Water Management For Every Permaculture Farm
By William Horvath
When I was a kid, my brother and I used to enjoy the winter weather at my grandparent’s 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 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. 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. This is the new normal.
We have to adapt to this new reality by creating resilient extreme weatherproof systems that are able to handle either too much or not enough water, all in one growing season. In these circumstances, the plan for the control of water is critical and involves a combination of earthworks, soil-building techniques and irrigation pipes.
Nothing defines the nature of a place more than water and water is always the number one priority for any permaculture system, as Mark Shepard, author of Restoration Agriculture, says: “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 cycles from capture.
There are two basic strategies of water conservation on a 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. You want to disperse the flow of water so it can slow down and infiltrate into the soil, enabling this runoff to soak in. Essentially, you want to make the water stroll, not run, through the landscape. Our next 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, and your land’s context.
Here, I’ll outline the entire process of water management for a farm:
Assessing Your Site's Water Needs and Resources
1) Your goals and context - what are your water needs, and how do you plan to use your harvested water? 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 storage you’ll have to build and, most importantly, whether it’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, or recreation? Calculate how much water you’ll need for each of these activities. Finally, think about what, realistically, you can build considering your budget, available space and aesthetics.
This thought 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 of your water needs and how you plan to use your harvested water, see what water sources are available to your farm. What is my average annual rainfall? 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 the answers to these questions. 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 detective work.
Locate 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 (be sure to check your stream’s class classifications first though, and DEC restrictions on pumping from streams if you plan to use substantial water). 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? Is the water clean enough for your purposes or contaminated in some way?
Consider if there is water underground that’s available to you. While you can’t reliably tell how much water is under your feet unless you drill a lot of wells, you can determine your site’s watershed.
3) Watershed - determining your place in the hydrologic cycle and your site’s watershed. 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 looking at the broader watershed to understand the ultimate source and destination of your water as well as how it moves.
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 may 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 the 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. 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. You’ll then need to calculate your site’s rainfall volume - your water budget. You can read basic instructions on my website or check out Darren Doherty’s article and tables at regrarians.org.
Storing 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 an 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, running over as many things as possible, spreading where it’s needed, and 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. Organic matter acts as a sponge and absorbs the water that’s slowly moving across the landscape. 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.
Keyline plowing /subsoiling - Keyline Pattern Cultivation
The concept of keyline agriculture emerged from the drylands of Australia thanks to P.A. Yeoman. Yeoman shaped how we permaculturists think about managing water on the farm. While keyline agriculture contains many concepts, the most fundamental is to spread the abundance of water from where it is concentrated in wet areas to areas that are consistently too dry. 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 in the process 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 the keyline.
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. Read more in 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 to several feet deep, and whatever length is necessary. The earth dug from the swale is piled on the downhill side to make a raised mound or berm.
During a 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, spreading it out along its length, and slowly it 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 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, and essentially decreasing its erosive potential. Swales also trap organic matter and the ditch becomes a rich, thick layer of humus that holds a considerable volume of water.
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 site 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 the 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, which explains whether or not you should swale.
Storing Water on the Surface
Once you’re done storing water in the soil, let’s move to storing water on the surface. The cheapest way of storing large volumes of water (more than 100,000 liters) is in a water-storage dam or pond. (Your local Soil & Water District and NRCS offices can be a great resource for pond design, safety considerations, construction and - in some cases - approval.) In a changing climate, a pond is an enormous asset to have. You can use it for many different purposes at once - aquaculture, irrigation, stock and domestic storage, wildlife habitat, recreation and more.
Generally speaking, there are two types 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, you want 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. With this in mind, here are different pond types from the most economical and easiest to the more expensive ones that require more extensive earthworks. 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, one of the easiest storage options and most economical options. They are constructed by building an embankment in a gully or drainage depression capable of keeping the water in a gully/valley behind it. The main use for keypoint dams/ponds is to store irrigation water. This irrigation water is then generally released though a large pipe going underneath the dam’s wall.
- Saddle Pond: A saddle is a topographic feature - 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 as 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 hillside slope (on the contour). The best way to locate these types of dams 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 gravity storage. They are usually filled by diversion drains or graded catch drains and have the same use as a saddle dam - wildlife and domestic stock.
Ponds for flat sites: Excavated tanks, Ring tanks, and ‘Turkey’s nest’ ponds are suitable for flat sites, and since they cannot capture runoff, they need to be filled by 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.
You can fill your ponds with water from a well, but ideally, you use surface flows and rainfall runoff. You can capture water with water-harvesting drains that will divert the runoff, stream flow or pump water into your ponds, and subsequently tanks. 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, will overflow into 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.
Any roads on your landscape are a very important and efficient water-harvesting system since they are compacted, graded and often made of impervious materials. The roads and adjacent water collection drains can be integrated with other harvesting drains and/or swales, contributing to the overall hydration of the farm.
Managing water is crucial in designing and setting up a farm. No 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, and channels should form the foundation that other infrastructure components (structures, farm roads, fencing) follow.
William Horvath, the founder of the Permaculture Apprentice website
The full version of this article can be found on the Permaculture Apprentice website, permacultureapprentice.com/permaculture-water-management. The article was reprinted with permission from the author.