54 THE FUTURE OF ARID LANDS 
place calls for geological knowledge and properly the use of 
geologists to make the survey with or without the aid of geo- 
physics. By this means exact records would be kept of all the 
wells or bores put down, the strata through which they went 
down, the quality and quantity of the water, and so on. Such a 
survey would enable estimates to be made of the total volume of 
the underground supply, of its area and depth in a confined source, 
or of its flow if unconfined, and the region of flow in the aquifer. 
It may be of interest to remind you that below the Nile there is 
an underground river about 560 miles long reaching from about 
80 miles south of Luxor to about 70 miles north of Cairo. Accord- 
ing to Mohamed El Sayed Ayoub, one-time Inspector General 
for Nile Control, the mean width of the stream is 10 kilometers, 
the strata of sand and gravel in which it flows ranges from 100 
meters to 300 meters in depth, with a water storage capacity of 
nearly 500,000 million cubic meters, and the water takes nearly 
100 years to arrive at the head of the delta. Each year 1,400 mil- 
lion cubic meters are used for irrigation, another 1,000 million 
cubic meters are planned to be used on 25,000 acres of a new irri- 
gation project, about another 1,000 million cubic meters are used 
by plants, and nearly 4,000 million cubic meters flow into the delta 
unused. 
This great aquifer under the Nile and the Nile itself receive 
their water from distant sources, but were they to rely on local 
rainfall for the infiltration and stream flow they would be dry 
each year for six months. 
The Thal Development Authority 
I would like at this stage to tell you briefly the story of another 
great arid area which is being reclaimed, the reclamation of which 
illustrates regional organization of the order of the Tennessee 
Valley Authority. I refer to the Thal desert area in western 
Pakistan. It consists of a triangular area of nearly five million 
acres with a base of 65 miles along the Salt Range to the north, 
and a length of about 175 miles to the apex at the-south, and is 
in the Punjab between the Indus, Jhelum, and the Chenab. 
Tradition, supported by geological evidence, has it that the Indus 
