34 BULLETIN 304, IT. S. DEPARTMENT OF AGRICULTURE. 



capacity of about 0.30 inch per 24 hours would be satisfactory on 

 most districts. Districts of less than 5,000 acres might better increase 

 this somewhat, while it is possible that districts having more than 

 15,000 acres could decrease this capacity with safety. By applying 

 a similar process to any other storm intensity, the necessary capacity 

 to prevent flooding could be approximated. In cases where especially 

 valuable crops were to be raised it might well pay to provide for storms 

 that occur only once in 10 years. 



While run-off data on pumping districts in this section were not 

 extensive enough to draw any very definite conclusions, the majority 

 of the districts have a capacity of plant sufficient to remove a depth 

 of 0.25 inch in 24 hours. On most of the districts this capacity has 

 given satisfaction. 



LOCATION OP PUMPING PLANT. 



In general the pumping plant should be so located that the drain- 

 age water may be brought to it with the least expenditure for interior 

 ditches. However, a more expensive ditch system will often permit 

 the combination of several small districts into one large one, thus 

 reducing very materially the charge for pumping-plant construction 

 and operation. The expenditures should be adjusted so that the 

 annual charge for interest on investment, depreciation, and opera- 

 tion of pumping plant will be a minimum. Where convenient, there 

 is some apparent advantage in locating the plant on a suitable arm 

 of the river rather than on the main river channel. The location 

 should be so chosen as to be most easily accessible for the delivery 

 of fuel and for convenience of attendance. Thus, in the Pekin-La 

 Marsh District the pumping plant is situated at the upper end of the 

 district, so as to be close to the town of Pekin. 



TYPES OF PUMPING MACHINERY. 



Since pumps are to be depended upon to remove promptly surplus 

 water whose presence may endanger a whole crop, it is of the utmost 

 importance that the pumping plant be able to work with certainty 

 and reliability whenever needed. 



The annual cost of a pumping plant is made up of three main items : 

 (1) The charge for interest on the original cost of the plant and for 

 depreciation; (2) the cost of fuel, or electricity if motors are used; 

 and (3) the cost of labor. Certain general principles concerning the 

 mutual relations of these different items must be understood before 

 taking up the comparison of the different types of machinery avail- 

 able for pumping. 



The interest upon the original cost of the plant goes on every year 

 whether the plant is operated much or little. Depreciation also takes 

 place whether the plant is operated or not, and for such installations 



