November 2003. Our first rain in Queensland. Water roared down the drive to the north and ponded on the concrete slab underneath the front of the house before spilling out to the street. The soil was so compacted it acted more like concrete…
A Whole of Site Water Management Plan at a Glance
21,000 litre in-ground tank. All rain falling on the house is harvested.
Modified Aqua-Nova aerated wastewater system. A sand and gravel filter and a UV steriliser replace a chlorine injector. All wastewater from the house is processed here. Treated wastewater is used to flush the toilet and irrigate the productive garden.
Enters land drainage system.
LAND DRAINAGE SYSTEM
Agricultural pipe laid in a gravel bed. Deeply waters soil. Excess discharges into soakaway.
Gravel lined pit planted with local native swamp plants. When full water soaks into the ground in less than four days – faster than the puddles on the grass verge opposite. The original roof drain acts as an overflow into the street.
George’s sustainable lawn has a caulked mowing strip raised 150mm. Heavy downpours – if we ever get any – will turn it into a pond so that water will soak into the soil and not run off.
PATHS AND NURSERY AREA
All water permeable surfaces. Gravel in the ornamental garden and nursery, woodchip mulch in the productive garden.
Background and Benefits
Brisbane City Council states that it has the following environmental objectives:
- To reduce stormwater flows
- To reduce stormwater pollution and
- To reduce drinking water use
We’ve used these as guiding principles in setting up ‘Bellis’. Some practical benefits that could result for the Wynnum Creek Catchment if more businesses and residents did what we’ve done:
- Reduced risk of homes along St Catherine’s Terrace flooding
- Reduced risk of the road junction between Collina St, Daisy St & Berrima St flooding
- Reduced creek bank erosion along Wynnum Creek between Tingal Rd and Fox St
- Reduced weed invasion of the catchment
- Improved stormwater quality
- Healthier soil, healthier plants – which means healthier wildlife and a greater variety of it too
- Reduced costs for dredging silt out of Oyster Point for the boat navigation channel
- Reduced costs for desilting stormwater systems
- Reduced costs for threatened species programmes
- Reduced insurance premiums and costs for repairs
Of course Moreton Bay is the destination of what flows through our catchment, a wetland of international significance under RAMSAR, a convention on wetlands
(see: www.ramsar.org andwww.wetlands.org/RSDB/default.htm).
And the health of a catchment is an indicator of community pride.
The property covers approximately 815 sq metres, of which:
- The roof covers 18.4% of the property
- Paths and driveway cover 26.5%
- Garden beds cover 42%
- Lawn covers 7.4%
- The rainwater tank roof covers 38.5 sq metres, or 4.7% of the property
Total = 99% of the property
The remaining 1% unaccounted for includes a 3 sq metre, raised gravel plunge bed for growing potted succulents, which drains all water, and occupies 0.36% of the site.
STEP BY STEP
1. THE SITE & RAINFALL.
Originally the roof shed all rainwater directly onto the garden. The garden then shed water, carrying soil and any nutrients with it into our street. The street’s stormwater enters Wynnum Creek, adding to peak storm flows and pollution.
We use a rain gauge to keep rainfall records. From 22.11.03 (when we arrived) to 19.2.06 our 815 sq metre property has received 2,769.9mm of rain. For each 1mm fall our property receives 815 litres of rain. This means that between 22.11.03 to 19.2.06 our site has received 2,257,468.5 litres of rain. We’ve managed to capture and use most of this on site, rather than allowing most to flow into Wynnum Creek.
A 21,000 litre rainwater tank collects roof water. The 150 sq metre roof collects 150 litres for each 1mm of rain that falls and using rainwater for drinking, washing and gardening means that we are reducing our consumption of drinking water too.
A soakaway acts as a temporary pond, collecting most of the overflow from the rainwater tank. Tank and soakaway are connected by drainage pipes.
This one step has stopped about 18.4% of our site from generating stormwater.
A sewage system treats and recycles all household waste water. No sewage leaves the property. The toilet only uses recycled water. Excess recycled water irrigates the garden.
Unlike the council our system avoids using toxic chlorine bleach to treat our recycled water. We use ultraviolet light. Chlorine breaks down into a persistent carcinogen called chloramine, harmful to anything living. And our system avoids wasting drinking quality water to flush the toilet – we just keep on recycling it!
In heavy rain sewage plants are designed to overflow, sending their excess water and sewage (the ‘overburden’) into local creeks. Gardeners in the nearby suburb of Lota know what it’s like to have council overburden rushing across their patch. By treating our waste water on site we are doing our bit to reduce the public health risk posed by overburden.
