The following interactive infographic gives highlights of the recent ridgepoint dam construction at Circle Organic Community Farm.

If you’re reading this, you probably love water-harvesting earthworks. When done right, they can start repairing damaged land right from the first rainfall after they are installed. When done wrong, they can waste a lot of money, or even put lives and property at risk.

Here are six things to keep in mind when planning earthworks for a site.

1. Slow it down

The point of harvesting water is grabbing it and holding it as long as you can before it escapes you by going off your site. The longer that water stays on site, the longer it is available to you. Whether you are choosing open storage, or directing it into the ground, your aim is to make it stay around longer.

It’s worth mentioning a curious misconception that some people have. Some folks have the idea that if you slow water on your site, you are taking it away from anyone downhill, leaving them with less water. This is not at all the case at all.

Allowing runoff rather than capturing it is generally a no-win situation. To regreen a water-starved place, would you encourage water to rush down off the hills as quickly as possible so that all the downhill people could have it? This, in essence, would be designing the land to make water travel out to the ocean as quickly as possible. Not only is this a recipe for erosion, it is a recipe for turning permanent rivers and streams into ephemeral ones that only flow during heavy rains.

With earthworks, you are rehydrating the landscape. Rehydrating the landscape means more water available more often for the people downstream. While they might see a temporary reduction in surface runoff in the short term, in the medium and long term they will have more groundwater available.

2. Safety

Nature will throw enough adversity at you without adding to the list by creating your own disaster. A good risk assessment will help you to make wise decisions. Here are some questions to keep in mind before bringing in the machines.

• How might this kill somebody?
• How might this damage property?
• What happens if there is a catastrophic failure?

Though you may be eager to install a particular feature on a site, safety might dictate that you walk away and leave the site untouched.

3. What does the land want to do?

You might have some exciting ideas about what you would like to see installed on a piece of land, but it is not going to work out very well if the earthworks do not suit the site you are working on.

A great perspective to take when deciding what to do is taking the land’s perspective. What does the land want to do? To answer that, consider what the environment was like before human intervention. That will give you some insight into the most optimal techniques to use on your site.

What the land will do depends on:

• Climate
• Topography
• Soil type and depth
• Local flora and fauna

Consider what the site would look like if it were just left alone for 40 years. How would it change over time?

Once you know the direction the land will naturally head, you can choose an approach that will steer it in that direction, rather than fight against what the land naturally wants to do. Nature rewards partners and punishes dictators.

4. Think like water

Bruce Lee wanted you to have a mind like water. I want you to think like water.

If you are water there are a few things you will do such as evaporate, or freeze, but the most important one with respect to earthworks is that you travel at 90° to contour. To put it another way, you flow downhill. (It’s true that if you are flowing through something, you will favour easily traversed mediums like sand over something denser like clay. In this case when travelling through soil, you might go at an angle less than 90o to contour. For planning purposes, however, 90° to contour is the rule.)

With this in mind, how will you, water, travel across the land? What path will you take? Check the land. There might be clues as to where you have travelled before – evidence of erosion, or of sediment building up. This can help you to make decisions of what to place where.

How much water will there be at one time? Not only do you need to know where the water does and doesn’t go, you also have to know how much there is at one time. How big do the water-harvesting systems need to be? What happens if you get more water than expected?

5. Know what earthworks do what jobs

There are a lot of choices when it comes to earthworks, choosing the right one for a site means that your efforts will go further

If you read your site correctly, it will go a long way towards determining what you can or should do on a site. Soil type, for instance, will determine what will be effective and what will not. As an example, ripping with a subsoiler such as a Yeoman’s plow can be very beneficial. It would be pointless to run one on sand or on lateritic soil, however. In the former case, the sand will just fall back in on itself. In the latter case, the land will flow and “heal” the ripping with the first rainfall (assuming you had the horsepower to get the power to break through the soil in the first case).

Next, you need to know what each type of earthwork does. For example, swales intercept water, sending it into the ground. They are great for sending runoff into the ground and helping trees to establish, but they won’t do much of anything at all for garden beds.

Do you want to get more water in the ground, or do you want open water storage? The answer will depend on your climate and what you are trying to do. If you were in an arid environment, you wouldn’t want a lot of open water storage, which would just be subject to evaporation. If you were in a humid temperate or tropical climate, open water could provide backup irrigation as well as opening space for aquaculture.

