34 BULLETIN 304, U. 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 haying 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 preyent flooding could be approximated. In cases where especially 
valuable crops were to be raised it might well pay to proyide for storms 
that occur only once in 10 years. 
While run-off data on pumping districts in this section were not 
extensiye enough to draw any yery definite conclusions, the majority 
of the districts haye a capacity of plant sufficient to remove a depth 
of 0.25 inch in 24 hours. On most of the districts this capacity has 
giyen satisfaction. 
LOCATION OF 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. Howeyer, 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 
