4 The Orinoco River Delta, Venezuela
J.E. CONDE
4.1 Introduction
The Orinoco River watershed (1.1 x 10 6 km 2 ) is the third largest in the
world and the prevailing hydrographic unit in Venezuela. Between its origin at the Sierra Parima and Sierra Unturan near Brazil and the Atlantic
Ocean, the Orinoco drains more than 2,000 rivers (Depetris and Paolini
1991; Bonilla et al. 1993; Cressa et al. 1993). The distinctive triangularshaped Orinoco Delta (20,000 km 2 ) includes a cluster of ecosystems (Pannier 1979; Lewis et al. 1990; Colonnello 1996) and encompasses more than
300 tributary channels (cafi.os) and several independent streams. Most
channels (e. g. the important Cafi.os Macareo and Manamo) originate as
branches of the Orinoco River at Barrancas. Together with the rivers of the
northeastern plain (San Juan and Guanipa) and the Rio Grande channel,
the delta discharges waters into the Gulf of Paria, the straits Boca de Serpientes and Boca de Dragones and the open sea (Pannier 1979; Fig. 4.1).
The delta itself and the plume are distinct estuarine units; their limits
probably depending on interactions brought about by seasonal variations
in runoff and intrusion of tidal fronts.
4.2 Environmental Setting
The annual precipitation in the Orinoco River watershed can be lower than
1,000 mm in the northern lowlands and as high as 8,000 mm in southern
high relief areas (Lewis and Saunders 1989). In the delta, the climate is perhumid tropical (Thornthwaite's classification), with annual rainfall varying between 1,200 and 2,800 mm in the Upper Delta and the coastal perimeter, respectively (Lewis and Saunders 1989). The pluvial regime is
markedly seasonal with two dry and two wet periods. The principal dry
Ecological Studies, Vol. 144
U. Seeliger and B. Kjerfve (eds.)
Coastal Marine Ecosystems of Latin America
© Springer-Verlag Berlin Heidelberg 2001
J.E. CONDE
4.1 Introduction
The Orinoco River watershed (1.1 x 10 6 km 2 ) is the third largest in the
world and the prevailing hydrographic unit in Venezuela. Between its origin at the Sierra Parima and Sierra Unturan near Brazil and the Atlantic
Ocean, the Orinoco drains more than 2,000 rivers (Depetris and Paolini
1991; Bonilla et al. 1993; Cressa et al. 1993). The distinctive triangularshaped Orinoco Delta (20,000 km 2 ) includes a cluster of ecosystems (Pannier 1979; Lewis et al. 1990; Colonnello 1996) and encompasses more than
300 tributary channels (cafi.os) and several independent streams. Most
channels (e. g. the important Cafi.os Macareo and Manamo) originate as
branches of the Orinoco River at Barrancas. Together with the rivers of the
northeastern plain (San Juan and Guanipa) and the Rio Grande channel,
the delta discharges waters into the Gulf of Paria, the straits Boca de Serpientes and Boca de Dragones and the open sea (Pannier 1979; Fig. 4.1).
The delta itself and the plume are distinct estuarine units; their limits
probably depending on interactions brought about by seasonal variations
in runoff and intrusion of tidal fronts.
4.2 Environmental Setting
The annual precipitation in the Orinoco River watershed can be lower than
1,000 mm in the northern lowlands and as high as 8,000 mm in southern
high relief areas (Lewis and Saunders 1989). In the delta, the climate is perhumid tropical (Thornthwaite's classification), with annual rainfall varying between 1,200 and 2,800 mm in the Upper Delta and the coastal perimeter, respectively (Lewis and Saunders 1989). The pluvial regime is
markedly seasonal with two dry and two wet periods. The principal dry
Ecological Studies, Vol. 144
U. Seeliger and B. Kjerfve (eds.)
Coastal Marine Ecosystems of Latin America
© Springer-Verlag Berlin Heidelberg 2001