30 



BULLETIN 462, V, S. DEPARTMENT OF AGRICULTURE. 



The size of main needed depends on the number of laterals it is 

 required to operate at once, or, in other words, the acreage that is to 

 be watered at one time. 



Table 2 gives sizes of mains needed for different quantities of 

 water, according to the acreage to be watered. The data in this table 

 are of a general nature and may be modified to suit the specific condi- 

 tions. By following the sizes of the pipe as indicated below there 

 will be ample capacity for the successful operation of the system 

 under all conditions encountered. 



Table 2. — Size of pipe for main supply line. 



Discharge in gallons per 



Length of line in feet. 



minute. 



50 



100 



200 



300 400 



500 



600 



700 



30 



Inches. 



2 



24 

 2* 

 3 

 34 



4 

 4 



Inches. 

 2 

 2} 

 2-1 

 3" 

 34 

 34 

 4 



Inches. 

 2 



24 

 3 

 3 

 34 



4 

 4 

 5 



Inches. 

 2 

 24 

 3 

 34 



4 

 4 

 5 

 5 



Inches. 

 24 

 3 

 3 



34 

 \ 

 4 

 5 

 6 



Inches. 

 24 

 3 



34 

 34 

 4 

 4 

 5 

 6 



Inches. 



24 

 3 



34 



4 



4 



5 



5 



6 



Inches. 

 2 4 



75 



3 



100 



34 



150 



4 



200 : 



4 



300 ~. 





400 



6 



500 



6 







The above system is in operation on about 150 acres within a few 

 miles of Williston, in the north-central part of the State. The plants 

 are mostly small, usually irrigating not more than 10 acres, one plant 

 which irrigates 55 acres being an exception. The water supply for 

 this plant is obtained from a bored well about 100 feet in depth, and 

 is pumped from the well into the main by a steam duplex pump with 

 rated capacity of 700 gallons per minute, operated by a 70-horsepower 

 steam engine. The plant is designed to irrigate about 20 acres at 

 one time, which requires a 7-inch main at the start. This is reduced 

 to a 5-inch main at the end of the field, and might be reduced still 

 more but for the fact that this pipe supplies water also to about 60 

 acres of surface-irrigated land. Much of the pipe is second-hand, and 

 there is no record of its cost, but it is estimated that to replace it 

 with new galvanized pipe would cost about $100 per acre for the field 

 laterals and an additional $150 per acre for the pump, engine, and the 

 main. This would mean a total cost of $250 per acre, or approxi- 

 mately $13,750 for the system, complete. The owner burns wood, 

 which is plentiful in this section. He estimates that with wood 

 he can operate his plant for 24 hours, the wood costing only $1.25 

 per cord. This is exceedingly low for operating expenses. The 

 plant is run day and night continuously when it is in operation 

 at all, owing to the difficulty of getting up steam every day; also be- 

 cause irrigation at night is found to have a number of advantages, 

 such as smaller loss by evaporation and prevention of scald. 



