During our April 2011 Permablitz we started to work on a pond for our permaculture garden. Our objectives were to provide a place of beauty and tranquility, an aquatic habitat for a diverse range of flora and fauna, some food production in way of plants and fish and a water catchment and storage facility.   Here you will find a step by step account of our project with plenty of information on ecological pond design,  maintenance,  planting schemes and how to keep your neighbours happy :)
So lets start with why?



Why build a pond ?
    A pond can serve multi- functions, examples of which are:  a water reservoir, swimming pool, aquaculture site , fish production, provider of beauty, duck rearing, wildlife attraction, biodiversity enhancer , home for  beneficial animals such as amphibians, a great provider of biomass for mulch, chicken fodder and even fuel production.  It is certainly good to have a clear idea why you personally want to build a pond as this will be crucial for the successful design.

Here are our main objectives:

• Aquaculture: We want to use the pond to rear some edible plants and fish which we intend to feed ourselves, the dog and the cat with.  We also want to grow a large percentage of mulch needed in the garden from within the garden and aquaculture is a great way of achieving this.  The ability to grow in the medium of water is far more efficient and productive than any land based efforts.  This is primarily because the essential component to growth, water, is always present.  Secondly the lack of  gravity in the water means that water based life has more energy to expend in growth as opposed to structural  support.      
  

• Biodiversity: A pond designed well can support many varieties of plants and aquatic animals.   The water also supports land based mammals, birds  and insects  where they will frequent the pond for a drink or bath.   By supporting a variety of species the ecosystem overall becomes more resilient and less prone to problems.  Hence a garden with high biodiversity needs no chemical sprays or fertilization and performs better than gardens that are reliant upon this . This is something which becomes clearer every year we spend in the garden  so more biodiversity is always welcome.
  

• Beauty ,Education and Recreation: We love water  and so do the kids who love to spend hours watching the pond life intently.  The pond will be a place to hang out and chill out and perhaps to dip into in the hot summer months.
  

 

A cross section of a ecological pond

 
How to build a pond ?

There are 3 main things to consider when choosing a site for a pond

• Topography

    Its better to construct ponds in waterlogged areas. This limited depth of digging reduces the construction cost and efforts considerably. However, full consideration should also be given to the possible effects of flood.  The low lands are also desirable as this is where a pond would naturally occur, and will collect water passively it will also look better here as it will seem more natural. The surrounding vegetation is also something to bear in mind.a  nearby fast growing tree like the willow can puncture clay and concrete membranes.   Furthermore, the annual  leaf and fruit drop from a tree can cause a loss of oxygen as the aerobic bacteria go to work on them in the water. This process is called eutrophication and can lead to very little diversity in the pond as most other lifeforms are starved from lack of a oxygen consumed by the bacteria. You may recognize this condition by the green blanket weed you see covering some ponds.

If you want to build a pond on a slope then you will need a wall on the lower side, this kind of pond building, especially if it is a larger pond, requires some expertise and it is recommended to seek advice.

• Source of water and its quality

    A dependable source of water supply must be available within or near the site. This is to compensate the water loss through seepage and surface evaporation thereafter. Equally important is the need for avoiding excess water and hence there must be arrangement for the excess water to escape through a bypass channel or a spillway. The water supply to the pond should as far as possible be natural, preferably rain water. However, alternative arrangements of water supply should be made for dry season either from a deep tube well or irrigation canal or from perennial sources like spring, stream, river, etc. It helps if the pond is on the lower lands to allow accumulation of surface runoff from a larger catchment area, again care should be taken to avoid flooding. 

• Soil Type
  

  Pond soil must retain water. Soils with a low infiltration rate are most suitable. The best soils are impermeable clay which can be easily compacted and made leak proof. Clay aside loamy soils can also be used, but they need to be compacted well and may leak slightly in the early stages, although they tend to seal themselves with time.  Sandy and gravelly soils should be avoided, but if they are the only ones available they must be made impermeable with a thick coating of clay or with polythene sheeting.  Soil impermeability can also be achieved by soil compaction at the pond bottom and sides with either a mixture of soil + 1–5% cement or soil + 10–20% cow dung. Treated areas should be kept moist for 2–3 days by gently sprinkling water to avoid cracking and finally the pond is filled with water. More on this below.

