22 The Colorado River Estuary
and Upper Gulf of California, Baja, Mexico
S. ALVAREZ-BORREGO
22.1 Introduction
Since the times of early explorers the Gulf of California has been described
as an area of high fertility (Leon-Portilla 1972), owing mainly to tidal
mixing and upwelling processes (Alvarez-Borrego et al. 1978). The shallow
northernmost part of the Gulf, the Upper Gulf of California, and the Colorado River delta are an area of reproduction and nursery for many fish species (Guevara-Escamilla et al. 1973). They are also habitat for endangered
endemic species, like the totoaba ( Totoaba macdonaldi) and the small dolphin "vaquita" (Phocoena sinus). In 1993, the Mexican Federal Government
decreed the area as a Reserve of the Biosphere (Reserva de la Bi6sfera del
Alto Golfo de California y Delta del Rio Colorado; Fig. 22.1) .
22.2 Meteorology
The moderating effect of the Pacific Ocean upon the climate of the Gulf of
California is greatly reduced by the almost uninterrupted, up to 3,000-mhigh mountain chain of Baja California. The climate of the Gulf is therefore
more continental than oceanic, with maximum air temperatures of >40 oc
in summer and large diurnal and annual (about 18 oq temperature ranges
(Roden 1964). In winter, air temperature differences between the Gulf and
the Pacific coast of Baja California are small and temperatures decrease
towards the interior of the Gulf, while in summer differences may exceed
10 °C and temperatures increase towards the interior of the Gulf. The northern Gulf has two seasons (Mosifio and Garda 1974). During the mid-latitude winter (November-May), 3- to 6-day events of northwesterly winds
(8-12 m s- 1 ) transport cool, dry desert air over the Gulf and during the subEcological Studies, Vol. 144
U. Seeliger and B. Kjerfve (eds.)
Coastal Marine Ecosystems of Latin America
© Springer-Verlag Berlin Heidelberg 2001
and Upper Gulf of California, Baja, Mexico
S. ALVAREZ-BORREGO
22.1 Introduction
Since the times of early explorers the Gulf of California has been described
as an area of high fertility (Leon-Portilla 1972), owing mainly to tidal
mixing and upwelling processes (Alvarez-Borrego et al. 1978). The shallow
northernmost part of the Gulf, the Upper Gulf of California, and the Colorado River delta are an area of reproduction and nursery for many fish species (Guevara-Escamilla et al. 1973). They are also habitat for endangered
endemic species, like the totoaba ( Totoaba macdonaldi) and the small dolphin "vaquita" (Phocoena sinus). In 1993, the Mexican Federal Government
decreed the area as a Reserve of the Biosphere (Reserva de la Bi6sfera del
Alto Golfo de California y Delta del Rio Colorado; Fig. 22.1) .
22.2 Meteorology
The moderating effect of the Pacific Ocean upon the climate of the Gulf of
California is greatly reduced by the almost uninterrupted, up to 3,000-mhigh mountain chain of Baja California. The climate of the Gulf is therefore
more continental than oceanic, with maximum air temperatures of >40 oc
in summer and large diurnal and annual (about 18 oq temperature ranges
(Roden 1964). In winter, air temperature differences between the Gulf and
the Pacific coast of Baja California are small and temperatures decrease
towards the interior of the Gulf, while in summer differences may exceed
10 °C and temperatures increase towards the interior of the Gulf. The northern Gulf has two seasons (Mosifio and Garda 1974). During the mid-latitude winter (November-May), 3- to 6-day events of northwesterly winds
(8-12 m s- 1 ) transport cool, dry desert air over the Gulf and during the subEcological Studies, Vol. 144
U. Seeliger and B. Kjerfve (eds.)
Coastal Marine Ecosystems of Latin America
© Springer-Verlag Berlin Heidelberg 2001