Wells have been used ever since human civilization stopped migrating to develop settlements and needed safe drinking water that was close to their homes. In the past, it would have been common that dug wells were the majority of wells, but now there are various types of well including the drilled well and artesian well. The type of well you use is dependent on a number of factors; one of them is the often confusing issue of groundwater level.
Groundwater and Water Wells
Groundwater is the water that is located in rock formations and soil pore spaces. Typically groundwater is thought of as a liquid, but it can include soil moisture and permafrost. The depth at which the ground is completely saturated with water is called the groundwater table.
The biggest issue for owners of private wells, is the groundwater table level is not consistent all year round. It would be easier for owners if it were, but due to seasonal changes in weather and rainfall the level of the water in the ground can rise and fall. Plus the demands placed upon groundwater can lower the groundwater table below what they were originally.
Types of Water Wells
There are four types of water well; each has its own advantages, disadvantages and construction methods.
• Dug Wells - Dug wells were probably the first type of well developed. As the name suggests the dug well is a well that has been dug out from the ground, normally with a shovel or backhoe, to a level just below the groundwater table. The well had to be then protected from collapse by sealing the edges with stone, tiles or other material. This type of well is normally very shallow averaging between 10 and 30 feet but has the highest risk of contamination.
• Driven Wells - Driven wells are simply constructed by a point being hammered into the ground with a tripod and driver. Pipe sections are added to the system as necessary and when groundwater is encountered the system is flushed of sentiment and a pump installed. Driven wells are normally produced in areas of thick sand and gravel where the groundwater level is about 15 foot from the surface and there are no large rock formations in the ground. The depth of driven wells can be deeper at about 30 to 50 foot but still have a high chance of contamination.
• Drilled Wells - Because they have to penetrate the bedrock fractures containing any groundwater, drilled wells can typically be 100 to 300 foot deep. They are three main methods of drilling for water in use today: top-head rotary, table rotary or cable tool drilling. Drilled well nowadays are pretty good at being protected from contaminants.
• Artesian Wells - An Artesian well use a type of water called artesian water to supply them. Although the water is not different in makeup, how it supplies the well is.
Artesian aquifer (water) is that which is confined between impermeable rock layers that result in positive pressure. If this water is tapped by a well it may rise above the normal level of the groundwater table and could flow onto the land (or through the artesian well) when it has come into a state of hydrostatic equilibrium. The continued flow of these wells is achieved when the water table’s recharge height is higher than the well head’s – a good example of an area where this might occur is valleys.
The biggest artesian basin is in Australia and is known as The Great Artesian Basin. Through much of inland Australia, it is the only reliable source of freshwater and relied upon heavily. If you have further questions about well drilling contact us.