'3'
~
i:'
:~
-;;;
'"
CHAPTER 6 • The Argentina Estuaries: A Review
123
gentina (Castaing and Guilcher 1995). They are formed by the discharge into the ocean
of the Deseado, Santa Cruz, Coig Rivers plus the San Julian; which used to receive fluvial discharge trough the Bajo de San Julian, (San Julian Lowland) but at the present
time it is only a net marine embayment.
Only five rivers are found in 1800 km of the Patagonian coast. This fact shows the
poor hydrological resources of this zone. Besides, the Deseado River discharge is limited since the streams from the Buenos Aires and Pueyrred6n lakes at the Andes were
captured by backward erosion towards the Pacific basin (Kiihnemann 1963). The Santa
Cruz River have a mean annual discharge of 697 m3 S-I, being the maximum and minimum mean daily values 2520 and 180 m3 S-1 (Evarsa 1995). Unfortunately, there is no
data from the other watercourses, although it is known that Gallegos and Coig Rivers
have smaller discharges than Santa Cruz.
Patagonian estuaries were formed by the inundation of the old river valley cut
through the Tertiary sediments of Patagonian formation. The Deseado River has a
general WSW-ENE orientation with a form of an elongated 40 km funnel. Its width
vary between 2500 and 400 m within 18 km from its mouth. It has an irregular form
due to the presence of islands, beach ridges and points that originate small bays
(i.e., Uruguay, Concordia). Between Puerto Deseado and its offshore zone the maximum depths vary between 30 and 37 m, but towards its interior, its depth decrease in
a short distance from 20 m to only 5 m (Piccolo and Perillo 1997b).
Even tough the mean spring and neap tides are 4.2 and 2.9 m, respectively, there
are not large tidal flats except in very few places with restricted circulation. According to the nautical charts the maximum tidal velocities of high and low tide vary between 2.5 and 3 m S-I. This indicates the strong dynamics and turbulence that characterize the circulation of its waters. Kiihnemann (1963) describes the strong turbidity
of the Deseado waters produced by the fluvial discharge of volcanic ashes (mostly
white-gray clays) giving Secchi values that vary between 6 m at the mouth to 0.5 at
12 km inland from it. The author also mentions the presence of a turbidity front at its
mouth. Pallares (1968) shows variation of temperature and salinity for a 15 days period at Cavendish Point, the harbour and Uruguay Bay (Fig. 6.13). Maximum and minimum temperatures are observed in January-February (14 0 C) and July-August (50 C),
respectively. Meanwhile salinity variation is small no exceeding 1 psu.
- - PORT
34.0
..... --- PCAVENDISH
a
15
b
- -- B.URUGUAY
33.5
t lO
1\ ,
t!!
l:~"
,
~
2
\ / \
'" Ci i
/~ .. :::I
c..
33.0
..... -:;(
E s
~
- - PORT
-------- P.CAVENOISH
- - - B. URUGUAY
32.S
0
F M A M J
A
0
N D
F M A M J
A
0
N
Fig. 6.13. Annual distribution of a salinity and b temperature in the Deseado River Estuary (modified from Piccolo and Perillo 1997b)
D
~
i:'
:~
-;;;
'"
CHAPTER 6 • The Argentina Estuaries: A Review
123
gentina (Castaing and Guilcher 1995). They are formed by the discharge into the ocean
of the Deseado, Santa Cruz, Coig Rivers plus the San Julian; which used to receive fluvial discharge trough the Bajo de San Julian, (San Julian Lowland) but at the present
time it is only a net marine embayment.
Only five rivers are found in 1800 km of the Patagonian coast. This fact shows the
poor hydrological resources of this zone. Besides, the Deseado River discharge is limited since the streams from the Buenos Aires and Pueyrred6n lakes at the Andes were
captured by backward erosion towards the Pacific basin (Kiihnemann 1963). The Santa
Cruz River have a mean annual discharge of 697 m3 S-I, being the maximum and minimum mean daily values 2520 and 180 m3 S-1 (Evarsa 1995). Unfortunately, there is no
data from the other watercourses, although it is known that Gallegos and Coig Rivers
have smaller discharges than Santa Cruz.
Patagonian estuaries were formed by the inundation of the old river valley cut
through the Tertiary sediments of Patagonian formation. The Deseado River has a
general WSW-ENE orientation with a form of an elongated 40 km funnel. Its width
vary between 2500 and 400 m within 18 km from its mouth. It has an irregular form
due to the presence of islands, beach ridges and points that originate small bays
(i.e., Uruguay, Concordia). Between Puerto Deseado and its offshore zone the maximum depths vary between 30 and 37 m, but towards its interior, its depth decrease in
a short distance from 20 m to only 5 m (Piccolo and Perillo 1997b).
Even tough the mean spring and neap tides are 4.2 and 2.9 m, respectively, there
are not large tidal flats except in very few places with restricted circulation. According to the nautical charts the maximum tidal velocities of high and low tide vary between 2.5 and 3 m S-I. This indicates the strong dynamics and turbulence that characterize the circulation of its waters. Kiihnemann (1963) describes the strong turbidity
of the Deseado waters produced by the fluvial discharge of volcanic ashes (mostly
white-gray clays) giving Secchi values that vary between 6 m at the mouth to 0.5 at
12 km inland from it. The author also mentions the presence of a turbidity front at its
mouth. Pallares (1968) shows variation of temperature and salinity for a 15 days period at Cavendish Point, the harbour and Uruguay Bay (Fig. 6.13). Maximum and minimum temperatures are observed in January-February (14 0 C) and July-August (50 C),
respectively. Meanwhile salinity variation is small no exceeding 1 psu.
- - PORT
34.0
..... --- PCAVENDISH
a
15
b
- -- B.URUGUAY
33.5
t lO
1\ ,
t!!
l:~"
,
~
2
\ / \
'" Ci i
/~ .. :::I
c..
33.0
..... -:;(
E s
~
- - PORT
-------- P.CAVENOISH
- - - B. URUGUAY
32.S
0
F M A M J
A
0
N D
F M A M J
A
0
N
Fig. 6.13. Annual distribution of a salinity and b temperature in the Deseado River Estuary (modified from Piccolo and Perillo 1997b)
D