Guarani Aquifer facts for kids
The Guarani Aquifer is a huge underground water source. It's found deep below Argentina, Brazil, Paraguay, and Uruguay. It's the second biggest aquifer (underground water system) known on Earth and provides lots of fresh water.
This aquifer is named after the Guarani people. It covers a massive area of about 1,200,000 square kilometers (460,000 square miles). Imagine a water tank with a volume of around 40,000 cubic kilometers (9,600 cubic miles)! Its thickness varies, from about 50 meters (160 feet) to 800 meters (2,600 feet) deep. The deepest parts can be around 1,800 meters (5,900 feet) underground.
Experts believe the aquifer holds about 37,000 cubic kilometers (8,900 cubic miles) of water. It gets refilled by rain at a rate of about 166 cubic kilometers (40 cubic miles) each year. Some people say this huge underground lake could supply the world with fresh drinking water for 200 years. If the world's population stayed around 7 billion people, it could even last for 1,600 years, providing about 9 liters (2.4 gallons) of water per person each day.
Because fresh water is becoming scarce around the world, this important natural resource is becoming a topic of discussion among countries. People are talking about who should control it.
What is the Guarani Aquifer Made Of?
The Guarani Aquifer is mostly made of sandstone. This sandstone formed from ancient rivers (Piramboia Formation) and wind-blown sand (Botucatu Formation) during the Triassic and Jurassic periods, which were millions of years ago.
More than 90% of the aquifer's area is covered by a layer of basalt rock from the early Cretaceous period. This basalt layer acts like a protective lid. It doesn't let much water pass through, which helps keep the aquifer's water safe. This lid slows down how much rain can seep in and refill the aquifer. But it also protects the water from evaporating and from getting polluted by things on the surface.
In some places, pieces of the sandstone are exposed on the surface. These are called "outcrops." This is where rain can enter the aquifer, but it's also where pollution could potentially get in. Generally, the aquifer's sand is made of round quartz grains with very little clay. Most of the sand grains are quite small, about 0.125 to 0.250 millimeters (0.005 to 0.01 inches) across.
It's very important to study and monitor the aquifer to manage it well. The number of people living above the aquifer is growing, which means more water is being used. This also increases the risk of pollution. The countries that sit over the aquifer are Argentina, Brazil, Paraguay, and Uruguay. These are also the original four countries of Mercosur, a group that works together on trade and other issues.
How Does the Aquifer Get Water?
The amount of water that refills the aquifer depends on how much it rains. It's a bit complicated because many things affect how quickly rain seeps into the ground. The rate at which water infiltrates (soaks in) changes over time and from place to place.
Another big factor is evapotranspiration. This is when water evaporates from the soil and plants release water vapor into the air. The soil, plants, and atmosphere all work together in this process. In some areas, more water evaporates than flows away as runoff.
A study in Ribeirão Preto, Brazil, from 1994 to 2001, showed that farming activities using chemical products can risk contaminating the underground water.
Plants also play a role in how much water reaches the soil. For example, a study on Eucalyptus trees found that the trees intercepted about 11% of the rainfall, meaning that water didn't reach the ground directly.
See also
In Spanish: Acuífero Guaraní para niños
