The Amazon River is the largest river in the world by the volume of water it discharges into the ocean. This immense waterway drains a basin covering approximately seven million square kilometers. Identifying the river’s most distant source has long been a subject of geographical debate, as determining the true length of the river system hinges on this location. For centuries, explorers and geographers have navigated the labyrinthine network of Andean tributaries to pinpoint where the river’s journey begins.
The Definitive Geographic Location
The generally accepted source of the Amazon River system is a small glacial stream high in the Andes mountains of southern Peru. This starting point is situated in the Arequipa Region, near the volcanic peak known as Nevado Mismi, which rises to an elevation of 5,597 meters.
The specific stream identified as the ultimate source is the Quebrada Carhuasanta, or sometimes the Quebrada Apacheta. These high-altitude trickles are fed by snowmelt and ice, originating on the northern slopes of Nevado Mismi at elevations around 5,170 meters. This location places the headwaters only about 160 kilometers from the Pacific Ocean, despite the river’s 6,400-kilometer journey eastward to the Atlantic.
The Carhuasanta stream is the farthest point from the river’s mouth that maintains a continuous, year-round flow into the main channel. The waters that begin in this cold, arid, high-altitude setting flow into the Apurímac River, initiating the sequence of confluences that form the Amazon.
The Historical Search and Defining Criteria
The search for the Amazon’s headwaters was complicated by the complex, braided nature of the Andean river network. Historically, the Marañón River was often considered the main source due to its greater water volume at the confluence with the Ucayali. Modern hydrology shifted the focus from volume to the principle of “longest continuous flow,” which dictates that the source is the most distant point from the river’s mouth whose waters remain connected to the ocean year-round.
The Apurímac River system, specifically the streams on Nevado Mismi, gained prominence following expeditions in the late 20th and early 21st centuries. Researchers used advanced technology, including GPS mapping and satellite imagery, to precisely measure the length of various tributaries. A 1971 National Geographic expedition initially identified the Carhuasanta stream as the longest continuous source, a finding later confirmed by subsequent surveys.
A debate arose from a 2014 study that proposed the Mantaro River, located farther north in Peru, as the most distant source. Although the Mantaro proved slightly longer than the Apurímac system when measured, this claim faced scrutiny based on the “continuous flow” rule. A hydroelectric dam built in 1974 on the Mantaro, the Tablachaca Dam, diverts the river’s flow, causing a section of the river’s path to run dry annually. This interruption means the Mantaro does not meet the established definition, allowing the Apurímac system to retain its designation as the accepted origin.
Tracing the Flow: From Headwaters to the Amazon Trunk
The glacial stream flowing from Nevado Mismi feeds into the Apurímac River. The Apurímac, which means “speaker of the gods” in Quechua, carves a deep, winding path through the mountainous terrain of the Andes. Its initial course is characterized by steep gradients and narrow canyons as it collects water from other high-altitude tributaries.
The Apurímac continues north for approximately 730 kilometers before merging with the Urubamba River. This confluence forms the Ucayali River, one of the two great headstream rivers of the Amazon. The Ucayali then flows generally north, taking a meandering course through the lower elevations and the beginning of the lowland forest.
After flowing for over 1,600 kilometers, the Ucayali River meets the Marañón River near the city of Nauta in Peru. This juncture, where the Ucayali’s length combines with the Marañón’s greater discharge, is where the main trunk of the Amazon River officially begins. From this confluence, the river flows eastward, passing into Brazil, where it is known as the Solimões before merging with the Rio Negro to become the Amazon River.