Nature's Water Economy

A vast planet-wide system of water collection, storage, purification & distribution

By Lawrence Gamble, M.U.M. Sustainable Living Dept

Savvy Veg: This is the long version of Lawrence Gamble's shorter article on rainwater collection, which appeared in the April 2006 print edition of The Iowa Source.

The shorter Source article is specifically about collecting and using rainwater, while this longer article is more informative about environment, permaculture landscape, the natural water economy, and the historic context of water.

The hydrological cycle is a vast planet-wide system for purifying and distributing water.

Redesigning Landscapes to Store and Purify Water

Water is evaporated in the oceans, across the land, and through the transpiration of plants. Water is cleansed, energized, and mineralized by flowing through the biota and rushing down streams.

The energy required to operate the hydrological cycle is thousands of times greater than the energy used in the economy of man. It has been operating autonomously for billions of years, driven entirely by sunlight that hits the surface of the earth every day. This system is so old and so vast that, through water, we are connected to the rest of the earth and the rest of life across and through time.

Man Made Not As Efficient

The spring rainfall, the mountain stream the forest, the deep roots of prairie plants, the marsh and wetland, the underground aquifer: this is how nature purifies water.

In contrast, man purifies water using expensive machinery and toxic chemicals. The water is dead and the proces takes lots of energy. Chlorinated tap water will kill your pet fish and diminish the beneficial microbial life in your soil.

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We can use nature as a mentor and model for how to treat water, making man's economy more in tune with the greater economy of nature, of which it is a small subpart.

Abundant Water From Rain

Huge amounts of naturally purified rainwater falls on urban landscapes. A small Iowa city like Fairfield gets 3.6 billion gallons per year, almost 400,000 gallons for each man, woman, and child. The hard, impermeable surfaces of most urban landscapes (and most conventional farmscapes) cause most of this water to run off all at once rather than being absorbed, purfied, stored, and released slowly. This run-off is polluted from roads and excess lawn and agricultural chemicals.

Surplus nutrients from conventional farming in the Upper Midwest are responsible for a dead zone in the Gulf of Mexico, an area incapable of supporting aquatic life that in the summer becomes as large as the state of New Jersey.

The good news is that we can design urban and farm landscapes that purify, energize, and store water.

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First, we should get the toxic chemicals and excess nutrients off our landscapes so we don't overwhelm the ability of natural systems to treat and absorb water.

After this, the key to treating water in the landscape is to slow the flow of the water and to increase the permeability of the landscape. This allows the water to do some useful work for us and for nature before it eventually reaches the ocean. The landscape of Southeast Iowa, with its rolling hills and retentive clay soils, is ideal for creating these kinds of systems.

Swales Are Swell

One classic technique for slowing the flow of water across the landscape is the swale. Swales are ditches that are dug on contour across a landscape. On a larger scale, terraced farmland functions in the same way, but you can use the identical principle in your backyard. As rainfall flows across the swale, the water has a chance to be absorbed by the ground. If your plant your fruit trees on the downhill side of a swale, for example, they will automatically be able to use this stored ground water in times of drought.

Swale systems built in the American Southwest over 60 years ago by the Civilian Conservation Corps still function today, providing oases for plant and animal life. Many of these systems have functioned without any maintenance since their construction.

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Creating Permeability

The next step after slowing the flow of water across the land is to make the landscape more permeable so that it can store water. This allows the landscape to minimize the damaging effects of high rates of rainfall by storing and slowly releasing it. It also allows the biology in the upper layers of the soil to have time to treat the surface runoff.

In the swale example above, we could plant the swale with deep-rooted perennials like prairie plants, some of which have roots that are many yards deep. For example, Blue False Indigo, Baptisia australis, grows only three to five feet tall, but the roots may go down 25 feet! Every year, some of these roots die off and leave channels that allow water to penetrate even the tightest clay soils. Millions of gallons of water can be stored in an acre of ground this way. The decomposing roots enrigh soil, making it more fertile and absorbent. The root systems also hold soil together and help prevent erosion.

Native prairie landscapes can absorb rainfalls as great as 10 inches per hour with very little run-off. In contrast, the conventional cool-season grasses that have largely replaced prairie grasses in most of Iowa have shallow roots, measured in inches rather than yards. Rainfall as little and inch an hour will cause run-off. These grasses have little ability to absorb and store water.

