Afrikaans
When groundwater is extracted from dry areas it is often unsuitable for irrigation, although it would be ideal for aquaculture.
Due to the lack of available water, aquaculture in the desert sounds like a non-starter.
There are however, several places in Southern Africa that have ample groundwater that could be used for irrigation and aquaculture.
The Kalahari-Karoo multifaceted aquifer stretches from eastern Namibia to southern Botswana and into western South Africa.
High-volume pumping is used to prevent flooding in mines that penetrate deep into this aquifer.
It makes perfect sense to run such water through fish ponds. The fish ponds are fertilised to increase primary productivity and as a result natural food for the fish.
A percentage of the water could be used for irrigation, after passing through the ponds.
The swathes of green around Upington are testimony to irrigation projects in desert areas that benefit from a long growing period and the abundant sunshine.
Mineralisation causes groundwater to not always be of a suitable quality for human consumption. Sodium chloride (salt) is one of these minerals, which is fitting for tilapia culture even at concentrations of up to 20ppt (parts per thousand).
The maximum recommended salt content for irrigation usually 2ppt to 3ppt making such water is too saline for agriculture.
Fish diseases and parasites are usually absent as the desert groundwater is isolated from surface contamination, making the water effectively sterile.
If there is groundwater available in parched regions, aquaculture can take place in several forms; for example, large ponds can be built where suitable land and soils are available.
Open-cast mines, would do well to consider extensive aquaculture projects using lined or unlined ponds if they are facing a water drainage problem
Solutions are even available in climatically suboptimal areas with cold winters. Egypt successfully produces 750 000t of tilapia annually, despite its cold winter.
Source: Farmer’s Weekly
