Everything You Need to Know About Groundwater
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What is groundwater?
Groundwater is fresh water located underground in porous soil or fractures in rock formations. Collections of groundwater are called aquifers, and we draw from aquifers for drinking water and water for use in everything form irrigation to agriculture to manufacturing.
Groundwater pumping is when we pull water from the aquifer for our own use. When we pull more water than is naturally replenished, this is called groundwater mining because we have to drill deeper and deeper into the earth to get at the remaining water.
Groundwater is a very important source of water for civilizations worldwide, making up about 20% of the world's fresh water supply. Many cities have gotten used to mining groundwater to sustain its residents. However, as we overuse the resource, pull water faster than aquifers can naturally refill, and continue to pollute groundwater supplies, we're beginning to face a whole new set of serious problems with this vital resource.
This video from the International Groundwater Resources Assessment Center explains how groundwater is a
Why do groundwater levels matter?
The more we pump from aquifers, the farther the available water is from the surface of the earth. That means more energy has to go in to mining the water, and the costs begin to outweigh benefits, and our capabilities. When aquifers are mismanaged and too much water is extracted, it can mean the aquifer is no longer a viable source of water and a new source needs to be found. Depending on the available options, it can mean anything from a city moving to energy intensive and environmentally problematic solutions, such as desalination plants, to the community being unable to survive.
Overpumping groundwater leads to a loss of water beyond the water table. Diminished water levels means springs dry up, less water flows through rivers, pollution builds up even more, and the impacts trickle through the flora and fauna of an ecosystem.
Don't natural rainfall and water flow patterns fix everything?
Technically, yes. But it can take centuries, or even millennia, for groundwater levels to be replenished naturally. The
in Australia has water that is two million years old!
The replenishment of water in an aquifer is called recharge. The time it takes water to move from the recharge zone -- or where it enters the earth's surface -- and the aquifer is often far longer than humans are willing to wait to pump more water. That turns an aquifer into a finite, and unsustainable, resource for water.
Plus, more flow of water doesn't fix the problem of pollution. Everyday contaminants can sink into the groundwater supplies in aquifers, which means more energy has to be expended to purify the mined water and ecosystems become more vulnerable to those pollutants.
What's the worst that could happen if we continue groundwater pumping?
Simply put, we run out of that supply of drinking water as well as negatively impact surrounding ecosystems and riparian habitats. Most rivers, lakes and wetlands are dependent upon groundwater, so overdrawing aquifers often means a drop in the water table, making it harder for every living thing to get at water supplies.
Water management agencies are responsible for determining how much water is pumped from an aquifer. But a major problem is sometimes the agencies count water supplies twice, measuring both the amount that is in the aquifer as well as river water that can be drawn for human use. But that river water may be feeding the aquifer or vice versa. Inaccuracies in measuring supplies can have disastrous results.