People dig wells to serve as an independent water supply system. These days before a well is dug, a survey is carried out on the site to determine the amount of water beneath the ground, its location, and yielding capacity. This will determine the type of well to be dug.
Types of wells
Generally wells can be categorized into 2 types;
Deep well and shallow well.
From an economical point of view,A well is considered deep when the length of the well is over 25ft or 7.62m deep. What causes the digging or boring of a deep well is as a result of the water table being too far from the top soil. Another reason for a deep well is if although, the water table is not far from the top soil, the soil beneath the water table doesn’t yield water, then the well has to be dug further down to locate the water yielding soil. Types of soil that hold and yield water are those of sand or rock formations. A type of soil that holds water but doesn’t yield it is a soil that consists mostly of shale.
Another definition of deep well is a well that extends several meters below the water table. Meaning that its source of water is not from the water table but from other water bearing stratum beneath the water table.
A deep well can extend up to 300m.
A well is considered shallow if the length is less than 25ft from the surface. This is because the water table is not too far from the surface and the soil directly under the water table yields water.
Shallow wells are also referred to as water table wells. Meaning, the source of water for these types of well is the water table. It also implies that if the water table is further down the earth ( over 25ft), the shallow well extends about the same length or more. Based on the location of water table, shallow wells can be over 35m in extreme cases.
Types of constructed wells
Generally they are of 3 types;
Hand Dug well.
A dug well is done using hand tools. A pick and shovel to dig the shaft, and a bucket and rope to lift out soil. This type of well cannot be dug a few feet below the water table. If the water table is very far from the surface ( over 10m deep),then a hand dug well may not be economically and practically viable. Most hand dug wells for private dwellings are less than 10m deep. Hand Dug wells are always shallow wells and they are the least costly.
A driven well consists of pipes driven into the ground. The drive point is usually twisted into the ground by hand or powered auger. This type of well is suitable for Sandy soils and cannot be dug through rock formations. The well can be driven up to 100m. It can be shallow or deep,depending on the nature of the soil and water yielding characteristics.
Bored or drilled well
This type of well is also called bore hole. It also consists of pipes much larger than that used in a driven well, bored into the ground using a heavy drilling machine. Bore holes can reach depths of up to 300m and can be drilled through rocky formations. Boreholes can either be shallow or deep, depending on depth of water table and water yielding characteristics of the soil. It is the most expensive of the types mentioned in this article.