6. How much money do you have?

You can make a grand plan, but do you have the money to pay for it? You might have to implement things in stages. Hiring a tractor to pull a subsoiler is very affordable. Digging swales is affordable and has a high return on investment, if you are using them for the right thing in the right place. Installing a dam is a higher investment that will take considerable machine time, and thus more money.

You also have a choice of machines to work with. The hourly rate of a backhoe is cheaper than that of a bulldozer. If you are in a humid temperate environment, you can cut in a swale with a bulldozer in a small fraction of the time a backhoe could. If you were in a semi-arid environment with hard, lateritic soils, even if you could cut through with the dozer blade, the swale you made would be far too small and would just be erased with the first big rain event.

Over to you…

What approaches do you take when designing water-harvesting earthworks? What snags and solutions have you encountered with your projects?

Sensationalist title, yes, but unfortunately swales can cause damage, or even loss of life. When designing and building earthworks, “Don’t kill people” should be your first rule. I’m going to highlight 3 situations in which these water-harvesting earthworks could be dangerous and perhaps even fatal.

You’ve Heard of Quicksand. How About Quick Clay?

When I get a call from a client who is east of me inquiring about earthworks, I immediately head for a soil map. The reason is that much of Eastern Ontario was covered by the Sea of Champlain around 10,000 years ago. Here silt, clay and organic matter were deposited in the sea’s saline environment, leaving a deposit of a particular kind of clay known as Leda clay, quickclay, or Sea of Champlain clay. The salt in the water acted as a cohesive agent. When the sea disappeared, this clay was then exposed to fresh water from rainfall, washing away much of the bonding properties of the salt, leaving the very unstable structure of the Leda clay.

Under pressure, or sometimes when highly saturated with water, Leda clay can liquefy – something which has triggered a number of landslides in Eastern Ontario. If you place a swale somewhere, you are going to make the ground downhill of the swale wetter. This creates conditions that could make the ground unstable, triggering a landslide.

So what do you do in this situation? I don’t have any set rules. I look at the need for swales and if other approaches would suffice. I also look at the slope and the likelihood that the land might slide. (Keep in mind that these slides can cover a lot of area and might start a long distance off site.)

In some situations, swales just might help prevent damage. Leda clay contracts a lot when dry, which can lead to foundation damage. If sliding is not a danger, you might help a building keeping the ground hydrated with swales. Personally, I’d look to preserve moisture with mulch and ground cover in those situations, just to be safe.

In short, Leda clay makes me nervous. I’ve yet to install or recommend any swales in these situations. If you’ve had any experience dealing with quick clay, I’d love to hear about it in the comments, or via the contact form.

Video by Christian Olsen.

Trouble in Paradise

Swales can trigger landslides in tropical highlands. These hilly areas get tremendous volumes of rainfall. Forcing more water into hillside soils in these regions can trigger a slide, even when they are forested. Consider the following passage from Jared Diamond’s Collapse:

[O]ne European agricultural advisor was horrified to notice that a New Guinean sweet potato garden on a steep slope in a wet area had vertical drainage ditches running straight down the slope. He convinced the villagers to correct their awful mistake, and instead to put in drains running horizontally along contours, according to good European practices. Awed by him, the villages reoriented their drains, with the result that water built up behind the drains, and in the next heavy rains, a landslide carried the entire garden down the slope in the river below.

These are areas of 3 or more metres of rainfall a year. There’s no problem with available water in these regions. Don’t risks potentially deadly landslides by floating mountainsides with swales.

Swales to Stop a Leaky Basement? No

As mentioned above, swales make the area downhill of the swale wetter. I had someone near the waterfront in Toronto contact me a few years back about doing some work on her property. Her house was at the bottom of a bluff, and she was wondering about swales above her home to keep the water out of her basement in the spring. In this situation, there was the increased risk of sliding, as well as a good guarantee that spring flooding would be made much worse. Sometimes the best advice is not to do anything. I was happy not to ruin her home with swales and I suggested some drainage to carry water away from the uphill side of the home.

