Whole Of Site Water Management
Making Every Drop Count
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 bitumen…
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;
Sewage is not discharged from the property, all wastewater is processed on site;
Treated, sterilised wastewater is used to flush the toilet and irrigate the productive garden;
Over two hundred kinds of crop have been cultivated with wastewater containing green cleaners since November 2003.
The rainwater tank overflow enters a land drainage system.
LAND DRAINAGE SYSTEM
Agricultural pipe laid in a gravel bed 70cm below the soil surface. Deeply waters soil. Excess water discharges into the 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
Named after George, a turf loving dog, the lawn is designed to capture heavy rain. The lawn has a caulked mowing strip raised 150mm above the lawn surface. Even the floods of 2011, 2012 and 2013 failed to turn it into a pond. Why? Organic maintenance and compost rich, worm filled soil have performed beautifully. Heavy and persistent rain didn’t run off, it soaked in.
PATHS, DRIVE 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 at the end of Wynnum Creek
- 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 finally – the health of a catchment is an indicator of community pride…
The property covers approximately 813 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 nutrients in soil, like fertiliser, into our street. Street stormwater then enters Wynnum Creek, adding to peak stormwater flows and pollution entering Moreton Bay.
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 – roughly a megalitre per year. We’ve managed to capture, soak up and use most of this water on site, rather than directing most of it into Moreton Bay via creeks and sewage plants.
A 21,000 litre rainwater tank collects roof water. The 150 sq metre roof collects 150 litres for each 1mm of rain that falls. Using rainwater for drinking, washing, cooking (and occasionally gardening) means we are reducing our consumption of town drinking water.
Roof rainwater passes through two mesh filters that line the three rainheads. Filtering removes the tiny ‘pine needles’ shed by our neighbour’s Bribie Island pine trees (Callitris sp.).
Rainwater then passes through a first flush device, one being fitted to each of the three down pipes. These remove the first 1mm of rain falling on the roof, water which efficiently rinses dust and dislodges dirt off the roof. This dirty water is separated and redirected away from the rainwater tank, it soaks into the soil.
When rainwater is used for drinking, it is drawn from the rainwater tank and passes through a ceramic filter and an activated charcoal filter. These remove any remaining biological or chemical contaminants, with the exception of fluorine. Fluorine is a highly toxic compound used in various ways to kill things from rats to bacteria in drinking water.
Chlorine is another toxic compound, related to fluorine. When chlorine contacts organic matter inside town water pipes it reacts to form carcinogenic chloramines. The combination of filters we use remove chloramines.
The rainwater tank overflow carries water into drainage pipe, which deeply waters the soil. Overflow water not absorbed by the soil is discharged into a soakaway pit in the front garden.
The soakaway acts as a temporary pond, passively watering the soil in the front garden. Suspended sediment drops out of the water to line the pit. The soakaway rarely overflows into the street. From experience, if the soakaway is overflowing into the gutter, Wynnum Creek is probably also overflowing onto the end of our street.
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 public infrastructure, the system here avoids using chlorine bleach to treat recycled water. Chlorine breaks down into a persistent carcinogen called chloramine, harmful to anything living. Instead, the system uses ultraviolet light and avoids wasting drinking quality water to flush the toilet – we use recycled wastewater and the system is perpetually 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. Macadamia seedlings, however, have been germinated and grown with it.
We agreed with council to maintain a temporary connection to the sewer, so that surplus recycled water can enter their system as a fail safe. 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, pine bark mulched footpaths in the back garden, and 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. GEORGE’S SUSTAINABLE 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!
For part of each year the lawn is mowed by grazing guinea pigs re-homed from a local cavy sanctuary. An ongoing trial shows one guinea pig can graze 20 sq metres of turf between autumn to early summer. They can overgraze turf in winter, since grass growth slows, but can’t quite keep up with growth in a wet summer, especially when conditions are too wet to permit grazing. They were semi-redundant during the floods of summer 2011.
By capturing stormwater, this step has eliminated another 60 sq metres of our property from generating stormwater, or 7.4% of the site.
Bellis is not adding to the pollution of Wynnum Creek or Moreton Bay’s dugong meadows.
That’s partly because we use ‘green’ cleaning agents for the laundry, shower, sinks, floors, etc; partly because we do not discharge sewage; and partly because we capture and retain pretty much all stormwater that falls on this site. Stormwater carries masses of nutrient rich sediment, and this pollutes aquatic environments.
Examples of ‘green’ cleaners include bicarbonate of soda, washing soda, vinegar, cloudy ammonia, vegetable soaps and genuinely 100% biodegradable detergents. Note that the Australian Standard only applies to the ‘active’ ingredient in a cleaning product.
Standard cleaners, especially laundry detergents, may contain several additives harmful to aquatic environments, like bleach, and these compounds contaminate fragile meadowgrass lawns growing on the sea floor of Moreton Bay.
Seagrass meadows nourish Dugongs, so the less pollution entering Brisbane’s Moreton Bay, the better for everything. Green cleaners are biodegradable and have far less impact on marine ecology.
By using green cleaners at Bellis, the household eliminates most of the typical domestic pollutants from wastewater. Our recycled wastewater isn’t harmful to soil ecology, it’s worm-friendly. I’ve fed the household on crops grown in the soil for a decade. That’s a ten year trial using wastewater containing these green cleaners and using this to irrigate more than 200 different crop.
This household captures, treats and recycles its own waste water, using it to grow food to feed a family.
Just to make sure no nutrients are leaching down hill through our soil, two Banksia aemula have been planted at the lowest point. This species is highly sensitive to phosphorous, and many fertilisers and manures contain enough phosphorous to be lethal to this plant. Their survival testifies that ground water and storm water flowing under their roots from this property contains phosphorous within acceptable levels.
The garden is maintained organically and fed sparingly (apart from bananas, citrus and corn), 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 loss of organic matter and nutrients, 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. Palms produce difficult to compost fronds, so numbers are limited. I culled the Sabal uresana in the front garden because water from the soakaway accelerated growth, and dead frond production.
The amount of water prevented from running off the site into storm drains can’t easily be measured. We can say that, even during the floods of 2011, 2012 and 2013, it’s just a trickle in the heaviest downpours compared to the torrent that used to flow down the drive, ponding under the north of the house.
As a result, the whole of site water plan helps this property to behave more like a natural system. Water is slowed and absorbed by the soil, nutrients and sediment retained, and there’s less stress on Moreton Bays fabulous dugongs and it seagrass meadows.