Most of the freshwater you consume comes from vast resources hidden deep underground. People in rural areas actually own private wells and are quite familiar with the process.
However, the majority of people don’t quite grasp the phenomenon behind groundwater and how it goes from deep in the earth’s layers to a glass of water.
Keep reading to learn about the miracle of groundwater that nourishes life on our planet.
Well water comes from large reservoirs of freshwater under the ground called aquifers. Saying that aquifers are the lifeline of the human species is not an understatement. Nearly 96% of all freshwater consumed by people comes from here.
Let’s explore this wonder of nature in detail.
An aquifer is made of small rocks, gravel, and unconsolidated sediment that holds water in the tiny spaces between the particles.
Think of it like a sponge that holds water in the tiny spaces between the foam. The aquifer works the same way, holding water in porous spaces in underground rocks. Water flows through these cracks and crevices. It’s not a river or water channel under the earth, contrary to popular belief.
Aquifers can occur from 15 ft to 30,000 ft below the surface.
Saturated ground vs. unsaturated ground
Here comes the tricky part. Groundwater is actually present in two zones: unsaturated and saturated.
The unsaturated ground is present just below the land surface. It holds water and air in tiny open spaces between the ground particles. These particles could be sand, sediment, gravel, or tiny rocks. Water isn’t a major part of the unsaturated zone.
As the ground gets deeper, it becomes more permeable, and small fractures and spaces between rocks hold a large amount of water. This is known as the saturated zone, or an aquifer, which is the main source of groundwater.
The water table is nothing but the line that separates an unsaturated zone from a saturated zone. When the well is dug, the moment it hits the point where water starts coming out of the ground is called the water table. Primitive dug wells have the depth equal to that of the water table.
Courtesy of USGS
Where does the water come from?
If you remember the water cycle from elementary school, then you already know the answer. Water from lakes, rivers and oceans evaporates, transforms into clouds, and then rains down in a perpetual cycle.
Surface water that doesn’t end up in bodies of water gets absorbed by the ground. Water flows through the porous sand and gravel, where soil also acts as a natural filter and removes some of the impurities present in the water. The process continues until water meets the underlying aquifer.
How Do Wells Get Water From Underground?
Wells are used to access groundwater. At its simplest, a well is a hole in the ground that is deep enough to tap into an underground aquifer that draws water by some kind of mechanical system.
In earlier days, it was a pulley-and-rope system, but now modern water wells use submersible pumps. Drilled wells go much deeper, thanks to high-tech rotary drilling machines and jet pumps! So, you don’t have to worry about fetching water like some cowboy in an old western movie.
There is no well opening in the latest water wells, which prevents contamination.
You can find more about how the private water wells work here. Water extracted from below ground is used for drinking, irrigation, food production, and much more.
Types of Aquifers
Aquifers have different types, and you need to know this to truly understand what’s happening under your feet. These underground water bodies have two types: confined and unconfined aquifers.
An unconfined aquifer is the common groundwater source that shallow water wells like “dug wells” and “borewells” use to draw water from. They are often called “the water table,” which is also their upper boundary. They are not confined by any underground layer and are easiest to access. However, they’re more prone to contamination because of surface pollutants.
They are formed at higher rates and are affected by rainfall. In droughts, unconfined aquifers are at risk of drying up and the water table may fall farther below the surface.
As is obvious from the name, these aquifers are confined by a layer of impermeable bedrock and clay. In other words, water stored in the confined aquifer can’t move past such a layer.
These layers are also called “low hydraulic conductivity units,” a fancy term for rocks holding the least amount of water.
Since the confined aquifers are bound by bedrock, the water present here doesn’t come directly from above the ground like in the case of an unconfined aquifer, which is replenished by rainwater. Instead, the water comes from a spring or lake present at the higher grounds.
Modern drilled wells tap into confined aquifers, which offer a more consistent supply of pure water.
Sometimes this confinement raises the pressure in the aquifer. If you drill a well in such an aquifer, water will start gushing out of the hole due to pressure differences. Such wells are also called artesian wells. There is no need for a water pump.
Courtesy of USGS
Other Sources of Groundwater
It’s true that the majority of the freshwater we use comes from aquifers, but there are other less desirable groundwater sources, such as aquitard, aquiclude, and aquifuge.
These layers are partially permeable and hence can’t store or permit water flow as aquifers do, making them unsuitable for water extraction.
Myths About Groundwater
There are many misconceptions about underground water, and even homeowners with private wells seem to lack a basic understanding of some of the finer points.
Myth 1: Groundwater flows like rivers and lakes
If you think that groundwater is some sort of vast underground river flowing under the earth’s surface (like in the picture below), then prepare to have your bubble burst—it’s not true.
