South America: Water deficits in eastern Brazil, surpluses in northern Peru

28 March 2017

The Big Picture

The forecast through November 2017, as seen in the 12-month map (above), shows widespread deficits in much of Brazil including a vast extent of exceptional deficits in Brazil’s eastern mid-section. Deficits are also forecast for Venezuela, French Guiana, Bolivia, and Chile.

Surpluses are forecast for central Loreto and San Martín Regions in northern Peru and La Pampa, Argentina.

Impacts
Yet another wildfire in Chile forced evacuation of thousands from the coastal resort town of Vina del Mar, destroying 16 homes and cutting off power to 280,000 households. Drought and high temperatures were contributing factors in this fire event and in widespread fires earlier this year, which Chilean President Bachelet called the "greatest forest disaster" in Chilean history.

Paradoxically, drought played a role in flooding and mudslides near Santiago that left three people dead and contaminated the Maipo River, source of drinking water for the capital and surrounding area. The drought and fires that ravaged central Chile, including Cajón del Maipo where the Maipo River flows, left the region susceptible to racing runoff and mudslides. Water utility Aguas Andinas suspended service for 5 million people due to contamination, forcing schools to close. Roads blocked by mudslides left 400 tourists and residents temporarily isolated.

After last month's flooding in northern Peru which affected 90,000 people, heavy rainfall in mid-March has stuck the capital area of Lima, killing a dozen people, dragging vehicles into the swollen Huaycoloro River, and closing schools nation-wide. Intense rains which authorities attribute to warming of surface waters of the Pacific Ocean have caused the worst flooding in almost 30 years. Overall, nearly 800 towns have declared a state of emergency and the armed forces have been deployed to maintain order.

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

Though the extent of water deficits in South America is expected to shrink overall March through May, severe to exceptional deficits are forecast in central and eastern states of Brazil including southern Pará, Tocantins, Mato Grosso, Goiás, Bahia, Sergipe, Minas Gerais, and northern São Paulo, as well as pockets in the west reaching to Bolivia. Many rivers in northeastern Brazil are visible on the map as paths of exceptional deficits including the São Francisco. Exceptional deficits are also forecast in western French Guiana into eastern Suriname.

Deficits in Bolivia are forecast to shrink in extent and severity overall but pockets of severe to exceptional deficit will persist. Though the extent of exceptional deficits in Chile will shrink slightly, much of the country will remain in deficit conditions with exceptional deficits in the north, in the south near the Gulf of Corcovado, and in southernmost Patagonia. Moderate to exceptional deficits are forecast in coastal Peru.

Surpluses are forecast in southern and eastern Paraguay and may be severe to exceptional from the Verde River in Paraguay reaching south across the border to the Bermejo River in Argentina. Surpluses are also forecast in a dotted north/south line in western Argentina, and in a pocket of central Buenos Aires Province. Primarily moderate surpluses are forecast for Rio Grande do Sul and Paraná in southern Brazil, northern Guyana, Suriname, and parts of Ecuador.

From June through August deficits are forecast to persist across Brazil’s mid-section with exceptional severity in Mato Grosso, Goiás, and Tocantins. Exceptional deficits will emerge in Piauí, and moderate to extreme deficits will emerge across northern Brazil. Scattered deficits will persist in Bolivia and moderate to extreme deficits will emerge in Colombia, Venezuela, and Guyana. Deficits will increase in extent in Suriname, French Guiana, and coastal Peru. Exceptional deficits will persist in northern Chile, while prior deficits in southern Chile are expected to retreat almost entirely. Surpluses will persist in aforementioned areas of Paraguay and Argentina.

The forecast for the latter months – September through November – indicates primarily moderate deficits across much of northern South America, and scattered surpluses in the south.

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