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The current "became a monster": a river dies and another is born in Brazil

2023-02-13T10:41:01.293Z


The Araguari runs out of water for a good part of the year, while the Urucurituba overflows 15 kilometers further on. A hydroelectric plant and the passage of buffaloes have influenced these extreme phenomena that cause significant population exodus


Jaime Lucian dos Santos Filho grew up on a stilt house —a house that is built on wooden stakes in the water— on the Araguari River, in the town of Bom Amigo, in the state of Amapá, in northern Brazil.

His family and the other residents of the village, made up of a few dozen inhabitants, ate fish from the river, raised buffalo on its banks and irrigated their gardens with its waters.

Tracing their flow, they reached the market.

In times of flood, the Araguari could reach four kilometers wide and became a powerful current.

The rest of the year it just flowed.

But conditions began to change in the early 2000s, when Filho noticed the flow dwindling.

Sandbanks were appearing that increased in size little by little.

In 2013, the Araguari had filled with mud to its mouth in the Atlantic, 20 kilometers away, and no longer passed through the town of Bom Amigo.

According to Filho, the change brought advantages, but also problems: "We have a little more land to cultivate, but less water."

Currently, some kilometers of the old riverbed are flooded during a few months of rain.

The rest of the year they dry up and the bed becomes hard as stone.

Stripped of what had motivated the town's existence, its inhabitants left.

The grandson of a fisherman from the town of Junco leans on the wooden walls of his house, which is being eroded by the Urucurituba canal, at the mouth of the Amazon river, in the State of Amapá, in northern Brazil, in April of 2022. The inhabitants of this town were flooded by the current of the river.

Galdieri Dice (Galdieri Dice)

With the Amazon River as a backdrop, children play in the high waters of the Urucurituba, in the town of Junco, which is being eroded by the expansion of the canal's waters.

Given Galderi

Former buffalo herder Domingo Maciel da Costa, from the town of Junco, in a boat in the place where his land used to be, now flooded by the waters of the Urucurituba canal.

He recounts that before the 1990s, the Urucurituba was the width of a city block and there were only a few kilometers from its source in the jungle to its mouth.

Sitting in his boat, he explains: "In a short time he became the monster you see here." PILAR OLIVARES

The Cabo Norte lighthouse structure flooded near the clogged mouth of the Araguari River, in the State of Amapá, in northern Brazil, in late April 2022. Floodplains, enhanced by the interruption of the Araguari River that flows into in the Atlantic Ocean, they comprise a large expanse of intermittent coastal ecosystem that is facing accelerated changes after many years of human intervention through economic activities such as livestock farming and electricity generation.Dado Galdieri

A maritime buoy rests on a floodplain that was once the bed of the Araguari River, a few kilometers north of the town of Bom Amigo.Dado Galderi

A group of children watch the Amazon River at high tide from the platform in front of their town Junco, right next to the Urucurituba channel.Dado Galdieri

Some residents of Igarape Grande talk while a barge carrying buffalo enters the canal in front of their house.

This activity is the basis of the economy in the impoverished, not far from the dry bed of the Araguari river.Dado Galdieri

The last hydroelectric plant built on the Araguari River in Ferreira Gomes, in the state of Amapá, in April 2022. The changes in the hydrodynamics of the Araguari River are possibly related to many years of human intervention, through economic activities such as grazing and the generation of electricity.Dado Galdieri

Zico, a resident of Bom Amigo, starts a diesel engine in the town of Junco.

Nearly a dozen people from this community have already left due to the alteration of the course of the Araguari river.Dado Galdieri

Rozete Tavares serves a meal of buffalo meat at her home, in a town that once sat right on the banks of the Araguari River and now struggles to harness rainwater in the wet season and use it year-round, since the river is too far away.Dado Galdieri (Dado Galdieri)

Moisés Pereira Faria watches the water course as the sun sets over the Amazon River, after a day's work buying açaí berries, an important agricultural product in the area.Dado Galdieri

Huge flocks of scarlet ibis (Eudocimus ruber) on the Urucurituba River, near the confluence with the Araguari River in the State of Amapá, northern Brazil in April 2022.Dado Galdieri

Around the same time, residents of another town called Junco, located about 15 kilometers to the south, also had to abandon their land due to changes in another river.

They had not run out of water, but the current flooded them.

