17 The Gulf of Guayaquil
and the Guayas River Estuary, Ecuador
R.R. TWILLEY, w. CARDENAS, V.H. RIVERA-MONROY, J. ESPINOZA,
R. SuEscuM, M. M. ARMIJOS, and L. SoLORZANO
17.1 Introduction
The Gulf of Guayaquil (3°S, 80°W) of the coastal province of Guayas, Ecuador, is the largest (12,000 km 2 ) estuarine ecosystem on the Pacific coast of
South America (Cucal6n 1983). The Gulf has historically been defined by
an outer and an inner estuary (Stevenson 1981). The outer estuary, referred
to as the Gulf of Guayaquil, has a shelf boundary along the 81 ow meridian
with a distance of about 204 km at the mouth of the gulf. The boundary
extends about 130km inland to Puna Island (80°15'W) at the mouths of
Morro and Jambeli channels. The inner estuary, referred to as the Guayas
River estuary, can be classified as a tectonic estuary (Stevenson 1981)
which extends about 7 4 km from its mouth at the northern shore of Puna
Island to the tidal signature of the Guayas River (Fig. 17.1). To the northwest, a relatively large subestuary, known as the Salado, has freshwater
input restricted to wastewater from the city of Guayaquil (population of
2.5 million) and to the southeast, the Churute subestuary is influenced by
the Churute and Taura Rivers. More than 20 rivers, with a total watershed
of 51,230 km 2 , discharge into the Gulf of Guayaquil (Fig. 17.1). The Guayas
River, which forms at the confluence of the Babahoyo and Daule Rivers, has
a drainage basin area of about 32,800 km 2 ( 64 o/o of total drainage basin)
and is the major source offreshwater (20km 3 year- 1 ; Stevenson 1981). The
Taura and Churute River drain a watershed of 1,600 and 300km 2 , respectively. Along the southeast coast, the Jubones and Arenillas Rivers contribute freshwater to the Gulf of Guayaquil and represent 4,830 km 2 of watershed (9.4 o/o of total). The depth of the Gulf of Guayaquil ranges from 183m
along the shelf to 18m along the inner shoals. The depth of the Morro and
Jamb eli channels at the inner boundary of the Gulf is 56 and 22m, respectively, and depth in the Guayas River estuary averages about 9 m.
Ecological Studies, Vol. 144
U. Seeliger and B. Kjerfve (eds.)
Coastal Marine Ecosystems of Latin America
©Springer-Verlag Berlin Heidelberg 2001
and the Guayas River Estuary, Ecuador
R.R. TWILLEY, w. CARDENAS, V.H. RIVERA-MONROY, J. ESPINOZA,
R. SuEscuM, M. M. ARMIJOS, and L. SoLORZANO
17.1 Introduction
The Gulf of Guayaquil (3°S, 80°W) of the coastal province of Guayas, Ecuador, is the largest (12,000 km 2 ) estuarine ecosystem on the Pacific coast of
South America (Cucal6n 1983). The Gulf has historically been defined by
an outer and an inner estuary (Stevenson 1981). The outer estuary, referred
to as the Gulf of Guayaquil, has a shelf boundary along the 81 ow meridian
with a distance of about 204 km at the mouth of the gulf. The boundary
extends about 130km inland to Puna Island (80°15'W) at the mouths of
Morro and Jambeli channels. The inner estuary, referred to as the Guayas
River estuary, can be classified as a tectonic estuary (Stevenson 1981)
which extends about 7 4 km from its mouth at the northern shore of Puna
Island to the tidal signature of the Guayas River (Fig. 17.1). To the northwest, a relatively large subestuary, known as the Salado, has freshwater
input restricted to wastewater from the city of Guayaquil (population of
2.5 million) and to the southeast, the Churute subestuary is influenced by
the Churute and Taura Rivers. More than 20 rivers, with a total watershed
of 51,230 km 2 , discharge into the Gulf of Guayaquil (Fig. 17.1). The Guayas
River, which forms at the confluence of the Babahoyo and Daule Rivers, has
a drainage basin area of about 32,800 km 2 ( 64 o/o of total drainage basin)
and is the major source offreshwater (20km 3 year- 1 ; Stevenson 1981). The
Taura and Churute River drain a watershed of 1,600 and 300km 2 , respectively. Along the southeast coast, the Jubones and Arenillas Rivers contribute freshwater to the Gulf of Guayaquil and represent 4,830 km 2 of watershed (9.4 o/o of total). The depth of the Gulf of Guayaquil ranges from 183m
along the shelf to 18m along the inner shoals. The depth of the Morro and
Jamb eli channels at the inner boundary of the Gulf is 56 and 22m, respectively, and depth in the Guayas River estuary averages about 9 m.
Ecological Studies, Vol. 144
U. Seeliger and B. Kjerfve (eds.)
Coastal Marine Ecosystems of Latin America
©Springer-Verlag Berlin Heidelberg 2001