AMOUNT OF WATER NECESSARY. 45 



M. Holland, Avho has written a very complete account of the water 

 supply of the Algerian Sahara," and who is himself one of the mem- 

 bers of a firm which has created extensive date plantations in the Oued 

 Rirh country, in the Algerian Sahara, considers that one-half liter 

 (0.53 quart) per minute should be allowed to each palm to secure, the 

 best results. 



M. le commandant Rose, himself an experienced planter, has pub- 

 lished a most detailed statement 6 regarding the practice of irriga- 

 tion in the Oued Rirh country, where the water supply is furnished 

 by artesian wells. He recommends 24 irrigations of 3 cubic meters 

 (7i>2.r> gallons) each, making 72 cubic meters, or 19,021 gallons during 

 the year. During the hot season, from June to September, inclusive, 

 weekly irrigations are practiced, 17 in all, consuming 51 cubic meters, 

 or 13,473 gallons per tree, which is at the rate of about 113 gallons 

 per day, or about 0.314 quart (0.3 liter) per minute, the lowest of the 

 three estimates. During the autumn and winter 2 irrigations, and 

 during spring 5 irrigations, are prescribed. 



When the supply of water is invariable, as for example the flow 

 from an artesian well, it is necessary to plant only the number of 

 palms that can be properly irrigated by the available water supply 

 during the hot season, when the amount needed is greatest. Where 

 irrigation is practiced by means of water conducted from rivers or 

 from storage reservoirs in canals, as is the case in most of the arid 

 regions of the Southwest, it will be even more necessary to determine 

 carefully how much water can be had in summer to avoid planting 

 more dates than can be properly irrigated. 



In the plantations made recently by French proprietors in the Alge- 

 rian Sahara, the date palms are usually set out 8 meters, or 26 feet, 

 apart, making 143 to the hectare, or 60 to the acre. Some of the 

 planters consider this distance too small and plant about 10 meters (33 

 feet) apart, making about 40 to the acre, while others, among them the 

 celebrated civil engineer Rolland, consider 200 to the hectare, or about 

 80 to the acre, as being the best number to plant. 



Taking 60 to the acre, 26f feet apart, as a good number to plant, the 

 amount of water needed per acre can easily be calculated. Using 

 Rose's estimate of 19,021 gallons per tree per annum, 3 acre-feet of 

 water would be required, of which 2-f acre-feet would be used during 

 the four summer months from June to September, inclusive. Using 

 Jus's estimate, which puts the least amount necessary at one-third 



Rolland, Georges. Hydrologie du Sahara algerien (chemin de fer transsaharien ) , 

 Paris, Imprimerie Rationale, 1894, p. 9. 



& "La culture du dattier dans le sud constantinois, par un homme du sud." Alger. 

 1898, Pierre Fontana & Cie, Paris, Augustin Challamel. 8. 20 pp. The identity 

 of the author of this pamphlet was disclosed by Eolland (Hydrologie du Sahara 

 algerien, p. 167). 



