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
|
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
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.
For more information, please contact:
Andrew K. Johnston
Smithsonian Institution
National Air and Space Museum
Center for Earth and Planetary Studies