  Peat soils have special problems, since they are usually very acidic in nature and need sufficient liming, while the organic matter decomposition may lead to dissolved oxygen deficiency. Soils rich in limestone also create special problems, since the excessive lime content tends to precipitate phosphate and iron.   Such ponds would then have little plankton population and macrophytes and would be relatively sterile. This can be overcome by adding sufficient organic matter such as cowdung, poultry manure, etc.

   A general and convenient field test for the soil quality is to take a handful of moist soil from the test holes made at the proposed site and to compress it into a firm ball. If the ball does not crumble after a little handling, it indicates that it contains sufficient clay for the purpose of pond construction. Several test holes should be made across the site and soil samples may be collected vertically from every 0.5 m of depth reaching up to a level of 1 m in a test hole. You can see our test holes on the first two pictures in the above slide show. Although our soil had some clay content it was not enough to retain water.

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   It is worthwhile to design in as much edge and as much variation in depth as possible to achieve maximum diversity of habitat. Edge is an ecological phenomena that observes the fact that the edge of one habitat with another, say pond shore to land surface or forest edge to meadow, supports many more lifeforms than either habitat alone.  At the very least, you should account for the four different types of plants which  can cohabit a water body, provide a gentle slope for amphibian and insects to enter and exit and provide hiding places for fish and other pond life in the form of tree stumps or hollow rocks.

 

The 4 types of plants : note that  each requires a different a habitat  as you can see from the diagram below

 

   Further variation will only increase diversity and these can come in the form of a beach area , an island, marshy area, peninsula forms or chinampas.

Laying out
  You should start by sketching out how your pond should look on paper and work out the dimensions. A useful aid when laying out your pond in the garden is a piece of rope which can be used to mark the shoreline.  It helps to visualize where the water will be and observe how it might interact with the surroundings and overall garden design. 

Gradients
   Its best to site your pond on level ground but if you do not have this privilege than use the earth from excavation to mound up the lower side to prevent any over spill. When doing this you need to compact the soil very well layer by layer and sow a cover crop in soon as possible to prevent erosion.

Lining

• Clay

If you are fortunate enough to have a clay soil than you will still need to puddle the substrate to avoid seepage. This is easy ,get it wet and stamp up and down in it preferably with lots of help. Its very important with clay that once you have placed and puddled it to not let the material dry out as it will crack so keep the water level high at all times. Importing clay into your site may not be worth the effort when you consider the alternatives.

• Gley
  

    Related to the word 'glaze', a gley is like a biological plastic membrane such as is found in bogs, which is formed by a bacterial process that requires anaerobic conditions.
traditionally a technique for sealing ponds and dams, there is potential for the process to be adapted for human-made structures.

    The Russian-devised version for dams uses a slurry of animal waste (pig manure) applied over the inner base and walls of the dam in multiple, thin layers, which is then itself covered with vegetable organic matter such as grass, leaves, waste paper, cardboard, etc. This is all then given a final layer of soil which is tamped down and the mixture is left for several weeks to allow the (anaerobic) bacteria to complete their task, at which time the dam is ready for flooding.

    Unlike bentonite clay, gley materials are virtually cost-free and are comprised of 'wastes' which would normally be discarded in the normal course of operations.  Also, plastic and rubber dam liners may actually be dependent on the same anaerobic process for their own continued effectiveness rather than their lack of holes or punctures ­ i.e, it is the anaerobic layer created below them rather than their own membranous qualities which prevent water seepage in the long term.

• Synthetic Liner
  

  Our neighbour was not happy about the pond building and was very concerned that leakage could damage her property so we opted for a synthetic liner in the end. Here is a quote from the firm that sold us the liner:

 "Liner is constructed out of a tightly woven inner core of high quality LDPE sandwiched between two laminated layers of rot-proof and UV resistant coating.  This manufacturing process makes our liners extremely tough and durable yet lighter to handle and move into position when pond building. Liners are approximately 0.3mm thick with a minimum weight of 200 grammes per square metre."  click here for a link to the website.