We started collecting data on the flow of recycled water through our sewage system on 19.8.04. Between 19.8.04 to 19.2.06 the flow meter records that our system has processed 153,000 litres of waste water, an average of 321.3 litres each day. The recycled water contains some phosphorous and nitrogen, so it’s unsuited for irrigating phosphorous sensitive plants in the Proteaceae family (Protea, Leucodendron, Grevillea, Banksia, Alloxylon, etc) and probably orchids as well.
We agreed with council to maintain a temporary connection to the sewer, so that surplus recycled water still enters their system. We’re still paying rates for council sewage services, but we’ve saved them the cost of treating 153,000 litres of waste water, which in turn has extended the life of council infrastructure.
3. PERMEABLE SURFACES
Hard surfaces such as paving, driveways and footpaths instantly shed stormwater, adding to stormwater flows in catchments. We use a rain absorbing gravel footpath in the front garden, mulched footpaths in the back garden and have a gravel lined driveway.
The little used footpath in the front garden allows some rainwater to pond in it during heavy rain, further reducing stormwater losses. Together, driveway and footpaths help rain to water our garden, and have reduced stormwater entering Wynnum Creek. This one step has significantly, but not completely, reduced stormwater losses from 26.5% of our property.
4. SOIL IMPROVEMENT
Our soil has been prepared to receive brief, heavy falls of rain. See our garden page for details.
In organic-rich soil worms, dung beetles and a myriad of microscopic soil life lend plants a helping hand, fighting disease, releasing nutrients – and helping air and water enter the soil. Organic matter decomposes, so it is supplemented regularly. Organic-rich soil acts like a sponge, soaking up and storing water even in dumping rain, then slowly releasing moisture as plants need it.
The plan maximised the area of organic-rich, water absorbing soil. In June 2005 the garden received 123mm of rain in four hours. Every bed soaked it up. Even the lawn didn’t flood!
Lush ornamental and productive gardens need use little drinking water. Our reward has been gardening with few interruptions by watering restrictions – or our continually surprising climate.
The plan anticipates wet weather. By raising beds and levelling surfaces, we have reduced runoff and ponding and helped drainage. Raised beds assist air to re-enter soil, reducing the incidence of root diseases during persistently wet weather. Most moisture-loving plants prefer well-drained conditions.
The vegetable and herb beds are raised 150mm above ground level (above). In the last two years we’ve had 22 brief, dumping falls of rain. Five were between 60 and 123mm and these justified raising those beds: zero runoff and no plant deaths. This step has almost completely eliminated stormwater losses from 46% our our property.
5. THE FLOODING LAWN
George’s Sustainable lawn is of Durban grass, also known as Sweet Smother grass, Dactyloctenium australe. It was laid in February 2005. The new turf was watered during laying and then for the next two months, but waterings were gradually reduced in frequency and volume. This allowed the turf to establish and harden up. Since then the only water it gets is splash water (when I’m watering nearby plants) and a once monthly foliar feed with seaweed fertiliser. Otherwise the lawn isn’t watered. The one big fall we had in June 2005 kept it green until mid-October 2005. Four times between January 2005 and February 2006 sections of it have gone brown, but most of the time it’s green and growing.
The lawn is roughly level, to reduce surface water movement. Instead of having a normal timber mowing strip to contain grass runners (so they don’t invade adjacent garden beds), our lawn is enclosed by a timber edge that’s 150mm above ground level. All the joins between timbers have been sealed, effectively creating a catchment area. If we do get serious, dumping rain in theory this can collect a 150mm fall. Just what happened in Melbourne in one hour in January 2005. So our lawn could become a temporary pond…here’s hoping!
This step has eliminated another 60 sq metres of our property from generating stormwater, or 7.4% of the site.
We use ‘green’ cleaning agents for the laundry, shower, sinks, floors, etc. Examples of ‘green’ cleaners include bicarbonate of soda, washing soda, vinegar, cloudy ammonia, vegetable soaps and genuinely 100% biodegradable detergents (the Australian Standard only applies to the ‘active’ ingredient) . These cleaners eliminate most of the typical household pollutants from our wastewater, which means our recycled water isn’t harming the garden soil, crops, or polluting our catchment via stormwater.
The garden is maintained organically and fed sparingly, further reducing the risk of stormwater and catchment pollution.
Crops and ornamentals with weed potential are composted on site – we regard sending garden prunings to the tip as a failure, but it hasn’t always been possible to do this 100% of the time. Plants with weed potential (almost all plants have some weed potential) are managed to prevent escape into our catchment. An example of a crop with weed potential is Lemongrass, Cymbopogon citratus, and these have their flowers removed to prevent self-seeding.
The amount of water prevented from running off the site into storm drains can’t easily be measured. We can say that it’s now a trickle in the heaviest downpours compared to the torrent that used to flow down the drive to the north of the house. As a result of our whole of site water plan the site behaves more like a natural system with water being slowed and absorbed by the soil, so there’s less stress on Moreton Bay.