118 THE IRRIGATION AGE. 



of quadrants, and the pumps be close enough to the embankment to- 

 discharge water into the reservoir through short flumes or pipes. 



How much water, in addition to the rainfall, has not yet been 

 fully determined for any kind of crops.. Taking the generally ac- 

 cepted amount of 24 inches of rainfall as the necessary amount of wa- 

 ter to mature a crop, it is only necessary to deduct the average annual 

 rainfall frow 24 and the difference will be the amount to be supplied- 



When the rainfall during the year equals 12 inches, then the 12 

 inches more must be supplied, and where the rainfall is 18 inches the 

 remaining amount to be supplied is 6 inches and so on. One acre of 

 ground requires about 27,000 gallons of water to cover it over one inch 

 deep, and this amount multiplied by the number of inches necessary 

 to add to the rain fall so as to make up the required 24 inches, will 

 give the number of gallons per acre of water to be pumped, but due 

 allowance must be made for leakage through the bottom and walls of 

 reservoir; leakage and loss in ditches and evaporation, all of which 

 amounts to a great deal in the aggregate. 250,000 to 325,000 gallons 

 of water will probably mature one acre of any crops when the average 

 rainfall is 12 inches or more. K pump with six inch cylinder will sup- 

 ply 1000 to 2000 gallons per hour when the wind velocity is 15 to 30 

 miles per hour and will probably supply water to irrigate 5 to 10 

 acres. A pump with 8 inch cylinder will supply 1800 to 3600 gallons 

 ppr hour, wind 15 to 30 mile velocity, and will supply water to irrigate 

 20 to 40 acres of spring crops. When general crops are grown, so that 

 the pump may work the year around, twice the amount of land can be 

 irrigated. Smaller mills can operate pumps in shallow wells, while it 

 will require mills of larger sizes to operate the pumps as the depth of 

 well increases and the same mill will operate more than one pump, as 

 the force of wind increases from 15 to 30 or 35 mile velocity, and the 

 added pumps reinforcing the first one, increases the amount of water 

 pumped so that a great deal more land can be irrigated than where 

 only one pump is employed. Water supply and how to obtain it. is a 

 problem but little understood. Open wells and well points are con- 

 tending for preference. 



Where the water is found in sand stratas of 12 feet or more in 

 thickness, the drive well points have given best satisfaction. It is be- 

 lieved that even where the water is found in sand stratas four or five 

 feet ihick that the water will flow into the pump faster through sand 

 points than through curbing into an open well and then from the 

 open well into the pump. 



Much money and labor has been expended in the Arkansas Valley 

 where the sand stratas in which the water is found, lies near the sur- 

 face to make open wells thai would supply sufficient water for large 

 pumps, and while all attempts can not truthfully be said to have re- 



