230 



FARM DEVELOPMENT 



Figure 143, are transformed into arable land. Here the 

 same pump serves for both drainage and irrigation. 

 This is a small illustration of how drainage is carried 

 out on a large scale in districts with lands subject to 

 flooding from ocean, lake or river; and it serves also to 

 show how irrigation may be economically arranged on 

 some lands in countries subject to an occasional drouth. 

 In some cases, co-operative associations are able to 

 undertake the construction of these dikes ; in other cases, 



the county, 



state, or even 

 the nation^ 

 must co-oper- 

 ate in their con- 

 struction and 

 maintenance. 

 Where diking 



Figure 135. S, roadway and embankment between low area 

 and stream which discharges into the lake; E, pumping engine; * 



T, pit into which drains discharge and from which the water /** -o 11 TT 



is pumped; W, water discharging into the lake; N, open ditch are generally 



flowing into the pit; X, embankment beside the lake. , 



some supple- 



mentary arrangements necessary for taking care of the 

 water from the rainfall, and also of the flood water from 

 drainage areas in a direction opposite to that from 

 which the main flood water is held back by dikes. In 

 some cases, water can be drained off in open ditches 

 nearly parallel to the line of the dike, and follow the river 

 to a lower level. In other cases, as along lakes and by 

 coast waters, there is no opportunity for carrying off 

 this surface and flood water, except by elevating it to the 

 other side of the dike by means of machinery operated 

 by wind, steam or other cheap power. The engineering 

 problems of diking and drainage to elevating stations, 

 while representing large interests, do not present un- 

 usual difficulties. As a rule, the most difficult problem 

 is to determine the relation between cost and benefit, 

 though in many cases in America, as well as in other 



