A deciding moment On the downward path, at every 100 meters the soil’s temperature can rise in up to 3 degrees Celsius. The liquid permeates very slowly through the stone’s pores and takes decades to travel a few hundred meters. Opening up a thousand-meter hole down with steel drills requires almost a year. When a well is dug, water can come gushing out even without the aid of pumps. With current reserves found at the Alter do Chão Aquifer, one could fill 29.3 million soccer stadiums the size of Rio de Janeiro’s Maracanã.

Information disclosed in April this year, stands a good chance of drawing much attention from the scientific community, environmentalists and public agencies. Geologists Milton Matta, Francisco Matos de Abreu, civil engineer André Montenegro Duarte and economist Mário Ramos Ribeiro, researchers of the Federal University of Pará (UFPA) and also geologist Itabaraci Cavalcante, from the Federal University of Ceará (UFC), are all positive that the Alter do Chão Aquifer, that spreads throughout the states of Amazonas, Pará and Amapá in Brazil, holds the planet’s largest underground sweet water reservoir.

According to scientific findings, the Alter do Chão Aquifer surpasses in terms of volume of water the Guarani Aquifer, until now considered the largest in South America, located under Brazil, Paraguay, Argentina and Uruguay. Gurarani holds 45 thousand cubic kilometers of water, covers a surface of nearly 1.2 million square kilometers and 70.2% of its area is located in Brazil – its extension spreads under eight states: Mato Grosso, Mato Grosso do Sul, Goiás, Minas Gerais, São Paulo, Paraná, Santa Catarina and Rio Grande do Sul. Meanwhile, the aquifer located in the Amazon Rainforest covers three states, holds 86,400 cubic kilometers (approximately 86 quadrillion liters) and an average width of 575 meters. Since the available information up to this moment is only preliminary at best, it can be much thicker and have a greater volume of water than originally estimated.

To grasp just what these proportions found really mean, Milton Matta explains that with the amount of water in there, it would be possible to provide fresh water not only for the more than 193 million Brazilians but for the whole of humanity actually – and for about a hundred times. “Of course this is not feasible for geological reasons, but it is important that this aquifer’s capacity is plainly understood. We are saying that it is the largest in the world, now we only have to convince the scientific community of this. We’ve taken everyone by surprise. It’s something very new to everyone”, says he.

For Fernando Roberto de Oliveira, subterranean waters manager for the National Waters Agency (ANA), it is perfectly possible that the Alter do Chão Aquifer is in fact the largest on the planet. However he cautions that there is yet no evidence to confirm that claim with absolute certainty. “I feel it is a bit early to make such claims. The knowledge gained is yet in its preliminary stages. We will be able to say for sure when we have more detailed information”, said he.



According to Matta, part of the studies that resulted in new information on the Alter do Chão Aquifer were subsidized by resources from other projects developed by the researchers themselves – in other words, without the financial help of sponsors. The most recent data obtained on the subject come from a doctorate thesis in geosciences written by André Montenegro that, under the guidance of Francisco Mattos, investigated the potentialities of the waters in the Amazon. However, in order to obtain more information, there is no other way: one has to undertake further research.

That is why researchers have written a project under the temporary title of “Great Amazon Hydro-geological System: Groundwork for the Use and Protection of the Largest Underground Freshwater Reservoir in the World” for which they intend to this time, count on some external support.
“The Guarani is a smaller aquifer, yet it warranted 30 million dollars in support when all we’re asking for is five and at least four more years in which to collect data. We must determine with precision the total amount of water there as well as define a usage and protection model”, states Matta.

The team intends to obtain support from national and international entities – one of these will be the World Bank. In order to ease this quest for financial resources and avoid confusing this work with the activities of the touristic township Alter do Chão, near Santarém (PA), one of the strategies will be to change the aquifer’s name to “Great Amazon”. “The impact will be different on would-be financers”, concludes Matta.

The map below shows all the aquifers in the country. Matta says that he is the proof that little is known of the potential of aquifers in the region of the Brazilian portion of the Amazon. The area depicted in green shows the surmised size of the Alter do Chão Aquifer.


Usage and economic valuation

Mário Ramos Ribeiro upholds the economic valuation of the future “Great Amazon Aquifer”, an opinion also shared by Francisco Matos. “Hydric resources cannot continue to be treated as if they belonged to no one, infinite and always ready to be put to any use desired. In this context, society as a whole must discuss just how this would be done and the cost of extracting water from these aquifers. Water as an asset in itself is important to maintain the forest’s balance. The transference of humidity to Brazil’s south-center region brings rain and stirs an agribusiness of some 320 billion dollars (2008 data), the equivalent of 20% of Brazil’s GNP.  In face of such arguments – and others that we could list – it must be valued”, says Matos.

The waters of the Alter do Chão Aquifer already supply part of the cities of Manaus, in the Amazon Rainforest (data suggests 40%) and of Santarém, in Pará. Parts of the material made available to the reporting team by one of the researchers, speaks of the capacity to “afford enough water for the industry and farming activities”. Scientists are then betting on the many uses of this aquifer.

In order to ensure there is no overexploiting, a usage and protection plan will be devised to guide the use of the aquifer. “We will say which areas can or cannot be touched”, explains Matta. “It will be indispensible to have an enforcing power for the socially sustainable use of this resource”, concludes Francisco Matos.

The announcement and the substantiation that under the soils of the Amazon there’s the largest quantity of sweet water in the world can make the eyes of many pop out with this groundbreaking news. Especially because of all the water in the world, less than 1% would be actually available for human consumption. Another important datum is that all the water that can be seen in the Amazon Rainforest (derived from rivers, rainfall and lakes) represent only 16% on the total amount in existence – 84% remains underground.


Aquifers x surface water

According to scientists, there are some advantages in employing aquifers to feed cities against the use of surface water. “The water is clean and doesn’t require treatment. The construction of wells has a lesser impact on the environment, it is cheap – a 50 meter deep one in Belém costs 12 thousand reais and can last up to 20 years”, claims Matta.

Other two advantages would be the fact that underground waters do not take up space on the surface and suffer less influence during climate variations, as explains the book Guarani Aquifer: The True Integration of Mercosul Countries, authored by biologists Nadia Rita Boscardin Borghetti and José Roberto Borghetti and by geologist Ernani Francisco da Rosa Filho.

Although they are located underground at small or great depths, water from aquifers can be contaminated in case there are any trash dumps, cesspits, cemeteries or major farmlands close by. “In another comparison with surface waters, if an aquifer is more difficult to contaminate, it is also much more complicated to decontaminate. In the case of the Alter do Chão Aquifer, we already know of ongoing contaminating processes that, if not dealt with swiftly, may reach underground waters”, says Matta. When in doubt, the best practice is to protect the area of this aquifer in the best manner possible. After all, in it can lie the largest quantity of freshwater (and drinking water) on Earth.


Karina Miotto is a journalist graduated from PUC-SP. As a free-lancer for the Abril Group, she loves to travel and ended up in the Amazon Rainforest where she began working for Greenpeace and writing for Terra da Gente and National Geographic magazines. She is the author of the Eco-Repórter-Eco blog and a correspondent of ((o)) eco Amazonia.