DUTY AND MEASUREMENT OF WATER. Ill 



An Irrigation Head. The proper wetting of the 

 whole ground requires what is known as an irrigation 

 head. To irrigate ten acres with a miner's inch of water 

 needs from fifteen to thirty inches of flow at a time, de- 

 pending upon the porosity of the soil. A single inch 

 flowing constantly and used in that way would not irri- 

 gate over two acres at the best and generally not over 

 one-half an acre properly. But the flow of a single inch 

 without any reservoir to accumulate it may be used in 

 another way so as to produce fair results on from ten to 

 forty acres, according to the nature of the soil, the 

 amount of rainfall and the kind of trees for it is only 

 for trees that it can be used to advantage. It would 

 hardly pay to make trenches around grapevines on any 

 large acreage, and although some berries, vegetables and 

 other small stuff may be raised, it generally takes too 

 much work and time to water a large area of them in 

 that way. 



The farmer who sees a severe drouth broken by a 

 three hours' flow of water hardly understands that every 

 acre of his farm has received in an inch of irrigation no 

 less than 100 tons of water, or 100 acres has had 10,000 

 tons of water poured over it. The quantity of water on 

 a single acre by such irrigation will be not less than 130 

 cubic yards. A little wetting of this character places 

 more than 1000 tons in twenty-four hours on every acre, 

 or 100,000 tons on a 100-acre farm. Now an average 

 irrigation requires a five-inch layer of water over an en- 

 tire field, while some crops, oats for instance, often de- 

 mand a solid covering of ten inches. When using wind- 

 mill irrigation in a small way it may be well to roughly 

 approximate an acre of garden or orchard as requiring 

 1000 barrels of water for an ordinary wetting, but in this 

 the greatest economy is necessary and it is best to apply 

 the water by the rill or row method. The following fig- 

 ures will give an idea of the amount of water necessary 



