CHAPTER 2
The Maracaibo System: A Physical Profile
27
the changes in the tidal wave. These currents are not produced by the ongoing tidal
cycle, but are affected by at least the six preceding tidal cycles.
The pattern of circulation in the Gulf of Venezuela (Fig. 2.6d) is due to the winds,
the presence of the Calabozo Ridge and the output of water from Tablazo Bay. Coriolis
forces seem to have little effect. Redfield (1955) postulated the existence of two estuarine cells, separated from each other by the Calabozo Ridge: The low salinity water
from the lake occupies a band on the southern portion of the gulf, and flows northwesterly to the center of the gulf where it merges with the Caribbean water, with a
cyclonic circulation on the west and an anticyclonic circulation on the south-east. The
effect of this pattern of circulation on the discharge from Tablazo Bay is partly reflected in the distribution of fine-grained sediments in the Gulf of Venezuela (Fig. 2.6b).
An upwelling of deep water has been reported on the north-western section of the
gulf, where high salinity and low temperature waters flow to the north and surfaces
near the Paraguami Peninsula (Ziegler 1964; Gines 1982).
2.6
Salinity
2.6.1
Salinity Patterns
The distribution of surface salinities in the Strait, Tablazo Bay and southern part of
the gulf throughout the year follows a marked seasonal pattern (Fig. 2.3c,d) with maximal values from February to May and minimal from June to August. The low salinity
waters witlIin Tablazo Bay are markedly deflected to the left as a result of the gulf waters
that, driven by the wind through the smaller mouth of the estuary, create a zone of
high salinities, usually in the range of 20-25 and rarely below 6. At the same time, the
output of the Limon River on the north-western corner of Tablazo Bay creates a smaller
estuary of its own within the larger estuary; in localities 16 km up-river the salinity
can reach up to 8 in the dry season and decrease at the river mouth as low as 0.1 in the
wet season. In the Strait the surface salinities are more constant, with fluctuations
from 2-6 for most of the year. Throughout the navigation channel that crosses Tablazo
Bay and the Strait there is a typical estuarine stratification related to the saline wedge
that enters from the gulf (Rodriguez 1973).
The effect of the discharge of the estuary can be observed up to the center of the
gulf, 12°N and 71°W, where salinities of 33-34 can be found (Ziegler 1964), although it
is in the southern part where this effect is most strongly felt. Figure 2.6c shows the
position of the isohaline of 30 at 6-7 m depth in the southern portion the gulf for January, March, June, August and October (Rodriguez 1973). A marked stratification can
be observed in Calabozo Bay, with vertical differences of 2 in 12 m, but on the outer
gulf the differences are very small. Ziegler (1964) found at l2°N 36.550 and 36.735 for
the surface and 60 m depth, respectively.
Tides produce cyclical alterations on the local distributions of salinities in the center
of Tablazo Bay where there is a semidiurnal fluctuation at all levels up to 1.5 corresponding to velocity fluctuations in the current.
The access of sea water to the lake through the Strait balances the deficit of freshwater from the large rivers to the south. As already mentioned, the Catatumbo River
The Maracaibo System: A Physical Profile
27
the changes in the tidal wave. These currents are not produced by the ongoing tidal
cycle, but are affected by at least the six preceding tidal cycles.
The pattern of circulation in the Gulf of Venezuela (Fig. 2.6d) is due to the winds,
the presence of the Calabozo Ridge and the output of water from Tablazo Bay. Coriolis
forces seem to have little effect. Redfield (1955) postulated the existence of two estuarine cells, separated from each other by the Calabozo Ridge: The low salinity water
from the lake occupies a band on the southern portion of the gulf, and flows northwesterly to the center of the gulf where it merges with the Caribbean water, with a
cyclonic circulation on the west and an anticyclonic circulation on the south-east. The
effect of this pattern of circulation on the discharge from Tablazo Bay is partly reflected in the distribution of fine-grained sediments in the Gulf of Venezuela (Fig. 2.6b).
An upwelling of deep water has been reported on the north-western section of the
gulf, where high salinity and low temperature waters flow to the north and surfaces
near the Paraguami Peninsula (Ziegler 1964; Gines 1982).
2.6
Salinity
2.6.1
Salinity Patterns
The distribution of surface salinities in the Strait, Tablazo Bay and southern part of
the gulf throughout the year follows a marked seasonal pattern (Fig. 2.3c,d) with maximal values from February to May and minimal from June to August. The low salinity
waters witlIin Tablazo Bay are markedly deflected to the left as a result of the gulf waters
that, driven by the wind through the smaller mouth of the estuary, create a zone of
high salinities, usually in the range of 20-25 and rarely below 6. At the same time, the
output of the Limon River on the north-western corner of Tablazo Bay creates a smaller
estuary of its own within the larger estuary; in localities 16 km up-river the salinity
can reach up to 8 in the dry season and decrease at the river mouth as low as 0.1 in the
wet season. In the Strait the surface salinities are more constant, with fluctuations
from 2-6 for most of the year. Throughout the navigation channel that crosses Tablazo
Bay and the Strait there is a typical estuarine stratification related to the saline wedge
that enters from the gulf (Rodriguez 1973).
The effect of the discharge of the estuary can be observed up to the center of the
gulf, 12°N and 71°W, where salinities of 33-34 can be found (Ziegler 1964), although it
is in the southern part where this effect is most strongly felt. Figure 2.6c shows the
position of the isohaline of 30 at 6-7 m depth in the southern portion the gulf for January, March, June, August and October (Rodriguez 1973). A marked stratification can
be observed in Calabozo Bay, with vertical differences of 2 in 12 m, but on the outer
gulf the differences are very small. Ziegler (1964) found at l2°N 36.550 and 36.735 for
the surface and 60 m depth, respectively.
Tides produce cyclical alterations on the local distributions of salinities in the center
of Tablazo Bay where there is a semidiurnal fluctuation at all levels up to 1.5 corresponding to velocity fluctuations in the current.
The access of sea water to the lake through the Strait balances the deficit of freshwater from the large rivers to the south. As already mentioned, the Catatumbo River