CHAPTER 2 . The Maracaibo System: A Physical Profile
Fig. 2.5. a Direction and velocity of the current at the center
of main outlet of the estuary
(solid line: surface, broken line:
_z
01bottom); b contemporary tidal
",a:
",0
1. 5
record; c velocity and direction
"z
of the current near the shore
~
(after Rodriguez 1973)
)00.0
':.:
or 0.5
01~a >11) I.
1 1.5
~
°
150
'" Cl z 100
« a:
-'
« a
i=
1 800
2400
TIME (HRS)
0600
25
Redfield's (1961) theory, according to which slack water time must be simultaneous in
all points south of Tablazo Bay.
In the Strait the water which escapes from the epilimnium moves northward, forming a discharge of 500 m3 S-l in the dry season and up to 2600 m3 S-l during the rainy
season (Corona 1964). The movement of masses of water in the Strait and Tablazo Bay
are the result of the following agents: hydraulic forces resulting from differences in
the seasonal mean sea level and mean lake level; tidal forces which alternate in direction; gravity forces arising from differences in the distribution of mass within the
estuary, for instance those produced by differences in salinity which result in density
currents; wind stress acting on the water surface; and frictional resistance on the bottom and on adjacent layers of water.
The interaction of these forces results in a periodical change of direction in the
water escaping from the lake. An example is given in Fig. 2.5 from measurements taken
in San Carlos Island, at the main outlet of the estuary (Febres 1968). There is a time
lag of 5.5 h between high-water time and the time of maximal velocity of current.
Measurements taken near the shore in this same area (Fig. 2.5b) show that the water
flow southward for almost 24 h, with velocities far smaller that at the center of the
channel. This phenomenon have important biological consequences for the immigration of small organisms (e.g. invertebrate larvae) into the estuary, which can penetrate
against a net seaward flow by crawling or swimming along the shore.
Fig. 2.5. a Direction and velocity of the current at the center
of main outlet of the estuary
(solid line: surface, broken line:
_z
01bottom); b contemporary tidal
",a:
",0
1. 5
record; c velocity and direction
"z
of the current near the shore
~
(after Rodriguez 1973)
)00.0
':.:
or 0.5
01~a >11) I.
1 1.5
~
°
150
'" Cl z 100
« a:
-'
« a
i=
1 800
2400
TIME (HRS)
0600
25
Redfield's (1961) theory, according to which slack water time must be simultaneous in
all points south of Tablazo Bay.
In the Strait the water which escapes from the epilimnium moves northward, forming a discharge of 500 m3 S-l in the dry season and up to 2600 m3 S-l during the rainy
season (Corona 1964). The movement of masses of water in the Strait and Tablazo Bay
are the result of the following agents: hydraulic forces resulting from differences in
the seasonal mean sea level and mean lake level; tidal forces which alternate in direction; gravity forces arising from differences in the distribution of mass within the
estuary, for instance those produced by differences in salinity which result in density
currents; wind stress acting on the water surface; and frictional resistance on the bottom and on adjacent layers of water.
The interaction of these forces results in a periodical change of direction in the
water escaping from the lake. An example is given in Fig. 2.5 from measurements taken
in San Carlos Island, at the main outlet of the estuary (Febres 1968). There is a time
lag of 5.5 h between high-water time and the time of maximal velocity of current.
Measurements taken near the shore in this same area (Fig. 2.5b) show that the water
flow southward for almost 24 h, with velocities far smaller that at the center of the
channel. This phenomenon have important biological consequences for the immigration of small organisms (e.g. invertebrate larvae) into the estuary, which can penetrate
against a net seaward flow by crawling or swimming along the shore.