iAVs had its roots in a quest to develop a new method of agriculture for arid-zone underdeveloped regions such as the African Sahel.
While the following images depict the development of such a low-cost, low-tech iAVs, a similar system can meet the needs of a family of four for fresh fish and nutritious vegetables……in a space no larger than a parking spot at your local supermarket.
Proportions depicted are approximate and the materials and configuration can be varied to suit the resources and skills of the user.
In its simplest form, an iAVs comprises a grow bed containing medium-coarse sand (which functions as the bio-filter and plant substrate) which drains into a fish tank.
The grow bed and fish tank can be made watertight with puddled clay, plastic liner or fibreglass.
Furrows are formed in the sand and seedlings are planted into the high sections of the furrows.
Nutrient-rich water is intermittently transferred from the fish tank into the furrows.
As the water percolates down through the sand, the fish solids are trapped and mineralised and become nutrients for the plants. The clean water drains back to the fish tank.
This symbiotic partnership will see the water recycled up to 300 times before it is used up by the plants.
The reddish tint in the image represents a liner of expansive clay (where available) as an alternative to synthetic membrane for water retention. The weir could be woven stick and thatch, or brick/rock wall, scrap tin, logs & mud, boards……whatever is available. Many alternative configurations…..both low/hi-tech are possible.
The image above shows a pipe or hose to move water to the far end of the bio-filter This is not actually necessary. Return (drainage) with cascade aeration is not clearly depicted.
The example above illustrates water transfer by means of a mechanical hand-operated pump. Could also employ solar-PV, a shadoof, animal-powered pump, windmill or even a simple calabash (bucket on a rope/stick).
The iAVs provides for 100-fold greater water use efficiency over traditional pond culture of tilapia with (the nutritionally and economically dominant) vegetable production for the same amount of water that it would take just to grow the fish.
Total annual water consumption is as low as 5 cubic metres/year for each cubic metre of fish culture volume – with a significant fraction of that water use in the form of edible biomass.
Credits: Pastel renderings by Brandy Noon, a Kenyan, circa 1992. Captions by Mark R. McMurtry.
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