South America: rivers fall victim to a historic drought

  In South America, the dry season terminated at the end of October leaving a heavy ecological bill. Entire regions of Argentina, Paraguay, Bolivia and southern Brazil were subjected to extreme climatic conditions, causing drought, the drying of rivers and fires. 

Severe drought in a large part of South America

According to the NASA Earth Observatory, signs of drought started to appear in the gravimetric observations made by satellite in southeast Brazil in mid-2018, and spread to parts of Paraguay, Bolivia and norther Argentina in 2020. It is the second most severe drought in South America since 2002, if the extent, duration and volume of water lost are taken into account during this period.

The map opposite shows the storage of shallow groundwater in South America on 26 October 2020, as measured by the satellites GRACE-FO (Gravity Recovery and Climate Experiment Follow On). The colours represent the percentile of humidity, that’s to say the comparison of underground water levels with long-term records for the month of October. The blue zones have more water than usual, while the orange and red zones have less. Those in dark red represent zones undergoing severe drought whose occurrence appears once every 50 years. South America is subject to the meteorological phenomenon “El Niño” (causing floods) or “La Niña” (droughts), present this year.

 

Rivers are at their lowest levels this year

In Argentina, the number of fires increased by 170 % this year. In Paraguay, they rose by 46 %. Another consequence of this exceptionally long and intense drought episode is the drying up of rivers.

The river Parana, one of the most powerful on Earth, which flows from its source in Brazil to continue onwards to the Atlantic Ocean via the estuary of the Rio de la Plata (Argentina), has not been as low since 1970. In Rosario, in eastern Argentina, the level was 80 cm in August, versus 3 to 4 metres normally at this time of year. Likewise, for the river Paraguay, the main tributary of the Parana, which flows from the north southwards and crosses Brazil, Bolivia, Paraguay and Argentina. In October it reached its lowest level for 50 years. According to Argentina’s National Water Institute, the situation is not likely to improve any time soon. Low rainfall is expected to continue, keeping the region’s rivers at a low level. This hydrological situation has damaged river trade on the main Paraná / Paraguayan waterway, an important activity in Paraguay’s economy. The loads transported by boats had to be reduced by 40%, whereas traffic had already been slowed down by the Covid-19 pandemic. At the port of “La Paz” in Argentina, barges coming from Paraguay and other convoys sailing northwards encounter difficulties due to the low water level.

 

Wetlands threatened

Without the usual rainfall and ravaged by fires, the wetlands have also undergone significant damage. In the Parana delta, the fires struck as early as January with unprecedented intensity, transforming over the months thousands of hectares into deserts of ashes.

This year, in Brazil, the Pantanal, the world’s largest tropical wetland located in the centre-west (State of Mato Grosso), was aflame, scoured by violent fires that led many observers to speak of an ecological disaster. More than 16,000 fire outbreaks were recorded in the region of which the most recent, during the dry period, were often uncontrollable. According to experts, this area of exceptional biodiversity, which accommodates about 650 species of birds, 98 species of reptiles and 159 species of mammals, has already lost 20 to 25% of its surface area, meaning 3 to 4 million hectares have gone up in smoke.

The cause of these fires was the severe drought that had already laid waste to the area. During the last rainy season, between October 2019 and March 2020, the level of rainfall in the Pantanal fell by 40% in comparison to the average whereas temperatures climbed. The river Paraguay, the main “faucet” and supplier of water to the huge marshland, suddenly ran dry this year.

The agricultural sector has also been blamed in Argentina and Brazil. The practice of slash and burn (clearance by fire to enlarge farmland and grazing land for livestock) also further contributed to drying the earth.

Lastly, responsibility is also political. First of all there is Brazil, where the current government rejects the reality of climate change: it has stopped monitoring activities by public environmental agencies in protected areas; no actions are taken to prevent fires; the deforestation of the Amazon forests is continuing, and will, according to scientists, have a considerable impact on the country’s rain cycle, particularly in the centre and south. Moreover, many NGOs are calling for better dialogue between the different actor to better regulate and use the land, although drought episodes will likely increase due to climate change.

Credit photo: Ahmad Masood/REUTERS