270 



THE IRRIGATION AGE. 



Suggestions for the Construction of Small Pumping Plants 



for Irrigation. 



KIND OF WELLS ADAPTED FOE SECURING WATER FROM GRAVELS. 



BY F. H. NEWELL, Chief Engineer, U. S. Reclamation Bureau. 



The most economical well for securing water in the 

 quantities needed for irrigation is a well from twelve 

 to fifteen inches in diameter, extending into the water- 

 bearing gravels thirty to sixty feet, according to the 

 thickness of the gravels at the place where the well is 

 drilled. Strainers for these wells can be made of slotted 

 galvanized iron. The perforated metal should be placed 

 opposite all the coarse gravels, or at a depth of ten 

 feet below the surface of the water. These strainers 

 can be made by any mechanic by punching one-eighth 

 by 1-inch slots into heavy galvanized iron and then rivet- 

 ing the sheets into cylinders of the proper diameter. 

 The cylinders should be rolled in such a way that the 

 burr made by punching the slots will come on the 

 outside of ,the finished casing, and so that the slots will 

 be vertical. A much better strainer can be made by pur- 

 chasing the metal in sheets already perforated. For 

 this purpose steel sheets 48 by 120 inches in dimensions, 

 perforated with hit and miss slots, three-sixteenths by 

 one-inch, and galvanized after the perforations are made, 

 will make ideal strainers. When rolled into cylinders 

 these sheets form a casing about fifteen inches in diam- 



Fig. 1. Well strainers, made of slotted galvanized iron. These 

 strainers are 15 inches in diameter and 10 feet long, provided with 

 AxlJ4-inch hit and miss slots, punched before the steel is galvanized. 

 The strainers shown in the diagram were made of No. 18 wire gauge 

 sheet steel. 



eter. In constructing the well the perforated sections 

 should be put in place, one above another, to within 

 about ten feet of the water level; from this depth up- 

 ward the casing should not be perforated. 



AMOUNT OF WATER THAT CAN BE OBTAINED FROM THE 

 WELLS. 



Wells constructed as above, in gravels similar to 

 those in the South Platte and Arkansas valleys, will 

 furnish at least one-fourth gallon of water per minute 

 for each square foot of strainer surface in the well, 

 when the water in the well is lowered one foot by 

 pumping. If the water in the well is lowered ten feet 

 by pumping the amount of water recovered should 

 amount to at least ten times as much, or two and one- 

 half gallons per minute per square foot of strainer. 

 If a fifteen-inch well is drilled in good water bearing 

 gravel to a depth of forty feet, the lower thirty feet of 

 which is strainer surface, and if the pump lowers the 

 water in the well ten feet, the amount of water sup- 

 plied by the well should amount to at least 300 gallons 

 per minute. A careful test of the waterworks at North 

 Platte, Neb., showed that the strainers in the wells 

 were furnishing three-tenths gallon of water per minute 

 per square foot of strainer surface, when the water 

 in the wells was lowered one foot by pumping. The 

 average of eleven pumping plants in the Arkansas val- 

 ley was 0.33 gallon of water per minute for each square 

 foot of strainer surface, under one foot head. 



For small pumping plants a single well of the 

 depth indicated above would probably be sufficient, but 

 if good water bearing gravels do not extend to the 

 requisite depth, it would be necessary to increase the 

 number of wells and connect several of them to the 

 pump. 



DISTANCE BETWEEN WELLS. 



If it is necessary to construct several wells in order 

 to secure the amount of water required for an irriga- 

 tion plant, it becomes important to consider the best 

 and most economical arrangement of the wells. Two 

 different methods will be found available for this pur- 

 pose. If the amount of water required is not greatly 

 in excess of that which can be supplied by a single 

 tubular well, it is often found practicable to construct 

 a large dug well, six to ten feet in diameter, to a depth 

 of five to ten feet below the water level, inserting in the 

 bottom of the dug well several feeders of perforated 

 galvanized iron, as described above. This method has 

 the advantage of permitting the pump that is to recover 

 the water to be submerged in the water of the well. A 

 well of this sort is shown in Fig. 2. 



In order to sink a dug well the proper distance ber 

 low the water level it is necessary to construct a wooden, 

 brick, or concrete crib that will sink as the material 

 is removed from its interior. The crib of the well 

 shown in Fig. 2 is made of wood, and is made larger at 

 the lower than at the upper end to facilitate sinking. 



Another method of recovering a large quantity of 

 water is to sink a battery of wells and connect them by 



