Aquifers Groundwater

Do you know where your last glass of water came from? If you drink tap water in the U.S. there is a 37% chance that it came from an aquifer, and if you drink bottled mineral water you can almost be sure it came from an aquifer. Freshwater supports life on Earth and 20% of this most important resource is stored in aquifers.

“Aquifer”  is a geologic term that defines those rocks or sediments underfoot that yield enough groundwater to be useful to people. For clarity, it should be noted that hydrogeologists (scientists who study aquifers) do not use the term “aquifer” interchangeably with “groundwater.” Aquifers contain groundwater; groundwater is simply any water that is under ground. Groundwater is indeed important, but let’s give a little glory to the aquifers!

Why, specifically, are aquifers important?  We have established that they hold one of our most precious resources, fresh water, but so do surface water bodies like lakes and reservoirs, right?

This is true, but when compared with surface water storage facilities like these examples, aquifers can offer three significant advantages: they are convenient, efficient and relatively safe. These factors make them an attractive water resource option for water managers and hydrogeologists around the world, which is why during the past century much effort has been made on improving aquifer protection and management.


Aquifers don’t take up any space that might otherwise be used for houses, highways or agricultural fields because they are underfoot. With the increasing population all over the world, real estate is in high demand and so this is an important advantage of aquifers. For example, if all the water in the Ogallala aquifer (one of the biggest aquifer systems in the U.S) was stored above ground, a reservoir the size of Lake Huron would be needed!


Aquifers lose significantly less water to evaporation than above ground storage methods because they are hidden from the sun. This is clearly more important in hot, arid areas than in cooler, temperate environments.

 An example technology that exploits this aspect of aquifers is called a “sand dam” builds up sands within a river bed to effectively create an aquifer for groundwater storage. This has fewer losses in a hot environment than a typical dam would, and have been used successfully all over Kenya, as well as in other arid lands around the world.


Aquifers are underground, so they are harder to pollute than rivers or lakes. Water in an aquifer is physically protected from contamination because any water entering the aquifer must first flow through layers of soil. Aquifers, especially shallow aquifers, are still under some risk of pollution, but that risk is much lower than that of an open lake or reservoir.

Soil is a natural filter, therefore any water entering aquifers is physically filtered before storage. If you take some muddy water and pour it into a bucket of sand with a hole in the bottom, the water that comes out the bottom will be almost clear!

Additionally, the ground contains many beneficial micro-organisms that “eat” or degrade contaminants, thus cleaning the water as it is flows through the soil. This process is particularly important when we consider fecal matter (or poo) as a contaminant. Fecal matter in your drinking water may seem disgusting, but for about a billion people in the developing world, this is the number one concern when it comes to water quality and water pollution.


It is only during the twentieth century that people really started to think about how aquifers are used. In places like the United States or Europe this has evolved into complex protection and management systems. Protection and management can not really be separated, but in a simplified way aquifer protection aims to keep groundwater clean (quality) and aquifer management aims to keep groundwater supply sustainable (quantity).

 Despite being relatively safe, as discussed above, aquifers MUST be protected from contamination because once they are polluted, they are generally much more difficult to clean up than surface water sources. Toxins can stick to the soil and sediment particles that make up the aquifer. These are deep underground, so they can be hard or impossible to clean off and thus continue to pollute the water flowing through the aquifer for years and years. Additionally, it takes more time, energy and thus money to clean up 1,000 liters of dirty groundwater from an aquifer than to clean the same amount of water from a lake, simply because it is underground.

To keep the world’s aquifers in good working order, they also need to be managed in a sustainable manner. Sustainable aquifer management generally entails making sure groundwater use (what comes out) is equal to aquifer recharge (what goes in), and includes monitoring water levels within the aquifer. Aquifer management is essentially synonymous with groundwater management. When more water is withdrawn from an aquifer than is coming in to it, like in the case of the Ogallala Aquifer, this is called water mining.

Aquifers offer several vital benefits over surface water storage, namely convience, efficiency and saftey, but does that mean we should start storing all freshwater underground? Of course not, every situation and every environment must find the best solution, specific to its water needs. The point is not that aquifers are the only option; the point is that they are a good option and a very important natural resource that must be protected from contamination and managed such that they remain a sustainable resource into the future.


U.S. Geological Survey:

Water Encyclopedia: