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Rainwater Harvesting for Drylands and Beyond

Rainwater Harvesting for Drylands and Beyond

I HAD A DISTINGUISHED VISITOR staying at my little shack this week, and I’ve had the good fortune to watch the video CD she left me. It’s all about her Blue Mountains house, how she retrofitted it and how she developed her small garden and designed it and her home to make the most of water. And it’s water, not that retrofit video with its home-spun, permaculture design know-how that is the focus of this review.

Although Rosemary Morrow’s video is the focus of a different article, it is pertinent to the book I want to write about. I had seen her garden in construction and looked curiously at what seemed to me to be a rather large hole that she had dug. As I watched her video, I came to understand the logic of that hole and its role in the curious earth-shaping exercise she had been undertaking when I visited. As it turns out, those backyard earthworks were all about harvesting, detaining and infiltrating into the soil the rainfall that comes onto and flows through her site.

It is this that Brad Lancaster’s book, ‘Rainwater Harvesting for Drylands and Beyond’, is all about. The book arrived unexpectedly in my mailbox just before Rosemary arrived on my doorstep, and that was a fortunate coincidence. Like Rosemary, Brad is no stranger to the practice of permaculture design, and that shows through rather plainly in the 179, well-illustrated (illustrative drawings and black and white photographs) pages of his large-format softcover. Oh, and Brad’s book isn’t just for the permaculture demimonde; it’s relevant to virtually all Australian cities and towns below the Tropic of Capricorn, including the better watered but recently drought-affected big cities. It’s also for those comparatively few Australians who derive a living from our often-parched soils, a description that doesn’t really do justice to our farmers west of the Great Divide who are now into their tenth year of drought.

The swale, or infiltration trench, at Fairfield City Farm in south-western Sydney details and infiltrates rainwater running downslope.
The swale, or infiltration trench, at Fairfield City Farm in south-western Sydney detains and infiltrates rainwater running downslope.

Let’s diverge. Australian governments, the whole three layers of them (whether that’s one too many is a different debate) have made great strides in encouraging individuals, companies and even government itself to take water-conserving measures. We now get rebates for installing water tanks and even bigger rebates is we have those roofwater tanks plumbed into our toilet flushing and other domestic systems.

The ban on urban watertanks that existed just 30 years ago definitely was in another country, another time, another mindset. Even the Manly Council Art Gallery down the road from me has a line of rainwater tanks the full length of its rear wall. And local government sustainability education programs feature water conservation… all about harvesting, storing and using the stuff carefully. The ‘Living Smart Action Guide, a 300 or so page manual I am writing for a local government sustainable living course, has an entire chapter on how urban people can make best use of water, and the topic is taught in the course by a water engineer knowledgeable in all aspects of water harvesting and use, including greywater. This indicates the seriousness of the local government interest in water conservation in our sometimes parched metropolis, and it suggests why Brad’s book is one for the times.

A mine of how-to

Back on topic again, and we find Brad’s book a literal mine of how-to information. Yes, I know he’s a North American and that the peculiar Imperial system of measurement survives in this country, however… good news… Brad has been thoughtful enough to supply critical figures in both Imperial and Metric. The plants he mentions, of course, are not relevant here, but I’m sure that readers will be smart enough to devise their own species list.

So, what’s in this book for we southern hemisphere dwellers? First, there’s the eight rainwater harvesting principles. The first might sound a little familiar to practitioners of permaculture design because it’s about beginning with long and thoughtful observation. It’s about understanding what goes on on our site, which is knowledge gained through the dual process of observing what happens and asking why it is so… why do those plants grow here? why is this soil moister than elsewhere? why does rainfall runoff flow this way and not the other? why is this area eroding?

Reading this, it reminded me of the Action Research process I have used in projects. That is based on the idea of look > think > act – look and observe to understand what is happening (more formally, this would be called baseline data collection in project management-speak), analyse it by thinking and learning about it, then act to design and develop the project. Call it what you will, observation reveals sometimes hidden processes and features in the landscape, whether that is of a farm, an urban garden or what is to become an community food garden in the suburbs. ‘Observe and contemplate’ is the rather nice way that Brad puts it.

His second point of advice – his second principle – is to start thinking about water flow and how you might interact with it at the highest elevation of your land. It is from here that we begin our interaction with rainfall and overland flow and channel it into detention structures such as bunds (raised ridges), detention ponds and infiltration trenches or contour ditches, also known in permaculture-speak as ‘swales’.

Brad’s third principle is to start small and simple, a suggestion that resonates with David Holmgren’s permaculture principle about small and slow solutions. Although I think there are situations when we need big and rapid interventions, the principle is one borne out in a development program I have had a long association with in the Solomons Islands. There, the principle was field rested and found to offer manageability and, as Brad suggests for water projects, reduced maintenance over time.

Domestic rainwater tanks come in a range of sizes, shapes and materials. This flatish, galvanised iron tank was installed at the home of Keelah Lam, from Manly Food Co-op.
Domestic rainwater tanks come in a range of sizes, shapes and materials. This flatish, galvanised iron tank was installed at the home of Keelah Lam, from Manly Food Co-op.

The fourth principle is about infiltrating water into our soils, which is accomplished by slowing and detaining overland flow so that it has time to sink into the soil where the roots of our plants can get at it. This leads nicely to the next principle, that of planning an overflow route for the excess water that falls during prolonged rainy periods or storms. The cost of not doing this is erosion. Spillways should take water to a larger infiltration zone or, more likely in the city, to storm water drainage. While this might seem a waste, we are responsible for the downstream impacts of our earthworks and water harvesting installations on other properties, so we don’t want excessive water flows entering them. In the city, inattention to this could lead to a visit from your local council officer.

