Following on from previous articles in this exclusive Equine Permaculture Design Series, Mariette van den Berg explains how the permaculture design principles can be applied in practice on horse properties.
The permaculture design approach aims to build systems that are easier to manage, more efficient and sustainable, whilst considering the health and wellbeing of all – people, horses, plants and the soil that sustains them. And this article focuses on how we can harvest and store that most precious of natures resources: water.
“Water is the driving force of all nature” – (Leonardo da Vinci). Without water we won’t be able to sustain our cells or grow plants that can feed our animals and ourselves.
While water is our number one essential, very little of our water reserves are actually available for present human needs due to run-off. Many areas on earth, particularly dryland areas, or over-developed cities and towns, and surrounding agriculture face a shortage of useable water.
In addition, environmental peaks (and/or climate changes) can even put an extra strain on available water reserves. This is why the value of land should actually be assessed on its yield of drinkable water, which should be viewed as an economically-valuable product. Water as a commodity is already transported by sea on a global scale.
Few farmers and property owners consciously invest in ‘drought-proofing’ their place before any foreseen peaks. It’s more common that people take action when drought or floods hit them. But, like a bush fire, it is always better to have considered this danger during the design process of the property and when developing an evacuation plan.
Water flow and storage should be viewed in the same way in your planning.
In Permaculture, the wild energies, the ‘elements’, such as water flow, rain, fire, sun and wind that come into the property are essential to the design, and are usually planned in sectors (see our previous article on zone and sector analysis). By identifying these sectors on our property, we get a clearer picture of where water flows and where potentially we can harvest and store water.
Once we have identified and established these areas, we will need to consider the methods to harvest, infiltrate or store water – which is the focus of this article.
Water conservation and storage
There are two basic strategies of water conservation in run-off areas: the diversion of surface water to impoundments (dams and tanks) for later use, and the storage of water in the soil. Both result in a recharge of groundwater.
Some of the main productive earthwork features we create for water conservation are:
• Dams and tanks (storage),
• Swales (absorption beds),
• Diversion systems or channels, and
• Irrigation layouts for soil conditioning.
Storing water in farm dams
Small dams and earth tanks are commonly found or installed on properties in Australia, and they have two primary uses. Their minor use is to supply watering points in pastures for your horses, stock and wildlife. These tanks or water points can be modest systems, widely dispersed and static.
For water cleanliness and parasite control, horses, cattle and other animals should be watered by troughs, not directly from the dams. This will also reduce damage to the dams and avoid potential accidents where animals get trapped in the muddy banks, which is quite a common occurrence in Australia.
The second and major use of small dams and earth tanks is to contain or store surplus run-off water for daily use over dry periods, for domestic use or irrigation.
Dam design and planning
This, therefore, needs to be carefully designed with respect to factors such as safety, catchment or water harvesting, total landscape layout, outlet/overflow systems, draw-down and placement relative to the usage area (for example, to allow for gravity flow).
Climate should also be factored in the equation when designing open water storage systems. Free water surface areas are most appropriate in humid climates where the potential of evaporation is exceeded by the annual rainfall.
In arid to sub-humid systems, however, open dams can become a danger because evaporation can concentrate dissolved salts. Firstly, such salt water can affect animal health and, secondly, the inevitable seepage from dams can and does create areas of salted or collapsed soils downhill from such storages. Therefore, in these climates, it’s important to also incorporate other design strategies that reduce evaporation or transpiration (winds). For example, by planting suitable vegetation in or around the dam.
It’s important that dams and ponds are designed in such a way that they do not stop flow in streams, displace populations, fill with silt, block fish migration or create health problems.
It may seem counter-intuitive, but properly constructed dams and storage effectively add to the stream flow in the long term. Even dams with considerable retaining walls, which have over-sized stable spillways, are no threat to life or property if they are well-made. Low barrier dams of 1-4 m (3-13 feet) high can assist stream oxygenation, provide permanent pools, and can be stepped to allow fish ladders or bypasses.
Most landscapes can hold and store water, but the storage efficiency may depend on the type of soil. Soils may be free-draining or have deep and coarse sands, other areas may be too rocky or have fissured limestone, and yet others are too steep or unstable. However, great many productive areas of clay fraction subsoil (40% or more clay fraction) will hold water behind earth dams, below grade levels as earth tanks or perched above grade as ‘turkey nests’ or ring dams.
