Water Budgeting in Fish Farming

Evaluate the availability and sustainability of a water supply.

I want to share a comment that came from my friend, Agricultural Engineer and an enthusiastic potential fish farmer. He criticised the use of Dam/Pond Liners in Fish farming. At first I understood his comment he said, “I attended a lecture where I was told, Dam lining is a quick fix for poor pond construction”.  What do you think?

Well, I think that dam lining is a solution for special sites, an example of areas with high soil permeability or insufficient flow of water resources. Regardless of how much one compacts, the soils in some special geographical locations don’t have properties that inhibit seepage. Some areas have adequate water resource but the extent of productivity may demand large amounts of water. To strike a balance a farmer needs to evaluate how much water is being supplied compared to how much is being lost through seepage. I have a lot of farmers who own fishponds that consume more than what can be sustained. These farmers have ended up having semi lined ponds or having both lined and earthen ponds on the same piece of land that has ideal soil types. Let’s get this right and correct.

There has been a growing trend of using pond liners, usually promoted by alleged aquaculture specialists in the sector, some of which are preying on clients to sell them dam liners and avoid the hefty exercise of soil compaction, an attempt to evade the principle processes of ideal pond construction. Hired contractors will make quick money from a rough structure and from the sale of liners to their clients.

On the other hand, there are a good breed of an honest, fully baked and credible Aquaculturist who will only recommend the use of Dam liners after evaluating the availability and sustainability of a water supply. They understand water budgeting in fish farming. A water budget simply states that the rate of change in water stored in a fish farming facility, such as fish pond, fish tank, is balanced by the rate at which water flows into and out of the farming water system or structure.

How good the soils can hold water, determines whether an alternative to use liners or concrete can be recommended or not. Not all soil types can dictate for use of Dam liners or cement, but complete earthen.

By definition water budgeting is the allocation of water receipt including anticipated within the entire fish farming production period and its detailed account of expenditure for efficient and profitable farm management.

Earthen ponds lose water through see page and evaporation and based on soil type, permeability is equally dependent on how well a pond is compacted. Therefore, it is possible to make the soil impermeable by simply following the primary principles of dyke and bottom construction of a pond.

In areas were the soil is found to be highly permeable, a dam liner may be recommended. You have to understand how to evaluate the availability and sustainability of a water supply, thus you don’t want to lose any water because you want to maximize its usage.

By principle, it is recommended that a contractor selects a site that has soils with low permeability, preferably clay or mixed. This type of soil can then be subjected to a series of steps of compaction in quantities of at least 150mm or 200mmhigh of soil layers. Top soil has to be removed completely and used at the end. Ponds have to be constructed on a gentle slope to allow for complete draining of a pond. The slope is equally essential in that it lessens the burden of digging large amounts so that one can easily cut and fill during slope construction.

For the sake of durability and strength of structures, both earthen and Dam lined ponds must be constructed with perfection, good enough without forgoing the essence of compaction. You don’t want your fish to be deprived of adequate water, primary source of dissolved Oxygen. The amount of water in a fish pond is usually proportional to the availability of dissolved oxygen. The demand for oxygen in your ponds is always constant with activities and biomass of aquatic flora and fauna. Therefore, you don’t want to risk losing any water from your fish ponds.

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By Alex  Choompo