114 FARM MECHANICS 



diseases. Where water is abundant within easy reach, 

 pumping irrigation water is thoroughly practical. 

 Improvements in pumps in recent years have increased 

 their capacity and insured much greater reliability. 

 A centrifugal pump is recommended for depths down 

 to 75 feet ; beyond this depth the necessity of installing 

 more expensive machinery places the business of pump- 

 ing for irrigation on a different plane. A centrifugal 

 pump will throw more water with less machinery than 

 any other device, but like all other mechanical inven- 

 tions, it has its limitations. In figuring economical 

 pumping, the minimum quantity should be at least 100 

 gallons per minute, because time is an object, and irri- 

 gation, if done at all, should cover an area sufficient to 

 bring substantial returns. Centrifugal pumps should 

 be placed near the surface of the water in the well. 

 For this reason, a large, dry well is dug down to 

 the level of the water-table and the pump is solidly 

 bolted to a concrete foundation built on the bottom of 

 this well. A supply pipe may be extended any depth 

 below the pump, but the standing water surface in the 

 well should reach within a few feet of the pump. The 

 pump and supply must be so well balanced against 

 each other that the pull-down from pumping will not 

 lower the water-level in the well more than twenty feet 

 below the pump. The nearer the ground water is to 

 the pump the better. 



The water well below the pump may be bored, or a 

 perforated well pipe may be driven; or several well 

 points may be connected. The kind of well must de- 

 pend upon the condition of the earth and the nature 

 of the water supply. Driven wells are more successful 

 when water is found in a stratum of coarse gravel. 