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In areas where native prairie still exists, streams tend to flow in moderate amounts all year long, rather than to have huge flushes of water in the spring and drought in the summer. Stream water temperature is cooler, and often supports a greater diversity of life. This ability of prairie plants to absorb and store water is so powerful that some Midwestern comunities require prairie to be widely planted - even in yards - because it saves money on costly conventional stormwater systems.

Softening the Urban Hardscape

We can also make the urban hardscape (i.e., roads, buildings, parking lots) more permeable. New kinds of paving such as grass pave, permeable block paving, and permeable asphalt allow water to penetrate and keep the ground from becoming compacted by people and cars. Parking lots can become underground storage reservoirs holding millions of gallons of water. The parking lots can then be planted with trees, making them cool and lush.

Rain Gardens

Impermeable surfaces like driveways (even gravel driveways are essentially impermeable) can be fitted with rain gardens, which are specially designed to allow water to be absorbed into the ground. A rain garden that can handle all the run-off from the impermeable surfaces of a typical home, driveway, and yard ranges from 100 to 400 square feet in size.

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Typical rain gardens have habitats for plants that range from wet to quite dry, so a diversity of beautiful plants that you don't have to water can easily become part of your landscape.

You can slow the runoff from your roof by building a living roof or creating a rainwater storage and collection system to provide a water supply for your home and gardens.

Planted Rooftops

Living roofs consist of a planting medium and plants that can absorb and slowly release rainwater. From the air, your house can look like a meadow. Some German cities with dense impermeable landscapes and flooding problems require all new buildings to have living roofs. Living roofs look cool and actually keep your building cooler.

In Chicago, for example, two municipal buildings face each other - one with a living roof and one without. On hot summer days, the living roof is 70 degrees cooler than the conventional roof. The living roof, about an acre in size, has been made into a city park and recreation area. It has become such a tourist attraction that when I tried to visit it last year I was told there is a six month waiting list. The City of Chicago now offers $5,000 to building owners who put in green roofs.

Natural Swimming Pools

Finally, I'd like to mention natural swimming pools, a form of 'living machine' where biology and mechanical components work in harmony together. Natural swimming pools use plants and microbes (actually, the microbes that colonize the roots of the plants do most of the work). Crystal clear water can be maintained without chemicals, and existing pools can be retrofitted.

Natural swimming pools are a more diverse version of the Iowa farm pond. One section of the pool is shallow, planted with marsh and wetland plants from the region. Pool water continuously moves through this area and through a bed of gravel, providing a place for water-cleaning microbes to grow. More common in European countries like Germany, France, and Great Britain, natural swimming pools are just starting to gain popularity in this country. You could build a small version as a garden pond to provide havitat for frogs and beneficial insects.

The Politics of Water

There are social and economic justice issues that cloud any discussion about the wider availability of clean water to humanity. Some people think that the next century's wars will be about water rather than oil. Only 2 to 4 percent of the earth's water is fresh, and of that only about.3 percent is available for use.

According to the BBC, over one billion people live without access to clean water for drinking and washing. It woiuld take a ridiculously small amount of money from wealthy Western countries - less than the cost of one year of the Iraq ewar - to make this basic human right available to everyone. Future generations will look on ours with shame that we did not accomlish this and the transition to renewable energy sooner.

While we might not be able to do much to change the dominant form of agriculture in the Midwest, we can all become responsible for the rain that hits where we live. Build a rain garden, dig a swale, plant a living roof, create a natural swimming pool with your neighbors.

A comprehensive water-in-the-landscape plan could save your community millions of dollars on conventional stormwater systems, will work better, and will create more beauty and diversity in the landscape. Our water can then begin to be managed by the unlimited intelligence of nature, rather than the limited intelligence of man. It can bring an element of wildness into the too-domesticated urban landscape.


Learn more about using water wisely and other aspects of environmental design at Big Green Summer, a 10 week summer immersion program in creating sustainable communities, offered each summer.

Rainwater Collection Over Texas: Service, systems, supplies. San Marcos, TX, Tel: 800-222-3614

Rainwater is an abundant, high-quality, and versatile water supply. See Solar Farm for photos, references, and more information on rainwater collecting.

Harvest H2O Harvesting the Rain Rainwater Collection

Rainwater Collection For The Mechanically Challenged - Book and Video

Economic Security for Spaceship Earth, by Jim Bell. Excellent book by San Diego environmental designer and mayoral candidate Jim Bell. It details how even San Diego could be water self-sufficient with the wise use of rainwater.

Rainwater Harvesting: The Collection of Rainfall and Runoff in Rural Areas, by Arnold Pacey, Adrian Cullis. Great book, designed for third-world applications.

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