An aquifer is a body of permeable rock, sand, and gravel that holds water in the tiny pockets and fractures in between them.
Echo River in Mammoth Cave, Kentucky
Myth 2: Groundwater is the purest
There is no such thing as the purest of all water, and one should be cautious of consuming anything before proper testing. Groundwater is healthy to drink, but do consult local governing agencies first. Studies show that kids are most affected by contaminants present in groundwater.
Myth 3: Groundwater is declining
Unfortunately, there might be some truth to this statement, though it varies by location. Groundwater is the largest natural resource that humans consume, but the mammoth extraction of it is causing a decline in water underground. Mindful usage and sustainable policies can help replenish the groundwater resources at a much faster rate.
Do Wells Run Out of Water?
Yes, wells do run out of water. This usually happens in shallow wells where drought and other factors may cause wells to dry. It happens when the water table falls below a certain level. In such cases, the depth of the well needs to be increased.
If rain falls periodically and consumption is regulated, then there is no need to worry. Modern wells are drilled deep enough, so they hardly get dried.
How fast does well water replenish?
Groundwater is sometimes hundreds or even thousands of years old. According to one estimation, the recharge rate is between 0.3 and 15 inches per year.
The replenishment of well water is a continuous process. There is no right answer for this because the rate at which well water replenishes varies from location to location.
How to Find Groundwater Under Earth’s Surface?
Where to dig for groundwater is the most common query by homeowners in need of a well. There are many false beliefs and opinions regarding this, mostly based on superstitions and personal anecdotes. Allow me to challenge those misconceptions.
Hydrogeology to the rescue . . .
Hydrogeology is the study of earth layers and groundwater. With the use of modern technology and drilling machines, hydrogeologists can locate suitable aquifers for drinking water and irrigation. They also examine soil samples from nearby wells and look for contaminants.
Moreover, all local well contractors have expert hydrogeologists on their teams to pinpoint the highest-yielding locations.
Charging money for finding water using metallic rods and sticks is quite common in rural locations, and it’s called water dowsing. They claim to have some sort of reaction to energy fields generated by ground water.
However, it’s all hocus-pocus and has nothing to do with actual science. But you might wonder why these guys succeed in finding an aquifer? It’s because underground aquifers are present everywhere. So, chances of striking the water table are quite high.
Groundwater Contamination—Is it Serious?
Groundwater is supposed to be pure, but people have polluted it with rapid industrialization and unfathomable waste dumping in landfills. It’s a growing concern that needs attention before the damage is irreversible. Here are some of the most common contaminants that affect groundwater quality:
Pesticides and fertilizers
These may be necessary for effective crop harvesting, but the toxic chemicals in them move through the soil and end up in an aquifer. Adopting organic agriculture techniques is one way that farmers can help prevent the contamination of groundwater.
Industrial waste from mining and motor oil can also seep through the ground and affect water quality.
Road salt prevents ice formation on roads in winters, but it’s highly toxic and can pollute underground water sources.
E. coli bacteria is most commonly found in fecal matter and can sneak its way into underground water. It usually happens due to damaged sewer lines or septic tanks.
Nitrate contamination is perhaps the most lethal of all contaminations. It can be dangerous for babies and can cause cyanosis. It’s a naturally occurring contaminant but can also be caused by unregulated landfills and fertilization of the soil.
Arsenic is a naturally occuring element in rock and is sometimes found in deep private wells. Unfortunately, it is harmful to humans and can even lead to cancer. Studies show that industrial waste containing arsenic is the leading cause of such contamination in groundwater.
Lead isn’t present in the groundwater but gets dissolved by corroded pipe carrying water and other well components.
Studies show that children who drink private well water have higher lead in their blood than those drinking city water. This is highly concerning because lead can damage the brain and cognitive ability of a child.
Is Well Water Safe to Drink?
Yes, it’s safe to drink, but prior testing of a sample is necessary. In extreme cases, water treatment and a filtration process are required to avoid any health hazards. Typically, kids are the most sensitive to contaminants in well water. The EPA suggests private well owners have yearly maintenance and water testing of their wells.
How Deep Should a Well Be for Drinking Water?
The deeper the well is, the more it’s free of surface contaminants. Normally, a depth of 100 feet is enough to get drinking water from an aquifer. However, experts still recommend installing filtration plants at home.
To Sum Up
Groundwater is the most consumed natural resource on the planet, so much so that the survival of humankind depends on it. Knowing about its origin and how it works beneath the earth’s surface will help you consume water more responsibly. It’ll also help you keep your private well healthy and running.
Like any other natural source, it has limits, and regulating its usage will ensure a lifetime of fresh water supply without any interruption.