When I was a kid, my brother and I used to enjoy the winter weather at my grandparents’ farm in the mountains. In a beautiful interplay of natural forces, throughout the winter and early spring we would play in half a meter of snow, walk on frozen lakes and then run from the floodwaters once the snow had thawed.
We always looked forward to wintertime and knew what to expect. Now that we’ve grown, however, these natural cycles of snow, ice, and floodwater have changed significantly. It’s not like there are not they no longer exist, but everything has become so much less predictable, and so much more extreme.
This weird weather is the new normal for many of us. It is beyond doubt that we all are experiencing more extreme and erratic weather cycles, with huge downpours and flash floods on the one hand and extreme droughts on the other.
Now, maybe meteorologists will one day call this period of weird weather some fancy term such as the ‘mid-millennium little warming period’ and, looking long term, it will just be blamed on a statistical error, but for us living through this period, it is the new normal. If this new normal continues for just 50 years, while it may a tiny speck of time in the Earth’s history from a climate science perspective, for many of us it’s going to be the rest of our lives, and the lives of our children.
It is this new reality to which we have to adapt and create resilient extreme weatherproof systems that are able to handle either too much or not enough water, all in one growing season. In these circumstances, where water from rainfall is generally in short supply while at other times there is run-off from rainfall, the plan for the control of water is paramount and involves a combination of earthworks, soil-building techniques and irrigation pipes.
Let’s dig deeper...
Permaculture Water Management
Nothing defines the nature of a place more than water! Without water we have deserts almost devoid of life, but with an abundance of water we have rainforests that are the hubs of the Earth’s biodiversity.
Water is always the number one priority for any permaculture system, as Mark Shepard would say: No matter where you go and what mineral deficiencies you have, there are plants who can adapt to these conditions, but no plant can live without water! That’s why Permaculture design tries to harvest, retain and rescue as much water as possible before it is lost from the system.
There are two basic strategies of water conservation on a permaculture farm: storing water in the soil and the diversion of surface water to dams/ponds and tanks for later use; storing it on the surface.
First we want to slow, spread, and sink water as it falls from the sky into the soil. Following this, our secondary goals, as Ben Falk writes in Resilient Farm and Homestead, are to: (1) capture as much water as is reasonably possible, (2) store that water for dry periods, and (3) distribute that water when necessary across the site. Whether you’re going to use one or both of these strategies depends on your site conditions: climate, terrain, soil, your context…
However, as I said, the first objective of landscape design is to control and better use the water that falls on the surface of the land. You want to disperse the flow of water so it can slow down and infiltrate into soil, turning this runoff into soak-in. Essentially, you want to make the water stroll, not run, through the landscape and for this we must shape the land in such a way (more on that later) that it facilitates getting water into the ground and storing it there.
Once you’ve made the best use of the fallen rainfall and stored that water in the soil, you’ll get runoff as the field capacity of soil is reached. Truth be told, you might get this runoff straight away if your site’s watershed is in a bad shape; however, whatever the case, you can begin diverting and storing that water on the surface in ponds and tanks. How much water you’ll be able to store on the surface depends on many factors: your climate, terrain, soil, budget…
Here, I’ll outline the entire process of water management for a permaculture farm, and this includes, but is not limited, to:
- Assessing your site’s water needs and resources
- Developing water storages (both in the ground and on the surface)
- Harvesting water
- Reticulating water
Assessing Your Site's Water Needs and Resources
The first issues to address are what water resources are available to your property, and what exactly are your needs?
1) Your goals and context - what are your water needs, and how do you plan to use your harvested water?
Can we do anything without being clear on what our goals and context are? NO… of course not!
You’ll have to be clear on what you want to achieve with your water system from the outset, because you want to know what size of storage you’ll have to build and, most importantly, whether they’ll be possible to build due to your terrain and your budget.
First, think about how you are planning to use the water: do you need water for household use, livestock, irrigation, fish production, fire protection, recreation…?
Following this, try to get a ballpark estimate of how much water you’ll need for each of these activities - calculate how much you need.
Finally, think about what, realistically, you can build. Here, your budget, available space and aesthetics are all factors you need to consider.
This thinking process can eliminate a great deal of unnecessary planning and will help you prioritize based on the reality of your situation. That’s why we always start with being clear on your context and your goals: The best way to save money on a project is not to start it in the first place!
2) Identify the sources of water
Once you have an idea on your water needs and how you plan to use your harvested water, let’s see what water sources are available to your farm. As I explained in the last post, you can find this out by searching for information online and by reading the landscape.