Overflow routes or spillways should be reinforced against erosion by planting them with a mat-rooted species, perhaps a variety of durable and drought-resistant grass, or by paving them with closely-packed stones, known as rip-rap. Brad talks about moving water from retention basin to basin in a stepped progression down our site, assuming we have the slope to start with.

He also talks about maximising planted groundcover because this, too, slows, detains and helps to infiltrate runoff. Plant roots also pump soil water towards the soil surface, and the leaf fall eventually forms a mulch that breaks down to add the organic matter that keeps our soils open and porous. Maximising groundcover is Brad’s sixth principle.

His seventh will be familiar to permaculture designers because it’s about stacking functions. This links with the principle of designing for multifunction, which appeared way back in Bill Mollison and David Holmgren’s ‘Permaculture One’. Brad talks about constructing contour bunds, which are earthern mounds made along the contour, so that they act as paths providing access through the garden. Bunds, of course, are a water harvesting technique. He discusses other strategies to increase productivity and make best use of limited space, and one of them I see if I look out of my window. It’s a trellis that makes use of the side of the rainwater tank and, currently, it supports a scrambling and largely unproductive pumpkin vine.

The final principle is an important one, that of monitoring your water works and continually assessing their performance. This discloses where improvements can be made and is a way of learning more about your landscape. It applies the philosophy of the continuous improvement of design to water systems.

The possibilities of techniques

The first swale I saw in action, actually working that is, was when I was a Landcare educator at Liverpool Council’s Fairfield City Farm in south-western Sydney. It was carved into the sticky clay soil of the urban permaculture demonstration garden and it held water well and separated the vegetable garden from the fruit and nut orchard planted immediately below its berm. As water infiltrates, swales (and, presumably, berms) form an area of moist soil immediately below and this slowly moves downslope under the influence of gravity. It is this that the roots of those fruit and nut trees accessed. The next swale I came across was the set at Habitat and Harmony Community Garden in the lower Hunter. These, too, worked well and were full of water when I first saw them.

Swales are something that long ago caught the imagination of perma-folk and now we find them from farm to suburban backyard, however they are only one of many water harvesting earthworks. We’ve already mentioned berms, which, unlike swales that are incised into the soil, stand mounded along the contour above it. There are mini-catchments, too, such as the ‘boomerang’ bunds Brad talks about — they are smaller, curved, low-raised berms made on gently sloping land. He also mentions basins, another excavation and one made around trees in dry climates. You can see some, well mulched and with their berm planted to banana, at the Yandina Community Garden on the Sunshine Coast.

Also mentioned in his book are terraces, which are really a means of turning a steep hillside into a stepped series of smaller, flat strips for cropping. I was introduced to them by Badri Dahal, now living in Sydney but then with the Institute for Sustainable Agriculture Nepal, when he gave me a copy of the book, ‘Sloping Land Agriculture’. I was impressed when, in the early 1990s, I encountered a low hillside of terraces at the Angel Street Community Garden. Brad suggests low-raised walls to boost their water harvesting capacity.

Swales don’t drain

Despite their popularity, there remains confusion about swales in permaculture circles. It is due to the misunderstanding of this fact: swales hold water, they do not drain it away; drainage ditches or channels move water from one place to another, such as to a dam. Drainage lines are excavated with a gentle grade, swales are flat along the contour — at the same height, that is — across the land.

Sometimes, but only where large enough and where the soil is deep enough, they have pits dug into them at intervals that act as cisterns to hold water and allow it to infiltrate. This is mentioned in Brad’s book, too.

And so much more

There’s an informative, illustrated chapter on site analysis for the home and garden. Site analysis, and its accompanying needs analysis of those who will live on-site or make use of it if it is something like a community garden is the staring point of design, as many reading this will know. There are also formula for calculating harvest capacity, boxes of interesting information and pages with scaled grids for doing your own design.

Brad Lancaster’s is the first of his three (so far) books on water. Rainwater Harvesting for Drylands and Beyond, Volume 1, leads to Volume 2, which is all about earthworks. Volume 3 covers roof catchments and cisterns — water tanks to us. I’ve seen Volumes 1 and 2 in Sydney bookshops (Gleebooks and Kinokinoya stock them) but I’ve not yet come across Volume 3. They are distributed in Australia by Tower Books in Sydney, so would presumably be found around the country.

Ours, we know only too well, is a dry country likely to become drier as climate change makes itself increasingly felt, especially in the south east. That is why, even in the cities clinging to our coasts, Brad’s manuals are potentially useful. What they do is take the ‘enrich soil + mulch’ message of permaculture and local government sustainability educators a step further to shaping the ground to get the most from the rainwater that runs over it.

Now, a note of caution. Get advice in land shaping if you do not really understand what Brad is about or the hydraulics of your site. Consider your downstream neighbours and what happens to water leaving your land and entering theirs’. This is what Rosemary Morrow did before she reshaped her land to harvest water and, if she — one of this country’s most experienced permaculture educators and designers — does this, then it’s only common sense that we do too.

So, should you invest your scarce dollars in this book and, perhaps, in Brad’s other volumes? I suggest the answer is ‘yes’. You will just have to apply a little observation and reasoning to adapt them to Australian conditions. Again, if you don’t feel confident doing what he describes, get help from a competent and experienced permaculture or landscape designer. These are manuals for our parched times and gardens. They are easy to read, easy to understand and it is evident that they are written from the knowledge that comes of experience.

Publishing details

Lancaster B; 2006/2008; Rainwater Harvesting for Drylands and Beyond, Volumes 1; Rainsource Press, Tuscon USA; ISBN 978 0 9772464 0 3.

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