128 



Alfred C. Redfield 



difference in level varies with the season, being highest (1-1 ft.) in January, and lowest 

 (0-6 ft.) in October (Fig. 12, B). 



The seasonal difference in levels across the Gulf is clearly related to the prevalence 

 of north-easterly winds, as shown by wind data from Maracaibo (Fig. 12, D). The 

 difference in levels may be explained in part by the reduced density of the water at the 

 head of the Gulf. The magnitude of the difference is, however, so great as to raise a 

 question as to the precision of the levelling between Las Piedras and Zaparita Island. 

 There can be little doubt, however, that the mean tide level at Zaparita is one-half foot 

 greater, relative to the level at Las Piedras when the north-east trades are at a maxi- 

 mum, than it is when their influence is reduced. Clearly winds which affect the slope 

 of the sea surface so greatly are adequate to produce the effects on the circulation 

 which have been deduced from the hydrographic observations. 



3.0 



2 5 



2 



"I — I — r 



"1 — I — r 



ZAPARITA 



- LAS PlEOPAS 



-A MEAN TIDE LEVEL 



J I I i I I \ I I L 



J I L 



I 2 



10 



0.8 



06 



04 



I I I I r 



1 — I — r 



1 I 1 r 



B DIFFERENCE IN LEVEL 

 J I I I I I I I I I I [ I L 



-4 



T — r 



2 — 



- C WATER BALANCE l. maracaibo - 

 J I I I l__l I I I I I I I L 



"I — I — I — I — I — r 



100 — 



80 — 



1 — I — r 



• D WIND AT MARACAIBO 



I I I I I I I I I I I L 



J L 



M A M J 



S N 



M A M J 



A S 



N 



Fig. 12. A. Monthly mean tide levels. Average at Las Piedras for 1942-49 and at Zaparita Island 

 for 1940-53. Data from Bar Survey, Maracaibo 



B. Difference in average monthly mean tide level at Las Piedras and Zaparita Island 



C. Average monthly net water balance of Lake Maracaibo. Estimated by Carter (1954) 



D. Per cent of time wind blew from N through ENE at Maracaibo, 1952. Data from 

 Bulletin Bimensureal, Servicio de Meteorologia y Communicaciones, Ministerio de la 

 Defensa , Fuerzas aereas, Maracay 



