São Francisco has lost 50% of its water surface in the last three decades
The São Francisco Basin lost 50% of its natural water surface area between 1985 and 2020. Considering human actions that, for example, brought an artificial increase of 13% of the reservoir water surface, the reduction was 4%, with the highest losses observed in the upper and lower São Francisco, 19% and 21% respectively.
The data are 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 the Northeast Power Plan, an initiative of a group of Brazilian organizations that work for the green and inclusive development of the region.
Human action alone may be insufficient to maintain the resource in the region, especially considering scenarios of reduced rainfall predicted for 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 the loss of significant natural water surface in the São Francisco River basin, this favors a water crisis scenario," noted Carlos Souza Jr.
The study shows how four major reservoirs have shown a downward trend in water surface area over the last 36 years. The largest of the falls is registered in 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 the water resources and of its soil. Today there are populations living in this region who already suffer from these variations. We need to implement solutions such as the recovery of the degraded areas as soon as possible, besides promoting a good management of the resources", says Renato Cunha, executive coordinator of Gambá (Grupo Ambientalista da Bahia).
The São Francisco Basin is the third largest in the country and corresponds to about 8% of the national territory. Although there are large variations between years, the downward trend is clear and adds to previous analyses, including those of the federal government. A study done 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 the 2005 record.
"The worrying indicators from MapBiomas show that it is urgent to implement a profound revitalization program, planned since the beginning of the transposition project and never carried out. Besides reforestation actions, recomposition of degraded areas and sanitation works in hundreds of municipalities, it is essential to have a plan to raise and stabilize the average flow of the river and incentives for an economic model that boosts the regeneration of the watershed," proposes Sérgio Xavier, coordinator of the HidroSinergia Project, of the Centro Brasil no Clima - CBC, which is developing the São Francisco Regenerative Economy Lab on the borders of the states of Alagoas, Bahia, Sergipe and Pernambuco.
Changes in the landscape
Other data from MapBiomas show that land use in the basin intensified during the period. Currently, the coverage of native vegetation in this area is 57%, but reaches only 30% in the Lower São Francisco and 37% in the Upper São Francisco.
Although there are consolidated areas of agriculture and pasture, the hydrographic region lost 7 million hectares of native vegetation in the last three decades to agriculture and cattle raising, leaving 36.2 million hectares - of these only 17% are in protected areas. Pastures occupy 14.8 million hectares and agriculture 3.4 million. The savannah formation was the most affected, losing 4.6 million hectares (14%). Besides the Cerrado, two other biomes make up the basin: the Atlantic Forest and the Caatinga.
The Lower and Middle São Francisco regions show the highest rates of increase in pasture areas, 50% and 85% respectively. In the Middle São Francisco, the highlight is the 650% increase in agriculture, mainly for the expansion of soy in recent years. In the Upper São Francisco region, forestry grew 400%.
This advance of agricultural activities manifests itself in other indicators. The Middle São Francisco registered almost 2 thousand deforestation alerts in 2019 and 2020, totaling approximately 99 thousand hectares felled. The same sub-region showed the highest growth in the number of irrigation systems since 1985, 1,870%, followed by the Upper São Francisco, with 1,586%.
"The São Francisco basin is under pressure, both for agriculture and for energy generation, which puts thousands of people living in the region at risk," adds Washington Rocha, coordinator of the Caatinga team at MapBiomas.