South America: Intense water deficit in French Guiana

22 April 2020

THE BIG PICTURE
The 12-month forecast through December indicates deficits of varying intensity in many areas, but anomalies will be most widespread and intense in Brazil, French Guiana, and Chile.

Though eastern Brazil will be largely spared, deficits are forecast for much of the remainder of the country and will include exceptional deficits along many rivers including the Amazon, Purus, Tapajos, and Xingu. Deficits will reach exceptional intensity in many states including Amapá in the north; Mato Grosso, Pará, Tocantins, Goías, and Mato Grosso do Sul in central Brazil; Rondônia and Amazonas in the west; and Rio Grande do Sul in the south. Deficits of varying intensity are forecast in São Paulo, Paraná, and Santa Catarina States in the south.

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In the east, pockets of surplus are forecast in a few regions including central Pernambuco and from central Minas Gerais curving southeast.

Across the northern arc of the continent, exceptional deficits are expected in French Guiana, becoming somewhat less intense through Suriname and moderating in southern Guyana. Moving west, deficits will be intense in northwestern and southern Venezuela and eastern Colombia; moderate to extreme in southern Colombia; and primarily moderate in Ecuador.

Peru and Bolivia can expect deficits overall with some moderate surpluses in southeastern Peru. Deficits will be extreme to exceptional east of Lima. The forecast for Chile indicates deficits throughout much of the nation which will be exceptional in many regions including Valparaiso and Santiago. Conditions in Paraguay will be relatively normal though exceptional deficits will trace a path along the Paraguay River through the center of the country, downgrading somewhat as it meets the Paraná River through Argentina, then becoming exceptional again as it approaches Buenos Aires.

Moderate deficits are forecast for Buenos Aires Province in the Argentine Pampas and moderate surpluses in the central Pampas. Some areas of intense deficit are expected in northern Argentina and central Patagonia, and surpluses in the northwestern provinces of La Rioja and Catamarca. Moderate deficits are expected in eastern Uruguay.

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 that deficits will shrink and downgrade throughout the region but will remain widespread. Deficits will moderate in much of Brazil but intense pockets are forecast in Mato Grosso, Mato Grosso do Sul, and Rio Grande do Sul. Deficits will also be intense in French Guiana, Suriname, southern Venezuela, pockets in eastern and southern Bolivia, and along the Paraguay River. Southern Colombia, eastern Ecuador, Peru, Chile, Uruguay, and many regions of Argentina can expect deficits.

Surpluses are forecast in eastern Brazil in Rio Grande do Norte, central Pernambuco, central Bahia, Minas Gerais, southern Espiritu Santo, and around the greater São Paulo metropolitan area. Surpluses are also forecast in north-central and southeastern Peru, northwestern Argentina and the central Argentine Pampas.

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From July through September, conditions in nations forming the northern arc of the continent will normalize overall though deficits will increase in Colombia and exceptional deficits will emerge along Venezuela’s northwestern coast. Deficits will persist in Brazil in a pattern similar to the prior forecast but will intensify, becoming exceptional in Pará and Maranhão, severe in Acre, and moderate in Amazonas. Exceptional deficits will emerge in western Ecuador, and deficits will increase and intensify in Peru. Nearly normal conditions are forecast for Paraguay with exceptional deficits along the northern portion of the Paraguay River. Southern Brazil, Uruguay, and many parts of Argentina’s northern bulk will see normal water conditions. Deficits will persist in much of Chile and in eastern and southern Argentina.

Intense surpluses will persist in northwestern Argentina, and surpluses will persist, but shrink in eastern Brazil, southeastern Peru, and the central Argentine Pampas.

In the final quarter – October through December – moderate deficits are forecast in the western Amazon Basin in Brazil, some coastal areas in northeastern nations, and in Colombia, Ecuador, Peru, central Bolivia, and Chile. A few pockets of intense deficit are expected in southern Bolivia and along Argentina’s northwestern border. Surpluses are forecast in pockets of southeastern Peru and eastern Brazil.

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

IMPACTS
Rainfall deficits in key agricultural regions of Argentina have prompted the nation to negotiate with Brazil for increased water releases from the massive Itapui Dam. The dam, located on the border of Brazil and Paraguay, feeds the Parana River as it moves through Paraguay and Argentina. The river supports a US$20 billion a year crop export business, but drought has reduced the Parana to its lowest level since 1989 threatening the Argentine soy harvest. A low river level also translates into additional costs for shipping companies through a reduction in loading capacity as crops bound for export make their way to port cities.

Summer rainfall deficits could also affect harvests in Brazil where March precipitation measured up to a third below normal in Mato Grosso do Sul, São Paulo, and Paraná states. In the southern state of Rio Grande do Sul, the soybean crop is at an 8-year low.

The current decade-long drought in Chile is the longest since the country began keeping meteorologic records in 1915 and, according to one paleoclimatologist, the longest the region has seen in more than 1,000 years. In March of this year the volume of water in El Yeso, the reservoir that supplies Santiago, a metropolis of over 6.5 million, had fallen to 99 million cubic meters, around 40 percent of its capacity. NASA’s satellite images from March 2020 and March 2016 show a stark difference.

The COVID-19 epidemic has added to Chile’s water woes. One recent study suggests that around 380,000 rural Chileans do not have access to a local water supply and depend on trucked deliveries, making recommended hygiene protocols especially challenging as the virus hits the nation.

Water deficits over the past three months have led to low water levels on the Maroni River that creates the border between French Guiana and Suriname. Some 30,000 indigenous people who live along the river depend on the Maroni to deliver their food supply via boats and canoes, and for trading goods. Due to low water levels, on-board loads are cut in half, threatening food supplies.

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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