CONDITIONS FAVORABLE AND 



UNFAVORABLE TO 



IRRIGATION. 



BY J. ULRICH. 



Irrigation, in the Rocky Mountain States, is almost wholly a- 

 matter of gravity. The stream is tapped at a point where its channel 

 is higher than the field to be watered. Thence the water is carried 

 down hill in the ditch to the highest point to be covered. In spread- 

 ing it over the field the laterals run on the ridges, and the shovel of 

 the irrigator manipulates its distribution along or across the slopes 

 below. When it has thus been brought to a level with the most 

 elevated points upon the tract to be irrigated, it can be made to flow 

 out over the laud by the force of gravity alone, without any assistance 

 from the irrigator beyond such manipulation as may be required to 

 effect its uniform distribution over the minor irregularities of surface, 

 which are eliminated as far as possible by careful leveling and 

 preparation of the ground before irrigation is attempted. 



Sometimes the water supply lies at a lower level than the land to 

 be irrigated, and has to be raised. This occurs where the water 

 supply comes from wells or other subterranean sources. In such 

 cases it is raised to the required elevation by pumping, or by any 

 other method which is found most convenient and economical. 

 Pumping water for irrigation, because of the large volume required, 

 is attended with great expense and can not usually be employed with 

 profit except for the reclamation of land devoted to the cultivation of 

 crops which represent great value per unit of area devoted to their 

 production. In the cultivation of oranges, lemons, and other fruits 

 which yield a product whose value is several hundred dollars per 

 acre, and where the amount of water required is relatively small, 

 pumping may be resorted to with profit; but in the growing of cereals 

 and the ordinary farm products of the temperate regions, the cost of 

 the pumping plant and its operation is often prohibitory. 



In most cases, however (in all where irrigation is conducted upon 

 an extensive scale), the water supply is obtained from running 

 streams, which in the arid region generally have very high gradients, 

 thus rendering their diversion upon the adjoining lands compara- 

 tively easy. Where the land to be irrigated lies along the immediate 

 border of the stream and is but little elevated above the latter a dam. 



