What Is A Borehole: A borehole is a generalised term for any narrow shaft drilled in the ground, either vertically or horizontally.
A borehole may be constructed for many different purposes, including the extraction of water or other liquid (such as petroleum) or gases (such as natural gas), as part of a geotechnical investigation or environmental site assessment, for mineral exploration, or as a pilot hole for installing piers or underground utilities. Boreholes used as water wells are described in more depth in that section.
In the engineering and environmental consulting fields, the term is used to collectively describe all of the various types of holes drilled as part of a geotechnical investigation or environmental site assessment. This includes holes advanced to collect soil samples, water samples or rock cores, to advance in situ sampling equipment, or to install monitoring wells or piezometers. Samples collected from boreholes are often tested in a laboratory to determine their physical properties, or to assess levels of various chemical constituents or contaminants.
Casing The Borehole: Typically, a borehole used as a well is completed by installing a vertical pipe (casing) and well screen to keep the borehole from collapsing. This also helps prevent surface contaminants from entering the borehole and protects any installed pump from drawing in sand and sediment. When completed in this manner the borehole is then more commonly called a well: whether it is a water well, oil well or natural gas extraction well.
Groundwater is one of Zimbabwe’s most valuable natural resources. Even though most large cities get their water from surface sources such as lakes, rivers, and dams, it is estimated that there are ten times as much freshwater below the land surface than in all the lakes and rivers combined. Groundwater is a far safer water source than surface water because it is protected by soil or rock, and is not so easily contaminated. A properly constructed water well is the best way to ensure that the water you drink is safe and clean.
A properly constructed borehole or water well should last a lifetime. Whether drilling a borehole for industrial units or for a domestic supply there a several important key factors which should be considered before drilling proceeds.
In the engineering and environmental consulting fields, the term is used to collectively describe all of the various types of holes drilled as part of a geotechnical investigation or environmental site assessment. This includes holes advanced to collect soil samples, water samples or rock cores, to advance in situ sampling equipment, or to install monitoring wells or piezometers. Samples collected from boreholes are often tested in a laboratory to determine their physical properties, or to assess levels of various chemical constituents or contaminants.
Casing The Borehole: Typically, a borehole used as a well is completed by installing a vertical pipe (casing) and well screen to keep the borehole from collapsing. This also helps prevent surface contaminants from entering the borehole and protects any installed pump from drawing in sand and sediment. When completed in this manner the borehole is then more commonly called a well: whether it is a water well, oil well or natural gas extraction well.
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| What Is A Borehole - Your Complete Guide To Borehole Drilling in Zimbabwe |
A properly constructed borehole or water well should last a lifetime. Whether drilling a borehole for industrial units or for a domestic supply there a several important key factors which should be considered before drilling proceeds.
- The location of the borehole and the design should be uppermost, the borehole should be drilled as far away from any potentially harmful contaminants as possible.
- The minimum yield, this is the least amount of water the borehole would produce in order to make it viable.
- The geological formations that will be drilled and the chances of potential aquifers.
- The depth and the diameter of the finished well, varies on smaller projects depending on drilling conditions but is important on larger ones as pumping equipment must be planned for at the outset.
PERMEABLE VS IMPERMEABLE SURFACES:
What Is Permeable: A permeable surface is one that allows water to pass through it, and an impermeable surface doesn’t allow water to pass through it. An example of a permeable surface would be soil or gravel and an example of an impermeable surface would be granite or slate.What Is Impermeable: Because rocks are hard you might be inclined to think that they are impermeable, but not all are. Some rocks have tightly bound particles that don’t allow water to move through them, whilst others have round loosely bound particles that allow water to pass through them. Permeable rocks are generally porous and are crumblier, one example being sandstone.
Ground Matter: So why does the makeup of the ground matter? Well, when it rains, water seeps into the ground travelling through permeable materials deep into the earth, sometimes even thousands of meters deep.
Water Collection: When the water reaches an impermeable layer of material, the water can’t travel down any further and so starts to collect on top of the impermeable material. These water-filled sections of soil sand and rock are known as aquifers, which is what’s needed for a water borehole.
To access the aquifer a specialist drilling company will need to come and drill a vertical hole into the ground to the depth of the aquifer. A special casing will need to be inserted into the hole to keep debris from falling in and to stop it from collapsing.
Water Pump Pipe: Once the hole is drilled and everything is in place, the water pump is ready to be inserted. A submersible pump, fitted with a sediment screen, attached to a length of pipe is lowered into the borehole to reach below the water level. This serves to pump water out of the aquifer to the surface.
Having a viable borehole isn’t quite as simple as having water underground, there needs to be a great enough quantity for your needs. Whether or not there is enough water will depend on how much water is entering the aquifer, as well as the characteristics of the base impermeable layer.
Gravity: Groundwater acts in the same way as surface water, in that gravity causes it to flow downwards. This means that water collects in the deepest point of the impermeable layer. The level of this water (the water table) is dictated by the amount of water feeding the aquifer.
Distance: Not only do you need to consider the amount of water available, you also need to consider the depth of the aquifer. In some places you may only need to drill 20 meters to reach water, however, in others, you may need to drill 300 meters. The cost of drilling increases as the depth increases and so it can be economically unviable to pursue a water borehole.
So why does the makeup of the ground matter? Well, when it rains, water seeps into the ground travelling through permeable materials deep into the earth, sometimes even thousands of meters deep.
If managed correctly, boreholes can be a great source of reliable water. They make great water sources for a variety of users including domestic communities and commercial enterprises.
Contact Borehole Experts Zimbabwe for advice and recommendations on the right pump to achieve your required flow rate, as well as help with water purification and maintenance.
HOW DO YOU ACCESS THE AQUIFER?
To access the aquifer a specialist drilling company will need to come and drill a vertical hole into the ground to the depth of the aquifer. A special casing will need to be inserted into the hole to keep debris from falling in and to stop it from collapsing.
Water Pump Pipe: Once the hole is drilled and everything is in place, the water pump is ready to be inserted. A submersible pump, fitted with a sediment screen, attached to a length of pipe is lowered into the borehole to reach below the water level. This serves to pump water out of the aquifer to the surface.
Having a viable borehole isn’t quite as simple as having water underground, there needs to be a great enough quantity for your needs. Whether or not there is enough water will depend on how much water is entering the aquifer, as well as the characteristics of the base impermeable layer.
Gravity: Groundwater acts in the same way as surface water, in that gravity causes it to flow downwards. This means that water collects in the deepest point of the impermeable layer. The level of this water (the water table) is dictated by the amount of water feeding the aquifer.
Distance: Not only do you need to consider the amount of water available, you also need to consider the depth of the aquifer. In some places you may only need to drill 20 meters to reach water, however, in others, you may need to drill 300 meters. The cost of drilling increases as the depth increases and so it can be economically unviable to pursue a water borehole.
So why does the makeup of the ground matter? Well, when it rains, water seeps into the ground travelling through permeable materials deep into the earth, sometimes even thousands of meters deep.
If managed correctly, boreholes can be a great source of reliable water. They make great water sources for a variety of users including domestic communities and commercial enterprises.
Contact Borehole Experts Zimbabwe for advice and recommendations on the right pump to achieve your required flow rate, as well as help with water purification and maintenance.
