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Ecuador Drainage
Almost all of the rivers in Ecuador rise in the Sierra region
and flow east toward the Amazon River or west toward the Pacific
Ocean. The rivers rise from snowmelt at the edges of the snowcapped
peaks or from the abundant precipitation that falls at higher
elevations. In the Sierra region, the streams and rivers are narrow
and flow rapidly over precipitous slopes. Rivers may slow and widen
as they cross the hoyas yet become rapid again as they flow
from the heights of the Andes to the lower elevations of the other
regions. The highland rivers broaden as they enter the more level
areas of the Costa and the Oriente.
In the Costa region, the Costa Externa has mostly intermittent
rivers that are fed by constant rains from December through May and
become empty riverbeds during the dry season. The few exceptions
are the longer, perennial rivers that flow throughout the Costa
Externa from the Costa Internal and the Sierra on their way to the
Pacific Ocean. The Costa Internal, by contrast, is crossed by
perennial rivers that may flood during the rainy season, sometimes
forming swamps.
The Guayas River system, which flows southward to the Gulf of
Guayaquil, constitutes the most important of the drainage systems
in the Costa Internal. The Guayas River Basin, including land
drained by its tributaries, is 40,000 square kilometers in area.
The sixty-kilometer-long Guayas River forms just north of Guayaquil
out of the confluence of the Babahoyo and Daule rivers. Briefly
constricted at Guayaquil by hills, the Guayas widens south of the
city and flows through a deltaic network of small islands and
channels. At its mouth, the river forms a broad estuary with two
channels around Puná Island, the deeper of which is used for
navigation.
The second major Costa river system--the Esmeraldas--rises in
the Hoya de Quito in the Sierra as the Guayllabamba River and flows
westward to empty into the Pacific Ocean near the city of
Esmeraldas. The Esmeraldas River is 320 kilometers long and has a
20,000-square-kilometer drainage basin.
Major rivers in the Oriente include the Pastaza, Napo, and
Putumayo. The Pastaza is formed by the confluence of the Chambo and
the Patate rivers, both of which rise in the Sierra. The Pastaza
includes the Agoyan waterfall, which at sixty-one meters is the
highest waterfall in Ecuador. The Napo rises near Mount Cotopaxi
and is the major river used for transport in the Eastern lowlands.
The Napo ranges in width from 500 to 1,800 meters. In its upper
reaches, the Napo flows rapidly until the confluence with one of
its major tributaries, the Coca River, where it slows and levels
off. The Putumayo forms part of the border with Colombia. All of
these rivers flow into the Amazon River. The Galápagos Islands have
no significant rivers. Several of the larger islands, however, have
freshwater springs.
Data as of 1989
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