white signature of the turbid waters in the visible
bands of TM frames. The spectral attribute of the
Amazon waters is the key parameter to analyse and
to measure the length of this amazing fluvial system.
S.DEPICTING THE HEADSTREAMS
The Ucayali Basin has two main branches in the
Andean landscapes: Apurimac and Urubamba
rivers. The upper basins of these rivers form a very
complex network of streams with Colca River that
runs to the Pacific and the Titicaca Lake tributaries.
The Urubamba River has a well designed valley
and begins to run from the all weather-snow peaks
(nevados) that divide waters from the Titicaca shed.
These perennial snowed peaks are clearly defined as
greenish blue in TM 3B4G35R color composite.
The Apurimac River from Atalaya to upwards is
refered as Tambo, Ene, Hornillos and Manigote until
to reach the first slope of the Amazon in the Chila
Mountains as part of the Western Andean Ridge of
Southern Peru. The several names applied to
Apurimac just reflect how much imbricated is the
flowing of the river along the steep valleys con-
trolled by the geological structure. The Mount
Quehuicha is the ultimate bound between the slopes
of Colca and Apurimac rivers (figure 2). This mount
was refered as the probable source of the Amazon
by Strain and Engle (1992). Quehuicha is a mount
with lack of perennial snows in the images (TM
003/71 of May 4th 1990 and Shuttle 40.055 of
November 1988). The landscapes of Quehuicha have
aridland brightness dominated by salt, rolled stones
and sand without lakes at all. Quehuicha is higher
then 5,000 meters and rises in latitude South 15
degrees 31 minutes 52 seconds and longitude West
71 degrees 41 minutes 41 seconds. These coordinates
were measured from TM-LANDSAT system-cor-
rected images together with ground control points
and contourlines from DMA map (table 2). There
are two nevados in the vicinities of Queuhicha one
to the Northeast (5,564 meters) and other to
Northwest (5,529 meters). These three mounts are
dividing the upper waters of the Apurimac and the
Colca River.
The Ridge that lies Northwestern from Chila
478
Mountains to Huanzo Range shows at least two sites
where the waters that run to the Pacific and to the
Atlantic may have a seasonal connection. The con-
nections are due mainly to the amount of water in
the glacial lakes that are spread over the suspended
valleys along the ridge. One site is around the lakes
in the upper Velille River the first large tributary of
the left margin of the Apurimac (latitude 15 degrees
5 minutes and longitude 71 degrees 56 minutes). The
other site is the very upper valley of OcoOa River
(Pacific border) in Huanzo Lake (latitude 14 degrees
40 minutes and longitude 72 degrees and 44 min.
utes). The margins of these lakes show scars of
sazonal streams that live the tarns and run to the
North (Atlantic Border) and to the South (Pacific
Border).
6. FIRST RESULTS: MEASUREMENTS
Up to now we have been studying the main
stream of the Amazon and the alternative large and
longer channels that are the opposite margin of the
River around the islands. Examples of channels are
the following:
-Japura Channel: lives the main stream meets
the Japura River and returns to the Amazon down-
wards near the city of Tefe.
-Tapara Channel: lives the main stream and sor-
rounds the Matapa Island near Santarem.
-Breves-Gurupa Channel: lives the Amazon and
meets the Tocantins River to form the Marajo
Island.
These channels are intrinsic part of the Amazon
since they help to design the large fluvial islands.
Those channels are included in the measurements of
the River length. There are however dozens of
shorter channels (locally named as furos and
paranas) that are not being measured because they
are 50-100 meters wide and sharper then the pencil
trace in 250.000 scale.
Turbid sazonal meanders that can be drawn as
the main stream in the flood season were included in
the measurements. These larger meanders are com-
monly found in the low waters of Ucayali (figure 2).
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996