So, the first question you should be asking yourself is: how much precipitation am I getting within the year - what is my average annual rainfall measured on mm or inches? Secondly, how is that precipitation distributed throughout the year? Is it being delivered in heavy downpours, only during the winter, or equally distributed throughout the year?
Your water systems will be completely different based on these numbers. If you get 600mm as an average rainfall and most of it falls in a few huge summer storms, this will require a completely different approach than 1200mm equally distributed throughout the year.
The precipitation and its distribution will be the foundation for your planning, and you can find this crucial information easily on the Internet just a few clicks away. Now, for other sources of water on your property and beyond, you’ll have to do some permaculture detective work.
You’ll want to distinguish any streams that are running across your property. This flowing water is essentially runoff from outside the boundaries of your property and within your watershed. You can’t control how this water gets onto your site, but you can use it for your water needs if necessary. That’s why you need to know the precise reliability of your water source. Is it perennial or just seasonal? Can you count on it when there is a drought?
Lastly, consider if there is undergoing water that’s available to you. As I outlined in the landscape post, you can’t reliably tell how much water you’ll have under your feet unless you drill a well, but there is a tell-tale sign you can spot in the landscape: If you have any groundwater, it’s another water source which you should take into account.
3) Watershed - determining your place in the hydrologic cycle and your site’s watershed
Okay, so once you’ve got an idea about the precipitation you’re getting and other water sources available to you, you can start by analyzing your watershed and determining your place of the hydrologic cycle.
Every piece of land belongs to a watershed, and it’s defined as an area of land that drains runoff from rain or snow downhill from the highest geographical barriers, such as hills, ridges and mountains, to a specific low point, generally a tributary outlet to a larger river or a lake.
On a larger scale, your land is almost sure to be a part of a regional watershed that drains thousands of square miles or kilometers of land, creating streams and rivers. Although knowing your regional watershed might not have an immediate use to you, I would recommend that you first look at the broader watershed.
Water movement on your site or within your area is a function of where you are in the overall watershed. For example, if you’re high in the hills, you’ll have a small flow of water, probably some small creeks, but on the other hand, if you’re low in the landscape, there be lots of water, probably rivers rather than creeks.
However, to access your site’s actual water resources, you’ll have to look at your site’s watershed or the sub-watershed. You might belong to an extensive watershed, but the precise quantities will depend on the local site’s terrain.
Nothing can be more critical to this process of identifying your site’s watershed than understanding the land patterns represented by topographical maps. For this, you’ll have to be able to recognize the contours for their definition of ridges, saddles and valleys/gullies. This is essential for the effective calculation of catchments.
To start assessing your site’s watershed, you’ll have to define boundaries of your property and the watershed directly affecting your site. You can do this by looking at a topographic map and identifying the divide lines (or center lines) on the ridges. The lines located at the tip of the ridges determine if water is flowing toward or away from your location. Find those lines…
Once you know where they are you’ll have an idea of the boundaries of that catchment and, by using simple math or online tools, you’ll get an estimate of the size of this surface area.
4) Calculate your site’s rainfall volume - your water budget
After you have an idea of the size of your watershed and the average rainfall you’ll receive, it’s easy to calculate your water budget. The first step in doing so is to multiply these two numbers. Calculating rainfall volumes or total rainwater you can get = watershed area x average yearly rainfall.
This number gives you the total rainwater volume assuming there is a 100% runoff, and since we’re not calculating runoff from a concrete patio or a metal roof, we need to adjust that number. You can get a ballpark estimate of runoff volume from any sloped surface by multiplying the volume of rain that falls on that surface by its runoff coefficient.
The runoff coefficient is the average percentage of rainwater that runs off a certain type of surface, and it all depends on what the surface is composed of and the rain intensity - the higher the intensity, the higher the runoff coefficient. I won’t go into details here about calculating rainfall volumes using different coefficients. Instead, if you’re going to run some equations yourself, you can use the following tables from this Darren Doherty’s article…
Now that you’ve calculated you site’s rainfall volume, and taken into consideration any surface streams and underground water, it’s time to circle back to your goals and needs to see is this water budget is sufficient to sustain your needs, along with needs of your crops and livestock. Here’s where reality kicks in and you’ll see what’s possible and what isn’t…
Storing Water in the Soil
Okay, so let’s now start with storing the water in the soil. The cheapest place to store water is in the soil - it’s the largest storage resource available on most sites. Maybe you have big plans for interconnected network of cascading ponds but let’s first cover the essentials that won’t cost that much money. Our initial efforts should always be to get water into the ground and store it there.