Almost every type of dam is cost-effective if it is located to pen water in an area of 5% or less slope. Nevertheless, many essential dams, if well made and durable, can be built at higher slopes or grades using different materials. Each and every dam needs a careful soil and level survey, and planning for local construction methods.
We can increase the storage capacity of almost any landscape. There are few landscapes that will not store more soil water when humus, soil treatment and/or swales are used. Soil itself is our largest water storage system in the landscape if we allow it to absorb.
Storing water in the soil
Soil (carbon) is important because it acts like a sponge – holding water and nutrients, and supporting life for organisms above and below the surface. Unfortunately, much of human settlement is built on compacted run-off land – whether it be roads, overgrazed farmland, the suburbs or cities.
Water has to go somewhere. If it is not seeping into soil carbon for storage and hydration, then it is going out to rivers and the sea.
To prevent the topsoil of a compacted landscape washing away, Keyline design and ripping slows the water run-off and allows the landscape to absorb changes in the weather patterns as they arise.
The Keyline design and plough concept was originally developed by P.A. Yeomans in the 1950’s to address issues of dwindling water supplies and soil erosion on Australian rangeland.
Yeoman developed a system of ‘amplified contour ripping’ that maximises productive use of rainfall and facilitates the uniform irrigation of land. Keyline ripping positively contributes to erosion control by building soil and soil carbon.
Through the process of deep-ripping land, and moving water from gullies to ridges to hydrate the landscape, Keyline systems help to drought-proof farms by encouraging deep penetration of plant and grass roots.
The main idea behind Keyline design is to capture water at the highest possible elevation and comb it outward toward the ridges using gravitational forces, reversing the natural concentration of water in valleys.
Maximising the flow of water to the drier ridges and using precise plough lines that fall slightly off contour slows the movement of water and spreads it more uniformly, infiltrating it across the broadest possible area.
By effectively capturing and distributing rainwater, and enhancing soils, Keyline design allows us to delay irrigation from off-farm sources until later in the season, and can result in fewer applications being required in the dry season.
This system captures significant quantities of water that would otherwise run off, and stores it in the soil. It also builds soil fertility, which further improves moisture-holding capacity. The addition of organic matter increases the number of micropores and macropores in the soil — either by ‘gluing’ soil particles together or by creating favourable living conditions for soil organisms. Certain types of soil organic matter can hold up to 20 times their weight in water.
Soil conditioning or ‘ripping’, providing it is followed by tree planting, trace element editions (fertiliser/compost), and proper grazing management certainly will increase the ability of soils to hold and infiltrate water.
Areas of up to 85% run-off can be converted to zero overland flow by a combination of soil conditioning, swales and water spreading towards vegetated areas (trees).
Another important tool in pasture and land hydration is the use of swales and dams. Swales are not the same as contour banks. Contour banks actually redirect the water slightly off-contour, and drain to a central point to slow water and to stop erosion.
Swales are level banks that follow contour from start to finish. Swales, as used in permaculture are designed to slow and capture run-off by spreading it horizontally across the landscape (following exactly an elevation contour line), and used to facilitate infiltration of water run-off into the soil.
A swale is created by digging a ditch on contour and piling the dirt on the downhill side of the ditch to create a berm. The soil that is excavated from the ground is placed, uncompacted, on the lower side of the excavation in a rounded, mound shape.
Run-off water will flow into the swale when the topsoil on the pasture is at 100% water-holding capacity. The swale water is absorbed, and taken deep underground to recharge the subsoil and replenish underground springs.
This infiltration process, therefore, achieves two aims: it slows water in the landscape and retains it in the ground for longer periods of time, recharging and rehydrating the landscape.
Dams and swales can be integrated into a single design by connecting the dam’s spillway with a swale. They extend the dam’s water storage capacity, and they can back-flow and recharge each other.
Once the safe maximum level (free-board) of the swale and dam is reached, a passive discharge across a level sill spillway of around 4–5 metres (13–16 feet) in length for large systems spills the water in a level sheet of water (usually 3 to 5 mm deep, depending on rainfall). The spilled water then runs across the grass and is discharged on a ridge rather than a gully. It is important to place a nitrogen-fixing legume crop, such as cowpea or field pea, in the new swales and trees to stabilise the soil.
