South America: Exceptional water deficits persist in central Brazil (August 23, 2016)

The Big Picture
The forecast through April 2017, as seen in the 12-month map (below), shows widespread water deficits – including large pockets of exceptional deficits (greater than 40 years) – from Brazil’s northern states southward through the center of the country, and deficits trace a path along the Amazon River. Exceptional deficits are also forecast in the Cordillera Real Mountains in western Bolivia, the Gulf of Corcovado in southern Chile, and rivers in southern Argentina.

Impacts
In Brazil drought on the Amazon has slowed food distribution and threatened water supplies in the region. Navigating through the shallow waters takes twice as long, with food arriving at Manaus in eight days instead of four. Rio Branco's only source of fresh water, the Acre River, reached its lowest level in 40 years on August 9. Wells are running dry and the threat of rationing looms.

Wet weather earlier this year in Brazil's southern states rotted bean crops in Paraná and Mato Grosso and has driven prices up by as much as two-thirds since September. This year's harvest of the carioca bean - a Brazilian food staple - is expected to be a quarter less than projected, only 2.6 million tons rather than 3.35 million.

The worst drought in 25 years has damaged half a million hectares of soybean crops in Bolivia with losses estimated at $180 million, according to the National Association of Oilseed and Wheat Producers.

Forecast Breakdown
The 3-month maps (below) for the same 12-month period clearly illustrate the forecast of a transition in the second half of the period away from widespread exceptional deficits in the first half.

During the next three months, however, (August through October) exceptional water deficits are forecast for much of Brazil north of Rio. Moderate (5 to 10 year) to, primarily, extreme (20 to 40 year) deficits are forecast for: southern Guyana, Suriname, French Guiana, northern Venezuela surrounding Caracas, southern Colombia, Ecuador, Peru, rivers in Bolivia, Chile, the Bermejo River in northern Argentina, southern Argentina including Tierra del Fuego, and the Falkland Islands. Surpluses are forecast to persist in central Argentina and along the Salado River.

In November and December the extent of exceptional water deficits in Brazil is forecast to diminish though extreme to exceptional deficits will persist along the Amazon River and in the northeastern states of Amapá and Maranhão. From November through January moderate deficits are expected to continue to emerge throughout Colombia, and in western and southern Venezuela, Guyana, Suriname, French Guiana, Ecuador, and Peru. Moderate deficits are also forecast to emerge in southern Rio Grande do Sul, Brazil.

In Chile deficits are forecast to persist though with diminished severity during this period. Likewise, deficits in some parts of southern Argentine will diminish, except along the Rios Negro, Chubut, and Deseado.

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