CHAPTER 2 ' The Maracaibo System: A Physical Profile
23
where A is the amplitude of each of the waves at the barrier when t = 0 and where
x = 0; 5 is the change in phase per unit of time; t is time measured from high-water at
the barrier; k is the change in phase per unit of distance; x is distance measured from
the barrier; m is the damping coefficient which expressed the attenuation of the wave
due to frictional and other losses.
Nodes are formed where the waves have opposite phases at distances 1,4, %, etc.,
wave lengths from the barrier, and antinodes where the two waves are in equal phases
at liz, 1, etc., wave lengths from the barrier. A node for the semidiurnal constituents
occurs in the northern part of the lake. An antinode for the semidiurnal constituents
occurs in Tablazo Bay at latitude lO o 54'N, and may be presumed to coincide with the
node for the diurnal constituents.
At the barrier high-water and slack water are synchronous, the amplitude of elevation is maximal and that of current is zero. At the node amplitude of elevation is zero,
that of current is maximal and that of high-water changes abruptly by liz period, with
the result that the elevation is rising beyond the node while it is falling between the
node and the barrier. At the antinode the amplitude is again maximal and that of the
current is zero. The time of slack changes abruptly by liz period, with the result that
high-water and slack water becomes synchronous beyond the antinode and occur
112 period before high-water at the barrier.
2.5.2
Water Levels
The monthly mean tidal levels change as much as 0.24 m in the outer Gulf of Venezuela (Redfield 1955), and by as much as 0.23 m in some of the tide gauges in Tablazo
Bay and the Strait (Rodriguez 1973). The pattern is similar to that observed in other
localities of the Venezuelan coast and the Caribbean in general (Patullo et al. 1955;
GriveI1979). The mean annual differences across the Gulf of Venezuela is 0.276 m in a
distance of 45.6 km. The value for this difference between the Strait and the mouth of
the estuary is 0.327 m in 35 km. The difference in level varies with the seasons in the
Gulf, being highest (0.33 m) in January, and lowest (0.18 m) in October. Tablazo Bay
and the Strait show similar variations with maximum and minimum differences in
March (0.38 m) and September (0.248 m), respectively. These seasonal differences are
clearly related to the prevalence of trade winds (Redfield 1955).
2.5.3
Currents
According to the water balance given above, there is a surplus volume of 49.1 x 10 9 m3 ye'
of fresh water that must be discharged to the sea across the estuary. Up to 56.9% of the
fresh water enters the lake on its south-western corner, through the Catatumbo River
(Escam 1991). Due to the position of the delta of this river its output is discharged perpendicularly to the main axis of the lake, thus creating a south-east current (Fig. 2.4b).
This current is forced by the coastline in a northward direction up to the middle of the
lake where a portion of the surface waters moves forward through the Strait and the
remnant is deflected to the west. Emery and Csanady (1973) observed similar counterclockwise circulations in 39 out of 40 lakes and marginal seas in the northern hemi-
23
where A is the amplitude of each of the waves at the barrier when t = 0 and where
x = 0; 5 is the change in phase per unit of time; t is time measured from high-water at
the barrier; k is the change in phase per unit of distance; x is distance measured from
the barrier; m is the damping coefficient which expressed the attenuation of the wave
due to frictional and other losses.
Nodes are formed where the waves have opposite phases at distances 1,4, %, etc.,
wave lengths from the barrier, and antinodes where the two waves are in equal phases
at liz, 1, etc., wave lengths from the barrier. A node for the semidiurnal constituents
occurs in the northern part of the lake. An antinode for the semidiurnal constituents
occurs in Tablazo Bay at latitude lO o 54'N, and may be presumed to coincide with the
node for the diurnal constituents.
At the barrier high-water and slack water are synchronous, the amplitude of elevation is maximal and that of current is zero. At the node amplitude of elevation is zero,
that of current is maximal and that of high-water changes abruptly by liz period, with
the result that the elevation is rising beyond the node while it is falling between the
node and the barrier. At the antinode the amplitude is again maximal and that of the
current is zero. The time of slack changes abruptly by liz period, with the result that
high-water and slack water becomes synchronous beyond the antinode and occur
112 period before high-water at the barrier.
2.5.2
Water Levels
The monthly mean tidal levels change as much as 0.24 m in the outer Gulf of Venezuela (Redfield 1955), and by as much as 0.23 m in some of the tide gauges in Tablazo
Bay and the Strait (Rodriguez 1973). The pattern is similar to that observed in other
localities of the Venezuelan coast and the Caribbean in general (Patullo et al. 1955;
GriveI1979). The mean annual differences across the Gulf of Venezuela is 0.276 m in a
distance of 45.6 km. The value for this difference between the Strait and the mouth of
the estuary is 0.327 m in 35 km. The difference in level varies with the seasons in the
Gulf, being highest (0.33 m) in January, and lowest (0.18 m) in October. Tablazo Bay
and the Strait show similar variations with maximum and minimum differences in
March (0.38 m) and September (0.248 m), respectively. These seasonal differences are
clearly related to the prevalence of trade winds (Redfield 1955).
2.5.3
Currents
According to the water balance given above, there is a surplus volume of 49.1 x 10 9 m3 ye'
of fresh water that must be discharged to the sea across the estuary. Up to 56.9% of the
fresh water enters the lake on its south-western corner, through the Catatumbo River
(Escam 1991). Due to the position of the delta of this river its output is discharged perpendicularly to the main axis of the lake, thus creating a south-east current (Fig. 2.4b).
This current is forced by the coastline in a northward direction up to the middle of the
lake where a portion of the surface waters moves forward through the Strait and the
remnant is deflected to the west. Emery and Csanady (1973) observed similar counterclockwise circulations in 39 out of 40 lakes and marginal seas in the northern hemi-