Banks and drains
Diversion drains are gently sloping drains used to lead water away from valleys and streams into storages and irrigation systems or into sand beds or swales for absorption. Diversion drains are different from swales in that they are built to flow after rain (from overland flow or from feeder streams). They are commonly used in Keyline systems, connecting a series of dams so that overflow of one dam enters the feeder channel of the next. Drains need careful planning and survey to manage flow rate and overflow.
In Australia, we are already accustomed to a great variety of surface (tank) storages. In some jurisdictions, governments require the construction of new homes to include rainwater tanks to supply water for toilet flushing, laundry and outside uses. Many local councils even provide rebates to home owners who install rainwater systems into new and existing dwellings! In stark contrast, however, domestic rainwater tanks are insignificant in Europe, the USA and other developing counties where drinking water may be rare. Up until 2009, it was illegal to harvest rainwater in Colorado, USA! In addition, in the UK, USA and Brazil, for example, farmers rarely use multiple earth storage systems for water; instead, expensive pipelines and bores are the preferred ‘alternative’ even where local rainfall often exceeds local needs.
There are many types of tanks that we can use – the most common in Australia are concrete tanks, poly/plastic or metal/steel tanks. The volume of the tank(s) will largely depend on the size of your household and usage per year. But, about 22,500L can provide a family with all needed water (drinking, showering, cooking, modest garden water on trickle) for a year.
Tank water is renewed by rain at any time of the year, Every roof – whether domestic, sheds, stables or industrial – would fill many such tanks, and a simple calculation (roof area x average rainfall in mm or inches) and conversion to litres gives you the expected yield.
Granted that birds, dust or industry can contaminate roof areas, the first precaution is to reject the first flow-off of water and use it on gardens, pastures or swales.
There are a number of methods that you can use such as the downpipe ‘first flush’ diverters. They are installed at each downpipe that supplies water to the tank and they use a dependable ball and seat system – a simple automatic system that does not rely on mechanical parts or manual intervention. As the water level rises in the diverter chamber, the ball floats and once the chamber is full, the ball resets on a seat inside the diverter chamber preventing any further water entering the diverter. The subsequent flow of water is then automatically directed along the pipe system to the tank.
First flush systems prevent sediment, bird droppings, spiders, insects, mosquitos and debris entering the rain water tank, and will improve water quality. The system is ideal to use in conjunction with a rain head.
As for the entry of insects, birds and rodents to tanks, a ‘U’ pipe entry and exit, a sealed tank roof, and an overflow pipe emptying to a gravel filled swale or rock garden all effectively excludes these potential nuisances. If birds persistently perch on the roof ridges, a few fine wires or thread stretched along the ridge as 10cm high ‘fence’ could discourage them.
Gutters on roofing should be cleaned out regularly or leaf-free gutter or downpipes fitted. Given that most dust and leaves are removed, leftover organic matter is usually harmless. Organic matter ‘fixes’ itself as an active biological velvety film on tank walls and bases. Nevertheless, to improve water quality for drinking, many people may install filter systems or include products such as limestone, shell or marble chips in the tank to increase the pH level (alkaline), to prevent heavy metals to be taken up from the water.
On any property, it is important that you identify all the sources of water, analyse for quality and quantity, and reserve sites for tanks, swales and dams.
Whenever possible, use the slope or raise the tanks to get the benefit of gravity flow to your water points. Detail also a list of trees and plants that, once mature, will grow unirrigated in your situation.
In the general landscape soil, samples (for 40% or more clay fraction) will reveal sites suited for earth-dam construction. Even if the budget does not allow immediate construction, those sites need to be reserved for future storages.
A sequence of primary valleys may enable a Keyline system to be established for downhill fire control and irrigation.
Get good advice and supervise the construction of all dams. Whenever possible, do not impede normal stream flow or fish migration, and place houses, stables, arenas, etc. out of the way in case of dam failure.
In particular, you must allow for an adequate and stable spillway flow that can cope with a ‘worst case’ rain intensity.
Finally, make sure that all earth storages, and, in particular swales, are planted with vegetation (first a fast-growing cover crop and later trees) to remove infiltrated water and, in arid areas, to prevent salting problems.
Read this article to make your own rain water garden as an innovative and practical way to make use of water run-off around your facilities, stables and wash bays.