The São Francisco Basin lost 50% of its natural water surface between 1985 and 2020. Taking into account human actions, such as the artificial increase of 13% in reservoir water surface, the net reduction was 4%, with the highest losses observed in the Upper and Lower São Francisco, at 19% and 21% respectively.
The data is part of a study released this Friday (3) by MapBiomas (www.mapbiomas.org) to mark the National Day of Defense of the São Francisco River, at the request of Plano Nordeste Potência, an initiative of a group of Brazilian organizations working towards green and inclusive development of the region.
Human action alone may be insufficient to maintain the resource in the region, especially considering predicted scenarios of reduced rainfall in the coming years. "The creation of reservoirs increases the water surface, however, we have observed a trend of water loss in the main reservoirs, in addition to significant loss of natural water surface in the São Francisco River Basin, which favors a scenario of water crisis," noted Carlos Souza Jr., coordinator of MapBiomas Água.
The study shows how four major reservoirs have exhibited a downward trend in water surface over the past 36 years. The largest decline is recorded at the Luiz Gonzaga hydroelectric plant (formerly Itaparica), between Pernambuco and Bahia, followed by Sobradinho, Três Marias, and Xingó.
"These numbers reflect what we can see in practice. The São Francisco Basin suffers from intense and unplanned use, both of its water resources and its soil. Today, there are populations living in this region that already suffer from these variations. We need to implement solutions such as the restoration of degraded areas as quickly as possible, as well as promoting good resource management," says Renato Cunha, executive coordinator of Gambá (Environmental Group of Bahia).
The São Francisco Basin is the third largest in the country and corresponds to approximately 8% of the national territory. Although there are significant variations between years, the downward trend is clear and adds to previous analyses, including those of the federal government. A study conducted in 2013 by the now-defunct Secretariat of Strategic Affairs of the Presidency, for example, indicated that there could be a loss of up to 65% of the flow by 2040, based on data from 2005.
"The concerning indicators from MapBiomas show that it is urgent to implement a comprehensive revitalization program, which has been planned since the beginning of the transposition project but never carried out. In addition to reforestation actions, the restoration of degraded areas, and sanitation works in hundreds of municipalities, it is essential to have a plan to increase and stabilize the average flow of the river and to incentivize an economy model that promotes the regeneration of the hydrographic basin," proposes Sérgio Xavier, coordinator of the HidroSinergia Project at the Center for Brazil in Climate - CBC, which is developing the Regenerative Economy Lab of the São Francisco River in the border regions of the states of Alagoas, Bahia, Sergipe, and Pernambuco.
Landscape changes
Other data from MapBiomas shows that land use in the basin has intensified over the period. Currently, the coverage of native vegetation in this area is 57%, but it reaches only 30% in the Lower and 37% in the Upper São Francisco.
Despite the presence of consolidated areas for agriculture and pasture, the hydrographic region lost 7 million hectares of native vegetation to agriculture and livestock in the last three decades, leaving 36.2 million hectares remaining. Of these, only 17% are in protected areas. Pastures occupy 14.8 million hectares, and agriculture occupies 3.4 million hectares. The savanna formation was the most affected, losing 4.6 million hectares (14%). In addition to the Cerrado, two other biomes make up the basin: the Atlantic Forest and the Caatinga.
The Lower and Submedium São Francisco regions have the highest rates of pasture area increase, at 50% and 85%, respectively. In the Middle São Francisco, there is a remarkable increase of 650% in agriculture, mainly for soybean expansion in recent years. Meanwhile, in the Upper São Francisco region, silviculture has grown by 400%.
This advancement of agricultural activities is reflected in other indicators. The Middle São Francisco recorded almost 2,000 deforestation alerts in 2019 and 2020, totaling approximately 99,000 hectares cleared. The same sub-region showed the highest growth in the number of irrigation systems since 1985, with an increase of 1,870%, followed by the Upper São Francisco, with 1,586%.
"The São Francisco Basin is under pressure, both from agriculture and energy generation, which puts thousands of people living in the region at risk," adds Washington Rocha, coordinator of the Caatinga team at MapBiomas.