The Paraná, South America’s second-largest river after the Amazon, has retreated this year to its lowest point since its peak in 1944, affected by cyclical droughts and reduced rainfall upstream in Brazil. Climate change threatens to exacerbate these trends.
The deterioration of the waterway, which connects a giant part of the continent, has harmed riverside communities, hampered the shipment of grain to Argentina and Paraguay and contributed to the accumulation of wildfires, damaging wetland ecosystems.
“This is historic. I’ve never seen it so low in my lifetime,” said Gustavo Alcides Diaz, an Argentine fisherman and hunter from a river island community in Charigue, some 300 kilometers (186 miles) upriver from the Argentine capital Buenos Aires, lamenting the impact on fish stocks and fresh water.
“When it dries up, the water rots. “
The Paraná crisis is part of the multitude of misfortunes occurring around the world that are related to global climate change related to the burning of fossil fuels and the consequent greenhouse gas emissions. World leaders will gather at the United Nations Climate Change Conference. or COP26, which begins Oct. 31 in Glasgow, Scotland, amid warnings from a U. N. panel of experts about climate-related disruptions in the coming decades or even centuries.
The Paraná, which means “like the sea” in the Tupi-Guarani language, was born from the convergence of Brazil’s two primary rivers, the Rio Grande and the Paranaiba. It fills up with water in southern Brazil before its long adventure up the river. La Plata Estuary in Buenos Aires. But those upstream areas have seen rainfall levels decline over the past decade.
A three-decade investigation of thousands of rainfall insights showed that combined average rainfall in Goias, Minas Gerais, Sao Paulo and Mato Grosso do Sul (key states where the river flows) is at its lowest point since at least the early 1990s.
In the four states, which surround the top of the Parana, combined daily precipitation, averaged over 12-months, fell from a high of 160 millimeters three decades ago to just half that amount now, with the biggest drop-off in the last ten years.
“This past year will stand out compared to anything else from the past any way you measure it,” said Isaac Hankes, Refinitiv senior weather research analyst.
Agronomist and climate expert Eduardo Sierra, “Many dams had been built in the La Plata basin, wetlands have been removed to make waterways, to generate electricity, and they haven’t taken care that this all impacts the river’s ability to regulate itself.”
Weather experts have said the Parana’s decline could last at least into next year. October rains have given some respite but the longer-term forecast is not encouraging, with only average or below average water levels predicted into 2022.
“We want an era of immediate river recharge,” said Lucas Chamorro, head of hydrology at the Yacyretá hydroelectric plant, adding that human activities such as raising farm animals, burning land and growing soybeans are impacting the Pantanal wetland in general, as well as the Amazon.
The river’s two-year average intensity at the Argentine breadbasket port of Rosario is the lowest recorded since the historic drought of 1944-45. The river level, measured with intensity index standards, reached -0. 33 meters in August.
It has recovered slightly since then, but is set to recede again at least until December before the arrival of the rainy season. The official National Water Institute’s (INA) intermediate projection is for -0.39 meters by mid-December.
The low tide is 2. 4 meters in Rosario.
“In the more than 40 years that I have been in this business, I had never noticed that the temperature reached 33 centimeters below zero. I had never noticed anything like this,” said Guillermo Wade, director of the Argentine Chamber of Ports and Maritime Activities.
Wade explained that the declining point meant that ships were currently reducing their grain loads by about 20% to general levels and that this would worsen if the river level dropped as expected.
The freighters want to cut between 1,600 and 2,175 tons of grain to save a foot of draft — the distance from the waterline to the rear of the ship — Wade said. Lately the ships left Rosario with a draft of 30 feet compared to the 34 generals. feet.
The difference in water levels in the Paraná was captured through satellite imagery between July 2019 and July 2020 and shows a dramatic drop. The combination of short-wave infrared and visual light makes it possible to distinguish land from water. Declining water levels have had a dramatic impact. In recent years, and in 2020, drought led to a massive buildup of wildfires, visible for miles around, that burned carbon-rich soils.
The arid weather driving the Parana’s decline is in-part driven by a long-term natural cycle of weather patterns, exacerbated by global warming, the burning of wetlands and the construction of dams upriver, said agronomist and climate expert Eduardo Sierra.
“It is a twice in a century event,” said Sierra, who is an advisor to the Buenos Aires grains exchange, adding that a long-term weather cycle had converged with a double hit from the La Niña phenomenon which lowers precipitation.
“Then we have a human cause which is warming, which accentuates all the diversifications of the climate. “
Refinitive; Argentina’s National Water Institute; Fish trap
Jon McClure, Sarah Slobin and Will Dunham