M.B. Framiftan . M.P. Etala . E.M. Acha . R. A. Guerrero· C.A. Lasta . O.B. Brown
ward to northward with a predominance of northwestward. There is a marked seasonal variability with predominance of westward winds in summer and northwestward
winds in winter. The highest speeds correspond to the northeastward and northwestward winds during winter.
8.2.3
River Input
The Rio de la Plata drains the second largest basin in South America, which, with an
area of 3.1 x 10 6 km>, extends through Argentina, Bolivia, Brazil, Paraguay and Uruguay (Depretis and Griffin 1968). The two major tributaries are the Parana and the
Uruguay Rivers, with annual average discharges of 16000 m3 S-I (15970 m3 S-I) and
6000 m3 S-I (5817 m3 S-I) respectively. These values, provided by the Instituto Nacional
de Ciencia y Tecnicas Hidricas (INCYTH), Argentina, are based on an 111 years river
discharge record of the hydrological station Rosario (Parana River) and 16 years record
of station Salto Grande Abajo (Uruguay River). The Parana River flows into the estuary forming a delta; the main channels are the Parana de las Palmas and the ParanaGuazu. The Uruguay River regime has smaller transport values than the Parana, but
extremely high variability. Maximum and minimum transport correspond to fall and
spring for the Parana, and fall and summer for the Uruguay River, respectively. The
mean transport of minor tributaries is several orders of magnitude smaller; for example, the annual average local discharge into the Samboromb6n Bay, from the Salado
River and the channel system, is estimated as 26 m3 S-I (Consejo Federal de Inversiones 1969). Therefore, the discharge of the Rio de la Plata can be evaluated as the result of the transport of the two major rivers. An average value of 22 000 m3 S-I is estimated, with maximum values during fall. Previous studies suggested a mean value of
20000 m 3 S-I (Urien 1967; CARP 1989), and Tossini (1959) estimated an average of
23 000 m3 S-I at the Rio de la Plata mouth.
8.3
Tides and Tidal Currents
8.3.1
Tides in the Estuary
The tidal waves associated with the South Atlantic amphidromes reach the continental shelf break while propagating northward. Bottom topography and coastline
geometry modify their propagation over the continental shelf, so that they enter
the estuary, in general, from the southeast. Tidal charts for the five main constituents,
M 2 , 52' N 2 , KI and 0 1 (CARP 1989) are shown in Fig. 8.2. The extremely shallow
water shortens tidal wavelengths after they enter the estuary. Due to this effect and
to the considerable length of Rio de la Plata, semidiurnal constituents have the very
unusual feature of a nearly complete wavelength within the estuary at all times, as
can be seen in Fig. 2a-c. Tidal amplitudes are generally not amplified towards the
upper part; the estuary is long and converges only at its innermost part, where it is
extremely shallow and bottom friction plays a fundamental role in controlling the wave
amplitude.
ward to northward with a predominance of northwestward. There is a marked seasonal variability with predominance of westward winds in summer and northwestward
winds in winter. The highest speeds correspond to the northeastward and northwestward winds during winter.
8.2.3
River Input
The Rio de la Plata drains the second largest basin in South America, which, with an
area of 3.1 x 10 6 km>, extends through Argentina, Bolivia, Brazil, Paraguay and Uruguay (Depretis and Griffin 1968). The two major tributaries are the Parana and the
Uruguay Rivers, with annual average discharges of 16000 m3 S-I (15970 m3 S-I) and
6000 m3 S-I (5817 m3 S-I) respectively. These values, provided by the Instituto Nacional
de Ciencia y Tecnicas Hidricas (INCYTH), Argentina, are based on an 111 years river
discharge record of the hydrological station Rosario (Parana River) and 16 years record
of station Salto Grande Abajo (Uruguay River). The Parana River flows into the estuary forming a delta; the main channels are the Parana de las Palmas and the ParanaGuazu. The Uruguay River regime has smaller transport values than the Parana, but
extremely high variability. Maximum and minimum transport correspond to fall and
spring for the Parana, and fall and summer for the Uruguay River, respectively. The
mean transport of minor tributaries is several orders of magnitude smaller; for example, the annual average local discharge into the Samboromb6n Bay, from the Salado
River and the channel system, is estimated as 26 m3 S-I (Consejo Federal de Inversiones 1969). Therefore, the discharge of the Rio de la Plata can be evaluated as the result of the transport of the two major rivers. An average value of 22 000 m3 S-I is estimated, with maximum values during fall. Previous studies suggested a mean value of
20000 m 3 S-I (Urien 1967; CARP 1989), and Tossini (1959) estimated an average of
23 000 m3 S-I at the Rio de la Plata mouth.
8.3
Tides and Tidal Currents
8.3.1
Tides in the Estuary
The tidal waves associated with the South Atlantic amphidromes reach the continental shelf break while propagating northward. Bottom topography and coastline
geometry modify their propagation over the continental shelf, so that they enter
the estuary, in general, from the southeast. Tidal charts for the five main constituents,
M 2 , 52' N 2 , KI and 0 1 (CARP 1989) are shown in Fig. 8.2. The extremely shallow
water shortens tidal wavelengths after they enter the estuary. Due to this effect and
to the considerable length of Rio de la Plata, semidiurnal constituents have the very
unusual feature of a nearly complete wavelength within the estuary at all times, as
can be seen in Fig. 2a-c. Tidal amplitudes are generally not amplified towards the
upper part; the estuary is long and converges only at its innermost part, where it is
extremely shallow and bottom friction plays a fundamental role in controlling the wave
amplitude.