Difference Between a Dug Well and Drilled Well

Wells can extract water from the ground by digging or drilling. Water is brought until ground level by pumps or by drawing it out from well through buckets or large utensils. Dug wells are generally used in rural areas. Drilled wells are made using drilling machines and go deep into the soil to draw out water to the surface. 

Dug Well vs Drilled Well

The main difference between Dug well and Drilled well is that the Dug well is a traditional way to obtain water where a shallow hole is dug down into the water table. The water obtained by dug well can get contaminated as it is extracted from the topmost layer of soil. Whereas in Drilled well, a hole is drilled deep in the soil for the extraction of groundwater from the groundwater table.

A dug well is generally hand-dug in rural areas or a shovel is used hence it is shallow. It obtains water from less permeable and top layers of soil like sand, silt, and clay. It has a high chance of getting dry during dry weather when the water table level drops below the groundwater level. 

A drilled well is drilled deep into the ground by a rotatory drilling machine. The drilling machine is cased within a protective covering to prevent the collapse of the driller when it strikes hard rocks. A drilled well can be up to 300-400 meters deep and the chances of water contamination are almost negligible. 

Comparison Table Between Dug Well and Drilled Well

What is Dug Well?

A dug well is generally seen in rural areas or in some localities of the urban areas that have been built years ago. A dug well is shallow and the water that is retained is highly contaminated by either pollutants or minerals. Intaking untreated well water can affect an individual’s health and might lead to diseases like cholera, typhoid, diarrhea, etc. 

The water is extracted from the dug well through pumps or hand-drawn. There are high chances of water getting exhausted during the dry season as dug wells draw water from topmost layers of groundwater table like sand, silt, and clay. 

After digging the well, it is protected by building bricks or concrete materials so that it does not collapse due to seepage of water. Nowadays, the dug wells can also be built using machines and hence they are constructed with a larger diameter. 

The dug wells need low technology means and are inexpensive. It generally needs manual labor to access groundwater. The lifespan of dug wells depends upon the climate and nature of rains as they are responsible for filling up the groundwater table. It might last up to 10-20 years if rains are good or might get dry in just 5 years in dry areas.

What is Drilled Well?

A drilled well is drilled by table rotary, or cable tool drilling machines which creates a cutting action in-ground or on hard rocks. The depth of these wells might range from 300 to 900 meters. 

The drilled wells use PVC or metal pipes that pull out water from the bore but water can be muddy since it is extracted from deep strata of ground so a semipermeable screen or casing is used to protect and filter the water. 

To avoid contamination through pathogens, the surface seal is used that provides an impermeable barrier between the outside environment and well. The drilled wells are mostly used to extract water but also for retrieving petroleum and other useful hydrocarbons from the ground. 

The water is pulled out from the ground using electric pumps as much energy is needed to pull out water from such a depth. Most drilled wells last up to 30-50 years. The drilled bit used in the drilling machine is made up of tough materials like tungsten and as the drill is rotated it starts up to grind the rocks, drills the ground, and then back to the surface. 

Main Differences Between Dug Well and Drilled Well

1. Dug Wells are either hand-dug or dug by shovel. Drilled wells are drilled using a rotary drilling machine.
2. Dug wells have a shallow pool and extract water from the topmost layers. Drilling wells can reach up to 300-400 meters or 1000 feet deep into the ground.
3. The water extracted from the dug well is high in minerals and hence needs to be treated well. The water extracted from drilling wells is muddy until it passes through a semipermeable membrane that filters out the impurities. 
4. Water from dug wells can be drawn out using handpumps, electric pumps or can be hand-drawn. Water from drilled wells is pulled out using suction or electric pumps.
5. Dug wells are used in rural areas for everyday use at homes. Drilled wells are used in urban areas at home or in factories as groundwater level is low in cities.

Conclusion

Wells were invented to bring water and in some cases, petroleum, natural gases, or other hydrocarbons out from the earth’s surface so that they can be used by humans for their needs. Over-excessive use of these resources is making them deplete. 

The wells can either be dug or drilled. Dug wells are shallow and have high chances of contamination as they extract water from the uppermost strata of soil which is prone enough to pathogens and industrial pollution. Dug wells were preferred in older times and can be seen mostly in rural areas. It has a lifespan of 10-20 years. 

Drilled wells are 300-900 meters deep and are drilled by machines that have their tip made up of tough metals like tungsten. The tip is protected with a casing so that it does not get broken when it hits hard rocks or surfaces at the bottom. It is used at home to extract water from borewells or for industrial use to create oil and gas wells. It can be used for 30-50 years until it gets exhausted.

References 

1. https://doi.org/10.1080/03067319.2020.1800000
2. https://doi.org/10.2118/119366-MS