South America: Water deficits forecast on São Francisco River, surpluses in Uruguay

8 February 2019

THE BIG PICTURE
The 12-month forecast through September 2019 indicates water deficits ranging from moderate to exceptional in many parts of Brazil, its northern neighbors, Peru, and Chile. Areas of exceptional deficit include pockets in the western Amazon Basin, the São Francisco River, southeastern Venezuela, and the Atacama Desert in Chile.

Surpluses are forecast in parts of the continent’s mid-section, and anomalies will be extreme to exceptional in central Paraguay. Primarily moderate surpluses will extend from eastern Paraguay into northeastern Argentina, Uruguay, and Rio Grande do Sul, Brazil. Anomalies may be extreme in a pocket northwest of Buenos Aires. Surpluses are also forecast for northwestern Bolivia, and in a line in the west from La Paz to the southern border; Neuquén Province, Argentina; and, Patagonia surrounding O’Higgins/San Martín Lake and along Río Santa Cruz.

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

The forecast through March indicates that deficits in the Amazon Basin will shrink, with nearly normal conditions returning to Pará and northern Amazonas. Exceptional deficits will persist, however, in southern Amazonas and the center of the country, and intense deficits will emerge the Central-West and Southeast states and along the São Francisco River. Surpluses in northeastern Pará will moderate and surpluses of similar intensity will emerge in nearby coastal regions.

Moderate to exceptional deficits are forecast for Brazil’s northern neighbors though the extent of exceptional conditions will shrink. Other areas of deficit include: Peru, where deficits of varying intensity are forecast scattered throughout the country; Chile, where exceptional deficits are forecast for the Atacama Desert, Santiago, and the Gulf of Corcovado; and southern Argentina, where extreme deficits are expected along parts of the Rios Chubut and Chico.

Surpluses in northwestern Bolivia will increase but moderate, and moderate surpluses will emerge in a line from La Paz to the southern border. Moderate to extreme surpluses will emerge in a block encompassing northeastern Argentina, Uruguay, and Rio Grande do Sul, Brazil, with exceptional surpluses expected in eastern Uruguay. The Bermejo River in northwestern Argentina is forecast to transition from moderate deficit to moderate surplus. Exceptional surpluses will persist around O’Higgins/San Martín Lake in Patagonia and moderate surpluses along Río Santa Cruz.

Deficits are forecast to generally shrink and downgrade from April through June. Mild to moderate deficits are forecast for Brazil, though deficits could reach severe to extreme intensity in pockets of the southeast, including Minas Gerais, Espíritu Santo, and São Paulo, and in the north in Roraima. Intense deficits are forecast for Suriname, as well, and in a long path along the Pacific Coast from northern Peru through northern Chile. Surpluses will shrink somewhat in Bolivia, increase in Paraguay and northern Argentina, and persist but moderate in Uruguay and Rio Grande do Sul, Brazil.

In the final quarter – July through September – deficits will increase over the northern half of the continent and intense deficits will emerge across the center of Brazil. Primarily moderate surpluses are expected to persist in northern Bolivia, northeastern Argentina, and central Paraguay.

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

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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