South America: Water deficits to persist in central Brazil

23 April 2019

THE BIG PICTURE
The 12-month forecast through December 2019 indicates water deficits of varying intensity across much of the northern bulk of the continent as well as through most of Chile and pockets of Argentina.

Deficits will be intense across a vast stretch of central Brazil and along many rivers and will include exceptional deficits in Mato Grosso, Tocantins, Minas Gerais, and São Paulo. Exceptional deficits are also forecast for French Guiana, Suriname, southern Venezuela, a pocket in central Bolivia, along the Pacific coast from Peru through the Atacama Desert in Chile, and further south around the Gulf of Corcovado.

Surpluses are forecast in pockets of northeastern Brazil, northwestern Bolivia, and central Paraguay. In Argentina, surpluses are expected in Catamarca and La Rioja Provinces in the northwest; several northeastern provinces; at the intersection of Neuquén, La Pampa, and Rio Negro Provinces; and along the Santa Cruz River in southern Argentina. Primarily moderate deficits are forecast elsewhere in Argentina though deficits will be extreme along the Bermejo River in the north; normal conditions are forecast for much of Buenos Aires Province.

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 in Brazil will shrink and downgrade, with nearly normal conditions returning to much of Pará and Amazonas, and surpluses increasing in northeastern states. Intense deficits are forecast in Mato Grosso, Tocantins, Goiás, eastern Mato Grosso do Sul, Minas Gerais, western São Paulo, and along many rivers including the São Francisco, Parnaíba, Xingu, and Araguaia. Moderate to severe deficits are forecast for Colombia, Venezuela, and Guyana, but deficits will be exceptional in southern Venezuela, Suriname, and French Guiana. Deficits of varying intensity are forecast for much of central Peru and northeastern and central Bolivia. Exceptional deficits will trace a path along the Pacific Coast from Lima, Peru reaching almost to Santiago, Chile, and around the Gulf of Corcovado in southern Chile.

Surpluses will increase in central and eastern Paraguay and are expected to be intense in the center of the country. Other areas of surplus include central La Paz Department in northeastern Bolivia, and Chaco, Santa Fe, Entre Rios, Catamarca, and La Rioja Provinces in Argentina. Primarily mild to moderate deficits are forecast elsewhere in Argentina but deficits will be severe along the Chubut, Chico, and Lower Reaches of the Colorado River.

From July through September, deficits are forecast to downgrade overall but exceptional anomalies will persist in central Brazil in a pattern nearly duplicating the forecast for April through June. Intense deficits along the Pacific Coast will increase in northern Peru reaching into Ecuador but will recede around the Gulf of Corcovado in Chile. Surpluses will persist in northeastern Brazil, central Paraguay, and pockets of northern Argentina. Moderate surpluses are expected to emerge in a line dissecting northern Paraguay.

In the final quarter – October through December – deficits will downgrade to moderate in central Brazil, while moderate to severe deficits emerge in the Amazon Basin and areas of surplus in northeastern Brazil begin to transition to deficit. Intense deficits along the Pacific Coast are expected to shrink slightly in Peru but will persist through the Atacama Desert in Chile. Surpluses will shrink and downgrade in Paraguay and Argentina.

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

IMPACTS
Flash floods in Rio de Janeiro killed at least nine people this month when over 31cm (13 inches) of rain fell on the city within 24 hours. Rio’s mayor declared a crisis, warning residents to stay inside and avoid potentially contaminated floodwaters. Caimans lurked in the waters in streets of one of the city’s favelas after escaping the walls of their confines during the floods. Flooding in Brazil’s northeast killed three people in Piaui State and caused the Coreau River in Ceara to overflow.

Heavy rain caused flooding and landslides in other parts of the continent as well. Flooding of the Paraguay River in Paraguay displaced 20,000 people. In Bolivia, over 2,000 hectares (4,942 acres) of crops and 109 homes were destroyed. A state of emergency was declared in several municipalities in Ecuador due to flooding that displaced hundreds and destroyed 13 homes.

Average annual rainfall in Chile dropped by 50 percent from the 1980’s to 2018. Until as recently as 2011, Lake Aculeo, located one hour outside of Santiago, served as a getaway destination for swimming, sailing, and water-skiing. As of last year, the lake has completely dried up amid a ten-year drought.

One agro-forecasting consultancy is predicting higher than average precipitation for Brazil’s center-south during May and June, increasing speculation that sugarcane areas will be harvested for ethanol production rather than sweetener. Wet conditions typically cause sugarcane to produce more glucose and fructose, sugars which are more convertible to ethanol than sucrose.

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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