The Hydrography of the Suez Canal
59
Canal and its shallow approaches. A limiting temperature only starts to act
outside the Canal in the open Red Sea or along the Levant Coast of the Mediterranean.
Salinity (Figs. 23 and 24). Salinity is probably the most important environmental factor influencing the settlement of organisms in the Suez Canal. The salt
content ofthe Canal waters has been reasonably weIl investigated during the past
century and it soon became clear that it does not result from a mere gradual
mixing of the Red Sea and Mediterranean water. The reasons for that are threefold: the dissolution ofthe fossil salt dome at the bottom ofthe Great Bitter Lake;
the evaporative concentration in the different lakes and shallows; and an inflow of
Nile waters at different points ofthe northern Canal.
The salinity pattern of the Canal system should, therefore, be treated separately for the different sections of the Canal, and we shall start from south to
north. Understandably, since the Suez Canal is not the central subject of this
book, the presentation below will be restricted to the data relevant to our subject.
The unusual salinities measured in the open sea at Suez-maximum of 44.3%0
in September 1897-have been attributed by Luksch (1898) and Morcos (1970) to
an outflow of brine from the Suez Canal. However, Robinet and Lefort (1874)
indicate an even higher salinity of 45.38%0 at Suez in December 1864, i.e. before
the opening of the Suez Canal. This is anormal salinity in the shallows of the
northern Red Sea and the Gulf of Suez. Por (1972) found values of 46%0 at Ras el
Misalla (about 15 km south of Suez) and 43.39%0 at Ras Sudr (50 km south of
Suez) in 1970. The high salinity values found in the Gulf of Suez are due to the
water losses by evaporation in this shallow gulf. According to Miller and Munns
(1974), the Gulfis "more conducive to evaporation than any other maritime area"
and its high salinity has therefore not to be attributed "to the leaching of the
Bitter Lake salt beds".l
The Bitter Lakes constitute the main high-salinity barrier in the Canal system.
Early authors, such as Krukenberg (1888a), believed that evaporation is the
main factor determining the high salinity of the Lakes. Keller (1882) attached
equal importance to evaporation and dissolution of the Bitter Lake salt deposits.
Starting with Tillier (1901), who, however, does not give reliable original measurements, attention began to focus exclusively on the dissolution of the salt dome.
Based on the original thickness of the dome (13 m as given by de Lesseps) Fox
(1929) calculated that all the salt will have been dissolved by the end of the 20th
century. Wüst (1935) found a direct relation between the increase in the depths of
the Bitter Lakes, i.e. in his view between the progressive dissolution of the salt
bank, and the decrease in salinity. In 1951 however, Wüst reached a new conclusion, namely that the decrease in salinity is asymptotical. Krauss (1958) was the
first to accept that the salinity of the Bitter Lakes will always remain above
normal sea salinity even after complete dissolution of the salt, owing to evaporation. Despite this, Oren (1969) still believed that the final values will eventually be
as low as 41%0.
1 Note added in proof: Morcos and Messieh (1973b) seem to find evidence that after the
cessation of the Nile floods the salinity in Suez Bay may decrease since less Bitter Lakes
waters reach this bay.
59
Canal and its shallow approaches. A limiting temperature only starts to act
outside the Canal in the open Red Sea or along the Levant Coast of the Mediterranean.
Salinity (Figs. 23 and 24). Salinity is probably the most important environmental factor influencing the settlement of organisms in the Suez Canal. The salt
content ofthe Canal waters has been reasonably weIl investigated during the past
century and it soon became clear that it does not result from a mere gradual
mixing of the Red Sea and Mediterranean water. The reasons for that are threefold: the dissolution ofthe fossil salt dome at the bottom ofthe Great Bitter Lake;
the evaporative concentration in the different lakes and shallows; and an inflow of
Nile waters at different points ofthe northern Canal.
The salinity pattern of the Canal system should, therefore, be treated separately for the different sections of the Canal, and we shall start from south to
north. Understandably, since the Suez Canal is not the central subject of this
book, the presentation below will be restricted to the data relevant to our subject.
The unusual salinities measured in the open sea at Suez-maximum of 44.3%0
in September 1897-have been attributed by Luksch (1898) and Morcos (1970) to
an outflow of brine from the Suez Canal. However, Robinet and Lefort (1874)
indicate an even higher salinity of 45.38%0 at Suez in December 1864, i.e. before
the opening of the Suez Canal. This is anormal salinity in the shallows of the
northern Red Sea and the Gulf of Suez. Por (1972) found values of 46%0 at Ras el
Misalla (about 15 km south of Suez) and 43.39%0 at Ras Sudr (50 km south of
Suez) in 1970. The high salinity values found in the Gulf of Suez are due to the
water losses by evaporation in this shallow gulf. According to Miller and Munns
(1974), the Gulfis "more conducive to evaporation than any other maritime area"
and its high salinity has therefore not to be attributed "to the leaching of the
Bitter Lake salt beds".l
The Bitter Lakes constitute the main high-salinity barrier in the Canal system.
Early authors, such as Krukenberg (1888a), believed that evaporation is the
main factor determining the high salinity of the Lakes. Keller (1882) attached
equal importance to evaporation and dissolution of the Bitter Lake salt deposits.
Starting with Tillier (1901), who, however, does not give reliable original measurements, attention began to focus exclusively on the dissolution of the salt dome.
Based on the original thickness of the dome (13 m as given by de Lesseps) Fox
(1929) calculated that all the salt will have been dissolved by the end of the 20th
century. Wüst (1935) found a direct relation between the increase in the depths of
the Bitter Lakes, i.e. in his view between the progressive dissolution of the salt
bank, and the decrease in salinity. In 1951 however, Wüst reached a new conclusion, namely that the decrease in salinity is asymptotical. Krauss (1958) was the
first to accept that the salinity of the Bitter Lakes will always remain above
normal sea salinity even after complete dissolution of the salt, owing to evaporation. Despite this, Oren (1969) still believed that the final values will eventually be
as low as 41%0.
1 Note added in proof: Morcos and Messieh (1973b) seem to find evidence that after the
cessation of the Nile floods the salinity in Suez Bay may decrease since less Bitter Lakes
waters reach this bay.