South America: Water surplus forecast in N Amazon

20 December 2021

THE BIG PICTURE
The 12-month forecast through August 2022 indicates exceptional water deficits across northern Colombia and Venezuela in the northern Orinoco River watershed. Deficits are also forecast in Colombia’s southern tip.

Surpluses are forecast from the Orinoco Delta through primarily the northern regions of the Guianas. Widespread surpluses of varying intensity are expected in the northern and eastern Amazon River Basin of Brazil reaching into southern Venezuela, but a pocket of intense deficit is expected at the confluence of the Amazon and Juruá Rivers in Brazil. A pocket intense surplus is forecast in north-central Mato Grosso and moderate surpluses in pockets of southern Goiás and Minas Gerais.

Deficits are forecast in western Amazonas, Acre, Rondônia, Mato Grosso, Mato Grosso do Sul, eastern Goiás, São Paulo, Paraná, and pockets of Rio Grande do Sul. Anomalies will be intense in Acre’s northwestern tip and from southern Rondônia into Mato Grosso.

Nearly all of Chile will experience deficits, with exceptional anomalies dominating much of the nation from La Serena through Tierra del Fuego. Intense deficits in Patagonia will extend across the border into Argentina, eventually downgrading though remaining exceptional along several southern rivers. Deficits will be extreme in the Falklands. Moderate to extreme deficits are forecast in the Iberá Wetlands of Corrientes Province in Argentina’s northeast, and moderate deficits in Buenos Aires Province north of the Salado River and in Entre Ríos Province. Moderate surpluses are expected in La Pampa Province.

Elsewhere on the continent, mixed conditions are forecast in Ecuador, deficits in many regions of northern Peru and some surpluses in the southeast. Surpluses are also forecast in central Bolivia, but deficits are expected surrounding Tarija in the south and into northeastern Argentina.

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

The forecast through February 2022 indicates that deficits will shrink considerably. However, intense deficits will persist in the Orinoco River Watershed of Colombia and Venezuela, and from Chile’s southern half into Patagonian Argentina. Widespread surpluses will emerge in the Brazilian Amazon, particularly in the north, and nearby regions in southern Venezuela and Colombia. Anomalies will be exceptional in northern Pará, Brazil. Surpluses will increase from the Orinoco Delta in eastern Venezuela through the Guianas. Moderate surpluses will increase in the Brazilian states of Mato Grosso, Goiás, Minas Gerais, Espírito Santo, and Rio de Janeiro. Deficits will shrink and moderate in southern Brazil, but moderate deficits will increase in Uruguay.

In the center of the continent, surpluses will emerge in much of Bolivia, transitioning from former deficit. Moderate surpluses are also forecast in some regions of northern Paraguay, and pockets along Peru’s borders with Brazil and Bolivia. Surpluses will persist near Quito (Ecuador) and deficits in the Marañón River Watershed of Peru. Moderate deficits will linger in northeastern Argentina and north of the Salado River in Buenos Aires Province, though anomalies will be more intense in the northern Iberá Wetlands. Surpluses will increase in northern La Pampa Province, moderate deficits will persist along rivers in the south, and intense deficits in Tierra del Fuego and the Falklands.

From March through May 2022, widespread moderate surpluses will persist in the northern Amazon Basin and nearby regions of Colombia and Venezuela and will downgrade in the Guianas becoming mild to moderate. Deficits will shrink and downgrade overall, leaving lingering anomalies primarily in northern Venezuela and Chile. Anomalies in Chile will bleed across its border into Bolivia and Argentina and will be intense in border regions, the south, Tierra del Fuego and the Falklands. Surpluses will shrink in La Pampa, and moderate surpluses will persist in small pockets of Bolivia, Paraguay, Ecuador, and western Colombia.

The final quarter – June through August 2022 – indicates lingering moderate surpluses primarily in Pará, and scattered deficits following the Andes from Colombia through Chile and Argentina. Deficits are also expected in Tierra del Fuego, the Falklands, and Mato Grosso do Sul.

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

IMPACTS
Flooding in the Brazilian state of Bahia has claimed at least ten lives after excessive rainfall, and prompted deployment of 200 military firefighters to aid in rescue operations. The federal government declared a state of emergency in 50 cities in Bahia and neighboring Minas Gerais State with the affected population totaling over 220,000. One municipality in Bahia recorded 300mm (11.8 inches) of rain over 48 hours, surpassing the norm for the entire month of November.

Long-term rainfall shortages, however, have occupied the attention of Brazil’s National Institute of Meteorology which notes that the nation’s rainfall has been below average in most years since 2012, robbing Brazil of R 50 billion (USD $8.7 billion) in estimated annual GDP according to a prominent economist.

A recent study estimates that close to 17 million animals perished in fires that race through the drought-stricken Pantanal, the massive wetland in Brazil, Bolivia, and Paraguay, in 2020.

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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