Brazilian scientists believe they have discovered a gigantic underground river flowing thousands of feet below the mighty Amazon River.

Researchers from the Brazil National Observatory said they found evidence of the existence of an underground river that flows 13,000 feet beneath the Amazon. They believe the subterranean river is about 3,700 miles (6,000 km) long, and about the same length as the Amazon on the surface.

The researchers, led by Valiya Hamza, studied the temperatures of 241 inactive wells drilled by Petrobras in the 1970s and 1980s in the Amazon region. Petrobras provided the researchers with thermal information that allowed them to identify the movement of water 13,100 feet below the Amazon River.

The apparent underground river has been named Rio Hamza -- after the scientist -- who said the Amazon rainforest has two separate drainage systems: the surface drainage through the Amazon and the flow of groundwater through the Hamza deep sedimentary layers.

At 6,000 km, both of the rivers flow from west to east. The Amazon is about 1 kilometer to 100 kilometers in width, while the Hamza is about 200 kilometers to 400 kilometers; however, the Hamza flows at only a fraction of the speed of Amazon.

The starting point of the underground river is believed to be the Acre region under the Andes, and it reaches the sea at Foz do Amazons, flowing through basins of rivers Solimões, Amazon and Marajo.

It is likely that this river is responsible for the low level of salinity in the waters around the mouth of the Amazon, the Brazil National Observatory said in a statement.

Computer simulations show that the groundwater flow is predominantly vertical to about 2,000 feet deep, but changes direction and becomes horizontal at greater depths.

Hamza said he hopes from the early-stage studies to be able to confirm the subterranean flow of water by the end of 2014.

The Amazon is the second longest river in the world and has the largest drainage basin anywhere. The bulk of the Amazon, which accounts for about one-fifth of the world's total river flow, runs through tropical rainforest. The river merges in to the Atlantic Ocean in a broad estuary about 150 miles wide.

If the estimated length of 6,000 km is confirmed, Rio Hamza would follow the Mississippi as the fifth-longest river in the world.

Water Amazon