A few of Africa’s dry areas face severe water shortages resulting from minimal rainfall. An historic system of drawing water from aquifers, the “qanat system”, may assist. Gaathier Mahed, an environmental scientist and knowledgeable on the administration of groundwater, has studied the feasibility of those techniques. He tells us extra.
How does the qanat system work?
There are our bodies of water underground generally known as aquifers, a few of which may be discovered on the tops of valleys or close to mountains. A qanat system faucets these aquifers and, utilizing underground tunnels, strikes the water, utilizing gravity, over many kilometres. The tunnel then exits at a lower-lying space.
When the water exits the tunnel, farmers can use it to irrigate their crops. Folks also can entry the water alongside the stretch of the tunnel utilizing wells.
It is a system that is managed by everybody, and its advantages are shared. Everyone has a vested curiosity and a job to play. Neighborhood bonds may be strengthened – in stark distinction to tensions we see over water assets in the present day.
It is a extremely complicated communal system to handle. Legal guidelines governing the system have existed because the ninth century. These legal guidelines relate to the development and proximity of qanat tunnels to one another. In addition they govern the exits of the qanats. As an illustration, land house owners on the exits can use the water first and should assist in managing them.
The place did it come from and the place is it used?
The qanats have been used for hundreds of years in arid and semi-arid elements of north Africa, the Center East and Asia, the place water provides are restricted. It is identified by quite a lot of names, “foggara” in north Africa, “falaj” in Oman and “qarez” in elements of Asia.
It is thought to have been developed in Persia within the first millennium BC. Because the Islamic Empire unfold throughout the Arabian Peninsula, the Levant, north Africa, and elements of Europe from 661 to 750 CE, so did data about qanats.
At this time, a number of the area’s qanat techniques, like these in Iran, are protected beneath heritage standing. A few of these qanats, though declining in quantity, are nonetheless used. They’re largely protected for historic and cultural causes.
Why is it not being extra extensively used?
There are a number of the reason why the tunnel system will not be extra extensively utilized in Africa.
Qanats have to be constructed someplace with the suitable geological formations. These typically appear to be fractured sandstones. The extent of groundwater can also be necessary for the circulation of water within the qanat. The quantity of water within the aquifer stems from the rainfall within the mountainous areas.
Qanats can solely be constructed the place there is a slope, like a mountain or a valley. And the slope should have a particular angle. If it is too steep, erosion of the qanat will happen and it’ll collapse. If it is not steep sufficient the water is not going to circulation quick sufficient and will turn into chemically altered resulting from interplay with minerals within the floor.
The digging of the tunnel and growth of the system over giant areas of land is labour intensive and might take a few years. The qanats cowl many kilometres and have to be maintained yearly, by cleansing out the silt build-up.
Information of constructing qanats and sustaining them is being misplaced. Folks have migrated from rural areas to cities and adopted boreholes in sure areas as an alternative.
Some qanats are drying up resulting from over exploitation of the water useful resource.
Why ought to the system be used extra extensively?
In most cases folks in arid areas drill wells to entry groundwater. These boreholes have a lifespan and ultimately new wells should be drilled. Pumps and supplies do not final without end, and wells can get clogged by microbial organisms and fantastic materials within the subsurface.
First, the qanat is sustainable as it really works with gravity and no electrical energy is required. It may well even be used to create clear power. As an illustration, in Iran chilly air that comes out of qanat tunnels is used to chill the inside of huge buildings.
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Second, water misplaced to evaporation is minimal compared to floor water provides.
Third, it could have a large scale affect. Qanats are a number of kilometres lengthy and as soon as this water hits a floodplain, it could irrigate a number of hectares of land.
Fourth, it fosters social cohesion. Many individuals, with totally different abilities, are concerned in sustaining the system.
Fifth, the lifespan of the system extends past that of a deep water nicely, which is just about 20 years. Tunnels don’t clog as simply as wells.
Lastly, the standard of water coming from the mountains is a lot better than water on the plains. It’s going to have decrease salinity and be higher for crops and folks.
Gaathier Mahed, Senior lecturer, Nelson Mandela College
