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
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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
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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