Permaculture designs often attempt to manage some of the driest places on earth at one extreme, like as demonstrated in the Greening the Desert Project, to the wettest farms deep in the remaining tropical forests in the world. In the later, an excess of water needs to managed with water diversion systems, whereas in the dryer places a precious amount of water must be captured, distributed and protected.
Permaculture uses a holistic design approach that emphasizes the creation of sustainable and self-sufficient ecosystems employing water management techniques that seek to mimic natural ecosystems. Using the force of gravity is the top-shelf option as far as energizing the irrigation system design, but active pumps such as solar PV or windmill powered pumps can be used where necessary.
5 Water Management Actions
There are different scales for irrigation systems, from the small homestead to large food forests or multi-acre, large production alley-cropping operations. The techniques used to manage water differ based on scale, but all sizes require the same 5 basic actions, capturing source water, storing it, distributing, filtering and protecting this most precious of all resources.
At the smallest scale, the urban balcony garden, rainwater can be collected a few gallons at a time in a bucket for container plants outside or inside the home. The suburban backyard can capture water from the roof in 55 gallon rain barrels raised up 18 inches to accommodate a watering can. Larger water storage tanks can be used in drier climates to collect rainwater from the roof, or diverted through pipes from a stream.
Swales, Springs & Ponds
On more gently sloped lands swales can be used to slow down water’s natural journey down the hill, allowing it to be captured by the spongy nature of the soil. Springs can be captured in spring boxes, accessing the moisture in the mountain. Swales can be hand build on the small scale, and excavated on large farms to slow and store water in the berms. Trees and shrubs can be planted into the moist mounds to give the soil some structure. Ponds of all sizes can be designed and excavated to capture water from the rain, from streams or it can be pumped in from another source, often a connected pond higher in elevation. The slope of the land determines the placement of the pond and that design decision is a trade-off between two forces, free gravitational energy high up the hill, and more volume and ease of storage in lower-sloping, clay-heavy soils. High clay content in soil allows the proper capture of pond water. The techniques used to source fresh water for irrigation is ultimately determined by each piece of land and its unique circumstances.
Storing at Scale
At any scale you want to store water as closely as possible to where you want to apply it. A balcony or kitchen garden can usually suffice with a 5 gallon container to fill a watering can. Clay pots can be filled with water upslope of a fruit tree to slowly seep water into the ground over time. Larger gardens might want to have several watering stations where a can be filled and distributed locally. IBC totes, or 55 gallon barrels can store rainwater from the roof for distribution through irrigation lines. In dry climates multi-thousand gallon water storage tanks or underground cisterns are used to store as much water as possible from the abundance of water falling during the rainy season.
The most natural way to store water is in the soil and the greatest example of that is in the pond. There are many purposes for ponds from creating a natural ecosystem to large capacity fire-fighting ponds. Seepage ponds are partially sealed and store water both above ground and below in the soil of the hill they are designed to seep into. Irrigation ponds are completely sealed so that no seepage occurs and the water is usually accessed through a pipe built through the hill to control the flow of water downhill.
Conventional vs. Drip
Natural rainwater is moved around the land through the Evaporation Cycle, lifted from oceans and lakes into the atmosphere powered directly by the sun and brought back down to the soil by the Earth’s gravitational field. Permaculture strives to mimic this sustainable broadcast-irrigation cycle, but in a more targeted way distributing water stingley only to where it’s needed. Conventional irrigation systems use the convenience of broadcasting water from the top like rain and lose about half of the resource to evaporation. More conservatively, a well-designed permaculture irrigation system will bring water as close to the roots of the plants as possible. Drip irrigation is growing in popularity because it is a cost-effective, water-conserving solution for most farms.
Scale & Distribution Methods
Small gardens like Container or Potager Gardens can use watering cans to get the wet to where it wants to be. The suburban backyard can also be irrigated by hand or, in a pinch, by the garden hose. Small-scale drip irrigation systems can be run along vegetable rows, or in garden beds if hand watering is not desirable. First year food forests require an intensive amount of irrigation for the trees as well as for the understory plants and a drip irrigation system is often the best choice especially in hotter climates where water is becoming increasingly precious. Swales and Seepage ponds do the distribution by design. Irrigation Ponds can be tapped to tie into large-scale drip irrigation systems powered either by gravity or an active pumping system
Not all water is pure; even rainwater can be contaminated by industrial air pollution carrying tiny chemicals that are harmful to living things. The soil and the plants and other life that inhabit it can detoxify the ground over time, but some of these industrial waste chemicals such as lead, cadmium, mercury, arsenic, and chromium, pesticides, PAHs, PCBs and dioxins may require active mitigation with soil remediation, activated carbon or toxin removing plants such as sunflower, indian mustard, ferns, alfalfa and even willow trees. This filtration of the water in the soil happens naturally and inspires most permaculture irrigation systems. Ponds planted with aquatic plants help to keep stored water clean for use in irrigation. At the smallest scale, in the window or balcony garden, if tap water must be used than it should be filtered for applying it to any living creature including your plants.
Greywater & Blackwater Systems
Where the concept of filtering water with plants by design shines brightest is in the residential greywater system where water used in the home gets stored, filtered and used to moisten soil and water crops. Greywater is defined as the runoff from sinks and showers where only food and greywater safe detergents are used. Care must be taken with greywater to minimize its contact with animals and humans so is often distributed below soil where possible. Care must also be taken to not contaminate the water in the home with consumer chemicals poured into drains or toilets as they will end up in the soil and possibly in your annual veggies. Blackwater, like from the toilet, can also be used to water crops but only after an extensive filtration process. Often, the homestead septic mound can tap into this common, sunny resource of fertility to grow a seed bank, wildflowers or other shallow-rooted, above ground herbaceous plants.
Protect from Chemicals
Once you’ve captured, stored, distributed and filtered your plant’s water you need to protect it from evaporation, seepage, leakage or contamination. On the small scale this is achieved more easily than in large operations and is mainly centered around protecting the water from contamination by chemicals in the home or those from road traffic. In most applications, however, we have to protect our system’s water from the sun. Underground cisterns and tanks are engineered solutions that do this very well while the forest achieves this naturally with several layers of shade.
Protect from Evaporation
The permaculture food forest copies the forest’s natural shading ability by defining layers vertically, based on their proximity to the sun. The Large Canopy layer with its nut trees is usually the first line of defense from the evaporative thievery of our Sun. Underneath that is the small canopy fruit trees that tolerate some shade and provide a second layer of shade protection to slow water loss in the forest understory. The shrub and herb layers provide localized areas of shade, thriving in the dappled sunlight. Next is the groundcover layer which is closest to the surface of the soil and that acts as a living mulch, blanketing the moist soil below. In the natural forest these layers decay creating a mulch of biomass that eventually degrades into soil. In the nascent food forest an initial investment of mulch is sourced externally to give the bare soil around the trees the moisture-preserving protection it needs. As the forest grows, the natural mulching process will take over.
Verge Permaculture Algae in Water Storage Tanks