What is the deepest river in Great Britain

Rivers: 4000 meters deep - the secret river of the underworld

The Amazon is a mighty river. The largest in the world, measured by the volume of water it carries. And this great river has an alter ego - albeit not visible on the surface of the earth, but underground. Brazilian scientists from the Observatório Nacional do Brasil have discovered this current at a depth of up to 4,000 meters below the earth's surface: the Rio Hamza. It paves its 6,000-kilometer route from the Andes to the Atlantic Ocean - through the depths of the earth.

The Hamza rises in the Peruvian highlands, in the same area in which the Amazon has its origin. It flows slowly over a width of 200 to 400 kilometers, always parallel to the Amazon. And the underground river is almost as long as the Amazon - with which the Hamza has probably earned the title of the longest underground body of water on earth.

Even its namesake doubts whether the Hamza, named after its discoverer, the geophysicist Valiya Mannathal Hamza, can really be classified as a "river". He has been researching in Brazil for 37 years, is a member of the American Geological Society and has over 100 articles in published in reputable specialist journals.

He used the "river" term "more generically than in the usual sense," Hamza told the British BBC. His colleague Elizabeth Tavares Pimentel from the Universidad Federal del Amazonas had the joint findings at the 12th International Geophysics Congress in Rio de Janeiro at the end of August under the title "Indications of an Underground 'River' beneath the Amazon River: Inferences from Results of Geothermal Studies " presents. There was no peer review process in which uninvolved researchers check the results of their colleagues.

"It's not a real river. You can't compare the Hamza with subterranean rivers in limestone layers," says Juan José Durán from the Madrid Geological and Mining Institute. "Rather, it is more likely to be an aquifer. Logically, they also have a direction of flow." To be a real river, the Hamza clearly lacks momentum.

The flow velocity of the deep current is far lower than that of its above-ground twin. The Amazon covers between 0.1 and two meters per second. The Hamza, on the other hand, only measures between ten and 100 meters per year. That makes it slower than many a glacier, even if it percolates from a depth of about 2000 meters to about 4000 meters during its leisurely course. At 3000 cubic meters per second, the Hamza only moves a fraction of the Amazon water and yet: "More than many other rivers," says Pimentel.

The fact that the Hamza could be discovered at all was made possible by the drilling in the Amazon region carried out by the petroleum company Petrobras in the 1970s and 1980s. On the basis of 241 boreholes in the region and near its inlet rivers Acre, Solimões as well as on the Marajó Island and in Barreirinhas at the mouth, Hamzas were able to prove the constant movement of water masses at 24 degrees Celsius underground by measuring the temperature. A geothermal method that shows water between dense layers of rock and suggests an uninterrupted course of the underground current.

Petrobras geologist Jorge Figueiredo promptly criticized it: "The term 'river' must be deleted," he demanded. Contrary to Hamza, who speaks of an important freshwater reservoir, the deep water of the Amazon basin is "very salty". The geologist Peter Prinz-Grimm from the Goethe University in Frankfurt am Main also believes: "Rock salt occurs in the sediment sequences of the carbon." The quarrel about the "river" status is "unusual" and probably more a sign of the "romantic personality cult" around its discoverer. To speak of a "continuous system" is, however, "bold", since many thresholds in the course of its tributaries are impermeable.

Figueiredo considers it unlikely that the Hamza could break through the watertight rock masses near the Atlantic shore. Hamza suspects that where the Amazon flows into the Atlantic, the underground current is also supposed to feed. Almost 200 kilometers away from the huge delta, the salt content of the ocean is so low in many places that many freshwater fish live here. This suggests that fresh water flows into the sea.