By Mario Osava
Two thirds of the Brazilian electrical energy comes from dammed rivers, whose flows have dropped to alarming levels.
The crisis reactivated concerns about climate change, the need to reforest river banks and new theses on the electrical system.
"We must diversify sources and reduce dependence on hydroelectric and thermoelectric plants powered by fossil fuels, to face increasingly frequent extreme weather events," Delcio Rodrigues, vice president of the non-governmental Vitae Civilis Institute, told Tierramérica.
The hydraulic source provided almost 90 percent of electricity generation until the 2001 "blackout", which forced rationing for eight months.
Since then, thermoelectricity, more expensive and polluting, has advanced to compensate for water instabilities.
Currently, thermal power plants, operated mainly with oil, reach 28 percent of the national generation capacity, against 66.3 percent of hydroelectric plants.
The other sources remain marginal. Supporters of hydropower advocate a return to large reservoirs, with the ability to withstand prolonged droughts.
The insecurity of supply is due, they argue, to run-of-the-river power plants with short water retention capacity, imposed for environmental reasons.
But "the largest reservoir of water is the forest," contrasts Rodrigues, to explain that without deforestation, which affects all basins, there would be more water retained in the ground, sustaining the river flow.
"Forests constitute the source, middle and end of the flow, because they produce continental atmospheric humidity, the infiltration of rain into the soil accumulating water and the protection of reservoirs", explained Antonio Donato Nobre, researcher on climate issues. "The Amazon already has 47 percent of its forest impacted, adding the total felling that reaches almost 20 percent and degradation," said Nobre, from the Amazon Research Institute and its counterpart in Space Studies.
That favors fires. "Before they did not penetrate into humid areas of forests that are still green, now they do, they move into the forest, burning immense extensions," he exemplified in dialogue with Tierramérica. “Amazonian trees have no tolerance to fire, unlike those (of the Cerrado ecoregion), adapted to periodic fires. Amazon forests take centuries to rebuild, "he said.
The scientist fears that deforestation is affecting the South American climate, even reducing rainfall in the Brazilian southeast, the most populated region that generates the most hydroelectricity in the country.
"Studies are lacking to quantify the moisture transported to different basins," to specify the climatic relationship between the Amazon and other regions, he acknowledged.
But in the eastern Amazon region, where destruction and forest degradation are concentrated, climatic changes are already visible, such as the decrease in rainfall and the extension of the dry season, he stressed.
In the Xingú River basin, this could be the year with the lowest rainfall in 14 years of measurement in Canarana, a municipality of its head, according to the Socio-Environmental Institute (ISA), which develops a sustainability program for indigenous and riverine peoples of the basin .
If this is consolidated as a trend, it will affect the Belo Monte hydroelectric plant, under construction 1,200 kilometers downstream, which will have a generation capacity of 11,233 megawatts, which will make it the third largest in the world, when fully operational, at as of 2019.
But its effective generation may fall 38 percent by 2050, in relation to what is expected, if deforestation continues at the current rate, according to a study by eight Brazilian and American researchers, published in 2013 by the journal of the National Academy of Sciences of the States. United.
That year, deforestation in the Xingú basin already reached 21.3 percent of its territory, the ISA estimated. Other large hydroelectric plants are being built in the Amazon that may also suffer losses.
In the Madeira River, torrential flows from its tributaries in Bolivia and Peru submerged the area where the Jirau and Santo Antônio plants are located in 2014, affecting their recently started operations.
The trend in the southern part of the Amazon basin is for “more intense events, with stronger low water and floods”, such as the severe droughts of 2005 and 2010 and abnormal floods in 2009 and 2012, said Naziano Filizola, a hydrologist at the Federal University of Amazonas.
“In addition to altering the flow, deforestation is linked to agricultural occupation that dumps pesticides into the river, as occurs in the upper Xingu.
The water loses quality, according to the indigenous people, ”he told Tierramérica. The same energy project reinforces that process, by attracting migrant workers, increasing the local population without offering them adequate conditions, he said.Anyway, the most intense energy impact due to insufficient rainfall occurs, for now, in the Central Planalto region, where the Cerrado, a savanna biome and the second most extensive in Brazil, behind the Amazon. The main basins with hydroelectric uses are born there. Related Posts
• Brazil goes from the droughts of the Northeast to the thirst of São Paulo
• Taking care of water is an energy duty in Brazil
• The Xingu River, between electricity and diversity
• A curse haunts Amazonian hydroelectric plants The one on the Paraná river, which runs south and concentrates the largest generating capacity in the country, receives half of its waters from the Cerrado, which rises to 60 percent in the Tocantins river basin, that flows to the north of the Amazon, said Jorge Werneck, a researcher at the Brazilian Agricultural Research Company (Embrapa).
These two rivers drive the two largest current Brazilian hydroelectric plants: Itaipú, shared with Paraguay, and Tucuruí.
Both are among the five largest in the world.
Another example is the São Francisco River, the main electricity source in the Northeast region, with 94 percent of its water flow coming from the Cerrado.
In his field of observation, the surroundings of Brasilia, where several rivers are born, Werneck, a hydrology specialist from Embrapa Cerrados, noticed a general trend towards the prolongation of the dry season. "But there is a lack of data and studies to verify the relationship between Amazon deforestation and changes in the rainfall regime of the Central-West and Southeast regions of Brazil," he added. In 2014, there was a drought in these regions, which comprise most of the Cerrado, but “there was no shortage of humidity in the Amazon and in fact it rained a lot in the states of Rondônia and Acre,” bordering Bolivia and Peru and victims of heavy flooding. argued.
Forests provide a variety of ecological services, but it cannot yet be said that they produce and conserve water on a large scale. Their tops "prevent 25 percent of the rain from reaching the ground" and their evapotranspiration removes the water from the soil that stops feeding the rivers "where we need it," he said. "Assessing the hydrology of forests remains a challenge," he concluded.
Nobre, on the contrary, defends large forests as "biotic pumps" that attract and produce rain. In his opinion, it is not enough to avoid deforestation of the Amazon, but it is urgent to reforest it, to recover its climate services.
An example to follow is that of Itaipu, which reforested its area of direct influence in the Paraná basin, revitalizing tributaries, through its “Cultivating good water” program.