The following is a write-up of my February 1 presentation at the Guelph Organic Conference. Many thanks to the event organizers and staff, my fellow panellists, and most importantly to the wonderful, engaging audience.

Permaculture Earthworks

We are fortunate to live in a climate that is relatively abundant in water. The disastrous drought of 2012, however, shows us that we can no longer afford to take water for granted. Globally, nearly half of all land is arid, with a further 25% threatened with desertification. That’s the bad news.

I’m here to tell you the good news. I’m here to tell you about how, with a fraction of the time and energy we have spent degrading our environment, we can foster life and increase biodiversity. And we can do it profitably.

Let me jump right into the “how.” The “how” is based on a few design strategies. One of those strategies is to hold onto the resources we have on site as long as possible. In the case of water, we hold onto it in two ways. One is to put it through as many duties as possible before it is lost to us. The approach we are focusing on today, however, is to capture the water arriving on site, and take it over the longest, and slowest path practical.

Putting this approach into practice means starting at the highest elevation on a site and working downhill with the techniques I am about to highlight.

To hold water at the top of a site, we typically forest hilltops and ridges, along with steep slopes. Forests are very effective at capturing water with minimal runoff. They also have the added benefits of preventing erosion, and adding fertility to the top of a site where it can naturally flow downward. This is a strategy hit on by the Japanese in a traditional mountain region farming system they call Satoyama. Admittedly, this is not a form of earthworks, but it is so integral to water harvesting design that I would be remiss not to mention it.

Water harvesting earthworks have the goal of intercepting runoff water, and storing it. The simplest of the interception techniques involves patterned ripping of the soil with a subsoil plow, given the right soil conditions. With the plow, we cut narrow furrows into the ground just slightly off contour to capture runoff and gently direct it from wetter areas to drier ones. Originating in Australia, this technique has proven very effective there.

This type of interception technique is also really a storage technique as well. The ground is a fantastic place to store water. There it is largely free from evaporation while being available to plant and soil life.

Another common interception technique is the swale, which is a water harvesting ditch dug level on contour. It stops water flowing downhill, allowing it to sink into the ground.

This is a good point to address an argument that too often comes up around water harvesting. Sometimes you will hear a claim from downhill people that you are “stealing their water.” Nothing could be further from the truth. They might see a temporary reduction in runoff onto their land as you hold onto more of your water, but, as you recharge the water table, the medium and long term effect will be to increase the local ground water. In many cases, ephemeral streams will start to have a more regular or even constant flow.

Both of these interception and infiltration techniques are inexpensive and cost effective to install.

Swales are also used in conjunction with earthen dams and ponds. The dams we are talking about are small reservoirs sealed with clay, not concrete structures. Both ponds and dams provide water for irrigation. They can also be put to productive use through aquaculture. While our climate does not support a very large variety of productive aquatic crops, warmer climates can produce prodigious quantities of edible and palatable plants. And even in our climate, water has a better feed conversion rate than terrestrial livestock. For instance, it generally takes 870 grams of feed to produce 100 grams of beef, or 190 g of feed to produce 100 g of chicken. The feed conversion rate for fish, however, is typically 120 g of feed to 100 g of fish.

Aquatic systems are also excellent producers of soil. Their periodic need for dredging yields a very valuable product that adds to site fertility.

In semi-arid and arid conditions, we sometimes employ a land imprinter – essentially a large, patterned drum which can break through desert hard pan and leave divots in the earth. Here debris, including seeds, will collect and moisture will concentrate during rains. This simple approach has proven effective in re-establishing grasslands.

Dug pits can work similarly to establish drought-hardy trees in semi arid conditions.

This has been a very rapid summary to give you a taste of some of the techniques we use. I’d like to leave you with a brief case study of the most dramatic work I have been involved in.

In 2009, I received an invitation to carry out a joint project with a local NGOin Andhra Pradesh, India. This region had traditionally had a dry tropical climate. In recent decades, however, it has grown increasingly arid at an accelerating pace.

When I finally arrived, I found the situation on the ground to be quite bleak. The vegetation is starting to give way to cacti and other desert xerophytes. The local village I worked in now has to draw water from a well over 1000 feet deep, the water from which is tainted with excessive amounts of naturally occurring fluoride.

