South America: Intense water deficits forecast for Suriname & French Guiana

22 March 2019

THE BIG PICTURE
The 12-month forecast through November 2019 indicates water deficits ranging from moderate to exceptional in much of Brazil, with intense deficits forecast along many rivers. Surpluses, primarily moderate, are forecast in northeastern Brazil and in the south.

Brazil’s northern neighbors will also see intense deficits including exceptional deficits in French Guiana, Suriname, Guyana, and pockets of Venezuela. Deficits of varying intensity are expected in Peru, southern Bolivia, Chile, and Argentina. Deficits will reach exceptional intensity in coastal Peru, the Atacama Desert in northern Chile and the Gulf of Corcovado in the south, and Tierra del Fuego. Extreme deficits are expected on the Bermejo River in northern Argentina.

Surpluses are forecast in northwestern Bolivia; central and eastern Paraguay; Uruguay; Argentina’s northeastern provinces and at the intersection of Neuquén, La Pampa, and Rio Negro Provinces.

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

The forecast through May indicates that deficits in Brazil will shrink and downgrade significantly, with nearly normal conditions returning to southern Pará, Maranhão, Tocantins, southeastern Mato Grosso, and southern Goiás. Deficits will downgrade in Roraima but will be severe overall; moderate deficits will increase in northern Amazonas; and deficits will be fairly intense along rivers in the Amazon. Moderate to extreme deficits are forecast for eastern Minas Gerais, Espíritu Santo, and São Paulo, and moderate to severe deficits on the São Francisco River. Surpluses will shrink in northern Pará; emerge in the northeastern states of Piauí, Ceará, Río Grande do Norte, Paraíba, and Pernambuco; and moderate but increase in Río Grande do Sul, reaching into Santa Catarina. Surpluses will also emerge between Río and São Paulo.

Across the northern arc of the continent, primarily moderate to severe deficits are forecast from Colombia through Guyana with exceptional deficits in southern Venezuela. Deficits in Suriname and French Guiana will increase and intensify, becoming exceptional. Deficits of varying intensity are forecast for Peru, Chile, eastern Bolivia, and parts of Argentina, primarily rivers. Deficits will be exceptional in pockets along Peru’s coast, and the Atacama Desert and the Gulf of Corcovado in Chile. Surpluses will shrink in northern Bolivia, shrink and downgrade in central Paraguay, and moderate in northeastern Argentina and Uruguay.

From June through August, deficits are forecast to generally downgrade, except along Peru’s coast where exceptional deficits will increase, tracing a path extending into Chile. Severe to exceptional deficits are forecast for Guyana, Suriname, and French Guiana. Mild to moderate deficits are forecast for Brazil, with more intense pockets in Minas Gerais and northern São Paulo. Deficits will be severe on the São Francisco and Jequitinhonha Rivers in the east. Surpluses will shrink in northeastern Brazil and in Río Grande do Sul but will increase in Santa Catarina and emerge in Paraná and southern Mato Grosso do Sul. Surpluses will increase in Paraguay, shrink somewhat in northeastern Argentina, and conditions in Uruguay will return to normal.

In the final quarter – September through November – deficits will downgrade in eastern Brazil, increase in the Amazon Basin, remain severe across the northern arc of the continent, increase in Peru, and emerge in the Cordillera Real Mountains in western Bolivia. Surpluses will persist in Paraguay, neighboring states in Brazil, and northeastern Argentina, and emerge in central Argentina.

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

IMPACTS
Extreme rain in the Andes mountains in early February destroyed homes and roads in northern Chile. The rains reactivated a 60m (196 ft.) waterfall that has been dry for ten years in the Atacama Desert, the world’s driest desert. At least six people were killed. In the town of Calama, 37,000 residents were left without tap water for four days and hundreds of homes were damaged in the region. In southern Chile, meanwhile, heatwaves fueled forest fires. Climate change is reflected in a pattern of extreme weather events in Chile in recent years. The capital city of Santiago hasn’t received its average annual rainfall in ten years, and temperatures set a record high for the third time in three years.

Heavy rains in Bolivia prompted officials there to declare a national emergency late last month. Dozens of homes were destroyed in the southern departments of Chuquisaca, La Paz, and Potosí by floods and landslides.

In Peru, heavy rain overflowed dozens of rivers, triggering landslides that killed at least 39 people and affected some 8,300 others. Landslides destroyed homes, roads, bridges, crops, and killed over 5,500 animals.

Heavy rain in São Paulo and surrounding areas in Brazil in the second week of March caused flooding that killed at least 11 people. Four deaths occurred as a result of a house collapsing in the rainstorm. São Paulo’s fire department reported that at least 155 trees fell in the city, and several roads were blocked.

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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