An artesian well is a pumpless water source that uses pipes to allow underground water that is under pressure to rise to the surface. This type of well seems to defy gravity because the pressure that builds up between layers of rock gets relieved when the water finds a path to the open air. In addition, the water has been naturally filtered because it passes through porous rock as it seeps into the Earth to reach the aquifer, which is the underground water source. For centuries, people have drilled artesian wells to drink filtered water that doesn't need to be manually or mechanically hauled up from the depths.
An aquifer provides the water source for an artesian well. This is the layer of permeable rock, such as limestone or sandstone, that absorbs water from an inlet path at high elevation, such as the top of a mountain. The water source might be fed by snowmelt or precipitation.
Porous stone is sandwiched between a top and bottom layer of an impermeable substance, such as clay soil or shale rock. This keeps the water pressure high, so that at a point below the entryway of the flow, there is enough pressure to bring the water up when the pressure is released. Natural springs form in the same way when a gap in the impermeable rock — perhaps triggered by an earthquake — allows the water to rise to the surface. Sometimes, if the pressure is especially strong in the aquifer, the water might thrust up like a fountain and form a geyser.
Artesian wells are found all over the world. Entire cities have relied on giant underground aquifers to provide fresh, cold water when there are no above-ground rivers. Where modern plumbing is scarce or nonexistent, people often must rely on an artesian well for clean water. The Great Artesian Basin, which provides fresh water to inland Australia, is the largest such basin in the world. Thousands of artesian wells have tapped into this aquifer.
The first known artesian well was drilled in 1126 by a group of monks who used a rod with a sharp end, called a bore, to penetrate a layer of impermeable rock to reach an aquifer. Their percussive drilling — just hammering on the end of the bore — broke through the rock with sheer human force. The water that rose to the surface had seeped through the pores of the rock, so that many contaminants have been filtered out, and it proved to be safer to drink than standing water from the surface or river water.
How Does an Artesian Well Work?
Artesian wells are a natural effort-saving innovation that requires no extra mechanics or filtering to obtain useable water. The word “artesian” comes from the French region of Artois where the technique was documented in the 12th century C.E. The water in an artesian well comes from an aquifer, a fancy term for a piece of rock or sediment that’s holding the water.
Water enters aquifers through soil drainage, also known as groundwater recharge. Rainfall is a chief source of groundwater recharge. This subsurface water fills in empty spaces inside and between rock and soil layers. For sufficient groundwater recharge to aquifers, rainfall levels must exceed what’s lost by evaporation or used by plants growing in the soil. Around 10% to 20% of precipitation on Earth makes its way into aquifers as groundwater.
Deep in the ground, pressure created between the rock layers can push groundwater up to the surface. While this groundwater remains trapped below the surface, the resulting pressure that builds up is called artesian pressure. The magnitude of this pressure can vary from well to well. The aquifer itself that contains the water is called an artesian aquifer.
How To Make an Artesian Well
Drilling is required to access groundwater and create an artesian well. You’ll commonly see these wells include a pipe or discharge line through which the water can rise. But their design doesn’t end at just drilling a hole and sticking a pipe into the ground. Flow control may be needed to avoid water waste and erosion, but it also may be required by state or local laws. And while many artesian wells produce clean water, some may require disinfecting measures to remove harmful microbes and toxins.
Controlling an artesian well’s flow can be done by adding a secured cap at the top of the pipe. This cap stops water from free-flowing out of the well, but it also shields the well from vermin, chemicals, and other contaminants. Along with this cap, the well can be equipped with control valves and pressure relief fittings. These controls prevent excess water from escaping, which in turn ensures that the well doesn’t prematurely run dry. Depending on the well’s design and the user’s needs, cement grout may be needed for proper sealing to enable flow control.
Common Artesian Well Problems
Artesian wells can be useful water sources. However, you do need to take some unique precautions. The water you use must be safe, but you must also take care to avoid problems such as erosion and water waste. Testing, decontamination, flow control, and sealing are some key issues you may need to consider.
Scientists estimate that Earth’s upper crust holds nearly 6 quintillion gallons of water. This water supply chiefly resides in the upper 1.2 miles of our planet’s surface. While the porous rock in the crust acts as a filter, groundwater can still be contaminated by fracking, landfills, and septic tanks along with industrial and agricultural chemical runoff.
Artesian well water may also contain coliform bacteria, which can be present in the soil from animal and human waste. While filtering can remove a good percentage of the bacteria, some of it may still make it into water consumed from these wells. Coliform bacteria can cause symptoms like diarrhea and vomiting, but serious illnesses such as polio and dysentery are also possible.
Proper disinfection is key to ensuring that your artesian well water is safe to use. The Centers for Disease Control and Prevent recommend testing it at least once a year for coliform bacteria, nitrates, and total dissolved solids. You should also monitor the water’s pH levels and regularly observe its color, taste, and odor. If recommended, you may need to test for other contaminants. For further guidance on testing and disinfection, check with your local health department.
Flow Control Issues
While you want to adequately control water flow rates in an artesian well, care must be taken to balance flow and pressure. One common risk is frac-out, or hydraulic fractures occurring at nearby spots in underground rock. These fractures permit water to surface in unexpected places and reduce an artesian well’s reliability and function.
If a well has been abandoned or its wall has deteriorated, you may need to discontinue using it. Such wells should also be permanently sealed with cement plugs. PVC pipes or drill rods can inject cement grout into the bottom of each well until the walls are completely filled up to the well’s exit point at the surface.