In 2012, Domingo Maciel da Costa got a job guarding a buffalo ranch to the east of the town, in the northern arm of the Amazon.

A small river called Canal Urucurituba cut through the lands and emptied into the Amazon.

Costa says that before the 1990s, the Urucurituba was the width of a city block and only a few kilometers from its source in the jungle to its mouth.

Then it started to grow.

When he started working on the ranch, the current had increased and the river was already 15 kilometers long.

And it kept widening, some days, up to two meters.

Sitting in his boat, which rocks him on the Urucurituba, Costa points with a hand gesture around him: "In a short time he became the monster you see here."

The ranger floats in the water right where the ranch used to be, almost a kilometer from what is now the shore.

“Here were our house, our pastures and our land”, he recalls.

Sides of the same coin

Where did this monster come from?

Scientists who study the Araguari and Urucurituba rivers have come to the conclusion that the plugging of the former and the growth of the latter are sides of the same coin, a consequence of the construction of a hydroelectric dam in the upper reaches of the Araguari and the introduction of water buffalo.

James Best, a geologist at the University of Illinois in the United States, is amazed at the rapidity of the changes.

Still, he foresees more surprises like this in the future, as human encroachment on the world's riverbeds and banks increases.

In an article published in the journal

Nature Geoscience

, Best warned of the large-scale extraction of river sands, the accelerated construction of hydroelectric plants, the introduction of non-native species, and other "stress factors of anthropogenic origin", and predicted "the possibility of an ecosystem collapse in some great rivers”.

A small tidal stream flows across a three-mile-wide plain of sprouting fresh silt with suckers in Amapá, Brazil, on Friday, April 22, 2022. Dado Galdieri

Last April, in the northern branch of the Amazon, just past Junco, one of the inlets on the shore looked like a wide bay.

According to Captain Marlon Pantoja Cardoso, it was the mouth of the Urucurituba, almost a kilometer and a half wide.

He had heard that plugging the mouth of the Araguari made the Urucurituba rise, and it seemed logical to him.

“The water had to go somewhere, and it came here,” he reasons.

Once on the Urucurituba, extensive wetlands flanked the channel where there had once been jungle, and small groups of water buffalo trudged through the mud.

Alan Cunha, professor of Civil Engineering at the Federal University of Amapá,

The Amazon and Araguari rivers occupy two adjacent alluvial plains.

Until the early 2000s, a natural barrier approximately one meter high separated the two rivers, the first of which rises in the Andes, and the second in the Tumucumaque mountains.

From a geological point of view, both plains are young, and are formed by sediments too recent to have consolidated.

For this reason, Cunha affirms, the barrier between its basins is "extremely fragile and vulnerable."

Water buffalo dig furrows in the ground

With government subsidies, ranchers began introducing water buffalo to the area in the 1980s. Currently, around 200,000 of this species roam free.

Compared to cattle, they swim better and eat more kinds of grass, and wade through swamps and shallow streams with ease.

A peculiar trait of their behavior has made them a problem for the Amazon-Araguari divide.

According to Cunha, they move in a file like soldiers, opening furrows in the ground.

Human beings should not be under the illusion that we can tame nature.

She will always be stronger than us

Valdenira Santos, geologist

In the decades that followed the arrival of these animals, their relentless hooves created trenches that fill and empty with each tidal cycle into a branching network of watercourses that amplified the embryonic Urucurituba.

At some point in the late 2000s, trampling, aggravated by the opening of trenches by ranchers, ended up opening a pass between the Urucurituba and the Araguari.

The two basins were connected, and the flow of the second began to flow into the first.

Cunha was probably the first scientist to realize that the Urucurituba was draining the Araguari.

In 2012, when he went down the latter in a motorboat, he saw that near the mouth there were sandbars, where he had expected deep water.

The current was shallower here than in the area from which it had come.

The find puzzled him.

In general, the flow of a river increases downstream due to the contribution of the tributaries.

Residents of Igarape Grande lift a buffalo as it is weighed and sold to a transport barge in the impoverished Montecarlo region, not far from the dry bed of the Araguari river, on April 19, 2022.Dado Galderi

How was it possible? he wondered.

Where did the missing water go?

She retraced his steps and noted what looked like a small incipient stream.

The researcher tied a device to measure current to a tree.

