A National Geographic Society expedition high in the Andes mountains of Peru has confirmed the source of the mighty Amazon River. The team of explorers from five nations used advanced Global Positioning System equipment to determine the river's source as a stream beginning on the 18,363-foot high mountain Nevado Mismi, the society announced Wednesday.

A National Geographic team established Mismi as the river's source in 1971, but in recent years the possibility has been raised that the actual source is a different stream flowing from another mountain. The new expedition, conducted last July, confirmed the source.

"I was delighted to lead the team of explorers and scientists, despite what we had to overcome — cold, vicious winds, and temperatures well below zero Fahrenheit, high altitude, and very rough terrain," said expedition leader Andrew Pietowski. "The trip's result is a highly reliable map of the Amazon's headwaters and an accurate determination of the river's source."

Pietowski, a native of Poland, is a math teacher in Carmel, N.Y. He led a group of 22 people from the United States, Poland, Peru, Canada and Spain. They traveled by foot, Jeep, bicycle and horseback to explore the five remote Andean rivers that combine to form the Amazon — the Apurimac, Huallaga, Mantaro, Maranion and Urubamba-Vilcanota.

The Apurimac is considered the most distant from the Amazon's mouth. "The source of the Amazon can be defined as the most distant point in the drainage basin from which surface water runs year-round, or the furthest point from which water could possibly flow to the Atlantic," explained geographer Andrew Johnston of the Smithsonian Institution's National Air and Space Museum.

"Nevado Mismi fits both of these definitions," said Johnston, who directed the GPS work on the trek.

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