To store water in the soil you have to focus on two objectives. The first is to slow, spread and sink the rainfall so that the water takes the longest possible path across your land, rubbing to as many things as possible, spreading where it’s needed, giving it time to infiltrate before it eventually leaves your site and drains away.
Your second objective is to build the soil’s organic matter, because the key to the soil’s capacity to hold water is the organic matter. The organic matter acts as a sponge and absorbs the water that’s slowly moving across the landscape. So it’s imperative that, if you want to store more water in the soil, you must promote organic-matter-rich topsoil.
Research shows that soil with as little as 2% organic matter can reduce the irrigation needed by 75% when compared to poor soils having less than 1% organic matter. Therefore, you’ll want to focus on developing the soil sponge.
You’ll also need to shape the land in such a way as to slow-spread and sink water for that sponge to absorb. To do this you can use two very famous techniques: 1. keyline plowing/subsoiling and, 2. Swales on the contour. Let’s start with keyline…
Keyline plowing /subsoiling - Keyline Pattern Cultivation
The concept of keyline agriculture emerged from the drylands of Australia thanks to P.A. Yeoman. This now legendary Australian bloke has shaped how we permaculturists think about managing water on the farm.
While keyline agriculture contains many concepts, its most fundamental is to spread the abundance of water from where it is concentrated in wet areas to areas that are consistently too dry. You see, normally water flows from ridges into valleys. The ridges stay dry, and the valleys accumulate moisture.
However, by using a keyline cultivation pattern, you can channel the water away from the valleys and towards the ridges, and, by so doing, distribute it evenly over the land and increase the infiltration. This is achieved by using the tractor and ripping lines (opening up furrows in the soil) with a keyline plow parallel to keyline (thus giving the name keyline cultivation pattern).
These small water channels in the soil, these hundreds of small drains, will then intercept water that flows down toward the valleys and move it in the other direction, toward the ridges. The net effect is that rip lines hold water for infiltration, instead of the water running down the slope. With more water in the soil, plant growth and soil microbes increase.
Keyline cultivation is also a soil improvement system, as it promotes rapid topsoil formation. As you create furrows in the soil and rip the subsoil you allow water and air to infiltrate deeper into the soil where they can be used by plants. This can break up the hard pan and build rich fertile soils, and, as you already know, as soil becomes fertile, more water can be absorbed and stored.
So, now you can see why keyline pattern cultivation is such a great tool in managing water on a permaculture farm. It can harvest rainwater, distribute it equally and build rich, fertile soils by turning subsoil into topsoil. I don’t want to make this post longer than it has to be, so I won’t go into how to find a keyline at this point, instead you can read P.A. Yeoman’s book Water For Every Farm.
Swales on contour
Your second strategy for storing water in the soil is by using swales. Swales also help us to slow, spread, and sink water, allowing us to hold off the runoff water and allowing it to seep into the soil, thus storing it there.
In his book Gaia's Garden, Toby Hemenway describes a swale as: a shallow trench laid out dead level along the land’s contours. It can be anything from one to several feet across, a foot or so deep, and whatever length necessary. The earth dug from the swale is piled on the downhill side to make a raised mound or berm.
During the rain event, once the soil can’t absorb the falling rain any longer, overland flow occurs. Whatever water the soil can’t absorb flows downhill as runoff. As that surface water and rainwater runs downhill it is intercepted by the swale, spreads out along its length, and slowly percolates into the soil.
This underground water then seeps downslope, forming a lens of moisture. The stored water creates an underground reservoir that aids plant growth for tens of feet below the swale. Most importantly, swales are tree-growing systems; by planting trees or other crops on the mound (berm) on the downhill side of the swale (or just below it) they’ll be able to take advantage of this soil moisture during dry periods.
We primarily use swales for this purpose, but swales also prevent gullies from forming by intercepting rainwater, slowing it, spreading it, essentially decreasing its erosive potential. Swales also trap organic matter and the ditch becomes a rich, thick layer of humus which holds a considerable volume of water. Moreover, once you have it dug out, you can bring that organic matter in, fill it out with wood chips, dead branches….
Now I know that, after hearing about swales, you’ll be eager to implement them on your land, but would they work on your property? Swales are the most widely used and abused permaculture water-management technique. There are many factors that influence whether or not you swale your property, depending on your slope, soils, hydrology, type of management, ecosystem’s condition and resource base.
