Climate Exchange

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Insurance against droughts and destabilization

of energy costs in Uruguay

Mario Bidegain, Dirección Nacional de Meteorología – Dep. de Climatología and

Guillermo Failache, Usinas y Transmisiones Eléctricas de Uruguay

he Uruguay River covers a total area of approximately

225,000 km

and is, along with the Parana River, one of

the largest contributors to the Rio de la Plata river basin.

he Uruguay River forms in the southern region of Brazil. It

is a transboundary basin forming at first the border between

Brazil and Argentina. This situation continues up to the conflu-

ence with the river Cuarein, where the Uruguay River goes on to

define the border between Argentina and Uruguay and forms the

Rio de la Plata estuary, together with the Parana River.

Average annual precipitation ranges fromabout 2,000mm in the northern

basin (26-29° S, 54-49° E) to over 1,300 mm in the region immediately

south of the basin to the damof SaltoGrande (29-34° S, 59-54° E). Rainfall

is relatively evenly distributed throughout the year. Nonetheless, in the

northern basin rainfall maximums occur in spring (October), while in the

central region and southern basin a double peak can be seen in the autumn

and spring (April and October). Around the northern part of basin,

isaster

isk

eduction

enhanced rainfall in summer is a signature of the Southern

Atlantic Convergence Zone development, especially towards

the east. In winter and spring, on the other hand, enhanced

rainfall is a signature of increased baroclinic activity.

The mean annual temperature in the region ranges

from around 17° C in the south to more than 22° C in

the north. The higher altitudes in the northeastern part of

the Brazilian state of Rio Grande do Sul are substantially

cooler than their surroundings. In winter, monthly mean

temperatures have a clear north-south gradient. In July, for

example, the mean temperature over the northwest part

of the region is more than 20° C, while that in Uruguay

is around 13° C cooler. In summer the gradient is more

zonal, reacting to the land-ocean distribution. In January,

the maximum mean temperatures reach more than 25° C

in the north of Argentina, while they are less than 22.5° C

in the coastal areas of southern Brazil and Uruguay.

Time series observed during the past 30 years indicate significant variability in the amount of rainfall in the Uruguay River basin

Image: Tamara Avellán, WMO