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A Treasure Underfoot
By María Laura Mazza

Little is known about the huge Guaraní Aquifer, an underground reservoir of freshwater for the countries of Mercosur (Argentina, Brazil, Paraguay and Uruguay). Experts are preparing long-term plans to preserve it.

MONTEVIDEO, (Tierramérica).- The Guaraní Aquifer, perhaps the largest underground freshwater reservoir in the world, under the territories of Argentina, Brazil, Paraguay and Uruguay, could suffer irreversible damage from contamination and unregulated exploitation, warn experts.

The uncontrolled increase in volumes of water extracted from the aquifer and the contamination from agro-chemicals and urban and industrial waste are some of the factors that threaten the potable water supplies of millions of people, and even the hot springs tourism industry and the future of thermal-powered electrical plants.

To prevent potential disaster, the four members of Mercosur (Southern Common Market) in March launched the Project for the Environmental Protection and Sustainable Management of the Guaraní Aquifer System, with the support of the Global Environment Facility (GEF), the World Bank and the Organization of American States.

The experts involved in the project have until March 2007 to draw up the plan to be presented to the four governments for shared management of the vital underground resource.

The goal is to develop an appropriate legal framework and to promote public participation so that society contributes to preserving the aquifer.

The total cost of the project is 26.7 million dollars, with GEF providing 13.4 million of that sum, the four governments another 11.9 million, with the rest coming from international institutions and cooperation agreements.

The project, largely preventive in nature, is in the information gathering stages. All of the sources consulted agree that relatively little is known about the reservoir. For example, it is not known where western border of the aquifer lies.

The initial task is to collect data to define the aquifer's characteristics, identify its inflow and outflow locations and water dynamics, understand its hydrogeology, and diagnose contamination levels.

An aquifer is a geological formation that stores water underground and allows it to move from place to place. The Guaraní is really a system of aquifers stretching over 1.2 million square km, of which 840,000 are in Brazil, 225,000 in Argentina, 71,700 in Paraguay and 58,500 in Uruguay (see infograph).

It holds an estimated 45,000 cubic kilometers of water, but the usable volume is just 40 to 80 cubic km per year. In much of the aquifer, water is under pressure, which saves in pumping costs. And in the central zone there are hot springs.

Some concrete problems are already known, the program's secretary-general, Brazil's Luiz Amore, told Tierramérica.

The mere presence of pesticides and fertilizers in areas where the aquifer is recharged with rainwater constitutes a threat to the entire reservoir. Farming and livestock activities may also compact the soil and impede water filtration, said Amore.

In the border cities of Rivera and Santana do Livramento, on each side of the Uruguay-Brazil border, there is a high risk of contamination due to the proximity of small industry, gas stations, cemeteries and garbage dumps to an aquifer recharge area, he said.

In the area along the Uruguay River -- at Salto, on the Uruguayan side, and Concordia, on the Argentine side -- the principal objective is to establish the degree of sustainable use of thermal waters from the aquifer.

Salto-Concordia is the site of greatest hydrothermal exploitation of the aquifer through several deep wells. The danger is that the water would lose the pressure necessary for pumping it, says Danilo Antón, an Uruguayan geographer, and the one who proposed the name Guaraní for an aquifer that covers nearly the entire territory of the indigenous civilization of that name prior to the arrival of the Europeans.

One of the project's proposals is to study the geothermal potential of the aquifer as a source of clean energy.

Another threat to the aquifer are the northern Uruguayan plantations of eucalyptus and pine trees, which due to their rapid growth capture a great deal of precipitation, preventing it from filtering into the underground reservoir, Antón told Tierramérica.

Deforestation also poses a problem. It increases water filtration too much, creating greater vulnerability to erosion and contaminants. This could be occurring in the aquifer recharge area in Paraguay, according to Elena Benítez, coordinator of the project in that country.

And not least of the worries is exploitation of the aquifer for human consumption. Demographic pressure, economic growth and surface water contamination have led to rising demands on subterranean water, which is purer and therefore much cheaper to process for consumption.

The country that most exploits the Guaraní aquifer is Brazil. It is used to partially or totally meet the needs of more than 300 cities, including Sao Paulo, home to 18 million people.

Amore noted that it could be overexploitation in Riberao Preto, in Sao Paulo state, that has caused a 60-meter drop in the aquifer water level, which has an average depth of 250 meters.

A sustainable future for the Guaraní Aquifer and for other water resources in the Mercosur region requires greater regulation and standardization of laws, agreed the sources consulted by Tierramérica.

* María Laura Mazza is a Tierramérica contributor.