  If you are using a Liner than you will need to know how much liner you will need for your proposed pond. You can simply type in length ,width and depth into a calculator to work this out. Click here for Liner Calculator

  To line the pond you need to:

• dig down a further 15cm than your required depth
• remove any stones or sharp objects from the soil which could puncture the lining
• place a layer of old carpet , cardboard, sand , or sieved soil under the liner for protection
• put in place the liner
• add 6cm layer of sand to cover liner
• add stone free soil to support plants
• fill the pond with at least some water from nearby pond to bring in microscopic life forms and eggs
• place your plants and watch it all come to life

  

   When digging the pond you can use the top soil for other areas in garden or store for later use as it is very valuable.   The sub soil can also be used in the garden  to create relief or perhaps mixed with compost a mound for a future herb spiral or some other landscaping.  Have a plan for this before you start digging.  We used the top soil for a potato hill which, in short,  is an intensive method for growing potatoes where the soil is built up around the potato plants thereby stimulating the growth of potatoes all the way up the stem.   We also used some of the topsoil to put back over the edges of the pond before we sowed white clover.  

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Pond Ecosystem

  When creating a water garden you must consider the plants you will use and their needs, the chemistry of the water and the needs of other living things within the pond.

Plants

   We can think of aquatic plants in 4 separate groups determined by their preferred habitat.



Emergent /Marginals
Or only partially submerged, such as Catails/ bullrushes latin name Typha

Fully Submerged/ Oxygenators
Water weeds like water milfoil Myriophyllum sp.

Deep Marginals  
The leaves float on the surface, but the roots are anchored in soil beneath the water, plants such as Water -lily Nymphaea 


Floaters
The plants float on the surface and the roots are suspended free in the water, plants such as Duckweeds Lemna minor


Algae
Algae will be the most successful plant in your pond. It is the green sludgy stringy like substance. The alga thrive in warm sunlit conditions and are very fast consumers of nutrients. If you have high levels of organic matter (leaf shed, excrement) than the algae will consume it at an incredible rate.

  Algae can cause considerable disturbance in the pond ecosytem by

• decreasing light filtration
• consumption of oxygen levels
• reducing surface intake of oxygen

  It's worth mentioning that algae get bad press due the destruction that they cause in natural lakes and ponds but please remember that they can only cause this destruction because they are over fed with chemical fertilizers that have leached into these water bodies from a farm or nearby housing estate.

Solution is the problem

   Algae is very high in nutrients and can be used to make plant feeding brews can be added to make compost can be feed to animals including the human. If you see it building up than take it out and put it to use elsewhere.  Also practice this if you see algae blooms around you.

  You should research and base your selection of plants on those that are growing local to your site.  Exercise caution against introducing foreign species of water weeds.



Chemistry of the Water

   Photosynthesis: During sunny days plants are creating oxygen and absorbing carbon dioxide, when there is no sunlight this process reverses (respiration) and the plant exhales carbon dioxide and takes in oxygen.  Aquatic plants act the same, but the exchange of carbon/oxygen takes place in the water body. It Is important to consider the levels of carbon and oxygen in the water and understand their implications in order to achieve a healthy and stable system.

  During periods of cloudy weather the plants cannot photosynthesis and are in fact taking oxygen from the water and producing carbon dioxide. The balance of the pond's production of  O relative to C is thrown off.  When pond surface is covered by too much growth this also reduces the ability for the lower plants to photosytnthesise and reduces the area on the surface for the water to take in oxygen from the air.

   The shedding of dead leaves, other organic matter falling into the pond and excrement from pond life also contribute to this relationship between C & O as the bacteria that decompose this material use oxygen further depleting levels.         

  So how do we get the balance right ????  Mimic nature :)

    We have created a suitable habitat for a diversity of plants and animals. We have selected native plants that are already well adjusted to the local condition. Now we need to learn in what proportion we need these plants. 