Generally, swales are most appropriate for slopes of 5% or less. The size of watershed, the climate, the soil type, and the land use determine how much water flows off the land and into swales. Small watersheds, sandy soil, and forested areas won’t produce much runoff. Conversely, large watersheds, and soils with clay and loam, shed more water. The location’s climate also plays a part, because some areas are more likely to experience intense storms with more runoff.
Here is a nice infographic from Ben Falk I found online, which explains whether or not you should swale.
Storing Water on the Surface
Okay, once you’re done with storing water in the soil, and developing that cheap water storage in the soil, let’s move to storing water on the surface. Here we’ll be developing water systems that will store, harvest and reticulate surface water.
Water Storage (options)
On the surface, you can store water in the ponds/dams and in the water tanks…
If you need to store anything less than around 100 000 liters of water or just need drinking water, then a water-storage tank is potentially a cheaper and better option. Moreover, your site terrain might indicate that a pond construction would be too expensive so, yet again, a tank is a better option.
You can construct water tanks from various materials and, if you position them somewhere on the top of your property, at highest practical point, you’ll have a source of effective gravity storage in conjunction with, for example, a lower level pond, stream or groundwater.
The cheapest way of storing large volumes of water (more than 100 000 liters) is in a water-storage dam or pond. In a changing climate, water in a pond is an enormous asset to have, you can use it for many different purposes at once - for aquaculture, irrigation, stock and domestic storage, wildlife habitat, recreation and more…
Generally speaking, there are two type of ponds/dams - an embankment pond and an excavated pond. An embankment, as the name suggests, is made by building an embankment or dam across a stream or watercourse where the stream valley is depressed enough to permit storing reasonable amounts of water.
An excavated pond is made by digging a pit or dugout in a nearly level area. Because the water capacity is obtained almost entirely by digging, excavated ponds are used where only a small supply of water is needed. Some ponds are built in gently to moderately sloping areas and the capacity is obtained both by excavating and by building a dam.
Now, what type of a pond you’ll be able to construct and, most importantly, where, depends on your site’s terrain. Different pond types and locations have different storage ratios (the volume of excavation versus the volume of storage) and this is the most important factor in determining how viable a potential site will be. When constructing a pond, what you want to ensure is to make a minimal investment in both time and earthworks for a maximal amount of storage.
The type and dimensions of the pond will also depend upon the climate and the amount of average evaporation losses. In semi-arid and arid zones the amount of evaporation will be quite significant in comparison with cooler climates. Ponds in the hotter zones need to be deep in order to overcome annual evaporation losses…
With this in mind, let’s go through different pond types from the most economical and easiest to dig to the more expensive ones that require more extensive earthworks. In so doing, the first rule of working with water is to keep it in its place of highest potential on the landscape, up high if it can be economically placed there. So, we’ll start from the locations up the hill and go downhill.
- Gully/Keypoint Ponds
These are probably the most common of all dams and one of the easiest storage options. Since they are constructed by building an embankment in a gully or in a drainage depression, they are also the most economic option. The earthworks required come down to building a dam wall that needs to be capable of keeping the water in a gully/valley behind it.
The right way to pinpoint the best pond location in the gully/valley would again be by using keyline design principles. In this context, this means first identifying the major keypoint of the slope (where the gully/valley slope section changes from a concave to convex profile), once you know where the keypoint is located, the contour line on the landscape that goes through the keypoint is the keyline.
This keyline is the highest contour in the gully/valley that can efficiently hold water, and usually the highest overall practical point in the landscape to hold water. The main use for keypoint dams/ponds is to store irrigation water. This irrigation water is then generally released though the large pipe going underneath the dam’s wall.
- Saddle Pond
A saddle is a topographic feature - this is simply a dip or break along a level ridge crest. Since it’s on a ridge, this is the high ground and the highest available water storage in the landscape. This pond has a much smaller watershed than a gully/valley pond, but still can collect water runoff from both sides of the ridge crests. The primary use of a saddle dam is for wildlife and domestic stock, not so much for irrigation.
- Hillside/Contour Ponds
Contour or hillside ponds are built on the side of hills and usually have a three-sided or curved bank or long, curved bank straight across the across the hillside slope (on the contour). The best way to locate these types of dam is to look at your topographic map and check for any widening of the contours along the hillside. Widening means that the terrain is flattening and this might be a good location for the pond.
