A borehole is a long thin shaft which is drilled into the earth to seek out and extract groundwater. As reported by the Borehole Water Association of Southern Africa (BWA), it is best to speak to your local municipal offices to determine if you require authorization to drill a borehole in your neighbourhood. If approval is necessary and you have not requested it, the municipality may fine you heavily.
A water borehole is an excellent way to access pure and natural underground water. A borehole is a small open, narrow shaft that is drilled vertically or horizontally into the ground to provide access to the water table below.
Who use this means and since when?
A borehole is an ancient technique dating back over three thousand years. It originated in China where bits of bamboo attached to a heavy weight were used to drill water wells.
There are two main approaches to boreholes these days:
- Manual drilling using manual tools for fairly shallow wells up to 40 m deep.
- Mechanised drilling using light equipment or a drilling platform and heavy equipment which can reach great depths.
In some cases, the mechanised drilling machines are fitted on self-propelled mobile platforms that are much quicker and easier to use and which can drill into hard ground at great depth. They are however far more cumbersome.
The mechanised drilling machines are often too expensive for the poorest populations in rural or near-urban areas. Manual drilling techniques must not be ignored, even if they are slower and rather more tiring.
Manual drilling is a practical solution that, although tiring, is advantageous and inexpensive for water points less than 40 metres deep in soft ground such as clay or sand and soft rock like soft sandstone or limestone. Where the characteristics of the ground permit, drilling a manual borehole can prove to be more than four times cheaper than a mechanised borehole.
But in hard ground, or when wishing to drill to a great depth or avoid difficult work or go faster and the means are available, mechanised boreholes and a better, even essential solution.
What does this process involve? How is it applied?
There are in fact numerous processes and it can be fairly difficult to distinguish between them given their sometimes-curious names, which can also vary according to the engineered structures and the language used.
The aim of this sheet is to describe and clarify the main processes by distinguishing between the manual boreholes and the mechanised boreholes. The drilling techniques most used or quoted are:
- Manual Mode: hand-auger drilling for communities with few resources, percussion or cable-tool drilling (up to 25 m) and rotary sludge drilling (also called mist or rotary manual drilling, up to 35 m).
- Mechanised Mode: compressed air percussion drilling (also called down-the-hole hammer drilling or rotary percussion drilling).