North and Northeast could lose up to 40% of water in 2040 – 01/31/2024 – Environment

Even in the not too distant future, the climate crisis is expected to hit Brazil hard, with a significant impact on water resources. Without significant cuts in global greenhouse gas emissions, the North, Northeast and part of the Midwest could see a loss of up to 40% of the water available for use in 2040.

In this scenario, the estimate is a substantial increase in the number of stretches of intermittent rivers (which dry up during the dry season), especially near the headwaters. This situation could bring critical situations similar to those that occurred last year, during the historic drought in the Amazon.

The data comes from the study “Impact of Climate Change on Brazilian Water Resources”, developed by ANA (National Water and Basic Sanitation Agency), which will be launched this Wednesday afternoon (31) and was obtained exclusively by Sheet.

The estimate considers a future of high carbon emissions and more than 4.5°C of warming in the world, in relation to temperatures in the period before the Industrial Revolution (from 1850 to 1900). However, even in more optimistic scenarios, with less carbon in the atmosphere and a not-so-hot planet, decreases of 20% in river levels were observed in these regions.

In the most pessimistic scenario, the risk of water shortages for the population in these regions increases, especially in the semi-arid region, with damage to the supply of cities, hydroelectric power generation and agriculture, in addition to health risks.

In the South, on the other hand, the trend is for an increase of, on average, 5% in water availability in 2040. Despite this, there was also an increase in the variability of this indicator.

In other words, even though, in general, there may be more water, its occurrence will be more inconsistent — and often associated with extreme weather events, such as floods, which does not always favor the eventual benefit arising from this increase.

In relation to the Southeast, due to greater uncertainty regarding the occurrence of rain in the climate models used, the changes are not as clear as in the rest of the country, although there is a preponderance of drier scenarios.

The study was prepared using a broad set of climate data, both current and projected for the future, and hydrological modeling, used to obtain basin flows.

As a result, future water availability scenarios were produced for more than 450 thousand stretches of Brazilian rivers, considering three time horizons: from 2015 to 2040, from 2041 to 2070, and from 2071 to 2100.

Criteria such as precipitation levels, evapotranspiration (evaporation of water driven by high temperatures), water availability (water available for use, which is granted by ANA) and flow variation (volume of water that passes through rivers) were analyzed.

“[Observa-se] a general increase in potential evapotranspiration regardless of the hydrographic region, with more pronounced increases in the region [das bacias] Amazon, Paraguay and São Francisco and less pronounced in the Uruguay and South Atlantic hydrographic regions, located in the southern region of Brazil”, states the document.

“This study provides information at the basin scale, at the scale necessary for the manager to take action and use it in his analyses”, states Ana Carolina Argolo, interim director-president of the agency, who highlights ANA’s dialogue with ministries, especially the Environment and Regional Development, in addition to state governments, to develop public policies.

For Ana Paula Fioreze, water resources specialist at the agency, focusing on the scenarios projected for the period from 2015 to 2040 is important because it reflects situations that we are already seeing, with more extensive, intense and frequent periods of drought.

“When we bring it closer, society begins to understand that impact differently, because it will see [estes acontecimentos] in her lifetime and even sees it in her everyday life”, he explains.

According to ANA, the results of the study should be included in the new national climate change adaptation plan, which is being prepared by the federal government and should be released in the second half of 2024.

“Too much drought and too much flooding are not good for anyone,” says Fioreze, highlighting that the analysis can be used by decision makers at different levels.

“Not only the water resources manager, the one who will have to decide who will use water, where and when. But also the sanitation manager, who has to prepare to have redundancy [na infraestrutura]and can even reach large companies, which also have to prepare to depend less on water.”

Possible adaptation measures include, for example, the adoption of more efficient irrigation systems and even crops that are less dependent on large amounts of water.

It is also necessary to consider concerns about energy security, as more than 70% of the electricity used in the country comes from hydroelectric plants, increasing the number of reservoirs.

ANA’s Climate Change coordinator, Saulo Aires de Souza, emphasizes, however, that the projections present in the study cannot be confused with predictions.

“Future scenarios are possible. And, of course, it will depend a lot on whether we continue to emit more or less greenhouse gases,” he says. “As the situation gets worse, what we show is that the reduction in water availability is much more pronounced, mainly because evapotranspiration rates increase. This is a consensus.”