These ponds are relatively expensive to build since you have to do more digging for less water storage, but they’ll still provide you with a gravity storage. Gravity-fed water still gets priority over ponds in the flat. They are usually filled by diversion drains or graded catch drains and have the same use as a saddle dam: for wildlife and domestic stock.
• Ponds for the flat sites: Excavated tanks, Ring tanks, ‘Turkey’s nest’ ponds
Ring tank / dam
‘Turkey’s nest’ dam
All these are suitable for flat sites, and since they cannot capture runoff, they need to be filled from external sources. In excavated tanks, the excavation becomes the water storage, below the surface level. Earth removed is stockpiled nearby, unless additional dam walls are constructed for additional storage above ground level.
Ring tanks are constructed by using earth from inside the ring (circular or shaped to suit topography) to build the surrounding embankment. Water is generally stored above the natural surface. ‘Turkey’s nest’ dams are a variation of the ring tank where the borrow pit is located outside the embankment. Water is stored above ground level.
Once your water storage is ready, you need to develop and expand upon the methods of harvesting the water. Sure, you can fill your ponds with water from a well, but before you go deep and tap into the underground aquifer, you’ll want to use the surface flows and rainfall runoff to fill your water storage.
You can capture water with water-harvesting drains that will divert the runoff, stream flow or pumped water into your ponds, and subsequently tanks. Bill Mollison in his Designers Manual explains: These drains are actually trenches in the soil that aren’t dead level: they are placed in the landscape off-contour and have a slight gradient, with the goal of moving water to a specific location such as your pond.
You can think of diversion drains/ditches as being giant earthen gutters placed across the landscape to harvest and move water in a manner similar to rain gutters on a house. They differ from swales in that they are built to flow after rain and, unlike swales, which are normally built on permeable soils, diversion drains work better when the base and sides are clay-lined.
However, swales or ditches on contour can also harvest water for you, and if they are connected to your pond as they fill up, they will overflow to your ponds. Also, if you have a series of ponds connected with swales, then the overflow of one pond enters the feeder channel/swale of the next. Having a spillway for a pond is a must and this way you’ll once more be slowing, spreading and sinking water across your landscape.
Once installed, your roads themselves become a very important and efficient water-harvesting system. Since the roads are compacted, graded and often made of impervious materials, they have very high runoff coefficient. In certain landscapes like karts, the roads will be the only available runoff surface. The roads and the adjacent water collection drains can be then also integrated with other harvesting drains and/or swales, contributing to the overall hydration of the farm.
When developing the water resources of a farm, there are two primary water channels in addition to already mentioned harvesting drains. The other type of water channel is there for irrigation purposes. These diversion drains, which are essentially the same thing as harvesting drains (placed in the landscape off-contour, have a slight gradient, moving the water) here function as irrigation channels for flow irrigation.
Water from a pond is directed into the drain, it fills up and overflows the top side, along its length, and cascades downhill over crops or paddocks… Basically, you can use these types of drain for your field irrigation of crops such as potatoes, corn and beans, or water your pastures.
In his book The Bio-Integrated Farm, Shawn Jadrnicek recommends that in order to build this drain, start at the outlet - a pond, retention basin, swale, or some other area with the capacity to hold and safely release the harvested water, and move down the slope towards the desired irrigated area.
Another way of reticulating water is the release of the water stored in ponds and water tanks by a gravity-fed pipe network. In adopting this approach, you will use your header water tank located at the highest point in your landscape and release the stored water to irrigate your orchards and gardens through the network of irrigation pipes. You could do the same on a bigger scale by using a pond as a source of stored water and a series of the irrigation reticulation pipes connected to it.
Managing water is crucial in designing and setting up a permaculture farm. No permaculture site has been properly planned unless it first considers how to use the available water resources.
The water systems you establish become a permanent feature of the new landscape and the base of permaculture land development planning. All the water lines: diversions, swales, terraces, dams/ponds, channels, form the foundation that other infrastructure components (structures, farm roads, fencing) will follow.
- You want to boost the overall resilience of the farm by first storing water in the soil, this is done by building soil’s organic matter, using swales and keyline cultivation pattern.
- Once you have evenly hydrated the whole landscape you can capture the runoff rainfall with harvesting drains and fill up your water tanks and ponds. Keep this water for times of drought and release it through irrigation channels and pipes to rehydrate the landscape while you’re waiting for the water droplets to return.
I hope this post has helped you to better understand water management on a permaculture farm. If you found it useful, please share it with anyone interested in permaculture water management.