56 BULLETIN 304, U. S. DEPARTMENT OF AGRICULTURE. 
by profiting by the experience of the districts already under drainage, 
the new districts will undoubtedly save much money and secure more 
satisfactory drainage improvements. The best way for one unfa- 
miliar with this kind of drainage to become informed on the subject 
is to visit and inspect thoroughly a number of the completed districts. 
Tables 20 and 21 give lists of such districts, with information as to 
location, size, etc. 
SUMMARY. 
Numerous tracts in units of from 5,000 to 20,000 acres have been 
reclaimed along the Illinois River and on both sides of the Mississippi 
in the States of Illinois, Iowa, and Missouri. In the average district 
the cost of the general drainage improvements, including levees, 
ditches, and pumping plant, has been about $30 per acre. This 
method of reclamation may be expected to be extended constantly 
to new localities as agricultural land becomes more valuable. 
The design and construction of the levees, ditches, and pumping 
plant require a considerable degree of engineering ability. Poor de- 
sign may result either in a system so inadequate for its purposes as 
to render the benefit to the land insufficient to make the undertaking 
profitable, or it may lead to an expenditure for construction greatly 
in excess of the amount that could have been made to suffice. In 
general, the inexperienced tend to underestimate greally the extent 
and expense of the work required in such reclamation. 
The levees must originally be made of such height and thickness 
as to afford ample strength and they must also be given careful sub- 
sequent attention to secure proper maintenance. The internal drain- 
age ditches should be deep enough to keep the ground- water level at 
least 3 feet below the surface and their capacity should be sufficient 
to discharge heavy rains freely to the pumping station. Streams 
entering the district from higher ground should be diverted around 
the levees where such a plan is feasible, and provision should be made 
in such diversion ditches for the collection and storage of silt from 
hill streams. 
The pumping plant should have a capacity sufficient to remove as 
a minimum amount in 24 hours a quantity of water sufficient to 
cover the entire district to a depth of 0.3 inch. The capacity should 
be greater in situations of heavy rainfall and where the run-off of 
rolling land is received in the district. 
The pumping machinery should be so arranged as to reduce to a 
minimum the work of disposing of the surplus water, and it should 
be chosen with especial regard to economy and efficiency in opera- 
tion. Where large fluctuations in the river level are to be expected 
the machinery must be sufficiently large to operate at the maximum 
