South America: Intense water deficits forecast for French Guiana

30 May 2019

THE BIG PICTURE
The 12-month forecast through January 2020 indicates water deficits across nearly all the northern bulk of the continent as well as through most of Chile and the eastern Argentine Pampas.

Deficits will be intense across a vast stretch of central Brazil and along many rivers. Areas of exceptional deficit include Mato Grosso, Tocantins, Maranhão, Minas Gerais, and São Paulo. Deficits reaching exceptional intensity are forecast for French Guiana, Suriname, southern Guyana, southern Venezuela, and a pocket in central Bolivia. Deficits of varying intensity will cover Peru and most of Chile and will be especially intense along Peru’s coast, the Atacama Desert in Chile, and further south around the Gulf of Corcovado.

Surpluses are forecast in northwestern Bolivia, central and eastern Paraguay, and Rio Grande do Sul, Brazil, and will be exceptional in central Paraguay. In Argentina, surpluses are expected in Catamarca and La Rioja Provinces in the northwest and several northeastern provinces. Moderate deficits are forecast for Buenos Aires Province, and severe deficits along the Bermejo River in the north and the Chubut and Chico Rivers in the south.

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

The forecast through July indicates that the extent of exceptional deficits on the continent will shrink somewhat, but deficits will dominate much of the northern bulk. Exceptional deficits are forecast for French Guiana, Suriname, and southern Venezuela; central Brazil, the southern Amazon Basin, and many Brazilian rivers; and along the Pacific Coast from, roughly, Lima, Peru through the Atacama Desert in Chile and around the Gulf of Corcovado. Severe deficits are forecast for Buenos Aires Province, Argentina and along the Chubut and Chico Rivers in the south. Surpluses are expected to increase in Paraguay covering the central and eastern portions of the country and will be exceptional in central Paraguay. Moderate surpluses are forecast for southern Brazil and pockets of northern Argentina, with more intense anomalies in northwestern Argentina. Surpluses are expected to persist north of La Paz, Bolivia. Uruguay will transition from surplus to mild deficit.

From August through October, deficits will downgrade in southern Venezuela, Suriname, and French Guiana, with moderate to severe anomalies forecast in coastal nations from eastern Ecuador through French Guiana, and across the breadth of the northern Amazon Basin in Brazil. Extreme to exceptional deficits will increase in the southern Amazon Basin, persist in central Brazil, increase in Minas Gerais, and emerge in pockets of the northeast. Exceptional deficits will emerge in southwestern Ecuador and intense deficits are forecast throughout much of Peru, especially in the west. Exceptional deficits are expected to persist in northern Chile but will retreat from the south. Exceptional surpluses will persist in central Paraguay while surpluses in the eastern region of the country will shrink, as will surpluses in southern Brazil. In Argentina, some surpluses will persist in pockets of the north, deficits will moderate in western Buenos Aires Province as severe deficits emerge farther east, and deficits in southern Argentina will become mild.

In the final quarter – November 2019 through January 2020 – primarily moderate deficits are expected across most of the northern bulk of the continent. Exceptional deficits will persist in the Atacama Desert. Some surpluses will persist in southern Brazil and pockets of northern Argentina but will nearly disappear in Paraguay.

(It should be noted that forecast skill declines with longer lead times.)

IMPACTS
Heavy storms in the northeastern Argentine provinces of Chaco and Corrientes killed at least two people last month. The two were killed by electrocution while they were placing sandbags around their home to mitigate flooding. At least 1,800 people evacuated their homes as floodwaters submerged vehicles and carried them down roads turned to rivers. This year’s El Niño event is being blamed for the heavy rains, though extensive flooding occurred in Argentina, Paraguay, Uruguay, and Brazil in January before El Niño was officially declared.

In Paraguay floods displaced 40,000 people and caused significant losses to the cattle industry since March. Heavy rains that began at the end of April continued into mid-May, drenching some areas with up to 80 mm (3.15 inches) of rain per day, and prompting the government to declare a state of emergency. At least six people were killed in the Presidente Hayes and Alto Paraguay communities, and flooding has largely cut off those areas from access to medical aid.

Flooding in Colombia killed at least 12 people and displaced over 1,000 late last month.

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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