AQUIFER & ARTESIAN
The picture above is taken on a foggy day from Heartland Farm, being of MOUNT WILLIAM, which forms part of the Mount William Convservation Reserve, which is Government owned and protected and located just to the north of Heartland Springs.
These two terms Aquifer & Artesian are often confused or regarded as much the same thing.
Maybe you've heard advertisements by water companies wanting to sell "artesian-well drinking water.?"
Is this water different from other bottled water taken from springs?
The artesian water may OR may not be different to spring water.
With bottled water described as 'artesian' it normally comes to the earth's surface via a bore and a well, not a natural spring.
When called artesian 'well' water one can be near sure it is not a natural spring, but is result of a hole bored into earth's surface to reach artesian water.
Let's try to further clarify the difference.
An underground store of water seems to be generically called an aquifer. Some might be artesian, some not. Some have high quality drinking water; some do not.
The more shallow the aquifer, generally the more likely it will be influenced by rainwater and or surface contamination. The deeper aquifers are likely to have higher water quality.
Some very deep acquifers may contain a naturally pure water which has not seen the surface of the earth for hundreds or thousands of years. Water tests are usually required to assess the quality of water from aquifers.
The fact the spring is flowing to the surface of earth under natural pressure, would indicate it is from an artesian aquifer surrounded by imprenatable rock, also called a contained aquifer.
A spring is where the water from the aquifer rises naturally via the aquifer's and earth's pressure (not using any drilling) to the surface of earth. Now we refer to a more expert definition, which follows.
Reference: USGS Water Science School- https://water.usgs.gov/edu/earthgwaquifer.html
Below a certain depth, the ground, if it is permeable enough to hold water, is saturated with water.
The upper surface of this zone of saturation is called the water table. The saturated zone beneath the water table is called ground water. Within or below the groundwater may be water pockets, called an aquifer or aquifers, where there can be huge storehouses of water.
At the beach level, the water table is always at the same level as the ocean, which is just below the surface of the beach.
Groundwater is one of our most valuable resources—even though you probably never see it or even realize it is there.
Some of the void spaces in the rocks below the water table are filled with water. But rocks have different porosity and permeability characteristics, which means that water does not move around the same way in all rocks below ground.
When a water-bearing rock readily transmits water to wells and springs, it is called an aquifer.
Wells can be drilled into the aquifers and water can be pumped out. Precipitation finding its way into earth, eventually adds water (recharge) into the porous rock of the aquifer. The rate of recharge is not the same for all aquifers, though, and that must be considered when pumping water from a well. Pumping too much water too fast draws down the water in the aquifer and eventually causes a well to yield less and less water and even run dry. In fact, pumping your well too fast can even cause your neighbor's well to run dry if you both are pumping from the same aquifer.
Sometimes the porous rock layers become tilted in the earth.
There might be a confining layer of less porous rock both above and below the porous layer. This is an example of a confined aquifer. In this case, the rocks surrounding the aquifer confines the pressure in the porous rock and its water. If a well is drilled into this "pressurized" aquifer, the internal pressure might (depending on the ability of the rock to transport water) be enough to push the water up the well and up to the surface without the aid of a pump, sometimes completely out of the well. This type of well is called an artesian well. An aretesian well has arisen from a hole being drilled into earth by humans; and this is NOT a spring.
The hole being drilled into earth is usually called a bore...and bore water could come from an artesian aquifer source (then its well is called an artesian well) or more likely will come from an uncontained aquifer (non-artesian) or could simply be pumped up from unprotected and if not deep then often polluted (and definitely immature) groundwater.
A spring arises naturally to the earth's surface, and can be from a contained (artesian) or un-contained aquifer (non-artesian); and a spring can also be a mountain spring, which might be from mountain groundwater more linked to rainfall (usually non-polluted due to height of moutains), but such spring is usually providing much younger water than a spring coming from a contained deep artesian aquifer.
Our spring is from a deep contained artesian aquifer.
Water movement in aquifers is highly dependent of the pearmeablility of the aquifer material. Permeable material contains interconnected cracks or spaces that are both numerous enough and large enough to allow water to move freely. In some permeable materials groundwater may move several metres in a day; in other places, it moves only a few centimetres in a century. Groundwater moves very slowly through relatively impermeable materials such as clay and shale.
Let's go straight to an expert definition of artesian.
Reference: USGS Water Science School- https://water.usgs.gov/edu/earthgwaquifer.html
Groundwater in aquifers between layers of poorly permeable rock, such as shale, may be confined under pressure.