Before leaving, I’d had it in mind to employ a number of techniques, including ripping the ground with a subsoiler, and building a dam. The soil conditions only lent themselves to swales, however.

I was given carte blanche over 7acres of arid hillside that a local mango farmer considered a write-off for everything except a seasonal crop of pigeon peas.

After crunching some formulas, we laid out contour lines on three levels, then excavated over 400 metres of swales, capable of holding over 1 million litres of water.  Our host farmer was initially dismayed to see us chewing his land up, but started to get the gist of what we were doing. The night before we were to complete the project, a pre-monsoon storm hit, so when the rains hit, he took off on his motorbike, and headed to the site. He was delighted to see that all the water that would have washed down the hillside, and eventually out to sea, was now stored in the ground.

Before I left, I made what I thought was a bold prediction. I said that within 3 years time, there would be springs appearing at the bottom of the hill during the monsoon season. It turns out that my predictions were very conservative.

Six months after I left, I received a photo update of the site. In it, I saw that they had established mango seedlings, and they had managed to do it without drip irrigation – something very unusual even on flat sites in the area.

Tamarind trees on the opposite side of the valley had a very anemic crop, whereas a tamarind tree adjacent to the swales produced an unusually bountiful crop.

I’d made my bold predictions of springs appearing within 3 years. At the bottom of the site there had been a well with water 3 metres down while I was there. Now six months later, the well was full. Water is no longer an issue on the site. And what had been a meager pigeon pea field is now a lucrative mango polyculture.

The results were beyond my most optimistic expectations, and the cost of the immediate project was just $650 Canadian. This is really a prime example of how the cost, effort and time it takes to repair a site is far less than that required to destroy it in the first place. As soon as we pattern our actions in harmony with nature, the payoff is immediate.

These techniques have proven effective everywhere from arid desert to tropical rainforest. They help to rejuvenate drylands, and buffer against drought. We can expect increasingly erratic weather in our future, including severe drought. These water harvesting approaches can help us through the rough times to come, and they can replenish our water tables during the good years.

Rainfall in arid regions occurs in large and infrequent events throughout the year. Because the desert environment is a brittle one and because there is so much rain at one time, tremendous erosion occurs. This leads to the creation of scarps and wadis.

Wadi is simply the Arabic word for a riverbed. In an arid region, its water flow is likely to be ephemeral, particularly in headwaters (where permaculturists are most likely to be working). They are also places where a lot of erosion takes place. Looked at from another perspective, wadis are places where a lot of erosion can be stopped.

After teaching a permaculture course in Jordan, designer Geoff Lawton returned to the area a year later and found that someone had built a gabion (an uncemented rock wall, usually held inside a steel cage) across a particular wadi. Although the 8-foot-high gabion was less than a year old, it was already full of settlement and still had water trickling out of the base, despite the fact that there had not been any recent rains.

This natural tendency for gabions in wadis to quickly fill with water-retaining sediment provides us the opportunity to create what I am dubbing the Instant Wadi-Well (for lack of a better name). After determining where the gabion is to be placed, start with a shallow hole about 2 feet (60 cm) deep in a teardrop shape with the tapered end downstream. Place the first row of stones for the well inside the hole and cement them together, leaving the ground unmortared to allow water to seep in. Keep adding and cementing stones until you reach ground level. Once at ground level, continue up but add an extra 2 layers of mortared stone at the tapering end to allow stability in the face of the rushing torrent and sediment that is to come with the first rainfall. Continue this right up the entire height of the well shaft, making the top row at least 3 feet (90 cm) above the height the gabion will be. After all the sediment moves in, it is likely the well casing will only be 2 feet (60 cm) above the sediment.

All that is left is to build the gabion. Wire cages are not absolutely necessary for the gabion to perform, but they are recommended as they make it far less likely that the rock wall will blow out in the face of the torrent of water, sand and silt.

If the well casing is built strong enough, then there will likely be a well within a few major rain event is. The water will have to be tested as deserts tend to have salty soil. Baring salinity problems, this would be a quick and easy way to establish clean wells and combat erosion at the same time!

This technique compliments other systems as well. For example, if there are storage tanks or cisterns at the top of the scarp, a windmill can be employed to pump water from the Instant Wadi Well to this higher storage. From there, it can be gravity fed down to where it is needed.