Climate change could aggravate hydric crisis in urban centers

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Agência FAPESP* –By Karina Toledo
Agência FAPESP – Extreme climate events, such as extended periods of drought, powerful storms and intense cold or heat waves, are expected to become more frequent as the planet’s temperature rises, which may impact the availability of hydric resources in Brazil’s large urban centers.
The assessment was made by researcher Humberto Ribeiro da Rocha of the Institute of Astronomy, Geophysics and Atmospheric Sciences at the University of São Paulo (IAG/USP) during his lecture at the third meeting of the 2014 Biota-FAPESP Conference Cycle, held in São Paulo on April 24, 2014.
According to Rocha, the supply of water in Brazil is, on average, much greater than demand. With a flow of 5,660 cubic kilometers per year (km³/year), Brazilian rivers hold nearly 12% of the world’s available water. The Brazilian population consumes approximately 74 km³/year, less than 2% of the quantity supplied. However, because hydric resources are unequally distributed, some regions are experiencing problems with water supply.
“Nearly 80% of the hydric resources are concentrated in the Amazon Basin, while there are regions with very little, such as the northeastern sertão, where survival is only possible thanks to the large dams,” he stated.
Although the lack of rain is the main cause of hydric scarcity in the Northeast and in northern Minas Gerais, the researcher added that in large urban centers such as São Paulo, Rio de Janeiro, Belo Horizonte, Porto Alegre and Goiânia, the problem is population density.
“There are many problems involved in strengthening the supply systems that have to accompany population growth and the demands of industry and agriculture. Everything is already working at capacity, and when there is an extreme climate event such as the drought in São Paulo that occurred this past summer, there is a crisis with the supply,” he said.
Although, on a global scale, an estimated 10% increase is expected in the volume of rainfall along with global warming, primarily as a result of increased ocean evaporation, certain regions may suffer from drought.
“The redistribution of ocean heat could form hot and cold pools, which distort the rainfall patterns on the continent. It may begin to rain more in certain regions and less in others,” Rocha explained.
According to the researcher, the mini-drought (high temperatures and scarcity of rainfall) that affected São Paulo in early 2014 was caused by the formation of a hot water pool in the tropical region of the Atlantic. “For some reason, the cold fronts that usually cool the ocean water never got here. The pool got hotter and hotter and prevented new cold fronts from moving in. Ocean temperature is a factor that has a major impact on the continent’s rainfall pattern,” he said.

<p><b>By Karina Toledo</b></p>
<p><b>Agência FAPESP</b> – Extreme climate events, such as extended periods of drought, powerful storms and intense cold or heat waves, are expected to become more frequent as the planet’s temperature rises, which may impact the availability of hydric resources in Brazil’s large urban centers.</p>
<p>The assessment was made by researcher Humberto Ribeiro da Rocha of the Institute of Astronomy, Geophysics and Atmospheric Sciences at the University of São Paulo (IAG/USP) during his lecture at the third meeting of the 2014 Biota-FAPESP Conference Cycle, held in São Paulo on April 24, 2014.</p>
<p>According to Rocha, the supply of water in Brazil is, on average, much greater than demand. With a flow of 5,660 cubic kilometers per year (km³/year), Brazilian rivers hold nearly 12% of the world’s available water. The Brazilian population consumes approximately 74 km³/year, less than 2% of the quantity supplied. However, because hydric resources are unequally distributed, some regions are experiencing problems with water supply.</p>
<p>“Nearly 80% of the hydric resources are concentrated in the Amazon Basin, while there are regions with very little, such as the northeastern sertão, where survival is only possible thanks to the large dams,” he stated.</p>
<p>Although the lack of rain is the main cause of hydric scarcity in the Northeast and in northern Minas Gerais, the researcher added that in large urban centers such as São Paulo, Rio de Janeiro, Belo Horizonte, Porto Alegre and Goiânia, the problem is population density.</p>
<p>“There are many problems involved in strengthening the supply systems that have to accompany population growth and the demands of industry and agriculture. Everything is already working at capacity, and when there is an extreme climate event such as the drought in São Paulo that occurred this past summer, there is a crisis with the supply,” he said.</p>
<p>Although, on a global scale, an estimated 10% increase is expected in the volume of rainfall along with global warming, primarily as a result of increased ocean evaporation, certain regions may suffer from drought.</p>
<p>“The redistribution of ocean heat could form hot and cold pools, which distort the rainfall patterns on the continent. It may begin to rain more in certain regions and less in others,” Rocha explained.</p>
<p>According to the researcher, the mini-drought (high temperatures and scarcity of rainfall) that affected São Paulo in early 2014 was caused by the formation of a hot water pool in the tropical region of the Atlantic. “For some reason, the cold fronts that usually cool the ocean water never got here. The pool got hotter and hotter and prevented new cold fronts from moving in. Ocean temperature is a factor that has a major impact on the continent’s rainfall pattern,” he said.</p>
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