336 MAN'S USE AND CONSERVATION OF SOILS 



Reclamation of Arid Lands and Low Lands. Four 

 thousand years ago the Assyrians made a veritable garden 

 of the Tigris and Euphrates valleys by dredging lakes for 

 the conservation of river flood waters and canals for distri- 

 bution. Tanks, reservoirs, and irrigation canals were in exist- 

 ence in India centuries before Christ. There are evidences 



EAST END OF THE ASSUAN DAM ACROSS THE NILE 

 The greatest irrigation dam in the world. 



that a prehistoric race had extensive irrigation works cen- 

 turies ago in New Mexico and Arizona. 



Modern methods of irrigation make it possible to reclaim 

 large tracts of land that must have remained waste lands in 

 ancient days. The building of great dams, the construc- 

 tion of permanent ditches, and even the boring of water 

 courses through the sides of great mountains, are among 

 the great tasks performed by the United States Govern- 

 ment and by private companies in reclaiming large areas 

 of land in arid sections of the West. 



