IRRIGATION. 



37 



This is hiokcii through with a few strokes of the pick, and if the water 

 ascends with considerable force, as is sometimes the case, the well 

 dig-ger runs considerable risk of being drowned. In the more accessi- 

 l)le parts of the Sahara, modern well-boring machinei-y has largel}^ 

 replaced the ancient method. 



The natives are very jealous of the water that is obtained with so 

 nmch difficulty, and numerous quarrels arise over its distribution. 

 In the Zibans oases, where a system of canals exists, the water is con- 

 trolled by an association which decides in what <[uantity and upon 

 what days it shall be allotted to each person. It is measured by lay- 

 ing the trunk of a date palm across the top of an earthen dam in the 

 canal. Notches, corresponding to the width of the hand with the 

 thumb closed, are cut into this trunk at intervals. The amount which 

 passes each of these notches represents one share of water. 



In the Oued Rirh region, since the French occupation, a great many 

 artesian wells have been bored, under the direction of M. Jus, who 

 became famous through his connection with this work. The first was 

 sunk in 1856. In 1898 there were 120 metal-cased artesian wells from 

 160 to 330 feet deep, in addition to .500 wells dug by natives. The 

 total discharge of all these wells was about UO cubic feet per second, 

 yet so far the water supply has sufl'ered no perceptible diminution. 

 With the water thus obtained the area in date palms has been greatly 

 extended during the past thirty years. It is estimated that during 

 the last three decades the population of the Oued Rirh has doubled, 

 and the wealth of the region has been increased tenfold. There are 

 probably few other parts of the Sahara where such development is 



possible. 



Unlike the irrigating water of the coast region, that used in the 

 desert region generally carries a high percentage of salts in solution. 

 In fact, the water with which various crops are grown in the Algei'ian 

 Sahara appears to be saltier than that used for this purpose anywhere 

 else in the world. So far as is known, 500 parts of salts per 100,000 

 parts of water is the maximum concentration of water which is used 

 with success in the United States, and, under ordinary circumstances, 

 300 parts is the limit for successful crop production. In the Sahara, 

 however, water containing as much as 800 parts of salts {half of the 

 total amount being sodium chlorid) per 100,000 parts of water is 

 applied to soils that are themselves highly saline. A variety of culti- 

 vated plants —various fruit trees, garden vegetables, and alfalfa- 

 thrive under these conditions. 



It seems a fair inference that the maxinumi amount of soluble matter 

 which can safely be allowed in irrigation water has been under- 

 estimated by American writers. Where the soil is light and under- 

 drainage is provided for, as is the case in the Algerian oases, it is 



