South America: Water surplus in N Amazon & the Guianas

21 February 2022

THE BIG PICTURE
The 12-month forecast through October indicates widespread deficits from western Venezuela into Colombia, and in central Peru, southeastern Brazil into Argentina, and throughout Chile. Widespread surpluses are forecast in the northern Amazon Basin.

Deficits will be exceptional in the western Orinoco River watershed, but surpluses are forecast in the Orinoco Delta, Venezuela’s southern tip, and parts of the Guianas. A pocket of intense deficit is forecast in southern French Guiana.

In Brazil, surpluses of varying intensity will be widespread in the northern Amazon River Basin and will reach south of Manaus where an exceptional pocket is expected in the middle region of the Madeira River, a southern tributary. Some deficits are forecast in Brazil’s Northeast, particularly Piauí, but pockets of surplus will form a broken path from Maranhão through Bahia and Minas Gerais. Deficits reaching exceptional intensity are expected in Mata Grosso do Sul, Paraná, and Rio Grande do Sul.

Deficits will be widespread in much of Peru’s northern half and will be intense in the middle Ucayali River Watershed. Southwestern Bolivia can expect surpluses, severe to extreme east of Lake Poopó near the source of the Pilcomayo River. Generally moderate deficits are forecast in eastern Paraguay and northern Uruguay.

In eastern Argentina, deficits are forecast in the Iberá Wetlands of Corrientes Province where anomalies will be exceptional, moderating as they form a path to the south but intensifying again north of the Salado River in Buenos Aires Province. In Argentina’s far northwest, some pockets of surplus are predicted. Deficits are forecast throughout Chile with exceptional deficits in a vast path from La Serena in the north through most of the nation’s southern extent. Deficits in Chilean Patagonia will cross the border into Argentina, eventually downgrading though remaining intense on the Deseado and Chico Rivers. Deficits in the Falklands will be extreme.

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

The forecast through April indicates widespread surpluses in the northern Amazon Basin and the Guianas, though exceptional deficits are expected in southern French Guiana. Surpluses are also expected in the Orinoco Delta, while deficits of varying intensity are forecast in much of the northern Orinoco Watershed. Some pockets of deficit are forecast near Brazil’s northeast coast, in Mato Grosso do Sul, and Rio Grande do Sul. Surpluses will persist in a pocket near Quito, Ecuador. In Peru, intense deficits are expected in Ucayali Department, reaching into neighboring regions of Peru and Brazil. Moderate surpluses will persist in southwestern Bolivia. Deficits are expected throughout much of Chile and will be exceptional from Concepcion to the Gulf of Corcovado, reaching into Argentina. Moderate deficits are forecast in northern Uruguay and eastern Argentina though deficits will be more intense in Córdoba Province, Argentina.

From May through July, much of the continent can expect near-normal water conditions. Moderate surpluses will linger in the Guianas, isolated pockets of the northern Amazon Basin, and southwestern Bolivia. Generally moderate to severe deficits are forecast in the eastern Pampas, southern Chile, Tierra del Fuego, and the Falklands.

The final quarter – August through October – indicates that moderate deficits will increase and surpluses in the Guianas and northern Amazon will nearly disappear as deficits emerge.

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

IMPACTS
A torrential downpour in mid-February caused flooding and a mudslide that left at least 170 people dead and 120 missing in the Brazilian mountain city of Petrópolis north of Rio de Janeiro. Rainfall in the region measured the most the area has experienced in 70 years according to the nation’s national meteorological institute, exceeding the average for the entire month of February in just one day. More than 300 vehicles were swept away as streets turned into rivers.

Earlier in the month, rainfall in Risaralda, Colombia triggered a mudslide that killed 14 people. In Ecuador’s capital, Quito, 28 people died after the heaviest precipitation in two decades. The flooding washed down the nearby Pichincha volcano, sweeping over athletes and spectators at a volleyball game and snapping power lines.

Nearly 900 people were evacuated from the Machu Pichu area of Peru at the end of January as a deluge caused the Alccamayo River to burst its banks. Flooding damaged regional rail tracks, suspending service.

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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