South America: Water deficits to persist in Chile

19 December 2016

The Big Picture
The forecast through August 2017, as seen in the 12-month map (below), indicates severe to exceptional water deficits throughout much of Chile, as well as in a scattered swath across Brazil’s mid-section, the Cordillera Real Mountains of Bolivia, and along rivers in southern Argentina. Surpluses are forecast for the Río Guaviare Basin in central Colombia, and parts of the Río Desaguadero Basin in Argentina.

Impacts
Water rationing remains in effect in La Paz, Bolivia where the worst drought in 25 years prompted the government to declare a state of emergency. Climate change in the region has caused glaciers to shrink more than 40 percent in the last three decades, affecting 2 million people who rely on glacier melt for water supply. Dams that supply La Paz with water are running dry and snowless ski resorts have long been deserted.

Chile is experiencing its most extensive drought in history and 2016 could end as the driest of the last 40 years. Patagonian sheep and alpaca farmers reminisce about the abundance of snow in the 1970s which provided a ready water supply for their herds. Some small agricultural communities near Santiago are using “fog catchers”, nets that harvest water from fog.

The temperature in Santiago, Chile reached 37.3°C (99°F) on December 14, breaking a hundred-year record, and the National Forestry Corporation recorded 80 fire incidents the day before. A large fire in the Chilean port city of Valparaiso – the country’s second largest urban district – destroyed 100 homes, forced the evacuation of 400 people, and required the services of nearly 50 fire brigades.

Heavy rains caused flooding in the Argentine provinces of Santa Fe, Cordoba, and Buenos Aires. Some areas received over 200 mm (7.87 inches) of rain in 24 hours, over 600 people were evacuated, and one death was reported.

Six people died when the Cali River overflowed its banks in Cali, Colombia.

Forecast Breakdown
The 3-month maps (below) for the same 12-month period illustrate the forecast of a transition away from widespread exceptional deficits observed in prior months.

However, from December through February large pockets of exceptional deficits are forecast across central Brazil in Acre, western Amazonas, Rondônia, Mato Grosso, and southern Pará. Severe to exceptional deficits are also forecast for: Venezuela, northern French Guiana, the Cordillera Real Mountains of Bolivia, scattered throughout Chile, rivers in southern Argentina, and Tierra del Fuego. Moderate deficits are forecast during this period for: Peru, Bahiá (Brazil), and Buenos Aires (Argentina). Moderate to exceptional surpluses are forecast in central Colombia, and from La Guajira in northeastern Colombia across the border into Venezuela west of Lake Maracaibo. Moderate to severe surpluses are expected in northeastern Brazil across northern Pará. Moderate to extreme surpluses are forecast in La Pampa, Argentina, with both deficits and surpluses for the Desaguadero and Colorado River Basins.

As the forecast moves into March through May, overall conditions improve considerably. Moderate deficits remain in the forecast for Northeast Brazil, northern Venezuela, southern Peru, and Chile. Moderate surpluses are expected in Pará, Brazil; northern Bolivia; and central Paraguay. Exceptional surpluses are forecast north of the Chabut River in Argentina, and both deficits and surpluses will persist between the Negro and Desaguadero Rivers.

The forecast for the latter months – June through August – shows a pattern similar to the prior three months but with an increasing extent and severity of water deficits in Northeast Brazil and northern Chile.

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