338 



CONSERVATION 



terests grow in value, so grows the 

 necessity for diminishing and prevent- 

 ing floods. Thus canalization bears the 

 same relation to plans for conserving 

 and controlling water circulation that 

 any concentration of civilization bears 

 to it. It increases the burden of re- 

 sponsibility for proper measures of con- 

 trol, whether in detail as applied to 

 raindrops or in gross as applied to 

 flood run-off, and the larger the wealth 

 to be protected the greater the justifica- 

 tion for large expenditures on account 

 of protection ; but more than this, for it 

 is not a question of engineering and 

 financial expense alone ; the larger the 

 national interests involved the greater 

 the individual responsibility of every 

 patriotic citizen to his local community 

 and to the commonwealth in general 

 for a proper discharge of his obligation 

 to take care of his share of the Nation's 

 assets. 



CONTROL OF GROUND STORAGE AND RUN- 

 OFF THROUGH AGRICULTURE 



On a reasonable estimate one-half of 

 the domain of the United States must 

 eventually be farmed to maintain the 

 population and prosperity of the coun- 

 try. The essential characteristics of the 

 great farming area, exclusive of irriga- 

 tion districts, is that it shall have soil and 

 sufficient rainfall. Rain falling on soil 

 is partly stored as ground water, but 

 also partly runs off. The stored water 

 is absolutely necessary to the farmer's 

 prosperity, which will increase as he in- 

 creases ground storage ; the other is 

 wasted, and if it causes erosion is de- 

 structive. 



In considering the relation of the 

 farmer's activities and the methods 

 which he can employ to increase ground 

 storage and decrease erosion we must 

 distinguish between lands that are level 

 or nearly so and lands that have a more 

 or less pronounced slope. 



Water control on plains. In regions 

 of great plains or plateaus, where lands 

 are level or nearly so, the methods 

 which may be used by the farmer to 

 increase ground-water storage are the 



methods of good tillage which at the 

 same time yield the largest crops. They 

 consist in deep plowing, proper cultiva- 

 tion during the growing season, crop 

 rotation, and the maintenance of an 

 open condition of the soil during the 

 periods of fallow. The object of these 

 methods is to increase the capacity of 

 the soil reservoirs and to open and keep 

 open the channels through which the 

 rain or melting snow has access to 

 them. Run-off and erosion are re- 

 stricted in proportion as this aim is 

 secured. 



To grow large crops takes a large 

 amount of soil moisture. The soil gets 

 it directly from rains or in seasons of 

 drought from the ground water which 

 is supplied by rains that pass down 

 through the soil to the water table. The 

 rain that soaks in is stored for the crop. 

 The rain that runs off is taken from 

 what might be stored, and is not only 

 lost water but, being muddy, is also lost 

 soil. Good tillage reduces these losses 

 by maintaining those conditions of soil 

 and subsoil under which a large pro- 

 portion of a given rainfall will be ab- 

 sorbed. 



In general, we say that an open soil 

 will absorb most water. The openness 

 of texture of a soil depends upon the 

 sizes of the particles of which it is com- 

 posed and the relative numbers of par- 

 ticles of these several sizes that is, its 

 mechanical composition. There is for 

 any kind of soil a state at which it is 

 in the loosest and best physical condi- 

 tion that is to say, a state of arrange- 

 ment of soil particles according to size 

 and spacing in which there may be the 

 largest amount of water gathered about 

 the particles as capillary films and be- 

 tween them in delicate columns. The 

 condition is one which is well known to 

 farmers as that which will yield the best 

 crops. This mechanical condition of 

 the soil is reached by plowing, harrow- 

 ing, and cultivating when the soil is 

 neither too moist nor too dry. 



The facility with which rain enters 

 a soil depends upon its being in the 

 above-described condition open, yet 



