Could El Niño alleviate São Paulo drought?

Thursday, August 27, 2015

The El Niño Southern Oscillation (ENSO) weather phenomenon could bring higher-than-normal rainfall to Brazil's drought-stricken São Paulo state over the next six months.

According to a study by the International Research Institute for Climate and Society (IRI), ENSO will affect climate conditions for the rest of the year, reaching a peak in 4Q15, and it is more than likely that it will continue until 1Q16.

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El Niño has strengthened over the last month and it is shaping up to be one of the most powerful since 1950. It should be nearly as strong as the 1997-98 event, according to IRI chief forecaster Anthony Barnsten.

More than average rainfall is likely in the southeastern state of São Paulo from September-November and this should continue for three months afterwards, but with less intensity, according to the study.

Most of the heavier rains, however, are expected to fall somewhat further south, affecting the southern Brazilian states of Rio Grande do Sul and Paraná, as well as Uruguay.

Global effects of El Niño in 4Q15 (CREDIT: IRI)


El Niño may just arrive in time to provide much-needed water supplies before the state's Cantareira and Alto Tiete water supply reservoirs dry up.

While Cantareira is already using underground technical reserve water, also known as dead volume water, Alto Tiete was at a level of 14.3% on Thursday, having dropped by around 1 percentage point per week throughout August.

At the same date in 2013 – before the drought – Cantareira was operating at 48.2% of capacity and Alto Tiete at 59.4%.

Meanwhile, state water utility Sabesp is expecting to wrap up a 130mn-real (US$36.1mn) drought prevention project by October.

Aimed at trasfering water from the state's Billings reservoir to the Alto Tietê supply system, it is to be the main emergency project to prevent the start of water rationing by the providing intermittent services in the state.