The Maracaibo System, Venezuela
49
3.2.1 Tides and Circulation
The tides in the Maracaibo System change from mixed-diurnal to mixedsemidiurnal types due to the size and morphology of the system. The tidal
amplitude varies between the outer Gulf of Venezuela (20 em), the entrance
of Tablazo Bay (110 em), the southern Maracaibo Strait (20 em), and the
lake (2.5-6 em; Pelegri and Avila 1986). The circulation pattern in the Gulf
of Venezuela is influenced by winds, bottom topography, and outflowing
water from Tablazo Bay, whereas Coriolis forces seem to have little effect.
The low-salinity water of the southern portion of the gulf flows towards
the center where it merges with Caribbean water, causing a cyclonic circulation at the west and anticyclonic circulation at the southeast of the gulf.
Upwelling of deep water occurs at the northwestern section, where highsalinity and low-temperature waters flow to the north and reach the surface (Gines 1982). The dynamics of water in Tablazo Bay and the strait are
dominated by tides, which generate alternate currents (12 h) along the
north-south axis, with a maximum of 1.6 m s- 1 at the mouth of the estuary
and 0.45 m s- 1 at the southern end of the strait. Tidal currents and the
diurnal component are almost absent from Lake Maracaibo. The cyclonic
circulation pattern in the lake, facilitated by the quasi-circular shape, is
initiated by the action of winds and by large freshwater runoff from rivers
at the southeastern corner of the lake (57 o/o from Catatumbo River; Escam
1991).As a consequence, the water in the lake circulates like a gigantic vortex in a counter-clockwise direction (Emery and Csanady 1973), forming a
cone-shaped hypolimnion (Parra Pardi 1983). Near the center of the lake,
in an area of approximately 40km in diameter (Battelle 1974; Parra Pardi
1983 ), surface current velocities can reach up to 0.5 m s- 1 and, though velocities rapidly decrease with depth, the direction does not change. The residence time of water in the lake is about 6 years (Escam 1991). The surplus
volume of freshwater (49.1 x 10 9 m 3 year- 1 ) discharges from the epilimnion
of the lake along the eastern coast of the strait at about 500m 3 s- 1 during
the dry, and up to 2,600 m 3 s- 1 in the rainy season. The final discharge of
freshwater from the Maracaibo System creates a considerable estuarine
zone in the open sea (Rodriguez 2000). In contrast, a deficit in water
balance, usually in February and March, is compensated for by inflowing
seawater from the Gulf of Venezuela.
49
3.2.1 Tides and Circulation
The tides in the Maracaibo System change from mixed-diurnal to mixedsemidiurnal types due to the size and morphology of the system. The tidal
amplitude varies between the outer Gulf of Venezuela (20 em), the entrance
of Tablazo Bay (110 em), the southern Maracaibo Strait (20 em), and the
lake (2.5-6 em; Pelegri and Avila 1986). The circulation pattern in the Gulf
of Venezuela is influenced by winds, bottom topography, and outflowing
water from Tablazo Bay, whereas Coriolis forces seem to have little effect.
The low-salinity water of the southern portion of the gulf flows towards
the center where it merges with Caribbean water, causing a cyclonic circulation at the west and anticyclonic circulation at the southeast of the gulf.
Upwelling of deep water occurs at the northwestern section, where highsalinity and low-temperature waters flow to the north and reach the surface (Gines 1982). The dynamics of water in Tablazo Bay and the strait are
dominated by tides, which generate alternate currents (12 h) along the
north-south axis, with a maximum of 1.6 m s- 1 at the mouth of the estuary
and 0.45 m s- 1 at the southern end of the strait. Tidal currents and the
diurnal component are almost absent from Lake Maracaibo. The cyclonic
circulation pattern in the lake, facilitated by the quasi-circular shape, is
initiated by the action of winds and by large freshwater runoff from rivers
at the southeastern corner of the lake (57 o/o from Catatumbo River; Escam
1991).As a consequence, the water in the lake circulates like a gigantic vortex in a counter-clockwise direction (Emery and Csanady 1973), forming a
cone-shaped hypolimnion (Parra Pardi 1983). Near the center of the lake,
in an area of approximately 40km in diameter (Battelle 1974; Parra Pardi
1983 ), surface current velocities can reach up to 0.5 m s- 1 and, though velocities rapidly decrease with depth, the direction does not change. The residence time of water in the lake is about 6 years (Escam 1991). The surplus
volume of freshwater (49.1 x 10 9 m 3 year- 1 ) discharges from the epilimnion
of the lake along the eastern coast of the strait at about 500m 3 s- 1 during
the dry, and up to 2,600 m 3 s- 1 in the rainy season. The final discharge of
freshwater from the Maracaibo System creates a considerable estuarine
zone in the open sea (Rodriguez 2000). In contrast, a deficit in water
balance, usually in February and March, is compensated for by inflowing
seawater from the Gulf of Venezuela.