    The plants that can cover the water surface inhibit excess light feeding the algae and we want to aim for these to cover 60% of the surface.  This will allow sufficient light through to lower levels plants.  Submerged plants should be distributed 1 bunch per 1/5th of a square metre.  These plants are oxygenators and will keep nutrient levels suitable.  We need to monitor levels of fish and amphibians, as natural predators are fewer in a garden environment unless of course you are the predator as will be the case in our ecosystem.  Too many fish in the pond will disrupt the balance.

   Bear in mind that a stable system is the result of natural succession and a natural healthy system needs to evolve.  We can try to get it there as fast as possible with good design and we can also integrate the pond management into our system .i.e fish control for food, organic removal for mulch, algae control for chicken food.

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Plants : Choosing, Growing and Propagating

Pond planting Plan

These are the plants we chose for our pond design, all of which we obtained from local waters.

Emergent/Marginals
Cattials Typha
Water Plantain Alisma
Sedge Carex
Pickerel Weed Pontederia
Yellow Iris iris pseudacorus

Oxygenators
Water Milfoil Myriophyllum sp.

Deep Marginals
Water lilies

Floaters
Duckweed Lemna minor

  Duck weed is a great chicken and duck food and replicates very fast so can be used as a regular supply of spring and summer food for them.  It is also edible for us.  Find below a list of other edible aquatic plants.

 Edible Plants of the Pond 

Shore line planting

   Once the earth works were complete,  we sowed clover seeds onto the surface which bind the soil preventing erosion, creating fertility and providing a good food for chickens once established.  

White Clover     Trifolium repens

  We also planted Perennial herbs along the higher banks to bind the soil such as:

Mugwort     Artemisia Vulgaris
Yarrow         Achillea millefolium
Stinging Nettle Urtica dioica

Growing

   In a marshy area you can place the emergent plants directly in the soil, but be aware of the invasive nature of these plants -  you will need room for them to spread. They make great mulch material.

   If you are stocking your pond from local waters than once you have dug them out, place them in plastic pots ready for placing in the pond. This is very helpful in the initial stages of planting as you can easily change the position of your plants.  You can use standard plant pots but plug the holes so that the nutrients cannot escape from the pot and spill excess residue on the pond floor, otherwise any plastic tub will do like a ice cream tub. The best pots are wider than they are deeper as most aquatic plants are shallow rooted.    You can also plant them directly into the soil.

   If planting in pots, use top soil  from garden with some clay content as this will make the pot heavy, ensures that it will sink and hold  nutrients.  Do not use sub soil from the pond digging,  even though you are going to have tons of it.   For really healthy plants you can change the soil every few years or add compost to the pots yearly.

Propagating

   The principal ways of propagating aquatic plants is by division and separation, it's really easy to do and you can quickly build up a very large supply of aquatic plants this way. 

• Division : in its most basic form involves sectioning the plant into rooted pieces and re-potting.  The plant roots should be cleaned with water to determine points of division that include growing points or growing eyes along with supportive root.

• Separation : This involves the separation of bulbs or corms from the mother plant
  

Fish Rearing and other Pond Animalia

Domestic Carp Rearing

   For small ponds the best fish you can consider keeping for food is carp.  It is important that the depth is at least 1m so that they can survive in the winter months.  The width and length can be as little as 3x3m.   Do not let populations grow too high,  as the pond ecosystem will suffer from oxygen depletion.   The fish will find the majority of their food from within the pond, but as the ecosystem establishes itself you can feed them manure and grain.

  You should stock your pond in the spring with baby carp.   In around three years you will have plate-size fish which make a very presentable family supper.   The best months to harvest them are November to February.

  For successful breeding the spawn needs to separated until they are big enough to not be eaten by the other fish.     

  We introduced some Pumpkin Seed Fish Lepomis gibbosus into our pond which we caught with line from nearby lake.  They predate upon mosquito larvae and are part of our mosquito control team.   Frogs quickly occupied the water and a whole host of aquatic insects have also made themselves comfortable.   These would have come in with the plants as well as the 4 or 5 buckets  of pond water from a  nearby pond we had added.