242 FIRST YEAR COURSE IN GENERAL SCIENCE 



of water constant on that side. On the other side is the 

 desert. 



262. Irrigation. There are thousands of square miles of 

 land in the United States, as well as elsewhere, which have 

 long been considered worthless and have been both impass- 

 able and uncultivated because of desert conditions. It has 

 always been known that the land bordering a stream is more 

 fertile than similar areas at a distance from the stream. 

 By diverting a part of the water of streams into a system 

 of canals and ditches, a much larger area can be artificially 

 watered. This method of supplying water is called irriga- 

 tion. By its practice, in the last fifty years much of the 

 desert in this country has been reclaimed for cultivation. 



The United States Reclamation Service and some private 

 enterprises are conducting extensive systems of irrigation in 

 the region between the Rocky Mountains and the Sierra 

 Nevadas. They have secured possession of, or the right to 

 take water from, streams whose headwaters are at a con- 

 siderable elevation above the lands to be irrigated. In 

 some places reservoirs are built to accumulate water during 

 the spring, the time of freshets and melting snows. The 

 water passes by gravity from the reservoirs, or streams, 

 through canals and ditches and sometimes by tunnels 

 through mountains, to the arid region. At intervals, gates 

 are provided by which water can be let out into a canal 

 on a lower level. From this canal, water flows through 

 parallel trenches all over a great farm. 



Many sections of eastern Colorado, Utah, New Mexico, 

 Arizona, and southern California are now producing mel- 

 ons, peaches, oranges, and lemons, as well as sugar beets 

 and all kinds of garden produce. A few years ago these 

 regions bore only sage brush and cactus and were the homes 

 of the prairie dog, the scorpion, and the coyote. 



