216 THE FUTURE OF ARID LANDS 
Figure 12. Fern-shaded spring on the flanks of the Araripe tableland 
near Crato, Ceara. 
extends along the foot of the sedimentary scarp and 1s sustained 
by a number of small streams which have nicked and notched the 
steep inface and tap the westward dipping aquifers (Figure 11). 
The Chapada do Araripe, the main tabular remnant east of the 
Ibiapaba, reaches an average altitude of around g60 meters 
(3,150 feet) and acts as an immense underground storage reservoir. 
Watered by more than 150 springs (Figure 12), a green belt 
several miles broad extends along the foot of the tableland in 
southern Ceara and suggests a veritable oasis to the traveler 
approaching through the dry caatinga. Here, where an intensive 
use of the soil is possible, a quarter-million people are concen- 
trated. Productivity and value of the land are in direct proportion 
to the possibility of it being irrigated. Access to water determines, 
for example, just how many hectares of cane an operator can 
cultivate. 
Becausethe techniques employed in the utilization of the water 
issuing from the sandstone beds of the Ibiapaba and Araripe 
uplands leave much to be desired, there is unfortunately a con- 
siderable wastage of water. It has been estimated that losses in 
the open /evadas (irrigation ditches) at the foot of the Araripe 
