or more. When treated like this, plants will have a chance to adapt to the new water availability.
The same goes for plants bought from a nursery. It is usual in a nursery to irrigate once, or even twice a day. The plants are used to this watering routine. When you plant new plants in your garden you will need to provide them with additional watering until their root systems are established. Gradually, the watering should be cut back.
Plants will tell you when they need to be watered by wilting. If only a few plants in your garden need additional watering think twice about irrigating the whole garden. The final piece of advice is to look at your garden with a keen eye. For the novice gardener being water-wise is like anything new, it takes time, practice and observation to get things right.
About the author: Ruth Czermak is the principal designer at Botanical Traditions, a firm that specializes in sustainable garden design.