After a week he returned to collect the data.

But the plane was gone, and so was the tree, dragged along by a piece of the bank that had slipped into the branch.

"Then we started to connect the dots," he says.

He had discovered the head of the Urucurituba channel.

By then, the Urucurituba was widening at breakneck speed.

Between the end of 2011 and mid-2016, an average of five meters per month was extended.

Soon it had become as wide and deep as the Panama Canal, and half as long.

The entire current of the Araguari was pouring into the Urucurituba.

"It was a big surprise," recalls the engineer.

The role of hydroelectric power plants

Cunha says that the ranchers and their animals have not been the only cause of the siltation of the lower Araguari and the widening of the Urucurituba.

The Coaracy Nunes plant, the first of the three hydroelectric plants built in the Araguari, also contributed to this.

Valdenira Santos, a geologist at the Institute for Scientific and Technical Research in Macapá, the capital of Amapá, says that the builders "did not take into account the effect that the facility would cause downstream."

Just upstream of the hydroelectric plants, she says, the flow varies greatly from the rainy to the dry season.

The reservoirs built for the plants even out the variations and stabilize the production of electricity, but they also alter the natural movement of the sediments.

The sediments are transported by large waves that go up the river, produced by the tide and known as tidal waves.

In enormous quantities and mixed with his convulsions.

Each year, the Amazon dumps 500 million tons of silt into the Atlantic, about 10 times the total mass of sand and gravel mined in a year in the United States.

A fan of these materials, easily visible from space, stretches 100 kilometers offshore and along the coast, just off the ancient mouth of the Araguari, like coffee grounds scattered on blue glass.

Before the Araguari was plugged, it also had pororocks, and the waves carried thousands of tons of sediment from the Amazon silt fan upriver and deposited it on the river bed.

A maritime buoy rests on a floodplain that was once the bed of the Araguari river, a few kilometers north of the town of Bom Amigo, around the areas between the Amazon and Araguari river basins, almost 200 kilometers northeast of Macapa , the capital of the northernmost Amazonian state of Amapá, April 20, 2022.Dado Galderi

Cunha says that, before, low tides washed away these deposits and kept the mouth of the river clean.

But the natural process of deposition and removal of sediments was disrupted when the Coarcy Nunes hydroelectric power station came online in 1976. During the dry season, when the river's flow reached its minimum level, the operators of the plant retained the water so that will accumulate in your reservoir.

Although the historical data is limited, Cunha points out that it seems that, by becoming weakened, the river could no longer carry the accumulated sediment.

Silt began to clog the lower course of the Araguari.

Its original course was no longer the easiest path for the current.

And so, a part of the water was poured into the Urucurituba.

The specialist suspects that the mud carried by the gradual widening of the Urucurituba aggravated the problem.

The suspended matter in the water was dragged up Urucurituba by the tides that rose from the Atlantic and then deposited at the mouth of the Araguari.

In this way, even more water was poured into the Urucurituba, in a vicious circle.

The rivers keep growing

The Urucurituba continues to grow, flooding forests and advancing through Junco.

Da Costa says the town has also lost just over 10 hectares of palm trees, the equivalent of about 14 football fields, which once produced açai berries, an important cash crop.

José Freitas hopes to be able to build a new house in another place before the river forces him to leave, but he cannot afford to move.

“Everywhere we could go is already owned by someone and we don't have money to buy new land,” he laments.

Near the headwaters of the Urucurituba, the Araguari also continues to widen.

In the town of Pracuúba, located at that fork, many people have dismantled their houses and rebuilt them further inland.

Best, the University of Illinois geologist, says that soon millions of people around the world could find themselves driven from their homes, just like the people of Junco, Bom Amigo and Pracuúba.

Rivers around the world are suffering a multitude of assaults, from dams to pollution to shoreline disruption, he asserts.

“This is going to have serious consequences for the people who live in the river corridors,” he denounces.

The Brazilian geologist Valdenira Santos, from the Institute of Scientific and Technological Research of the State of Amapá, sees a lesson in all this,

and not only for those who live in the river basins.

“Human beings should not be under the illusion that we can tame nature.

She will always be stronger than us,” she asserts.

 This reporting has been produced thanks to a grant from the Pulitzer Center on Crisis Reporting. 

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Source: elparis

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