If such a confined aquifer is tapped (drilled into) then contained by an artificial well, water may rise above the top of the aquifer and may even flow 'naturally' (along the bore hole dug into it) from the well onto the land surface. Water confined in this way is said to be under artesian pressure, and the aquifer is called an artesian aquifer.
The word artesian comes from the town of Artois in France, the old Roman city of Artesium, where the best known flowing artesian wells were 'drilled' in the Middle Ages. The level to which water will rise in tightly cased wells where water is flowing from artesian aquifers is called the potentiometric surface.
Deep wells drilled into rock to intersect the water table and reaching far below it are often called artesian wells in ordinary conversation, but this is not necessarily a correct use of the term. Such deep wells may be just like ordinary, shallower wells; great depth alone does not automatically make them artesian wells.
The word artesian, properly used, refers to situations where the water is confined under pressure in an aquifer below layers of relatively impermeable rock. Artesian pressure can be very strong.
This is how Wikipedia defines artesian and aquifer, which seems to suggest artesian is a confined aquifer which is under positive pressure:
"An artesian aquifer is a confined aquifer containing groundwater under positive pressure. This causes the water level in a well to rise to a point where hydrostatic equilibrium has been reached.
A well drilled into such an aquifer is called an artesian well, if water reaches the ground surface under the natural pressure of the aquifer, the well is called a flowing artesian well.
An aquifer is a geologic layer of porous and permeable material such as sand and gravel, limestone, or sandstone, through which water flows and is stored.
An artesian aquifer is confined between impermeable rocks or clay which causes this positive pressure. Not all the aquifers are artesian, because the water table must reach the surface (not the case for underground groundwater such as, for example, the Nubian Sandstone Aquifer System). The recharging of aquifers happens when the water table at its recharge zone is at a higher elevation than the head of the well.
Fossil water aquifers can also be artesian if they are under sufficient pressure from the surrounding rocks.
Artesian wells were named after the former province of Artois in France, where many artesian wells were drilled by Carthusian monks from 1126."
Groundwater–A major link in hydrologic cycle
From Environment Canada on web site:
Groundwater circulates as part of the hydrologic cycle. As precipitation and other surface water sources recharge the groundwater it drains steadily, and sometimes very slowly, towards its discharge point.
Groundwater does not stay underground forever, and it does not lie still waiting for us to draw it from a well.
The hydrologic cycle is the series of transformations that occur in the circulation of water from the atmosphere onto the surface and into the sub-surface regions of the earth, and then back from the surface to the atmosphere. Precipitation becomes surface water, soil moisture, and groundwater. Groundwater circulates back to the surface, and from the surface all water returns to the atmosphere through evaporation and transpiration.
When precipitation falls on the land surface, part of the water runs off into the lakes and rivers.
Some of the water from melting snow and from rainfall seeps into the soil and percolates into the saturated zone. This process is called recharge. Places where recharge occurs are referred to as recharge areas.
Eventually, this water reappears above the ground. This is called discharge. Groundwater may flow into streams, rivers, marshes, lakes and oceans, or it may discharge in the form of springs and/or flowing wells.
Groundwater discharge can contribute significantly to surface water flow. In dry periods, the flow of some streams may be supplied entirely by groundwater. At all times of the year, in fact, the nature of underground formations has a profound effect on the volume of surface runoff. While the rate of discharge determines the volume of water moving from the saturated zone into streams, the rate of recharge determines the volume of water running over the surface.
When it rains, for instance, the volume of water running into streams and rivers depends on how much rainfall the underground materials can absorb. When there is more water on the surface than can be absorbed into the groundwater zone, it runs off into streams and lakes.
The residence time of groundwater, i.e., the length of time water spends in the groundwater portion of the hydrologic cycle, varies enormously. Water may spend as little as days or weeks underground, or as much as 10 000 or more years.
Residence times of tens, hundreds, or even thousands of years are not unusual. By comparison, the average turnover time of river water, or the time it takes the water in rivers to completely replace itself, is about two weeks.
This table illustrates the estimated depth and residence time of the world's water supply:
Estimated depth and residence time of world's water supply
Parameter Equivalent depth (m) Computed as though storage were uniformly distributed over the entire surface of the earth Residence time
Oceans and seas 2500 (m) approximately 4000 years
Lakes and reservoirs 0.25 (m) approximately 10 years
Swamps 0.007approximately (m) 1 to 10 years
River channels 0.003 (m) approximately 2 weeks
Soil moisture 0.132 (m) weeks to 1 year
Groundwater 120 (m) 2 weeks to 10 000 years
Ice caps and glaciers 60 (m) 10 to 1000 years
Atmospheric water 0.025(m) approximately 10 days
Biospheric water 0.001 (m) approximately 1 week