Mapping the Source of the Amazon


The Source of the Amazon

The search for the most distant extent of the Amazon river system has been a subject of  interest for centuries. Finding the ultimate "source" of a great river is problematic, as there are many ways to define this point. Very often the source is defined by measuring  flow rates of different tributaries and following the route upriver along the routes of greatst flow. However, many hostorical definitions of river sources were made without measuring flow rates. The route to the source was chosen by deciding which "looked" like the dominant tributaries. In this work, the "source" of the Amazon is defined as the point at which water must flow the greatest distance to flow into the Amazon River.

The Rio Lloqueta, a small river in the Andes Mountains, is located in southern Peru about 130 kilometers north of the city of Arequipa. Its watershed covers an area of  about 100 square kilometers at altitudes up to 5300 meters. This area is the most distant catchment of the Amazon River system. The five main tributaries of the Lloqueta, named Carhuasanta, Silanque, Apacheta, Calomarco, and Ccaccansa, reach almost to the summits of the continental divide. The peaks include Nevado Mismi and Quehuisha.

Nevado Mismi

Click here for more about the Lloqueta River and the history of the Amazon's source.


Field Work


Field Team Next to Laguna McIntyre

Preliminary field work was performed in July 1997 to visit the Lloqueta and obtain accurate positions of the river and its tributaries. Portable GPS receivers were used to collect these data. In July 2000, researchers returned to the Lloqueta to perform GPS surveying to obtain accurate position data on the Lloqueta and its tributaries.

During the 2000 field work, more than 20 people were equipped with high-precision GPS equipment. GPS receivers used were Trimble GeoExplorer 3s, GeoExplorer 2s, and Pathfinder Pro XRS. Separate teams mapped all the tributaries of the Llqueta by recording locations as GPS receivers were taken along the path of each stream. Part of the continental diviade was also mapped this way. All GPS data were post processed at a base camp located downstream of the confluence of the tributaries. A GPS base station was maintained at the base camp throught the field work.

Click here to see more images of the 2000 field expedition.


Maps and Images

Maps

Click here to see the maps produced from this field work.

The three-dimentional views graphically demonstrate the physical structure of the Lloqueta basin. The first view shows Quebrada Caruasanta and the perennial ice cover of Nevado Mismi. An overview of the entire southern part of the Lloqueta drainage basin was also created. GPS data were draped over the images. A topographic map including the GPS data collected during field work was also created.

The five main tributaries of the Lloqueta were accurately mapped. Of the five, Carhuasanta had the greatest length with consistant water flow. The Apacheta can have longer surface flow, but this stream has been observed to become dramatically shorter in dry years. The most distant bodies of standing water are Ticlla Cocha and Laguna McIntyre on Nevado Mismi.

Click here for more about how these maps and images were produced.



For more information, please contact:

Andrew K. Johnston
Smithsonian Institution
National Air and Space Museum
Center for Earth and Planetary Studies