The Guarani Aquifer is Contaminated by Agritoxins
The Guarani aquifer, the source of 100% of the water serving Riberao Preto, a city in the northeast of Sao Paulo state located 313km from the state capital, is threatened by herbicides.
This conclusion comes from a study done with data from the Riberao Preto Department of Water and Sewage (DAERP) in partnership with a group of researchers. It found two samples of water from an artesian well in eastern Riberao Preto with traces of diuron and hexazinone, components of the agrochemical protection of sugar cane.
Throughout the study one hundred DAERP wells were investigated with samples taken every 15 days. The concentrations of the product found at the site were 0.2 picograms per liter - or two trillionths of a gram. This measurement is far below the levels considered dangerous for human consumption in Europe (0.5 milligrams or 5 millionths of a gram per liter). However, the results of the study still worry the researchers, who see even larger contamination as a possibility.
In Brazil, there are no official substance levels deemed unsafe. Still, the presence of herbicide in the eastern zone - where the aquifer isn’t as deep - sends up a warning flare for specialists. According to Cristina Paschoalato, a professor at UNAERP who coordinated the study, the results should serve as a warning. “It doesn’t mean that the water is contaminated, but it’s necessary to avoid the application of herbicides and pesticides in areas where the aquifer replenishes itself,” she says.
Monitoring also found signs of the same products in the Pardo River, which is considered an alternative water source for the region in the long run. “This shows that, if the situation isn’t resolved and adequate preventive measures aren’t taken, Riberao Preto could suffer severely since using the river as a secondary water supply could be impossible if it too is contaminated.”
The Guarani aquifer system, which is part of the Sedimentary Geological Basin of Parana, covers an area of 1.2 million km², 839,800 of which are in Brazil, 225,500 in Argentina, 71,700 in Paraguay, and 58,500 in Uruguay. With an estimated reserve of 46,000 km² of water, about thirty million people live in the basin, 600,000 of them being in Riberao Preto.
The water from the Guarani aquifer system is of very high quality in various locations, mainly in outcroppings of the aquifer and surrounding areas, where the possibility of salts and other chemical composites seeping into the water is remote. This is the case in Riberao Preto, nationally renowned for the quality of its water.
For the chemical engineer Paulo Finotti, president of the Society for the Regional Defense of the Environment (SODERMA), Riberao Preto runs the risk of making the use of water from its natural aquifer impossible. “The eastern zone of the city has sugar cane plantations in areas covered with lakes filled with aquifer water. It’s a process that takes many years, but these petrochemicals will inevitably reach the aquifer, which could impede use of the aquifer if nothing is done,” he explained.
For Marcos Massoli, a specialist that brought together the local group of studies on the aquifer, the construction of houses and gated communities in the city, begun through a bill by former councilman Silvio Martins (PMDB) in 2005, is already extremely harmful to the health of the aquifer. “It damages the impermeability that keeps the aquifer full,” he said.
Another problem that could put the water supply of Riberao Preto at risk in the medium term is the excessive extraction of water from subterranean sources. If the current pace of extraction is maintained, the use of water from the Guarani aquifer could become infeasible in the next 50 years in Riberao Preto.
The alternative, aside from reducing water capture, could be to invest in structures that collect water from streams and rivers, in addition to being water of a lower quality, significant major investments would need to be made to make such water potable. This perspective was already considered by a study called Project Guarani, which involved four countries with territory above the subterranean reserve of the aquifer. The final recommendations of the report were released at the end of 2010.
The mapping from Project Guarani showed that the velocity of the flux of water absorbed by the reserve is slower than was supposed. According to the specialists, the city extracted 4% more than it should have from the aquifer. The average daily water consumption in Riberao Preto is 400 liters per person, well above the 250 liters of the national average. The city removes 16 thousand liters of water from the aquifer hourly. It should be noted that the largest portion of fresh water in the world, somewhere around 70%, is in the form of ice near the poles and in mountainous regions.
The other 29% of global freshwater is in underground sources. The world’s lakes and rivers, when put together, supply less than 1% of the world’s fresh water. However, in the case of potable water, nearly 98% is found underground, and the Guarani Aquifer is the largest of all sources. The alternative way to preserve these resources is to invest in reforestation to guarantee that the aquifer can recharge, says the secretary general of the project, Luiz Amore.
translated by Rob Call