South America: Water deficits in central Brazil

21 April 2022

THE BIG PICTURE
The 12-month forecast through December indicates water surpluses in the central Amazon Basin in Brazil reaching into Venezuela’s southern tip, deficits in central and southern Brazil, and mixed conditions in the nation’s east.

Surpluses will be primarily moderate in the northern Amazon Basin but will reach exceptional intensity in eastern Amazonas in the central reaches of the Madeira River, a southern tributary of the Amazon. Deficits of varying intensity are forecast in the central states, but anomalies will become more intense in the south in Mato Grosso do Sul, along the Paraná and Paranapanema Rivers, and in Rio Grande do Sul. Some pockets of deficit are forecast for the small states in the far northeast and pockets of surplus in central Bahia and Minas Gerais in the east.

Across the northern arc of the continent, pockets of intense deficit are forecast north of Bogota, Colombia; around Merida, Venezuela, and a belt between the Orinoco and Ventuari Rivers in southern Venezuela; and the border region of Suriname and French Guiana. French Guiana’s capital, Cayenne, can expect surpluses.

In Peru, exceptional deficits are forecast in the middle reaches of the Ucayali River Watershed, and deficits of varying intensity in pockets of the north, through the Cordillera Central region near Lima, and in the far south. Surpluses are expected near Huancayo in the central Peruvian Andes. Surpluses are also forecast from Lake Titicaca in the south through La Paz, Bolivia where anomalies will be severe, and past Lake Poopó where surpluses will be extreme in the Upper Pilcomayo River region. Deficits are forecast in pockets elsewhere in Bolivia, particularly in the east.

Deficits in Paraguay’s eastern two-thirds will reach well into northern Argentina. Anomalies will be exceptional on the Paraná River downgrading to severe as it flows to the Atlantic, and exceptional around the Itaipu Dam reservoir and in the Iberá Wetlands of northeastern Argentina. Moderate deficits will skirt the eastern Pampas region. A pocket of exceptional surplus is forecast in coastal Chubut Province in Patagonia.

Mixed conditions are forecast in northern Chile and exceptional deficits in a vast path from La Serena through most of the nation’s southern extent. Deficits in Chilean Patagonia will cross into Argentina. Exceptional deficits are forecast in Tierra del Fuego and severe deficits in the Falklands.

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

The forecast through June indicates widespread deficits of varying intensity in central Brazil. Deficits will be especially intense in Tocantins, Bahia west of the São Francisco River, and eastern Mato Grosso do Sul. Extreme surpluses are forecast in a pocket of central Bahia and moderate surpluses in the central Amazon Basin. Surpluses are also forecast in several regions of Colombia and pockets in Ecuador and coastal region of Guyana and French Guiana. Intense deficits are expected in eastern French Guiana and in southern Venezuela between the Orinoco and Ventuari Rivers.

In Peru, surpluses will emerge in the northeast and persist near Huancayo; deficits will linger in the center of the county with exceptional deficits in the Department of Ucayali in the Amazon rainforest. Bolivia can expect deficits in the northeast and southeast, and surpluses will persist in pockets of the southwest including La Paz. Mixed conditions are forecast in northern Chile and deficits in the southern half of the country, spilling into Argentina. Some deficits will linger in Argentina on the Pilcomayo and Bermejo Rivers in the north, in Córdoba Province, and near Buenos Aires. A pocket of intense surplus will persist in coastal Chubut.

From July through September, anomalies will retreat from much of the northern arc of the continent. Deficits will downgrade in central Brazil but remain widespread with intense pockets, primarily in Tocantins, Piaui, and Mato Grosso do Sul, and moderate surpluses are forecast in the central Amazon Basin. In Peru, deficits will persist in Ucayali and intensify in Arequipa, and surpluses will persist near Huancayo. Deficits will shrink in Bolivia, downgrade in Chile, and retreat from northern Argentina and the central Pampas, lingering near Buenos Aires. Surpluses will persist in coastal Chubut and emerge in the Southern Patagonia Icefield. Deficits will linger in Patagonia near the Chilean border and in Tierra del Fuego and the Falklands.

The final quarter – October through December – indicates moderate deficits from southern Colombia into Ecuador and Peru, and in Chile. Moderate surpluses will linger in western Bolivia and Chubut, and will increase from southern Bahia, Brazil, into Minas Gerais.

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

IMPACTS
The six million residents of Santiago, Chile are facing water rationing for the first time in the city’s nearly 500-year history. Chile has been in the grip of drought for 13 years, prompting water authorities to initiate a drop in water pressure and rotating water cuts in its capital. Over the last three decades, officials estimate that water availability in Chile has plunged by 10 to 37 percent, with an expected drop of 50 percent by 2060.

Excessive rainfall triggered deadly flooding and landslides in several regions of South America during late March and April. In Brazil’s southeastern state of Rio de Janeiro, 14 people died early in April, most in mudslides and one by electrocution. The city of Petrópolis north of metropolitan Rio de Janeiro suffered yet another deluge, its second in just weeks, leaving five people dead in March following over 230 deaths in February. Flooding and landslides in Colombia claimed a combined 15 lives in Antioquia and Nariño; three people died during flooding in the Paraguayan capital of Asunción; and 20 homes were damaged when the Jalqueño river in Cajamarca, Peru burst its banks.

Northeastern Argentina’s Corrientes Province has seen widespread flooding in April just months after drought-fueled wildfires scorched through the wetlands region.

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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