In Sao Paulo, South America's largest city and the continent's industrial centre, the price of industrialization can be seen in the murky, contaminated waters of the Tiete and Pinheiros Rivers that cross the sprawling megalopolis.

What is not so clear is the effect that these rivers -- choked with sewage and industrial waste -- have on the groundwater supply, to which they are connected by a shallow aquifer.

Treated water from the Upper Tiete basin and a reservoir fed with water from the Pinheiros River supplies most of Sao Paulo's 17 million residents. The remainder of the 'Paulistanos' rely on groundwater, often drawn from badly constructed wells. In addition to many other sources of contamination, the groundwater is threatened by pollution from streams.

Tainted water and water shortages are familiar realities for millions of Paulistanos. Late in 1993, for instance, about 300 residents of Pirituba in northern Sao Paulo blocked a highway for six hours to protest a water shortage. About 1,000 families were without water for three days, in temperatures above 30 C. "We cannot live in this heat without water," says one woman. Many desperate people used water from contaminated wells. "Now 20 people have hepatitis from drinking bad water," said one angry community leader.

Particularly for the three million urban poor living in the belt of favelas (shantytowns) ringing Sao Paulo, the shortages and degradation of the water supply are serious problems. Most of these people, former rural dwellers from Brazil's poor northeast, still find themselves living below the poverty line. Their new neighbourhoods are without basic urban services, creating grave difficulties in waste disposal and water supply.

The urban poor can expect little assistance from government sources: the ongoing political and economic crisis in Brazil means there are no resources to carry out research on the gravity of water supply problems and contamination of valuable groundwater. But an IDRC-supported project brings some possibilities for improvements.

Part of the Latin American network of IDRC-supported projects in urban hydrology, the project addresses groundwater contamination and water shortages, among other issues. "We want to determine the correlation between the surface water and groundwater," says Dr. Nelson Ellert, project leader and associate professor at CEPAS (Centro de Estudos e Pesquisas de Aguas Subterraneas), one of the few South American institutes that conducts groundwater research. The centre is located at the Institute of Geosciences, University of Sao Paulo (USP). "Knowing that the rivers are so polluted, and that they mostly run on permeable layers, we want to determine whether or not there is a problem, and if so, detect where it is, and its magnitude."

The current research is the second phase of a recent collaborative project between CEPAS and the Institute for Groundwater Research at the University of Waterloo (IGR-UW) in Canada.

KNOWLEDGE CENTRE

Ellert says IGR-UW's role was greater in the first phase, but is currently limited mainly to transfer of technology. "The idea is for them to help us to create a centre of knowledge from which we can irradiate knowledge to the surrounding area. It is easier and less expensive for me to go to Argentina or Bolivia than for a Canadian expert," Ellert says.

The second phase will use the new methods developed to identify the sources, types and magnitude of contamination near the Tiete, Pinheiros and Tamanduati Rivers, and develop new analytical methods for groundwater study and environmental assessment in subtropical humid urban environments.

The project's investigation wells are located at three contaminated or threatened sites in Sao Paulo: at the university itself, which is located beside the Pinheiros River in central Sao Paulo; near the international airport at an ecological park beside the Tiete River, known to be contaminated by a landfill site; and the Tamanduati River, which carries heavy metals in effluent from the city's petro-chemical industries to the two other rivers.

Ellert says the project already has some tangible results and byproducts. The university site is a good example. "Before, the water company had been pressuring us to reduce our consumption of water at the university. We have constructed seven deep wells for our research and, as a result, are now supplying 70% of our own needs," says Ellert.

And preliminary study results show that pollution of groundwater from the Tiete, Pinheiros and Tamanduati rivers may not be as generalized as feared. A thick layer of clay along the riverbeds prevents seepage into the groundwater. At present, the water table is higher than the rivers' waters, and therefore recharge to the aquifer does not occur; however, excessive pumping may lower the water table below the river level, inducing seepage of contaminated water into the aquifer.

But pollution is already coming from other sources. "In many places, we have found that the construction and maintenance of wells is the main reason for the pollution of deep wells," says Ellert. For instance, some wells are constructed with their heads below the ground's surface, so when it rains, the water runs inside. "This is like introducing your vein to very dangerous poison," Ellert says.

FUTURE PROBLEMS

Mathematical models developed at the University of Waterloo using information gathered about groundwater behaviour during the project have alerted researchers to future problems. In areas with many deep wells, the water table is sinking at a rate of 3 to 4.4 metres per year. "So these groundwater sources get depleted through the use of deep wells, the water table sinks, and this means there is a possibility of very polluted water being introduced into the groundwater in future," says Ellert. "It seems that in 30 years we will have some problems with the water flowing from the river into the wells, here at the university and at other sites."

The project also had a larger spinoff: the city water officials contracted CEPAS to do a study of groundwater resource potential in the entire Sao Paulo area. CEPAS found that Sao Paulo has much potential for more deep wells, which range between 60-350 metres in depth. These wells would be of particular benefit to poor residents in unserviced areas as well as hospitals, hotels, schools and industries, all of which face water shortages.

Study results will allow the water authorities to make better water management plans for the future. "If there is a critical area where there is a poor water supply, and we have already detected high potential for groundwater, for instance, we can suggest that the water company drill wells there," says Ellert.

Findings from the project and spinoff study will also be relevant for other cities in Brazil with problems similar to Sao Paulo's, and throughout Latin America and other subtropical regions where there is little information about groundwater resources and their vulnerability to contamination.

But Ellert says that Sao Paulo's urban poor will be the most immediate beneficiaries of the application of knowledge gathered by this project. "As the city grows continually, areas surrounding Sao Paulo have become crazy. Urbanization has become clandestine -- people occupy a piece of land and start to build there and create a problem because there are no services. Then the municipality arrives and has to reduce the problem by giving electricity, sewage and water," says Ellert. "But with the kind of information we are developing, the water authorities can make local studies and produce water for these areas."

For more information, contact:

Dr. Nelson Ellert
CEPAS,
Instituto de Geociencias Universidade de Sao Paulo
Tel: 11 818-4206 or 818-4144
Fax: 11 210-4958

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