South America: Intense water deficits to persist in French Guiana

23 October 2020

THE BIG PICTURE
The 12-month forecast through June 2021 indicates intense water deficits in a vast region of west-central Brazil, and in southern French Guiana, northern Venezuela, Colombia’s southern corners, and pockets throughout much of Chile.

In Brazil, deficits will be widespread from eastern Rondônia, through Mato Grosso, Tocantins, Goiás, and Mato Grosso do Sul, leading to the Atlantic Coast through the state of São Paulo. Anomalies will be exceptional in many areas but particularly in Mato Grosso. Deficits of varying intensity are forecast in Maranhão on Brazil’s northern coast, and deficits and transitional conditions in its large neighbor, Pará. Some pockets of surplus are expected in the northern Amazon Basin while far western Brazil will see moderate to extreme deficits reaching across the border into Peru.

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In Venezuela, exceptional deficits are forecast in a wide band north of the Apure and Orinoco Rivers, but surpluses are expected in the Orinoco Delta. Central Colombia can also expect surpluses with deficits in the south as previously mentioned. Pockets of moderate deficit are forecast in Ecuador and Peru, and intense deficits in pockets of southern Bolivia. Surpluses are forecast in central Bolivia near Santa Cruz.

Deficits of varying intensity are expected in Chile and across its border into Argentina. Deficits will include exceptional anomalies on the Bío-Bío River in south-central Chile and severe to exceptional deficits near Valparaiso and Santiago.

Moderate to severe deficits are forecast in Argentina’s Chaco Austral region in the north and in the northern Pampas. Scattered, isolated surpluses will trail through western Argentina. In the south, severe deficits are forecast along the Chico River and in Tierra del Fuego, and deficits in the Falkland Islands will be exceptional.

FORECAST BREAKDOWN
The 3-month maps (below) for the same 12-month period show the evolving conditions in greater detail.

The forecast through December indicates that deficits will shrink and downgrade significantly. Near-normal conditions will return to the northern Amazon Basin and deficits in central Brazil will downgrade, becoming mild to moderate. Severe deficits are forecast in Mato Grosso do Sul and through São Paulo State to the Atlantic, spilling into São Paulo’s neighboring states. Deficits will reach exceptional intensity northeast of the metropolis of São Paulo. Exceptional deficits will emerge in Brazil’s easternmost tip.

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Intense deficits remain in the forecast for pockets across the northern arc of the continent in northwestern Venezuela, southern Guyana and Suriname, and French Guiana. Surpluses and deficits will shrink in Colombia. Primarily moderate deficits are expected in Ecuador and Peru with some surpluses lingering in southern Peru. Surpluses in south-central Bolivia will shrink. Conditions in western Paraguay are expected to normalize and moderate deficits are forecast in the east. In Argentina, deficits on the Paraná River will be severe, and deficits in Tierra del Fuego and the Falklands will be extreme to exceptional. Deficits of varying intensity are forecast for Chile.

From January through March 2021, normal water conditions will return to many regions of the continent. Widespread surpluses will emerge from the northern Amazon Basin into southern and eastern Venezuela, northern Guyana, and Suriname. Intense deficits will persist in a pocket of southern Guyana, and deficits of lesser intensity are expected in northwestern Venezuela. Exceptional deficits will persist in Bolivia’s southwestern tip and small pockets of intense deficits will follow Chile’s border with Argentina. Moderate to extreme deficits are expected in central Chile.

In the final quarter – April through June 2021 – surpluses in the north will shrink considerably and the few pockets of deficit that had lingered in the north will retreat. Mild deficits are forecast for Chile, and some small pockets of exceptional deficit will persist in southern Bolivia.

Please note that WSIM forecast skill declines with longer lead times.

IMPACTS
Argentina has become the first nation in the world to approve the use of genetically modified (GMO) wheat, clearing the way for cultivation of the drought-resistant variety. The country’s agricultural community, however, is reluctant to commit without endorsement from its neighbor, Brazil, which purchases 45 percent of Argentina’s wheat exports, and without support from an international market reluctant to accept GMOs.

Drought in the Argentine Pampas continues to take a bite out of wheat forecasts. The Buenos Aires Grains Exchange has again trimmed estimates, by 4 percent in its most recent weekly report after downsizing estimates the prior week.

Dry conditions have fueled fires in Argentina this season that have consumed an area the size of Puerto Rico including in normally wet areas like the Paraná River Delta. Nearly 60 percent of the damage has occurred in two provinces - Córdoba and Entre Ríos.

Loss of Amazon rainforest acreage is contributing to fires, according to a Brazilian hydrologist, by shrinking the region’s atmospheric “flying rivers” that circulate humidity to places like the Paraná River Delta and Brazil’s Pantanal, two regions that have suffered intense fires this year.

Extreme drought in the Pantanal and neighboring Paraguay has dropped the Paraguay River to its lowest level in 50 years, curtailing cargo traffic and increasing shipping costs. The river serves as a conduit for around 85 percent of Paraguay’s foreign trade.

NOTE ON ADMINISTRATIVE BOUNDARIES
There are numerous regions around the world where country borders are contested. ISciences depicts country boundaries on these maps solely to provide some geographic context. The boundaries are nominal, not legal, descriptions of each entity. The use of these boundaries does not imply any judgement on the legal status of any territory, or any endorsement or acceptance of disputed boundaries on the part of ISciences or our data providers.

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