资源环境科技发展态势分析平台

The European Commission’s Joint Research Centre has issued an analysis of the  persistent extreme drought, which started in 2019 and is impacting the La Plata Basin, the second largest river basin in South America and the fifth in the world.

WMO contributed to the study published in JRC Publications Repository. It  includes an overview of the event, its climatological background, its spatio-temporal evolution, its causes and characteristics, as well as its impacts on natural and human systems.

The 2019-2021 drought started with below normal precipitation in the upper part of the basin in mid-2019 and has spread through the hydrological cycle affecting soil moisture, flows, groundwater and vegetation. Severe, extreme, and exceptional drought conditions began to appear in the upper basins of the Paraguay and Paraná rivers in south-central Brazil. By the end of 2019 drought conditions were already affecting the Brazilian states of Mato Grosso, Goias, Sao Paulo and Paraná, and in Paraguay and central Argentina.

This situation continued during 2020 and northern Argentina and the Pampas of central-eastern Argentina suffered widespread drought as well by the end of the year.

The ongoing 2019-2021 La Plata Basin dry event can be already ranked among the top five events in South-Eastern South America since the 1950s. Most of the parameters included in the present classification (severity, intensity, and peak) show that the ongoing drought falls behind the 1968-1971 event because of its shorter duration.

In most parts of the La Plata Basin, La Niña is often accompanied by drought, leading to particularly negative impacts in southern Brazil, north-eastern Argentina, Paraguay and Uruguay.

Recent observations and seasonal forecasts suggest that La Niña conditions may be back again in October-November 2021 and lasting till 2022 spring, thus delaying the return to normal conditions in the La Plata Basin, including river flows. This is in line with most seasonal precipitation forecasts from global model ensembles, which indicate a precipitation deficit scenario in the middle and lower part of the La Plata Basin.

According to the impacts reported and attributed to this event, many sectors including agriculture, inland water navigation, energy production, water supply and several ecosystems have been suffering from the ongoing drought. However, total damage estimates and characterisation of all affected sectors can be performed only once the event will be over.

WMO chief scientist Juerg Luterbacher and scientist Cristian Escobar were among the authors of the study.